Multicast backbone
As Multicast Backbone , the MBone or MBONE refers to a 1992 installed expansion of the normal Internet Protocol ( IP version 4 ), after the multicasting working methods, and mainly for video was used and audio conferencing. The MBone was developed to connect multicast-capable networks via the existing Internet infrastructure
history
The MBone was developed in 1992 by Van Jacobson, Steve Deering and Stephen Casner at the suggestion of Allison Mankin.
The first activities in Germany were undertaken in mid-1993, and an MBone-DE for Germany called Whiteboard was set up
A Rolling Stones concert in November 1994 at the Cotton Bowl in Dallas with 50,000 fans was the "first major cyberspace multicast concert". Mick Jagger opened the concert with the words: "I would like to extend a special welcome to everyone who went online tonight and logged into the MBone. And I hope it doesn't all collapse."
A year later the MBone, this time symmetrical (simultaneous sending and receiving without hierarchy among the participants), was used for a first experience of graphical real-time interaction without the intermediary of a center.
Until 1995 there was MBone connections in Russia and at the research station McMurdo Sound in Antarctica.
MBone was used for shared communication such as video conference calls or shared collaborative workspaces. It was generally not associated with commercial Internet service providers, but often with universities and research institutions.
architecture
The MBONE consists of multicasting-capable computers and routers on the Internet. Since the conventional routers used on the Internet are not multicast-capable, multicast-capable subnets remain isolated on the Internet and form so-called multicasting islands. These islands can be bridged by tunneling , i.e. by encapsulating a multicast packet in a unicast packet, and thus form a global multicast network, the MBONE.
Extensive video and audio data can be transmitted over the high-speed networks of the Internet with the help of the Internet Multicast Protocol . A feature of this protocol is that the compressed and digitized data can be transmitted to different participants at the same time without the network load increasing linearly with the number of participants. In practice this means, for example, that if you are interested in an offer, you do not log on to the server, but to the network with your multicast address as a member of this group that uses an application such as a video conference. The UDP protocol is used in the transport layer, which can lead to packet loss , but the individual nodes are not overloaded.
Algorithms
The multicast backbone uses the DVMRP routing algorithm, which is based on the Bellman-Ford algorithm . The distance vector is used to select a route . In practice , in order to broadcast an audio or video program in this mode , a source broadcaster must first be assigned a class D address, which serves as a frequency or TV channel number pattern. The host selects a set multi-channel network . This happens thanks to the IGMP protocol, which sends a request to all hosts in the LAN network to find out which host is interested in a particular channel. The interested host then sends the corresponding IGMP packet. When the sending host generates a new packet, it sends it to a distributor on the network, which then sends it to all tunnels to which it is connected. When a distributor in another LAN network receives this packet, it then checks whether it was delivered on the optimal route. If it was not sent in the optimal way, it will be discarded, otherwise it will be forwarded accordingly. In order to avoid blockages, each package is given a weighting. The packet is only forwarded to tunnels if its weight does not exceed that of the tunnel weight
However, this algorithm can be modified. One possibility of modification is to give the algorithm a hierarchical structure by grouping LAN networks into regions. Then packets are first forwarded to hosts in the same region, if the recipient is not in the region, the request leaves the region and is forwarded to others.
Another possibility is to get link status information via the MOSPF protocol. Each router creates a list of connected routers and their distance, then the shortest route is calculated using an algorithm, for example the Dijkstra algorithm .
However, if members are scattered over a large area, DVMRP and MOSPF are not very efficient. In this case, the PIM protocol is used.
Usage today
IP multicasting is rarely used these days. The reason for this is the additional maintenance effort that arises from the variety of protocols, and the configuration effort also plays a decisive role. The risk of denial-of-service attacks is also higher and the use of the UDP protocol increases the processing power of the sender by correcting transmission errors.
See also
- Streaming media
- Broadcast
- Multicast
- 6Bone • M6Bone
- eXtensible Open Router Platform (XORP) • Cisco Systems • Juniper Networks
Web links
- MBoned Working Group of the IETF
- Definition at ITWissen.de
- Equipped for the multimedia age - IP network for real-time data: the multicast backbone at TecChannel.de
Individual evidence
- ↑ a b c d 12.1. Multicast Infrastructure (MBONE). Retrieved May 20, 2019 .
- ↑ The Evolution of Multicast: From the MBone to Interdomain Multicast to Internet2 Deploymen! 2000, accessed on May 20, 2019 .
- ↑ BUSINESS TECHNOLOGY; Peering Out a 'Real Time' Window. February 8, 1995, accessed May 20, 2019 .
- ↑ "VRVS Frequently Asked Questions" ( Memento of 22 February 2008 at the Internet Archive )
- ↑ a b Multicast Backbone (MBone). Retrieved May 20, 2019 .
- ↑ a b c d Systems II 4. The network layer. Retrieved May 20, 2019 .
- ↑ Internet Multicast Today - The Internet Protocol Journal - Volume 2, No. 4. Retrieved May 20, 2019 .