[vlc-devel] [RFC] stream output MTU

[Marian Ďurkovič]

On Mon, Sep 03, 2007 at 05:59:57PM +0300, Rémi Denis-Courmont wrote:
> Having a value that is arbitrarily lowered is no better. Besides, that 
> was not even done consistently.

That was intentional and as I see you've already managed to break it...

MTU is used in 2 different contexts:

- in UDP accees to set buffer size - it must be able to accept largest
  possible UDP payload, i.e. at least 1472 bytes on ethernet

- in RTP stream output to set the payload size and avoid fragmentation

Your current value of 1400 is not apropriate for UDP access.

And by the way, it's definitely not an application-layer MTU, since
RTP header is still inside. 

If you want to have RTP payload size directly configurable, you need to
split MTU into 2 parameters: 

- MRU (for UDP access)
- RTP payload size (for stream output)

For the latter, please leave RTP header out - i.e. if someone sets RTP
payload size to 1400, the packet size should be 1440/1460 for IPv4/v6
(1400 + RTP header + UDP header + IP header).


	With kind regards,

		M.