R3303-HP HSR6800 Routers Layer 2 - WAN Configuration Guide

Configuring PPP and MP

Overview

PPP

Point-to-Point Protocol (PPP) is a link layer protocol carrying network layer packets over point-to-point links.

It gains popularity because it provides user authentication, supports synchronous/asynchronous

communication, and allows for easy extension.

PPP contains a set of protocols, including:

• Link control protocol (LCP)—Establishes, tears down, and monitors data links.

• Network control protocol (NCP)—Negotiates the packet format and type for data links.

• Authentication protocols—Provides network security, consisting of Password Authentication

Protocol (PAP), Challenge Handshake Authentication Protocol (CHAP), Microsoft CHAP

(MS-CHAP), and Microsoft CHAP Version 2 (MS-CHAP-V2).

PPP link establishment process

Figure 10 shows the PPP link establishment process.

Figure 10 PPP link establishment process

1. Initially, PPP is in Link Dead phase. After the physical layer goes up, PPP enters the Link

Establishment phase (Establish).

2. In the Link Establishment phase, the LCP negotiation is performed. The LCP configuration options

include Authentication-Protocol, Async-Control-Character-Map (ACCM),

Protocol-Field-Compression (PFC), Address-and-Control-Field-Compression (ACFC), and MP. If the

negotiation fails, LCP reports a Fail event, and PPP returns to the Dead phase. If the negotiation

succeeds, LCP enters the Opened state and reports an Up event, indicating that the underlying

layer link has been established. (At this time, the PPP link is not established for the network layer,

and network layer packets cannot be transmitted over the link.)

The router does not support ACCM, PFC, or ACFC negotiation.

3. If authentication is configured, the PPP link enters the Authentication phase, where PAP, CHAP,

MS-CHAP, or MS-CHAP-V2 authentication is performed. If the supplicant fails to pass the

authentication, the link reports a Fail event and enters the Link Termination phase, where the link

is torn down and LCP goes down. If the supplicant passes the authentication, a Success event is

reported.

Dead Establish

Authenticate

Opened

Terminate Network

Down

Fail Fail

Success

/None

Closing