[Isis-wg] draft-ietf-isis-gmpls-extensions-19.txt and unnumbered links
Jon Berger <Jon.Berger@dataconnection.com> Fri, 30 January 2004 16:10 UTC
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From: Jon Berger <Jon.Berger@dataconnection.com>
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Subject: [Isis-wg] draft-ietf-isis-gmpls-extensions-19.txt and unnumbered links
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Date: Fri, 30 Jan 2004 16:05:20 -0000
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Hello Kireeti, Yakov (and everyone else), I have the following comments to make on draft-ietf-isis-gmpls-extensions-19.txt. My key concerns are in the area of unnumbered links. 1. Regarding the Link Local/Remote sub-TLV: ---------------------------------------------- In sections 3.2 and 3.3 (regarding local and remote interface addresses) of the soon-to-be-RFCed draft-ietf-isis-traffic-05.txt, the following text appears: "If a router implements traffic engineering, it MUST include this sub-TLV." I do not believe this to be true, as unnumbered links will use the Link Local/Remote ID sub-TLV to identify a link's endpoints, rather than IP addresses. Since we cannot change the Traffic Engineering RFC(?), I would like to add a comment similar to the following to section 1.1 of draft-ietf-isis-gmpls-extensions-19.txt: "For unnumbered links, the Link Local/Remote Identifiers sub-TLV is used to identify a link. For numbered links the IPv4 interface address and IPv4 neighbor address sub-TLVs are used to identify a link. For each link only one set of sub-TLVs should be present." 2. Again, regarding the Link Local/Remote ID sub-TLV: -------------------------------------------------------- In section 3.1 the draft specifies that this sub-TLV 'MUST NOT occur more than once within the extended IS reachability TLV'. The limitation should actually be that the sub-TLV appear at most once per neighbor data structure. Likewise, where multiple instances of the sub-TLV are present, the draft dictates that if the 'sub-TLV occurs more than once within the extended IS reachability TLV, the receiver SHOULD ignore all these sub-TLVs'. As well as being incorrect for the reason stated above, I believe that this text is slightly unclear as to whether the receiver should discard all of the sub-TLVs, or just the superfluous ones (where my preference is the latter, which allows the receiver to be generous, and is preferable to ignoring all instances of the sub-TLV). My suggested replacement text for this section would be: 'The Link Local/Remote Identifiers sub-TLV MUST NOT occur more than once per IS neighbor data structure within the extended IS reachability TLV. If the Link Local/Remote Identifiers sub-TLV occurs more than once within an IS neighbor data structure in an extended IS reachability TLV, the receiver SHOULD ignore all bar the first of these sub-TLVs'. Note that this also corrects the misspelling of 'Identifiers'. 3. Link Protection Type sub-TLV: ----------------------------------- Section 3.2 is erroneous in the same way as section 3.1 - I suggest altering the text to: 'The Link Protection Type sub-TLV MUST NOT occur more than once per IS neighbor data structure within the extended IS reachability TLV. If the Link Protection Type sub-TLV occurs more than once within an IS neighbor data structure in an extended IS reachability TLV, the receiver SHOULD ignore all bar the first of these sub-TLVs'. 4. SRLG TLVs --------------- I believe that the description of the flag byte should include a comment specifically stating that the least significant bit determines whether Link IDs or IPv4 addresses will be used in the TLV (bit set to 1 - IP addresses, bit set to 0 - Link IDs). I propose adding the sentence: 'For a numbered interface, IPv4 addresses SHALL be used to describe the link, whereas for an unnumbered interface Link IDs SHALL be used.' 5. SRLG TLVs --------------- I think that it would be advisable to have the following comment (as we do in the Link ID sub-TLV description): 'If the Link Remote Identifier is unknown, it is set to 0.' Regards, Jon ----------------------------------------------- Jon Berger Network Protocols Group Data Connection Ltd (DCL) Tel: +44 20 8366 1177 Fax: +44 20 8363 1039 Email: jon.berger@dataconnection.com Web: http://www.dataconnection.com _______________________________________________ Isis-wg mailing list Isis-wg@ietf.org https://www1.ietf.org/mailman/listinfo/isis-wg