Re: [PWE3] PWE3 new WG items? PW QoS

[Scott W Brim <sbrim at cisco.com>]

Busschbach, Peter B (Peter) allegedly wrote on 2/20/2004 10:15:

>>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.
>>    
>>
>
>Hi Wei,
>
>I respectfully disagree. The fact that we have a signaling protocol to set up single PW segments doesn't mean that it is clear how to establish multi-segment PWs. 
>
You're both right depending on clarification and problem scoping.  We
know how to set up multiple PWs, and "stitching" them might be purely a
PE issue.  However, whether that solves the problem or not depends on
the answers to your questions (and others). 

>- Are segments set up in a random order or is there a need for a certain sequence of message?
>  
>
For scaling and robustness you can't require a certain order of setup.

>- Is it necessary to use the same values for Interface Parameters on each segment?
>
>- Is VCCV used on single segments or end-to-end? If the latter, do intermediate points monitor or do they blindly forward the packets?
>
>- In case a segment goes down, are alarm signals sent to the end-points of the multi-segment PW or is the error handled locally?
>  
>
PW-specific alarms should be constrained to just the extent of that
particular PW.  Alarms for protocols that use that PW obviously extend
further.

>All these, and probably more, need to be specified. On the other hand, if we decide that a multi-segment PW is essentially an LSP that can be set up with RSVP-TE, the RSVP-TE spec provides most of the answers.
>  
>
Unlikely :-). 

swb

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