1.Applying PPP To WAN

PPP is the most widely used and most popular WAN protocol because of the following features:

- Control of data link setup
- Provides for dynamic assignment of IP addresses
- Network protocol multiplexing
- Link configuration and link quality testing
- Error detection
- Negotiation options for capabilities such as network layer address and data compression negotiations

Applying PPP to the Washington School District WAN will provide point-to-point serial lines with an encapsulation protocol to communicate with each other.

PPP will establish, configure, and test the data link connections in the wide area network. The Network Control Protocol establishes and configures different network layer protocols such as IP and IPX.

With PPP lower level functions, synchronous and asynchronous media can be used for connectivity using ISDN and basic dialup connections. Higher level protocols can encapsulate or support network layer protocols with Network Control Protocols. These higher level protocols include Internet Protocol Control Protocol and Internetwork Packet Exchange Protocol.


2. Implementing PPP On A Router:

WAN Core Routers:

< > indicate where relevant information should be inputted by the administrator.

username <name> password <secret password>

The username should be the hostname of every remote router connecting to this router. The pasword should be the same for both routers.

interface serial <slot>/<port>
encapsulation ppp
ppp authentication chap

CHAP offers features such as periodic verification and three-way handshakes to improve security. CHAP does not send passwords across links in clear text, it encrypts them.

ppp chap hostname <hostname> 
ppp chap password <secret password>

The PPP chap hostname and password is the username and password remote routers expect from this router when authenticating. If more than one router can be connected to for authentication, this command can be used on all routers to make the user think they are connecting to the same router. This hostname and password will be setup as the username and password on remote routers.


District Site Routers:

< > indicate where relevant information should be inputted by the administrator.

username <hostname of remote router> password <secret password>

The username here should match the ppp chap hostname inputted in the WAN router. Passwords between the two routers must be the same secret password.

interface serial <slot>/<port>
encapsulation ppp
ppp authentication chap

See Router Configuration Scripts For Router Configuration Changes

3. Benefits Of PPP Over Other Layer 2 WAN Protocols

PPP offers several benefits to its users over other Layer 2 WAN protocols such as HDLC and SLIP.

PPP offers control of data-link setup, link quality determination, network layer protocol configuration negotiation, and link termination. PPP also offers network protocol multiplexing which allows for multiple routing protocols to be used over the same lines. Dynamic assignment of IP addresses is an advantage PPP has over SLIP. PPP can provide connections over synchronous and asynchronous lines. PPP has error correction and data compression.
HDLC only works on point-point lines and has a 2 byte proprietary field in its header that can make it incompatible with other vendors equipment.