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Chapter 10

Wide Area Networking Protocols

The following list explains the WAN connection types:

Leased lines

Typically referred to as a

point-to-point connection

dedicated connection; a

leased line

is a pre-established WAN communi-

cations path from the CPE, through the DCE switch, to the CPE of the
remote site, allowing DTE networks to communicate at any time with no
setup procedures before transmitting data. It uses synchronous serial lines
up to 45Mbps.

Circuit switching

Sets up a line like a phone call. No data can transfer

before the end-to-end connection is established;

circuit switching

uses

dial-up modems and ISDN. It is used for low-bandwidth data transfers.

Packet switching

WAN switching method that allows you to share band-

width with other companies to save money. Think of packet switching
networks as a party line. As long as you are not constantly transmitting
data and are instead using bursty data transfers, packet switching can save
you a lot of money. However, if you have constant data transfers, you will
need to get a leased line. Frame Relay and X.25 are packet-switching tech-
nologies. Speeds can range from 56Kbps to 2.048Mbps.

WAN Support

In this section, we will define the most prominent WAN protocols used
today. These are Frame Relay, ISDN, LAPB, HDLC, and PPP. The rest of the
chapter will be dedicated to explaining in depth how WAN protocols work
and how to configure them with Cisco routers.

Frame Relay

A packet-switched technology that emerged in the early

1990s,

Frame Relay

is a Data Link and Physical layer specification that

provides high performance. Frame Relay assumes that the facilities used
are less error prone than when X.25 was used and that they transmit data
with less overhead. Frame Relay is more cost-effective than point-to-point
links and can typically run at speeds of 64Kbps to 1.544Mbps. Frame
Relay provides features for dynamic bandwidth allocation and congestion
control.

ISDN

Integrated Services Digital Network (ISDN)

is a set of digital

services that transmit voice and data over existing phone lines. ISDN
can offer a cost-effective solution for remote users who need a higher-
speed connection than analog dial-up links offer. ISDN is also a good
choice as a backup link for other types of links such as Frame Relay or
a T-1 connection.

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