The IP over ATM Mailing List Archive by date

[bryang@eng.adaptec.com (Bryan Gleeson)]

>
>
>You could even put the "echo ID" into the AAL5 CPCS-SDU
>in some of those unused bits near the end and you wouldn't
>even have to change your hardware. 
>
>There you have it: AAL5-1/2 :-)
>

Being pedantic, I guess you mean the AAL5 CPCS-PDU. The
CPCS-SDU contains the Interface Data (ID) and CPCS
User-to-User Indication. The CPCS-PDU contains the
ID and the UU, CPI, Length and CRC. The CPI is not
part of the CPCS-SDU and so an SSCS entity can't use 
those 8 bits. The UU is only 8 bits so that's not
big enough. Pity though, a 16 bit UU would probably
have been good enough.

Obviously you don't _have_ to change your
hardware here. I think such a solution could have
a little difficulty being accepted :-). A part that
could be implemented in hardware is the ECID check. 
The adapter is loaded with the ECID on VCC establishment, 
and it performs the check on PDUs that pass the 
CRC check, and chucks them away without interrupting 
the host, for example, if there is a match. Otherwise
the check is done is software, just like LANE.

Regards,
Bryan