Руководство Пользователя для Netopia 3220-h

How Your Cayman 3220-H Works

Cayman 3220-H User’s Guide

December 2000

several Network Control Protocols (NCPs), which establish how 
datagrams for a specific higher-level protocol using PPP as a data link 
should be encapsulated. Network control protocols establish and 
configure different network-layer protocols, such as TCP/IP.

PPP encapsulation provides for transmission of different 
network-layer protocols simultaneously over the same link. Once a 
PPP link is established, a PPP peer can negotiate the exchange of 
TCP/IP, IPX, or AppleTalk packets over standard telephone lines. 

When one PPP peer opens a link to another peer, the PPP link moves 
through several phases: 

Link establishment 

Link configuration 

Authentication 

Network configuration 

Link up 

Link termination 

Each phase is described separately below. 

The manner in which a PPP link is opened depends on whether the 
router's serial port is configured as a dial-in, dial-out, or dedicated 
interface: 

Dial-in -- If a port is configured as a dial-in interface, the router 
sends an initialization string to the modem when it is turned on 
to prepare it to accept calls. When the local modem receives an 
incoming call and negotiates the serial connection settings, the 
serial connection is established and the link peers begin 
negotiating the link configuration.