To add to Les’s point of BGP only scenario, during MSD IESG reviews, BGP-LS only deployment was found not well characterized and had been removed from the draft. It will require much better discussion to have it included.
Regards, Jeff > On Nov 13, 2020, at 15:57, Les Ginsberg (ginsberg) <[email protected]> wrote: > > > The points which Ketan has made regarding the use of MTU advertisements > defined in RFC 7176 are very valid. Indeed, the contents of the sub-TLV > defined in https://www.rfc-editor.org/rfc/rfc7176.html#section-2.4 depend > upon the TRILL specific MTU-probe/MTU-ack procedures defined in > https://www.rfc-editor.org/rfc/rfc6325#section-4.4.3. These procedures are > not currently applicable to non-TRILL environments. > > So, there are no existing IGP advertisements defined which can support the > goals of this draft. > > As Ketan has also indicated, there is no discussion in the draft of how a BGP > only network (for example) could provide the information of interest. > > From my perspective, WG adoption of this draft in ANY WG is premature. > This might be a useful functionality to have – but at the moment we simply > have an idea with no definition of how to implement/deploy it. > > So I therefore oppose WG adoption of this draft by IDR. > > Continuing the discussion is certainly useful – and I would encourage the > current authors to investigate and propose relevant mechanisms in all the > protocols of interest in some future version of the draft. > At that point we could then have a far more meaningful WG adoption call. > > Les > > > From: Idr <[email protected]> On Behalf Of Ketan Talaulikar (ketant) > Sent: Friday, November 13, 2020 1:35 AM > To: Susan Hares <[email protected]>; 'Jeff Tantsura' <[email protected]>; > 'Stephane Litkowski (slitkows)' <[email protected]>; > [email protected]; 'Acee Lindem (acee)' <[email protected]> > Cc: [email protected] > Subject: Re: [Idr] WG Adoption for draft-zhu-idr-bgp-ls-path-mtu (11/1/2020 > to 11/16/2020) > > Hi Authors, > > I believe this work is useful and should be taken up. It has value in > providing the link MTU as part of the topology information via BGP-LS. > However, as pointed out by others on this thread, the draft should remain > scoped to just that – i.e. providing link MTU information. The discussion > related to Path MTU and applicability to SR networks are best left outside > the scope of this standards track draft. > > Hi Sue, > > I would support the points made by Acee for not taking up this draft in IDR > WG and instead doing this in LSR. > > Besides the missing coverage for OSPFv2/v3, there are also issues with how > this would work with ISIS. The reference to the ISIS Trill specification > points to this TLV https://tools.ietf.org/html/rfc7176#section-2.4 – if you > see, there is more here than just the MTU value. What is more critical is the > ISIS procedures (in non-Trill deployments) on how this value is determined. > Please do not mix the following : > > The MTU sub-TLV is used to optionally announce the MTU of a link as > specified in [RFC6325], Section 4.2.4.4. > > Are the authors trying to specify that these Trill procedures for testing MTU > need to be adopted for regular ISIS deployments. > > My take is that while the ISIS TLV defined for Trill may be re-used in normal > ISIS deployments, its usage and procedures need to be specified. Copying the > LSR WG so that I may be corrected if I am wrong here. > > Coming to the point of BGP-only networks, the draft has zero text related to > that scenario. Moreover, the procedures for BGP-LS advertisements in BGP only > fabric need to be specified as a base. The > https://datatracker.ietf.org/doc/draft-ketant-idr-bgp-ls-bgp-only-fabric/ was > my attempt to specify those procedures and it would be great if the IDR WG > could review and provide feedback to this document and consider for adoption > so we can cover the BGP-only networks. > > I would also like to offer support/help to the authors in adding the > necessary OSPFv2/v3 support for the same in an LSR draft where we could > tackle both the IGPs and BGP-LS encoding and procedures together. > > Thanks, > Ketan > > From: Idr <[email protected]> On Behalf Of Susan Hares > Sent: 13 November 2020 00:20 > To: 'Jeff Tantsura' <[email protected]>; 'Stephane Litkowski > (slitkows)' <[email protected]>; [email protected]; 'Acee > Lindem (acee)' <[email protected]> > Subject: Re: [Idr] WG Adoption for draft-zhu-idr-bgp-ls-path-mtu (11/1/2020 > to 11/16/2020) > > Jeff and Authors of draft-zhu-idr-bgp-ls-path-mtu: > > I do believe the authors agreed to renaming the draft. > > Does the name: draft-xxx-idr-bgp-ls-link-mtu work for > the authors and interested IDR participants. > > As the end of 12 days of the 14 day WG LC, this draft appears > to have general consensus from the WG as a useful draft. > > I plan to allow 2 more days of comment, but at this point > it appears the WG wishes to adopt this draft. > > Here’s my understanding of the best way forward: > > If LSR adopts a version of the draft, IDR will allow the > LSR WG to be the main source as long as cross-working > review occurs so the BGP-only function can be reviewed. > > Please continue to comment on the draft and > the planned progression. > > Cheers, Sue > > From: Jeff Tantsura [mailto:[email protected]] > Sent: Thursday, November 12, 2020 12:53 PM > To: Susan Hares; Stephane Litkowski (slitkows); [email protected]; Acee Lindem > (acee) > Subject: Re: [Idr] WG Adoption for draft-zhu-idr-bgp-ls-path-mtu (11/1/2020 > to 11/16/2020) > > +1 to everything Acee said > > Cheers, > Jeff > On Nov 10, 2020, 1:01 PM -0800, Acee Lindem (acee) > <[email protected]>, wrote: > > Speaking as an IDR WG member: > > The name of the draft is wrong – the extension is for a Link MTU and not a > path MTU. > > Speaking as LSR Chair: > > We could this in LSR as there is currently no MTU advertisement in the LSAs > for OSPFv2 and OSPFv3. Implementations already make use of this information > as it is used in the OSPF DBD packets and for LSA packing. Of course, we’d > require a more accurate draft name and title. > > Thanks, > Acee > > From: Idr <[email protected]> on behalf of Susan Hares <[email protected]> > Date: Monday, November 9, 2020 at 4:20 PM > To: "'Stephane Litkowski (slitkows)'" <[email protected]>, > IDR List <[email protected]> > Subject: Re: [Idr] WG Adoption for draft-zhu-idr-bgp-ls-path-mtu (11/1/2020 > to 11/16/2020) > > Stephane: > > My second message to this thread asked a few questions about the technology. > > > This information can be more than IGP information. If SR segments > statically defined (static or direct interfaces) tunnels and pass the > endpoints via BGP tunnel-encaps draft with SR Policy tunnel type, this can > just be BGP. > > I’ll keep this WG adoption call going until we can be sure if: 1) it > something LSR wants to standardize, and 2) whether there is a BGP only case. > It is clear to me that standardizing MTU for a SR segments with stacked > tunnel segments passed by BGP was useful. > > The authors should be the ones to propose this in LSR. > > Cheers, Sue > > From: Idr [mailto:[email protected]] On Behalf Of Stephane Litkowski > (slitkows) > Sent: Monday, November 9, 2020 4:28 AM > To: Susan Hares; [email protected] > Subject: Re: [Idr] WG Adoption for draft-zhu-idr-bgp-ls-path-mtu (11/1/2020 > to 11/16/2020) > > Hi Sue, > > > The purpose behind this mechanism is to reduce administrative work rather > > than to reduce the review on drafts. > > That’s exactly my point. If we don’t do OSPF extension now and in the same > draft, we leave a gap that will require a new draft for a very very small > extension. Just adds process overhead for nothing… > > > Stephane > > > From: Susan Hares <[email protected]> > Sent: lundi 9 novembre 2020 10:10 > To: Stephane Litkowski (slitkows) <[email protected]>; [email protected] > Subject: RE: [Idr] WG Adoption for draft-zhu-idr-bgp-ls-path-mtu (11/1/2020 > to 11/16/2020) > > Stephane: > > I want to pick up on your email from two points: > > 1) Why not do everything in LSR? > <WG-chair hat> > If the feature comes with interest in doing all 3 (ISIS, OSPF, and BGP-LS > data gathering), then the authors may select to do everything in LSR rather > than have 2 or 3 drafts to maintain. > > This is optional and the mechanism may not fit every draft. The drafts may > also start out adopted and vetted in LSR and IDR. The purpose behind this > mechanism is to reduce administrative work rather than to reduce the review > on drafts. > > </wg-chair hat off> > > > 2) TRILL implementations of IS-IS has some MTU subTLV - > > If you are interested in whether this has been implemented in TRILL, you > might want to check with Donald Eastlake. My vague and foggy recollection > is that had some implementations or came from pre-TRILL implementations. > > > Cheers, Susan Hares > > > > From: Stephane Litkowski (slitkows) [mailto:[email protected]] > Sent: Wednesday, November 4, 2020 3:03 AM > To: Susan Hares; [email protected] > Subject: RE: [Idr] WG Adoption for draft-zhu-idr-bgp-ls-path-mtu (11/1/2020 > to 11/16/2020) > > Hi, > > “a) Are there ways to pass IGP link MTUs in > the IGPs? If so, is this needed in BGP-LS” > > This is a valid point, most of the time BGP-LS is feeded by IGP LSDBs (of > course there are other ways too). While I see that IS-IS has some MTU subTLV > coming from TRILL RFC7176 (possibly never been implemented), I don’t see > anything for OSPF (I’m not an OSPF expert, so I may have missed it). > Shouldn’t this be checked and validated with LSR WG before adopting ? > > > Stephane > > > From: Idr <[email protected]> On Behalf Of Susan Hares > Sent: lundi 2 novembre 2020 06:04 > To: [email protected] > Subject: [Idr] WG Adoption for draft-zhu-idr-bgp-ls-path-mtu (11/1/2020 to > 11/16/2020) > > This begins a 2 week WG adoption call for > draft-zhu-idr-bgp-ls-path-mtu-04.txt (11/1 – 11/16/2020). > > The authors should send in an IPR statement for this draft > by 11/5 so the WG can include the IPR status in their decision. > > You can access the draft at: > https://datatracker.ietf.org/doc/draft-zhu-idr-bgp-ls-path-mtu/ > > Since this draft is reference by an existing IDR draft > I’ve included a bit of background below to help you place > this draft into the larger context of the SR additions to BGP-LS > and the draft-ietf-idr-tunnel-encaps-19.txt. > > This draft does continue BGP-LS additions. if you > are opposed to any BGP-LS additions rather than > this specific addition, please make that clear in your > comment in this discussion. > > The authors requested a WG adoption at IETF 108. > The IDR co-chairs thank the authors for their patience. > This draft has been delayed by process of having a > new document shepherd (Sue Hares) come up to speed > on draft-ietf-idr-tunnel-encapsulation. > > Cheers, Sue > > Background > =========== > Segment Routing technology creates SR tunnels that are > directly overlaid on MPLS or SRv6. While existing MPLS technology > (LDP and RSV-TE) provides mechanisms to negotiate path MTU > based on individual link MTU limits, the Segment Routing (SR) > on BGP-LS Link Attribute does not pass information on > MTU size per link. > > draft-ietf-idr-sr-policy-path-mtu-02.txt sends PATH MTU > information in the tunnel-encapsulation attribute for the tunnel type > SR-Policy that handles segment routing (SR) paths. > However, it lacks the information to create a reasonable > Path size since the BGP-LS Link Attribute does distribute > this information. > > The draft proposes adding a new sub-TLV for MTU size > to the BGP-LS Link Attribute TLV, and > draft-ietf-idr-sr-policy-path-mtu-02.txt mentions this > draft as one possible way to distribute the per link > MTU. > > Questions for the authors might be: > a) Are there ways to pass IGP link MTUs in > the IGPs? If so, is this needed in BGP-LS > > b) What other mechanisms pass link MTU? > > > > > > > > _______________________________________________ > Idr mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/idr
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