PPPD Issues pinging server with packets greater than 484 bytes length

[Andrew Sinclair]

Has anyone encountered problems pinging the rtems PPPD server with packets greater than 484 bytes length?

I have established a connection with a Win XP box, and I am using MS-DOS to ping. The following works fine:
ping -l 484 192.168.124.5 
However the following fails:
ping -l 485 192.168.124.5 

I have tried making my termios serial buffers very large, and setting "mru" and "mtu" to 1500 to no avail.

Any ideas?