Re: [RTG-DIR] Rtgdir early review of draft-ietf-isis-mpls-elc-08
Peter Psenak <ppsenak@cisco.com> Fri, 04 October 2019 11:14 UTC
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From: Peter Psenak <ppsenak@cisco.com>
To: Dhruv Dhody <dhruv.ietf@gmail.com>, rtg-dir@ietf.org
Cc: lsr@ietf.org, draft-ietf-isis-mpls-elc.all@ietf.org, ietf@ietf.org
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Date: Fri, 04 Oct 2019 13:14:35 +0200
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Subject: Re: [RTG-DIR] Rtgdir early review of draft-ietf-isis-mpls-elc-08
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Hi Dhruv, please see inline (##PP): On 12/09/2019 12:06, Dhruv Dhody via Datatracker wrote: > Reviewer: Dhruv Dhody > Review result: Has Issues > > Subject: RtgDir Early review: draft-ietf-isis-mpls-elc-08 > > Hello > > I have been selected to do a routing directorate “early” review of this draft. > https://datatracker.ietf.org/doc/draft-ietf-isis-mpls-elc/ > > The routing directorate will, on request from the working group chair, perform > an “early” review of a draft before it is submitted for publication to the > IESG. The early review can be performed at any time during the draft’s lifetime > as a working group document. The purpose of the early review depends on the > stage that the document has reached. > > As this document is in working group last call, my focus for the review was to > determine whether the document is ready to be published. Please consider my > comments along with the other working group last call comments. > > For more information about the Routing Directorate, please see > http://trac.tools.ietf.org/area/rtg/trac/wiki/RtgDir > > Document: draft-ietf-isis-mpls-elc-08 > Reviewer: Dhruv Dhody > Review Date: 12-09-2019 > Intended Status: Standards Track > > Summary: I have some minor concerns about this document that I think should be > resolved before it is submitted to the IESG. > > The draft is focused and straightforward, the reader needs to be aware of > RFC6790 and draft-ietf-mpls-spring-entropy-label beforehand. I have reviewed > this and the OSPF I-D together and you will find similar comments for both I-Ds. > > Minor > ***** > (1) Could you mark that the codepoints mentioned in the draft are early > allocated by IANA? Currently it says the value are desired. I also suggest > following change in Section 7 (IANA Considerations) - > > OLD: > IANA is requested to allocate the E-bit (bit position 3 is desired) > from the "Bit Values for Prefix Attribute Flags Sub-TLV" registry. > > IANA is requested to allocate a MSD type (the type code of 2 is > desired) from the "IGP MSD Types" registry for ERLD. > NEW: > IANA is requested to confirm the early allocation of the E-bit (Bit > position 3) in the "Bit Values for Prefix Attribute Flags Sub-TLV" > registry. > > IANA is requested to confirm the early allocation of the ERLD (type > code of 2) in the "IGP MSD Types" registry. > END ##PP I'm not sure above is necessary, given that the above text would change eventually to simply say which code points have been allocated. > > (2) Section 3 talks about ERLD in Node MSD sub-TLV. But what happens if one > receives ERLD in the Link MSD sub-TLV? As per my understanding this is not > allowed, better to add normative text for the case then. ##PP added a sentence > > Also we have this text in draft-ietf-mpls-spring-entropy-label - > > In a distributed switching architecture, each linecard may have a > different capability in terms of ERLD. For simplicity, an > implementation MAY use the minimum ERLD of all linecards as the ERLD > value for the system. > > There may also be a case where a router has a fast switching path > (handled by an ASIC or network processor) and a slow switching path > (handled by a CPU) with a different ERLD for each switching path. > Again, for simplicity's sake, an implementation MAY use the minimum > ERLD as the ERLD value for the system. > > The drawback of using a single ERLD for a system lower than the > capability of one or more specific component is that it may increase > the number of ELI/ELs inserted. This leads to an increase of the > label stack size and may have an impact on the capability of the > ingress node to push this label stack. > > If we are deviating from this and opting for the node (marked 'MAY' above) as > the only possibility, we need to handle this properly. Maybe check with > chairs/AD on this! ##PP A remote router introducing the EL may not always know the LC/interface over which the traffic he sends is received on the remote node. So I don't really see much of the value advertising ERLD per link. Sure, chairs/AD will have their chance during the review :) > > (3) Section 4, can we add some more description on what the 'E' flags means, in > the similar style of other flags > [https://tools.ietf.org/html/rfc7794#section-2.1] ##PP done > > (4) Section 8, suggest to also add one sentence for the impact of advertising > incorrect ERLD. If there isn't any, that can also be stated. ##PP done > > Nits > **** > (1) Suggested ordering of sections - ..ELC/ERLD/BGP-LS/ACK.. [matching between > OSPF/ISIS] ##PP done >(2) Section 2, add [I-D.ietf-mpls-spring-entropy-label] for > terminology reference ##PP done >(3) Section 3, Add reference to > draft-ietf-mpls-spring-entropy-label for the definition and usage of ERLD The Introduction section has: "This capability, referred to as Entropy Readable Label Depth (ERLD) as defined in [I-D.ietf-mpls-spring-entropy-label] " > (4) > Section 6, > > The ERLD MSD-type introduced for IS-IS in Section 3 is advertised > using the Node MSD TLV (TLV 266) of the BGP-LS Node NLRI Attribute as > defined in section 3 of [I-D.ietf-idr-bgp-ls-segment-routing-ext]. > > I think you mean draft-ietf-idr-bgp-ls-segment-routing-msd here! ##PP right, corrected it. > > Also, maybe change the title "BGP-LS Extension" as there is no 'extension' > required, ELC/ERLD is BGP-LS would be automatically supported. ##PP renamed to "Signaling ELC and ERLD in BGP-LS". > > (5) Expand MSD on first use. ##PP done. > (6) The first figure is titled Figure 2! ##PP fixed > (7) Section 4, mark the figure as "Prefix Attribute Flags" ##PP done > (8) All references are marked Normative, please re-check if this is intentional. ##PP done. thanks, Peter > > Thanks! > Dhruv > > > >
- [RTG-DIR] Rtgdir early review of draft-ietf-isis-… Dhruv Dhody via Datatracker
- Re: [RTG-DIR] Rtgdir early review of draft-ietf-i… Acee Lindem (acee)
- Re: [RTG-DIR] Rtgdir early review of draft-ietf-i… Acee Lindem (acee)
- Re: [RTG-DIR] Rtgdir early review of draft-ietf-i… Peter Psenak