Dear Mr. Gene, There is an assumption in your theory that the endpoint may be doing a favor to the network by providing frequent keep alives. But, What I feel is, the TTL specified by the endpoint is the value it seems, it is going to be alive. (The definition of being alive here may mean the agreement duration with the service provider or it may be the time for which you are present in the cyber cafe...). This way, the endpoint is telling that it intends to use the services of the Gatekeeper for this much duration. Now, the Gatekeeper, in opposition to this, may say that I need to know every nth minute that you are still there. The reason may be, every nth minute, the gatekeeper will like to change the security information. By forcing the endpoint to reregister every nth second, it can change the security information. And, as you yourself have said that the Gatekeeper has better knowledge of the condition of the network. So, given the maximum time the EP wants to work with the gatekeeper, the GK may select the optimum value of the TTL, which will always be less than or equal to the TTL.crumb=v8.e34f9bxp, Dear Mr. Gene, There is an assumption in your theory that the endpoint may be doing a favor to the network by providing frequent keep alives. But, What I feel is, the TTL specified by the endpoint is the value it seems, it is going to be alive. (The definition of being alive here may mean the agreement duration with the service provider or it may be the time for which you are present in the cyber cafe...). This way, the endpoint is telling that it intends to use the services of the Gatekeeper for this much duration. Now, the Gatekeeper, in opposition to this, may say that I need to know every nth minute that you are still there. The reason may be, every nth minute, the gatekeeper will like to change the security information. By forcing the endpoint to reregister every nth second, it can change the security information. And, as you yourself have said that the Gatekeeper has better knowledge of the condition of the network. So, given the maximum time the EP wants to work with the gatekeeper, the GK may select the optimum value of the TTL, which will always be less than or equal to the TTL __________________________________________________ Do You Yahoo!? Talk to your friends online with Yahoo! Messenger. http://im.yahoo.com