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Cell Relay Retreat>MPLS-OPS Archive>month:2001-Jun> msg00377



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RE: ATM Label stack processing

  • From: Javier Antich <javier.antich@telindus.es>
  • Date: Thu, 28 Jun 2001 13:09:14 +0200
  • Resent-Date: Thu, 28 Jun 2001 08:21:01 -0400
  • To: John Black <john_black66@hotmail.com>, mpls-ops@mplsrc.com
  • X-MIME-Autoconverted: from quoted-printable to 8bit by host.secure4-hosting.net id f5SBBns07934

ATM-LSRs have routing intelligence, that it, they have IP addresses, run IGP
routing protocol (OSPF, ISIS) and run a label distribution protocol (i.e.
LDP). By means of the IGP and the Label Distributio Protocols they know
where to send each cell comming with a certain VPI/VCI pair, and swaping it
to which VPI/VCI pair. That is the only thing they do, no matter if there
are other labels inside the frame.

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Javier Antich Romaguera
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> -----Mensaje original-----
> De:	John Black [SMTP:john_black66@hotmail.com]
> Enviado el:	jueves 28 de junio de 2001 12:52
> Para:	javier.antich@telindus.es; mpls-ops@mplsrc.com
> Asunto:	RE: ATM Label stack processing
> 
> 
> 
> 
> 
> > > 1.Does it mean that every ATM switch has to reassemble AAL5 frame to 
> >read
> > > the next label from the stack?
> >	[Javier Antich]  ATM switches acting as LSRs do not need to read the
> >next label. They do only ATM switching based on the VPI/VCI values with
> are
> >the MPLS outer-most label.
> Ok
> Let see it step by step:
> 1.LER pops up label stack
> 2.First ATM switch (LSR) gets a cell on VPI/VCI A (where A is top most 
> label).
> 3. ATM LSR swaps the label A with what?
> How intermidiate atm LSRs know where to send ATM cell to if they cannot
> read 
> the stack?
> How LSP is setup?
> 
> 
> _________________________________________________________________________
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