Cell relay
Encyclopedia
In computer networking
, cell relay refers to a method of statistically multiplexing
small fixed-length packets, called "cells", to transport data between computers or kinds of network equipment. It is an unreliable
, connection-oriented
packet switched
data communications protocol
.
Cell relay transmission rates usually are between 56 kbit/s and several gigabits per second. ATM
, a particularly popular form of cell relay, is most commonly used for home DSL
connections, which often runs between 128 kbit/s and 1.544 Mbit/s (DS1
), and for high-speed backbone connections (OC-3 and faster).
Cell relay protocols have neither flow control
nor error correction capability, are information-content independent, and correspond only to layers one and two of the OSI Reference Model.
Cell relay can be used for delay- and jitter-sensitive traffic such as voice and video.
Cell relay systems break variable-length user packets into groups of fixed-length cells, that add addressing and verification information. Frame length is fixed in hardware
, based on time delay and user packet-length considerations. One user data message may be segmented over many cells.
Cell relay statems may also carry bitstream-based data such as PDH
traffic, by breaking it into streams of cells, with a lightweight synchronization and clock recovery shim. Thus cell relay systems may potentially carry any combination of stream-based and packet-based data. This is a form of statistical time division multiplexing.
Cell relay is an implementation of fast packet-switching
technology that is used in connection-oriented broadband integrated services digital networks (B-ISDN, and its better-known supporting technology ATM) and connectionless IEEE 802.6
switched multi-megabit data service (SMDS
).
At any time there is information to be transmitted; the switch basically sends the data units. Connections don’t have to be negotiated like circuit switching. Channels don’t have to be allocated because channels do not exist in ATM, and on condition that there is an adequate amount of bandwidth to maintain it, there can be indefinite transmissions over the same facility.
Cell relay utilize data cells of a persistent size. Frames are comparable data packets; however they contrast from cells being they may fluctuate in size based on the prerequisite or circumstances. This type of technology isn’t secure for the reason that its procedures do not support error handling or data recovery. Per se, all delicate and significant transmissions may perhaps be transported faster via fixed-sized cells, which are simpler to transmit compared to variable-sized frames or packets.
Cell relay is extremely reliable for transporting vital data. Switching devices give the precise method to cells as each endpoint address embedded in a cell. For instance cell relay is ATM, a prevalent form utilized to transfer a cell with fixed size of 53 bytes.
Computer network
A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....
, cell relay refers to a method of statistically multiplexing
Statistical multiplexing
Statistical multiplexing is a type of communication link sharing, very similar to dynamic bandwidth allocation . In statistical multiplexing, a communication channel is divided into an arbitrary number of variable bit-rate digital channels or data streams. The link sharing is adapted to the...
small fixed-length packets, called "cells", to transport data between computers or kinds of network equipment. It is an unreliable
Reliability (computer networking)
In computer networking, a reliable protocol is one that provides reliability properties with respect to the delivery of data to the intended recipient, as opposed to an unreliable protocol, which does not provide notifications to the sender as to the delivery of transmitted data.A reliable...
, connection-oriented
Connection-oriented
Connection-oriented communication is a data communication mode in telecommunications whereby the devices at the end points use a protocol to establish an end-to-end logical or physical connection before any data may be sent. In case of digital transmission, in-order delivery of a bit stream or...
packet switched
Packet switching
Packet switching is a digital networking communications method that groups all transmitted data – regardless of content, type, or structure – into suitably sized blocks, called packets. Packet switching features delivery of variable-bit-rate data streams over a shared network...
data communications protocol
Communications protocol
A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications...
.
Cell relay transmission rates usually are between 56 kbit/s and several gigabits per second. ATM
Asynchronous Transfer Mode
Asynchronous Transfer Mode is a standard switching technique designed to unify telecommunication and computer networks. It uses asynchronous time-division multiplexing, and it encodes data into small, fixed-sized cells. This differs from approaches such as the Internet Protocol or Ethernet that...
, a particularly popular form of cell relay, is most commonly used for home DSL
Digital Subscriber Line
Digital subscriber line is a family of technologies that provides digital data transmission over the wires of a local telephone network. DSL originally stood for digital subscriber loop. In telecommunications marketing, the term DSL is widely understood to mean Asymmetric Digital Subscriber Line ,...
connections, which often runs between 128 kbit/s and 1.544 Mbit/s (DS1
Digital Signal 1
Digital signal 1 is a T-carrier signaling scheme devised by Bell Labs. DS1 is a widely used standard in telecommunications in North America and Japan to transmit voice and data between devices. E1 is used in place of T1 outside North America, Japan, and South Korea...
), and for high-speed backbone connections (OC-3 and faster).
Cell relay protocols have neither flow control
Flow control
In data communications, flow control is the process of managing the pacing of data transmission between two nodes to prevent a fast sender from outrunning a slow receiver. It provides a mechanism for the receiver to control the transmission speed, so that the receiving node is not overwhelmed with...
nor error correction capability, are information-content independent, and correspond only to layers one and two of the OSI Reference Model.
Cell relay can be used for delay- and jitter-sensitive traffic such as voice and video.
Cell relay systems break variable-length user packets into groups of fixed-length cells, that add addressing and verification information. Frame length is fixed in hardware
Hardware
Hardware is a general term for equipment such as keys, locks, hinges, latches, handles, wire, chains, plumbing supplies, tools, utensils, cutlery and machine parts. Household hardware is typically sold in hardware stores....
, based on time delay and user packet-length considerations. One user data message may be segmented over many cells.
Cell relay statems may also carry bitstream-based data such as PDH
Plesiochronous Digital Hierarchy
The Plesiochronous Digital Hierarchy is a technology used in telecommunications networks to transport large quantities of data over digital transport equipment such as fibre optic and microwave radio systems...
traffic, by breaking it into streams of cells, with a lightweight synchronization and clock recovery shim. Thus cell relay systems may potentially carry any combination of stream-based and packet-based data. This is a form of statistical time division multiplexing.
Cell relay is an implementation of fast packet-switching
Fast packet switching
In telecommunications, fast packet switching is a packet switching technique that increases the throughput by eliminating overhead. Overhead reduction is accomplished by allocating flow control and error correction functions to either the user applications or the network nodes that interface with...
technology that is used in connection-oriented broadband integrated services digital networks (B-ISDN, and its better-known supporting technology ATM) and connectionless IEEE 802.6
IEEE 802.6
IEEE 802.6 is a standard governed by the ANSI for Metropolitan Area Networks . It is an improvement of an older standard which used the Fiber distributed data interface network structure. The FDDI-based standard failed due to its expensive implementation and lack of compatibility with current LAN...
switched multi-megabit data service (SMDS
SMDS
Switched Multi-megabit Data Service was a connectionless service used to connect LANs, MANs and WANs to exchange data, in early 1990s. In Europe, the service was known as Connectionless Broadband Data Service ....
).
At any time there is information to be transmitted; the switch basically sends the data units. Connections don’t have to be negotiated like circuit switching. Channels don’t have to be allocated because channels do not exist in ATM, and on condition that there is an adequate amount of bandwidth to maintain it, there can be indefinite transmissions over the same facility.
Cell relay utilize data cells of a persistent size. Frames are comparable data packets; however they contrast from cells being they may fluctuate in size based on the prerequisite or circumstances. This type of technology isn’t secure for the reason that its procedures do not support error handling or data recovery. Per se, all delicate and significant transmissions may perhaps be transported faster via fixed-sized cells, which are simpler to transmit compared to variable-sized frames or packets.
Cell relay is extremely reliable for transporting vital data. Switching devices give the precise method to cells as each endpoint address embedded in a cell. For instance cell relay is ATM, a prevalent form utilized to transfer a cell with fixed size of 53 bytes.