Introduction

Question 1

What is a brief definition of the internet

Answer 1

Billions of connected computing devices. A network of networks.

Question 2

What is packet switching?

Answer 2

Packet switching is used to transfer data in the form of packets. Data is broken up into small pieces called “packets” and sent. It is then reassembled at its destination.

Question 3

What are communication links?

Answer 3

Means of transferring data on the internet, for example, fiber, copper, radio, satellite.

Question 4

What is a network?

Answer 4

A collection of devices, routers and links which is managed by an organization.

Question 5

What are protocols?

Answer 5

Protocols are rules that determine formats for transferring data across networks.

Question 6

What is the purpose of wireless access networks?

Answer 6

Wireless access networks connect end systems to routers, and in turn, the internet.

Question 7

What are enterprise networks?

Answer 7

enterprise networks refers to the interconnected computer systems and resources within an organization, like within a university. Involves a mix of wired and wireless technology.

Question 8

What are data center networks?

Answer 8

High bandwidth links between servers and the internet, speeds of up to 100gbs.

Question 9

What are the two types of wires in physical media links?

Answer 9

Coaxial cables are bidirection copper conductors that provide broadband. They carry multiple channels with up to 100mbps per channel.

Fiber optic cable carry light pulses at extremely high speeds. 10-100gbs. Lower error rate, much more expensive but generally better otherwise.

Question 10

What are types of links in physical media?

Answer 10

Wireless radio - carries signal in waves on the electromagnetic spectrum. Can be interfered with by objects. No physical wire

Question 11

What are the two important network-core functions

Answer 11

Forwarding and routing
Forwarding - Moving arriving packets from the router’s input to the appropriate router output link.
Routing - Determining source to destination paths taken by packets.

Question 12

What is packet transmission delay and how is it calculated?

Answer 12

How many seconds it takes to transmit an amount of packets.
Calculated as L/R where L is the number of bit packets and R is the bps

Question 13

What is meant by store and forward?

Answer 13

The entire packet must arrive at a router before it can be transmitted to the next link.

Question 14

What is circuit switching?

Answer 14

Where end-end resources are allocated to and reserved for a call between source and destination. No shared links and you get basically guaranteed perfromance. It’s commonly used in telephone networks. It isn’t commonly used otherwise as circuit switching does not efficiently use a network’s resources, and also can’t be scaled effectively.

Question 15

What is meant by queuing in packet switching?

Answer 15

When packets arrive at a router faster than they can be serviced, they will queue. If the memory buffer in the router fills up, the packets can be dropped and lost, and they will need to be re-requested.

Question 16

What’s the difference between FDM and TDM?

Answer 16

FDM dedicates frequencies into narrow bands, each call has its own band and can transmit whenever within that narrow band, but can’t exceed that max rate.

TDM divids time into slots, and each call has an allocated slot where they can transmit at a higher maximum rate, but only in that time slot.

Question 17

What’s a brief description of the internet’s network of networks.

Answer 17

Each access net is connected to an internet service provider via a router, which communicates with other routers and other ISP’s routers (via internet exchange points). Additionally, content provider networks like google may run their own network, to bring services to end users.

Question 18

How does packet delay occur?

Answer 18

Nodal processing - checking bit errors, determining output link
Queing delay - waiting at an output link to be transmitted, depends on congestion of router
Transmission delay - Packet length (bits) divided by transmission rate (bits per second)
Propogation delay - length of physical link
All adds up, resulting in packet delay.

Question 19

How does packet loss occur?

Answer 19

Packets are lost when they queue, and arrive at a full queue, where they are dropped. They must then be retransmitted by the previous node or the source. Or sometimes they aren’t at all.

Question 20

What is meant by throughput?

Answer 20

The rate at which bits are sent from sender to receiver.

Question 21

What are five network layers (and in what order)

Answer 21

Application, transport, network, link and phyical.

Question 22

What happens in the application layer?

Answer 22

Messages are exchanged to implement some application service using services of the transport layer.

Question 23

What happens in the transport-layer?

Answer 23

Protocol transfers messages from one process to another, using services of the network layer.W

Question 24

What happens in the network layer?

Answer 24

Network-layer protocol transfers transport-layer segment from one host to another, using link layer services.

Question 25

What happens in the link layer?

Answer 25

The link-layer protocol transfers datagram from host to neighboring host, using network-layer services.

Question 26

What is the physical layer?

Answer 26

The physical link between the two networks.