المساعد الشخصي الرقمي

مشاهدة النسخة كاملة : What is happening with signalling standards for ATM?



A7med Baraka
04-15-2009, 08:46 PM
The Signaling Sub-Working Group (SWG) of the ATM Forum's Technical
Committee has completed its implementation agreement on signaling at the
ATM UNI (summer 1993). The protocol is based on Q93B with extensions
to support point-to-multipoint connections. Agreements on addressing specify
the use of GOSIP-style NSAPs for the (SNPA) address of an ATM end-point
at the Private UNI, and the use of either or both GOSIP-style NSAPs and/or
E.164 addresses at the Public UNI. The agreements have been documented
as part of the UNI 3.0 specification.

Additionally, the ANSI T1S1 as well as the ITU-T sudygroup XI are concerned
with ATM signalling. In the latter half of 1993 a couple of things happened:
1) The ITU finally agreed to modify its version of Q93B to more closely
to align it with that specified in the ATM Forum's UNI 3.0 specification.
The remaining variations included some typos which the ITU Study Group
found in the Forum's specification. Also, some problems were solved
differently. Aligned yes, but the changes could still cause
incompatibilities with UNI 3.0.
2) Given the above, the ATM Forum's signalling SWG decided to modify the
Forum's specification to close the remaining gap and align it with the
ITU. The end result may be declared as errata to UNI 3.0 or defined
as a UNI 3.1 specification

The biggest change is with SSCOP. UNI 3.0 references the draft ITU-T SSCOP
documents (Q.SAAL). However UNI 3.1 will reference the final ITU Q.21X0
specifications. These two secifications are *not* interoperable so there
will be no backwards compatibility between UNI 3.0 and UNI 3.1.

Beyond that folks are looking forward to a UNI 4.0 which would include
things like ABR service class among other things.

The ATM Forum also has a Private-NNI SWG. Their objective is to define an
interface between one Switching System (SS) and another, where each SS is a
group of one or more switches, such that the specification can be applied to
both the switch-to-switch case and the network-to-network cases.

Tentative schedule for the ATM Forum's work:

UNI 3.1 September 94
PNNI 1.0 March 95
B-ICI 2.0 March 95
UNI 4.0 draft June 95