COSC203 - PART IV

Question 1

What are two network-layer functions?

Answer 1

Routing and forwarding

Question 2

In SDN, forwarding is performed at the ___ plane, and routing is performed at the _____ plane.

Answer 2

Data, control

Question 3

This is at traditional approach for the network control plane.

Answer 3

Per-router control.

Question 4

This type of networking enables logically centralised control by defining a control and data plane.

Answer 4

Software defined networking

Question 5

What is considered a “good” route?

Answer 5

Least cost, fastest, and least congested.

Question 6

What are the four routing algorithm classifications?

Answer 6

Global, static, dynamic, and decentralised.

Question 7

What are two characteristics about link state routing?

Answer 7

centralised - link costs are known to all nodes,
and iterative - after k iterations, the least cost path to k destinations is known.

Question 8

Notation for the current estimate of the least-cost-path from source to destination v

Answer 8

D(v)

Question 9

The notation for the predecessor node along path from source to v

Answer 9

p(v)

Question 10

This notation for a set of nodes whose least-cost-path is definitively known

Answer 10

N’

Question 11

This is a group of networks and routers controlled by a single administrative authority

Answer 11

Autonomous system

Question 12

This protocol is used by hosts and routers to communicate network-level information

Answer 12

ICMP (Internet Control Message Protocol)

Question 13

What is the responsibility of the data link layer?

Answer 13

Transfer datagram from one node to physically adjacent node over a link

Question 14

What is the difference on flow control between the transport and link layers?

Answer 14

Transport is end-to-end and byte-oriented.
Link layer is single link and frame-oriented.

Question 15

What is the principle of error detection in flow control at the link layer?

Answer 15

Add additional bit(s) to detect and correct bit errors (i.e. redundancy)

Question 16

Can a single parity correct single bit errors?

Answer 16

No - only detect.

Question 17

This kind of check is a more powerful error-detection coding

Answer 17

CRC - Cyclic Redundancy Check

Question 18

This protocol is a distributed algorithm that determines how nodes share the channel

Answer 18

(MAC) - Medium Access Control protocol

Question 19

This provides access to the channel in ‘rounds’

Answer 19

TDMA - Time Division Multiple Access

Question 20

What is FDMA?

Answer 20

Frequency Division Multiple Access - it divides the channel spectrum into frequency bands

Question 21

What equation is this and which routing method does it relate to?

Answer 21

Bellman-Ford, which is what distance vector routing is based on.

Question 22

What services are performed at the data link layer?

Answer 22

Framing and link access.

Question 23

Where is the link layer implemented?

Answer 23

The link layer is implemented in the network interface card or on a chip, which has a unique identifier - the MAC address.

Question 24

Which layers of the OSI model have flow control?

Answer 24

Transport and data link layer

Question 25

Which version of ALOHA is simpler, and can transfer data at any time?

Answer 25

Pure ALOHA

Question 26

Which version of ALOHA can only transmit data at the beginning of a time slot, thus is more synchronised?

Answer 26

Slotted ALOHA

Question 27

In Pure ALOHA, there is no synchronisation. What is a consequence of this?

Answer 27

The collision probability increases.

Question 28

This version of CSMA has the human analogy of ‘don’t interrupt others’ i.e. it listens before transmitting.

Answer 28

Simple CSMA

Question 29

This version of CSMA has the human analogy of ‘the polite conversationalist’ i.e., Collision Detection.

Answer 29

CSMA/CD

Question 30

What is the third step in this slide?

Answer 30

3. If NIC transmits entire frame without collision, NIC is done with the frame.

Question 31

Two MAC protocols for “taking turns”

Answer 31

Polling and token passing

Question 32

What are some of the concerns of polling? (MAC protocol)

Answer 32

Polling overhead, latency, single point of failure (master)

Question 33

What are some of the concerns of token passing? (MAC protocol)

Answer 33

Token overhead, latency, single point of failure (token)