On Mon, 27 May 2002 01:23:24 +0900
itojun@iijlab.net wrote:

> 	it seems that there's no notification from icmp layer to tcp layer,
> 	when smaller-MTU route goes away.  am I correct?  how should we fix
> 	it? (is it sufficient if we just call registered callback routine?)

Last time I looked, TCP just picked up the new size by looking
at the route MTU as it went through tcp_output.  This is inefficient,
as it would be better to just get a notification each time the MTU
changed, so that we could always know what the appropriate size was.

> 	openbsd uses PRC_MTUINC as notification from icmp layer to tcp layer.

That sounds like a win, if you are sure you've caught all possible
changes of the route MTU.

Kevin
kml@selresearch.net