R0106-HP MSR Router Series Layer 2 - WAN Configuration Guide(V7)

Configuring PPP and MP

In this chapter, "MSR2000" refers to MSR2003. "MSR3000" collectively refers to MSR3012, MSR3024,

MSR3044, MSR3064. "MSR4000" collectively refers to MSR4060 and MSR4080.

PPP overview

Point-to-Point Protocol (PPP) is a point-to-point link layer protocol. It provides user authentication, supports

synchronous/asynchronous communication, and allows for easy extension.

PPP includes the following protocols:

• 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—Authenticate users. Protocols include 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 1 shows the PPP link establishment process.

Figure 1 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), Maximum-Receive-Unit

(MRU), Magic-Number, 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.)

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 client fails to pass the authentication,

LCP reports a Fail event and enters the Link Termination phase, where the link is torn down and LCP

goes down. If the client passes the authentication, LCP reports a Success event.

4. If a network layer protocol is configured, the PPP link enters the Network-Layer Protocol phase for

NCP negotiation, such as IPCP negotiation. If the NCP negotiation succeeds, the link goes up and

Dead Establish

Authenticate

Opened

Terminate Network

Down

Fail Fail

Success

/None

Closing