👉 PPP (Point-to-Point Protocol) Explained
PPP (Point-to-Point Protocol) is a widely used data link layer protocol designed to enable direct communication between two network nodes. Standardized by the IETF, PPP provides a reliable method to transport multiple types of network layer packets—such as IPv4, IPv6, and legacy protocols—over point-to-point links, including serial cables, fiber, DSL, or dedicated leased lines.
Unlike Ethernet, which works in multi-access environments, PPP is optimized for direct node-to-node communication, making it a foundational protocol for WANs and early Internet access technologies.
👉 Core Functions of PPP
PPP delivers three essential capabilities that make it a preferred protocol for service providers and enterprise WANs:
Encapsulation of Network Layer Packets
PPP encapsulates different network protocols into a uniform frame format.
It ensures compatibility across heterogeneous systems and supports multiple protocols simultaneously.
Link Establishment and Configuration
PPP uses the Link Control Protocol (LCP) to establish, configure, and test the link between two devices.
Parameters such as maximum frame size, compression options, and error detection methods are negotiated dynamically.
Authentication
PPP supports optional authentication using PAP (Password Authentication Protocol) and CHAP (Challenge Handshake Authentication Protocol).
This ensures that only authorized users or devices gain access to the network.
Support for Multiple Protocols
Through Network Control Protocols (NCPs) such as IPCP (for IPv4) and IPV6CP (for IPv6), PPP can handle various upper-layer protocols efficiently.
👉 PPP Frame Structure
PPP frames are based on the HDLC format and include:
Flag (0x7E): Indicates the start and end of the frame.
Address (0xFF): Broadcast address, fixed in PPP.
Control (0x03): Denotes unnumbered information.
Protocol: Identifies the encapsulated payload (e.g., IPv4, IPv6).
Payload: The actual data packet from the network layer.
FCS (Frame Check Sequence): Provides error detection using CRC.
This structure ensures robust encapsulation and error detection, even on noisy transmission media.
👉 Applications of PPP
PPP has been applied in several key networking scenarios:
WAN Connections
PPP is widely used in point-to-point leased lines and Packet over SONET/SDH (POS) connections between routers.
Broadband Internet Access
Technologies such as PPPoE (PPP over Ethernet) and PPPoA (PPP over ATM) were foundational in DSL broadband deployments, allowing ISPs to authenticate and manage users.
Virtual Private Networks (VPNs)
Early VPN solutions leveraged PPP for protocol encapsulation and user authentication, forming the basis for PPTP and related tunneling protocols.
👉 Why PPP Still Matters
Although Ethernet and MPLS dominate modern networks, PPP continues to play a role in legacy WAN systems and as a building block in protocol encapsulation methods. Its design influenced many subsequent standards and is still referenced in broadband and carrier-grade infrastructure.
For businesses and engineers dealing with WAN links, understanding PPP remains critical for grasping how authentication, encapsulation, and protocol negotiation evolved in networking.
