[Asterisk-Users] UDP Fragmentation Problem

[Rich Adamson]

<snip>
> >>>>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.
> > 
> 
> Here it is ;-)

Okay, looked at the pcap and see the fragmentation, but that does not
indicate your asterisk IP stack is not handling it properly. Might compare
a 'sip debug' with those packets to see if data is reassembled.

Since both pieces of the original fragmented packet did in fact arrive at
your destination, the only issue left is whether your IP stack reassembled
them properly. I'd suspect another problem is lurking unrelated to
fragmentation.

Rich