Richard Town wrote in a message to Mike Farrill:
 RT> Link Access Procedures for Modems - we only get the cheeep end of
 RT> the market - 128 byte or 128 byte with Selective REJect on budget
 RT> modems, 244 (256 in reality?) on more expensive.  There's some with
 RT> 512 around, but not really in hobbiests' price range.
244 on the USR Couriers, ZyXEL implements a 256 LAPM packet (it may go higher 
but that's the highest I've seen reported).  The CPS difference between 244 
and 256 is pretty negligible and more than compensated for by SREJ, IMHO.
 RT> If you've got purrfect lines to your remote then MNP4's best since
 RT> on both budget and not-so-budget modems that's available with a 256
 RT> byte packet size.  It's also got less overhead than either version
 RT> of LAP-M.  But just one BLER (BLock ERror) and the whole 256 will
 RT> have to be sent again
Actually both LAPM and MNP 4 have the same 7 byte/packet overhead in standard 
implementations.  What get's resent without SREJ is all the packets in the 
pipeline.  On a Courier, that would be 15 128 byte packets or 8 244 byte 
packets using LAPM.  Using MNP 4, it would be 8 256 byte packets -- ouch!
Regards,
       David
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