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

[Marshall Eubanks <tme () multicasttech com>]

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


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> > Marshall
> >
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