I've been looking at XECS-2202 (kludge: use Min-Expires: 3600 value in 423 Subscription Too Brief response). The original purpose of that change is to avoid a problem with some phones, in that whenever they successfully subscribe to BLF information, they use the expiration they receive as the expiration they will request when they renew the subscription. Since sipX gives less expiration time than requested for most subscriptions (in order to ensure that resubscribe times are evenly distributed), this causes the phone's requested expiration time to shrink until it gets to the minimum that the sipX BLF server will accept. Currently, that minimum is 32 seconds, which is too small for a large number of phones to use, as it will overload the server.
The change currently documented in the issue is to raise the minimum time to 3600 seconds (1 hour), so that when a phone "ratchets down", it will stop at 3600 seconds, which is a reasonable resubscribe interval. The idea is that this is a temporary change until we can get the phone manufacturers to correct their products. After thinking about this, I think a better strategy would be to: (1) change the new minimum to 1800 seconds (30 minutes), and (2) make this change permanent. My thinking is that we do not want phones, under any circumstances, subscribing to any sipX server with sort subscriptions. (Requested subscription time of 0 (that is, a polling request) is always allowed.) 1800 seconds is a reasonable lower limit. 1800 seconds is significantly smaller than the conventional default (3600 seconds), ensuring that devices do not accidentally become unable to subscribe, and also ensuring that the "resubscribe spread" algorithm has a wide range to work with (1800 to 3600 seconds). Thoughts? Dale _______________________________________________ sipx-users mailing list sipx-users@list.sipfoundry.org List Archive: http://list.sipfoundry.org/archive/sipx-users Unsubscribe: http://list.sipfoundry.org/mailman/listinfo/sipx-users
