Subject: multicast tunneling From: "Ahmet Uyar" Date: Wed, 28 Mar 2001 11:47:25 -0500 To: "Geoffrey Fox" CC: "Gurhan" , "Hasan Bulut" On the multimedia meeting we had some time ago, One of the question we had was how does tunneling done on multicast networks? here is an explanation for it from http://www.cs.columbia.edu/~hgs/internet/mbone-faq.html#MBONE How do IP multicast tunnels work? IP multicast packets are encapsulated for transmission through tunnels, so that they look like normal unicast datagrams to intervening routers and subnets. A multicast router that wants to send a multicast packet across a tunnel will prepend another IP header, set the destination address in the new header to be the unicast address of the multicast router at the other end of the tunnel, and set the IP protocol field in the new header to be 4 (which means the next protocol is IP). The multicast router at the other end of the tunnel receives the packet, strips off the encapsulating IP header, and forwards the packet as appropriate. Ahmet Uyar Ph.D. candidate Computational Science and Information Technology Florida State University