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

[Hannes Gredler <[e-mail]>]

hi les,

On 2/27/16 19:28, Les Ginsberg (ginsberg) wrote:
> 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.

agreed - IP prefix info is missing ...
i can see two ways to fix this:

1. explicitly state that the tunnel-encaps-cap refers to a particular
    IP prefix
2. move the tunnel-encaps-cap underneath an IP prefix TLV

we should be good the, right ?

/hannes

>
>> -----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/
>>
>> | _______________________________________________
>> | Isis-wg mailing list
>> | [e-mail]
>> | https://www.ietf.org/mailman/listinfo/isis-wg
>