Re: Re: [ssm] AD-review comments on draft-ietf-ssm-arch-04.txt
Hugh Holbrook <holbrook@cisco.com> Sat, 17 July 2004 07:59 UTC
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From: Hugh Holbrook <holbrook@cisco.com>
To: Alex Zinin <zinin@psg.com>, ssm@ietf.org, pekkas@netcore.fi
In-reply-to: <20040716000557.014A310B7D8@holbrook-laptop.cisco.com>
Subject: Re: Re: [ssm] AD-review comments on draft-ietf-ssm-arch-04.txt
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Pekka, thanks for reading and specifically for confirming my understanding of MBGP. As promised, here is a list of specific changes that are planned to appear in the next revision of the document in response to Alex's commentes. I'm about to submit a new version that incorporates all of these changes. If further changes are necessary, I will revise and resubmit, but I plan to go ahead and submit a version with these changes before the draft submission deadline. Cheers, -Hugh ---------------------------------------------------------------- I. All of Alex's Editorial changes. I have not listed the specific editorial changes here; I did exactly what Alex suggested. II. Add text saying that hosts must implement IGMPv3/MLDv2, and also the igmpv3/mldv2-changes-for-ssm document. REPLACE in Section 4.2 (Requirements on the Host IP Module) A separate document describes how IGMPv3 and MLDv2 are adapted to support source-specific multicast. WITH A host that supports the SSM service model MUST implement the host portion of [IGMPv3] for IPv4 and [MLDv2] for IPv6. It MUST also conform to the IGMPv3/MLDv2 behavior described in [GMP-SSM]. III. Add text mandating PIM-SSM and IGMPv3/MLDv2 for routers to section 5.2 (Router Requirements/Protocols) REPLACE Companion documents will specify the required modifications to those protocols to support SSM. WITH A router that supports the SSM service model MUST implement the PIM-SSM subset of the PIM-SM protocol from [PIM-SM] and MUST implement the router portion of [IGMPv3] for IPv4 and [MLDv2] for IPv6. An SSM router MUST also conform to the IGMPv3/MLDv2 behavior described in [GMP-SSM]. IV. Mandate that PIM-SSM implementation be able to use the unicast topology for RPF lookups, also in section 5.2 ADD the following paragraph, after insertion III above. With PIM-SSM, successful establishment of an (S,G) forwarding path from the source S to any receiver depends on hop-by-hop forwarding of the explicit join request from the receiver toward the source. The protocol(s) and algorithms that are used to select the forwarding path for this explicit join must provide a loop-free path. When using PIM-SSM, the PIM-SSM implementation MUST (at least) support the ability to use the unicast topology database for this purpose. V. References Changes ADD a new normative reference to the IGMPv3/MLDv2-for-SSM document. [GMP-SSM] H. Holbrook and B. Cain, "IGMPv3/MLDv2 for SSM", draft-holbrook-idmr-igmpv3-ssm-07 (Work in Progress), June 2004. .PP REPLACE the previous reference to the old PIM RFC with a reference to the new one: [PIM-SM] B. Fenner, M. Handley, H. Holbrook, and I. Kouvelas. "Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification (Revised)," draft-ietf-pim-sm-v2-new-10.txt (Work in Progress), July 2004. MOVE the IGMPv3, MLDv2, and PIM-SM references to the normative reference section, as they are all REQUIRED with a capital R. The full diffs of the nroff source follow =================================================================== RCS file: RCS/draft-ietf-ssm-arch.nroff,v retrieving revision 1.6 diff -uw -r1.6 draft-ietf-ssm-arch.nroff --- draft-ietf-ssm-arch.nroff 2003/10/20 07:40:04 1.6 +++ draft-ietf-ssm-arch.nroff 2004/07/17 07:17:07 @@ -9,22 +9,22 @@ .ds RF PUTFFHERE[Page %] .ds CF .ds LH INTERNET-DRAFT -.ds RH 19 Oct 2003 +.ds RH 18 Jul 2004 .ds CH Source-Specific Multicast .ad l .in 0 .na INTERNET-DRAFT Source-Specific Multicast H. Holbrook -Expires Apr 19, 2004 Cisco Systems +Expires Jan 18, 2005 Cisco Systems B. Cain Storigen Systems - 19 Oct 2003 + 18 Jul 2004 .sp 2 .nr PI 0n .ce Source-Specific Multicast for IP .ce -<draft-ietf-ssm-arch-04.txt> +<draft-ietf-ssm-arch-05.txt> .sp .in 0 .ne 4 @@ -48,10 +48,6 @@ .PP The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. -.SH -The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", -"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this -document are to be interpreted as described in RFC 2119 [RFC 2119]. .PP .bp .SH @@ -65,7 +61,7 @@ For IP version 6 (IPv6), the address prefix FF3x::/32 is reserved for source-specific multicast use. -It defines an extension to the Internet +This document defines an extension to the Internet network service that applies to datagrams sent to SSM addresses and defines the host and router requirements to support this extension. .NH 1 @@ -176,6 +172,10 @@ which a client sends a multicast query directly to a "service location group" to which servers listen is not directly supported by SSM. +.SH +The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", +"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this +document are to be interpreted as described in RFC 2119 [RFC 2119]. .PP This document defines the semantics of source-specific multicast addresses @@ -386,10 +386,12 @@ sends an unsubscription request for that channel to interface I. .PP These requests will typically be Internet Group Management Protocol -version 3 messages for IPv4, or Multicast Listener Discovery -Version 2 messages for IPv6 [IGMPv3,MLDv2]. -A separate document describes how IGMPv3 and MLDv2 -are adapted to support source-specific multicast. +version 3 (IGMPv3) messages for IPv4, or Multicast Listener Discovery +Version 2 (MLDv2) messages for IPv6 [IGMPv3,MLDv2]. +A host that supports the SSM service model MUST implement the host +portion of [IGMPv3] for IPv4 and [MLDv2] for IPv6. It MUST also +conform to the IGMPv3/MLDv2 behavior described in +[GMP-SSM]. .NH 2 Allocation of Source-Specific Multicast Addresses .PP @@ -480,9 +482,19 @@ communicate source-specific joins to neighboring routers (in particular, PIM-SM [PIM-SM]), and these protocols can, with slight modifications, be used to provide source-specific semantics. -Companion documents -will specify the required modifications to those protocols -to support SSM. +A router that supports the SSM service model MUST implement the +PIM-SSM subset of the PIM-SM protocol from [PIM-SM] and MUST +implement the router portion of [IGMPv3] for IPv4 and [MLDv2] for IPv6. +An SSM router MUST also conform to the IGMPv3/MLDv2 behavior +described in [GMP-SSM]. +.PP +With PIM-SSM, successful establishment of an (S,G) forwarding path +from the source S to any receiver depends on hop-by-hop forwarding of +the explicit join request from the receiver toward the source. The +protocol(s) and algorithms that are used to select the forwarding path +for this explicit join must provide a loop-free path. When using PIM-SSM, +the PIM-SSM implementation MUST (at least) support the ability to use the +unicast topology database for this purpose. .PP A network can concurrently support SSM in the SSM address range and any-source multicast @@ -743,6 +755,9 @@ [ETHERv6] Crawford, M., "Transmission of IPv6 Packets over Ethernet Networks", RFC2464, Dec 1998. .PP +[GMP-SSM] H. Holbrook and B. Cain, +"IGMPv3/MLDv2 for SSM", draft-holbrook-idmr-igmpv3-ssm-07 (Work in Progress), June 2004. +.PP [IPSEC] S. Kent, R. Atkinson, "Security Architecture for the Internet Protocol.", RFC 2401. .PP @@ -781,14 +796,15 @@ October 2002. .PP [MLDv2] R. Vida, and L. Costa. -"Multicast Listener Discovery Version 2 (MLDv2) for IPv6." -Work in Progress. +"Multicast Listener Discovery Version 2 (MLDv2) for IPv6," RFC3810, +June 2004. .PP [MSFAPI] Thaler, D., Fenner, B., and Quinn, B. "Socket Interface Extensions for Multicast Source Filters." Work in Progress. .PP -[PIM-SM] Estrin, D., Farinacci, D., Helmy, A., Thaler, D., Deering, S., -Handley, M., Jacobson, V., Liu, C., Sharma, P. and L. Wei, "Protocol Independent -Multicast-Sparse Mode (PIM-SM): Protocol Specification," RFC 2362, June 1998. +[PIM-SM] B. Fenner, M. Handley, H. Holbrook, and I. Kouvelas. +"Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol +Specification (Revised)," draft-ietf-pim-sm-v2-new-10.txt (Work in +Progress), July 2004. .PP [PIM-DM] Deering, S., Estrin, D., Farinacci, D., Jacobson, V., Helmy, A., Meyer, D., and L. Wei, @@ -832,6 +848,11 @@ .SH Intellectual Property Rights Notice .PP +The IETF has been notified of intellectual property rights +claimed in regard to some or all of the specification contained +in this document. For more information consult the online list +of claimed rights. +.PP The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology @@ -855,7 +876,7 @@ .SH Full Copyright Statement .PP -Copyright (C) The Internet Society (2002). All Rights Reserved. +Copyright (C) The Internet Society (2004). All Rights Reserved. .PP This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it @@ -885,5 +906,5 @@ .\" .bp .\" .ls 1 .\" Comment out the table of contents for now .PX -This document expires Apr 19, 2004. +This document expires Jan 18, 2005. > > Hi, Alex. > > Thanks for your comments. Sorry for the very delayed response; I was > out on paternity leave and got embarassingly far behind... Anyway, > let me respond now. > > - I will incorporate all of your editorial comments into the next > revision of the draft; thanks. > > Regarding your other comments suggesting that this document needs to > address protocol requirements. Generally, I think this is a good > idea. > > The history on this is that when the draft was first written, > "PIM-SSM" as a concept did not exist -- the first revisions of this > predated the new pim-sm spec by quite a bit. Likewise, IGMPv3 was > still at the very early draft stage, and I don't think MLDv2 had any > document at the time. But things have obviously changed since the -00 > version of the -arch documetn, and so I think your suggestion of > mandating some protocols to ensure interoperability is a good one. So > here is a list of changes that I propose we make to the draft: > > There are two places where I think we should consider the > ineroperability issue: > > hosts-to-routers > router-to-router > > Each of these is discussed below. > > - For the host-to-router case, I think your suggestion of mandating > IGMPv3/MLDv2 for hosts and routers that wish to support the SSM > service is a good one. This is essentially true in practice anyway, > so I don't anticipate this as being a contentious point. > > One point that I'd like to solicit input from the list about is what > to say about draft-holbrook-idmr-igmpv3-ssm-07.txt. This is the > document that describes IGMPv3/MLDv2 modifications and clarifications > to make SSM work better. There are a lot of SHOULDs in the document, > but it really only has one MUST in it: it disallows the optional > IGMPv3 behavior in which an older-version report for (*,G) can > suppress an IGMPv3 report for (S,G). This is a DoS prevention issue. > Otherwise, an attacker could use an IGMPv1 report to deny SSM service > to someone else on the same LAN. My current thinking is to say that > draft-holbrook-idmr-igmpv3-ssm-07 MUST be implemented, but I don't > feel that strongly as this is at worst a DoS issue and is somewhat of > a corner case. I'd appreciate comments from anyone on this topic. > > - For the router-to-router case, In order to ensure interoperabiliity, > I think the document should say that routers that provide SSM service > MUST (at least) support the PIM-SSM subset of PIM from pim-sm-v2-new. > This is a practical requirement anyway, so it just codifies what is > the common practice, and is hopefully not controversial. > > The final question in my mind is what if anything to say about the > protocol requirements to address SSM's need for an underlying topology > database that is used to route join messages toward the source. This > really derives from the use of PIM-SSM for routing, because it does > not have its own topology exchange protocol. > > I think it would be appropriate to say that the PIM-SSM implementation > MUST support the ability to use the unicast topology database for RPF > decisions, without mandating a specific protocol (e.g., DO NOT mention > OSPF, BGP, MBGP, etc.). This requirement, if implemented in all > routers, will ensures that an SSM route can be (assuming sufficient > processing and memory in routers along the way) established from any > host that is reachable by unicast. And I think this is exactly the > right requirement for this document. This ensures interoperability > for both the inter- and intra-domain SSM routing cases without > specifically mentioning the distinction and without needing to require > any specific unicast routing protocol, which is I think the right > level of requirement. > > I don't believe that there is really enough experience with the use of > a multicast-specific topology (with some minor exceptions like static > routes to multicast sources) to mandate anything about it. > Specifically, I don't think it's appropriate to mandate MBGP at this > point. It is not a requirement for multicast interoperability, and I > don't think it would be appropriate to say anything about it in the > architecture spec. This information is based on discussions with some > of the more knowledgeable folks on the topic at Cisco; anyone who has > different (or even the same) opinion on this topic is encouraged to > comment. > > If there is rough consensus on the mailing list, then I will send some > proposed text to the mailing list and revise and resubmit the draft > this week. > > Comments from the working group (or ADs) are appreciated. > > Thanks again for the careful review, Alex. > > -Hugh > > > Folks- > > > > Please find attached my AD-review comments on the SSM architecture > > document. > > > > -- > > Alex > > http://www.psg.com/~zinin/ > > > > Generally the document is in a great shape. Very good job. I have one meta > > issue and one editorial nit. > > > > Meta: > > > > The document does not spell out what protocols hosts and routers MUST > > implement. I.e., this kind of document is expected to specify the > > mandatory-to-implement mechanisms that will ensure that hosts and routers can > > interoperate. However, there is no place in the document where it says > > something like "hosts supporting the SSM network service MUST implement IGMPv3 > > for IPv4 and MLDv2 for IPv6", or "routers supporting the SSM network service > > MUST implement PIM-SSM..." > > > > Editorial > > > > The following part: > > > > > The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", > > > "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this > > > document are to be interpreted as described in RFC 2119 [RFC 2119]. > > > > should be moved inside the body of the document (preferably not in Abstract) > > > > Abstract: > > > > > IP addresses in the 232/8 (232.0.0.0 to 232.255.255.255) range are > > > designated as source-specific multicast (SSM) destination addresses and > > > are reserved for use by source-specific applications and protocols. For > > > IP version 6 (IPv6), the address prefix FF3x::/32 is reserved for > > > source-specific multicast use. It defines an extension to the Internet > > ^^ > > needs to be expanded. "This document" ? > > > > > > Section "Intellectual Property Rights Notice". To reflect the situation > > with Apple, this section also needs to include the following paragraph > > from RFC 2026. > > > > "The IETF has been notified of intellectual property rights > > claimed in regard to some or all of the specification contained > > in this document. For more information consult the online list > > of claimed rights." > > > > > > > > _______________________________________________ > > ssm mailing list > > ssm@ietf.org > > https://www1.ietf.org/mailman/listinfo/ssm > > _______________________________________________ > ssm mailing list > ssm@ietf.org > https://www1.ietf.org/mailman/listinfo/ssm _______________________________________________ ssm mailing list ssm@ietf.org https://www1.ietf.org/mailman/listinfo/ssm
- [ssm] AD-review comments on draft-ietf-ssm-arch-0… Alex Zinin
- Re: [ssm] AD-review comments on draft-ietf-ssm-ar… Hugh Holbrook
- Re: [ssm] AD-review comments on draft-ietf-ssm-ar… Pekka Savola
- Re: Re: [ssm] AD-review comments on draft-ietf-ss… Hugh Holbrook