Subject: Re: fragmentation by NetBSD routers vs. reassembly on other systems....
To: None <tech-net@NetBSD.ORG>
From: Greg A. Woods <firstname.lastname@example.org>
Date: 09/02/2000 13:25:34
[ On Saturday, September 2, 2000 at 16:42:11 (+0200), Sean Doran wrote: ]
> Subject: Re: fragmentation by NetBSD routers vs. reassembly on other systems....
> It changes the largest segment size that you admit to being able
> to receive, whenever a TCP connection is started.
Yes, exactly! That's the right way to say it concisely!
> It has nothing to do with what segment size you will send; that
> is limited by what mssdflt is set to on the other system.
and of course by the MTU of your local interface (max(mssdflt, if_mtu)).
This is all without Path-MTU-discovery in operation too, of course, as
well as mss_ifmtu=0 on newer systems too.
The only thing weird about what I've seen with NetBSD is that changing
mssdflt definitely affected packet size on the fly..... From the code
this appears to happen as a result of something to do with congestion
window monitoring, and may in fact be a bug (the code was probably
written before tcp_mssdflt became a run-time tunable parameter!).
Greg A. Woods
+1 416 218-0098 VE3TCP <email@example.com> <robohack!woods>
Planix, Inc. <firstname.lastname@example.org>; Secrets of the Weird <email@example.com>