We have an issue of registration been negotiated with the server, but some time if the registration got expired in the server before the agreed time with the polycom VVX handset, the server sends with expires=0. How to make the VVX handset to re-register immedietly with the server as soon as the registration is expired at the server? Currently the VVX handset waits less than or equal to 60 seconds to send the new register.
This is the configuration we have use in our handset.
You don't mention what SIP server you are using but you may have option around sending the expires notification before the registration expires. You can also try turning down the expires.overlap setting.
A global parameter that sets the number of seconds before the expiration time returned by server x after which the phone attempts to resubscribe.