Re: [reSIProcate-users] SIP messages limits for UDP in reSIProcate

[Scott Godin <sgodin@xxxxxxxxxxxxxxx>]

The stack decides to which transport to use based on the results of the DNS NAPTR lookup for the message destination.  The NAPTR records can prefer TCP over UDP.  (This seems to be a good writeup:  http://anders.com/cms/264/).  Also if the stack blacklists a UDP DNS result because it is unreachable, then it will use TCP instead.

An application can force a particular protocol in many different ways:

1.  Use a DUM profile outbound proxy setting (Profile::setOutboundProxy) with a transport=TCP parameter on the outbound URI.

2.  Use the DUM profile setting setFixedTransportPort to force the transport selection logic to a particular transport - this only works if you use a different port for UDP and TCP.

3.  Lower level - Add the transport parameter (ie: ;transport=TCP) to the request URI or Route header of any message.

4.  Lower level - pre-populate the Via header in each SipMessage with an IP address/port of the transport and a transport parameter (ie: ;transport=TCP).

Note:  All of these methods will end up circumventing the NAPTR lookup stage of the DNS records, since there is no point in checking which protocol to use, if the application is fixing it.  Some will also circumvent SRV look ups as well (the ones that lock to a particular IP or port).

I'm sure there are more ways I'm forgetting.

Scott

On Wed, Dec 23, 2015 at 3:31 PM, Julio Cesar Esteves Cabezas <jcabezas@xxxxxxxxxxxxx> wrote:

Hi Scott,

  I understand and I have 2 questions:

  - So, what is today the bonus of adding both UDP and TCP transports instead of only UDP, since it seems to always prefer and use UDP ?
  Maybe stack switches transport if it cannot get a response using the first tried transport ?

  - How an application, knowing the SIP message size, could command the stack to switch the transport, on-the-fly and on a message-by-message or dialog-by-dialog basis ?

Many thanks,
Julio.

--------------------------------
From: slgodin@xxxxxxxxx [mailto:slgodin@xxxxxxxxx] On Behalf Of Scott Godin
Sent: Wednesday, December 23, 2015 5:52 PM
To: Julio Cabezas
Cc: resiprocate-users@xxxxxxxxxxxxxxx
Subject: Re: [reSIProcate-users] SIP messages limits for UDP in reSIProcate

There is nothing in the stack today to automatically switch from UDP to TCP based on the message size.  The application would need to be responsible for that.  You may want to consider just enabling TCP only.

Sounds like a feature to consider for a future release.  :)

Scott

On Wed, Dec 23, 2015 at 2:37 PM, Julio Cesar Esteves Cabezas <jcabezas@xxxxxxxxxxxxx> wrote:
Hi,

    I noticed in my UA application that the dum/resiprocate stack is sending and receiving UDP packets well above the 1300 bytes limit recommended in RFC3261.  (e.g. 5000 bytes)

    I think that allowing SIP over UDP above 1300 bytes is an useful behaviour in some scenarios (despite RFC3261) but undesirable in others.

    Suppose I have activated both UDP and TCP transports in an UserAgentMasterProfile.
    Is there any configuration to select the behaviour between "allow any UDP datagram size" and "switch automatically to TCP when sending SIP message above 1300 bytes" ?

    I am using reSIProcate 1.8.14 in Windows 7.


Best Regards,
Julio.


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