Updated April 4, 2023
Introduction to Data Link Layer
Data link layer is the second layer of the OSI model of computer networking. This layer transforms data between nodes on the network segment over across the physical layer. It 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. Data link layer protocol is generally responsible to simply ensure and confirm that the bits and bytes that are received are identical to bits and bytes being transferred. SDLC, HDLC, SLIP, PPP, LCP, LAP, and NCP are some of the data link layer protocols.
List of Data Link Layer Protocols
Below is the list of Data link layer protocols.
SDLC:
SDLC stands for synchronous data link control protocol, is a communication protocol of a computer. It is usually used to carry system network architecture traffic. synchronous data link protocol connects all the remote devices to the mainframe computer at the Central location. This connection is done in two formats, point to point format i.e. one to one connection, and point to multipoint format, i.e. one to many connections. SDLC support one to many connections even in case of error detection or error recovery. SDLC ensures that all the received data units are correct and flow is right from one network point to the next network point.
HDLC:
HDLC stands for High-level data link control protocol, is a bit-orientated code transparent synchronous protocol developed by ISO (International organization for standardization) in1979. It provides both connection-orientated and connectionless services. HDLC protocol contains various wide-area protocols. It is based on the SDLC protocol that supports both point-to-point and multipoint communication. HDLC frames are transferred over synchronous or asynchronous serial communication links. HDLC uses various modes such as normal response mode, asynchronous response mode, asynchronous balanced mode. Normal response mode is used to share the secondary to primary link without contention. asynchronous response mode is used for full-duplex links. asynchronous balanced mode, support combined terminal which can act as both primary and secondary.
SLIP:
SLIP stands for Serial line interface protocol which is used to add framing byte at the end of the IP Packet. SLIP is a data link layer protocol That transforms the IP packets among ISP (Internet Service Providers) and home user over dial-up links. SLIp is designed to work with ports and router connections. SLIP does not provide error detection, being reliant on upper-layer protocols for this. Therefore, SLIP on its own is not satisfactory over an error-prone dial-up connection.
PPP:
PPP stands for Point to point protocol. PPP is a data link layer protocol that provides the same services as the Serial line interface protocol. It is a robust protocol that transfers the other types of pockets also with the IP packets. It provides two protocols – LCP and NCP, that we will discuss in the next section. Point to point protocol uses framing methods that describe the frames. Point to point protocol is also called character orientated protocol which is used to detect errors. PPC provides Connection authentication, data compression, encryption, and transmission. It is used over various networks such as phone lines, cellular telephones, serial cables, trunk lines, ISDNs, Specialized radio links, etc.
LCP:
LCP stands for Link control protocol, is a part of point-to-point control protocol. LCP packets determine the standards of data transmission. LCP protocol is used to determine the identity of the linked devices, if the device is correct it accepts it otherwise it rejects the device. It also determines whether the size of the packet is accepted or not. If requirements exceed the parameters, then the link control protocol terminates that link.
LAP:
LAP stands for Link access procedure is a data link layer protocol that is used for framing and transfer the data across point-to-point links. There are three types of Link access procedure – LAPB ( Link Access procedure balanced), LAPF ( Link Access Procedure Frame-Mode Bearer Services), and LAPD (Link Access Procedure D-Channel. LAP was originally derived from HDLC (High-Level Data Link Control), but was later updated and renamed LAPB (LAP Balanced).
NCP:
NCP stands for Network control protocol, is a part of the point-to-point protocol. The network control protocol is used to negotiate the parameter and facilities for the network layer. For every higher-layer protocol supported by PPP, one NCP is there. IPCP ( Internet Protocol control protocol), DNCP (DECnet Phase IV Control Protocol), OSINLCP (OSI Network Layer Control Protocol), IPXCP (Internetwork Packet Exchange Control Protocol), NBFCP (NetBIOS Frames Control Protocol), IPV6CP (IPv6 Control Protocol) are some of the NCPs.
Conclusion
Here, in this article, we have discussed the data link layer protocols SDLC, HDLC, SLIP, PPP, LCP, LAP, and NCP. We hope you enjoyed the article.
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