[SIPForum-discussion] Is TCP feasible for SIP??

[M. Ranganathan]

TCP makes it more painful when Firewalls are used.  You establish an
outbound connection but the local socket is bound to some random port
on your sender side. This does not correspond to your Contact address
( for example, that may be some port like 5060, whereas the outbound
connection as bound to some random port). The Server cannot connect to
port 5060 as specified in the Contact header.

A UDP socket on the other hand, can bind to port 5060 and you can use
that same socket to send the INVITE. The server that gets the INVITE
can signal port 5060 because Firewalls and NATs are frequently
configured to be able to receive on a port they send from.

I am guessing that this is the reason why you see much more UDP than
TCP for SIP over the WAN.








On Fri, Oct 15, 2010 at 9:06 AM, Medve, Steve <smedve at redcom.com> wrote:
> Yes
>
>
>
> TCP is great for accurate delivery rather than timely delivery, and can
> sometimes get into long delays while waiting for out-of-sequenced packets or
> retransmissions of lost messages/sessions. It has been said that it is not
> particularly suitable for real-time applications such as Voice over IP but,
> I’ve personally used and seen it work just fine at the larger CLEC’s
> operating in the US.  You may also choose UDP for these such applications as
> protocols like Real-time Transport Protocol (RTP) running over the User
> Datagram Protocol (UDP) are usually recommended.
>
>
>
>
>
>
>
> Steven A. Medve
>
> smedve at redcom.com
>
> http://www.redcom.com
>
>
>
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> From: discussion-bounces at sipforum.org
> [mailto:discussion-bounces at sipforum.org] On Behalf Of Sam
> Sent: Thursday, October 14, 2010 11:20 PM
> To: Vijayalakshmi
> Cc: discussion at sipforum.org
> Subject: Re: [SIPForum-discussion] Is TCP feasible for SIP??
>
>
>
> Yes ,
>
> TCP can be use, but it will attract delay.
>
>
> Regards
> Sam
>
> On Wed, Oct 13, 2010 at 12:06 PM, Vijayalakshmi <vijayalakshmi at comneti.com>
> wrote:
>
> Can I use TCP to send or receive this message. Is it feasible??
>
> My message length will be approximately 500 bytes as follows
>
>
> NOTIFY sip:1 at 56.0.0.185:5060 SIP/2.0
> Call-ID: b6b58c84e373a4e3a4cd4845166b2fa2 at 135.111.122.64
> CSeq: 1 NOTIFY
> From: <sip:1 at 135.111.122.64:5060>;tag=343833444441FFFFFFFF
> To: <sip:2 at 56.0.0.182:5060>
> Max-Forwards: 70
> Subscription-State: Active
> Event: message-summary
> Content-Type: application/simple-message-summary
> Via: SIP/2.0/TCP
> 135.111.122.64:5060;branch=z9hG4bK237262a4269abc6dd282d5f81f9d0ff2
> Content-Length: 42
>
> Messages-Waiting:YES
> Voice-Message: 1/0
>
> Thanks in Advance....
>
> Regards
> Vijayalakshmi Marudhanayagam
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-- 
M. Ranganathan