In information theory and coding theory with applications in computer science and telecommunication, error detection and correction (EDAC) or error control are techniques that enable reliable delivery of digital data over unreliable communication channels. Many communication channels are subject to channel noise, and thus errors may be introduced during transmission from the source to a receiver. Error detection techniques allow detecting such errors, while error correction enables reconstruction of the original data in many cases.
The Transmission Control Protocol (TCP) is one of the main protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, the entire suite is commonly referred to as TCP/IP. TCP provides reliable, ordered, and error-checked delivery of a stream of octets (bytes) between applications running on hosts communicating via an IP network. Major internet applications such as the World Wide Web, email, remote administration, and file transfer rely on TCP, which is part of the Transport Layer of the TCP/IP suite. SSL/TLS often runs on top of TCP.
Alternating bit protocol (ABP) is a simple network protocol operating at the data link layer that retransmits lost or corrupted messages using FIFO semantics. It can be seen as a special case of a sliding window protocol where a simple timer restricts the order of messages to ensure receivers send messages in turn while using a window of 1 bit.
High-Level Data Link Control (HDLC) is a bit-oriented code-transparent synchronous network layer protocol developed by the International Organization for Standardization (ISO). The standard for HDLC is ISO/IEC 13239:2002.
The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between nodes on a network segment across the physical layer. The data link layer provides the functional and procedural means to transfer data between network entities and may also provide the means to detect and possibly correct errors that can occur in the physical layer.
ZMODEM is a file transfer protocol developed by Chuck Forsberg in 1986, in a project funded by Telenet in order to improve file transfers on their X.25 network. In addition to dramatically improved performance compared to older protocols, ZMODEM offered restartable transfers, auto-start by the sender, an expanded 32-bit CRC, and control character quoting supporting 8-bit clean transfers, allowing it to be used on networks that would not pass control characters.
XMODEM is a simple file transfer protocol developed as a quick hack by Ward Christensen for use in his 1977 MODEM.ASM terminal program. It allowed users to transmit files between their computers when both sides used MODEM. Keith Petersen made a minor update to always turn on "quiet mode", and called the result XMODEM.
YMODEM is a file transfer protocol used between microcomputers connected together using modems. It was primarily used to transfer files to and from bulletin board systems. YMODEM was developed by Chuck Forsberg as an expansion of XMODEM and was first implemented in his CP/M YAM program. Initially also known as YAM, it was formally given the name "YMODEM" in 1985 by Ward Christensen, author of the original XMODEM.
In data communications, flow control is the process of managing the rate of data transmission between two nodes to prevent a fast sender from overwhelming a slow receiver. It provides a mechanism for the receiver to control the transmission speed, so that the receiving node is not overwhelmed with data from transmitting node. Flow control should be distinguished from congestion control, which is used for controlling the flow of data when congestion has actually occurred. Flow control mechanisms can be classified by whether or not the receiving node sends feedback to the sending node.
Go-Back-N ARQ is a specific instance of the automatic repeat request (ARQ) protocol, in which the sending process continues to send a number of frames specified by a window size even without receiving an acknowledgement (ACK) packet from the receiver. It is a special case of the general sliding window protocol with the transmit window size of N and receive window size of 1. It can transmit N frames to the peer before requiring an ACK.
Selective Repeat ARQ/Selective Reject ARQ is a specific instance of the automatic repeat request (ARQ) protocol used to manage sequence numbers and retransmissions in reliable communications.
In two-way communication, whenever a frame is received, the receiver waits and does not send the control frame back to the sender immediately. The receiver waits until its network layer passes in the next data packet. The delayed acknowledgment is then attached to this outgoing data frame. This technique of temporarily delaying the acknowledgment so that it can be hooked with next outgoing data frame is known as piggybacking.
Binary Synchronous Communication is an IBM character-oriented, half-duplex link protocol, announced in 1967 after the introduction of System/360. It replaced the synchronous transmit-receive (STR) protocol used with second generation computers. The intent was that common link management rules could be used with three different character encodings for messages. Six-bit Transcode looked backwards to older systems; USASCII with 128 characters and EBCDIC with 256 characters looked forward. Transcode disappeared very quickly but the EBCDIC and USASCII dialects of Bisync continued in use.
The Stream Control Transmission Protocol (SCTP) has a simpler basic packet structure than TCP. Each consists of two basic sections:
- The common header, which occupies the first 12 bytes. In the adjacent diagram, this header is highlighted in blue.
- The data chunks, which form the remaining portion of the packet. In the diagram, the first chunk is highlighted in green and the last of N chunks (Chunk N) is highlighted in red. There are several types, including payload data and different control messages.
A sliding window protocol is a feature of packet-based data transmission protocols. Sliding window protocols are used where reliable in-order delivery of packets is required, such as in the data link layer as well as in the Transmission Control Protocol (TCP). They are also used to improve efficiency when the channel may include high latency.
In data networking, telecommunications, and computer buses, an acknowledgment (ACK) is a signal that is passed between communicating processes, computers, or devices to signify acknowledgment, or receipt of message, as part of a communications protocol. The negative-acknowledgement is a signal that is sent to reject a previously received message or to indicate some kind of error. Acknowledgments and negative acknowledgments inform a sender of the receiver's state so that it can adjust its own state accordingly.
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.
Janus is a file transfer protocol for use on bulletin board systems (BBSs). It has the relatively rare feature that it is fully bidirectional, allowing the protocol to upload and download files at the same time. It was written by Rick Huebner in 1987; Huebner had previously written a ZMODEM module for the Opus-CBBS system.
This article provides information about the communications aspects of Universal Serial Bus, USB: Signaling, Protocols, Transactions.
MEGAlink is a file transfer protocol for modem-equipped microcomputers written by Paul Meiners in 1987. Like many protocols of the era, MEGAlink is an expanded version of the seminal XMODEM. While it was a relatively simple and high-performance system, it remains relatively obscure because it was overshadowed by ZMODEM, which had been released a year earlier and saw rapid uptake.
