Cell Relay Archive

[Kathleen Kuypers <kkuypers@dma.be>]

Hi to you all,

I've got 2 rather basic questions about (the interpretation) of
standards, and I would be really glad if someone could help me out..

1. About the VPI and VCI field in the ATM cell header
-----------------------------------------------------
According to what I've read:
at UNI   VPI:8,  VCI:16 bits
at NNI   VPI:12, VCI:16 bits
Someone told me that it was perfectly according the ATM standards when
an ATM-switch uses only let's say 4 bits for the VPI and 8 bits for the
VCI. He says that to be compliant with the standard it is only needed
that the switch supports a continuous VP-VC address range up to its
maximum. So address space at UNI 0-(2^4-1) for the VP and 0-(2^8-1)
would be sufficient.

2. consequences of reduced VPI/VCI range
----------------------------------------
If we have a reduced rangen for our VPI and VCI, let's assume again 4
bits for the VPI and 8 bits for the VCI, do we get in trouble when we
use UNI 3.0/3.1, and later on UNI 4.0 and PNNI signalling with an
ATM-switch which supports the complete range? Is there always a VPI/VCI
negotiation-phase?

Thanks, Kathleen.
Is there a VPI/VCI