Multicasting SeminarBy:

Professor A. HannaDepartment of Computer Science,

Concordia University, Montreal Canada.

Multicasting - A Proposal for a General Architecture

Aiman Hanna J. William Atwood Department of Computer Science Department of Computer Science Concordia University Concordia University

IEEE International Conference for Telecommunication (ICT-2001) Bucharest, Romania - June 2001

Our World Large-scale communication over very high-

speed networks. – Defense & Intelligence – Medical Imaging – Education – …….

• Protocol: A set of rules for guiding communication among a set of participants

Slide 3

Slide 4

Multicasting Unicasting

UnicastingUnicasting

Slide 5

Different Features of Multicasting

• Reliability

• Scalability

• Ordering

• M-to-N Multicast

• Late-join and Early-leave Receivers

• Atomicity

Slide 6

Reliable Multicasting

• Delivery time

• Delivery atomicity– Guaranteed delivery to a member or group of

members

• Delivery order

• Sender/Receivers perspective

What is Reliability?

Slide 7

Architecture of Multicast Protocols

Bi-directional Control Flow

Multicast Data Flow

Sender

Receiver

Receiver

Receiver

Receiver

Receiver

Sender

Receiver

ReceiverReceiver

Receiver Receiver

ReceiverReceiverReceiver

ReceiverReceiver

CA

CA

CA

CA - Controlling Agent

Flat Structure Hierarchical Structure

Slide 8

Structure Impact on the Protocol

– Ideally, they should be capable of supporting:• M-to-N multicast,

• Ordering

• Sender-based reliability

– However, they are incapable of being: • Scalable

• Flat-Structured Protocols

Slide 9

– Ideally, they should be capable of supporting:• Scalability

• Receiver-based reliability

– However, it is significantly difficult for these protocols to support:

• Ordering

• Sender-based reliability

• M-to-N Multicast

Structure Impact on the Protocol

• Hierarchically-Structured Protocols

Slide 10

Reliable Multicast Protocols

• The Tree-Based Multicast Transport Protocol (TMTP)

• The Scalable Reliable Multicast Protocol (SRM)

• The Reliable Multicast Transport Protocol (RMTP)

• The Reliable Adaptive Multicast Protocol (RAMP)

• The Reliable Multicast Protocol (RMP)

• The Multicast Transport Protocol (MTP-2)

• The Local Group Based Multicast Protocol (LGMP)

• The Xpress Transport Protocol (XTP)

Major Reliable Multicast Protocols:

Slide 11

Too Many Protocols, No Standard!

M-to-N Multicast

Supported only by:

• SRM

• RMTP

• MTP-2

Guaranteed ReliabilitySupported only by:

• TMTP

• RAMP

• XTP

ScalabilitySupported only by:

• TMTP

• LGMP

• RMTP

Ordering Supported only by:

• RMP

• MTP-2

The Reality

Slide 12

Architecture for Reliable Multicast Protocols

New

• The architecture must provide, and without incurring much overhead on the protocol, nor on the network:

– Proper Reliability

– Scalability

– M-to-N Multicast

– Ordering

– Ability for:– atomicity,

– late-join and early-leave receivers,

– ……..

Goal: Achieving a standard reliable multicast protocol

Slide 13

• Scalability: – Support as many receivers as the application wishes

• M-to-N Multicast: – Must be achieved with minimal resource

consumption

– Practical Consideration: How many senders should a session have?

• Ordering: – Must be achieved with a full separation between

policies and mechanisms

• Proper Reliability:– When sender-initiated must be used, and

– when receiver-initiated must be used

Slide 14

The Significant Set

B

D

C E

F

A

Master Sender

Significant Set Multicast Address

FIRST

FIRST

FIRST

FIRST

FIRST

Multicast Transmission

Slide 15

The Significant Set

B

D

C E

F

A

Master Sender

JOIN-REQUEST

JOIN-REQUEST

JOIN-REQUEST

JOIN-REQUEST

JOIN-REQUEST

Unicast Transmission

Slide 16

The Significant Set

A

B

D

C E

F

Master Sender

JOIN-CONFIRM

JOIN-CONFIRM

JOIN-CONFIRM

JOIN-CONFIRM

JOIN-CONFIRM

Unicast Transmission

Slide 17

The Significant Set

Significant Set Multicast Address

Multicast Transmission

A

B

D

C E

F

Master Sender

FIRST

FIRST

FIRST

FIRST

FIRST

Slide 18

The Significant Set

A

B

D

C E

F

Master Sender

Unicast Transmission

Unicast Transmission, Already existing paths

JOIN-REQUEST

JOIN-REQUEST

JOIN-REQUEST

JOIN-REQUEST

JOIN-REQUEST

Slide 19

The Significant Set

A

B

D

C E

F

Master Sender

Unicast Transmission

Unicast Transmission, Already existing paths

JOIN-CONFIRM

JOIN-CONFIRM

JOIN-CONFIRM

JOIN-CONFIRM

JOIN-CONFIRM

Slide 20

The Significant Set

A

B

D

C E

F

Master Sender

Significant Set Multicast

Address

Slide 21

The Simple Receivers Set

Local Group Multicast Address

Y

X

Z

W

CA

Controlling Agent

ReceiverReceiver

ReceiverReceiver

FIRST

FIRST

FIRST

FIRST

Multicast Transmission

Slide 22

The Simple Receivers Set

Unicast Transmission

CA

Y

X

Z

W

Controlling Agent

ReceiverReceiver

ReceiverReceiver

JOIN-REQUESTJOIN-REQUEST

JOIN-REQUEST

JOIN-REQUEST

Slide 23

The Simple Receivers Set

Unicast Transmission

CA

Y

X

Z

W

Controlling Agent

ReceiverReceiver

ReceiverReceiver

JOIN-CONFIRMJOIN-CONFIRM

JOIN-CONFIRM

JOIN-CONFIRM

Slide 24

The Simple Receivers Set

CA

Y

X

Z

W

Controlling Agent

Local Group Multicast Address

ReceiverReceiver

ReceiverReceiver

Slide 25

The Global Multicast Address

• One single multicast address

• All data is sent to this multicast address

• All senders and receivers listen to that multicast address

Slide 26

Architecture for Reliable Multicast Protocols

New

RCA

R R

R RR

R

RR

CA

A

B

D

C E

F

MasterSender

R

RR

CA

R

RR

R

R R

R R

R

R

R R CA

R RRR R

RCAR

RCA

RRR R

CA

CACA

R CA

CA

CA

CA

CA

CA

R

R

RR

RR

RRR

RR

R

R

R

R R

RR

Different Local GroupMulticast Addresses

Global MulticastAddress

Slide 27

Architecture Achievements • Absolute Reliability:

– Both sender-initiated and receiver-initiated

• M-to-N Multicasting:

– Achieved using:

• only one multicast address when the number of simple receivers is zero

• two or multiple multicast addresses when the number of simple receivers is > zero

Slide 28

Architecture Achievements

• Scalability:

– High-level of scalability as a result of using a hierarchical structure and local error recovery

• Ordering:

– Flexibility from Total Ordering to no ordering

– Complete separation between policies and mechanisms

Slide 29

Disadvantages !!• Utilizing One multicast address per local group

However, that is not a real weakness!

• Local error recovery is highly supported

• Network traffic is significantly reduced

• Number of local groups is relative to the number of receivers within a session

In other words:

• Achieving high scalability, with more efficient error recovery and reduced network traffic is more advantageous than saving a small number of multicast addresses

Slide 30

Mapping to Existing Protocols

– Relatively easy

– Significant Set is an add-on to protocol design

and implementation

– Many parts of current protocol design/

implementation need not to be changed

• Mapping to Hierarchically-Structured Protocols

Slide 31

– More complex as a result of structure conversion from flat to hierarchical one

– However, many parts of current design/implementation can be used for the significant set

• Example: An existing proposal for multi-sender communication for XTP

• Mapping to Flat-Structured Protocols

Mapping to Existing Protocols

Slide 32

Questions?

Slide 33

Questions?

Slide 34

Questions?