Overcoming Last-Hop/First-Hop Problems in IP Multicast

Whereas much of the recent thrust in IP multicast standardization has focused on multicast routing and other supplementary infrastructure for multicast, the reach to/from end-systems from/to the multicast infrastructure constitutes a significant barrier in deploying any network layer multicast protocol. A basic problem arises from the fact that current IP multicast protocols have been designed assuming universal deployment thereby preventing end-systems that are more than one router hop away to participate in multicast. This problem is further aggravated by increasing protocol awareness of layer-2 devices effectively locking particular protocols and versions into hardware, and in part by the declining transparency of the maturing Internet due to firewalls and NATs. In this paper we describe new multicast mechanisms to address these issues. While designed as part of our research on Selfconfiguring Lightweight Internet Multicast (SLIM), the techniques and mechanisms are applicable to other multicast protocols. We discuss our implementation and experimentation over the open Internet, and show how these new protocol mechanisms have enabled us to introduce our new IP multicast to end-systems in an incremental manner without the collaboration of network administrators.