The MPLS WG Archive

["Yongjun Im" <yongjuni@erlangtech.com>]

----- Original Message ----- 
From: "Vishal M" <vishal_study@yahoo.com>
To: <mpls@UU.NET>
Sent: Thursday, November 01, 2001 2:59 PM
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. 

What is 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 ?

Since ATM-LSR has only cell switching capability, it is not able to
look into EXP field in the shim header. Howerver, Edge ATM-LSR can look into 
EXP field.

> 
> 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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