Why does my Polycom HDX9004 keep losing its registration with the VCS, and how can I fix this?

Introduction

This article relates to Cisco TelePresence Video Communication Server Expressway.

Q. Why does my Polycom HDX9004 keep losing its registration with the VCS, and how can I fix this?

A. This is because the Polycom endpoint does not refresh its registration within the default period required by the VCS. You can't change this setting on the Polycom endpoint, therefore in order to fix this problem you must change the setting on the VCS, so that it requires SIP registrations to be refreshed within the same time period used by the Polycom endpoint.

More information

The standard SIP registration process is as follows:

1. A SIP endpoint sends a registration request to the SIP registrar (in this case a VCS).

2. The VCS accepts the registration and advises the endpoint of the frequency with which the endpoint must refresh its registration in order to remain registered (this frequency is determined on the VCS by the SIP Registration expire delta setting).

3. The SIP endpoint sends a registration refresh request to the VCS. If the VCS does not receive this request within the frequency specified, it will remove the registration.

The default frequency on the VCS is 60 seconds; the default frequency on the Polycom HDX9004 is 300 seconds.

Normally endpoints will adjust the frequency with which they send the registration refresh requests according to the Registration expire delta information received from the SIP registrar. However, the Polycom HDX9004 does not respond to this information and continues to send the registration refresh messages every 300 seconds. This frequency is not configurable on the Polycom endpoint. If the Registration expire delta setting on the VCS requires that the refresh messages are sent more frequently than 300 seconds (which it does by default), the VCS will consider the registration to have expired after the period specified by the Registration expire delta setting. When the Polycom HDX9004 sends its next registration refresh message, the VCS considers this to be a new registration request, and so re-registers the endpoint (but only for the period specified by the its Registration expire delta setting).

The work-around for this is to change the Registration expire delta setting on the VCS (VCS configuration > Protocols> SIP > Configuration) to be greater than 300 seconds.

Note: changing the Registration expire delta setting on the VCS will affect the frequency with which all SIP endpoints must re-register, not just the Polycom HDX9004. If you have Presence enabled on the VCS, it will also affect the frequency with which the PUA updates the presence status of SIP endpoints - see The Presence status of my endpoints sometimes seems to take a while to update in VCS. How can I fix this? for more information.

Related Information

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