Caching learned MSS/MTU values

[Jason Fesler]

I'm once again considering trying to improve on the test-ipv6.com PMTUD
failure detection. Due to limitations on the client side I can't use raw
sockets to generate test packets. The client is JavaScript and runs in a
browser; all I can do is try fetching urls from multiple locations, each
with a different MTU.

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?   Also, I
the absence of Packet Too Big messages, what does each OS do?

If anyone has pointers, please share. It will affect what and how I can
improve the site, given the restrictions I have with the client side.




-- 
 Jason Fesler, email/jabber <jfesler at gigo.com> resume: http://jfesler.com
 "Give a man fire, and he'll be warm for a day;
 set a man on fire, and he'll be warm for the rest of his life."
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