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Cabling the Wide Area Network

here's a couple of things (well, okay, more than a couple, but we'll

start with these) that you need to know in order to connect your wide area
network (WAN). You've got to understand the WAN Physical layer imple-
mentation provided by Cisco, and you must be familiar with the various
types of WAN serial connectors. So mostly, that's what I'm going to talk
about in this section, but I'm also going to discuss the cabling requirements
for ISDN BRI connections.

Cisco serial connections support almost any type of WAN service. The

typical WAN connections are dedicated leased lines using High-Level Data
Link Control (HDLC), Point-to-Point Protocol (PPP), Integrated Services
Digital Network (ISDN), and Frame Relay. Typical speeds run at anywhere
from 2400bps to 1.544Mbps (T-1).

All of these WAN types are discussed in detail in Chapter 10.

HDLC, PPP, and Frame Relay can use the same Physical layer specifica-

tions, but ISDN has different pinouts and specifications at the Physical layer.

Serial Transmission

WAN serial connectors use serial transmission, which happens one bit at a
time, over a single channel. Parallel transmission can pass at least 8 bits at
a time, but all WANs use serial transmission.

Cisco routers use a proprietary 60-pin serial connector that you must buy

from Cisco or a provider of Cisco equipment. The type of connector you
have on the other end of the cable depends on your service provider or end-
device requirements. The different ends available are EIA/TIA-232, EIA/
TIA-449, V.35 (used to connect to a CSU/DSU), X.21 (used in X.25), and
EIA-530.

Serial links are described in frequency or cycles-per-second (hertz). The

amount of data that can be carried within these frequencies is called band-
width. Bandwidth is the amount of data in bits-per-second that the serial
channel can carry.

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