On Jun 5, 2011, at 9:46 AM, Pascal Hambourg wrote:
Rick Thomas a écrit :
On Jun 3, 2011, at 10:46 AM, Jeffrey B. Green wrote:
The RFCs say that any conforming implementation MUST handle an MTU of
1280, and may not necessarily handle anything larger.
What is your point in mentionning this requirement? Do you mean that the
server should not send packets bigger than 1280 bytes if it fails to
handle properly path MTU discovery ? If so, I fully agree.
My point is that by setting your MTU to 1280, you have done *your* part. At least you can be assured that all your packets will get thru without fragmentation, even if the host at the other end -- or some intervening router -- is improperly configured.
If the host on the other end sets its MTU to something larger and an intervening router doesn't do fragmentation, they (or the admins of the router) need to fix that. An easy recommendation that you can make in this case (if the server admin on the other end is clueless but willing to help) is for them to set their MTU to 1280 as well. That will fix the problem regardless of intervening routers.
Finding a (possible series of) mis-configured intermediate router(s) and convincing the respective router-admin(s) to fix their configuration is often difficult. It's easier if you have only one person to talk to, the server admin on the other end.