Cell Relay Archive

[Paul Koning <pkoning@xedia.com>]

tony_ducks@my-dejanews.com wrote:
> 
> Is the VP/VC in the cell header always the same for the forward and
> backward path for a connection?  I've done some reading of ATM Forum
> and ITU specs but cannot find any specific statement that the VP/VC
> will always be the same, or that it may be different.  For UNI
> connections I cannot imagine any reason why they could possibly be
> different. 

Actually, it would be very nice if it was possible for them
to be different.  There's no technical reason why, but the
standards don't work that way.  So yes, the same VPI/VCI appears
in both directions.

> At NNI connections what would happen if the forward and
> backward paths are routed on different physical links?

They aren't.  VCs are routed as a unit, both directions on
the same route.  And here too, the same VPI/VCI are used in
both directions.  (And here especially this is a hassle that
would have been better avoided.  Oh well...)

	paul

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