Re: WGLC comments on bfd-mpls-05

Rahul Aggarwal <rahul@juniper.net> Thu, 08 May 2008 23:13 UTC

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Date: Thu, 8 May 2008 16:13:17 -0700 (PDT)
From: Rahul Aggarwal <rahul@juniper.net>
To: Carlos Pignataro <cpignata@cisco.com>
Subject: Re: WGLC comments on bfd-mpls-05
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Hi Carlos,

On Thu, 8 May 2008, Carlos Pignataro wrote:

> Hi Rahul, Tom,
>
> Please find some comments inline on the last point (down to one).
>
> On 5/7/2008 7:49 PM, Rahul Aggarwal said the following:
> > Hi Tom,
> >
> > Please see below:
> >
> > <snipped>
> >
> > <rahul>
> >> I don't think that makes sense as this document relies on
> >>> configuration.
>
> That's fine, but my point is that instead of configuration, this
> document (for the PW case) relies on the existence of a control channel
> and capability/ability/agreement to run LSP-Ping, which in turn can be
> preformed by configuration (or other means equally).
>

And those other means are out of scope. Seems like we are in agrement and
are saying the same thing. Let us not spin in wordsmithing.

> > tom>
> >> However, I think the confusion here lies in the fact that we could
> >> configure the capability, and then advertise the BFD/VCCV capability,
> >> right?
> >
> > This spec requires configuration and should just say that signaling of
> > capabilities is out of scope.
>
> Note that RFC5085 says:
>
>     Routers that implement VCCV create a Control Channel (CC) associated
>     with a pseudowire.  This control channel can be signaled (e.g., using
>     LDP or L2TPv3 depending on the PWE3) or statically configured.  Over
>     this control channel, VCCV Connectivity Verification (CV) messages
>     are sent.
>
> I mean (and I may not have been clear), not to signal capabilities for
> the procedures in this spec, but the configuration or signaling
> pre-requisite (and hence Normative for PWs) to start those procedures in
> this document (with LSP-Ping over the PW control channel).
>
> For the PW case specifically,  a control channel needs to exist prior to
> OAM messages. This dependency can be realized by configuration or
> signaling. For example, the text says as an example use TTL=1 or:
>

And this spec requires configuration. That is it.

>     For MPLS PWs, alternatively,
>     the presence of a fault detection message may be indicated by setting
>     a bit in the control word [VCCV].
>
> But to use this method, it needs to be signaled or configured as per
> RFC5085, otherwise OAMs could potentially be not intercepted and
> forwarded to the CE. The TTL=1 listed is another control channel type
> from RFC5085.
>

And the revised text that I had sent makes it clear that this needs to be
configured.

> >
> > tom>
> >> But those are explicitly detailed in the vccv-bfd document
> >> (draft-ietf-pwe3-vccv-bfd-01).  It might be most appropriate to simply
> >> remove the forward reference to the vccv-bfd stuff from here, and only
> >> refer to this document from there.
> >>
> >
> > How about removing the forward reference to draft-ietf-pwe3-vccv-bfd-01.
> > But leaving the reference to RFC5085 to say that there could be
> > other ways to identify OAM packets other than ttl=1, for PWs ?
>
> Note that TTL=1 for PWs is one of the RFC5085 control channels, so it
> seem that RFC5085 is needed to bootstrap:
>
>           Bit 2 (0x04) - Type 3: MPLS PW Label with TTL == 1
>

See above note on configuration.

> But regarding this forward pointer, my preference would be to leave it
> in (for completeness and cross-reference) in the same context as the
> existing text:
>
> 	"Use of BFD for PWs is further described in [VCCV-BFD] and
> 	[OAM-MAP].".
>

Based on Tom's comment, I am inclined to keep only RFC5085 as an
informative reference, unless I hear more opinions on this.

I will produce a revised ID. Thanks for the comments.

rahul

> Thanks,
>
> --Carlos.
>
>
> > And let
> > that be an informative reference ?
> >
> > rahul
> >
>
> --
> --Carlos Pignataro.
> Escalation RTP - cisco Systems
>