University of California, Irvine. ICS 243D – Internet Technologies - Spring 2001
Roberto Silveira Silva Filho ID# 85849631

This report describe the main aspects of the MBONE technology.

The MBONE (Internet Multicast Backbone) is a technology that allows the transmission of multicast data using current Internet routers. Some examples of applications that can benefit from this technology are the transmission of video in the Internet through multiple multimedia channels, as television, the transmission of radio, shared collaborative workspaces and teleconferencing applications.

Multicast is a technical term that defines the transmission of a piece of data (data packet) to multiple hosts. It can use many different protocols, which include multimedia transmission. The internet TCP/IP protocols were designed to convey information in a Unicast transmission mode. The packages are transmitted between peers, from one site to another, through each connection.

The Multicast transmission mode has the objective to allow the transmission of packages from a single source to many listeners. It follows an idea similar to Broadcast, a transmission mode, normally used by TV and ratio stations to "universally" distribute information through its signal. The broadcast data can be captured by anyone with the appropriate device, and within the signal range. In Networking jargon, Broadcast means the transmission of data to all the hosts in a network, whereas the Broadcast means the transmission of information to a set of these hosts.

The advantage of multicast technology is the transmission of a single information piece to multiple subscribers without the need of replication of this information. This characteristics helps in conserving the bandwidth of the network, using it in a more rational way. Another advantage is that the sender does not need to know the addresses of all the receiving hosts.

Most of the routers in the internet today do not support multicasting of packages, instead, they rely on traditional unicast TCP/IP transmission mode. The MBONE technology was created with the intent to overcome this limitation, allowing the traversal of multicast packages in the Internet. It is implemented as a virtual network (a software implemented network, as opposed to a hardware based one, that shares the same resources – wires, routers, etc. from the Internet) that runs over the TCP/IP protocols. The process of embedding multicast packages in unicast ones is called tunelling.

Unicast and Multicast routers can coexist. When a multicast package, embedded in a unicast one, reaches a mrouter (multicast router), it is unpackad and transmitted over the multicast network. Converselly, when a multicast package reaches a unicast router, it is tunelled in unicast packages and transmitted over the unicast network.

MBONE is a multicast backbone. It was created by the IETF (Internet Engineering Task Force) in 1992 It is implemented as a confederation of sites that implement the multicast over IP protocol described in the previous paragraphs. It was created as a temporary solution that eventually will be replaced when the Internet routes are replaced by IP multicast capable ones.

Much like the Internet itself, the MBONE's growth and development has been based on mutual cooperation between network service providers and users. The MBONE community is active and open. Work on tools, protocols, standards, applications, and events is a cooperative international effort.

In 1994, the first live rock concert was transmitted in the internet. The Rolling Stones multicasted 20 minutes of their November 18, 1994, Dallas Cotton Bowl concert as a promotion for a subsequent pay-per-view TV special.

Since them, radio broadcasts, in part because of their lesser bandwidth requirements, have become common on the MBONE. Some examples include episodes of "The Cyberspace Report" (a public-affairs show from KUCI 88.9 FM, the radio of the UC Irvine, California), Internet Talk Radio, and Radio Free vat.

In 1996, about 1,700 networks (in about 20 countries) were using the MBONE, a network of approximately the size that the entire Internet was in 1990.

MBONE packages have semantic similar to broadcast signals. The data trnasmitted using this technology should have a limited duration time and a restricted range. The MBONE includes procedures for limiting how far multicast packets may travel, to prevent them from saturating the entire Internet. Each packet has a time to live (TTL) value, a counter that is decremented every

time the packet passes through an mrouter. The TTL also allows the expression of range, since it is usually the case that the more routers a package travels from, the farther is the site receiving this information. For example, events of interest to the world at large are generally multicast with long TTLs -- perhaps 200 -- to guarantee that the information will reach the most distant sites.

The transmission of multimedia information over the internet can use other technologies besides the MBONE, it is the case of streamming technology software. This technology allows the sending and receiving of video and sound in real time. This technology does not use multicasting but have the advantage of not requiring as much bandwidth as this last technology. One example of such technoloty is Real Audio [Realplayer].

A list of free MBONE tools can be found in the Introduction to MBONE applications [Mbone]; Currently, MBONE is still esperimental and is subject to many research. Some of the researches in the area can be found at Microsoft [Microsoft], which is researching the integration of the multicast capabilities to their products.

[SRL96] Kevin Savetz, Neil Randall, and Yves Lepage. MBONE: Multicasting Tomorrow's Internet. IDG. April 1996. http://www.savetz.com/mbone/

[RealPlayer] http://www.real.com

[Mbone] Introduction to the Mbone. http://www-itg.lbl.gov/mbone/

[Microsoft] Microsoft MBONE Home Page. http://www.research.microsoft.com/research/BARC/mbone/