Subject: RE: Multi-Hop Pseudo-Wires Signalling Using LDP

From: David McDysan <[email-masked]>
Date: Tue, 01 Feb 2005 10:27:55 -0500

Interesting draft. A few comments and questions below.

Dave

Agree that hierarchy is an important driver. Suggest reference of the
requirements I-D that describes the use cases for hierarchy in more detail.
draft-martini-pwe3-MH-PW-requirements-00.txt

Should additional parameters be encoded in a separate TLV instead of
augmenting the Generalized ID (GID) FEC already defined in
draft-ietf-pwe3-control-protocol-11.txt? This could ease interoperability
considerations.

The proposed next-Hop LSR ID TLV can be inferred from the LDP peer.
Therefore, is this TLV necessary? 

The proposed next-hop priority TLV could be learned from BGP (local pref) or
an IGP (metric) for the LDP peer. Therefore, is this TLV necessary?

Does the "Reflector" in section 4.1, simple trunk mode, need to withdraw
labels if a session with an LDP client fails?

A few comments on section 4.2, "nexthop self" mode. 

Suggest use of source/dest PE terminology defined at the end of section 1 to
improve readability throughout. Section 4.2 section uses terms such as
"far-end" and "dest," and references to a particular PE are sometimes
unclear later in the document.

The "reflector" described with reference to Figure 4-2 appears to be similar
to a PW Switching PE (S-PE) function in the terminology defined in
draft-martini-pwe3-MH-PW-requirements-00.txt where the PW FEC is the same
for all segments. Also, the S-PE determines the next hop toward the target,
as opposed to having to configure a "stitching" point.

The "reflector" described with reference to Figure 4-3 appears to be similar
to PW Stitching of SH PW segments, which may have different PW FECs and
different PSN tunnel types as described in
draft-martini-pwe3-pw-switching-01.txt. 

A unique aspect of the described approach is that the proposed extenstion to
PW LDP is used to "flood" the label binding from the source PE (i.e., the PE
distributing the PW label) to all "reflector" nodes until the target PE is
reached, creating the need for loop detection as described in section 9.
This has the consequence that PW labels and other resources (e.g., capacity
if that is signaled) are reserved on all possible PW paths. This could be
inefficient in some topologies or applications.

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On 
> Behalf Of Stewart Bryant
> Sent: Tuesday, February 01, 2005 4:07 AM
> To: pwe3
> Subject: [PWE3] Multi-Hop Pseudo-Wires Signalling Using LDP
> 
> 
> The following draft was recently posted:
> 
> Multi-Hop Pseudo-Wires Signalling Using LDP 
> draft-yudong-pwe3-control-protocol-ext-01.txt
> 
> Stewart
> 
> _______________________________________________
> pwe3 mailing list
> [email-masked]
> https://www1.ietf.org/mailman/listinfo/pwe3
>

---

From: Chris Metz <[email-masked]>
Date: Tue, 01 Feb 2005 09:14:17 -0800

I can only find the -00 rev of this draft.

http://www.ietf.org/internet-drafts/draft-yudong-pwe3-control-protocol-ext-00.txt

Is there a rev -01?

Thanks ...