Re: [Isis-wg] WG Adoption Call for draft-xu-isis-encapsulation-cap

["Les Ginsberg (ginsberg)" <[e-mail]>]

Hannes -

Discovery of tunnel endpoints is not what this draft is about. 

I am saying that I do not see that announcing tunnel capabilities is useful. Discovering tunnel endpoints obviously is useful - as is identifying endpoint addresses - but this draft will help us do neither.

   Les


> -----Original Message-----
> From: Hannes Gredler [mailto:[e-mail]]
> Sent: Saturday, February 27, 2016 9:52 AM
> To: Les Ginsberg (ginsberg)
> Cc: Uma Chunduri; Christian Hopps; [e-mail] list
> Subject: Re: [Isis-wg] WG Adoption Call for draft-xu-isis-encapsulation-cap
> 
> hi les,
> 
> <wg-chair hat off>
> 
> On Sat, Feb 27, 2016 at 05:18:39PM +0000, Les Ginsberg (ginsberg) wrote:
> |    From my POV the draft currently defines how to advertise new
> |    information without defining why it is necessary to do so.
> 
> agree - "discovery of tunnel endpoints" should be explicitly spelled out.
> 
> |
> |    Yes, multiple tunnel types may be in use in the network - that does not
> |    in and of itself lead to a requirement to advertise supported tunnel
> |    types . In most cases, the support of a given tunnel type can be known
> |    today by other means. You give the example of RLFA - but today LDP
> |    reachability to an endpoint is something a router already knows - and
> |    this is the real requirement to setup an RLFA tunnel. Knowing that the
> |    endpoint is capable of supporting RLFA is insufficient. Further, folks
> |    (including you if I recall correctly) have indicated that they want
> |    more than just knowing RLFA capability - they also want to know what
> |    endpoint address to use. This logically leads to the use of admin tags
> |    which will not only indicate support for the tunnel type but also what
> |    endpoint address is preferred/required.
> 
> guess the RLFA example refers to non-MPLS (IP-only deployments)
> 
> |    I think more thought and discussion is required before deciding that
> |    this is something that should be supported. And I think this needs to
> |    be done BEFORE this becomes a WG document as - almost without
> exception
> |    - anything that becomes a WG document proceeds to become an RFC.
> 
> IMO the generic ability to discover tunnel-endpoints is something desireable.
> agreed that the actual use-cases should be (better) documented
> somewhere (perhaps in RTGWG ?), but we can do that after WG adoption as
> well.
> 
> - or is it that you want to make a case that discovery of tunnel endpoints is
> not desired at all ?
> 
> /hannes
> 
> |    From: Uma Chunduri [mailto:[e-mail]]
> |    Sent: Friday, February 26, 2016 12:09 PM
> |    To: Uma Chunduri; Les Ginsberg (ginsberg); Christian Hopps;
> |    [e-mail] list
> |    Subject: RE: [Isis-wg] WG Adoption Call for
> |    draft-xu-isis-encapsulation-cap
> |
> |
> |    Dear Les et. al,
> |
> |
> |    Please post any further comments you might have on this document.
> |
> |
> |    --
> |
> |    Uma C.
> |
> |
> |    From: Isis-wg [[1]mailto:[e-mail]] On Behalf Of Uma
> |    Chunduri
> |    Sent: Thursday, January 14, 2016 4:51 PM
> |    To: Les Ginsberg (ginsberg); Christian Hopps; [2][e-mail] list
> |    Subject: Re: [Isis-wg] WG Adoption Call for
> |    draft-xu-isis-encapsulation-cap
> |
> |
> |    Les,
> |
> |
> |    Thanks for your comments, see in line [Uma]:
> |
> |    --
> |
> |    Uma C.
> |
> |
> |    From: Isis-wg [[3]mailto:[e-mail]] On Behalf Of Les
> |    Ginsberg (ginsberg)
> |    Sent: Tuesday, January 12, 2016 5:25 PM
> |    To: Christian Hopps; [4][e-mail] list
> |    Subject: Re: [Isis-wg] WG Adoption Call for
> |    draft-xu-isis-encapsulation-cap
> |
> |
> |    Apologies for the very late response on this...
> |
> |
> |    I have a couple of concerns regarding taking on this work.
> |
> |
> |    The draft is straightforward enough in terms of the protocol extensions
> |    defined, but I am not at all clear on the usefulness of the information
> |    being advertised. The introduction to the draft discusses a variety of
> |    tunnel types which might be used in a network but does not offer an y
> |    reason why advertising the tunnel types supported is of benefit.
> |
> |
> |    [Uma]: Lot of use cases have been described where there is no
> |    configuration possible for all possible egress nodes at a given ingress
> |    node; as asymmetric connections can be made dynamically based on the
> |    network topology; using the tunnel capabilities or parameters of egress
> |    node  from ingress.
> |
> |
> |    Given this information is only advertised within a single
> |    administrative domain it does not seem to provide any information that
> |    is not already known to the network operator.
> |
> |    [Uma]: This is not about whether network operators know all the
> |    information but it's about if it is possible to configure/manage
> |
> |    a.       all options supported by possible egress nodes from ingress
> |    nodes perspective or
> |
> |    b.      one option of all "possible" egress nodes from ingress nodes
> |    pov.
> |
> |
> |    It also logically leads to requiring a configuration for what tunnel
> |    types to advertise. If this information is meant to drive automatic
> |    configuration of tunnels I presume that the network operator would want
> |    to limit what is advertised - not simply accept what the implementation
> |    is capable of supporting. So it seems we have simply traded one
> |    configuration for another.
> |
> |    [Uma]: I don't see, we have traded any configuration here. An in-line
> |    ingress application/feature  running as part of IS-IS ought to know
> |    what kind of tunnel capabilities the egress node is capable of
> |    accepting and associated parameters thereof for that tunnel.  Network
> |    operator can always limit enabling  capabilities that are being
> |    supported and capabilities that are being advertised by an egress node
> |    as part of ISIS through configuration.
> |
> |
> |    I would like to see more detail on this before deciding whether it is
> |    worth doing.
> |
> |
> |    It is clear that the information is not at all useful to IS-IS itself -
> |    which brings me to my second concern. This is advertising information
> |    that has nothing to with IS-IS. Router Capabilities is not meant to be
> |    used as a vehicle to advertise information not of direct use to the
> |    protocol.
> |
> |    [Uma]:  I am not sure why you see it is not all useful to IS-IS ; most
> |    of the features/applications listed in  section 1 are related to  ISIS
> |    protocols. For example RLFA- computation of PQ nodes done after
> primary
> |    SPF and as part of RLFA  SPFs (neighbor SPF, neighbors rSPF) and PQ
> |    nodes are computed dynamically on the current topology. It's not
> |    conceivable to provision an ingress node with one/all tunnel
> |    capabilities of egress nodes (essentially where ever this feature is
> |    enabled and potentially all eventually).  Similarly for Spring/Bier
> |    nodes dynamic tunnels can be supported based on the neighboring
> |    non-spring/non-bier node capabilities advertised.
> |
> |
> |    In fact, the existence of a couple of exceptions to this guideline is
> |    what prompted the creation of GENAPP (RFC 6823) as the appropriate
> |    place to advertise such information.
> |
> |
> |    I would like to see further discussion of the above before deciding
> |    that WG adoption (which almost always indicates an intent to progress
> |    to RFC) is appropriate.
> |
> |
> |        Les
> |
> |
> |
> |    From: Isis-wg [[5]mailto:[e-mail]] On Behalf Of
> |    Christian Hopps
> |    Sent: Monday, November 30, 2015 11:45 PM
> |    To: [6][e-mail] list
> |    Subject: Re: [Isis-wg] WG Adoption Call for
> |    draft-xu-isis-encapsulation-cap
> |
> |
> |    [It seems due to some sneaky cut and paste error, the URL was wrong in
> |    the original email, I've corrected in this message]
> |
> |
> |    Hi Folks,
> |    The authors have requested the IS-IS WG adopt:
> |
> |
> |
> | [7]https://datatracker.ietf.org/doc/draft-xu-isis-encapsulation-cap/
> |
> |
> |    as a working group document.
> |
> |    Please indicate support or no-support for taking on this work.
> |    Thanks,
> |    Chris.
> |
> | References
> |
> |    1. mailto:[e-mail]
> |    2. mailto:[e-mail]
> |    3. mailto:[e-mail]
> |    4. mailto:[e-mail]
> |    5. mailto:[e-mail]
> |    6. mailto:[e-mail]
> |    7.
> | https://datatracker.ietf.org/doc/draft-xu-isis-encapsulation-cap/
> 
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