The Evolution of Multicast

Research paper presented by

Ajith M Jose (u4083453)

The Evolution of Multicast

This presentation discusses about:

• General Information about Multicast • Importance, types of Multicast • Description of Std IP Multicast Model • Evolution of MBone• Evolution of Intra-domain Multicast• Evolution of Inter-domain Multicast• Deployment of Inter-domain Multicast

The Evolution of Multicast

Multicast Backbone (MBone)

Intra-Domain Multicast

Inter-Domain Multicast

Std IP Multicast Model1988

1992

1994

1997

Single flat topology

Hierarchical topology

What is Multicast ?

• It is an efficient way of data distribution in Internet environment

• It provides the functionality to logically group a set of hosts/routers in a distributed fashion

• A class D IP address is used to represent a group of receivers

• All the members in a group gets the datagram sent by a member

Applications of Multicast ?

A scene from the famous network game “Shrine of the Ancient”

Distance Learning

Multimedia conferencing

Challenges Faced by Multicast

• lack of an elegant protocol

• Existing unicast infrastructure

How did the Multicast started?

The concept of Multicast originated from the “Std IP Multicast Model” described by Stephen Deering in 1988

Deering’s IP Multicast Model

Deering’s Model explains how the end systems are to send and receive the multicast packets

The main features of Deering’s Model are:

1) IP-Style Sematics

2) Open Groups

3) Dynamic Groups

Deficiencies of Deering’s Multicast Model

• Does not discuss how the network should perform routing

• No mechanism for providing quality of service, security or address allocation

Virtual Internet Backbone for Multicast IP or MBone

• MBone is a virtual network based on Deering’s IP Multicast model

• It is layered on top of the physical Internet to support routing of IP multicast packets since that function has not yet been integrated into many routers

• It is an experiment to upgrade the Internet to handle live multimedia messages

• The first MBone network was established in 1992 at the Internet Engineering Task Force (IETF) meeting in San Diego

The Structure of MBone

• The Structure of MBone is based around the use of IP Multicast protocol and the use of tunnels

• At the moment, sections of the MBone form a virtual network of "islands", interconnected using tunnels over the physical Internet

• Each tunnel connect two end points by one logical link, but could cross several Internet routers

• The tunnel endpoints are typically workstation-class machines having operating system support for IP multicast and running the daemon process "mrouted"

Topology of MBone

• gross topology of the MBone in May of 1994

Virtual Internet Backbone for Multicast IP or MBone

• Transmission of Multicast packets through the ordinary routers.

Encapsulating Multicast packet in normal IP Datagram

Protocols Used by MBone

• DVMRP (Distance Vector Multicast Routing Protocol)

-broadcast-and-prune

“Multicast Routing in MBone was a controlled form of flooding”

Virtual Internet Backbone for Multicast IP or MBone

Following graph shows the growth rate in the number of MBone sites

More than 200 sites within the first year of starting MBone

Deficiencies of MBone

• It uses only dense mode protocols

-not efficient if there are only a few group members

Intra-domain Multicast Routing is Evolving

• Why did Intra-domain Multicasting originated ? -tremendous growth in MBone since 1992 -new multicast method for satisfying the

increasing number of sites • What are the features of Intra-domain Multicasting ? -sites added to groups called Domains -Two more dense mode protocols deployed 1) Multicast Extensions to OSPF(MOSPF) 2) Protocol Independent Multicast Dense

Mode (PIM-DM)

Features of Intra-domain Multicasting

• “Sparse mode” protocols created -features of Sparse mode• Two sparse mode protocols 1)Core Based Trees (CBT) protocols 2)Protocol Independent Multicast -Sparse Mode (PIM-SM) -Rendezvous Point (RP) • New applications were created

Evolution of Inter-Domain Multicast

• With intra-domain multicasting the communication was limited to a domain

• Inter-Domain Multicast considers about the communication within a domain and between different domains

• It uses Protocols like..

1) Multicast Border Gateway Protocols (MBGP)

2) Multicast Source Discovery Protocol (MSDP)

Inter-domain Multicast Deployment

Deployment in Commodity Internet

-main challenge was to deal with the existing MBone network -MBone use tunnels to connect the sites -the solution was to put MBone as a separate AS called

AS10888 -connectivity between AS10888 and other multicast capable

AS’s was provided at the NASA Multicast friendly Internet eXchange (NASA MIX)

Inter-domain Multicast Deployment

Deployment in Internet2• The deployment was based on the guidelines set by the

Internet2 Multicast working group • The main task was to deploy the Inter-domain Multicast in the

two backbones1) vBNS -Since the start in 1995 ,was using dense mode protocols -due to the severe data flooding problems in 1998 decided to use

protocols PIM-Sparse Mode,MBGP and MSDP -in 1999 became a complete inter-domain multicast backbone2) Abeline -Started only in 1999, so the transition to Inter-domain Multicast

was an easy process

Future of Multicast

• Future of Multicast is rooted in the continued development, evaluation and standardization of new protocols and issues like address allocation and management

Web References

http://nextinet.ncsa.uiuc.edu/nextnet/ngi/applications/videoconferencing/mbone.html

http://www.webopedia.com/TERM/M/Mbone.html

http://www-mice.cs.ucl.ac.uk/multimedia/projects/mice/mbone_review.html

http://www.serpentine.com/~bos/tech/mbone/

Types of MulticastOne-to-all• Separate Unicast transport connection to each of

the receivers• Involves only senders in sending the data• Requires explicit multicast support from the

network layer

Application-level multicast• Involves receivers also in the replication and

forwarding of data• Sender transmits a copy to a smaller number of

receivers, which then make copies themselves and forwards to the other receivers

• Significant amount of infrastructure required to maintain application level distribution architecture

Explicit multicast• Single datagram is sent from the sending host and

gets replicated at a network router whenever it must be forwarded on multiple outgoing links to reach the receivers