[c-nsp] transport path-mtu-discovery - ME3600....too unpredictable to use?

[CiscoNSP List]

Thanks for all the replies - Given our circumstances, I think the "safest/sanest" approach would be to disable PMTUD, and enable "ip tcp mss xxx" (Maybe 1300 or 1400).

Cheers

________________________________________
From: Nick Hilliard <nick at foobar.org>
Sent: Thursday, 25 February 2016 6:35 AM
To: CiscoNSP List
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] transport path-mtu-discovery - ME3600....too unpredictable to use?

CiscoNSP List wrote:
> Quick synopsis of our network, multiple pops, all connected via
> various 3rd party carriers, who all use differing MTUs, that can also
> "change" unexpectedly(Unavoidable unfortunately!)

MTU means _maximum_ transport unit, so if your underlying transport
network unexpectedly changes this so that the max transport packet size
decreases below the configured MTU on the layer 3 side, then you are
going to drop packets, end of story.

Your transport providers need to guarantee you a specific MTU and you
need to configure your router L3 interfaces with that number.

Nick