The MPLS WG Archive

["Proch, Daniel" <Daniel.Proch@marconi.com>]

Vishal,

Somewhere I read that E-LSP shouldn't be used for
ATM-LSR. Could someone please explain why ?

MPLS over ATM (cell) interfaces uses the existing ATM cell structure and
what were the contents of the VPI field or the combined VPI/VCI fields to
infer a label.  There are no EXP bits in the header and therefore only
L-LSPs can be supported on LC-ATM interfaces.  

dan

-----Original Message-----
From: Vishal M [mailto:vishal_study@yahoo.com]
Sent: Thursday, November 01, 2001 3:59 PM
To: mpls@UU.NET
Subject: Re: question on e-lsp and l-lsp



Hi,

I have some followup questions on L-LSP and E-LSPs:

1. Can we map multiple CTs onto a single L-LSP ? The
draft seem to suggest that creation of a separate LSP
can be done for every CT. 

Is creation of separate L-LSP mandatory for every CT
or  is it left to the implementation?

2. Somewhere I read that E-LSP shouldn't be used for
ATM-LSR. Could someone please explain why ?

Thanks for your time,
Vishal.

"Fan, Zhong" wrote:
> 
> Can anybody shed some light on the differences
between e-lsp and
> l-lsp please? I'm reading
draft-ietf-mpls-diff-ext-09.txt at the
> moment. Although the draft gives denifition of these
two kinds of
> LSPs, I am still confused. Is this all about the
mapping of diffserv
> classes to MPLS FEC or EXP?

The draft explains the differences.

In superbrief summary;

- An L-LSP has one QoS for all packets.  It is
determined at LSP
  setup.  This is similar to setting up an LSP without
any DiffServ
  extensions, except that the objects used in the
signaling are
  different.

- An E-LSP has up to 8 QoS levels for the single LSP. 
The EXP bits
  determine the appropriate QoS on a per-packet basis.
 The QoS that
  is assigned to each EXP value is signaled at LSP
setup (or is a
  configured default if the values are not signaled.)

-- David


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