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主题： [Lsr] Re: RtgDir Last Call Review: draft-ietf-lsr-multi-tlv-06
时间： 2024-11-12 08:06:09
Yawn
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On Nov 11, 2024, at 6:48 PM, Aijun Wang <wangaijun@xxxxxxxxxxxxxxx> wrote:
Hi, Robert and Mach:
Thanks for your comments on this document.
It reveals clearly the issues existing within the documents.
The Chairs declare repeatedly this document reached WG consensus, apparently it DOESN’T.
I have submitted the appeal to IESG.
Wish more experts to stand out to ABANDON this error prone, pitfall solution being published under the name of LSR, or IETF.
On Nov 12, 2024, at 06:55, Robert Raszuk <robert@xxxxxxxxxx> wrote:
Les,
> Link identifiers are indeed sub-TLVs.
> That does not disqualify them from being part of “key” information.
Oh, it was not clear from the draft. Perhaps you can add this detail in the next rev.
- - -
If you have multiple parallel links today they will all be listed in the sub-TLVs - so they are ok spec wise today.
I am not sure however - assuming you do not include "Example" in section 4.1 that everyone would be adding them to each TLV fragment.
// But then we have hackathons and interop venus where interop bugs can be quickly found and fixed
// if this is how it should all work out.
That is why I do believe a sort of dictionary would be nice to have in either a normative spec or reference to such a document or even as a simple wiki page :).
Best,
Robert
Robert –
Link identifiers are indeed sub-TLVs.
That does not disqualify them from being part of “key” information.
If I have multiple parallel links between two routers, this is how the links are uniquely identified. Such information is essential to correctly identify the link attribute information
which in turn is essential for applications such as RSVP-TE, SR=TE, and flex-algo to operate correctly.
If you think this is underspecified, I presume you think it is not possible for these applications to work correctly today – which obviously is not the case.
Les
I note that in all of these emails expressing concern no one has provided a single example
RFC5305 defines Extended IS Reachability TLV as:
The proposed extended IS reachability TLV contains a new data
structure, consisting of:
7 octets of system ID and pseudonode number
3 octets of default metric
1 octet of length of sub-TLVs
Now your draft makes an impression that there are also at the TLV level itself optional link identifiers.
4.1. Example: Extended IS Reachability
As an example, consider the Extended IS Reachability TLV (type 22).
A neighbor in this TLV is specified by:
* 7 octets of system ID and pseudonode number
* 3 octets of default metric
* Optionally one or more of the following link identifiers:
- IPv4 interface address and IPv4 neighbor address as specified
in [RFC5305]
- IPv6 interface address and IPv6 neighbor address as specified
in [RFC6119]
- Link Local/Remote Identifiers as specified in [RFC5307]
Can you point to the text in RFC5305 where such IPv4 link identifier is defined ?
I can only find them to be defined as part of sub-TLVs.
Also I do not see them as LSDB keys in FRR ISIS code ...
Speaking as WG member:
Dear Christian,
Thank you for your answer. I remain educated that LSR WG born RFCs are only for those who implement protocol and have years of experience in doing so.
I was obviously wrong thinking RFCs are designed to also help operators to run and troubleshoot network problems. Or maybe say wireshark or tcpdump developers to properly decode stuff which shows up on the wire ...
And if this is so obvious, what is the problem for someone with such experience to sit down and write down a BCP dict listing what in his opinions should be used as a key for each TLV listed in section 8.2 ? If done weeks before we would
not have such discussion.
If done correctly, this document would be welcomed. However, it should be a gating factor on specification of IS-IS MP-TLVs.
As was pointed out on the list, anyone implementing IS-IS knows exactly what a key is b/c it’s literally the value they use to differentiate TLVs from one another — IOW *A KEY VALUE*. You don’t consider 2 neighbor
TLVs to be different neighbors (and allocate a neighbor structure to store in your DB of neighbors) based on the TLV metric value. This really is obvious when people stop treating the discussion as some abstraction which is again what people keep pointing
out.
Thanks,
Chris.
> On Nov 11, 2024, at 08:13, Robert Raszuk <robert@xxxxxxxxxx> wrote:
>
> Hi Chris,
>
> > The WG explicitly decided it was inappropriate to have this document re-define
> > every "key" for every possible TLV as these "key" values are already defined
> > by the documents that define the TLV;
>
> I have followed this discussion on the list.
>
> It seems to be as a side observer that folks questioning the WGLC and progressing the document do have a valid point.
>
> The document by its title and by section 8.2 creates an impression that it is a universal spec for all TLVs in respect how to implement MP-TLVs for them.
>
> Yet we clearly see from examples provided in sections 4.1 and 4.2 that what constitutes a "key" is TLV dependent and it is really cherry picked out of the number of values carried in a TLV.
>
> An example from section 4.1: In TLV 22 - 3 octets of def metric is skipped and not considered as a key
>
> An example from section 4.2: In TLV 135 - 4 octets of metric information and two bits of control information octet are skipped and not considered as a key
>
> So if an implementer takes this document and attempts to write up MP-TLV how is he going to figure out which values for all other listed TLVs in 8.2 constitute a key and which not ?
>
> IMO this document can proceed however only in respect to TLV 22 and TLV 135 and both its title and content should reflect this.
>
> Cheers,
> Robert
>
> On Mon, Nov 11, 2024 at 1:27 PM Christian Hopps <chopps@xxxxxxxxxx> wrote:
>
> Mach Chen <mach.chen=40huawei.com@xxxxxxxxxxxxxx> writes:
>
> > Hello，
> >
> > I have been selected as the Routing Directorate reviewer for this draft. The
> > Routing Directorate seeks to review all routing or routing-related drafts as
> > they pass through IETF last call and IESG review, and sometimes on special
> > request. The purpose of the review is to provide assistance to the Routing ADs.
> > For more information about the Routing Directorate, please
> > see https://wiki.ietf.org/en/group/rtg/RtgDir
> >
> > Although these comments are primarily for the use of the Routing ADs, it would
> > be helpful if you could consider them along with any other IETF Last Call
> > comments that you receive, and strive to resolve them through discussion or by
> > updating the draft.
> >
> > Document:
https://datatracker.ietf.org/doc/draft-ietf-lsr-multi-tlv-06
> > Reviewer: Mach Chen
> > Review Date: 2024-11-11
> > IETF LC End Date:
> > Intended Status: Standards Track
> >
> > Summary:
> > • I have some major and minor concerns about this document that I think should be resolved before publication.
> >
> > Comments:
> > • The document is well written and easy to read it.
> >
> > Major Issues:
> > 1. The definitions of the 'Key' for TLVs and sub-TLVs vary, and this document
> > does not specify the Key for each MP-TLV. Therefore, it may result in
> > interoperability issues if implementations use different information to
> > construct the 'Key.' Given Section 8.2 listed all existing applicable MP-TLVs,
> > it's essential to specify the Key for each of those MP-TLVs, either within this
> > document or in a separate document to which this document should provide a
> > normative reference.
>
> Hi Mach,
>
> I'm curious if you also followed along on the extensive discussions on this exact issue on the LSR list or not?
>
> Understanding your exposure to this would help with how to address any remaining confusion about this directly in the draft.
>
> The WG explicitly decided it was inappropriate to have this document re-define every "key" for every possible TLV as these "key" values are already defined by the documents that define the TLV; however, documenting that choice and the reasoning better may
still be necessary.
>
> So my question is this: were you following along with this discussion in the LSR WG and find yourself disagreeing with the WG decision, or is this entire topic new to you?
>
> Thanks,
> Chris.
>
>
> >
> > Minor Issues:
> > 1. The MP-TLV Capability Advertisement is defined as a node-based capability
> > rather than on a per-codepoint basis, which limits its usefulness. In some
> > cases, it may even be misleading if operators just rely on this capability to
> > assume MP-TLV support. Therefore, it would be preferable to either remove this
> > capability advertisement or redefine it to operate on a per-codepoint basis.
> >
> > Best regards,
> > Mach
>
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