WAN Fundamentals

Question 1

Leased line service delivers….

Answer 1

bits in both directions, at a predetermined speed, using full-duplex logic

Question 2

Telco …

Answer 2

installs a large network of cables and specialized switching devices to create its own computer network

Question 3

To create a leased line…

Answer 3

a physical path must exist between the routers on the ends of the link; usually a large and complex network that gives the appearance of a cable between two routers

Question 4

Telcos put their equipment in….

Answer 4

Central offices (COs) where they connect cables from COs to buildings where they expect to sell their services

Question 5

Customer premises equipment includes:

Answer 5

router, serial interface card (within router?), CSU/DSU

Question 6

CSU/DSU typically provides

Answer 6

the clock rate

Question 7

The serial cables normally used between a router and external CSU/DSU are called

Answer 7

Data Terminal Equipment (DTE) cables; male cable

Question 8

DCE cables are….

Answer 8

cables that are female and have the equivalent task of an Ethernet crossover cable

Question 9

A leased line provides a ________ service

Answer 9

Layer 1

Question 10

Two most popular DLL protocols for leased lines

Answer 10

High Level Data Link Control (HDLC) and Point to Point Protocol (PPP)
SN: Organizations create Layer 2 protocols for WAN links

Question 11

Ethernet as a WAN technology basics

Answer 11

The customer connects to an Ethernet link using a router interface.
The fiber leaves the customer building and conncts to some nearby Service Provider location called a point of presence (POP) by using an Ethernet switch

Question 12

Ethernet over MPLS (EoMPLS) provides:

Answer 12

A point-to-point connection between two customer devices
Behavior as if a fiber Ethernet link existed between the two devices
Simply two routers with a single Ethernet link between the two routers; uses Ethernet header and trailer over the WAN link

Question 13

Main idea of WANs

Answer 13

give IP routers a way to forward IP packets from a LAN at one site, over the WAN, and to another LAN at another site.

Question 14

What all three Internet access technologies have in common:

Answer 14

they use a pair of routers: one at the customer side of the WAN link and one at the ISP side.

Question 15

Digital Subscriber LIne (DSL)

Answer 15

Creates a relatively short (miles long, not tens of miles) high speed WAN link between a telco customer and an ISP; utilizes the same single-pair telephone line used for a typical home phone line

Question 16

In order to have DSL service:

Answer 16

You need DSL capable devices such as a DSL modem and the telco has to add DSL equipment at the CO; telco uses a DSL Access Multiplexer (DSLAM) to differentiate data between voice signals and Internet connections via a router

Question 17

Cable Internet

Answer 17

utilizes cable TV cable (CATV) to send data; similar to DSL; both send data faster downstream than upstream; telephone line is replaced with coaxial cable from CATV company and uses a cable modem instead of a DSL