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can egress know the ingress of a packet?

  • From: Eric Gray <EGray@zaffire.com>
  • Date: Tue, 30 May 2000 09:01:50 -0700
  • Cc: mpls@UU.NET

Jana,

	This is not always (or perhaps even generally)
true.

	Information about ingresses for any LSP is lost 
at each merge point in the LSP.  Given the importance
of merging for MPLS scalability, it is probably not a 
good idea to count on an ability to recover information 
about ingress LSRs from label and incoming interface.

--
Eric Gray

> -----Original Message-----
> From: Pathangi N Janardhanan [mailto:janar@netlab.hcltech.com]
> Sent: Monday, May 29, 2000 8:18 PM
> To: Tan Su Wei; mpls@UU.NET
> Subject: Re: can egress know the ingress of a packet?
> 
> 
> Hi,
> 
> >     I'd a doubt on :
> >         In a mpls network domain, for a particular ingress-egress
> pair
> > with multiple LSPs in between them, is it possible when a packet
> reach
> > the engress node, the engress node will know the following:
> >         i. ) the ingress node
> >         ii.) the lsp it travel
> >
>   Either the label on the incoming packet or the combination of label
> and interface of the
> incoming packet can be used to identify the ingress/LSP of the
> incoming packet.
> 
> Thanks
> Jana
> 
>