Link Control Protocol
Encyclopedia
In computing
, the Link Control Protocol (LCP) forms part of the Point-to-Point Protocol
. In setting up PPP communications, both the sending and receiving devices send out LCP packets to determine the standards of the ensuing data transmission. LCP is logically a Transport Layer
protocol according to the OSI model
, however it occurs as part of the Data link layer
in terms of the actual implemented Network stack.
The LCP protocol
:
Devices cannot use PPP to transmit data over a network until the LCP packet determines the acceptability of the link, but LCP packets are embedded into PPP packets and therefore a basic PPP connection has to be established before LCP can reconfigure it.
The LCP over PPP packets have control code 0xC021 and their info field contains the LCP packet, which has four fields (Code, ID, Length and Data).
LCP was created to overcome the noisy and unreliable physical lines of the time (e.g. phone lines on dial up modems), in a way which didn't lock the PPP protocol into specific proprietary vendor protocols and physical transmission media.
Computing
Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...
, the Link Control Protocol (LCP) forms part of the Point-to-Point Protocol
Point-to-Point Protocol
In networking, the Point-to-Point Protocol is a data link protocol commonly used in establishing a direct connection between two networking nodes...
. In setting up PPP communications, both the sending and receiving devices send out LCP packets to determine the standards of the ensuing data transmission. LCP is logically a Transport Layer
Transport layer
In computer networking, the transport layer or layer 4 provides end-to-end communication services for applications within a layered architecture of network components and protocols...
protocol according to the OSI model
OSI model
The Open Systems Interconnection model is a product of the Open Systems Interconnection effort at the International Organization for Standardization. It is a prescription of characterizing and standardizing the functions of a communications system in terms of abstraction layers. Similar...
, however it occurs as part of the Data link layer
Data link layer
The data link layer is layer 2 of the seven-layer OSI model of computer networking. It corresponds to, or is part of the link layer of the TCP/IP reference model....
in terms of the actual implemented Network stack.
The LCP 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...
:
- checks the identity of the linked device and either accepts or rejects the peerPeer-to-peerPeer-to-peer computing or networking is a distributed application architecture that partitions tasks or workloads among peers. Peers are equally privileged, equipotent participants in the application...
device - determines the acceptable packet size for transmission
- searches for errors in configuration
- can terminate the link if requirements exceed the parameters
Devices cannot use PPP to transmit data over a network until the LCP packet determines the acceptability of the link, but LCP packets are embedded into PPP packets and therefore a basic PPP connection has to be established before LCP can reconfigure it.
The LCP over PPP packets have control code 0xC021 and their info field contains the LCP packet, which has four fields (Code, ID, Length and Data).
- Code: Operation requested: configure link, terminate link, ... and acknowledge and deny codes.
- Data: Parameters for the operation
LCP was created to overcome the noisy and unreliable physical lines of the time (e.g. phone lines on dial up modems), in a way which didn't lock the PPP protocol into specific proprietary vendor protocols and physical transmission media.