Cell Relay Archive

[riwells@hotmail.com]

Here's my take on this extremely interesting posting (by Jeff Wilson)
and
the subsequent response (by Baris Aksoy).  KINDLY FEEL FREE TO CORRECT
ME,
SHOULD ANY OF MY OBSERVATIONS BE WRONG.  To keep this posting short and
readable, I am splitting it into multiple postings.  Here's part I:


Point 1
=======
The Signature Edition of "ATM Theory and Applications" by McDysan and
Spohn (arguably the "best" ATM book out there) states very clearly on
Pg 359 that "AAL2 has no Segmentation and Reassembly Sublayer".  Anyone
who takes this book as gospel is bound to be misled by such a conclusive
statement made in the book at a time when the AAL2 standardization had
not even completed.

P.S. My personal opinion is that McDysan's book is a useful reference
book, but it is poorly written and its layout leaves much to be desired,
and of course, every now and then it is misleading. Unfortunately, this
book is as good as any on the market.


Point 2
=======
The main ITU Specification on AAL2, I.363.2, makes only one reference
to SAR, and that too in the Abbreviations section!  Mind you, this
standard is not that old.  It was released in September 1997.

Point 3
=======
Has the ITU-T I.362.2 specification, that Baris is talking about, been
publicly released?  I tried looking up the ITU website
(http://www.itu.int/itudoc/itu-t/rec/i/index.html)
without much success.

----Richard


Based on Point 1 and Point 2, I can see why Jeff concluded that AAL2
does
not have the SAR sub-layer.









In article <388031CB.2693ED6D@gte.net>,
  baris.aksoy@gte.net wrote:
>
> --------------BAAADC14172621049E638683
> Content-Type: text/plain; charset=us-ascii
> Content-Transfer-Encoding: 7bit
>
> Hello,
>
> Either I'm missing something here or, you miss that AAL2 layer also
has
> SAR layer. AAL2 consists of a Common Part Sublayer (CPS) and a Service
> Specific Convergence Sublayer (SSCS):
>
>       -The AAL2 CPS specification, ITU-T I.362.2 - 09.97
>
>      - The AAL2 SSCS consists of two elements:
>           Segmentation and Reassembly (I.366.1) - 06.98
>           I.Trunk (I.366.2) - 02.99
>
> The SAR-SSCS sublayer for the AAL2 supports a bandwidth-efficient
> transmission of low-rate, short, and variable length packets in delay
> sensitive applications, such as voice.In this way, it's different form
> AAL5- SAR function, which targets transmission of bulk of variable
length
> non-real time packets.
>
> Baris
>


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