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Re: 1500 does not work: Thoughts on increasing MTUs on the internet

  • From: Marshall Eubanks
  • Date: Sun Apr 15 09:03:23 2007


On Apr 15, 2007, at 1:49 AM, Petri Helenius wrote:


Marshall Eubanks wrote:

I advise people doing streaming to not use MTU's larger than ~1450 for these sorts of reasons.
The unfortunate side-effect of that is that most prominent streaming apps (don't know about Youtube though) then send fragmented UDP packets which leads to reassembly overhead and in case of lost packets, a significantly larger lost data than neccessary.

Pete

Dear Pete;

The streaming servers that I have dealt with (such as Darwin Streaming Server) do the fragmentation at the application layer. They thus send out lots of packets at or near (in this case) 1450 bytes, but they are not UDP fragments.
That's the whole point - many networks will not deliver fragments at all, much less the increased risk of loss when they do. (I use Cox Cable at home, and this network apparently does not forward fragments and also has an apparent MTU of 1480 bytes.)

Just looked at a YouTube dump, btw, and almost all of the packets are 1448 bytes.

Regards
Marshall





Kind regards
Peter and Karin Dambier


Regards
Marshall

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