Subject: Re: [MBONED] GW Address Changes (With NAT)

From: "SAYKO, ROBERT J (ATTSI)" <[email-masked]>
Date: Wed, 16 Mar 2011 14:48:59 -0400

At AT&T base on our experience,  testing and investigation we would like
to present the following recommendation as an addition to the
"Automatic IP Multicast Without Explicit Tunnels
(AMT)draft-ietf-mboned-auto-multicast-10" 

Problem:
Handling GW Address Changes:
-GW's external address (Source IP, port) can change:
	>Shift from wireline to WiFi, etc.
	>NAT device reboot or DHCP renew
-GW will present itself as a "new" tunnel to the Relay
-Relay resources can be temporarily wasted as old tunnel cannot be torn
down until Relay times it out
-In some cases, the client may receive duplicate copies of the multicast
stream until the Relay times out the "old" GW.   
 For constrained local access networks, this could cause congestion
problems for the end user.
-The GW is able to detect a change in the local network interface, which
would cover most of these scenarios, but not a 
 change in upstream NAT address

Recommendation:
-Have mechanism whereby the GW when it detects a change could teardown
the "old" tunnel
-Teardown message was introduced for this purpose
-Since the AMT GW would need to know it's external address, there is a
dependency upon the enhanced AMT Query message (per previous
recommendation entitled: "Reporting Issues with NAT")