[SR-Users] 422 Session timer too small

[Marco Mouta]

Overview through the RFC 4028- Session Timers in the Session
Initiation Protocol (SIP)

 Session-Expires, which conveys the lifetime of the session, and
Min-SE, which conveys the minimum allowed value for the session timer.

 Session-Expires Header Field Definition

The Session-Expires header field conveys the session interval for a
SIP session. It is placed only in INVITE or UPDATE requests, as well
as in any 2xx response to an INVITE or UPDATE.  Like the SIP Expires
header field, it contains a delta-time. The absolute minimum for the
Session-Expires header field is 90 seconds.  This value represents a
bit more than twice the duration that a SIP transaction can take in
the event of a timeout.  This allows sufficient time for a UA to
attempt a refresh at the halfpoint of the session interval, and for
that transaction to complete normally before the session expires.

However, 1800 seconds (30 minutes) is RECOMMENDED as the value for the
Session-Expires header field.  In other words, SIP entities MUST be
prepared to handle Session-Expires header field values of any duration
greater than 90 seconds, but entities that insert the Session-Expires
header field SHOULD NOT choose values of less than 30 minutes.


422 Response Code Definition


This extension introduces the 422 (Session Interval Too Small)
response code.  It is generated by a UAS or proxy when a request
contains a Session-Expires header field with a duration below the
minimum timer for the server.  The 422 response MUST contain a Min-SE
header field with the minimum timer for that server.

--
Marco Mouta


On Wed, Feb 23, 2011 at 2:00 PM, Mino Haluz <mino.haluz at gmail.com> wrote:
>
> Hi,
> I see in my cdrtool rarely 422 Session Timer too small - the reason why the call was not initiated. Do you have some suggestion how to fix this ? Maybe SST module ? What is the default value of this timer, so that I could increase it ?  kamailio 3.1.0 (i386/linux) 1e204f
> Thank  you,
> Mino
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