What is Point-to-Point Protocol (PPP)?

PPP is a protocol that is generally used to provide similar functionality as SLIP. It is the best robust protocol that can transfer different types of packets also along with IP Packets. It can also be needed for dial-up and hired router-router lines. It generally supports the framing techniques to represent frames. 

It can transfer diagrams across a serial connection to transfer IP traffic over the point-to-point connection as an encapsulation protocol.

It can provide the responsibility and executive of IP addresses, asynchronous and bit-oriented synchronous encapsulation, network protocol multiplexing, link configuration, etc. It can support an extensible Link Control Protocol (LCP) along with Network Control Protocols (NCP).

PPP Components

The point-to-point protocol includes the following components for sending diagrams over serial point-to-point connections −

Encapsulating Diagrams

PPP operates the High-Level Data Link Control (HDLC) protocol to encapsulate diagrams over the point-to-point connection. The HDLC protocol represents the boundaries around the single PPP frames and supports a 16-bit checksum.

A PPP frame inserts a protocol field to the primary HDLC frame to recognize the type of packet transported by the frame to manage packets from protocols other than IP, including Novell's IPX or Appletalk.

Implementing LCP

An extensible link control LCP can start, construct and check the data-link connections. It is executed on top of HDLC to arrange preferences about the data link.

Implementing NCP

Classification of network control protocols (NCPs) can start and construct multiple network-layer protocols such as IP and Appletalk, routed across the data link. They are set up powerfully using an equivalent NCP.

Before transmitting IP diagrams across the link, both the host running PPP must negotiate the IP address used by each of them. The control protocols used for such negotiations is called Internet Protocol Control Protocol (IPCP).

PPP Frame

The PPP frame format is shown in the figure below and includes the following −

  • Flag: It includes a single byte that denotes the starting or end of a frame.

  • Address: Address includes a single byte that contains the binary sequence. PPP does not allow single station addresses.

  • Control: It creates an individual byte that includes the binary sequence, which calls for user information communication. It is a connectionless link function equivalent to that of Logical Link Control (LLC).

  • Protocol: It includes two bytes that recognize the protocol encapsulated in the frame's information field.

  • Data: Data can range from zero or more bytes, including the datagram for the protocol defined in the protocol field. The default highest duration of the information field is 1,500 bytes.

  • Frame Check Sequence (FCS): It accepts 2 bytes. In this term, it can also use 4-byte FCS for upgraded error detection but with previous agreement.