The problem with MTU <1500

[Michael Sierchio]

2012/3/26 Владислав Продан <universite at ukr.net>

>
> Dear all!
> I have two different values of uplink MTU - 1440 and 1492.
> And in a local network - 1500.
> In Cisco routers can be set 'set ip df 0', but I have no such router :(
> What options are there for FreeBSD?
>

 man ifconfig - not the 'mtu' option.  You should set the MTU size on the
interface to match the uplink MTU.  And you should make sure you handle
ICMP need-frag error messages, otherwise Path MTU discovery will be broken.

Only use the net/tcpmssd?


That's a workaround for not properly handling ICMP error messages, and just
for TCP ;-)


> Will it be possible to process both two channels of 1Gb?
>
> Never. ;-)  Not in practice.  What is the bandwidth - delay product?
That's a fraction of the 1Gbps you'll never get.

- M