Subject: RE: draft-raggarwa-rsvpte-pw-01.txt

From: [email-masked]
Date: Tue, 29 Mar 2005 12:49:57 +0100

>  
> > NH=> OK, let me have a go.  In a client/server relationship how many

> > server layer trails are needed to carry the client?
> > Answer is 1.  So why don't we carry the client directly over 
> > a single MPLS LSP then?  The answer is simple....if the 
> > server is LDP with merging we can't resolve the client directly.  
> 
> I think the real reason is simply not to burden the service
> provider with handling an immense number of connections that 
> all originate and terminate at the same point, and thus are 
> all routed identically in the core.
> 
> ... and that's also why PWs are a new layer network,
> just as the VC layer was for ATM.
> 
Thanks Yaakov....you correctly describe a key reason for hierarchy (BTW
the VP and VC layers in ATM are actually not clearly distinguished in
practice, ie occur in the same traffic unit).  But that was not what I
was describing (which is a forced consequence of merging, irrespective
of any other requirement for hieerachy, *if* the client is not cl-ps, ie
has SA/DA pair).  And there is a major difference between how a digital
wrapper hierarchy behaves (which is what MPLS is) and how true
client/server hierarchy behaves.....the latter has functionally
decoupled layer networks, the former does not (in fact all the nested
LSPs belong to the same layer network and this has some interesting
consequences).  IPinIP is true client/server relationship BTW.

regards, Neil