gentoo@xxxxxxxxxxxx wrote:
On netBSD setting the MTU also seems to set the MRU, is this the case
here to? should people have thier DSLAMs configured for the same MTU?
It doesn't set MRU - you can still receive a larger than MTU packet.
I guess what you mean is MSS, if so yes Linux and Windows TCP also
choose what tcp MSS to advertise by looking at the MTU on the interface.
This means you get the tweak both ways. If you can't change each LAN PC
then you can do it with Linux iptables set mss, you can make it
aysymmetric and have min limits this way aswell.
The DSLAM is at the exchange. Doing it on the router by setting MTUs can
cause problems and isn't as good as doing each client/clamping. If you
set the LAN facing interface of the router to less than the clients all
the websites/networks that set DF and don't respond to ICMP frag needed
will expose their brokenness.
FWIW the only time I see MRU is when I log on (pppoa) to my dsl
connection. The other end asks for 32725 so the MTU on my ppp0 gets set
to 32725 - it's lucky I can't really use it and tc doesn't pick up on
it, though the mtu bit of the atm/dsl hack I use hardcodes it.
Andy.
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