multicasting concepts,algoritms,protocols

8/8/2019 MultiCasting Concepts,Algoritms,Protocols

1/36

MULTICASTING

Concepts, Algorithms and Protocols


2/36

Introduction

What is Multicasting?

Real Life Applications of Multicasting

Multicasting

Online TV, Radio

Video

Conferencing

Stock MarketUpdates

Internet Gaming


3/36

Concepts

Groups in Multicasting

Multicasting Addressing

Managed by IANA(Internet Assigned Numbers Authority)


4/36

IANA Approvedaddress Range

224.0.0.0-239.255.255.255

Special Purposese.g.(to exchange linkstate information)

224.0.0.0-224.0.0.255

Globally ScopedAddresses

224.0.1.0-238.255.255.255


5/36

Ethernet MAC Address Mapping Technique using

Multicast IP address

IANA owned block of Ethernet MAC addresses start

with 01:00:5E in hexadecimal and half of this block isallocated for multicast addresses


6/36

IGMP(Internet Group Management Protocol)

For Dynamically Registration of the Hosts in

Multicast Network

IGMP Packet Format

Type field (indicating different types of IGMP packets) Type 11 is the IGMP membership query.

Type 12 is the IGMP version 1 membership report.

Type 16 is the IGMP version 2 membership report.


7/36

Versions of IGMP


8/36

Algorithms

Multicasting Routing Algorithms

Flooding

Spanning Trees

Reverse Path Forwarding (RPF)

Truncated Reverse Path Forwarding (TRPF)

Core Based Trees (CBT)


9/36

Flooding

Simplest Algorithm

Serious Drawbacks

Pointless Duplicate Copies

Bandwidth Wastage

Inefficient usage of Router Memory


10/36

Spanning Trees

Efficient than Flooding Algorithm


11/36

Spanning Trees

Advantage

Router will have to keep track of only 1 field

Disadvantages

Centralizes all Traffic on a single link

Doesn't consider the Group Membership


12/36

Reverse Path Broadcast (RPF)

Modified form of Spanning Trees

Implicitly Spanned Trees for each source

A more refined approach for improvingR

PB


13/36

RPB

Advantage

Very Fast

Better Utilization of Network

Disadvantage

Doesnt take into account the Multicast GroupMembership info.


14/36

Truncated Reverse Path Broadcast(TRPB)

Proposed to overcome some of the limitations of

RPB algorithm

IGMP practiced

Concept of Leaf Router

Drawback

Unnecessary traffic on Non-Leaf Subnets which dont

have the group member


15/36

Reverse Path Multicasting(RPM)

An enhancement to RPB and TRPB

Delivery Tree spans only if:

Subnetwork has a Group Member

Routers and Subnetworks along shortest path


16/36

RPM

Prune Message

Truncation of a Delivery Tree


17/36

RPM

Prune State should be Refreshed at regular

intervals

Drawback

Relatively Large Router Memory Space needed for

maintaining state information


18/36

Core Based Trees(CBT)

Most Latest Algorithm

One of its kind

Creates a single delivery tree for each group

Core of CBT

Unicast system is also used


19/36

CBT In Service


20/36

CBT

Advantage

Routers will have to keep less info

Network Bandwidth Conserved

Disadvantage

Single Tree may lead to Traffic concentration


21/36

Protocols

Distance Vector Multicast Routing Protocol (DVMRP)

Multicast Extension to OSPF (MOSPF)

Protocol Independent Multicast (PIM)

PIM-DM (for densely spaced Members)

PIM-SM (for sparsely spaced Members)


22/36

Distance Vector Multicast Routing Protocol(DVMRP)

Formulated from RIP(Routing Information Protocol)

Difference Between RIP and DVMRP

Earlier Versions Uses RPB and TRPB

Latest Tactic is to useRPM

Grafting Back in case of new Joining


23/36

Multicast Extension to OSPF (MOSPF)

Build on top of OSPF

Delivery Tree Constructed using IGMP and OSPF

database

Most significant aspect:

Support of Hierarchal Routing


24/36

MOSPF

Hierarchal Routing

Intra-Area Routing

Inter-Area Routing

Inter-AS Routing

Internet

AS-1

Area-1 Area-2

AS-2

Area


25/36

MOSPF

Intra-Area Routing

OSPF link state database is used

Group-Membership-LSA

Forwarding Cache at each Router


26/36

MOSPF

Inter-Area Routing

ABRs as inter-area multicast forwarders

Wild-Card Multicast Receivers


27/36

MOSPF

Inter-AS Routing

The technique used is very similar to Inter-Area Routing


28/36

Protocol-Independent Multicast(PIM)

Being Developed by IDMR a working group of IETF

Objective is to develop a Multicast Routing Protocol

independent of any particular Unicast Protocol

Deficiency of DVMRP and MOSPF

No good for sparsely distributed group members


29/36

PIM

To address the issue of sparsely spaced members

PIM introduces 2 protocols:

PIM-DM (efficient for dense distributions)

PIM-SM (efficient for sparse distributions)

Both use same control messages


30/36

PIM-DM(DENSE MODE)

Uses a push model

Very efficient if active members on each subnet

Flood and Prune Mechanism


31/36

PIM-SM(SPARSE MODE)

Uses a pull model

Major Difference between PIM-SM and other stated

Protocols

Introduction of Rendezvous Point (RP)


32/36

PIM-SM(SPARSE MODE)


33/36

PIM-SM(SPARSE MODE)

Source to Group Sends


34/36

MBone(Multicast Backbone)

Launched in 1992

At Start: 40 subnets in 4 countries

Now-a-Days: 3400 subnets in 25 different countries

November 1994 Rolling Stones concert at the CottonBowl in Dallas with 50,000 fans was the "first majorcyberspace multicast concert" Mick Jagger opened theconcert by saying,

"I wanna say a special welcome to everyone that's, uh, climbed into the Internet tonightand, uh, has got into the M-bone. And I hope it doesn't all collapse."


35/36


36/36

multicasting concepts,algoritms,protocols

Documents