[Asterisk-Users] UDP Fragmentation Problem

[Rich Adamson]

> >>> I've got no success to get a friend in Bogota (Colombia) connected to my
> >>> Asterisk. He has got a ISDN Internet connection and the UDP packets will
> >>> be fragmented. It seems that the MTU of this connection is round about
> >>> 400 to 500 Bytes. Therefore most UDP-SIP packages are fragmented.
> >>> Is Asterisk not able to handle fragmented UDP packages?
> >>> Is it possible to use SIP over TCP with X-Lite?
> >>> Or has somebody another hint for me?
> >>
> >>
> >>
> >> As far as I am aware there is no such thing as a fragmented UDP 
> >> packet; each packet is sent out on its own, there is no coherency 
> >> between UDP packets like there is with TCP packets.
> >>
> >> I could be very wrong here, it's been a late night with the kids.  :-)
> >>
> > 
> > Packet fragmentation is at the IP layer, so UDP will have fragmented 
> > packets too. But... the OS should handle that and Asterisk shouldn't 
> > find out - it's a all or none policy, so it should receive the whole 
> > packet at once or nothing.
> 
> How I can setup Linux to handle UDP fragments?

Not sure why the concern with fragmentation, it should not be an issue 
with any modern linux distribution and there is nothing to setup.

The only issue that I've heard about in recent months/years relative
to fragmentation is the SonicWall firewall just can't seem to get it
right. In their case, any udp packet greater then about 1500 bytes does
not get reassembled propery, and its still an issue in the latest firmware.

If you really think you've got a fragmentation problem, I'd like to see
a packet trace (eg, ethereal) of those packets.