The Bits and Bytes of Computer Networking 5

Question 1

What are the specifications of wireless networks defined by?

Answer 1

The IEEE 802.11 standards.

Question 2

How is data transferred in wireless networks?

Answer 2

Through radio waves.

Question 3

What are 3 differences between different 802.11 standards?

Answer 3

They operate at different frequency bands, different channel widths, have different speeds.

Question 4

What is a frequency band?

Answer 4

A certain section of the radio spectrum that is agreed to be used for certain communications.

Question 5

What are the 2 most commonly used frequency bands for Wi-Fi, and what are the differences between the 2?

Answer 5

2.4 Ghz - slower, more susceptible to interference, larger range.

5 Ghz - faster, less range.

Question 6

How many address fields does an 802.11 data frame have, and what are they?

Answer 6

4;

1 Source device MAC
2 Destination device MAC
3 MAC of receiving WAP
4 MAC of sending WAP

Question 7

What are 3 ways to configure a wireless network?

Answer 7

1 Ad-hoc networks
2 LAN / WLAN
3 Mesh Networks

Question 8

Describe the configuration of an ad-hoc wireless network.

Answer 8

Simplest type, nodes speak directly to each other, no supporting network infrastructure.

Question 9

Describe the configuration of a LAN / WLAN.

Answer 9

Consists of one or more WAPS, connected to gateway routers, which act as a bridge between the wired LAN and wireless LAN.

Question 10

Describe the configuration of a mesh wireless network. What is a benefit of this kind of network?

Answer 10

Is connected to a wired network, can have multiple WAPs, not all need to be connected to wired network, devices communicate with each other.

Benefit - increase performance and range of a wireless network.

Question 11

What are channels?

Answer 11

Individual, smaller sections of the frequency band used by a wireless network.

Question 12

What is a collision domain?

Answer 12

Any network segment where one computer can interrupt another.

Question 13

What is a benefit of using channels in wireless networks?

Answer 13

Help avoid collision domain, wireless networking equipment can auto sense which channels are congested and use another.

Question 14

What does WEP stand for, and what is it used for?

Answer 14

Wired Equivalent Privacy - an encryption technology. WEP key has 40 bits - not good.

Question 15

What is the difference between WPA and WPA2?

Answer 15

Wi-Fi Protected Access, encryption technology.

WPA key = 128 bits.
WPA2 key = 256 bits.

Question 16

How do cellular wireless networks differ to regular wireless networks?

Answer 16

A cellular network is a radio network distributed over land through cells where each cell includes a fixed location transceiver known as base station

Question 17

Aside from encryption, what is another security measure used in wireless networks?

Answer 17

MAC filtering, only allow certain devices to connect to your network.

Question 18

What does ICMP stand for, and what is it used for?

Answer 18

Internet Control Message Protocol - used by a router etc to communicate back to the source, why a transmission has failed.

Question 19

What are 2 tools to check network connectivity (at the network layer)?

Answer 19

Ping, traceroute / tracert (windows).

Question 20

What are the 2 steps in using a Ping message? (Name each step)

Answer 20

1 In command line interface - type “ping” followed by an IP address or a FQDN = “echo request”.

2 If destination is able to communicate on the network it will send an “echo reply” message.

Question 21

How does traceroute work?

Answer 21

It will send multiple packets, first with the ttl = 1, second with ttl = 2, and so on. This results in an ICMP time exceeded message being returned from every node along the route. Each time 3 packets will be sent.

Question 22

How do ping and traceroute output differ?

Answer 22

Ping output is basic info regarding the destination IP, roundtrip time and success rates of packets being sent.

Traceroute output is more detailed, with info about every router along the route, IP addresses and roundtrip time of each.

Question 23

What are 2 tools to test port connectivity (at the transport layer), what OSs do they work on?

Answer 23

Netcat - Linux / MacOS

Test-NetConnection - Windows

Question 24

When using the netcat tool, how can you tell if the connection has succeeded or failed?

Answer 24

Failed - command will exit.

Success - will see a blinking cursor waiting for more input.

Question 25

What are 2 flags you can use with netcat?

Answer 25

• z = zero input / output mode, do not want to send / receive data from the port.
• v = verbose, makes the output more legible for humans.

Question 26

How would you enter a netcat and a Test-NetConnection command in the shell, to test connection to googles port 80? (with at least one flag)

Answer 26

netcat = “nc -v -z google.com 80”

Test-NetConnection = “Test-NetConnection google.com -port 80”

Question 27

What is a command you can use to look up the IP of a domain? (name resolution tool)

Answer 27

nslookup twitter.com

Question 28

What are public DNS servers? Give 2 IP addresses and name who they belong to.

Answer 28

Name servers set up so anyone can freely use them.

Level 3 communications = 4.2.2.4
Google = 8.8.8.8