Chapter 8 - Wide Area Networks

Question 1

What is a Wide Area Network (WAN)?

Answer 1

• Networks and hosts are spread out over large distances (country or continent wide).
• Interconnect several MANs
• Typically owned by network providers
• Inter-processer distance 1000+ km

Question 2

Describe the link type that the WAN usually uses

Answer 2

• Typically fiber
• Possibly microwave
• Link speed of 1 to 40 Gb/s (Ethernet); 622 Mb/s to 39.8 Gb/s (SONET); 54 – 170 Mb/s (Microwave)

Question 3

Draw the WAN topology

Answer 3

See Slide 2 of IT Infrastructure Diagrams Keynote

Question 4

Draw the WAN services view diagram

Answer 4

See Slide 3 of IT Infrastructure Diagrams Keynote

Question 5

Name two common carrier services regulatory bodies.

Answer 5

Canadian Radio-Television and Telecommunications Commission (CRTC)
Federal Communications Commission (FCC)

Question 6

What are the four main WAN circuit types?

Answer 6

• Circuit switched
• Dedicated circuit
• Packet switched
• Virtual Private Network

Question 7

Describe the circuit switched network

Answer 7

• Uses the Public Switched Telephone Network
• (according to the textbook it uses a cloud architecture)
• Oldest WAN service
• Dial up

Question 8

What are the two types of circuit switched networks?

Answer 8

Dial-up:

• Plain Old Telephone Service (POTS)
• Integrated Services Digital Network (ISDN)

Question 9

What are the two main problems with circuit switched networks?

Answer 9

• Each time you want to transfer data you have to create a new connection
• The data rates are low

Question 10

Describe dedicated circuit networks (also called leased line or private line service)

Answer 10

• Creates a point-to-point link between two customer locations.
• Ends of link are terminated by a Customer Premises Equipment (CPE)
• Typically billed a flat fee per month for unlimited use.

Question 11

Draw the textbook diagram of a dedicated circuit network topology

Answer 11

See Slide 4 of the IT Infrastructure Diagrams Keynote

Question 12

What are the three basic dedicated circuit network architectures? Draw them.

Answer 12

• Ring (slide 7 of diagrams keynote): Linked in a ring topology. Can be rerouted around a failed link.
• Star (slide 8 of diagrams keynote): customer cites are linked through a central router (can become a bottleneck). Link failure only affects one location.
• Partial/Full Mesh (slide 9 of diagrams keynote): each customer site has multiple links to other customer sites. More expensive.

Question 13

What are the two main services of dedicated circuit networks?

Answer 13

• T-Carrier
• SONET
• both use time division multiplexing

Question 14

What type of network is likely going to replace SONET?

Answer 14

Optical Transport Network (OTN)

Question 15

Draw the basic architecture of a Packet Switched Network

Answer 15

See slide 12 of the IT Infrastructure Diagrams slide deck

Question 16

What are the main differences between Circuit Switched Networks and Packet Switch Networks?

Answer 16

Circuit Switched: physical circuit connects two endpoints of customer premises equipment and is not shared by any other devices.
Packet Switched: Multiple data streams from different connections share the same physical connection.

Question 17

What are the four types of packet switched services

Answer 17

• Asynchronous Transfer Mode (ATM) (legacy)
• Frame Relay (legacy)
• Multiprotocol Label Switching (IP/MPLS)
• Ethernet Services

Question 18

Name some advantages of ethernet services

Answer 18

• Ethernet technology is ubiquitous - it works with existing infrastructure.
• It represents a simplified network design and management

Question 19

Name three types of ethernet services

Answer 19

• Metro internet
• Wide Area Ethernet (WAE)
• Virtual private LAN Service

Question 20

Packet switched network: Describe Multi-Protocol Label Switches

Answer 20

Allows carriers to define a specific path through the core network for a particular customer’s data. It requires special routers and headers.

Question 21

What are the three special headers needed for Multi-Protocol Label Switches (MPLS)?

Answer 21

• Insert label
• Switch label
• Remove label

Question 22

Multi-Protocol Label Switch (MPLS) are sometimes called ____________

Answer 22

Layer 2.5

Question 23

What are the three Multi-Protocol Label Switch (MPLS) services?

Answer 23

• MPLS Virtual Private LAN Service
• Virtual Leased Line (VLL)
• Virtual Private Routed Network (VPRN)

Question 24

What is a Virtual Private Network? Draw a diagram

Answer 24

• Creates a private tunnel through the common carrier network.
• Can be either provider or customer provisioned
• see slides 18-19 for diagram

Question 25

How does a customer provisioned VPN differ from a provider provisioned VPN?

Answer 25

Customer provisioned VPN:

• uses customer provided and managed equipment.
• user computer must run VPN software that is compatible with the VPN gateway

Question 26

What is IPsec VPN? draw a supporting diagram

Answer 26

IPsecurity VPN:

• uses customer provided and managed VPN gateway to terminate VPN connections
• user computer runs IPsec software provided by gateway vendor
• IPsec encapsulates and encrypts data sent between PC and gateway

Question 27

What are the three main types of IPsec VPNs?

Answer 27

• Intranet VPN
• Extranet VPN
• Access VPN

Question 28

What are three main factors to consider when purchasing WAN services?

Answer 28

• effective data rates and cost
• reliability
• network integration

Question 29

Name some ways to improve performance for WANs.

Answer 29

1. Upgrade routers that connect to the WAN
2. Analyse traffic to find circuits approaching capacity
3. Examine why circuits are at capacity
4. Shift Network Usage
5. Redesign the network