Point-to-Point Protocol (PPP)

Point-to-Point Protocol (PPP) is a data link protocol used to establish a direct connection between two nodes. It can provide connection authentication, transmission encryption (using ECP, RFC 1968), and compression. PPP is used over many types of physical networks, including serial cable, phone line, trunk line, cellular telephone, specialized radio links, and fiber optic links such as SONET. It's widely used for internet access and is particularly common in establishing connections between a computer and an Internet Service Provider (ISP) over a phone line with a modem.

Key features of PPP include:

  1. Encapsulation of Multi-protocol Traffic: PPP can encapsulate different network layer protocols (like IPv4, IPv6, IPX) for transmission over a point-to-point link.

  2. Link Control Protocol (LCP): It's used to establish, configure, and test the data link connection. LCP sets up and maintains the PPP connection.

  3. Network Control Protocols (NCPs): These are a set of protocols for establishing and configuring different network layer protocols.

  4. Authentication: PPP supports authentication protocols like PAP (Password Authentication Protocol) and CHAP (Challenge Handshake Authentication Protocol) to verify the identity of the connection.

  5. Error Detection: PPP includes error detection mechanisms to check if data is received correctly at the other end.

  6. Multiple Network Layer Protocols: PPP supports simultaneous operation of multiple network layer protocols.

  7. Quality and Compression: It can negotiate network layer compression and quality monitoring.

PPP is a fundamental element in many network connections and is integral to many broadband and dial-up internet access methods. It has been succeeded in some applications by more advanced protocols like PPP over Ethernet (PPPoE) and PPP over ATM (PPPoA).