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- NACK-Oriented Reliable Multicast (NORM) is a transport layer Internet protocol designed to provide reliable transport in multicast groups in data networks. It is formally defined by the Internet Engineering Task Force (IETF) in Request for Comments (RFC) 5740, which was published in November 2009. NORM operates on top of the User Datagram Protocol (UDP), and ensures reliable communication based upon a negative acknowledgement (NACK), selective Automatic Repeat Request (ARQ) mechanism, as opposed to the positive acknowledgement (ACK) approach that the standard Transmission Control Protocol (TCP) uses. In other words, receivers using NORM only send feedback when they do not receive a packet, as opposed to the TCP model where receivers regularly acknowledge packet receipt as part of it protocol operation. This allows NORM to support large-scale receiver groups. To support further scalability, NORM also employs packet erasure coding using forward error correction (FEC) codes coupled with suppression of redundant NACK feedback from the receiver group. Additionally, NORM can be configured to operate with “silent receivers” relying upon its packet erasure coding for high assurance delivery, thus operating as a broadcast-only protocol. The FEC can be configured to be used either reactively (with NACKing receivers) or proactively (silent receivers), or in a hybrid manner that allows tradeoffs in latency and network overhead. Along with supporting reliable transport, NORM also provides TCP-compatible congestion control as well as end-to-end flow control. Unlike TCP, which uses the ACK mechanism for congestion control and flow control, NORM uses separate mechanisms for each. This allows for a wide variety of configurations to meet different application data delivery needs. NORM also supports additional signaling mechanisms to facilitate session control, application-controlled positive acknowledgement, and other functions towards building complete point-to-point and group network communications applications that are highly robust and efficient. Although NORM was developed primarily to support multicast group communication, it also supports unicast (point-to-point) data transfers. (en)
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- 42401 (xsd:nonNegativeInteger)
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- NACK-Oriented Reliable Multicast (NORM) is a transport layer Internet protocol designed to provide reliable transport in multicast groups in data networks. It is formally defined by the Internet Engineering Task Force (IETF) in Request for Comments (RFC) 5740, which was published in November 2009. NORM also supports additional signaling mechanisms to facilitate session control, application-controlled positive acknowledgement, and other functions towards building complete point-to-point and group network communications applications that are highly robust and efficient. (en)
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- NACK-Oriented Reliable Multicast (en)
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