--- asterisk-1.4.32/channels/chan_sip.c	2010-05-05 09:42:22.000000000 -0700
+++ asterisk-1.4.32-new/channels/chan_sip.c	2010-06-22 10:54:26.000000000 -0700
@@ -1831,7 +1831,7 @@
 static int __sip_xmit(struct sip_pvt *p, char *data, int len)
 {
 	int res;
-	const struct sockaddr_in *dst = sip_real_dst(p);
+	const struct sockaddr_in *dst = sip_real_dst(p); 
 	res = sendto(sipsock, data, len, 0, (const struct sockaddr *)dst, sizeof(struct sockaddr_in));
 
 	if (res == -1) {
@@ -4873,12 +4873,13 @@
 
 	/* See if the method is capable of creating a dialog */
 	if (sip_methods[intended_method].can_create == CAN_CREATE_DIALOG) {
+		const char *event = get_header(req, "Event");
 		if (intended_method == SIP_REFER) {
 			/* We do support REFER, but not outside of a dialog yet */
 			transmit_response_using_temp(callid, sin, 1, intended_method, req, "603 Declined (no dialog)");
-		} else if (intended_method == SIP_NOTIFY) {
-			/* We do not support out-of-dialog NOTIFY either,
-		   	like voicemail notification, so cancel that early */
+		} else if (intended_method == SIP_NOTIFY && (!event || strcmp(event, "keep-alive"))) {
+			/* We do not support out-of-dialog NOTIFY either, unless it is a
+			 * keep-alive, like voicemail notification, so cancel that early */
 			transmit_response_using_temp(callid, sin, 1, intended_method, req, "489 Bad event");
 		} else {
 			/* Ok, time to create a new SIP dialog object, a pvt */
@@ -14185,8 +14186,11 @@
 	
 	if (option_debug > 1 && sipdebug)
 		ast_log(LOG_DEBUG, "Got NOTIFY Event: %s\n", event);
-
-	if (strcmp(event, "refer")) {
+	
+	if (!strcmp(event, "keep-alive")) {
+		/* Return 200 OK for keep-alive events */
+		transmit_response(p, "200 OK", req);
+	} else if (strcmp(event, "refer")) {
 		/* We don't understand this event. */
 		/* Here's room to implement incoming voicemail notifications :-) */
 		transmit_response(p, "489 Bad event", req);