Link Access Procedure (LAP) Protocols Last Updated : 07 Apr, 2025 Comments Improve Suggest changes Like Article Like Report Link Access Procedure (LAP) is basically considered as an ITU family of Data Link Layer (DLL) protocols that are subsets of High-Level Data Link Control (HDLC). LAP is particularly derived from IBM’s Synchronous Data Link Control (SDLC). There are several LAP protocols. Each of these protocols is usually a subset of HDLC tailored for a particular purpose. Some of them are given below : These are explained as following below. Multilink Procedure (MLP) - MLP basically allows for Multilink Operations. It is an upper sublayer of the DLL that usually operates among Packet Layer and a multiplicity of SLP’s (Single Data Link Protocol) functions. It is generally an extension of LAPB that simply gives permission for multiple physical links along with providing better throughput. Link Access Procedure for Modems (LAPM) - LAPM has basically used in V.32 error-correcting modems and V.42 modems. Transmission among LAPM is synchronous even though transmission among computer and modem is asynchronous. With the help of bit-oriented synchronous techniques, LAPM generally transmits data in frames or packets. LAPM usually contains SREJ (Selective Reject) as an optional function that allows it to again send all of corrupted frames along with providing faster recovery from an error. Modem transmits or transfers data as frames even though all the attached or connected computer transfers data to LAPM modem as standard asynchronous input. To simply ensure data reliability i.e., data are reasonably complete and accurate or not, LAPM makes use of CRC (Cycle Redundancy Checking) and also of ARQ (Automatic Repeat Request). It is also been developed and established to apply some HDLC features to modems. It is also designed and created to do asynchronous-synchronous conversion, error detection and correction, and retransmission. Link Access Procedure for Frame Relay (LAPF) - LAPF basically provides data link for frame relay networks and is designed for use along with frame relay. It is easiest and simplest version of ISDN’s LAPD. It is also required or carrying data only and even there is no signaling at DLL for performing flow and error control. It is also a part of network’s communications protocol. LAPF simply ensures that whether frames are error-free and executed in correct sequence or not. It does not make use of C/R (Command/Response) bit, even though other higher-layer protocols that need application-specific do use this bit. Link Access Procedure for Half-Duplex (LAPX) - LAPX is basically used for ship-to-shore transmission. Comment More infoAdvertise with us Next Article Link Access Procedure (LAP) Protocols M madhurihammad Follow Improve Article Tags : Computer Networks Data Link Layer Similar Reads Link Access Protocol D-channel (LAPD) LAPD or Link Access Protocol on D channel is basically Layer 2 protocol usually required on ISDN D channel. It is being derived from Link Access Protocol Balanced (LAPB) protocol. It was specially designed and developed to simply satisfy the signaling requirements of ISDN basic access. The main obje 3 min read Link Access Procedure Balanced (LAPB) Frame Types Link Access Procedure, Balanced (LAPB) is protocol that is usually required for data link layer. It is version of High-Level Data Link Control (HDLC) in Asynchronous Balanced Mode (ABM). LAPB use of P/F bit is somewhere different from all of the other protocols. LAPB basically uses three types of da 4 min read Examples of Data Link Layer Protocols Data Link Layer protocols are generally responsible for ensuring and confirming that the bits and bytes received are identical to the bits and bytes being transferred. It is a set of specifications that are used for the implementation of the data link layer just above the physical layer of the Open 5 min read Multiple Access Protocols in Computer Network Multiple Access Protocols are methods used in computer networks to control how data is transmitted when multiple devices are trying to communicate over the same network. These protocols ensure that data packets are sent and received efficiently, without collisions or interference. They help manage t 9 min read Link Layer Discovery Protocol (LLDP) LLDP stands for Link Layer Discovery Protocol. It is an open IEEE-standard (802.1AB) Layer 2 protocol. LLDP is the open-source alternative for CDP (Cisco Discovery Protocol) which is also a device discovery protocol that runs over Layer 2 (the data link layer) only on Cisco-manufactured devices (rou 6 min read Like