Reliable multicast
Encyclopedia
A reliable multicast protocol is a computer networking protocol that provides a reliable sequence of packets to multiple recipients simultaneously, making it suitable for applications like multi-receiver file transfer
or streaming media
.
is a network addressing method for the delivery of information
to a group of destinations simultaneously using the most efficient strategy to deliver the messages over each link of the network only once, creating copies only when the links to the multiple destinations split (typically network switch
es and routers). However, like the User Datagram Protocol
, multicast does not guarantee the delivery of a message stream. Messages may be dropped, delivered multiple times, or delivered out of order. A reliable multicast protocol adds the ability for receivers to detect lost and/or out-of-order messages and take corrective action (similar in principle to TCP
), resulting in a gap-free, in-order message stream.
However, not all reliable multicast protocols ensure this level of reliability; many of them trade efficiency for reliability, in different ways. For example, while TCP
makes the sender responsible for transmission reliability, multicast NAK
-based protocols shift the responsibility to receivers: the sender does never know for sure that all the receivers have in fact received all the data.
RFC 2887 explores the design space for bulk data transfer, with a brief discussion on the various issues and some hints at the possible different meanings of reliable.
File transfer
File transfer is a generic term for the act of transmitting files over a computer network or the Internet. There are numerous ways and protocols to transfer files over a network. Computers which provide a file transfer service are often called file servers. Depending on the client's perspective the...
or streaming media
Streaming media
Streaming media is multimedia that is constantly received by and presented to an end-user while being delivered by a streaming provider.The term "presented" is used in this article in a general sense that includes audio or video playback. The name refers to the delivery method of the medium rather...
.
Overview
MulticastMulticast
In computer networking, multicast is the delivery of a message or information to a group of destination computers simultaneously in a single transmission from the source creating copies automatically in other network elements, such as routers, only when the topology of the network requires...
is a network addressing method for the delivery of information
Information
Information in its most restricted technical sense is a message or collection of messages that consists of an ordered sequence of symbols, or it is the meaning that can be interpreted from such a message or collection of messages. Information can be recorded or transmitted. It can be recorded as...
to a group of destinations simultaneously using the most efficient strategy to deliver the messages over each link of the network only once, creating copies only when the links to the multiple destinations split (typically network switch
Network switch
A network switch or switching hub is a computer networking device that connects network segments.The term commonly refers to a multi-port network bridge that processes and routes data at the data link layer of the OSI model...
es and routers). However, like the User Datagram Protocol
User Datagram Protocol
The User Datagram Protocol is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol network without requiring...
, multicast does not guarantee the delivery of a message stream. Messages may be dropped, delivered multiple times, or delivered out of order. A reliable multicast protocol adds the ability for receivers to detect lost and/or out-of-order messages and take corrective action (similar in principle to TCP
Transmission Control Protocol
The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
), resulting in a gap-free, in-order message stream.
Reliability
The exact meaning of reliability depends on the specific protocol instance. A minimal definition of reliable multicast is eventual delivery of all the data to all the group members, without enforcing any particular delivery order.However, not all reliable multicast protocols ensure this level of reliability; many of them trade efficiency for reliability, in different ways. For example, while TCP
Transmission Control Protocol
The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
makes the sender responsible for transmission reliability, multicast NAK
NAK (protocol message)
The NAK protocol message is sent in many communications protocols to negatively acknowledge or reject a previously received message, or to indicate some kind of error....
-based protocols shift the responsibility to receivers: the sender does never know for sure that all the receivers have in fact received all the data.
RFC 2887 explores the design space for bulk data transfer, with a brief discussion on the various issues and some hints at the possible different meanings of reliable.
Existing or proposed protocols
- Pragmatic General MulticastPragmatic General MulticastPragmatic General Multicast is a reliable multicast transport protocol. PGM provides a reliable sequence of packets to multiple recipients simultaneously, making it suitable for applications like multi-receiver file-transfer.-Overview:...
(PGM) - Tibco SoftwareTibco SoftwareTIBCO Software Inc. is a provider of infrastructure software for companies to use on-premise or as part of cloud computing environments. TIBCO manages information, decisions, processes and applications in real-time for over 4,000 customers worldwide...
's TRDP (part of RVTIBCO RendezvousTIBCO Rendezvous is a software product that provides a message bus for enterprise application integration .-Details:TIBCO provides messaging APIs in C, C++, Java, Visual BASIC, Perl and .NET to receive data feeds on MS Excel spreadsheets and other applications of choice.The basic message passing is...
). Note: when Tibco acquired TalarianTalarianTalarian was a provider of real-time infrastructure software. Now part of TIBCO, it was a veteran provider of message-oriented middleware.Talarian was a member of the Business Integration Group , the Internet Protocol Multicast Initiative , the Securities Industry Middleware Council , the Object...
, they inherited a PGM implementation with SmartSockets (SmartPGM). TRDP pre-dates the development of SmartPGM - 29West29West29West Inc., now a business unit of Informatica , is a computer networking software company based in the Chicago area specializing in Message Oriented Middleware...
's LBT-RM protocol (part of LBM/UME) - RTIRTI- Broadcasters :* Radiodiffusion Television Ivoirienne - The state broadcaster of Ivory Coast* Radio Taiwan International* Reti Televisive Italiane, Mediaset group * RTI Colombia, a TV production company- Other companies :...
's reliable multicast protocol (part of NDDS) - OpenDDSData Distribution ServiceData distribution service for real-time systems is a specification of a publish/subscribe middleware for distributed systems created by the Object Management Group in response to the need to standardize a data-centric publish-subscribe programming model for distributed systems.- History :A few...
as an open source implementation since their 0.12 release - Reliable Multicast Transport Protocol (RMTP)
- Scalable Reliable Multicast (SRM)
- QuickSilver Scalable Multicast (QSM)
- SMART MulticastSMART MulticastSMART Multicast is an experimental method of Secure Reliable IP Multicast. It allows a user to forward IP datagrams to an unlimited group of receivers...
(Secure Multicast for Advanced Repeating of Television) - NACK-Oriented Reliable Multicast Protocol (NORM)
- Reliable Stream Protocol (RSP), a high-performance open source protocol for compute clusters