Subject: Re: PWE3 new WG items? PW QoS

From: Luca Martini <[email-masked]>
Date: Thu, 19 Feb 2004 08:50:57 -0700

Busschbach, Peter B (Peter) wrote:

[snip]

>I would agree that if QoS were the only problem that needs to be solved it could be acceptable to carry QoS information in the LDP messages that are used for PW setup (albeit that it is somewhat ugly since it makes LDP look like CR-LDP which has been depreciated).
>
>However, there are other issues that need to be solved. Several people on this mailing list suggested that we need to address PW stitching. It seems to me that stitching of PWs requires a signaling protocol that establishes a multi-hop PW through switches that switch based on the PW label. RSVP is in my view the only reasonable solution.
>
>Hence, if we don't look at one problem at a time, but at the entire problem space, I think we need to adopt RSVP as a way to establish PWs. It would solve the problems of both QoS and stitching.
>
>Peter
>
>  
>
Peter,
It is possible ( I already know of one implementation ) to select an 
RSVP LSP to transport a single PW.
That does not change the protocol , and does carry QoS information 
needed by the PSN. It also achieves another property that as it turns 
out is quite useful in practice: explicit routing of the PW across the 
PSN. ( this is for TE , but also other reasons like avoiding shared PSN 
failure modes )

Luca

>
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>  
>

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From: Wei Luo <[email-masked]>
Date: Thu, 19 Feb 2004 14:43:33 -0800

> Hence, if we don't look at one problem at a time, but at the entire problem space, I think we need to adopt RSVP as a way to establish PWs. It would solve the problems of both QoS and stitching.

Actually PW stitching can be implemented entirely using existing pseudowire 
signaling procedures (using LDP or L2TP) without any new protocol or extension. 
  The signaling protocol is not an issue.

With regard to PW stitching, this working group probably should focus on the 
operational issues with regard to PW stitching, such as whether Attachment 
Circuit interworking is needed at the stitching point, how to interwork between 
different PSN types, sequencing, multi-hop VCCV, Inter-AS considerations and 
other network management subjects.

---Wei

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From: Rahul Aggarwal <[email-masked]>
Date: Thu, 19 Feb 2004 18:26:07 -0800 (PST)

Hi Luca,

> PSN. ( this is for TE , but also other reasons like avoiding shared PSN

True. To take this one step further for scaling, one may want to transport
multiplePWs, signaled with QoS, in one transport LSP. If the PW is
signaled using RSVP-TE, and the PSN LSP is signaled using RSVP-TE, LSP
Hierarchy with Generalized MPLS TE (draft-ietf-mpls-lsp-hierarchy-08.txt),
can be used to carry the PW LSPs in the RSVP-TE PSN LSP.

rahul