[Asterisk-Users] SIP on TCP

[Jamie Carl]

On Wed, 3 Sep 2003 15:47:35 -0600
  Timothy Soos <XQL at americanisp.net> wrote:
>*This message was transferred with a trial version of 
>CommuniGate(tm) Pro*
>On Wednesday 03 September 2003 09:32 am, Master Abi 
>wrote:
>> Hi
>>
>> I read through the archives but could not find much 
>>reference to * using
>> SIP on TCP instead of UDP for signalling. Can * be 
>>configured and if so
>> how. My service provider will only accept SIP signalling 
>>on TCP.
>>
>> Thanks
>>
>> Master
>
>This suggestion is not exactly elegant, yet it may be of 
>help:
>
>"The UDP over TCP tunnel is a simple UDP-over-TCP 
>application written in Java, 
>and is designed so that people behind a firewall can 
>connect through a TCP 
>connection to play Quake and other UDP-based games."
>
>It is available at:
>http://freshmeat.net/projects/udptunnel/?topic_id=907%2C150%2C151
>-- 

This wouldn't exactly help his situation.  Would this 
tunnel require this software running at both ends?  What 
he's talking about is SIP on TCP. Not SIP on UDP on TCP. 

SIP, by design, is supposed to be used with UDP as it has 
a lot of it's own transport control mechanisms, ie, 
retries, acks, etc, which allow for UDPs lack of 
reliability.

However, SIP can run on TCP with no major changes apart 
from altering the stack to establishing a TCP connection 
before signalling.

 From section 18 in RFC3261:

------------
All SIP elements MUST implement UDP and TCP.  SIP elements 
MAY implement other protocols.

Making TCP mandatory for the UA is a substantial change 
from RFC 2543.  It has arisen out of the need to handle 
larger messages, which MUST use TCP, as discussed below. 
 Thus, even if an element never sends large messages, it 
may receive one and needs to be able to handle them.
------------

So if * wants to be RFC 3261 complient (which to get in 
anywhere commercial, it'll need to be) TCP MUST be 
implemented.

Regards,

Jamie Carl
Jazz Inc.
Email:  me at jazz-inc.net
Web:    www.jazz-inc.net
Phone:  +61-414-365-466
Jabber: jazz at netmindz.net