Link Control Protocol

The protocol LCP ( Link Control Protocol) is a term used in computer science.

This protocol is used to configure a data connection with a PPP (Point- to-Point Protocol ) connection, build and test.

  • 3.1 Maximum Receive Unit (MRU )
  • 3.2 authentication protocol
  • 3.3 Quality Protocol

Preparation of a PPP connection

PPP, the communication over a point-to -point connection in four phases forth:

LCP packet formats

LCP header

Code Description Reference

The code is 8 bits long. Specifies the function to be executed.

The identifier field is 8 bits long. It is used to control the requests and responses.

The length field is 16 bits long. Size of the packet including the header.

The data have a variable length. Zero or more bytes of data is described by the length field. This field contains one or more options.

LCP Configuration Options

The option field is 8 bits long.

The length field is 8 bits long. The length in bytes of the options, including the two fields "Length" and "Option". These are accordingly the length of the option plus 2 bytes. example:

The data have a variable length. Zero or more bytes for specific options.

LCP Configuration Options

Maximum Receive Unit (MRU )

This option informs the communication partner, what is the maximum packet size can be received. The default value according to RFC 1661 is 1500 bytes. The transmitter may also send smaller packets.

Authentication protocol

Authentication protocols in RFC 1661 are

  • Password_Authentication_Protocol PAP
  • Challenge Handshake Authentication Protocol CHAP

Quality Protocol

About this configuration option, a protocol for the exchange of link quality data to be negotiated.

Point-to-Point Protocol Network Control Protocol Password Authentication Protocol
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