Messages in this thread | | | From | kuznet@ms2 ... | Subject | Re: Path MTU discovery, UDP and Linux | Date | Fri, 29 Oct 1999 18:05:32 +0400 (MSK DST) |
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Hello!
> Does linux 's kernel implement Path MTU discovery in UDP packets (IPv4)? I
Yes.
> runned tcpdump and i saw that TCP packets usind Don't Fragment bit while > UDP packets don't use. Why?
PMTU discovery is useless for UDP at the moment, so that it is turned off by default.
> I saw that Solaris use Path MTU in UDP packets too.
The problem is that UDP does not retransmit. If pmtu discovery on UDP solved some (even minor) problem, we would enable it. It does not as of 2.2 and 2.3, so that it is not worth to loose packets without any clear purpose. I have no idea why sun folks did it.
BTW one application for pmtu discovery for udp is found and it is enabled by default in patch ftp://ftp.inr.ac.ru/ip-routing/softnet-*.dif.gz
Alexey
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