Subject: RE: [Fwd: use ideas from, but not true aal]

From: [email-masked]
Date: Tue, 16 Apr 2002 09:44:35 -0700

I like your overall concept.  Keeping the structures (i.e. not extracting 
CAS) makes sense, because judging from your response, it certainly appears 
to be the most hands-off approach, which I like.  But on top of this, my 
additional belief is that:

* there is really no need to break up packets into 48-byte units, with 
intrapayload encapsulatory information contained therein;
* there is really no need for INTRApacket sequencing.  There is a need for 
INTERpacket sequencing, but we already have defined this in the PW header;
* there is never a need for more than one structure pointer per packet. 
Using the AAL1 encapsulation, this could occur unnecessarily.

Is encapsulatory a word?  I don't know.  :-)

So I don't see how AAL1 is such an efficient approach to our specific 
problem.  I'm sure it's an efficient answer to the problem in an ATM 
setting, where the 3 asterisked elements above don't apply.  But here, if 
you just take the one part of AAL1 that matters in our generic PSN setting 
-- the structure pointer -- and stick it into the packet header (granted, 
this means it will be a few extra bits than it is currently), then this 
seems to be MORE efficient, not less.  If the parity protection is 
important to you, we can keep that feature as well.  The payload, in this 
scenario, becomes completely natural....none of these unnecessary 48-byte 
partitions or useless fields.

In a previous posting, you said, "Just tell me where the structure 
starts!!! That's all that is needed!!!"  Are you prepared to take that 
back?  Because I'm giving you exactly what you asked for and no more.  ;-)

It seems like we all agree that in unstructured and N*DS0 modes, 
everything is great.  So the only issue is N*DS0 + CAS.  We also agree in 
principle, at least, that the payload should be as simple as possible, 
while still providing robustness.  It appears that extracting bits is less 
simple than transmitting them --- as long as you "just tell me where the 
structure starts."  So isn't it a good compromise to simply transmit the 
bits, including CAS, then stick a structure pointer in the header (plus 
parity if you want)?  This seems like the outline for a solution we're 
looking for.

It's not clear to me why either side would be particularly unhappy with 
this outline. 

-Craig