Subject: Re: [Idr] Signalling ERLD (ISIS, OSPF and BGP-LS)

From: Jeff Tantsura <[email-masked]>
Date: Wed, 13 Jun 2018 14:09:22 -0700

Gunter,

I have nothing to add to Les' comments, 100% agree.

Cheers,
Jeff
On 6/13/18, 08:42, "Idr on behalf of Les Ginsberg (ginsberg)" <[email-masked] on behalf of ginsberg=[email-masked]> wrote:

    Gunter -
    
    I strongly support Option #2 and strongly support Ketan's recommendation that an MSD sub-type be used to advertise ERLD.
    This is the unified framework that the MSD advertisement has been designed to support.
    
    The following documents provide a unified definition of this mechanism:
    
    https://datatracker.ietf.org/doc/draft-ietf-isis-segment-routing-msd/
    https://datatracker.ietf.org/doc/draft-ietf-ospf-segment-routing-msd/
    https://datatracker.ietf.org/doc/draft-ietf-idr-bgp-ls-segment-routing-msd/
    
    (The last one needs a refresh.)
    
    If we can update the related ERLD documents to align I think we will have an excellent solution.
    
     (Note: in the case of https://datatracker.ietf.org/doc/draft-ietf-idr-bgp-ls-segment-routing-rld/ perhaps that can be combined with https://datatracker.ietf.org/doc/draft-ietf-idr-bgp-ls-segment-routing-msd/  - but I leave that to the respective authors to work out.)
    
       Les

    > -----Original Message-----
    > From: Lsr <[email-masked]> On Behalf Of Van De Velde, Gunter (Nokia
    > - BE/Antwerp)
    > Sent: Wednesday, June 13, 2018 2:10 AM
    > To: Ketan Talaulikar (ketant) <[email-masked]>; [email-masked]; [email-masked];
    > [email-masked]
    > Subject: Re: [Lsr] Signalling ERLD (ISIS, OSPF and BGP-LS)
    > 
    > It is desirable that same understanding of TLVs ([ELC, RLD] or [ERLD]) are
    > signaled for ISIS, OSPF and BGP-LS.
    > 
    > If the WG's can manage to agree upon a decision (option1/2/3 or 4), then
    > next, have a look into how to encode the TLV so that we have a clean
    > technological solution space.
    > 
    > G/
    > 
    > -----Original Message-----
    > From: Ketan Talaulikar (ketant) [mailto:[email-masked]]
    > Sent: Wednesday, June 13, 2018 10:45
    > To: Van De Velde, Gunter (Nokia - BE/Antwerp)
    > <[email-masked]>; [email-masked]; [email-masked];
    > [email-masked]
    > Subject: RE: Signalling ERLD (ISIS, OSPF and BGP-LS)
    > 
    > Hi Gunter,
    > 
    > In that case, I concur with you that option (2) is better than the others. My
    > only difference in opinion is that ERLD not have its own separate TLV but
    > instead get advertised as a new MSD sub-type - it is just a different encoding.
    > 
    > Thanks,
    > Ketan
    > 
    > -----Original Message-----
    > From: Van De Velde, Gunter (Nokia - BE/Antwerp)
    > <[email-masked]>
    > Sent: 13 June 2018 13:55
    > To: Ketan Talaulikar (ketant) <[email-masked]>; [email-masked]; [email-masked];
    > [email-masked]
    > Subject: RE: Signalling ERLD (ISIS, OSPF and BGP-LS)
    > 
    > Indeed, the debate that made BGP-LS to go down the ERLD path is of
    > pragmatic motivation.
    > 
    > The major Readable Label Depth use-case is entropy. Hence, if the ERLD TLV
    > is available, then ELC can be implicitly assumed. No pragmatic reason to signal
    > separately, as it just make things more complex then should be.
    > 
    > >From a holistic perspective having something similar, yet different, in both
    > IGP and BGP-LS encoding seems to make little sense and only bring
    > confusion (router/controller implementers and network operators).
    > 
    > The ways to address this in IGP and BGP-LS going forward:
    > 1) do nothing and leave all as it is (it has potential to create massive
    > confusion)
    > 2) only signal ERLD TLV in IGP and BGP
    > 3) signal ELC TLV and RLD TLV (unclear pragmatic value of explicit signaling of
    > ELC TLV compared to option (2))
    > 4) signal ELC TLV, RLD TLV and ERLD TLV (it has all, but is much much more
    > complex as option (2))
    > 
    > I believe that option (2) is the best option:
    > * it bring the needed readable label depth value to operators
    > * most simple solution for implementers (routers and controller)
    > * easy to understand with no confusion
    > * is compliant with draft-ietf-mpls-spring-entropy-label-10
    > 
    > G/
    > 
    > -----Original Message-----
    > From: Ketan Talaulikar (ketant) [mailto:[email-masked]]
    > Sent: Wednesday, June 13, 2018 08:05
    > To: Van De Velde, Gunter (Nokia - BE/Antwerp)
    > <[email-masked]>; [email-masked]; [email-masked];
    > [email-masked]
    > Subject: RE: Signalling ERLD (ISIS, OSPF and BGP-LS)
    > 
    > Hi Gunter,
    > 
    > The difference in IGP signalling seems to be because the ELC is a capability
    > which is advertised differently than ERLD which is a limit. Are you saying that
    > ELC does not have value by itself without the ERLD?
    > 
    > IMHO it makes sense to retain ELC as capability of the router (as specified in
    > the IGP specs) and position ERLD as a MSD sub-type for indicating the limit.
    > This way we have the flexibility of signalling ERLD both per node and per
    > ingress link/LC level.
    > 
    > Thanks,
    > Ketan
    > 
    > -----Original Message-----
    > From: Idr <[email-masked]> On Behalf Of Van De Velde, Gunter (Nokia
    > - BE/Antwerp)
    > Sent: 12 June 2018 19:28
    > To: [email-masked]; [email-masked]; [email-masked]
    > Subject: [Idr] Signalling ERLD (ISIS, OSPF and BGP-LS)
    > 
    > In LSR WG the following drafts document the signaling of ELC and RLD:
    > * draft-ietf-ospf-mpls-elc
    > * draft-ietf-isis-mpls-elc
    > 
    > When exporting this information using BGP-LS encoding to a controller, there
    > is need for BGP-LS extension by means of new TLVs.
    > 
    > BGP-LS is signaling ERLD (entropy capable readable label depth) ISIS/OSPF is
    > signaling individually ELC and RLD
    > 
    > I was working upon the IANA section, and discovered some inconsistency
    > that should be addressed:
    > * Why is IGP signaling individual ELC and RLD? ERLD is what was decided upon
    > (https://tools.ietf.org/html/draft-ietf-mpls-spring-entropy-label-10)
    > * What are the plans to request IANA code points for these drafts?
    > * (E)RLD seems to have meaning only from NODE perspective, (I assume that
    > LINK ERLD is not of any value at all, is that a correct assumption?)
    > 
    > G/
    > 
    > 
    > -----Original Message-----
    > From: Idr [mailto:[email-masked]] On Behalf Of internet-
    > [email-masked]
    > Sent: Tuesday, June 12, 2018 15:25
    > To: [email-masked]
    > Cc: [email-masked]
    > Subject: [Idr] I-D Action: draft-ietf-idr-bgp-ls-segment-routing-rld-02.txt
    > 
    > 
    > A New Internet-Draft is available from the on-line Internet-Drafts directories.
    > This draft is a work item of the Inter-Domain Routing WG of the IETF.
    > 
    >         Title           : Signalling ERLD using BGP-LS
    >         Authors         : Gunter Van de Velde
    >                           Wim Henderickx
    >                           Matthew Bocci
    >                           Keyur Patel
    > 	Filename        : draft-ietf-idr-bgp-ls-segment-routing-rld-02.txt
    > 	Pages           : 6
    > 	Date            : 2018-06-12
    > 
    > Abstract:
    >    This document defines the attribute encoding to use for BGP-LS to
    >    expose ERLD "Entropy capable Readable Label Depth" from a node to a
    >    centralised controller (PCE/SDN).
    > 
    > 
    > 
    > The IETF datatracker status page for this draft is:
    > https://datatracker.ietf.org/doc/draft-ietf-idr-bgp-ls-segment-routing-rld/
    > 
    > There are also htmlized versions available at:
    > https://tools.ietf.org/html/draft-ietf-idr-bgp-ls-segment-routing-rld-02
    > https://datatracker.ietf.org/doc/html/draft-ietf-idr-bgp-ls-segment-routing-
    > rld-02
    > 
    > A diff from the previous version is available at:
    > https://www.ietf.org/rfcdiff?url2=draft-ietf-idr-bgp-ls-segment-routing-rld-
    > 02
    > 
    > 
    > Please note that it may take a couple of minutes from the time of submission
    > until the htmlized version and diff are available at tools.ietf.org.
    > 
    > Internet-Drafts are also available by anonymous FTP at:
    > ftp://ftp.ietf.org/internet-drafts/
    > 
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