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Re: ATMF UNI or ITU Q.2931?

  • From: Ephraim Gadsby <a@b.c>
  • Date: Tue, 19 Jun 2001 23:26:58 GMT
  • Organization: - minimal
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On Mon, 18 Jun 2001 12:20:32 -0700, "WJ" <wjsu@hotmail.com> wrote:

>Sorry if this is a FAQ.
>
>Could someone briefly tell the difference of purpose between ATM Forum's UNI
>spec and ITU's Q.2931?
>To provide signaling, which spec shall one follow?
>



The ATMF provides the de facto standard.

The split came about as a culture clash between telecomms (ITU) and
datacomms (ATMF) - look at the difference between an ITU document and
an RFC to see the difference in way the two industries work.  

The ITU developed Q2931 (which is only one of several document that
specify the ITU version) from narrowband ISDN (and other) signalling
documents. The ATMF simplified it and added a few features that
computer industry  needed. 

In the end ATM sold mostly into computer networks rather than PSTN, so
the ATMF won out. However the most recent version, UNI 4.0,  is
specified in terms of how it differs from the ITU version - so you
need to have both sets of documents. Actually I find Q2931 much
clearer than the ATMF documents.  

The real problem though is that there are three versions of the ATMF
UNI in use - 3.0, 3.1 and 4.0,  with 3.0 having an incompatible
version of SSCOP. 

The two side of the link negotiate what they will use via ILMI.