[CCAMP] draft-ietf-ccamp-rfc5787bis
"Adrian Farrel" <adrian@olddog.co.uk> Fri, 25 November 2011 19:44 UTC
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From: Adrian Farrel <adrian@olddog.co.uk>
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Date: Fri, 25 Nov 2011 19:43:53 -0000
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Cc: draft-ietf-ccamp-rfc5787bis@tools.ietf.org
Subject: [CCAMP] draft-ietf-ccamp-rfc5787bis
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Hi, I have done my usual AD review prior to putting the draft forward for IETF last call and IESG review. I have a number of questions and issues that I would like you to address in a new revision. Some of these things are questions that can be handled either by discussion or by making changes to the draft. Other issues are more substantive and will need updates to the document. I have move the draft into Revised I-D needed, and will wait for the new revision. Thanks, Adrian --- If I understand correctly, the intention of this document is to entirely replace (i.e. obsolete) RFC 5787. That's OK, but you need to do several things: 1. State in the document header Obsoletes: 5787 (if approved) 2. Remove "Updates to" and "(RFC 5787bis)" from the document title 3. Add a statement to the Abstract (usually the last sentence) to say "This document obsoletes RFC 5787" 4. Add a final paragraph to summarise why this document obsoletes RFC 5787 and to mention the change to standards track. 5. Include a section called "Changes from RFC 5787" --- Section 2 RAs are hierarchically contained: a higher-level (parent) RA contains lower-level (child) RAs that in turn MAY also contain RAs, etc. Why MAY not may? Why "etc." ? --- Please expand acronyms on first use. For example SCN. --- Section 3 In the context of OSPF Traffic Engineering (TE), an ASON transport node corresponds to a unique OSPF TE node. An OSPF TE node is uniquely identified by the TE Router Address TLV [RFC3630]. In this document, this TE Router Address is referred to as the TE Router ID, which is in the ASON transport plane name space. The TE Router ID should not be confused with the OSPF Router ID which uniquely identifies an OSPF router within an OSPF routing domain [RFC2328] and is in a name space for control plane components. Note: The Router Address top-level TLV definition, processing, and usage are unchanged from [RFC3630]. This TLV specifies a stable OSPF TE node IP address, i.e., the IP address is always reachable when there is IP connectivity to the associated OSPF TE node. Note that RFC 3630 does not define a "TE Router Address TLV" You seem to recognize this in the second paragraph. You seem to acknowledge that the Router Address TLV contains a stable OSPF TE node IP address that is always reachable when there is IP connectivity to the associated OSPF TE node. As far as I can tell, this means that the address comes from the SCN space not from the transport name space as you have claimed. It may be that you need or desire some overlap of spaces, but you have not made any statement to that effect. In fact I am surprised that you say that there is a 1:1 correspondence between a transport node and an OSPF TE node. This sounds like an implementation detail unless an OSPF TE node is a logical concept. If it is, it would be really useful to explain it. It does not help that you have not defined "OSPF TE node" and you freely mix that term with the term "OSPF router". It should be clear to you that there are OSPF protocol speakers and there are transport nodes on behalf of which the protocol speakers distribute information. Please have another attempt at this section making clear what the OSPF entities are and how they map to actual things. You obviously did not like the content of Section 5.1 of RFC 5787, but you seem to have thrown out the baby with the bathwater. Furthermore, in Section 6 you have Hence, a single OSPF router (i.e., the PC) MUST be able to advertise on behalf of multiple transport layer nodes. The OSPF routers are identified by OSPF Router ID and the transport nodes are identified by TE Router ID. which is very good, but appear to contradict In the context of OSPF Traffic Engineering (TE), an ASON transport node corresponds to a unique OSPF TE node. Probably you intend to say that an ASON transport node is represented by a single OSPF TE node and that an OSPF TE node may represent more than one ASON transport node. You haven't actually excluded that in what you write, but it is not very clear. --- Section 4 Reachability in ASON refers to the set of endpoints reachable in the transport plane by a node or the reachable endpoints of a level N. Can you please rewrite this for clarity. "Reachability" cannot refer to a set of anything per se; it is a quality. The definition also seems circular since you do not define what reachable means. --- Section 4 "(ASON SNPP name space)" What is this? You have already told us that ASON has just three name spaces and this was not one of them. What is SNPP? --- Section 4 You say: The data plane node is identified in the control plane by its TE Router ID, as discussed in section 6. This contradicts what you say in Section 3 where the TE Router ID is an IP reachable address and so is an SCN identifier not a control plane identifier. --- Section 4 As a consequence, it MUST be possible for the router to originate more than one TE LSA containing the Node Attribute TLV when used for ASON reachability advertisement. Hence, the Node Attribute TLV [RFC5786] advertisement rules must be relaxed for ASON. A Node Attribute TLV MAY appear in more than one TE LSA originated by the RC when the RC is advertising reachability information for a different transport node identified by the Local TE Router Sub-TLV (refer to section 6.1). This looks like you are updating RFC 5786. You will need to make this explicit and to assure me that the OSPF working group has signed off on this change. Since you are making the relaxation specific to ASON (or are you making it general?) you will need to explain how a node receiving a second TE LSA containing a node attribute TLV will know that it is an ASON advertisement. --- Section 5.2 GMPLS routing defines an Interface Switching Capability Descriptor (ISCD) that provides, among other things, the available (maximum/minimum) bandwidth per priority available for Label Switched Path (LSPs). - Too many instances of "available" - The ISCD doesn't provide the bandwidth, only the information about the bandwidth --- Section 6 For ASON routing, the control plane component routing adjacency topology (i.e., the associated Protocol Controller (PC) connectivity) and the transport topology are NOT assumed to be congruent [RFC4258]. Lower case "not" please. --- Section 6 The Router Address TLV [RFC3630] is used to advertise the TE Router ID associated with the advertising Routing Controller. TE Router IDs for additional transport nodes are advertised through specification of the Local TE Router Identifier in the Local and Remote TE Router TE sub-TLV and the Local TE Router Identifier sub-TLV described in the sections below. These Local TE Router Identifiers are typically used as the local endpoints for TE Label Switched Paths (LSPs) terminating on the associated transport node. I found this a bit odd. Previously you have said that a TE Router ID is associated with a transport node that it identifies. Now you seem to be saying that a TE Router ID is associated with an RC, and implying that an RC is a transport node (since you say "for additional transport nodes"). --- Section 6 It MAY be feasible for multiple OSPF Routers to advertise TE information for the same transport node. However, this is not considered a required use case and is not discussed further. The use of "MAY" is in the wrong scope. How about... The use of multiple OSPF Routers to advertise TE information for the same transport node is not considered a required use case and is not discussed further in this document. --- Section 6.1 An OSPF router advertising on behalf of multiple transport nodes will require additional information to distinguish the link endpoints amongst the subsumed transport nodes. In order to unambiguously specify the transport topology, the local and remote transport nodes MUST be identified by TE router ID. "subsumed" seems a bit dramatic! How about... When an OSPF Router advertises on behalf of multiple transport nodes, the link end points cannot be automatically assigned to a single transport node associated with the advertising router. In this case, the link advertisement also includes identifiers of the link end points. --- Section 6.1 The Type field of the Local and Remote TE Router ID sub-TLV is assigned the value 26 (see Section 10). AFAICS, no early allocation was performed. Therefore, please replace "26" with TBDx. Similarly in 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type (26) | Length (8) | --- Section 6.1 The value of the Local and Remote TE Router Identifier SHOULD NOT be set to 0. This use of "SHOULD NOT" implies that a value of 0 MAY be used for some reason. Please clarify. --- Section 6.1 This section reminds me to ask what plans the WG has to support IPv6. --- Section 6.1 This sub-TLV MUST be included as a sub-TLV of the top-level Link TLV if the OSPF router is advertising on behalf of one or more transport nodes having TE Router IDs different from the TE Router ID advertised in the Router Address TLV. Therefore, it MUST be included if the OSPF router is advertising on behalf of multiple transport nodes. Note: The Link ID sub-TLV identifies the other end of the link (i.e., Router ID of the neighbor for point-to-point links) [RFC3630]. When the Local and Remote TE Router ID Sub-TLV is present, it MUST be used to identify local and remote transport node endpoints for the link and the Link-ID sub-TLV MUST be ignored. The Local and Remote ID sub- TLV, if specified, MUST only be specified once. A lot of "MUST" without explaining what the process is if not. A receiver getting no sub-TLV assumes what? A router advertising on behalf of the transport node with the same TE Router ID MAY / MUST NOT include sub-TLVs. If there is more than one sub-TLV present the receiver should do what? Does "Therefore, it MUST be included if the OSPF router is advertising on behalf of multiple transport nodes" imply the sub-TLV must be included even when the advertisement is for the transport node with the same TE Router ID? --- Section 6.2 Per previous comments on IANA Please change "5" to TBDy in... The Type field of the Local TE Router ID sub-TLV is assigned the value 5 (see Section 10). The Length field takes the value 4. The ...and... 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... | Type (5) | Length (4) | --- Section 6.2 This sub-TLV MUST be included as a sub-TLV of the top-level Node Attribute TLV if the OSPF router is advertising on behalf of one or more transport nodes having TE Router IDs different from the TE Router ID advertised in the Router Address TLV. Therefore, it MUST be included if the OSPF router is advertising on behalf of multiple transport nodes. Similar questions as per 6.1. What can a receiver assume if the sub-TLV is not present? Does the final sentence mean that the sub-TLV must be included even in the case where the advertisement is for the same TE Router ID? Can the sender include the sub-TLV when it only advertises for a single transport node? What if there is more than one sub-TLV present? --- Section 7 An ASON routing area (RA) represents a partition of the data plane, and its identifier is used within the control plane as the representation of this partition. An RA may contain smaller RAs inter-connected by links. ASON RA levels do not map directly to OSPF areas. Rather, hierarchical levels of RAs are represented by separate OSPF protocol instances. It would be interesting to add a statement about the correspondence between RAs and OSPF areas (per section 2). --- Section 7 It isn't clear to me reading this section and the subsections whether export happens at a single node that is present in both parent and child RA, or whether there is an "export interface" between nodes. I would assume that an implementation could place the export within a box, but that there is no architectural constraint. That means that the export function is an exposed function. If so, where is the protocol definition? --- Section 7.2.1 IANA stuff again Please replace: 27 as TBDz1 28 as TBDz2 in... The type value 28 (see Section 10) will indicate that the associated routing information has been exported downward. The type value 27 (see Section 10) will indicate that the associated routing information has been exported upward. and in... The Type field of the Inter-RA Export Upward and Inter-RA Export Downward sub-TLVs are respectively assigned the values 27 and 28 (see Section 10). and... 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Upward/Downward Type (27/28) | Length (4) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ --- Section 7.2.2 When exporting routing information upward in the ASON routing hierarchy, any information received from a level above, i.e., tagged with an Inter-RA Export Downward Sub-TLV, MUST NOT be exported upward. Since an RA at level N is contained by a single RA at level N+1, this is the only checking that is necessary and the associated RA ID is used solely for informational purposes. Agreed. And what should the receiver do if it receives such an export? Ditto for In order words, routing information MUST NOT be exported downward into the RA from which it was received. --- Section 8 The extensions described herein are only applicable to ASON routing domains and it is not expected that the attendant reachability (see Section 4) and link information will ever be mixed with global or local IP routing information. I am not quite sure what you mean by "mixed" or by "local IP routing information". You may be saying that you expect (require?) that TE information s exchanged in a separate instance of OSPF than is used for exchanging SCN routing information. If that is what you are hoping for, I expect you will be sadly disappointed by the entire deployed GMPLS base. For a single RA it makes complete sense to run just one instance of OSPF that exchanges information about SCN IP reachability and also transport plane TE info. It gets more complicated with a multi-RA system, and you need to address that. --- Section 8 You give some good advice, but you do it with nested 2119 language. I don't know how to interpret "You SHOULD apply a MUST". Additionally, since you say "SHOULD", you need to explain what the associated MAY condition is. --- Section 9 Here is an attack vector... Suppose a small child RA is infiltrated. A very large (unmanageably large) number of LSAs are exported to the parent. This may swamp the parent making it impossible for it to function. Additionally, the parent may export all the LSAs to another child (which being a child) has less processing capabilities. The implication is that the policy points at import/export need to be capable of providing policing and maybe able to throttle import volume. --- Section 10 As previously discussed, there was no early allocation. Please delete This draft requests early allocation of IANA code points in accordance with [RFC4020]. [NOTE TO RFC Editor: this paragraph and the RFC 4020 reference can be removed during RFC editing]. --- Section 10.1 OLD - Local and Remote TE Router ID sub-TLV (26) - Inter-RA Export Upward sub-TLV (27) - Inter-RA Export Downward sub-TLV (28) NEW - Local and Remote TE Router ID sub-TLV (TBDx) - Inter-RA Export Upward sub-TLV (TBDz1) - Inter-RA Export Downward sub-TLV (TBDz2) END --- Section 10.2 OLD - Local TE Router ID sub-TLV (5) - Inter-RA Export Upward sub-TLV (27) - Inter-RA Export Downward sub-TLV (28) NEW - Local TE Router ID sub-TLV (TBDy) - Inter-RA Export Upward sub-TLV (TBDz1) - Inter-RA Export Downward sub-TLV (TBDz2) END --- Section 10.3 OLD - Inter-RA Export Upward sub-TLV (27) - Inter-RA Export Downward sub-TLV (28) NEW - Inter-RA Export Upward sub-TLV (TBDz1) - Inter-RA Export Downward sub-TLV (TBDz2) END --- Section 12 The following table shows how this draft complies with the s/draft/document/ to that requirement, and the fourth column lists the relevant section in draft, and/or another RFC that already satisfies the requirement. s/in draft/in this document/ --- Section 12 | 3.1 (3) | Prior to establishing | Yes when RA |Section 11.1 | | | communications, RCs MUST | maps to OSPF | | | |verify that they are bound | Area ID. | | | | to the same parent RA. | | | But you only recommend that correspondence. So what happens to this requirement if RA does not map to OSPF Area? Should you address this case, or should you require the correspondence? --- Section 12 | 3.2 (8) | Routing Information | No - Not | | | |exchanged between levels N | described. | | | | and N+1 via external link | | | | | (inter-RA links). | | | and | 3.2 (15) | The Level N routing | Not described | N/A | | | function is on a separate | but possible. | | | | system the Level N+1 | | | | | routing function. | | | I think this ties to my question on section 7. I think you should make clearer in the preamble that you are only addressing the case where the level boundary occurs within an RC. Since you are doing this work to address a need from the OIF where layer boundaries have typically been exposed through an external protocol interface, I am a little puzzled by your choice to limit your work. Maybe a figure in an early section would show how RAs and RCs are presented in the part of the problem you are solving. --- Section 12 | 3.3 (16) |The RC MUST support static | Yes - | Sections 2 | | | (i.e., operator assisted) | automation |and 3. Config| | | and MAY support automated |requirement is | is product | | | configuration of the | ambiguous. | specific. | | |information describing its | | | | |relationship to its parent | | | | | and its child within the | | | | | hierarchical structure | | | | | (including RA ID and RC | | | | | ID). | | | Does "automation requirement is ambiguous" mean "automation not supported"? --- Section 12 | 5 (29) | In order to support |Partial - OSPF |RFC 2328 and | | | operator-assisted changes | supports the | RFC 5250 | | | in the containment | purging of | | | | relationships of RAs, the | stale | | | | routing protocol SHALL |advertisements | | | |support evolution in terms |and origination| | | | of the number of | of new. The | | | |hierarchical levels of RAs.|non-disruptive | | | | For example: support of | behavior is | | | | non-disruptive operations |implementation | | | |such as adding and removing| specific. | | | | RAs at the top/bottom of | | | | | the hierarchy, adding or | | | | | removing a hierarchical | | | | |level of RAs in or from the| | | | |middle of the hierarchy, as| | | | | well as aggregation and | | | | | segmentation of RAs. | | | Surely this requirement demands a section explaining how the function is achieved. --- Section 14 It is usual to inherit acknowledgements from the obsoleted RFC where there is a lot of shared text. You should also thank any external SDO that was consulted through a liaison process. --- Appendix A Management domain Text format problem
- [CCAMP] draft-ietf-ccamp-rfc5787bis Adrian Farrel
- Re: [CCAMP] draft-ietf-ccamp-rfc5787bis Andrew G. Malis