RE: I-D ACTION:draft-takacs-asym-bw-lsp-00.txt

["Attila Takacs \(IJ/ETH\)" <Attila.Takacs@ericsson.com>]

Hi all,

Please see inline.
Regards,
Attila 

> -----Original Message-----
> From: owner-ccamp@ops.ietf.org 
> [mailto:owner-ccamp@ops.ietf.org] On Behalf Of Adrian Farrel
> Sent: Saturday, March 03, 2007 1:11 AM
> To: Don Fedyk; Dimitri.Papadimitriou@alcatel-lucent.be
> Cc: ccamp@ops.ietf.org
> Subject: Re: I-D ACTION:draft-takacs-asym-bw-lsp-00.txt
> 
> Cutting to the chase (I hope):
> 
> >>-> btw, where this requirement come from ?
> > [DF] Specifically GMPLS control of Ethernet.
> >
> >
> > [dp] i think i should be more precise WHY this specific req ?
> > is that specific to Ethernet ?
> 
> 1.a. Do we have a clear requirement for an asymmetrical 
> bidirectional service?
> 
> 1.b. Do we have a clear requirement for asymmetrical 
> bidirectional LSPs?
> (Does 1.b follow from 1.a?)
> 

It would be good to have operators reflect on these. My two cents are
that asymmetrical bidirectional services are apparently there. In
regards to LSPs carrying highly aggregated traffic in backbones
asymmetry might be of less importance, however LSPs getting further out
to the edges of the network may have really asymmetrical loads.

> > [dp] the issue is threefold
> >
> > a) you will see from the above that asym bi-dir LSP do not 
> call for an 
> > upstream tspec
> 
> 2. If 1.b, what should we use on a Path message to indicate 
> the bandwidth of the forward flow.
> 2.a. an 'upstream' TSpec
> 2.b. a FlowSpec
> 

I agree with Don and Igor on this. Having a TSpec there and ending up
with "single-sided" LSP control would be not a problem in practice.


> > b) the gain compared to the cost of having a real bi-dir.
> > setup is so low that setting unidir LSP is simpler
> >
> > c) but there is an operational issue in linking two LSPs
> > (asymmetric) together that one could think of associating them, we 
> > have a very efficient technique for this, that does not impact 
> > intermediate nodes (ASSOCIATION object) and provides for full 
> > flexibility (common or diverse spatial path for the upstream and 
> > downstream flow)
> 
> 3. Even if 1.b. we can consider:
> 3.a. A single signaling exchange for both directions 3.b. Two 
> 'associated' signaling exchanges
> 
> Personally, I think that the discussion is confused by 
> talking about "bidirectional LSPs". The issue really seems to 
> revolve around the signaling exchanges. The data plane 
> presence can be established identically by 3.a. or 3.b.

Agree. The target of the ID was to have a discussion on the topic and
see if there is interest to add a new *option* (3.a) for asymmetric
bidirectional LSP establishment. 

> 
> Adrian 
> 
> 
> 
>