Fundamentals Of Wans

Front 1

WAN data link layer protocols:
1- ....
2- ....
3- ....

Back 1

1- High-Level Data Link Control (HDLC).
2- Point-to-Point Protocol (PPP) .
3- Frame Relay

Front 2

WAN standards and protocols define ?

Back 2

WAN standards and protocols define how to
network between devices that are relatively far apart—in some cases, even thousands of
miles apart—hence the term wide-area in the acronym WAN.

Front 3

LANs and WANs implement which OSI layers?

Back 3

LANs and WANs both implement the same OSI Layer 1 and Layer 2 functions, but with
different mechanisms and details

Front 4

You typically use ......... cables between end-user devices and the switches

Back 4

You typically use straightthrough
Ethernet cables between end-user devices and the switches

Front 5

For the trunk links
between the switches, you use .........

Back 5

For the trunk links
between the switches, you use crossover cables

Front 6

demarcation point, to refer to .....

Back 6

demarcation point, to refer to the point at which the telco’s responsibility is on one side and
the customer’s responsibility is on the other.

Front 7

The term customer premises equipment (CPE) refers to ...
....

Back 7

The term customer premises equipment (CPE) refers to devices that are at the customer site,
from the telco’s perspective.
For instance, both the CSU/DSU and the router are CPE
devices in this case.

Front 8

standardized WAN connectors

Back 8

EIA/TIA-232
EIA/TIA-449
V.35 X.21
EIA-530

Front 9

The cable between the CSU/DSU and the telco CO (central office) typically uses an ....... connector to
connect to the CSU/DSU;

Back 9

RJ-48

Front 10

Every WAN circuit ordered from a service provider runs at one of many possible predefined
speeds. This speed is often referred to as ......

Back 10

the clock rate, bandwidth, or link speed.

the enterprise network
engineer must configure the CSU/DSU on each end of the link to match the defined speed.

Front 11

Synchronization occurs between the two CSU/DSUs on a leased line by having .......

Back 11

one CSU/DSU (the slave) adjust its clock to match the clock rate of the other CSU/DSU (the master).

Front 12

In practice, the clocking concept includes a hierarchy of different clock sources. The telco
provides clocking information to the CSU/DSUs based on the transitions in the electrical
signal on the circuit. The two CSU/DSUs then adjust their speeds to match the clocking
signals from the telco. The CSU/DSUs each supply clocking signals to the routers so that
the routers simply react, sending and receiving data at the correct rate. So, from the routers’
perspectives, the ........ is considered to be clocking the link.

Back 12

CSU/DSU

Front 13

The device that provides
clocking, typically the CSU/DSU, is considered to be the ..........

Back 13

data communications equipment
(DCE)

Front 14

The device receiving clocking, typically the router, is referred to as ............

Back 14

data terminal equipment (DTE).

Front 15

when purchasing serial cables from Cisco, you can pick either a .... or a ... cable

Back 15

DTE or DCE

Front 16

What is the bit rate of WAN speed standard DS0 ?

Back 16

64 kbps

Front 17

What is the bit rate of WAN speed standard DS1 (T1) ?

Back 17

1.544 Mbps (24 DS0s, plus 8 kbps overhead)

Front 18

What is the bit rate of WAN speed standard DS3 (T3) ?

Back 18

44.736 Mbps (28 DS1s, plus management overhead)

Front 19

What is the bit rate of WAN speed standard E1 ?

Back 19

2.048 Mbps (32 DS0s)

Front 20

What is the bit rate of WAN speed standard E3 ?

Back 20

34.064 Mbps (16 E1s, plus management overhead)

Front 21

What is the bit rate of WAN speed standard J1 (Y1) ?

Back 21

2.048 Mbps (32 DS0s; Japanese standard)

Front 22

The two most popular data link layer protocols used on pointto-
point links are (1.....) and (2....).

Back 22

(1)High-Level Data Link Control (HDLC)
(2)Point-to-Point Protocol
(PPP)

Front 23

What is the standard HDLC header ?

Back 23

[Flag 1 | Address 1 | Control 1 | Data variable| FCS 4]

Front 24

What is Proprietary Cisco HDLC ?

Back 24

[Flag 1 | Address 1 | Control 1 |Type 2| Data variable| FCS 4]

(Adds Type field)

Front 25

using the HDLC , if error occurs ...
a - the error recovery performed
b - the device receiving the frame disgards the frams

Back 25

b - the device receiving the frame disgards the frams

Front 26

The Cisco implementation of HDLC includes a ..... field that identifies the type of packet inside the frame

Back 26

Protocol Type field

Front 27

The original HDLC standards did not include a Protocol Type field, , Cisco made its version of HDLC proprietary. So, the Cisco implementation of HDLC (will not work)(will work) when connecting a Cisco router to another vendor’s router.

Back 27

(will not work)

Front 28

PPP stand for

Back 28

Point-to-Point Protocol (PPP).

Front 29

when connecting a Cisco router to another vendor’s router over
a point-to-point serial link,

a - PPP is the data link layer protocol of choice.
b- standard HDLC data link layer protocol of choice.

Back 29

a - PPP is the data link layer protocol of choice.

because the Protocol Type field is part of the
standard for PPP, any vendor that conforms to the PPP standard can communicate with
other vendor products

Front 30

what is Clock source ?

Back 30

The device to which the other devices on the link adjust their speed when using synchronous links.

Front 31

what is CSU/DSU ?

Back 31

Channel service unit/data service unit. Used on digital links as an interface to the
telephone company in the United States.

Routers typically use a short cable from a
serial interface to a CSU/DSU, which is attached to the line from the telco with a
similar configuration at the other router on the other end of the link.

Front 32

Telco stand for what ?

Back 32

Telephone company.

Front 33

What is the Four-wire
circuit ?

Back 33

A line from the telco with four wires
, composed of two twisted-pair wires. Each
pair is used to send in one direction, so a four-wire circuit allows full-duplex
communication.

Front 34

Type of WANs ?

Back 34

1- point-to-point leased line
following terms
may be used to refer to a point-to-point leased line (leased line, leased circuit, link, serial link, serial line, point-to-point link, circuit)

2-point-to-multipoint (packet-switching services.)
a- Frame Relay
b- AsynchronousTransfer Mode (ATM)
c-VPN (Virtual Private Network)

Front 35

leased line is installed between each router and a nearby Frame Relay switch; these links are called ....

Back 35

access links

Front 36

Each Frame Relay header holds an address field called a .....

Back 36

datalink connection identifier (DLCI).

The WAN switch forwards the frame based on the DLCI,

Front 37

The Frame Relay header and trailer are defined by a protocol called .......

Back 37

Link Access
Procedure – Frame (LAPF).

Front 38

With Frame Relay, the Frame Relay switches
are called DCE/DTE, and the customer equipment—routers, in this case—are called DCE/DTE.

Back 38

the Frame Relay switches
are called DCE

and the customer equipment—routers, in this case—are called DTE.

DCE refers to the device providing the service, and the term DTE refers to the device
needing the frame-switching service

Front 39

In Frame Relay , The logical path that a frame travels between each pair of routers is called a .....

Back 39

Frame Relay
VC (Virtual Circuit.

Front 40

CIR Stand forwhat ?

Back 40

committed information rate (CIR).

Front 41

Each VC has a ......., which is a guarantee by the provider that a particular VC gets at least that much bandwidth.

Back 41

(CIR)committed information rate