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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: MTU of the Internet?
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 | [email protected] [email protected] [email protected] phil | [email protected] [email protected] [email protected] at | [email protected] [email protected] [email protected] milepost | [email protected] [email protected] [email protected] dot | [email protected] [email protected] [email protected] com | [email protected] [email protected] [email protected]
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