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Cell Relay Retreat>MPLS WG Archive>month:2002-Jul> msg00036



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AW: your mail

  • From: Hummel Heinrich <Heinrich.Hummel@icn.siemens.de>
  • Date: Tue, 2 Jul 2002 16:25:37 +0200
  • Cc: "'Eric Osborne'" <eosborne@cisco.com>, George Sheng <george_s97@hotmail.com>, scullptor@yahoo.com, mpls@UU.NET
  • X-MIME-Autoconverted: from quoted-printable to 8bit by cell.onecall.net id g62EOa321867

It  gets weirder  and weirder: The MPLS WG invents a label stack, but does not care at all that any of the
deeper nested labels may ever be signalled/carried by means of a Label-TLV/object (no public comments to my
Hierarchical LSPs, draft-hummel-mpls-hierarchical-lsp-01.txt).

However it is ok, to "steal" the deepest nested label and call it "VC-label" for indexing
some VRF at some remote PE. Furthermore it is ok, to "steal" the very same label for hashing.

Independent from what is clean and what is quick&dirty, I cannot detect any sense in giving a hash-meaning to the bottom label at all.



Heinrich Hummel
Siemens

-----Ursprüngliche Nachricht-----
Von: Eric Rosen [mailto:erosen@cisco.com]
Gesendet: Dienstag, 2. Juli 2002 16:06
An: Shahram Davari
Cc: 'Eric Osborne'; George Sheng; scullptor@yahoo.com; mpls@UU.NET
Betreff: Re: your mail 


Shahram> To do ECMP, you need to  assign hashed values to egress ports. This
Shahram> assignment is the hash state that I said you need.  

A hash is  a function that maps  some sequence of octets into  a sequence of
integers.  If you want to split  traffic over six paths, while ensuring that
all packets  with the  same bottom label  travel the  same path, you  need a
function that maps  a 20 bit quantity  into a number from 1-6.   There is no
need to maintain state of any kind.


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