For Dummies CCNA Certification All-In-One 978-0-470-48962-8 User Manual
Product codes
978-0-470-48962-8
Book VII
Chapter 1
Wide-Area
Networking Basics
809
Introducing WANs
These hardware devices are used to establish the WAN communications
link and are responsible for translating frames between the local LAN and
the ISP or phone company. DCE units are located between the DTE device
and the transmission link or circuit, such as a dedicated leased line. The
transmission link is the WAN path the data travels to reach other networks.
the ISP or phone company. DCE units are located between the DTE device
and the transmission link or circuit, such as a dedicated leased line. The
transmission link is the WAN path the data travels to reach other networks.
DCE devices also control the clock rate for DTE devices. DCEs allow the
timing for all network devices to remain synchronized by maintaining
an accurate bit rate. This ensures that all network data is time synchro-
nized and readable between DCE and DTE devices.
an accurate bit rate. This ensures that all network data is time synchro-
nized and readable between DCE and DTE devices.
WAN connectivity would not be possible without the services of both DCE and
DTE devices. DTEs are known as user-side devices — usually routers or com-
puters — that interconnect packet-switching LANs, converting user data into
signals that can be interpreted by DCE devices. Customer devices that con-
nect to the telephone company’s (telco’s) equipment are known as customer
premises equipment (CPE). The site location where the customer equipment
(DTE) and telephone equipment (DCE) meet is called the demarcation point
(demarc). An example of the DCE and DTE arrangement is shown in Figure 1-2.
DTE devices. DTEs are known as user-side devices — usually routers or com-
puters — that interconnect packet-switching LANs, converting user data into
signals that can be interpreted by DCE devices. Customer devices that con-
nect to the telephone company’s (telco’s) equipment are known as customer
premises equipment (CPE). The site location where the customer equipment
(DTE) and telephone equipment (DCE) meet is called the demarcation point
(demarc). An example of the DCE and DTE arrangement is shown in Figure 1-2.
Figure 1-2:
DTE and
DCE
devices.
DTE and
DCE
devices.
Router
(DTE)
Modem
(DCE)
Computer Terminal
(DTE)
Modem
(DCE)
Transmission
Medium/Telecom
Switch
Cisco serial interfaces
All wide-area networks use serial interfaces as a means of transmission.
Serial transmission allows traffic to flow 1 bit at a time over a single channel
or link. A few questions must be raised when selecting a serial interface:
Serial transmission allows traffic to flow 1 bit at a time over a single channel
or link. A few questions must be raised when selecting a serial interface:
✦
Will the interface be used by a DTE or a DCE device?
✦
Which signaling standard does the serial interface require?
✦
What type of connector is required?
A DTE device typically has a male connector with pins.
A DCE device typically has a female connector with holes.
The two types of proprietary Cisco WAN connectors are as follows:
✦
Proprietary 60-pin serial connection: A WAN connection using a 60-pin
serial interface developed by Cisco Systems. The opposite end of the
serial interface developed by Cisco Systems. The opposite end of the
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