Subject: RE: e-lsp & l - lsp

From: "Kota, Ravikumar" <[email-masked]>
Date: Wed, 22 Aug 2001 18:02:27 -0400

Hi srinivas ,
These are two techiniques to implement packet treatment in  MPLS cloud ,
with diffserv inferred information.
The diffserv information from the packet can be encapsulated into label/exp
field of  "MPLS labelled packet "(this will be happened between
diffservcloud and mpls cloud ),
so that we will be making sure that diffserv information will be used in
MPLS cloud to treat the packets according to that information.
Cisco is implementing this concept with the name : MPLS  DIFFSERV AWARE TE
 e-lsp intended for carrying single OA for single LSP.
l-lsp is intended for carrying multiple OA s for LSP.

 OA  :      Ordered Aggregate. The set of Behavior Aggregates which
               share an ordering constraint.

Any comments are welcome.

Reference draft : draft-ietf-mpls-diff-ext-09.txt  

Regards
Ravikumar Kota
978  263 0094 (extn  8157 )(work)   
978 869 3314(cell)

-----Original Message-----
From: Srinivas T M [mailto:[email-masked]]
Sent: Wednesday, August 22, 2001 5:46 PM
To: [email-masked]
Subject: e-lsp & l - lsp

Hi,
    Can anybody explain what is e-lsp ,l-lsp and
difference between them.

Thanks,
Srini

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---

From: "Mark Seery" <[email-masked]>
Date: Wed, 22 Aug 2001 15:32:37 -0700

>>  e-lsp intended for carrying single OA for single LSP. l-lsp is intended
for carrying multiple OA s for LSP.

I believe it is the other way.

From the below mentioned draft:

"1.2 EXP-Inferred-PSC LSPs (E-LSP)

   A single LSP can be used to support one or more OAs. Such LSPs can
   support up to eight BAs of a given FEC, regardless of how many OAs
   these BAs span. With such LSPs, the EXP field of the MPLS Shim
   Header is used by the LSR to determine the PHB to be applied to the
   packet. This includes both the PSC and the drop preference......."

"1.3 Label-Only-Inferred-PSC LSPs (L-LSP)

   A separate LSP can be established for a single <FEC, OA> pair.
   With such LSPs, the PSC is explicitly signaled at label
   establishment time so that, after label establishment, the LSR can
   infer exclusively from the label value the PSC to be applied to a
   labeled packet. When the Shim Header is used, the Drop Precedence to
   be applied by the LSR to the labeled packet, is conveyed inside the
   labeled packet MPLS Shim Header using the EXP field. When the Shim
   Header is not used (e.g. MPLS Over ATM), the Drop Precedence to be
   applied by the LSR to the labeled packet is conveyed inside the link
   layer header encapsulation using link layer specific drop precedence
   fields (e.g. ATM CLP)....."

Additional comments:

A number of existing layer 2 technologies (e.g. ATM) can only support L-LSP
because of their inability to carry the equivalent of a full EXP field (drop
precedence can be indicated).

Some people have argued that in the context of diffserv/traffic engineering
support only L-LSPs would be used - I leave this argument as an exercise for
the reader.

E-LSPs represent an approach most similar to diffserv TOS treatment.

-mark

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of Kota,
Ravikumar
Sent: Wednesday, August 22, 2001 3:02 PM
To: 'Srinivas T M'; [email-masked]
Subject: RE: e-lsp & l - lsp

Hi srinivas ,

Regards
Ravikumar Kota

-----Original Message-----
From: Srinivas T M [mailto:[email-masked]]
Sent: Wednesday, August 22, 2001 5:46 PM
To: [email-masked]
Subject: e-lsp & l - lsp

Hi,

Thanks,
Srini