Caching learned MSS/MTU values

[Ignatios Souvatzis]

On Thu, Oct 17, 2013 at 09:05:24AM -0700, Jason Fesler wrote:

> I know that the various operating systems tend to cache any PMTUD issues
> that they can detect; future connections to that destination will use
> smaller packets accordingly. What I can not see to find is an adequate
> description of what granularity this gets cached with. /128? /64?

NetBSD does it on a per-address base - that is, I think, per /128. It's 
an additional entry in the routing table, like this:

2a01:170:1012:77::25               fe80::20d:61ff:fe46:50ad%xennet0 UGHD        2       27   1280  xennet0

	-is