wide area network A wide area network (WAN) is a telecommunications network that extends over a large geographic area. Wide area networks are often established with leased telecommunication circuits. Businesses, as well as schools and government entities, us ...

computing, Link Access Procedure for Frame Relay (or LAPF) is part of the network's

communications protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchr ...

which ensures that frames are error free and executed in the right sequence. LAPF is formally defined in the

International Telecommunication Union The International Telecommunication Union is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established on 17 May 1865 as the International Telegraph Unio ...

standard Q.922. It was derived from IBM's

Synchronous Data Link Control Synchronous Data Link Control (SDLC) is a computer communications protocol. It is the layer 2 protocol for IBM's Systems Network Architecture (SNA). SDLC supports multipoint links as well as error correction. It also runs under the assumption th ...

protocol, which is the layer 2 protocol for IBM's

Systems Network Architecture Systems Network Architecture (SNA) is IBM's proprietary networking architecture, created in 1974. It is a complete protocol stack for interconnecting computers and their resources. SNA describes formats and protocols but, in itself, is not a pi ...

developed around 1975. ITU used SDLC as a basis to develop LAPF for the

Frame Relay Frame Relay is a standardized wide area network (WAN) technology that specifies the physical and data link layers of digital telecommunications channels using a packet switching methodology. Originally designed for transport across Integrated Se ...

environment, along with other equivalents:

LAPB Link Access Procedure, Balanced (LAPB) implements the data link layer as defined in the X.25 protocol suite. LAPB is a bit-oriented protocol derived from HDLC that ensures that frames are error free and in the correct sequence. LAPB is specified i ...

for the

X.25 X.25 is an ITU-T standard protocol suite for packet-switched data communication in wide area networks (WAN). It was originally defined by the International Telegraph and Telephone Consultative Committee (CCITT, now ITU-T) in a series of drafts ...

protocol stack,

LAPM Link Access Procedure for Modems (LAPM) is part of the V.42 error correction protocol for modems.ITU-T Recommendation V.42Error-correcting procedures for DCEs using asynchronous-to-synchronous conversion/ref> LAPM is an error control protocol defin ...

for the

V.42 The ITU-T V-Series Recommendations on Data communication over the telephone network specify the protocols that govern approved modem communication standards and interfaces. ''Note:'' the '' bis'' and ''ter'' suffixes are ITU-T standard designato ...

protocol, and LAPD for the

ISDN Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the digitalised circuits of the public switched telephone network. Wo ...

protocol stack. In Frame Relay

Local Management Interface Local Management Interface (LMI) is a term for some signaling standards used in networks, namely Frame Relay and Carrier Ethernet. Frame Relay LMI is a set of signalling standards between routers and Frame Relay switches. Communication takes pl ...

(LMI) messages are carried in a variant of LAPF frames. LAPF corresponds to the

OSI model The Open Systems Interconnection model (OSI model) is a conceptual model that 'provides a common basis for the coordination of SOstandards development for the purpose of systems interconnection'. In the OSI reference model, the communications ...

Data Link layer.

External links

Cisco Frame Relay documentation
Link access protocols Link protocols Frame Relay {{Compu-network-stub