Wide Area Networks
505
Demarcation
The
demarc
is the last responsibility of the service pro-
vider, usually an RJ-45 jack located close to the CPE. The CPE at this
point would be a CSU/DSU or ISDN interface that plugs into the demarc.
Local loop
The
local loop
connects the demarc to the closest switching
office, called a central office.
Central office (CO)
This point connects the customers to the provider's
switching network. A
central office (CO)
is sometimes referred to as a
point of presence (POP)
.
Toll network
These are trunk lines inside a WAN provider's network.
The toll network is a collection of switches and facilities.
It is important to familiarize yourself with these terms, as they are crucial
to understanding WAN technologies.
WAN Connection Types
Figure 10.1 shows the different WAN connection types that can be used to
connect your LANs together over a DCE network.
F I G U R E 1 0 . 1
WAN connection types
Dedicated
Circuit-switched
Packet-switched
Synchronous serial
Asynchronous serial, ISDN
Synchronous serial
Telephone
company
Service
provider
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