ppp fix

[Paul Borman prb@bsdi.com]

> From: Russ Cox <rsc@research.att.com>

> the standard ppp default is for 1500 mtu
> nuless specified by either side, and we're
> not specifying it.  i suppose the client ppp
> software could request a lower mtu, but i
> bet it rarely happens.  i'm not sure i see a
> good way to handle mtu in the server on a
> per-client basis.

Each side may request the other side to set its
MTU to some higher or lower value.  Slower lines
may wish a lower MTU so that interactive response
is better.  We have also had experience with some
popular windows based PPP programs which seem to
work better with a lower MTU (working better
means they do not hang :-)  Note that in all of
these cases, it is the client which initiates the
request, not the server.  There is no way to get
the other side to request that you change your
MTU, however, you can always just send smaller
packets even if the other side did not negotiate
them.  As long as a server honors a clients
request for a smaller MTU every thing should work
just fine.

			-Paul Borman
			 prb@bsdi.com