W8 Ethernet

Question 1

Most popular wired ethernet standards today?

Answer 1

IEEE (Institute of Electrical and Electronics Engineers) 802.3

Question 2

IEEE 802.3 advantages:

Answer 2

• Great cost to performance ratio

- Being developed into a MAN AND WAN technology

Question 3

Wireless Ethernet 802.11:

Answer 3

• Most popular method to access internet

- Works together with wired connection to provide seamless communication

Question 4

Wired Ethernet 802.3:

Answer 4

• Network but in a hierarchical manner using workgroup and core switches
• Allows combining expensive and cheap equipment
• Workgroup switches connect devices to network
• Core switches connect switches to switches

Question 5

Frame Format:

Answer 5

Preamble – synchronization 0s and 1s
SFD – beginning of frame
Destination MAC address
Source MAC address
Length of Header
Data – Max 1500 bytes (MTU)
Pad – padding used on frames less than 64 bytes (needed for Collision Detection)
FCS – 4 bytes
Total size 1518 bytes

Question 6

Types of Ethernet Networks:

Answer 6

Gigabit Ethernet: IEEE 802.3z

10 Gigabit Ethernet: IEEE 802.3ae

Power over Ethernet (PoE): IEEE 802.3-2012

Metro Ethernet

Question 7

3 Types of Switches

Answer 7

• Store and Forward
• Cut Through
• Fragment-free switching

Question 8

Store and Forward switches:

Answer 8

• Receives entire frame and stores in memory
• Checks errors by computing the CRC and checking frame length
• If OK looks at destination address (if not deletes frame)
• Forwards the frame out the destination port

Question 9

Cut Through Switches:

Answer 9

• Starts to forward the frame as soon as it receives the destination address
• Does no error checking
• Advantage - very fast used ,on high speed backbones
• Disadvantage - may waste bandwidth forwarding frames with errors

Question 10

Fragment-free switching:

Answer 10

• Lies between the extremes of cut-through switching and store and forward switching
• First 64 bytes of frame are read and stored
• If all header data appears correct, switches begin transmitting

Question 11

RSTP:

Answer 11

Rapid Spanning Tree Protocol
A hierarchical network cannot have loops
Network prone to single points of failure
RSTP protocol to allow backup links.
Core switch polls the Main switch to see if alive.
If true – ignores backup link
If false – uses backup link

Question 12

802.1x Port Security:

Answer 12

• Designed to protect data ports

- Divides the port into 2 virtual ports

Question 13

WLAN:

Answer 13

Wireless Local Area Network:

• Uses radio frequency to transmit and receive data
• WLAN spec replaced by WPA (Wi-fi protected access) to address security problems

Question 14

Problem with WPA2:

Answer 14

• Public wifi networks are open and allow traffic to be sent over them that isn’t encrypted

Question 15

WPA3 solution:

Answer 15

• Encrypts all traffic between a device and wifi access point by using a unique key, to avoid MATM (Man in the middle) attacks)
• Not as secure as authenticated encryption

Question 16

Wireless errors:

Answer 16

Greater attenuation than copper or fiber optic cable

“Absorptive attenuation” of plants

Higher frequencies do not bend around objects can get shadow or dead zones

Question 17

Wireless frame format:

Answer 17

• Frame Control
• Duration (16 bit field)
• MAC of sender
• MAC of AP
  MAC of next wifi device
• MAC address (optional)
• Sequence control
• Payload - message
• CRC (12 bits, error detection)

Question 18

Rouge Access Point:

Answer 18

• Unauthorized access point installed with network SSID

- Created by intruder to steal data or by employee who wants unfettered access

Question 19

Evil Twin:

Answer 19

An access point operating at high power with network SSID

• Wireless devices connect to strongest signal. Client thinks imposter is the real AP
• Intruder has full access and can alter communication without other side knowing
• Used to steal personal info or corporate intellectual property

Question 20

VPN:

Answer 20

Virtual Private network:

• Costly, but allows use of internet as extension of private network
• encrypts outbound traffic, encapsulates it in unencrypted IPv4 packet
• Destination VPN removes IPv4 packet from inbound traffic
• Decrypts the message and forwards to destination host