Multicast Transport Protocols:
A Survey and Taxonomy
Author: Katia Obraczka
University of Southern California
Presenter: Venkatesh Prabhakar
Contents
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Introduction
Taxonomy
Survey of Multicast Transport Protocols
Conclusion
Introduction
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Earlier mechanisms
 General solutions to the group
communication problem
Recent trends focus on
 Multipoint interactive applications
 Data Dissemination applications
Taxonomy
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Data Propagation
Reliability Mechanism
Repair request
Feedback Control
Retransmission
Flow and Congestion Control
Locus of Control
Ordering
Group Management
Target Application
Taxonomy
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Data Propagation
 Multicast, some work with unicast too
Reliability Mechanism
 Receiver initiated through NACKs
 Special site for feedback control
 Avoiding losses
 Forward Error Correction
 Hybrid approach
Taxonomy
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Repair request and Retransmission
 Point to Point or to the whole group
 NACK suppression
 Local recovery
Feedback Control
 Structure based - designated site or control
structure
 Timer based – probabilistic feedback
suppression
Taxonomy
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Flow and Congestion Control
 Rate, window and token based schemes
 Layered Multicast – Encoding to different
layers
 Forward Error Correction techniques
 Representative based congestion control
Control
 Distributed Vs Centralized
Ordering
 Assigning sequence numbers
Taxonomy
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Group Management
 Implicit or Explicit
 Variation: Authorization only while joining
Target Application
 Generic ones
 Delay sensitive real time services
 Reliable transfers
 Resilience as opposed to reliability
General Purpose Protocols
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Reliable Broadcast Protocol
 Multipoint communication between sites
connected by a local broadcast network
 Messages multicast through a token site
 Token site multicasts ACKs
 NACKs sent to Token site upon Packet loss
 Token site rotated among group members
General Purpose Protocols
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Multicast Transport Protocol
 Reliable and globally ordered delivery
 Group Master coordinates members
 Transmits tokens which provide
ordering, congestion control
 Group membership allowed only when
all transmit tokens are with the master
 Retransmission NACK based
 Uses fixed size transmission window
General Purpose Protocols
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Reliable Multicast Protocol
 Name service advertises multicast groups,
and flow and congestion control schemes
 Dynamic group updation
 TCP-like congestion control – Timers, ACKs
and NACKs used to control window size
 Reliability through multicasting NACKs
General Purpose Protocols
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Xpress Transport Protocol
 Designed to support a wide range of
applications
 Explicit multicast group management
protocol (MGM)
 TCP-like fully reliable delivery, UDP-like
best effort delivery and Fast NACK modes.
 Sender can select ACK frequency
 Window and rate based flow control
General Purpose Protocols
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Uniform Reliable Group Communication
Protocol
 Reliable ordered communication though a
coordinator
 All sites keep history and coordinator
knows the most up-to-date site
Reliable Multicast Framework
 Provide framework to develop multicast
protocols for various applications
Support for Multipoint
Interactive Applications
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Multicast Transport Protocol-2
 Immediate joins
 Master recovery
 Dynamic group parameter adjustment
Real-Time Transport Protocol
 Does not assure ordered reliable delivery
 RTCP used for control information
 Avoids packet losses using probabilistic
polling of set of receivers to compute rates
Support for Multipoint
Interactive Applications
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Scaleable Reliable Multicast
 Distributed protocol
 Group management by join and session
messages
Log Based Receiver-Reliable Multicast
 Logging server (LS) logs all packets
 LS ACKs senders and Receivers NACK LS
 Secondary logging servers used as proxies
and for local recovery
Support for Multipoint
Interactive Applications
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Reliable Adaptive Multicast Protocol
 NACK based reliable delivery
 Burst and idle modes
 Rate based flow control
Transport Protocol for Reliable Multicast
 Interactive Multimedia applications
 Group membership handled by application
 Multicasting NACKs and probabilistic NACK
suppression
Support for Data
Dissemination Services
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Muse
 Posting multicast news articles
 Uses cryptographic checksums and
signatures on data for authentication
 Keep-alive messages
Multicast Dissemination Protocol
 Fragments files to MDUs
 Recovery by source asking receivers for
retransmission requests at end of
transmission
Support for Data
Dissemination Services
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Adaptive File Distribution Protocol
 Group management done by a designated
group secretary
 No recovery mode for site failures or
network partitions
Tree-Based Multicast Transport Protocol
 Control Tree Structure – Domain manager
 Max tree degree defined
 ACKs and NACKs limited in scope
Support for Data
Dissemination Services
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Reliable Multicast Transport Protocol
 Control Tree – Designated Receivers
 Reclaim buffers on ACKs from children
 Window based flow control
Multicast File Transfer Protocol
 Modes: Unicast, Broadcast and Multicast
 Two pass Data Transmission protocol
 Open and closed Group Management
Interactivity Vs Reliabilty
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Resilient multicast delivery model
Structure Oriented Resilient Multicast
 Dynamic distribution graph
 Unicasts NACK to each parent
 Extended Ring Search (ERS) to look for
parents
 Nodes measure parents performance and
react to it
 Mechanism to avoid loops provided
Conclusion
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Summary
 Survey and Classification of most Multicast
Transport Protocols presented
 Multicast Congestion Control – big research
area
My Opinion
 Provides good pointers to the existing
protocols
 Emphasizes the Application Level Framing
trend in Multicast Transport Protocols