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RE: Info On DLCI/VPI VCI as the Label

  • From: "Gibbs, Mike" <mgibbs@aleron.com>
  • Date: Fri, 7 Dec 2001 07:43:55 -0500
  • Resent-Date: Fri, 7 Dec 2001 09:53:46 -0500
  • To: "'J.C.Ramesh Babu'" <rameshbabu_j@inf.com>, mpls-ops@mplsrc.com

This is assuming your message meant ATM Labels in a cell, and not MPLS
Labels.  It is split up into VPI/VCI, in this manner, for a UNI ATM Cell
Header:

 VPI (Virtual Path Identifier)  Second four bits of Byte 1 and the first
four bits of Byte 2
 VCI (Virtual Channel Identifier)  Second four bits of Byte 2, Byte 3, and
the first four bits of Byte 4

If you want the cells full header:

 GFC (Generic Flow Control)1  First four bits of Byte 1
 VPI (Virtual Path Identifier)  Second four bits of Byte 1 and the first
four bits of Byte 2
 VCI (Virtual Channel Identifier)  Second four bits of Byte 2, Byte 3, and
the first four bits of Byte 4
 PT (Payload Type)  The fifth, sixth, and seventh bits of Byte 4
 CLP (Cell Loss Priority)  Eighth bit of Byte 4
 HEC (Header Error Control)  Byte 5


Mike Gibbs

> -----Original Message-----
> From: J.C.Ramesh Babu [mailto:rameshbabu_j@inf.com]
> Sent: Friday, December 07, 2001 12:41 AM
> To: mpls-ops@mplsrc.com
> Subject: Info On DLCI/VPI VCI as the Label
> 
> 
> Hi All,
> 
> When we think of ATM as the Layer 2 technology, we know that 
> VPI/VCI is
> considered as the Label (identifier). But I'm eager to know 
> how a label (the
> exact format in terms of bits and bytes) looks like.
>  Can someone kindly educate me on this?
> 
> Thanks in advance
> 
> J.C.Ramesh Babu
> 
> E-mail : rameshbabu_j@infy.com
>        : rj52@casc.com
> Ph :91-80-852 0261 Ext:1933 (O)
>    :91-80-6097077 (R)
> 
> 
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