[CALUG] Gigabit Ethernet
linux at tempest-sw.com
Tue Oct 18 15:37:09 CDT 2005
On Tuesday 18 October 2005 07:00 am, you wrote:
> Wouldn't PMTU discovery allow the sending host to retransmit at 1500
> for anything not destined for the local LAN?
I've been doing some reading, and I think you are right. Because my
router would respond to an MTU discovery request with 1492
(because my ISP uses PPPoE), even my Jumbo-enabled adapters would then
do the right thing.
My guess is that the sites who were having problems have Jumbo-enabled
routers that are connecting to ICMP-blocking servers. Their MTU
discovery requests go unanswered, so they merrily send along Jumbo
packets, which are summarily dropped once they leave the Jumbo-safe
environs of the university or whatever. At least that's my guess why so
many people report that they need Jumbo end-to-end.
Thanks for the help.
Ray Lischner, Author of C++ in a Nutshell
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