[pim] WGLC feedback for draft-ietf-pim-3376bis (was: Re: pim wglc for 3228bis, 3376bis and 3810bis)
Toerless Eckert <tte@cs.fau.de> Thu, 14 December 2023 21:27 UTC
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Date: Thu, 14 Dec 2023 22:27:27 +0100
From: Toerless Eckert <tte@cs.fau.de>
To: Stig Venaas <stig@venaas.com>, draft-ietf-pim-3376bis@ietf.org
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Subject: [pim] WGLC feedback for draft-ietf-pim-3376bis (was: Re: pim wglc for 3228bis, 3376bis and 3810bis)
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Dear Brian, Thanks a lot for all this meticulous work! I've just sent another related email to one set of possible change requests i didn't want to propose without other peoples feedback (changing automatic fallback for older router presence). The following feedback is marked question/nit/minor/myor/comment. It is also numbered for easier referencing if necessary later. 1.question: I am not sure what the current BCP is wrt. to authorship of a bis that maintains most of the original text. Was this discussed and concluded that there was evidence/opinion that it is BCP to remove all the original authors ? Just wondering. I do understand it could be painful to go through the IETF review/AUTH48 process if any of the prior author is listed and is unresponsive. 2.minor: Should we not have a way for operators to determine which revision of IGMP version 3 an implementation claims to be conformant to ? Something like: Implementations of IGMP version 3 that are conforming to this specification (as opposed to [RFC3376]) SHOULD have an operator interface indication for this (such as a CLI show command or a YANG element). Rest of review in inline into idnits formatted draft: idnits 2.17.1 Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- -- The draft header indicates that this document updates RFC2236, but the abstract doesn't seem to mention this, which it should. 3.comment: see suggested fix below. Miscellaneous warnings: ---------------------------------------------------------------------------- == The document seems to lack the recommended RFC 2119 boilerplate, even if it appears to use RFC 2119 keywords. (The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). (Using the creation date from RFC2236, updated by this document, for RFC5378 checks: 1995-08-28) -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) 4.comment: see suggested fix below Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Looks like a reference, but probably isn't: '1' on line 691 -- Looks like a reference, but probably isn't: '2' on line 693 == Missing Reference: 'N' is mentioned on line 699, but not defined == Missing Reference: 'M' is mentioned on line 677, but not defined ** Obsolete normative reference: RFC 2402 (Obsoleted by RFC 4302, RFC 4305) 5.comment: I haven't tried to validate/falsify the above. Pretty sure you can to or did this yourself. -------------------------------------------------------------------------------- 2 Network Working Group B. Haberman, Ed. 3 Internet-Draft JHU APL 4 Obsoletes: 3376 (if approved) 9 November 2023 5 Updates: 2236 (if approved) 5. comment: rfc-index.txt says: Generally, only immediately succeeding and/or preceding RFCs are indicated, not the entire history of each related earlier or later RFC in a related series Given how rfc3376 already updates rfc2236, this text would suggest we do not include "updates: 2236", but given how we obsolete 3376, it seems we do must include "updates 2236", so this seems to be correct. Just commenting here because it took me a while to get to this conclusion, and RFC editor might ask later too. 6.minor: I think we need to add "Updates: RFC4604". See discussion after line 192. 6 Intended status: Standards Track 7 Expires: 12 May 2024 9 Internet Group Management Protocol, Version 3 10 draft-ietf-pim-3376bis-08 12 Abstract 14 This document specifies a revised Version 3 of the Internet Group 15 Management Protocol, IGMPv3. IGMP is the protocol used by IPv4 7.nit: I think this reads more correct if you s/IGMPv3/IGMP/. Because right now it read like "third version of IGMPv3". Or alternatively some different sentence structure: This document revises Version 3 of the Internet Group Management Protocol (IGMPv3), RFC3376, but maintains full interoperability with existing IGMPv3 deployments. However you want to do it, i think the interoperability statement would be nice for reconfirmation to the reader even though keeping the version number might be a sufficient indicator for the more enlightened process fetishist. 16 systems to report their IP multicast group memberships to neighboring 17 multicast routers. Version 3 of IGMP adds support for source 18 filtering, that is, the ability for a system to report interest in 19 receiving packets only from specific source addresses, or from all 20 but specific source addresses, sent to a particular multicast 21 address. That information may be used by multicast routing protocols 22 to avoid delivering multicast packets from specific sources to 23 networks where there are no interested receivers. 8.nit: Nice explanations. I would love to see a sentence like the following added to the end.: but fully optional. It also enables support of Source Specific Multicast (SSM). 25 This document obsoletes RFC 3376. 9.nit: This document obsoletes RFC3376 and updates RFC2276. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at https://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on 12 May 2024. 44 Copyright Notice 46 Copyright (c) 2023 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 51 license-info) in effect on the date of publication of this document. 52 Please review these documents carefully, as they describe your rights 53 and restrictions with respect to this document. Code Components 54 extracted from this document must include Revised BSD License text as 55 described in Section 4.e of the Trust Legal Provisions and are 56 provided without warranty as described in the Revised BSD License. 10.nit: idnits reminded us that we need to insert the appropriate disclaimer here because rfc3376 is before 2008: This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. In XML: <rfc category="std" docName="draft-ietf-pim-3376bis-08" ipr="pre5378Trust200902" updates="2236" obsoletes="3376"> ^^^^^^^^^^^^^^^^^^ 58 Table of Contents 60 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 61 2. The Service Interface for Requesting IP Multicast 62 Reception . . . . . . . . . . . . . . . . . . . . . . . . 5 63 3. Multicast Reception State Maintained by Systems . . . . . . . 6 64 3.1. Socket State . . . . . . . . . . . . . . . . . . . . . . 6 65 3.2. Interface State . . . . . . . . . . . . . . . . . . . . . 7 66 4. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 9 67 4.1. Membership Query Message . . . . . . . . . . . . . . . . 10 68 4.1.1. Max Resp Code . . . . . . . . . . . . . . . . . . . . 11 69 4.1.2. Checksum . . . . . . . . . . . . . . . . . . . . . . 12 70 4.1.3. Group Address . . . . . . . . . . . . . . . . . . . . 12 71 4.1.4. Flags . . . . . . . . . . . . . . . . . . . . . . . . 12 72 4.1.5. S Flag (Suppress Router-Side Processing) . . . . . . 12 73 4.1.6. QRV (Querier's Robustness Variable) . . . . . . . . . 12 74 4.1.7. QQIC (Querier's Query Interval Code) . . . . . . . . 12 75 4.1.8. Number of Sources (N) . . . . . . . . . . . . . . . . 13 76 4.1.9. Source Address [i] . . . . . . . . . . . . . . . . . 13 77 4.1.10. Additional Data . . . . . . . . . . . . . . . . . . . 13 78 4.1.11. Query Variants . . . . . . . . . . . . . . . . . . . 14 79 4.1.12. IP Destination Addresses for Queries . . . . . . . . 14 80 4.2. Version 3 Membership Report Message . . . . . . . . . . . 14 81 4.2.1. Reserved . . . . . . . . . . . . . . . . . . . . . . 16 82 4.2.2. Checksum . . . . . . . . . . . . . . . . . . . . . . 16 83 4.2.3. Flags . . . . . . . . . . . . . . . . . . . . . . . . 16 84 4.2.4. Number of Group Records (M) . . . . . . . . . . . . . 16 85 4.2.5. Group Record . . . . . . . . . . . . . . . . . . . . 17 86 4.2.6. Record Type . . . . . . . . . . . . . . . . . . . . . 17 87 4.2.7. Aux Data Len . . . . . . . . . . . . . . . . . . . . 17 88 4.2.8. Number of Sources (N) . . . . . . . . . . . . . . . . 17 89 4.2.9. Multicast Address . . . . . . . . . . . . . . . . . . 17 90 4.2.10. Source Address [i] . . . . . . . . . . . . . . . . . 17 91 4.2.11. Auxiliary Data . . . . . . . . . . . . . . . . . . . 17 92 4.2.12. Additional Data . . . . . . . . . . . . . . . . . . . 18 93 4.2.13. Group Record Types . . . . . . . . . . . . . . . . . 18 94 4.2.14. IP Source Addresses for Reports . . . . . . . . . . . 20 95 4.2.15. IP Destination Addresses for Reports . . . . . . . . 20 96 4.2.16. Notation for Group Records . . . . . . . . . . . . . 20 97 4.2.17. Membership Report Size . . . . . . . . . . . . . . . 21 98 5. Description of the Protocol for Group Members . . . . . . . . 21 99 5.1. Action on Change of Interface State . . . . . . . . . . . 22 100 5.2. Action on Reception of a Query . . . . . . . . . . . . . 25 101 6. Description of the Protocol for Multicast Routers . . . . . . 27 102 6.1. Conditions for IGMP Queries . . . . . . . . . . . . . . . 28 103 6.2. IGMP State Maintained by Multicast Routers . . . . . . . 29 104 6.2.1. Definition of Router Filter-Mode . . . . . . . . . . 29 105 6.2.2. Definition of Group Timers . . . . . . . . . . . . . 30 106 6.2.3. Definition of Source Timers . . . . . . . . . . . . . 31 107 6.3. IGMPv3 Source-Specific Forwarding Rules . . . . . . . . . 32 108 6.4. Action on Reception of Reports . . . . . . . . . . . . . 33 109 6.4.1. Reception of Current-State Records . . . . . . . . . 33 110 6.4.2. Reception of Filter-Mode-Change and Source-List-Change 111 Records . . . . . . . . . . . . . . . . . . . . . . . 35 112 6.5. Switching Router Filter-Modes . . . . . . . . . . . . . . 36 113 6.6. Action on Reception of Queries . . . . . . . . . . . . . 37 114 6.6.1. Timer Updates . . . . . . . . . . . . . . . . . . . . 37 115 6.6.2. Querier Election . . . . . . . . . . . . . . . . . . 37 116 6.6.3. Building and Sending Specific Queries . . . . . . . . 38 117 7. Interoperation With Older Versions of IGMP . . . . . . . . . 39 118 7.1. Query Version Distinctions . . . . . . . . . . . . . . . 39 119 7.2. Group Member Behavior . . . . . . . . . . . . . . . . . . 39 120 7.2.1. In the Presence of Older Version Queriers . . . . . . 39 121 7.2.2. In the Presence of Older Version Group Members . . . 41 122 7.3. Multicast Router Behavior . . . . . . . . . . . . . . . . 41 123 7.3.1. In the Presence of Older Version Queriers . . . . . . 41 124 7.3.2. In the Presence of Older Version Group Members . . . 41 125 8. List of Timers, Counters and Their Default Values . . . . . . 43 126 8.1. Robustness Variable . . . . . . . . . . . . . . . . . . . 44 127 8.2. Query Interval . . . . . . . . . . . . . . . . . . . . . 44 128 8.3. Query Response Interval . . . . . . . . . . . . . . . . . 44 129 8.4. Group Membership Interval . . . . . . . . . . . . . . . . 44 130 8.5. Other Querier Present Interval . . . . . . . . . . . . . 44 131 8.6. Startup Query Interval . . . . . . . . . . . . . . . . . 45 132 8.7. Startup Query Count . . . . . . . . . . . . . . . . . . . 45 133 8.8. Last Member Query Interval . . . . . . . . . . . . . . . 45 134 8.9. Last Member Query Count . . . . . . . . . . . . . . . . . 45 135 8.10. Last Member Query Time . . . . . . . . . . . . . . . . . 45 136 8.11. Unsolicited Report Interval . . . . . . . . . . . . . . . 45 137 8.12. Older Version Querier Present Interval . . . . . . . . . 46 138 8.13. Older Host Present Interval . . . . . . . . . . . . . . . 46 139 8.14. Configuring Timers . . . . . . . . . . . . . . . . . . . 46 140 8.14.1. Robustness Variable . . . . . . . . . . . . . . . . 46 141 8.14.2. Query Interval . . . . . . . . . . . . . . . . . . . 47 142 8.14.3. Max Response Time . . . . . . . . . . . . . . . . . 47 143 9. Security Considerations . . . . . . . . . . . . . . . . . . . 47 144 9.1. Query Message . . . . . . . . . . . . . . . . . . . . . . 48 145 9.2. Current-State Report messages . . . . . . . . . . . . . . 48 146 9.3. State-Change Report Messages . . . . . . . . . . . . . . 49 147 9.4. 9.4. IPSEC Usage . . . . . . . . . . . . . . . . . . . . 50 148 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 50 149 11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 51 150 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 51 151 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 51 152 13.1. Normative References . . . . . . . . . . . . . . . . . . 51 153 13.2. Informative References . . . . . . . . . . . . . . . . . 52 154 Appendix A. Design Rationale . . . . . . . . . . . . . . . . . . 52 155 A.1. The Need for State-Change Messages . . . . . . . . . . . 52 156 A.2. Host Suppression . . . . . . . . . . . . . . . . . . . . 53 157 A.3. Switching Router Filter Modes from EXCLUDE to INCLUDE . . 53 158 Appendix B. Summary of Changes from IGMPv2 . . . . . . . . . . . 54 159 Appendix C. Summary of Changes from RFC 3376 . . . . . . . . . . 54 160 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 55 162 1. Introduction 164 The Internet Group Management Protocol (IGMP) is used by IPv4 systems 165 (hosts and routers) to report their IP multicast group memberships to 166 any neighboring multicast routers. Note that an IP multicast router 167 may itself be a member of one or more multicast groups, in which case 168 it performs both the multicast router part of the protocol (to 169 collect the membership information needed by its multicast routing 170 protocol) and the group member part of the protocol (to inform itself 171 and other, neighboring multicast routers of its memberships). 11.nit: i would also remove the parenthesis around the the two explanations. 173 IGMP is also used for other IP multicast management functions, using 174 message types other than those used for group membership reporting. 175 This document specifies only the group membership reporting functions 176 and messages. 178 This document specifies Version 3 of IGMP. Version 1, specified in 179 [RFC1112], was the first widely-deployed version and the first 180 version to become an Internet Standard. Version 2, specified in 181 [RFC2236], added support for low leave latency, that is, a reduction 182 in the time it takes for a multicast router to learn that there are 183 no longer any members of a particular group present on an attached 184 network. Version 3 adds support for source filtering, that is, the 185 ability for a system to report interest in receiving packets only 186 from specific source addresses, as required to support Source- 187 Specific Multicast [RFC3569], or from all but specific source 12.minor: s/RFC3569/RFC4607/ I think we should consider RFC3569 only further reading, but the requirements are from RFC4607. Could even be 4604, i am not 100% sure, but 4607 sounds better to me. 188 addresses, sent to a particular multicast address. Version 3 is 189 designed to be interoperable with Versions 1 and 2. 191 This document uses SSM-aware to refer to systems that support Source- 192 Specific Multicast (SSM) as defined in [RFC4607]. 13.minor: Given how RFC4604 is an update to RFC3376, and given how this draft inlines several core requirements for SSM groups, which i think are from RFC4604, and/or hopefully do not conflict with RFC4604, i think we need to explicitly refer to RFC4604. Suggested rewrite: This document uses SSM-aware to refer to systems that support Source-Specific Multicast (SSM) as defined in [RFC4607] for IP. In addition to the requirements in this document, SSM-aware systems must also support [RFC4607] which defines additional requirements for use of IGMPv1, IGMPv2, IGMPv3 with SSM. This document inherits and updates the core requirements of [RFC4607]. For further information on SSM refer to [RFC3569]. 194 This document obsoletes [RFC3376]. 196 The capitalized key words "MUST", "MUST NOT", "REQUIRED", "SHALL", 197 "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and 198 "OPTIONAL" in this document are to be interpreted as described in 199 [RFC2119]. 14.minor: Use the new template text: The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and only when, they appear in all capitals, as shown here. 201 2. The Service Interface for Requesting IP Multicast Reception 203 Within an IP system, there is (at least conceptually) a service 204 interface used by upper-layer protocols or application programs to 205 ask the IP layer to enable and disable reception of packets sent to 206 specific IP multicast addresses. In order to take full advantage of 207 the capabilities of IGMPv3, a system's IP service interface must 208 support the following operation: 210 IPMulticastListen ( socket, interface, multicast-address, 211 filter-mode, source-list ) 213 where: 215 * "socket" is an implementation-specific parameter used to 216 distinguish among different requesting entities (e.g., programs or 217 processes) within the system; the socket parameter of BSD Unix 218 system calls is a specific example. 220 * "interface" is a local identifier of the network interface on 221 which reception of the specified multicast address is to be 222 enabled or disabled. Interfaces may be physical (e.g., an 223 Ethernet interface) or virtual (e.g., the endpoint of a Frame 224 Relay virtual circuit or the endpoint of an IP-in-IP "tunnel"). 225 An implementation may allow a special "unspecified" value to be 226 passed as the interface parameter, in which case the request would 227 apply to the "primary" or "default" interface of the system 228 (perhaps established by system configuration). If reception of 229 the same multicast address is desired on more than one interface, 230 IPMulticastListen is invoked separately for each desired 231 interface. 233 * "multicast-address" is the IP multicast address, or group, to 234 which the request pertains. If reception of more than one 235 multicast address on a given interface is desired, 236 IPMulticastListen is invoked separately for each desired multicast 237 address. 239 * "filter-mode" may be either INCLUDE or EXCLUDE. In INCLUDE mode, 240 reception of packets sent to the specified multicast address is 241 requested only from those IP source addresses listed in the 242 source-list parameter. In EXCLUDE mode, reception of packets sent 243 to the given multicast address is requested from all IP source 244 addresses except those listed in the source-list parameter. 246 * "source-list" is an unordered list of zero or more IP unicast 247 addresses from which multicast reception is desired or not 248 desired, depending on the filter mode. An implementation MAY 249 impose a limit on the size of source lists, but that limit MUST 250 NOT be less than 64 addresses per list. When an operation causes 251 the source list size limit to be exceeded, the service interface 252 MUST return an error. 254 For a given combination of socket, interface, and multicast address, 255 only a single filter mode and source list can be in effect at any one 256 time. However, either the filter mode or the source list, or both, 257 may be changed by subsequent IPMulticastListen requests that specify 258 the same socket, interface, and multicast address. Each subsequent 259 request completely replaces any earlier request for the given socket, 260 interface and multicast address. 262 Previous versions of IGMP did not support source filters and had a 263 simpler service interface consisting of Join and Leave operations to 264 enable and disable reception of a given multicast address (from all 265 sources) on a given interface. The equivalent operations in the new 266 service interface follow: 268 The Join operation is equivalent to: 270 IPMulticastListen ( socket, interface, multicast-address, 271 EXCLUDE, {} ) 273 and the Leave operation is equivalent to: 275 IPMulticastListen ( socket, interface, multicast-address, 276 INCLUDE, {} ) 278 where {} is an empty source list. 280 An example of an API providing the capabilities outlined in this 281 service interface is in [RFC3678]. 283 3. Multicast Reception State Maintained by Systems 285 3.1. Socket State 287 For each socket on which IPMulticastListen has been invoked, the 288 system records the desired multicast reception state for that socket. 289 That state conceptually consists of a set of records of the form: 291 (interface, multicast-address, filter-mode, source-list) 293 The socket state evolves in response to each invocation of 294 IPMulticastListen on the socket, as follows: 296 * If the requested filter mode is INCLUDE and the requested source 297 list is empty, then the entry corresponding to the requested 298 interface and multicast address is deleted if present. If no such 299 entry is present, the request is ignored. 301 * If the requested filter mode is EXCLUDE or the requested source 302 list is non-empty, then the entry corresponding to the requested 303 interface and multicast address, if present, is changed to contain 304 the requested filter mode and source list. If no such entry is 305 present, a new entry is created, using the parameters specified in 306 the request. 308 3.2. Interface State 310 In addition to the per-socket multicast reception state, a system 311 must also maintain or compute multicast reception state for each of 312 its interfaces. That state conceptually consists of a set of records 313 of the form: 315 (multicast-address, filter-mode, source-list) 317 At most one record per multicast-address exists for a given 318 interface. This per-interface state is derived from the per-socket 319 state, but may differ from the per-socket state when different 320 sockets have differing filter modes and/or source lists for the same 321 multicast address and interface. For example, suppose one 322 application or process invokes the following operation on socket s1: 324 IPMulticastListen ( s1, i, m, INCLUDE, {a, b, c} ) 326 requesting reception on interface i of packets sent to multicast 327 address m, only if they come from source a, b, or c. Suppose another 328 application or process invokes the following operation on socket s2: 330 IPMulticastListen ( s2, i, m, INCLUDE, {b, c, d} ) 332 requesting reception on the same interface i of packets sent to the 333 same multicast address m, only if they come from sources b, c, or d. 334 In order to satisfy the reception requirements of both sockets, it is 335 necessary for interface i to receive packets sent to m from any one 336 of the sources a, b, c, or d. Thus, in this example, the reception 337 state of interface i for multicast address m has filter mode INCLUDE 338 and source list {a, b, c, d}. 340 After a multicast packet has been accepted from an interface by the 341 IP layer, its subsequent delivery to the application or process 342 listening on a particular socket depends on the multicast reception 343 state of that socket [and possibly also on other conditions, such as 344 what transport-layer port the socket is bound to]. So, in the above 345 example, if a packet arrives on interface i, destined to multicast 346 address m, with source address a, it will be delivered on socket s1 347 but not on socket s2. Note that IGMP Queries and Reports are not 348 subject to source filtering and must always be processed by hosts and 349 routers. 351 Filtering of packets based upon a socket's multicast reception state 352 is a new feature of this service interface. The previous service 353 interface [RFC1112] described no filtering based upon multicast join 354 state; rather, a join on a socket simply caused the host to join a 355 group on the given interface, and packets destined for that group 356 could be delivered to all sockets whether they had joined or not. 358 The general rules for deriving the per-interface state from the per- 359 socket state are as follows: For each distinct (interface, multicast- 360 address) pair that appears in any socket state, a per- interface 361 record is created for that multicast address on that interface. 362 Considering all socket records containing the same (interface, 363 multicast-address) pair, 365 * if any such record has a filter mode of EXCLUDE, then the filter 366 mode of the interface record is EXCLUDE, and the source list of 367 the interface record is the intersection of the source lists of 368 all socket records in EXCLUDE mode, minus those source addresses 369 that appear in any socket record in INCLUDE mode. For example, if 370 the socket records for multicast address m on interface i are: 372 from socket s1: ( i, m, EXCLUDE, {a, b, c, d} ) 374 from socket s2: ( i, m, EXCLUDE, {b, c, d, e} ) 376 from socket s3: ( i, m, INCLUDE, {d, e, f} ) 378 then the corresponding interface record on interface i is: 380 ( m, EXCLUDE, {b, c} ) 382 If a fourth socket is added, such as: 384 from socket s4: ( i, m, EXCLUDE, {} ) 386 then the interface record becomes: 388 ( m, EXCLUDE, {} ) 390 * if all such records have a filter mode of INCLUDE, then the filter 391 mode of the interface record is INCLUDE, and the source list of 392 the interface record is the union of the source lists of all the 393 socket records. For example, if the socket records for multicast 394 address m on interface i are: 396 from socket s1: ( i, m, INCLUDE, {a, b, c} ) 398 from socket s2: ( i, m, INCLUDE, {b, c, d} ) 400 from socket s3: ( i, m, INCLUDE, {e, f} ) 402 then the corresponding interface record on interface i is: 404 ( m, INCLUDE, {a, b, c, d, e, f} ) 406 An implementation MUST NOT use an EXCLUDE interface record to 407 represent a group when all sockets for this group are in INCLUDE 408 state. If system resource limits are reached when an interface 409 state source list is calculated, an error MUST be returned to the 410 application which requested the operation. 412 The above rules for deriving the interface state are (re-)evaluated 413 whenever an IPMulticastListen invocation modifies the socket state by 414 adding, deleting, or modifying a per-socket state record. Note that 415 a change of socket state does not necessarily result in a change of 416 interface state. 418 4. Message Formats 420 IGMP messages are encapsulated in IPv4 datagrams, with an IP protocol 421 number of 2. Every IGMP message described in this document is sent 422 with an IP Time-to-Live of 1, IP Precedence of Internetwork Control 423 (e.g., Type of Service 0xc0), and carries an IP Router Alert option 424 [RFC2113] in its IP header. IGMP message types are registered per 425 [I-D.ietf-pim-3228bis]. 427 There are two IGMP message types of concern to the IGMPv3 protocol 428 described in this document: 430 +===================+=============================+ 431 | Type Number (hex) | Message Name | 432 +===================+=============================+ 433 | 0x11 | Membership Query | 434 +-------------------+-----------------------------+ 435 | 0x22 | Version 3 Membership Report | 436 +-------------------+-----------------------------+ 438 Table 1: New messages introduced by IGMP3 15.minor: This should reflect the format of the IANA "IGMP Type Numbers" table: +===================+=============================+===========+ | Type Number (hex) | Message Name | Reference | +===================+=============================+-----------+ | 0x11 | Membership Query | [RFC1112] | +-------------------+-----------------------------+-----------+ | 0x22 | Version 3 Membership Report | [ThisRFC] | +-------------------+-----------------------------+-----------+ 440 An implementation of IGMPv3 MUST also support the following three 441 message types, for interoperation with previous versions of IGMP (see 442 Section 7): 444 +===================+=============================+===========+ 445 | Type Number (hex) | Message Name | Reference | 446 +===================+=============================+===========+ 447 | 0x12 | Version 1 Membership Report | [RFC1112] | 448 +-------------------+-----------------------------+-----------+ 449 | 0x16 | Version 2 Membership Report | [RFC2236] | 450 +-------------------+-----------------------------+-----------+ 451 | 0x17 | Version 2 Leave Group | [RFC2236] | 452 +-------------------+-----------------------------+-----------+ 454 Table 2: Legacy IGMP messages 456 Unrecognized message types MUST be silently ignored. Other message 457 types may be used by newer versions or extensions of IGMP, by 458 multicast routing protocols, or for other uses. 460 In this document, unless otherwise qualified, the capitalized words 461 "Query" and "Report" refer to IGMP Membership Queries and IGMP 462 Version 3 Membership Reports, respectively. 464 4.1. Membership Query Message 466 Membership Queries are sent by IP multicast routers to query the 467 multicast reception state of neighboring interfaces. Queries have 468 the following format: 470 0 1 2 3 471 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 472 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 473 | Type = 0x11 | Max Resp Code | Checksum | 474 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 475 | Group Address | 476 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 477 | Flags |S| QRV | QQIC | Number of Sources (N) | 478 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 479 | Source Address [1] | 480 +- -+ 481 | Source Address [2] | 482 +- . -+ 483 . . . 484 . . . 485 +- -+ 486 | Source Address [N] | 487 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 489 Figure 1: IGMPv3 Query Message 491 4.1.1. Max Resp Code 493 The Max Resp Code field specifies the maximum time allowed before 494 sending a responding report. The actual time allowed, called the Max 495 Resp Time, is represented in units of 1/10 second and is derived from 496 the Max Resp Code as follows: 498 If Max Resp Code < 128, Max Resp Time = Max Resp Code 500 If Max Resp Code >= 128, Max Resp Code represents a floating-point 501 value as follows: 503 0 1 2 3 4 5 6 7 504 +-+-+-+-+-+-+-+-+ 505 |1| exp | mant | 506 +-+-+-+-+-+-+-+-+ 508 Max Resp Time = (mant | 0x10) << (exp + 3) 510 Figure 2: Max Resp Code Representation 512 Small values of Max Resp Time allow IGMPv3 routers to tune the "leave 513 latency" (the time between the moment the last host leaves a group 514 and the moment the routing protocol is notified that there are no 515 more members). Larger values, especially in the exponential range, 516 allow tuning of the burstiness of IGMP traffic on a network. 518 4.1.2. Checksum 520 The Checksum is the 16-bit one's complement of the one's complement 521 sum of the whole IGMP message (the entire IP payload). For computing 522 the checksum, the Checksum field is set to zero. When receiving 523 packets, the checksum MUST be verified before processing a packet 524 [RFC1071]. 526 4.1.3. Group Address 528 The Group Address field is set to zero when sending a General Query, 529 and set to the IP multicast address being queried when sending a 530 Group-Specific Query or Group-and-Source-Specific Query (see 531 Section Section 4.1.9, below). 16.nit: duplicate "Section Section" 533 4.1.4. Flags 535 The Flags field is a bitstring managed by an IANA registry defined in 536 [I-D.ietf-pim-3228bis]. 17.minor: I think we need to add to that paragraph: Unused/undefined Flag are set to zero on transmission and ignored on receipt. This specification does not specify or use any Flags. Reasoning: neither this draft nor rfc3228 specifies the set-to-zero-ignore-on-receipt. That is a candidte for backward compatibility issues, because rfc3367 says this. The "not specify any flags" is somewhat reconfirming, but i think its helpful so readers don't wonder. Alternatively we could not write all or some of this here but in rfc3228bis, which might suffice but would be harder to read. 538 4.1.5. S Flag (Suppress Router-Side Processing) 540 When set to one, the S Flag indicates to any receiving multicast 541 routers that they are to suppress the normal timer updates they 542 perform upon hearing a Query. It does not, however, suppress the 543 querier election or the normal "host-side" processing of a Query that 544 a router may be required to perform as a consequence of itself being 545 a group member. 547 4.1.6. QRV (Querier's Robustness Variable) 549 If non-zero, the QRV field contains the [Robustness Variable] value 550 used by the querier, i.e., the sender of the Query. If the querier's 551 [Robustness Variable] exceeds 7, the maximum value of the QRV field, 552 the QRV is set to zero. Routers adopt the QRV value from the most 553 recently received Query as their own [Robustness Variable] value, 554 unless that most recently received QRV was zero, in which case the 555 receivers use the default [Robustness Variable] value specified in 556 section Section 8.1 or a statically configured value. 558 4.1.7. QQIC (Querier's Query Interval Code) 560 The Querier's Query Interval Code field specifies the [Query 561 Interval] used by the querier. The actual interval, called the 562 Querier's Query Interval (QQI), is represented in units of seconds 563 and is derived from the Querier's Query Interval Code as follows: 565 If QQIC < 128, QQI = QQIC 566 If QQIC >= 128, QQIC represents a floating-point value as follows: 568 0 1 2 3 4 5 6 7 569 +-+-+-+-+-+-+-+-+ 570 |1| exp | mant | 571 +-+-+-+-+-+-+-+-+ 573 QQI = (mant | 0x10) << (exp + 3) 575 Figure 3: QQIC Representation 577 Multicast routers that are not the current querier adopt the QQI 578 value from the most recently received Query as their own [Query 579 Interval] value, unless that most recently received QQI was zero, in 580 which case the receiving routers use the default [Query Interval] 581 value specified in Section 8.2. 583 4.1.8. Number of Sources (N) 585 The Number of Sources (N) field specifies how many source addresses 586 are present in the Query. This number is zero in a General Query or 587 a Group-Specific Query, and non-zero in a Group-and-Source-Specific 588 Query. This number is limited by the MTU of the network over which 589 the Query is transmitted. For example, on an Ethernet with an MTU of 590 1500 octets, the IP header including the Router Alert option consumes 591 24 octets, and the IGMP fields up to including the Number of Sources 592 (N) field consume 12 octets, leaving 1464 octets for source 593 addresses, which limits the number of source addresses to 366 594 (1464/4). 596 4.1.9. Source Address [i] 598 The Source Address [i] fields are a vector of n IP unicast addresses, 599 where n is the value in the Number of Sources (N) field. 601 4.1.10. Additional Data 603 If the Packet Length field in the IP header of a received Query 604 indicates that there are additional octets of data present, beyond 605 the fields described here, IGMPv3 implementations MUST include those 606 octets in the computation to verify the received IGMP Checksum, but 607 MUST otherwise ignore those additional octets. When sending a Query, 608 an IGMPv3 implementation MUST NOT include additional octets beyond 609 the fields described here. 611 4.1.11. Query Variants 613 There are three variants of the Query message: 615 1. A General Query is sent by a multicast router to learn the 616 complete multicast reception state of the neighboring interfaces 617 (that is, the interfaces attached to the network on which the 618 Query is transmitted). In a General Query, both the Group 619 Address field and the Number of Sources (N) field are zero. 621 2. A Group-Specific Query is sent by a multicast router to learn the 622 reception state, with respect to a single multicast address, of 623 the neighboring interfaces. In a Group-Specific Query, the Group 624 Address field contains the multicast address of interest, and the 625 Number of Sources (N) field contains zero. 627 3. A Group-and-Source-Specific Query is sent by a multicast router 628 to learn if any neighboring interface desires reception of 629 packets sent to a specified multicast address, from any of a 630 specified list of sources. In a Group-and-Source-Specific Query, 631 the Group Address field contains the multicast address of 632 interest, and the Source Address [i] fields contain the source 633 address(es) of interest. 635 4.1.12. IP Destination Addresses for Queries 637 In IGMPv3, General Queries are sent with an IP destination address of 638 224.0.0.1, the all-systems multicast address. Group-Specific and 639 Group-and-Source-Specific Queries are sent with an IP destination 640 address equal to the multicast address of interest. However, a 641 system MUST accept and process any Query whose IP Destination Address 642 field contains any of the addresses (unicast or multicast) assigned 643 to the interface on which the Query arrives. 645 4.2. Version 3 Membership Report Message 647 Version 3 Membership Reports are sent by IP systems to report (to 648 neighboring routers) the current multicast reception state, or 649 changes in the multicast reception state, of their interfaces. 650 Reports have the following format: 652 0 1 2 3 653 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 654 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 655 | Type = 0x22 | Reserved | Checksum | 656 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 657 | Flags | Number of Group Records (M) | 658 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 659 | | 660 . . 661 . Group Record [1] . 662 . . 663 | | 664 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 665 | | 666 . . 667 . Group Record [2] . 668 . . 669 | | 670 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 671 | . | 672 . . . 673 | . | 674 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 675 | | 676 . . 677 . Group Record [M] . 678 . . 679 | | 680 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 682 Figure 4: IGMPv3 Report Message 684 where each Group Record has the following internal format: 686 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 687 | Record Type | Aux Data Len | Number of Sources (N) | 688 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 689 | Multicast Address | 690 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 691 | Source Address [1] | 692 +- -+ 693 | Source Address [2] | 694 +- -+ 695 . . . 696 . . . 697 . . . 698 +- -+ 699 | Source Address [N] | 700 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 701 | | 702 . . 703 . Auxiliary Data . 704 . . 705 | | 706 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 708 Figure 5: IGMPv3 Report Group Record 710 4.2.1. Reserved 712 The Reserved field is set to zero on transmission, and ignored on 713 reception. 715 4.2.2. Checksum 717 The Checksum is the 16-bit one's complement of the one's complement 718 sum of the whole IGMP message (the entire IP payload). For computing 719 the checksum, the Checksum field is set to zero. When receiving 720 packets, the checksum MUST be verified before processing a message. 722 4.2.3. Flags 724 The Flags field is a bitstring managed by an IANA registry defined in 725 [I-D.ietf-pim-3228bis]. 18.minor: I think we need to add to that paragraph: Unused/undefined Flag are set to zero on transmission and ignored on receipt. This specification does not specify or use any Flags. same reasoning as in 4.1.4 727 4.2.4. Number of Group Records (M) 729 The Number of Group Records (M) field specifies how many Group 730 Records are present in this Report. 732 4.2.5. Group Record 734 Each Group Record is a block of fields containing information 735 pertaining to the sender's membership in a single multicast group on 736 the interface from which the Report is sent. 738 4.2.6. Record Type 740 See section Section 4.2.13, below. 742 4.2.7. Aux Data Len 744 The Aux Data Len field contains the length of the Auxiliary Data 745 field in this Group Record, in units of 32-bit words. It may contain 746 zero, to indicate the absence of any auxiliary data. 748 4.2.8. Number of Sources (N) 750 The Number of Sources (N) field specifies how many source addresses 751 are present in this Group Record. 753 4.2.9. Multicast Address 755 The Multicast Address field contains the IP multicast address to 756 which this Group Record pertains. 758 4.2.10. Source Address [i] 760 The Source Address [i] fields are a vector of n IP unicast addresses, 761 where n is the value in this record's Number of Sources (N) field. 763 4.2.11. Auxiliary Data 765 The Auxiliary Data field, if present, contains additional information 766 pertaining to this Group Record. The protocol specified in this 767 document, IGMPv3, does not define any auxiliary data. Therefore, 768 implementations of IGMPv3 MUST NOT include any auxiliary data (i.e., 769 MUST set the Aux Data Len field to zero) in any transmitted Group 770 Record, and MUST ignore any auxiliary data present in any received 771 Group Record. The semantics and internal encoding of the Auxiliary 772 Data field are to be defined by any future version or extension of 773 IGMP that uses this field. 775 4.2.12. Additional Data 777 If the Packet Length field in the IP header of a received Report 778 indicates that there are additional octets of data present, beyond 779 the last Group Record, IGMPv3 implementations MUST include those 780 octets in the computation to verify the received IGMP Checksum, but 781 MUST otherwise ignore those additional octets. When sending a 782 Report, an IGMPv3 implementation MUST NOT include additional octets 783 beyond the last Group Record. 785 4.2.13. Group Record Types 787 There are a number of different types of Group Records that may be 788 included in a Report message: 790 * A Current-State Record is sent by a system in response to a Query 791 received on an interface. It reports the current reception state 792 of that interface, with respect to a single multicast address. 793 The Record Type of a Current-State Record may be one of the 794 following two values: 796 1 - MODE_IS_INCLUDE - indicates that the interface has a filter 797 mode of INCLUDE for the specified multicast address. The 798 Source Address [i] fields in this Group Record contain the 799 interface's source list for the specified multicast address, 800 if it is non-empty. 802 2 - MODE_IS_EXCLUDE - indicates that the interface has a filter 803 mode of EXCLUDE for the specified multicast address. The 804 Source Address [i] fields in this Group Record contain the 805 interface's source list for the specified multicast address, 806 if it is non-empty. An SSM-aware host SHOULD NOT send a 807 MODE_IS_EXCLUDE record type for multicast addresses that fall 808 within the SSM address range. 810 * A Filter-Mode-Change Record is sent by a system whenever a local 811 invocation of IPMulticastListen causes a change of the filter mode 812 (i.e., a change from INCLUDE to EXCLUDE, or from EXCLUDE to 813 INCLUDE), of the interface-level state entry for a particular 814 multicast address. The Record is included in a Report sent from 815 the interface on which the change occurred. The Record Type of a 816 Filter-Mode-Change Record may be one of the following two values: 818 3 - CHANGE_TO_INCLUDE_MODE - indicates that the interface has 819 changed to INCLUDE filter mode for the specified multicast 820 address. The Source Address [i] fields in this Group Record 821 contain the interface's new source list for the specified 822 multicast address, if it is non-empty. 824 4 - CHANGE_TO_EXCLUDE_MODE - indicates that the interface has 825 changed to EXCLUDE filter mode for the specified multicast 826 address. The Source Address [i] fields in this Group Record 827 contain the interface's new source list for the specified 828 multicast address, if it is non-empty. An SSM-aware host 829 SHOULD NOT send a CHANGE_TO_EXCLUDE_MODE record type for 830 multicast addresses that fall within the SSM address range. 832 * A Source-List-Change Record is sent by a system whenever a local 833 invocation of IPMulticastListen causes a change of source list 834 that is not coincident with a change of filter mode, of the 835 interface-level state entry for a particular multicast address. 836 The Record is included in a Report sent from the interface on 837 which the change occurred. The Record Type of a Source-List- 838 Change Record may be one of the following two values: 840 5 - ALLOW_NEW_SOURCES - indicates that the Source Address [i] 841 fields in this Group Record contain a list of the additional 842 sources that the system wishes to hear from, for packets sent 843 to the specified multicast address. If the change was to an 844 INCLUDE source list, these are the addresses that were added 845 to the list; if the change was to an EXCLUDE source list, 846 these are the addresses that were deleted from the list. 848 6 - BLOCK_OLD_SOURCES - indicates that the Source Address [i] 849 fields in this Group Record contain a list of the sources 850 that the system no longer wishes to hear from, for packets 851 sent to the specified multicast address. If the change was 852 to an INCLUDE source list, these are the addresses that were 853 deleted from the list; if the change was to an EXCLUDE source 854 list, these are the addresses that were added to the list. 856 If a change of source list results in both allowing new sources and 857 blocking old sources, then two Group Records are sent for the same 858 multicast address, one of type ALLOW_NEW_SOURCES and one of type 859 BLOCK_OLD_SOURCES. 861 We use the term State-Change Record to refer to either a Filter- 862 Mode-Change Record or a Source-List-Change Record. 864 Unrecognized Record Type values MUST be silently ignored. 866 4.2.14. IP Source Addresses for Reports 868 An IGMP report is sent with a valid IP source address for the 869 destination subnet. The 0.0.0.0 source address may be used by a 870 system that has not yet acquired an IP address. Note that the 871 0.0.0.0 source address may simultaneously be used by multiple systems 872 on a LAN. Routers MUST accept a report with a source address of 873 0.0.0.0. 875 4.2.15. IP Destination Addresses for Reports 877 Version 3 Reports are sent with an IP destination address of 878 224.0.0.22, to which all IGMPv3-capable multicast routers listen. A 879 system that is operating in version 1 or version 2 compatibility 880 modes sends version 1 or version 2 Reports to the multicast group 881 specified in the Group Address field of the Report. In addition, a 882 system MUST accept and process any version 1 or version 2 Report 883 whose IP Destination Address field contains any of the addresses 884 (unicast or multicast) assigned to the interface on which the Report 885 arrives. 887 4.2.16. Notation for Group Records 889 In the rest of this document, we use the following notation to 890 describe the contents of a Group Record pertaining to a particular 891 multicast address: 893 IS_IN ( x ) - Type MODE_IS_INCLUDE, source addresses x 894 IS_EX ( x ) - Type MODE_IS_EXCLUDE, source addresses x 895 TO_IN ( x ) - Type CHANGE_TO_INCLUDE_MODE, source addresses x 896 TO_EX ( x ) - Type CHANGE_TO_EXCLUDE_MODE, source addresses x 897 ALLOW ( x ) - Type ALLOW_NEW_SOURCES, source addresses x 898 BLOCK ( x ) - Type BLOCK_OLD_SOURCES, source addresses x 900 where x is either: 902 * a capital letter (e.g., "A") to represent the set of source 903 addresses, or 905 * a set expression (e.g., "A+B"), where "A+B" means the union of 906 sets A and B, "A*B" means the intersection of sets A and B, and 907 "A-B" means the removal of all elements of set B from set A. 909 4.2.17. Membership Report Size 911 If the set of Group Records required in a Report does not fit within 912 the size limit of a single Report message (as determined by the MTU 913 of the network on which it will be sent), the Group Records are sent 914 in as many Report messages as needed to report the entire set. 916 If a single Group Record contains so many source addresses that it 917 does not fit within the size limit of a single Report message, if its 918 Type is not MODE_IS_EXCLUDE or CHANGE_TO_EXCLUDE_MODE, it is split 919 into multiple Group Records, each containing a different subset of 920 the source addresses and each sent in a separate Report message. If 921 its Type is MODE_IS_EXCLUDE or CHANGE_TO_EXCLUDE_MODE, a single Group 922 Record is sent, containing as many source addresses as can fit, and 924 the remaining source addresses are not reported; though the choice of 925 which sources to report is arbitrary, it is preferable to report the 926 same set of sources in each subsequent report, rather than reporting 927 different sources each time. 929 5. Description of the Protocol for Group Members 931 IGMP is an asymmetric protocol, specifying separate behaviors for 932 group members -- that is, hosts or routers that wish to receive 933 multicast packets -- and multicast routers. This section describes 934 the part of IGMPv3 that applies to all group members. (Note that a 935 multicast router that is also a group member performs both parts of 936 IGMPv3, receiving and responding to its own IGMP message 937 transmissions as well as those of its neighbors. The multicast 938 router part of IGMPv3 is described in Section 6.) 940 A system performs the protocol described in this section over all 941 interfaces on which multicast reception is supported, even if more 942 than one of those interfaces is connected to the same network. 944 For interoperability with multicast routers running older versions of 945 IGMP, systems maintain a MulticastRouterVersion variable for each 946 interface on which multicast reception is supported. This section 947 describes the behavior of group member systems on interfaces for 948 which MulticastRouterVersion = 3. The algorithm for determining 949 MulticastRouterVersion, and the behavior for versions other than 3, 950 are described in Section 7. 952 The all-systems multicast address, 224.0.0.1, is handled as a special 953 case. On all systems -- that is all hosts and routers, including 954 multicast routers -- reception of packets destined to the all-systems 955 multicast address, from all sources, is permanently enabled on all 956 interfaces on which multicast reception is supported. No IGMP 957 messages are ever sent regarding the all-systems multicast address. 959 There are two types of events that trigger IGMPv3 protocol actions on 960 an interface: 962 * a change of the interface reception state, caused by a local 963 invocation of IPMulticastListen. 965 * reception of a Query. 967 (Received IGMP messages of types other than Query are silently 968 ignored, except as required for interoperation with earlier versions 969 of IGMP.) 971 The following subsections describe the actions to be taken for each 972 of these two cases. In those descriptions, timer and counter names 973 appear in square brackets. The default values for those timers and 974 counters are specified in Section 8. 976 5.1. Action on Change of Interface State 978 An invocation of IPMulticastListen may cause the multicast reception 979 state of an interface to change, according to the rules in 980 Section Section 3.2. Each such change affects the per-interface 981 entry for a single multicast address. 983 A change of interface state causes the system to immediately transmit 984 a State-Change Report from that interface. The type and contents of 985 the Group Record(s) in that Report are determined by comparing the 986 filter mode and source list for the affected multicast address before 987 and after the change, according to the table below. If no interface 988 state existed for that multicast address before the change (i.e., the 989 change consisted of creating a new per-interface record), or if no 990 state exists after the change (i.e., the change consisted of deleting 991 a per-interface record), then the "non-existent" state is considered 992 to have a filter mode of INCLUDE and an empty source list. 994 +=============+=============+==========================+ 995 | Old State | New State | State-Change Record Sent | 996 +=============+=============+==========================+ 997 | INCLUDE (A) | INCLUDE (B) | ALLOW (B-A), BLOCK (A-B) | 998 +-------------+-------------+--------------------------+ 999 | EXCLUDE (A) | EXCLUDE (B) | ALLOW (A-B), BLOCK (B-A) | 1000 +-------------+-------------+--------------------------+ 1001 | INCLUDE (A) | EXCLUDE (B) | TO_EX (B) | 1002 +-------------+-------------+--------------------------+ 1003 | EXCLUDE (A) | INCLUDE (B) | TO_IN (B) | 1004 +-------------+-------------+--------------------------+ 1006 Table 3 1008 If the computed source list for either an ALLOW or a BLOCK State- 1009 Change Record is empty, that record is omitted from the Report 1010 message. 1012 To cover the possibility of the State-Change Report being missed by 1013 one or more multicast routers, it is retransmitted [Robustness 1014 Variable] - 1 more times, at intervals chosen at random from the 1015 range (0, [Unsolicited Report Interval]). 1017 If more changes to the same interface state entry occur before all 1018 the retransmissions of the State-Change Report for the first change 1019 have been completed, each such additional change triggers the 1020 immediate transmission of a new State-Change Report. 1022 The contents of the new transmitted report are calculated as follows. 1023 As was done with the first report, the interface state for the 1024 affected group before and after the latest change is compared. The 1025 report records expressing the difference are built according to the 1026 table above. However these records are not transmitted in a message 1027 but instead merged with the contents of the pending report, to create 1028 the new State-Change report. The rules for merging the difference 1029 report resulting from the state change and the pending report are 1030 described below. 1032 The transmission of the merged State-Change Report terminates 1033 retransmissions of the earlier State-Change Reports for the same 1034 multicast address, and becomes the first of [Robustness Variable] 1035 transmissions of State-Change Reports. 1037 Each time a source is included in the difference report calculated 1038 above, retransmission state for that source needs to be maintained 1039 until [Robustness Variable] State-Change reports have been sent by 1040 the host. This is done in order to ensure that a series of 1041 successive state changes do not break the protocol robustness. 1043 If the interface reception-state change that triggers the new report 1044 is a filter-mode change, then the next [Robustness Variable] State- 1045 Change Reports will include a Filter-Mode-Change record. This 1046 applies even if any number of source-list changes occur in that 1047 period. The host has to maintain retransmission state for the group 1048 until the [Robustness Variable] State-Change reports have been sent. 1049 When [Robustness Variable] State-Change reports with Filter-Mode- 1050 Change records have been transmitted after the last filter-mode 1051 change, and if source-list changes to the interface reception have 1052 scheduled additional reports, then the next State-Change report will 1053 include Source-List-Change records. 1055 Each time a State-Change Report is transmitted, the contents are 1056 determined as follows. If the report should contain a Filter-Mode- 1057 Change record, then if the current filter-mode of the interface is 1058 INCLUDE, a TO_IN record is included in the report, otherwise a TO_EX 1059 record is included. If instead the report should contain Source- 1060 List-Change records, an ALLOW and a BLOCK record are included. The 1061 contents of these records are built according to the table below. 1063 +========+==============================+ 1064 | Record | Sources Included | 1065 +========+==============================+ 1066 | TO_IN | All in the current interface | 1067 | | state that must be forwarded | 1068 +--------+------------------------------+ 1069 | TO_EX | All in the current interface | 1070 | | state that must be blocked | 1071 +--------+------------------------------+ 1072 | ALLOW | All with retransmission | 1073 | | state that must be forwarded | 1074 +--------+------------------------------+ 1075 | BLOCK | All with retransmission | 1076 | | state that must be blocked | 1077 +--------+------------------------------+ 1079 Table 4 1081 If the computed source list for either an ALLOW or a BLOCK record is 1082 empty, that record is omitted from the State-Change report. 1084 Note: When the first State-Change report is sent, the non-existent 1085 pending report to merge with, can be treated as a source-change 1086 report with empty ALLOW and BLOCK records (no sources have 1087 retransmission state). 1089 5.2. Action on Reception of a Query 1091 When a system receives a Query, it does not respond immediately. 1092 Instead, it delays its response by a random amount of time, bounded 1093 by the Max Resp Time value derived from the Max Resp Code in the 1094 received Query message. A system may receive a variety of Queries on 1095 different interfaces and of different kinds (e.g., General Queries, 1096 Group-Specific Queries, and Group-and-Source-Specific Queries), each 1097 of which may require its own delayed response. 1099 Before scheduling a response to a Query, the system must first 1100 consider previously scheduled pending responses and in many cases 1101 schedule a combined response. Therefore, the system must be able to 1102 maintain the following state: 1104 * A timer per interface for scheduling responses to General Queries. 1106 * A per-group and interface timer for scheduling responses to Group- 1107 Specific and Group-and-Source-Specific Queries. 1109 * A per-group and interface list of sources to be reported in the 1110 response to a Group-and-Source-Specific Query. 1112 When a new Query with the Router-Alert option arrives on an 1113 interface, provided the system has state to report, a delay for a 1114 response is randomly selected in the range (0, [Max Resp Time]) where 1115 Max Resp Time is derived from Max Resp Code in the received Query 1116 message. The following rules are then used to determine if a Report 1117 needs to be scheduled and the type of Report to schedule. The rules 1118 are considered in order and only the first matching rule is applied. 1120 1. If there is a pending response to a previous General Query 1121 scheduled sooner than the selected delay, no additional response 1122 needs to be scheduled. 1124 2. If the received Query is a General Query, the interface timer is 1125 used to schedule a response to the General Query after the 1126 selected delay. Any previously pending response to a General 1127 Query is canceled. 1129 3. If the received Query is a Group-Specific Query or a Group-and- 1130 Source-Specific Query and there is no pending response to a 1131 previous Query for this group, then the group timer is used to 1132 schedule a report. If the received Query is a Group-and-Source- 1133 Specific Query, the list of queried sources is recorded to be 1134 used when generating a response. 1136 4. If there already is a pending response to a previous Query 1137 scheduled for this group, and either the new Query is a Group- 1138 Specific Query or the recorded source-list associated with the 1139 group is empty, then the group source-list is cleared and a 1140 single response is scheduled using the group timer. The new 1141 response is scheduled to be sent at the earliest of the remaining 1142 time for the pending report and the selected delay. 1144 5. If the received Query is a Group-and-Source-Specific Query and 1145 there is a pending response for this group with a non-empty 1146 source-list, then the group source list is augmented to contain 1147 the list of sources in the new Query and a single response is 1148 scheduled using the group timer. The new response is scheduled 1149 to be sent at the earliest of the remaining time for the pending 1150 report and the selected delay. 1152 When the timer in a pending response record expires, the system 1153 transmits, on the associated interface, one or more Report messages 1154 carrying one or more Current-State Records (see section 1155 Section 4.2.13), as follows: 1157 1. If the expired timer is the interface timer (i.e., it is a 1158 pending response to a General Query), then one Current-State 1159 Record is sent for each multicast address for which the specified 1160 interface has reception state, as described in Section 3.2. The 1161 Current- State Record carries the multicast address and its 1162 associated filter mode (MODE_IS_INCLUDE or MODE_IS_EXCLUDE) and 1163 source list. Multiple Current-State Records are packed into 1164 individual Report messages, to the extent possible. 1166 This naive algorithm may result in bursts of packets when a 1167 system is a member of a large number of groups. Instead of using 1168 a single interface timer, implementations are recommended to 1169 spread transmission of such Report messages over the interval (0, 1170 [Max Resp Time]). Note that any such implementation MUST avoid 1171 the "ack-implosion" problem, i.e., MUST NOT send a Report 1172 immediately on reception of a General Query. 1174 2. If the expired timer is a group timer and the list of recorded 1175 sources for the that group is empty (i.e., it is a pending 1176 response to a Group-Specific Query), then if and only if the 1177 interface has reception state for that group address, a single 1178 Current-State Record is sent for that address. The Current-State 1179 Record carries the multicast address and its associated filter 1180 mode (MODE_IS_INCLUDE or MODE_IS_EXCLUDE) and source list. 1182 3. If the expired timer is a group timer and the list of recorded 1183 sources for that group is non-empty (i.e., it is a pending 1184 response to a Group-and-Source-Specific Query), then if and only 1185 if the interface has reception state for that group address, the 1186 contents of the responding Current-State Record is determined 1187 from the interface state and the pending response record, as 1188 specified in the following table: 1190 +=====================+=========================+===============+ 1191 | Per-Interface State | Set of Sources in the | Current-State | 1192 | | Pending Response Record | Record | 1193 +=====================+=========================+===============+ 1194 | INCLUDE (A) | B | IS_IN (A*B) | 1195 +---------------------+-------------------------+---------------+ 1196 | EXCLUDE (A) | B | IS_IN (B-A) | 1197 +---------------------+-------------------------+---------------+ 1199 Table 5 1201 If the resulting Current-State Record has an empty set of source 1202 addresses, then no response is sent. 1204 Finally, after any required Report messages have been generated, the 1205 source lists associated with any reported groups are cleared. 1207 6. Description of the Protocol for Multicast Routers 1209 The purpose of IGMP is to enable each multicast router to learn, for 1210 each of its directly attached networks, which multicast addresses are 1211 of interest to the systems attached to those networks. IGMP version 1212 3 adds the capability for a multicast router to also learn which 1213 sources are of interest to neighboring systems, for packets sent to 1214 any particular multicast address. The information gathered by IGMP 1215 is provided to whichever multicast routing protocol is being used by 1216 the router, in order to ensure that multicast packets are delivered 1217 to all networks where there are interested receivers. 1219 This section describes the part of IGMPv3 that is performed by 1220 multicast routers. Multicast routers may also themselves become 1221 members of multicast groups, and therefore also perform the group 1222 member part of IGMPv3, described in Section 5. 1224 A multicast router performs the protocol described in this section 1225 over each of its directly-attached networks. If a multicast router 1226 has more than one interface to the same network, it only needs to 1227 operate this protocol over one of those interfaces. On each 1228 interface over which this protocol is being run, the router MUST 1229 enable reception of multicast address 224.0.0.22, from all sources 1230 (and MUST perform the group member part of IGMPv3 for that address on 1231 that interface). 1233 Multicast routers need to know only that at least one system on an 1234 attached network is interested in packets to a particular multicast 1235 address from a particular source; a multicast router is not required 1236 to keep track of the interests of each individual neighboring system. 1237 (However, see Appendix A.2 point 1 for discussion.) 1239 IGMPv3 is backward compatible with previous versions of the IGMP 1240 protocol. In order to remain backward compatible with older IGMP 1241 systems, IGMPv3 multicast routers MUST also implement versions 1 and 1242 2 of the protocol (see section Section 7). 1244 6.1. Conditions for IGMP Queries 1246 Multicast routers send General Queries periodically to request group 1247 membership information from an attached network. These queries are 1248 used to build and refresh the group membership state of systems on 1249 attached networks. Systems respond to these queries by reporting 1250 their group membership state (and their desired set of sources) with 1251 Current-State Group Records in IGMPv3 Membership Reports. 1253 As a member of a multicast group, a system may express interest in 1254 receiving or not receiving traffic from particular sources. As the 1255 desired reception state of a system changes, it reports these changes 1256 using Filter-Mode-Change Records or Source-List-Change Records. 1257 These records indicate an explicit state change in a group at a 1258 system in either the group record's source list or its filter-mode. 1259 When a group membership is terminated at a system or traffic from a 1260 particular source is no longer desired, a multicast router must query 1261 for other members of the group or listeners of the source before 1262 deleting the group (or source) and pruning its traffic. 1264 To enable all systems on a network to respond to changes in group 1265 membership, multicast routers send specific queries. A Group- 1266 Specific Query is sent to verify there are no systems that desire 1267 reception of the specified group or to "rebuild" the desired 1268 reception state for a particular group. Group-Specific Queries are 1269 sent when a router receives a State-Change record indicating a system 1270 is leaving a group. 1272 A Group-and-Source Specific Query is used to verify there are no 1273 systems on a network which desire to receive traffic from a set of 1274 sources. Group-and-Source Specific Queries list sources for a 1275 particular group which have been requested to no longer be forwarded. 1276 This query is sent by a multicast router to learn if any systems 1277 desire reception of packets to the specified group address from the 1278 specified source addresses. Group-and-Source Specific Queries are 1279 only sent in response to State-Change Records and never in response 1280 to Current-State Records. Section 4.1.11 describes each query in 1281 more detail. 1283 6.2. IGMP State Maintained by Multicast Routers 1285 Multicast routers implementing IGMPv3 keep state per group per 1286 attached network. This group state consists of a filter-mode, a list 1287 of sources, and various timers. For each attached network running 1288 IGMP, a multicast router records the desired reception state for that 1289 network. That state conceptually consists of a set of records of the 1290 form: 1292 (multicast address, group timer, filter-mode, (source records)) 1294 Each source record is of the form: 1296 (source address, source timer) 1298 If all sources within a given group are desired, an empty source 1299 record list is kept with filter-mode set to EXCLUDE. This means 1300 hosts on this network want all sources for this group to be 1301 forwarded. This is the IGMPv3 equivalent to a IGMPv1 or IGMPv2 group 1302 join. 1304 6.2.1. Definition of Router Filter-Mode 1306 To reduce internal state, IGMPv3 routers keep a filter-mode per group 1307 per attached network. This filter-mode is used to condense the total 1308 desired reception state of a group to a minimum set such that all 1309 systems' memberships are satisfied. This filter-mode may change in 1310 response to the reception of particular types of group records or 1311 when certain timer conditions occur. In the following sections, we 1312 use the term "router filter-mode" to refer to the filter-mode of a 1313 particular group within a router. Section 6.4 describes the changes 1314 of a router filter-mode per group record received. 1316 Conceptually, when a group record is received, the router filter-mode 1317 for that group is updated to cover all the requested sources using 1318 the least amount of state. As a rule, once a group record with a 1319 filter-mode of EXCLUDE is received, the router filter-mode for that 1320 group will be EXCLUDE. 1322 When a router filter-mode for a group is EXCLUDE, the source record 1323 list contains two types of sources. The first type is the set which 1324 represents conflicts in the desired reception state; this set must be 1325 forwarded by some router on the network. The second type is the set 1326 of sources which hosts have requested to not be forwarded. 1327 Appendix A describes the reasons for keeping two different sets when 1328 in EXCLUDE mode. 1330 When a router filter-mode for a group is INCLUDE, the source record 1331 list is the list of sources desired for the group. This is the total 1332 desired set of sources for that group. Each source in the source 1333 record list must be forwarded by some router on the network. 1335 Because a reported group record with a filter-mode of EXCLUDE will 1336 cause a router to transition its filter-mode for that group to 1337 EXCLUDE, a mechanism for transitioning a router's filter-mode back to 1338 INCLUDE must exist. If all systems with a group record in EXCLUDE 1339 filter-mode cease reporting, it is desirable for the router filter- 1340 mode for that group to transition back to INCLUDE mode. This 1341 transition occurs when the group timer expires and is explained in 1342 detail in Section 6.5. 1344 6.2.2. Definition of Group Timers 1346 The group timer is only used when a group is in EXCLUDE mode and it 1347 represents the time for the filter-mode of the group to expire and 1348 switch to INCLUDE mode. We define a group timer as a decrementing 1349 timer with a lower bound of zero kept per group per attached network. 1350 Group timers are updated according to the types of group records 1351 received. 1353 A group timer expiring when a router filter-mode for the group is 1354 EXCLUDE means there are no listeners on the attached network in 1355 EXCLUDE mode. At this point, a router will transition to INCLUDE 1356 filter-mode. Section 6.5 describes the actions taken when a group 1357 timer expires while in EXCLUDE mode. 1359 The following table summarizes the role of the group timer. 1360 Section Section 6.4 describes the details of setting the group timer 1361 per type of group record received. 1363 +=============+=======+========================================+ 1364 | Group | Group | Actions/Comments | 1365 | Filter-Mode | Timer | | 1366 | | Value | | 1367 +=============+=======+========================================+ 1368 | INCLUDE | Timer | All members in INCLUDE mode. | 1369 | | >= 0 | | 1370 +-------------+-------+----------------------------------------+ 1371 | EXCLUDE | Timer | At least one member in EXCLUDE mode. | 1372 | | > 0 | | 1373 +-------------+-------+----------------------------------------+ 1374 | EXCLUDE | Timer | No more listeners to group. If all | 1375 | | == 0 | source timers have expired then delete | 1376 | | | Group Record. If there are still | 1377 | | | source record timers running, switch | 1378 | | | to INCLUDE filter-mode using those | 1379 | | | source records with running timers as | 1380 | | | the INCLUDE source record state. | 1381 +-------------+-------+----------------------------------------+ 1383 Table 6 1385 6.2.3. Definition of Source Timers 1387 A source timer is kept per source record and is a decrementing timer 1388 with a lower bound of zero. Source timers are updated according to 1389 the type and filter-mode of the group record received. Source timers 1390 are always updated (for a particular group) whenever the source is 1391 present in a received record for that group. Section 6.4 describes 1392 the setting of source timers per type of group records received. 1394 A source record with a running timer with a router filter-mode for 1395 the group of INCLUDE means that there is currently one or more 1396 systems (in INCLUDE filter-mode) which desire to receive that source. 1397 If a source timer expires with a router filter-mode for the group of 1398 INCLUDE, the router concludes that traffic from this particular 1399 source is no longer desired on the attached network, and deletes the 1400 associated source record. 1402 Source timers are treated differently when a router filter-mode for a 1403 group is EXCLUDE. If a source record has a running timer with a 1404 router filter-mode for the group of EXCLUDE, it means that at least 1405 one system desires the source. It should therefore be forwarded by a 1406 router on the network. Appendix A describes the reasons for keeping 1407 state for sources that have been requested to be forwarded while in 1408 EXCLUDE state. 1410 If a source timer expires with a router filter-mode for the group of 1411 EXCLUDE, the router informs the routing protocol that there is no 1412 longer a receiver on the network interested in traffic from this 1413 source. 1415 When a router filter-mode for a group is EXCLUDE, source records are 1416 only deleted when the group timer expires. Section 6.3 describes the 1417 actions that should be taken dependent upon the value of a source 1418 timer. 1420 6.3. IGMPv3 Source-Specific Forwarding Rules 1422 When a multicast router receives a datagram from a source destined to 1423 a particular group, a decision has to be made whether to forward the 1424 datagram onto an attached network or not. The multicast routing 1425 protocol in use is in charge of this decision, and should use the 1426 IGMPv3 information to ensure that all sources/groups desired on a 1427 subnetwork are forwarded to that subnetwork. IGMPv3 information does 1428 not override multicast routing information; for example, if the 1429 IGMPv3 filter-mode group for G is EXCLUDE, a router may still forward 1430 packets for excluded sources to a transit subnet. 1432 To summarize, the following table describes the forwarding 1433 suggestions made by IGMP to the routing protocol for traffic 1434 originating from a source destined to a group. It also summarizes 1435 the actions taken upon the expiration of a source timer based on the 1436 router filter-mode of the group. 1438 +=============+==========+=======================================+ 1439 | Group | Group | Action | 1440 | Filter-Mode | Timer | | 1441 | | Value | | 1442 +=============+==========+=======================================+ 1443 | INCLUDE | TIMER > | Suggest to forward traffic from | 1444 | | 0 | source | 1445 +-------------+----------+---------------------------------------+ 1446 | INCLUDE | TIMER == | Suggest to stop forwarding traffic | 1447 | | 0 | from source and remove source record. | 1448 | | | If there are no more source records | 1449 | | | for the group, delete group record. | 1450 +-------------+----------+---------------------------------------+ 1451 | INCLUDE | No | Suggest to not forward source | 1452 | | Source | | 1453 | | Elements | | 1454 +-------------+----------+---------------------------------------+ 1455 | EXCLUDE | TIMER > | Suggest to forward traffic from | 1456 | | 0 | source | 1457 +-------------+----------+---------------------------------------+ 1458 | EXCLUDE | TIMER == | Suggest to not forward traffic from | 1459 | | 0 | source (DO NOT remove record) | 1460 +-------------+----------+---------------------------------------+ 1461 | EXCLUDE | No | Suggest to forward traffic from | 1462 | | Source | source | 1463 | | Elements | | 1464 +-------------+----------+---------------------------------------+ 1466 Table 7 1468 6.4. Action on Reception of Reports 1470 SSM-aware routers SHOULD ignore records that contain multicast 1471 addresses in the SSM address range if the record type is 1472 MODE_IS_EXCLUDE or CHANGE_TO_EXCLUDE_MODE. SSM-aware routers SHOULD 1473 ignore IGMPv1/IGMPv2 Report and IGMPv2 DONE messages that contain 1474 multicast addresses in the SSM address range, SHOULD NOT use such 1475 Reports to establish IP forwarding state, and MAY log an error if it 1476 receives such a message. 1478 6.4.1. Reception of Current-State Records 1480 When receiving Current-State Records, a router updates both its group 1481 and source timers. In some circumstances, the reception of a type of 1482 group record will cause the router filter-mode for that group to 1483 change. The table below describes the actions, with respect to state 1484 and timers that occur to a router's state upon reception of Current- 1485 State Records. 1487 The following notation is used to describe the updating of source 1488 timers. The notation ( A, B ) will be used to represent the total 1489 number of sources for a particular group, where 1491 A = set of source records whose source timers > 0 (Sources that at 1492 least one host has requested to be forwarded) 1493 B = set of source records whose source timers = 0 (Sources that IGMP 1494 will suggest to the routing protocol not to forward) 1496 Note that there will only be two sets when a router's filter-mode for 1497 a group is EXCLUDE. When a router's filter-mode for a group is 1498 INCLUDE, a single set is used to describe the set of sources 1499 requested to be forwarded (e.g., simply (A)). 1501 In the following tables, abbreviations are used for several variables 1502 (all of which are described in detail in Section 8). The variable 1503 GMI is an abbreviation for the Group Membership Interval, which is 1504 the time in which group memberships will time out. The variable LMQT 1505 is an abbreviation for the Last Member Query Time, which is the total 1506 time spent after Last Member Query Count retransmissions. LMQT 1507 represents the "leave latency", or the difference between the 1508 transmission of a membership change and the change in the information 1509 given to the routing protocol. 1511 Within the "Actions" section of the router state tables, we use the 1512 notation 'A=J', which means that the set A of source records should 1513 have their source timers set to value J. 'Delete A' means that the 1514 set A of source records should be deleted. 'Group Timer=J' means 1515 that the Group Timer for the group should be set to value J. 1517 Router State Report Rec'd New Router State Actions 1518 ------------ ------------ ---------------- ------- 1520 INCLUDE (A) IS_IN (B) INCLUDE (A+B) (B)=GMI 1522 INCLUDE (A) IS_EX (B) EXCLUDE (A*B,B-A) (B-A)=0 1523 Delete (A-B) 1524 Group Timer=GMI 1526 EXCLUDE (X,Y) IS_IN (A) EXCLUDE (X+A,Y-A) (A)=GMI 1528 EXCLUDE (X,Y) IS_EX (A) EXCLUDE (A-Y,Y*A) (A-X-Y)=GMI 1529 Delete (X-A) 1530 Delete (Y-A) 1531 Group Timer=GMI 1533 6.4.2. Reception of Filter-Mode-Change and Source-List-Change Records 1535 When a change in the global state of a group occurs in a system, the 1536 system sends either a Source-List-Change Record or a Filter-Mode- 1537 Change Record for that group. As with Current-State Records, routers 1538 must act upon these records and possibly change their own state to 1539 reflect the new desired membership state of the network. 1541 Routers must query sources that are requested to be no longer 1542 forwarded to a group. When a router queries or receives a query for 1543 a specific set of sources, it lowers its source timers for those 1544 sources to a small interval of Last Member Query Time seconds. If 1545 group records are received in response to the queries which express 1546 interest in receiving traffic from the queried sources, the 1547 corresponding timers are updated. 1549 Similarly, when a router queries a specific group, it lowers its 1550 group timer for that group to a small interval of Last Member Query 1551 Time seconds. If any group records expressing EXCLUDE mode interest 1552 in the group are received within the interval, the group timer for 1553 the group is updated and the suggestion to the routing protocol to 1554 forward the group stands without any interruption. 1556 During a query period (i.e., Last Member Query Time seconds), the 1557 IGMP component in the router continues to suggest to the routing 1558 protocol that it forwards traffic from the groups or sources that it 1559 is querying. It is not until after Last Member Query Time seconds 1560 without receiving a record expressing interest in the queried group 1561 or sources that the router may prune the group or sources from the 1562 network. 1564 The following table describes the changes in group state and the 1565 action(s) taken when receiving either Filter-Mode-Change or Source- 1566 List-Change Records. This table also describes the queries which are 1567 sent by the querier when a particular report is received. 1569 We use the following notation for describing the queries which are 1570 sent. We use the notation 'Q(G)' to describe a Group-Specific Query 1571 to G. We use the notation 'Q(G,A)' to describe a Group-and-Source 1572 Specific Query to G with source-list A. If source-list A is null as 1573 a result of the action (e.g., A*B) then no query is sent as a result 1574 of the operation. 1576 In order to maintain protocol robustness, queries sent by actions in 1577 the table below need to be transmitted [Last Member Query Count] 1578 times, once every [Last Member Query Interval]. 1580 If while scheduling new queries, there are already pending queries to 1581 be retransmitted for the same group, the new and pending queries have 1582 to be merged. In addition, received host reports for a group with 1583 pending queries may affect the contents of those queries. 1584 Section Section 6.6.3 describes the process of building and 1585 maintaining the state of pending queries. 1587 Router State Report Rec'd New Router State Actions 1588 ------------ ------------ ---------------- ------- 1590 INCLUDE (A) ALLOW (B) INCLUDE (A+B) (B)=GMI 1592 INCLUDE (A) BLOCK (B) INCLUDE (A) Send Q(G,A*B) 1594 INCLUDE (A) TO_EX (B) EXCLUDE (A*B,B-A) (B-A)=0 1595 Delete (A-B) 1596 Send Q(G,A*B) 1597 Group Timer=GMI 1599 INCLUDE (A) TO_IN (B) INCLUDE (A+B) (B)=GMI 1600 Send Q(G,A-B) 1602 EXCLUDE (X,Y) ALLOW (A) EXCLUDE (X+A,Y-A) (A)=GMI 1604 EXCLUDE (X,Y) BLOCK (A) EXCLUDE (X+(A-Y),Y) (A-X-Y)=Group Timer 1605 Send Q(G,A-Y) 1607 EXCLUDE (X,Y) TO_EX (A) EXCLUDE (A-Y,Y*A) (A-X-Y)=Group Timer 1608 Delete (X-A) 1609 Delete (Y-A) 1610 Send Q(G,A-Y) 1611 Group Timer=GMI 1613 EXCLUDE (X,Y) TO_IN (A) EXCLUDE (X+A,Y-A) (A)=GMI 1614 Send Q(G,X-A) 1615 Send Q(G) 1617 6.5. Switching Router Filter-Modes 1619 The group timer is used as a mechanism for transitioning the router 1620 filter-mode from EXCLUDE to INCLUDE. 1622 When a group timer expires with a router filter-mode of EXCLUDE, a 1623 router assumes that there are no systems with a filter-mode of 1624 EXCLUDE present on the attached network. When a router's filter-mode 1625 for a group is EXCLUDE and the group timer expires, the router 1626 filter-mode for the group transitions to INCLUDE. 1628 A router uses source records with running source timers as its state 1629 for the switch to a filter-mode of INCLUDE. If there are any source 1630 records with source timers greater than zero (i.e., requested to be 1631 forwarded), a router switches to filter-mode of INCLUDE using those 1632 source records. Source records whose timers are zero (from the 1633 previous EXCLUDE mode) are deleted. 1635 For example, if a router's state for a group is EXCLUDE(X,Y) and the 1636 group timer expires for that group, the router switches to filter- 1637 mode of INCLUDE with state INCLUDE(X). 1639 6.6. Action on Reception of Queries 1641 6.6.1. Timer Updates 1643 When a router sends or receives a query with a clear Suppress Router- 1644 Side Processing flag, it must update its timers to reflect the 1645 correct timeout values for the group or sources being queried. The 1646 following table describes the timer actions when sending or receiving 1647 a Group-Specific or Group-and-Source Specific Query with the Suppress 1648 Router-Side Processing flag not set. 1650 +========+===================================================+ 1651 | Query | Action | 1652 +========+===================================================+ 1653 | Q(G,A) | Source Timer for sources in A are lowered to LMQT | 1654 +--------+---------------------------------------------------+ 1655 | Q(G) | Group Timer is lowered to LMQT | 1656 +--------+---------------------------------------------------+ 1658 Table 8 1660 When a router sends or receives a query with the Suppress Router-Side 1661 Processing flag set, it will not update its timers. 1663 6.6.2. Querier Election 1665 IGMPv3 elects a single querier per subnet using the same querier 1666 election mechanism as IGMPv2, namely by IP address. When a router 1667 receives a general query with a lower IP address, it sets the Other- 1668 Querier- Present timer to Other Querier Present Interval and ceases 1669 to send general queries on the network if it was the previously 1670 elected querier. After its Other-Querier Present timer expires, it 1671 should begin sending General Queries. 1673 If a router receives an older version general query, it MUST use the 1674 oldest version of IGMP on the network. For a detailed description of 1675 compatibility issues between IGMP versions see section Section 7. 1677 6.6.3. Building and Sending Specific Queries 1679 6.6.3.1. Building and Sending Group Specific Queries 1681 When a table action "Send Q(G)" is encountered, then the group timer 1682 must be lowered to LMQT. The router must then immediately send a 1683 group specific query as well as schedule [Last Member Query Count - 1684 1] query retransmissions to be sent every [Last Member Query 1685 Interval] over [Last Member Query Time]. 1687 When transmitting a group specific query, if the group timer is 1688 larger than LMQT, the "Suppress Router-Side Processing" bit is set in 1689 the query message. 1691 6.6.3.2. Building and Sending Group and Source Specific Queries 1693 When a table action "Send Q(G,X)" is encountered by a querier in the 1694 table in Section 6.4.2, the following actions must be performed for 1695 each of the sources in X of group G, with source timer larger than 1696 LMQT: 1698 * Set number of retransmissions for each source to [Last Member 1699 Query Count]. 1701 * Lower source timer to LMQT. 1703 The router must then immediately send a group and source specific 1704 query as well as schedule [Last Member Query Count - 1] query 1705 retransmissions to be sent every [Last Member Query Interval] over 1706 [Last Member Query Time]. The contents of these queries are 1707 calculated as follows. 1709 When building a group and source specific query for a group G, two 1710 separate query messages are sent for the group. The first one has 1711 the "Suppress Router-Side Processing" bit set and contains all the 1712 sources with retransmission state and timers greater than LMQT. The 1713 second has the "Suppress Router-Side Processing" bit clear and 1714 contains all the sources with retransmission state and timers lower 1715 or equal to LMQT. If either of the two calculated messages does not 1716 contain any sources, then its transmission is suppressed. 1718 Note: If a group specific query is scheduled to be transmitted at the 1719 same time as a group and source specific query for the same group, 1720 then transmission of the group and source specific message with the 1721 "Suppress Router-Side Processing" bit set may be suppressed. 1723 7. Interoperation With Older Versions of IGMP 1725 IGMP version 3 hosts and routers interoperate with hosts and routers 1726 that have not yet been upgraded to IGMPv3. This compatibility is 1727 maintained by hosts and routers taking appropriate actions depending 1728 on the versions of IGMP operating on hosts and routers within a 1729 network. 1731 7.1. Query Version Distinctions 1733 The IGMP version of a Membership Query message is determined as 1734 follows: 1736 IGMPv1 Query: length = 8 octets AND Max Resp Code field is zero 1738 IGMPv2 Query: length = 8 octets AND Max Resp Code field is non- 1739 zero 1741 IGMPv3 Query: length >= 12 octets 1743 Query messages that do not match any of the above conditions (e.g., a 1744 Query of length 10 octets) MUST be silently ignored. 1746 7.2. Group Member Behavior 1748 7.2.1. In the Presence of Older Version Queriers 1750 In order to be compatible with older version routers, IGMPv3 hosts 1751 MUST operate in version 1 and version 2 compatibility modes. IGMPv3 1752 hosts MUST keep state per local interface regarding the compatibility 1753 mode of each attached network. A host's compatibility mode is 1754 determined from the Host Compatibility Mode variable which can be in 1755 one of three states: IGMPv1, IGMPv2 or IGMPv3. This variable is kept 1756 per interface and is dependent on the version of General Queries 1757 heard on that interface as well as the Older Version Querier Present 1758 timers for the interface. 1760 In order to switch gracefully between versions of IGMP, hosts keep 1761 both an IGMPv1 Querier Present timer and an IGMPv2 Querier Present 1762 timer per interface. IGMPv1 Querier Present is set to Older Version 1763 Querier Present Timeout seconds whenever an IGMPv1 Membership Query 1764 is received. IGMPv2 Querier Present is set to Older Version Querier 1765 Present Timeout seconds whenever an IGMPv2 General Query is received. 19.nit: s/Present Timeout/Present Interval/ 1767 The Host Compatibility Mode of an interface changes whenever an older 1768 version query (than the current compatibility mode) is heard or when 1769 certain timer conditions occur. When the IGMPv1 Querier Present 1770 timer expires, a host switches to Host Compatibility mode of IGMPv2 1771 if it has a running IGMPv2 Querier Present timer. If it does not 1772 have a running IGMPv2 Querier Present timer then it switches to Host 1773 Compatibility of IGMPv3. When the IGMPv2 Querier Present timer 1774 expires, a host switches to Host Compatibility mode of IGMPv3. 1776 The Host Compatibility Mode variable is based on whether an older 1777 version General query was heard in the last Older Version Querier 1778 Present Timeout seconds. The Host Compatibility Mode is set 20.nit: s/Present Timeout/Present Interval/ 1779 depending on the following: 1781 +=========================+========================================+ 1782 | Host Compatibility Mode | Timer State | 1783 +=========================+========================================+ 1784 | IGMPv3 (default) | IGMPv2 Querier Present not running and | 1785 | | IGMPv1 Querier Present not running | 1786 +-------------------------+----------------------------------------+ 1787 | IGMPv2 | IGMPv2 Querier Present running and | 1788 | | IGMPv1 Querier Present not running | 1789 +-------------------------+----------------------------------------+ 1790 | IGMPv1 | IGMPv1 Querier Present running | 1791 +-------------------------+----------------------------------------+ 1793 Table 9 1795 If a host receives a query which causes its Querier Present timers to 1796 be updated and correspondingly its compatibility mode, it should 1797 switch compatibility modes immediately. 1799 When Host Compatibility Mode is IGMPv3, a host acts using the IGMPv3 1800 protocol on that interface. When Host Compatibility Mode is IGMPv2, 1801 a host acts in IGMPv2 compatibility mode, using only the IGMPv2 1802 protocol, on that interface. When Host Compatibility Mode is IGMPv1, 1803 a host acts in IGMPv1 compatibility mode, using only the IGMPv1 1804 protocol on that interface. 1806 An IGMPv1 router will send General Queries with the Max Resp Code set 1807 to 0. This MUST be interpreted as a value of 100 (10 seconds). 1809 An IGMPv2 router will send General Queries with the Max Resp Code set 1810 to the desired Max Resp Time, i.e., the full range of this field is 1811 linear and the exponential algorithm described in Section 4.1.1 is 1812 not used. 1814 Whenever a host changes its compatibility mode, it cancels all its 1815 pending response and retransmission timers. 1817 An SSM-aware host that receives an IGMPv1 Query, an IGMPv2 General 1818 Query, or an IGMPv2 Group Specific Query for a multicast address in 1819 the SSM range SHOULD log an error. 1821 7.2.2. In the Presence of Older Version Group Members 1823 An IGMPv3 host may be placed on a network where there are hosts that 1824 have not yet been upgraded to IGMPv3. A host MAY allow its IGMPv3 1825 Membership Record to be suppressed by either a Version 1 Membership 1826 Report, or a Version 2 Membership Report. SSM-aware hosts MUST NOT 1827 allow its IGMPv3 Membership Record to be suppressed. 21.mayor: The last sentence looks like being copied from RFC4604. But it does not copy the explanation sentence from RFC4604: Suppressing reports in this scenario would provide an avenue for an attacker to deny SSM service to other hosts on the link. The correct requirement just to protect SSM would be: SSM-aware hosts MUST NOT allow their IGMPv3 Membership Records for groups in the SSM address tange to be suppressed. Suppressing such records would make SSM fail in the presence of older hosts, malicious or not. BUT: I would love to change the whole paragraph to be changed to: An IGMPv3 host may be placed on a network where there are hosts that have not yet been upgraded to IGMPv3. A host MUST NOT allow its IGMPv3 Membership Records to be suppressed by either a Version 1 Membership Report, or a Version 2 Membership Report. See A.2 for explanations. Aka: There is IMHO no reason whatsoever to ever think about report suppression. The only reason for report suppression where shared (non-switched) LANs or todays equivalent, ad-hoc WiFi (AP-mode is like a switch), but it absolutely does make no sense whatsoever to only have a MAY for such scenarios in the presence of older hosts. 1829 7.3. Multicast Router Behavior 1831 7.3.1. In the Presence of Older Version Queriers 1833 IGMPv3 routers may be placed on a network where at least one router 1834 on the network has not yet been upgraded to IGMPv3. The following 1835 requirements apply: 1837 * If any older versions of IGMP are present on routers, the querier 1838 MUST use the lowest version of IGMP present on the network. This 1839 must be administratively assured; routers that desire to be 1840 compatible with IGMPv1 and IGMPv2 MUST have a configuration option 1841 to act in IGMPv1 or IGMPv2 compatibility modes. When in IGMPv1 1842 mode, routers MUST send Periodic Queries with a Max Resp Code of 0 1843 and truncated at the Group Address field (i.e., 8 bytes long), and 1844 MUST ignore Leave Group messages. They SHOULD also warn about 1845 receiving an IGMPv2 or IGMPv3 query, although such warnings MUST 1846 be rate-limited. When in IGMPv2 mode, routers MUST send Periodic 1847 Queries truncated at the Group Address field (i.e., 8 bytes long), 1848 and SHOULD also warn about receiving an IGMPv3 query (such 1849 warnings MUST be rate-limited). They also MUST fill in the Max 1850 Resp Time in the Max Resp Code field, i.e., the exponential 1851 algorithm described in Section 4.1.1 is not used. 1853 * If a router is not explicitly configured to use IGMPv1 or IGMPv2 1854 and hears an IGMPv1 Query or IGMPv2 General Query, it SHOULD log a 1855 warning. These warnings MUST be rate-limited. 1857 7.3.2. In the Presence of Older Version Group Members 1859 IGMPv3 routers may be placed on a network where there are hosts that 1860 have not yet been upgraded to IGMPv3. In order to be compatible with 1861 older version hosts, IGMPv3 routers MUST operate in version 1 and 1862 version 2 compatibility modes. IGMPv3 routers keep a compatibility 1863 mode per group record. A group's compatibility mode is determined 1864 from the Group Compatibility Mode variable which can be in one of 1865 three states: IGMPv1, IGMPv2 or IGMPv3. This variable is kept per 1866 group record and is dependent on the version of Membership Reports 1867 heard for that group as well as the Older Version Host Present timer 1868 for the group. 1870 In order to switch gracefully between versions of IGMP, routers keep 1871 an IGMPv1 Host Present timer and an IGMPv2 Host Present timer per 1872 group record. The IGMPv1 Host Present timer is set to Older Version 1873 Host Present Timeout seconds whenever an IGMPv1 Membership Report is 1874 received. The IGMPv2 Host Present timer is set to Older Version Host 1875 Present Timeout seconds whenever an IGMPv2 Membership Report is 1876 received. 1878 The Group Compatibility Mode of a group record changes whenever an 1879 older version report (than the current compatibility mode) is heard 1880 or when certain timer conditions occur. When the IGMPv1 Host Present 1881 timer expires, a router switches to Group Compatibility mode of 1882 IGMPv2 if it has a running IGMPv2 Host Present timer. If it does not 1883 have a running IGMPv2 Host Present timer then it switches to Group 1884 Compatibility of IGMPv3. When the IGMPv2 Host Present timer expires 1885 and the IGMPv1 Host Present timer is not running, a router switches 1886 to Group Compatibility mode of IGMPv3. Note that when a group 1887 switches back to IGMPv3 mode, it takes some time to regain source- 1888 specific state information. Source-specific information will be 1889 learned during the next General Query, but sources that should be 1890 blocked will not be blocked until [Group Membership Interval] after 1891 that. 1893 The Group Compatibility Mode variable is based on whether an older 1894 version report was heard in the last Older Version Host Present 1895 Timeout seconds. The Group Compatibility Mode is set depending on 1896 the following: 1898 +==========================+=====================================+ 1899 | Group Compatibility Mode | Timer State | 1900 +==========================+=====================================+ 1901 | IGMPv3 (default) | IGMPv2 Host Present not running and | 1902 | | IGMPv1 Host Present not running | 1903 +--------------------------+-------------------------------------+ 1904 | IGMPv2 | IGMPv2 Host Present running and | 1905 | | IGMPv1 Host Present not running | 1906 +--------------------------+-------------------------------------+ 1907 | IGMPv1 | IGMPv1 Host Present running | 1908 +--------------------------+-------------------------------------+ 1910 Table 10 1912 If a router receives a report which causes its older Host Present 1913 timers to be updated and correspondingly its compatibility mode, it 1914 SHOULD switch compatibility modes immediately. 1916 When Group Compatibility Mode is IGMPv3, a router acts using the 1917 IGMPv3 protocol for that group. 1919 When Group Compatibility Mode is IGMPv2, a router internally 1920 translates the following IGMPv2 messages for that group to their 1921 IGMPv3 equivalents: 1923 +================+===================+ 1924 | IGMPv2 Message | IGMPv3 Equivalent | 1925 +================+===================+ 1926 | Report | IS_EX( {} ) | 1927 +----------------+-------------------+ 1928 | Leave | TO_IN( {} ) | 1929 +----------------+-------------------+ 1931 Table 11 1933 IGMPv3 BLOCK messages are ignored, as are source-lists in TO_EX() 1934 messages (i.e., any TO_EX() message is treated as TO_EX( {} )). 1936 When Group Compatibility Mode is IGMPv1, a router internally 1937 translates the following IGMPv1 and IGMPv2 messages for that group to 1938 their IGMPv3 equivalents: 1940 +================+===================+ 1941 | IGMPv2 Message | IGMPv3 Equivalent | 1942 +================+===================+ 1943 | v1 Report | IS_EX( {} ) | 1944 +----------------+-------------------+ 1945 | v2 Report | IS_EX( {} ) | 1946 +----------------+-------------------+ 1948 Table 12 1950 In addition to ignoring IGMPv3 BLOCK messages and source-lists in 1951 TO_EX() messages as in IGMPv2 Group Compatibility Mode, IGMPv2 Leave 1952 messages and IGMPv3 TO_IN() messages are also ignored. 1954 8. List of Timers, Counters and Their Default Values 1956 Most of these timers are configurable. If non-default settings are 1957 used, they MUST be consistent among all systems on a single link. 1958 Note that parentheses are used to group expressions to make the 1959 algebra clear. 1961 8.1. Robustness Variable 1963 The Robustness Variable allows tuning for the expected packet loss on 1964 a network. If a network is expected to be lossy, the Robustness 1965 Variable may be increased. IGMP is robust to (Robustness Variable - 1966 1) packet losses. The Robustness Variable MUST NOT be zero, and 1967 SHOULD NOT be one. Default: 2 1969 8.2. Query Interval 1971 The Query Interval is the interval between General Queries sent by 1972 the Querier. Default: 125 seconds. 1974 By varying the [Query Interval], an administrator may tune the number 1975 of IGMP messages on the network; larger values cause IGMP Queries to 1976 be sent less often. 1978 8.3. Query Response Interval 1980 The Max Response Time used to calculate the Max Resp Code inserted 1981 into the periodic General Queries. Default: 100 (10 seconds) 1983 By varying the [Query Response Interval], an administrator may tune 1984 the burstiness of IGMP messages on the network; larger values make 1985 the traffic less bursty, as host responses are spread out over a 1986 larger interval. The number of seconds represented by the [Query 1987 Response Interval] must be less than the [Query Interval]. 1989 8.4. Group Membership Interval 1991 The Group Membership Interval is the amount of time that must pass 1992 before a multicast router decides there are no more members of a 1993 group or a particular source on a network. 1995 This value MUST be ((the Robustness Variable) times (the Query 1996 Interval)) plus (2 * Query Response Interval). 1998 8.5. Other Querier Present Interval 2000 The Other Querier Present Interval is the length of time that must 2001 pass before a multicast router decides that there is no longer 2002 another multicast router which should be the querier. This value 2003 MUST be ((the Robustness Variable) times (the Query Interval)) plus 2004 (one half of one Query Response Interval). 2006 8.6. Startup Query Interval 2008 The Startup Query Interval is the interval between General Queries 2009 sent by a Querier on startup. Default: 1/4 the Query Interval. 2011 8.7. Startup Query Count 2013 The Startup Query Count is the number of Queries sent out on startup, 2014 separated by the Startup Query Interval. Default: the Robustness 2015 Variable. 2017 8.8. Last Member Query Interval 2019 The Last Member Query Interval is the Max Response Time used to 2020 calculate the Max Resp Code inserted into Group-Specific Queries sent 2021 in response to Leave Group messages. It is also the Max Response 2022 Time used in calculating the Max Resp Code for Group-and-Source- 2023 Specific Query messages. Default: 10 (1 second) 2025 Note that for values of LMQI greater than 12.8 seconds, a limited set 2026 of values can be represented, corresponding to sequential values of 2027 Max Resp Code. When converting a configured time to a Max Resp Code 2028 value, it is recommended to use the exact value if possible, or the 2029 next lower value if the requested value is not exactly representable. 2031 This value may be tuned to modify the "leave latency" of the network. 2032 A reduced value results in reduced time to detect the loss of the 2033 last member of a group or source. 2035 8.9. Last Member Query Count 2037 The Last Member Query Count is the number of Group-Specific Queries 2038 sent before the router assumes there are no local members. The Last 2039 Member Query Count is also the number of Group-and-Source-Specific 2040 Queries sent before the router assumes there are no listeners for a 2041 particular source. Default: the Robustness Variable. 2043 8.10. Last Member Query Time 2045 The Last Member Query Time is the time value represented by the Last 2046 Member Query Interval, multiplied by the Last Member Query Count. It 2047 is not a tunable value, but may be tuned by changing its components. 2049 8.11. Unsolicited Report Interval 2051 The Unsolicited Report Interval is the time between repetitions of a 2052 host's initial report of membership in a group. Default: 1 second. 2054 8.12. Older Version Querier Present Interval 22.minor: Googling the Internet, it seems as if some CLI have used OVQPT to refer to the rfc3376 name "Older Version Querier Present Timeout", which you renamed to "Older Version Querier Present Interval", probably because 8.12 in rfc3376 also uses the term "Older Version Querier Interval" as a synonym for "Older Version Querier Present Interval" - to confuse the heck out of everybody. Anyhow. To put a better stake into the ground, i would suggest to change title to: Older Version Querier Present Interval (OVQPI) aka: seed the abbreviation to the right term. 2056 The Older Version Querier Present Interval is the timeout for 23.nit: And/or add (OVQPI) on the above line 2057 transitioning a host back to IGMPv3 mode once an older version query 2058 is heard. When an older version query is received, hosts set their 2059 Older Version Querier Present Timer to Older Version Querier Present 2060 Interval. 24.nit: And put (OVQPT) behind the term, so that any CLI that wants to use abbreviation has a normative one. This may annoy the CLI i found on google which used OVQPT for the Timeout, but obviously, we can not have OVQPT to describe both a timeout and a timer, so there is no way to make those folks happy. 2062 It is RECOMMENDED to use the default values for calculating the 2063 interval value as hosts do not know the values configured on the 2064 querying routers. This value SHOULD be [Robustness Variable] times 25.nit: ... quering routers, because QQIC is not present in version 1 or version 2 queries. Just a suggestion for readers to more easily understand the problem. 2065 [Query Interval] plus (10 times the Max Resp Time in the last 2066 received query message). 26.nit: A short rationale for the magical value 10 would be nice. 2068 8.13. Older Host Present Interval 2070 The Older Host Present Interval is the time-out for transitioning a 2071 group back to IGMPv3 mode once an older version report is sent for 2072 that group. When an older version report is received, routers set 2073 their Older Host Present Timer to Older Host Present Interval. 2075 This value MUST be ((the Robustness Variable) times (the Query 2076 Interval)) plus (one Query Response Interval). 2078 8.14. Configuring Timers 2080 This section is meant to provide advice to network administrators on 2081 how to tune these settings to their network. Ambitious router 2082 implementations might tune these settings dynamically based upon 2083 changing characteristics of the network. 2085 8.14.1. Robustness Variable 2087 The Robustness Variable tunes IGMP to expected losses on a link. 2088 IGMPv3 is robust to (Robustness Variable - 1) packet losses, e.g., if 2089 the Robustness Variable is set to the default value of 2, IGMPv3 is 2090 robust to a single packet loss but may operate imperfectly if more 2091 losses occur. On lossy subnetworks, the Robustness Variable should 2092 be increased to allow for the expected level of packet loss. 2093 However, increasing the Robustness Variable increases the leave 2094 latency of the subnetwork. (The leave latency is the time between 2095 when the last member stops listening to a source or group and when 2096 the traffic stops flowing.) 2098 8.14.2. Query Interval 2100 The overall level of periodic IGMP traffic is inversely proportional 2101 to the Query Interval. A longer Query Interval results in a lower 2102 overall level of IGMP traffic. The Query Interval MUST be equal to 2103 or longer than the Max Response Time inserted in General Query 2104 messages. 2106 8.14.3. Max Response Time 2108 The burstiness of IGMP traffic is inversely proportional to the Max 2109 Response Time. A longer Max Response Time will spread Report 2110 messages over a longer interval. However, a longer Max Response Time 2111 in Group-Specific and Source-and-Group-Specific Queries extends the 2112 leave latency. (The leave latency is the time between when the last 2113 member stops listening to a source or group and when the traffic 2114 stops flowing.) The expected rate of Report messages can be 2115 calculated by dividing the expected number of Reporters by the Max 2116 Response Time. The Max Response Time may be dynamically calculated 2117 per Query by using the expected number of Reporters for that Query as 2118 follows: 2120 +===========================+===============================+ 2121 | Query Type | Expected number of Reporters | 2122 +===========================+===============================+ 2123 | General Query | All systems on subnetwork | 2124 +---------------------------+-------------------------------+ 2125 | Group-Specific Query | All systems that had | 2126 | | expressed interest in the | 2127 | | group on the subnetwork | 2128 +---------------------------+-------------------------------+ 2129 | Source-and-Group-Specific | All systems on the subnetwork | 2130 | Query | that had expressed interest | 2131 | | in the source and group | 2132 +---------------------------+-------------------------------+ 2134 Table 13 2136 A router is not required to calculate these populations or tune the 2137 Max Response Time dynamically; these are simply guidelines. 2139 9. Security Considerations 2141 We consider the ramifications of a forged message of each type, and 2142 describe the usage of IPSEC AH to authenticate messages if desired. 2144 9.1. Query Message 2146 A forged Query message from a machine with a lower IP address than 2147 the current Querier will cause Querier duties to be assigned to the 2148 forger. If the forger then sends no more Query messages, other 2149 routers' Other Querier Present timer will time out and one will 2150 resume the role of Querier. During this time, if the forger ignores 2151 Leave Messages, traffic might flow to groups with no members for up 2152 to [Group Membership Interval]. 2154 A DoS attack on a host could be staged through forged Group-and- 2155 Source-Specific Queries. The attacker can find out about membership 2156 of a specific host with a general query. After that it could send a 2157 large number of Group-and-Source-Specific queries, each with a large 2158 source list and the Maximum Response Time set to a large value. The 2159 host will have to store and maintain the sources specified in all of 2160 those queries for as long as it takes to send the delayed response. 2161 This would consume both memory and CPU cycles in order to augment the 2162 recorded sources with the source lists included in the successive 2163 queries. 2165 To protect against such a DoS attack, a host stack implementation 2166 could restrict the number of Group-and-Source-Specific Queries per 2167 group membership within this interval, and/or record only a limited 2168 number of sources. 2170 Forged Query messages from the local network can be easily traced. 2171 There are three measures necessary to defend against externally 2172 forged Queries: 2174 * Routers SHOULD NOT forward Queries. This is easier for a router 2175 to accomplish if the Query carries the Router-Alert option. 2177 * Hosts SHOULD ignore v2 or v3 Queries without the Router-Alert 2178 option. 2180 * Hosts SHOULD ignore v1, v2 or v3 General Queries sent to a 2181 multicast address other than 224.0.0.1, the all-systems address. 2183 9.2. Current-State Report messages 2185 A forged Report message may cause multicast routers to think there 2186 are members of a group on a network when there are not. Forged 2187 Report messages from the local network are meaningless, since joining 2188 a group on a host is generally an unprivileged operation, so a local 2189 user may trivially gain the same result without forging any messages. 2190 Forged Report messages from external sources are more troublesome; 2191 there are two defenses against externally forged Reports: 2193 * Ignore the Report if you cannot identify the source address of the 2194 packet as belonging to a network assigned to the interface on 2195 which the packet was received. This solution means that Reports 2196 sent by mobile hosts without addresses on the local network will 2197 be ignored. Report messages with a source address of 0.0.0.0 2198 SHOULD be accepted on any interface. 2200 * Ignore Report messages without Router Alert options [RFC2113], and 2201 require that routers not forward Report messages. (The 2202 requirement is not a requirement of generalized filtering in the 2203 forwarding path, since the packets already have Router Alert 2204 options in them.) This solution breaks backwards compatibility 2205 with implementations of IGMPv1 or earlier versions of IGMPv2 which 2206 did not require Router Alert. 2208 A forged Version 1 Report Message may put a router into "version 1 2209 members present" state for a particular group, meaning that the 2210 router will ignore Leave messages. This can cause traffic to flow to 2211 groups with no members for up to [Group Membership Interval]. This 2212 can be solved by providing routers with a configuration switch to 2213 ignore Version 1 messages completely. This breaks automatic 2214 compatibility with Version 1 hosts, so should only be used in 2215 situations where "fast leave" is critical. 2217 A forged Version 2 Report Message may put a router into "version 2 2218 members present" state for a particular group, meaning that the 2219 router will ignore IGMPv3 source-specific state messages. This can 2220 cause traffic to flow from unwanted sources for up to [Group 2221 Membership Interval]. This can be solved by providing routers with a 2222 configuration switch to ignore Version 2 messages completely. This 2223 breaks automatic compatibility with Version 2 hosts, so should only 2224 be used in situations where source include and exclude is critical. 2226 9.3. State-Change Report Messages 2228 A forged State-Change Report message will cause the Querier to send 2229 out Group-Specific or Source-and-Group-Specific Queries for the group 2230 in question. This causes extra processing on each router and on each 2231 member of the group, but can not cause loss of desired traffic. 2232 There are two defenses against externally forged State-Change Report 2233 messages: 2235 * Ignore the State-Change Report message if you cannot identify the 2236 source address of the packet as belonging to a subnet assigned to 2237 the interface on which the packet was received. This solution 2238 means that State-Change Report messages sent by mobile hosts 2239 without addresses on the local subnet will be ignored. State- 2240 Change Report messages with a source address of 0.0.0.0 SHOULD be 2241 accepted on any interface. 2243 * Ignore State-Change Report messages without Router Alert options 2244 [RFC2113], and require that routers not forward State-Change 2245 Report messages. (The requirement is not a requirement of 2246 generalized filtering in the forwarding path, since the packets 2247 already have Router Alert options in them.) 2249 9.4. 9.4. IPSEC Usage 2251 In addition to these measures, IPSEC in Authentication Header mode 2252 [RFC2402] may be used to protect against remote attacks by ensuring 2253 that IGMPv3 messages came from a system on the LAN (or, more 2254 specifically, a system with the proper key). When using IPSEC, the 2255 messages sent to 224.0.0.1 and 224.0.0.22 should be authenticated 2256 using AH. When keying, there are two possibilities: 2258 1. Use a symmetric signature algorithm with a single key for the LAN 2259 (or a key for each group). This allows validation that a packet 2260 was sent by a system with the key. This has the limitation that 2261 any system with the key can forge a message; it is not possible 2262 to authenticate the individual sender precisely. It also 2263 requires disabling IPSec's Replay Protection. 2265 2. When appropriate key management standards have been developed, 2266 use an asymmetric signature algorithm. All systems need to know 2267 the public key of all routers, and all routers need to know the 2268 public key of all systems. This requires a large amount of key 2269 management but has the advantage that senders can be 2270 authenticated individually so e.g., a host cannot forge a message 2271 that only routers should be allowed to send. 2273 This solution only directly applies to Query and Leave messages in 2274 IGMPv1 and IGMPv2, since Reports are sent to the group being reported 2275 and it is not feasible to agree on a key for host-to-router 2276 communication for arbitrary multicast groups. 2278 10. IANA Considerations 2280 All IGMP types described in this document are managed via 2281 [I-D.ietf-pim-3228bis]. 27.minor: I think we need to add the following text: IANA is asked to update the registration for the IGMP messages type as shown in Table 1 to refer to [ThisRFC] instead of [RFC3376]. 2283 11. Contributors 2285 Brad Cain, Steve Deering, Isidor Kouvelas, Bill Fenner, and Ajit 2286 Thyagarajan are the authors of RFC 3376, which forms the bulk of the 2287 content contained herein. 2289 Anuj Budhiraja, Toerless Eckert, Olufemi Komolafe and Tim Winters 2290 have contributed valuable content to this version of the 2291 specification. 2293 12. Acknowledgments 2295 We would like to thank Ran Atkinson, Luis Costa, Toerless Eckert, 2296 Dino Farinacci, Serge Fdida, Wilbert de Graaf, Sumit Gupta, Mark 2297 Handley, Bob Quinn, Michael Speer, Dave Thaler and Rolland Vida for 2298 comments and suggestions on RFC 3376. 2300 Stig Venaas, Hitoshi Asaeda, and Mike McBride have provided valuable 2301 feedback on this version of the specification and we thank them for 2302 their input. 2304 13. References 2306 13.1. Normative References 2308 [RFC1112] Deering, S., "Host extensions for IP multicasting", STD 5, 2309 RFC 1112, DOI 10.17487/RFC1112, August 1989, 2310 <https://www.rfc-editor.org/info/rfc1112>. 2312 [RFC2113] Katz, D., "IP Router Alert Option", RFC 2113, 2313 DOI 10.17487/RFC2113, February 1997, 2314 <https://www.rfc-editor.org/info/rfc2113>. 2316 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2317 Requirement Levels", BCP 14, RFC 2119, 2318 DOI 10.17487/RFC2119, March 1997, 2319 <https://www.rfc-editor.org/info/rfc2119>. 2321 [RFC2236] Fenner, W., "Internet Group Management Protocol, Version 2322 2", RFC 2236, DOI 10.17487/RFC2236, November 1997, 2323 <https://www.rfc-editor.org/info/rfc2236>. 2325 [RFC2402] Kent, S. and R. Atkinson, "IP Authentication Header", 2326 RFC 2402, DOI 10.17487/RFC2402, November 1998, 2327 <https://www.rfc-editor.org/info/rfc2402>. 2329 [RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for 2330 IP", RFC 4607, DOI 10.17487/RFC4607, August 2006, 2331 <https://www.rfc-editor.org/info/rfc4607>. 2333 13.2. Informative References 2335 [I-D.ietf-pim-3228bis] 2336 Haberman, B., "IANA Considerations for Internet Group 2337 Management Protocols", Work in Progress, Internet-Draft, 2338 draft-ietf-pim-3228bis-02, 23 October 2023, 2339 <https://datatracker.ietf.org/doc/html/draft-ietf-pim- 2340 3228bis-02>. 2342 [RFC1071] Braden, R., Borman, D., and C. Partridge, "Computing the 2343 Internet checksum", RFC 1071, DOI 10.17487/RFC1071, 2344 September 1988, <https://www.rfc-editor.org/info/rfc1071>. 2346 [RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A. 2347 Thyagarajan, "Internet Group Management Protocol, Version 2348 3", RFC 3376, DOI 10.17487/RFC3376, October 2002, 2349 <https://www.rfc-editor.org/info/rfc3376>. 2351 [RFC3569] Bhattacharyya, S., Ed., "An Overview of Source-Specific 2352 Multicast (SSM)", RFC 3569, DOI 10.17487/RFC3569, July 2353 2003, <https://www.rfc-editor.org/info/rfc3569>. 2355 [RFC3678] Thaler, D., Fenner, B., and B. Quinn, "Socket Interface 2356 Extensions for Multicast Source Filters", RFC 3678, 2357 DOI 10.17487/RFC3678, January 2004, 2358 <https://www.rfc-editor.org/info/rfc3678>. 2360 Appendix A. Design Rationale 2362 A.1. The Need for State-Change Messages 2364 IGMPv3 specifies two types of Membership Reports: Current-State and 2365 State Change. This section describes the rationale for the need for 2366 both these types of Reports. 2368 Routers need to distinguish Membership Reports that were sent in 2369 response to Queries from those that were sent as a result of a change 2370 in interface state. Membership reports that are sent in response to 2371 Membership Queries are used mainly to refresh the existing state at 2372 the router; they typically do not cause transitions in state at the 2373 router. Membership Reports that are sent in response to changes in 2374 interface state require the router to take some action in response to 2375 the received report (see Section 6.4). 2377 The inability to distinguish between the two types of reports would 2378 force a router to treat all Membership Reports as potential changes 2379 in state and could result in increased processing at the router as 2380 well as an increase in IGMP traffic on the network. 2382 A.2. Host Suppression 2384 In IGMPv1 and IGMPv2, a host would cancel sending a pending 2385 membership reports if a similar report was observed from another 2386 member on the network. In IGMPv3, this suppression of host 2387 membership reports has been removed. The following points explain 2388 the reasons behind this decision. 2390 1. Routers may want to track per-host membership status on an 2391 interface. This allows routers to implement fast leaves (e.g., 2392 for layered multicast congestion control schemes) as well as 2393 track membership status for possible accounting purposes. 28.minor: Could we add the following at the end, please: See [draft-ietf-pim-explicit-tracking] for details on such procedures. Yes, we did let that draft expire and that pains me, and we should get back to it, but i think that it deserves mentioning especially given how there are existing explicit tracking implementations in widely deployed products. 2395 2. Membership Report suppression does not work well on bridged LANs. 2396 Many bridges and Layer2/Layer3 switches that implement IGMP 2397 snooping do not forward IGMP messages across LAN segments in 2398 order to prevent membership report suppression. Removing 2399 membership report suppression eases the job of these IGMP 2400 snooping devices. 2402 3. By eliminating membership report suppression, hosts have fewer 2403 messages to process; this leads to a simpler state machine 2404 implementation. 2406 4. In IGMPv3, a single membership report now bundles multiple 2407 multicast group records to decrease the number of packets sent. 2408 In comparison, the previous versions of IGMP required that each 2409 multicast group be reported in a separate message. 2411 A.3. Switching Router Filter Modes from EXCLUDE to INCLUDE 2413 If there exist hosts in both EXCLUDE and INCLUDE modes for a single 2414 multicast group in a network, the router must be in EXCLUDE mode as 2415 well (see section 6.2.1). In EXCLUDE mode, a router forwards traffic 2416 from all sources unless that source exists in the exclusion source 2417 list. If all hosts in EXCLUDE mode cease to exist, it would be 2418 desirable for the router to switch back to INCLUDE mode seamlessly 2419 without interrupting the flow of traffic to existing receivers. 2421 One of the ways to accomplish this is for routers to keep track of 2422 all sources desired by hosts that are in INCLUDE mode even though the 2423 router itself is in EXCLUDE mode. If the group timer now expires in 2424 EXCLUDE mode, it implies that there are no hosts in EXCLUDE mode on 2425 the network (otherwise a membership report from that host would have 2426 refreshed the group timer). The router can then switch to INCLUDE 2427 mode seamlessly with the list of sources currently being forwarded in 2428 its source list. 2430 Appendix B. Summary of Changes from IGMPv2 2432 While the main additional feature of IGMPv3 is the addition of source 2433 filtering, the following is a summary of other changes from RFC 2236. 2435 * State is maintained as Group + List-of-Sources, not simply Group 2436 as in IGMPv2. 2438 * Interoperability with IGMPv1 and IGMPv2 systems is defined as 2439 operations on the IGMPv3 state. 2441 * The IP Service Interface has changed to allow specification of 2442 source-lists. 2444 * The Querier includes its Robustness Variable and Query Interval in 2445 Query packets to allow synchronization of these variables on non- 2446 Queriers. 2448 * The Max Response Time in Query messages has an exponential range, 2449 changing the maximum from 25.5 seconds to about 53 minutes, for 2450 use on links with huge numbers of systems. 2452 * Hosts retransmit state-change messages for increased robustness. 2454 * Additional data sections are defined to allow later extensions. 2456 * Report packets are sent to 224.0.0.22, to assist layer-2 switches 2457 in snooping. 2459 * Report packets can contain multiple group records, to allow 2460 reporting of full current state using fewer packets. 2462 * Hosts no longer perform suppression, to simplify implementations 2463 and permit explicit membership tracking. 2465 * New Suppress Router-Side Processing (S) flag in Query messages 2466 fixes robustness issues which were also present in IGMPv2. 2468 Appendix C. Summary of Changes from RFC 3376 2470 The following is a list of changes made since RFC 3376. 2472 * Modified definition of Older Version Querier Present Interval to 2473 address Erratum 4375. 2475 * Modified metadata to fix Obsoletes vs Updates relationship with 2476 RFC 2236 per Erratum 1501. 2478 * Updated Group Membership Interval definition to address Erratum 2479 6725. 2481 * Updated text for Router Filter-Mode to address Erratum 5562. 29.minor: I could actually not find any text changes for this. There seem to be none functionally relevant in the sections mentioned in thre erratum. Could you add some pointer to the section(s) with changes because of this erratum here please ? 2483 * Clarified the use of General Queries in the Querier election 2484 process. 30.minor: Please add: * Inherited and rephrased core requirements text from RFC4604 for SSM-aware systems. * Changed ambiguous naming "Older Version Querier Present Interval" / "Older Version Querier Interval" to "Older Version Querier Present Interval" (OVQPI). Removed Term "Older Version Querier Present Timeout", because its abbreviation would clash with the necessary "Older Version Querier Present Timer" (OVQPT). * Changed a MAY for host record report suppression in the presence of older hosts to a MUST NOT to better protect good IGMPv3 behavior in the presence of older hosts. That previous line of course only if/when the suggested change by me is used. * Improved formatting and copyright statement. 31.minor: Appendix D. Summary of Updates to RFC4604 * For ease readability and completeness of this specification, it inherits the core requirements of RFC4604 for the IGMPv3 protocol behavior. No changes in requirements over RFC4604 are intended. RFC4604 also specifies additional behavior for IGMPv1/IGMPv2 backward compatibility behavior for SSM groups not covered in this document as well as configuration options. I hope this is correct and explans the situation sufficiently. 2486 Author's Address 2488 Brian Haberman (editor) 2489 Johns Hopkins University Applied Physics Lab 2490 Email: brian@innovationslab.net --- EOF - Thanks again! On Wed, Dec 13, 2023 at 01:08:13PM -0800, Stig Venaas wrote: > Hi again > > Hoping we can get some more responses here. > > I've reviewed it myself, but would be great to have more people > reviewing the updates. > > WGLC ends in 2 days (the 15th). > > Thanks, > Stig > > On Tue, Nov 28, 2023 at 2:59 PM Stig Venaas <stig@venaas.com> wrote: > > > > Dear working group > > > > We have been working on progressing these core documents to Internet Standard. > > > > The documents are > > > > IANA Considerations for Internet Group Management Protocols > > https://datatracker.ietf.org/doc/draft-ietf-pim-3228bis/ > > > > Internet Group Management Protocol, Version 3 > > https://datatracker.ietf.org/doc/draft-ietf-pim-3376bis/ > > > > Multicast Listener Discovery Version 2 (MLDv2) for IPv6 > > https://datatracker.ietf.org/doc/draft-ietf-pim-3810bis/ > > > > As these are important documents, I am hoping we will get some people > > to review these drafts and give us feedback. We did not get any > > responses to the previous wglc for these documents. > > > > Please respond by December 15th 2023 whether you believe these > > documents are ready for publication, and any comments or concerns you > > may have. Any input is helpful. > > > > Regards, > > Stig >
- [pim] pim wglc for 3228bis, 3376bis and 3810bis Stig Venaas
- Re: [pim] pim wglc for 3228bis, 3376bis and 3810b… Stig Venaas
- Re: [pim] pim wglc for 3228bis, 3376bis and 3810b… Jeffrey (Zhaohui) Zhang
- Re: [pim] pim wglc for 3228bis, 3376bis and 3810b… Toerless Eckert
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Hitoshi Asaeda
- Re: [pim] IGMPv3 backward compatibility issue kil… Holland, Jake
- Re: [pim] WGLC feedback for draft-ietf-pim-3376bi… Toerless Eckert
- Re: [pim] IGMPv3 backward compatibility issue kil… Toerless Eckert
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Toerless Eckert
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Toerless Eckert
- [pim] WGLC feedback for draft-ietf-pim-3376bis (w… Toerless Eckert
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Stig Venaas
- [pim] IGMPv3 backward compatibility issue killing… Toerless Eckert
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Leonard Giuliano
- Re: [pim] pim wglc for 3228bis, 3376bis and 3810b… Brian Haberman
- Re: [pim] pim wglc for 3228bis, 3376bis and 3810b… Stig Venaas
- Re: [pim] WGLC feedback for draft-ietf-pim-3376bi… Toerless Eckert
- Re: [pim] WGLC feedback for draft-ietf-pim-3376bis Brian Haberman
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Stig Venaas
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Dave Katz
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Hitoshi Asaeda
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Dave Katz
- Re: [pim] IGMPv3 backward compatibility issue kil… N.Leymann
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Brian Haberman
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Stig Venaas
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Brian Haberman
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Hitoshi Asaeda
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Stig Venaas
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Hitoshi Asaeda
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Brian Haberman
- Re: [pim] [MBONED] IGMPv3 backward compatibility … N.Leymann
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Stig Venaas
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Brian Haberman
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Leonard Giuliano
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Stig Venaas
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Stig Venaas
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Hitoshi Asaeda
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Brian Haberman
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Stig Venaas
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Brian Haberman
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Stig Venaas
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Hitoshi Asaeda
- Re: [pim] [MBONED] IGMPv3 backward compatibility … N.Leymann
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Leonard Giuliano
- Re: [pim] [MBONED] IGMPv3 backward compatibility … Hitoshi Asaeda