________________________________________
From: [email protected] 
[[email protected]] On Behalf Of Ali Nebi 
[[email protected]]

1. Phone register to Sipxecs as the phone is set to propose expiration
time around 360s. Phone register and we see in sipx traces and logs and
web interface that the phone is registered.
2. When the timer shows around 120s until expiration time, then we see
that the phone is registering again, but it is different registration
session not the first one. So now we have 2 registrations with the same
identity. What happens is that the first registration expires and it
does not reregister. Then the second session expiration time decrease
around 120s and phone again creates anothe registration session, and
previous session expire after 120s (not exactly 120s) and it does not
reregister also.

This happens all the time for all identities that connects to Sipxecs.

What i see in Sipxecs traces is that phone gets Registration Too Brief
message. Minimum registration expiration time is 300s in sipx.

Another thing that i see in sipx is the following situation:

1. Phone send registration request with proposal for expiration time
360s.
2. Sipxecs returns "401 Unauthorized" request to the phone so phone can
register with authentication
3. Then phone sends again Register requests, but now the Expires header
is set to 120s.
4. In normal situation Sipxecs should return (200 OK), but it returns
"423 Registration Too Brief".
________________________________________

The phone is responsible for registering correctly.  There are two common 
errors that phones make when registering with sipX:

(1) When sipX accepts a registration, it does not grant the amount of time that 
was requested, but rather a random fraction of that time.  This avoids problems 
when a large group of phones is restarted at the same time.  The phone must 
detect the expiration time that is granted and reregister before that time has 
expired.

(2) When the phone re-registers, it must request the same amount of time as it 
originally requested.  Some phones request the amount of time that was 
previously granted.  Because of the randomized granting, such a phone will 
request less and less time with each registration until it requests less time 
that is permitted, and then receive a 423 error and give up.

We have also occasionally seen phones that change the Call-Id of REGISTER 
requests with each request.  This leads to multiple registrations of the same 
phone.  We have also seen phones that change the from-tag of a REGISTER request 
when it is resent in response to a 401/407 response.  That is not allowed by 
RFC 3261 and will not work with sipX.

In addition, we recommend a minimum registration request of 3600 seconds.  Most 
of the load on the sipX proxy is handling registrations (rather than calls), 
and increasing the registration request reduces that load.

You need to look at a detailed trace of REGISTER messages to determine what is 
going wrong.  You probably need to convince the phone vendor to fix its 
software.

Dale
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