[Freeswitch-users] Codec list truncation?

[Lawrence Conroy]

Hi Ken, folks,
 Um ... strictly true but **VERY** misleading.
UDP doesn't handle fragmentation only because it's done at the IP layer -- see the inside front cover of Stevens' TCP/IP Illustrated Volume 1.
You can send a UDP packet out of up to 64 KBytes. If you do, it'll be fragmented by the IP layer into a set of fragments, each datagram being less than the MTU, with the fragment offset in all but the first datagram being non-zero.

I send and receive DNS packets of up to 3-4 KBytes [with the EDNS0 bufsize option set :] -- problems only occur with brain-damaged DNS servers (Microsoft) and intrusively dumb home router/NATs.

----

TCP was originally added as an option for SIP leading up to RFC2543 because some people didn't like the message retransmission timers -- back then, the idea was that if one had a TCP stream set up, one didn't need to do the retransmit logic in SIP. I agree that it was also added as an option because some ancient host network stacks were broken (and didn't handle fragmentation and reassembly). N[and some early SIP implementations had hard limits in their application buffers -- no one would ever need more than a kilobyte for a SIP message, would they?]. Now the network stacks do support F&R, and I sincerely hope no-one's still trying to use that early C*s*o SIP code.

all the best,
  Lawrence


On 21 Mar 2014, at 16:33, Ken Rice <krice at freeswitch.org> wrote:
> UDP doesn't handle fragmentation... This is why sip is required to use both
> UDP and TCP (if you exceed MTU you Must use TCP per the RFC)
> 
> There are things like compressed headers to help with this but that only
> goes so far when you have 1500+ bytes in the SDP alone...
> 
> 
> On 3/21/14 8:41 AM, "Pete Ashdown" <pashdown at xmission.com> wrote:
> 
>> On 03/21/2014 03:32 AM, Keith Laaks wrote:
>>> Hi,
>>> 
>>> Are you perhaps hitting the MTU limit?
>>> 
>> 
>> Are SIP transmissions limited to a single packet confined by MTU?  Why
>> not just continue the list in the next packet?
>> 
>> 
>> _________________________________________________________________________
>> Professional FreeSWITCH Consulting Services:
>> consulting at freeswitch.org
>> http://www.freeswitchsolutions.com
>> 
>> 
>> 
>> 
>> Official FreeSWITCH Sites
>> http://www.freeswitch.org
>> http://wiki.freeswitch.org
>> http://www.cluecon.com
>> 
>> FreeSWITCH-users mailing list
>> FreeSWITCH-users at lists.freeswitch.org
>> http://lists.freeswitch.org/mailman/listinfo/freeswitch-users
>> UNSUBSCRIBE:http://lists.freeswitch.org/mailman/options/freeswitch-users
>> http://www.freeswitch.org
> 
> -- 
> Ken
> http://www.FreeSWITCH.org
> http://www.ClueCon.com
> http://www.OSTAG.org
> irc.freenode.net #freeswitch
> Twitter: @FreeSWITCH
> 
> 
> 
> 
> _________________________________________________________________________
> Professional FreeSWITCH Consulting Services:
> consulting at freeswitch.org
> http://www.freeswitchsolutions.com
> 
> 
> 
> 
> Official FreeSWITCH Sites
> http://www.freeswitch.org
> http://wiki.freeswitch.org
> http://www.cluecon.com
> 
> FreeSWITCH-users mailing list
> FreeSWITCH-users at lists.freeswitch.org
> http://lists.freeswitch.org/mailman/listinfo/freeswitch-users
> UNSUBSCRIBE:http://lists.freeswitch.org/mailman/options/freeswitch-users
> http://www.freeswitch.org