Solved: cucm-ip-phone-SIP-keepalive-and-failover-architecture-SRST

Ayodeji Okanlawon · ‎10-28-2016

Guys

Does any one know what the fail over arhitecture is for SIP phones in SRST. For SCCP phones, the IP phones send two keep-alives: TCP and SCCP and waits for CUCM to send ACK to both before registering back to CUCM.

What is the architecture for SIP phones. Does it just use the sip station keep alive?

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Adarsh Chauhan · ‎11-14-2016

Hi,

You might find your answer in here

The SIP phone registers to the CUCM and sends keep-alive every 120 seconds as per the settings in CUCM. When the phone sends the initial register to primary CUCM, it sets the Expires timer to 3600 seconds (default set in SIP profile applied on the phone). CUCM sends an ACK by modifying the timer to 120 seconds as per the value set in Service parameter.

Therefore, the phone sends keep-alive every 120 seconds (actually 115 seconds which is 120 minus the delta value configured in SIP profile, which is 5 seconds by default). In this case, the phone sends keep-alive every 115 seconds.

SIP phone exchanges the Register message to Backup CUCM with Expires field set to 0.

Also, you might want to refer to:

Support Forum Previously asked question

Please rate if helpful.

Regards,

Adarsh Chauhan

Please rate and mark correct if helpful
Regards,
Adarsh Chauhan

View solution in original post

ausjustin · ‎11-13-2016

i had problem with SRST for SIP phone not failover back to CUCM when the CUCM off line .

the only solution is manually reboot the handset or shutdown the phone interface from the switch then can bring back the phone reg to CUCM .

SO anyone how can resolve this issue ?

gio_nweng · ‎12-29-2017

Hi,

I have same issue, any permanent fix know for the SIP phone.

Regards,

Geeta

Adarsh Chauhan · ‎11-14-2016

Hi,

You might find your answer in here

The SIP phone registers to the CUCM and sends keep-alive every 120 seconds as per the settings in CUCM. When the phone sends the initial register to primary CUCM, it sets the Expires timer to 3600 seconds (default set in SIP profile applied on the phone). CUCM sends an ACK by modifying the timer to 120 seconds as per the value set in Service parameter.

Therefore, the phone sends keep-alive every 120 seconds (actually 115 seconds which is 120 minus the delta value configured in SIP profile, which is 5 seconds by default). In this case, the phone sends keep-alive every 115 seconds.

SIP phone exchanges the Register message to Backup CUCM with Expires field set to 0.

Also, you might want to refer to:

Support Forum Previously asked question

Please rate if helpful.

Regards,

Adarsh Chauhan

Please rate and mark correct if helpful
Regards,
Adarsh Chauhan

Ayodeji Okanlawon · ‎11-15-2016

Thank you Adarsh. This is excellent

Please rate all useful posts

raghukan · ‎07-04-2020

Hi Adarsh,

The explanation is pretty clear regarding the keep alive mechanism of SIP phones with CUCM.

I have one doubt, suppose if the primary call manager went down. To register the phone to secondary call manager it will take 115 seconds i.e., almost 2 minutes?

Roger Kallberg · ‎07-05-2020

AFAIK SIP phones would as with SCCP phones maintain a list of CUCM CPE nodes, aka nodes that run the Call Manager service, and fail over to the secondary instantaneous if the primary is down.