Marc Slemko writes...
First, I _really_ doubt the web server set the DF bit. It is almost certainly the OS, probably trying to do path MTU discovery.
If there is a smaller MTU in the middle, and someone is filtering ICMP can't fragment errors then yes, you will have trouble with PTMU discovery. The fix is to not blindly filter ICMP. Increasing the client MTU won't fix this.
Agreed that one should not blindly filter ICMP. However not all filter tests don't support discriminating individual ICMP types. Ascend is one example.
If the client lowers their MTU, there is no problem because then they advertise an appropriate MSS and no stack should try sending packets that it knows will need to be fragmented given the client MSS.
That's one reason I went with lower MTU until I could replace SLIP with PPP. But then I discovered other things work better, such as interactive telnet during multiple concurrent downloads. So I leave MTU low until I get that OC-12 into my apartment. -- Phil Howard | blow1me4@spammer0.net no75ads9@no3where.org ads9suck@dumb0ads.com phil | stop9397@noplace2.org ads0suck@lame9ads.net no27ads2@nowhere0.org at | ads4suck@nowhere5.net eat0this@noplace5.com die2spam@nowhere4.net milepost | eat8this@spammer3.net suck1it7@anyplace.com end8ads9@lame8ads.org dot | crash834@anyplace.edu suck5it5@spammer6.edu suck7it3@dumbads1.net com | die5spam@anyplace.edu no16ads5@no61ads7.org no47ads4@anyplace.com