VLC and VBrick

[Talbert, Scott]

> -----Original Message-----
> From: Talbert, Scott 
> Sent: Thursday, July 11, 2002 10:58 AM
> To: 'vlc at videolan.org'
> Subject: RE: VLC and VBrick
> 
> > >- The size of the UDP packets sent varies.  Most packets are 4136
> > >bytes.
> > 
> > 4136 ??? What sort of network are you working on ? VLC expects a MTU
> > of 1500 bytes (such as Ethernet), and that is the problem.
> > 
> > A temporary workaround would be to change in plugins/network/ipv4.c
> > DEFAULT_MTU to 4136. However, if you find a clean way to 
> retrieve the 
> > MTU of the interface, I'm interested.
> 
> We actually _are_ working on an Ethernet right now.  The 
> VBrick is sending out 4136 byte datagrams, which are getting 
> fragmented into Ethernet frames and reassembled into 4136 
> byte datagrams on the client and passed to VLC.
> 
> Why not set DEFAULT_MTU to 64K, which is the maximum size for 
> UDP datagrams.  Then, VLC would work in all cases.  Would 
> this cause too much of a performance hit?
> 
> Alternatively, I wrote a function which will determine the 
> maximum size of UDP datagrams on a given machine.  It's not 
> exactly pretty, but it should be portable.  
> http://www.techie.net/> ~talbert/max_udp_datagram_size.c

I did some more research and testing on this (with Linux, Solaris, and AIX)
and it seems these platforms don't do much of anything consistently.  :)  So
the best bet would probably be just to set the DEFAULT_MTU to 64K and play
it safe.

Scott

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