Corey wrote: There is none. The registering UA decides how long it wants this time to be. The server then has three options. It can accept the time and use it. It can decide that it is too long. In this case it uses whatever time it sees fit and tells the UA about the time it uses in the response. Or, it finds the time too short. In this case it replies with an error message "423 Interval Too Brief" and tells the UA the minimum time it expects through the Min-Expires header field. Well, actually, there is a default case. If the UA forgets to specify an expire time or uses an illegal time, the registrar can pick whatever it wants. The most common value for this is 3600 seconds. The Standard mandates this value to use in the last case. There is three module parameters in the registrar module for this: o "default_expires" sets the time for the last case, o "min_expires" sets the minimum expire time, o "max_expires" sets the maximum expire time. So, if you think that your clients should re-register only every other hour, you can simply set | modparam ("registrar", "min_expires", 7200) Best regards, Martin