Lecture 2

Question 1

What is a network?

Answer 1

Any thing reticulated or decussated, at equal distances, with interstices between the intersections.

Question 2

What is the G(V,E) notation?

Answer 2

A graph is made up of vertices & edges. Vertices are all the dots and edges are which dots connect to which.

Question 3

What does a router do?

Answer 3

Handle packets from different networks.

Routes traffic between two different networks.

Question 4

What are the three different communication modes?

Answer 4

Simplex - One way only
Half Duplex - Two ways, one at a time
Duplex - Two ways both at the same time.

Question 5

What is the difference between symmetric and asymmetric communication?

Answer 5

Symmetric: Send and receive using the same communication media.

Asymmetric: Send and receive using different communication medias.

Question 6

Name the four different communication methods. Unicast…

Answer 6

Unicast: 1-to-1
Broadcast: 1-to-all
Multicast: 1-to-many
Anycast: 1-to-any

Question 7

Name three different types of area networks.

Answer 7

Local Area Network (LAN): Devices often within the same building.

Metropolitan Area Network (MAN): Devices often within the same city.

Wide Area Network (WAN): Networks extending over large / multiple geographical regions.

BAN, PAN, Internet and Interplanetary Internet

Question 8

I say CSMA, you say? (Two things)

Answer 8

CSMA/CD: Carrier Sense Multiple Access / Collision Detection. Send, if a collission is detected wait random time and then send again.

CSMA/CA: Carrier Sense Multiple Access / Collision Avoidance.

Question 9

What is the truncated binary exponential backoff?

Answer 9

After a collision is detected by, each station waits for a random time between [0, 1] slot before attempting to retransmit again.

Each collision is expands this window to increase the chances of a collision.

Question 10

What is the maximum amount of tries in the binary exponential backoff?

Answer 10

10.

Question 11

What is a VLAN?

Answer 11

A Virtual LAN (VLAN) is a group of devices on one or more LANs that are configured to communicate as if they were attached to the same wire.

Physically they may be on the same device, but logically they are different and cannot talk to each other.

Question 12

What is ARP used for?

Answer 12

Converting IP Addresses to MAC Addresses, allows for Layer 2 communication.

Question 13

Which type of hardware is controlled by IEEE802.11?

Answer 13

Wireless Adapters.

Question 14

What is the bus topology?

Answer 14

Multiple nodes are connected via a main shared-half duplex link.

Question 15

What are the pros of bus topology?

Answer 15

Simple connection and extension of computers and other devices.

Cheap as chips.

Question 16

What are the cons of bus topology?

Answer 16

Single point of failure

Bigger networks would not work well as high probs of packet crashing ya’ll.

Question 17

What is ring topology?

Answer 17

All nodes have exactly two other nodes connected to each other, to form a circle.

Question 18

What are the pros of ring topology?

Answer 18

Better performance than bus topology

No central host

Relatively simple to add new hosts

Question 19

What are the cons of ring topology?

Answer 19

Faulty host can break the ring

Increasing communication delay as a function of number of hosts

Higher complexity in configuring new hosts

Question 20

What is the star topology?

Answer 20

All hosts connected to a central node. I.E. a switch.

Question 21

What are the pros of a star topology?

Answer 21

No disruptions to the network when adding/removing devices.

Easy to install and simple wiring.

Simple fault detection and component replacements.

Question 22

What are the cons of a star topology?

Answer 22

Central node (hub) is the single point of failure.

More expensive than linear bus topologies - costs more cable than bus topology.

Question 23

What is mesh topology?

Answer 23

All nodes directly connected to all other nodes.

Question 24

What is the fat tree concept?

Answer 24

For every downlink there’s an uplink.

I.E. if two servers connect to a switch, that switch should have two uplinks to the next intermediary device.

Question 25

What is congestion?

Answer 25

When the input data rate is higher than the output rate.

X = Input, Y = output.

X < Y - No Congestion
X = Y - No Congestion
X > Y - Congestion

Question 26

If there is congestion on a network what normally occurs?

Answer 26

Queue increases
Buffer overflows
Packet drop