Introduction

Question 1

Network Edge

Answer 1

Hosts (clients and servers), end of data route, sends packets of data, takes application message

Question 2

Network Core

Answer 2

Route must pass through it.
Interconnected routers.

Question 3

Network of Networks

Answer 3

Devices are connected using a hierarchy of networks

Question 4

Host

Answer 4

Client and server. End system that provides user with information/data

Question 5

Protocol

Answer 5

Define format and order of messages sent and received among network entities and actions taken on message transmission/receipt.
HTTP (web), TCP, IP, 4G, Ethernet.

Question 6

ISP

Answer 6

Internet Service Provider, provides connection between host and network

Question 7

Internet Structure

Answer 7

1. Network edge
2. Access networks, Physical media
3. Network core

Question 8

Access Networks/ISP

Answer 8

Residential, institutional, or mobile access networks. (within an organization). Smallest type of network

Question 9

Types of Access Networks

Answer 9

1. Cable-based Access
2. Digital subscriber line
3. Home networks
4. Wireless network
5. Enterprise network
6. Data Center network

Question 10

Cable-Based Access Network

Answer 10

Network of cable/fiber that connectes homes to ISP router.
Homes share connection from access network to cable headend.

Question 11

Digital Subscriber Line Access Network

Answer 11

Uses existing telephone line to central office DSLAM. Voice and data transmitted at different frequencies.
Data over DSL phone line goes to Internet. Voice over DSL phone goes to telephone net.

Question 12

Home Access Network

Answer 12

Wired: Headend/central office to modem to router to host
Wireless: Headend/central office to modem to router to Wifi access point to host

Question 13

Wireless Access Network

Answer 13

Through access point.
Wireless LAN: 100ft
Wide-Area Cellular: provided by mobile/cellular network operator

Question 14

Enterprise Access Network

Answer 14

Companies, universities, etc.
Mix of wired, wireless link technologies (mix of switches and routers)

Question 15

Data Center Access Network

Answer 15

High-bandwidth links connects many servers together and to the Internet

Question 16

Transmission Rate

Answer 16

Link capacity or bandwidth.
Time needed to transmit bit packet into link = L (bits) / R (bits/sec)

Question 17

Radio Link Types

Answer 17

1. Wireless LAN (wifi)
2. Wide-area
3. Bluetooth
4. Terrestrial microwave
5. Satellite

Question 18

Packet Switching

Answer 18

Host breaks application-layer messages into packets

Question 19

Forwarding

Answer 19

Move arriving packets from routers input link to appropriate output link.
LOCAL ACTION

Question 20

Routing

Answer 20

Determine source-destination paths taken by packets (routing algorithms)
GLOBAL ACTION

Question 21

Packet Transmission Delay

Answer 21

Takes L/R seconds to transmit L-bit packet into link at R bps.

Question 22

Store and Forward

Answer 22

Entire packet must arrive at router before it can be transmitted on next link.

Question 23

Parts of Packet Switching

Answer 23

Store and forward, queueing

Question 24

Queueing and when does it occur

Answer 24

When router becomes overloaded with packets. Can cause data loss. Occurs when work arrives faster than it can be serviced.

Question 25

Circuit Switching

Answer 25

Alternative to packet switching. End to end resouces allocated to, reserved for the 'call' (no sharing) between source and destination. Call gets dropped if max num of connection is reached. Can use FDM or TDM

Question 26

FDM

Answer 26

Frequency Division Multiplexing. Used in circuit switching. Optical, electromagnetic frequencies divided into narrow frequencies bands. Each call allocated its own band

Question 27

TDM

Answer 27

Time Division Multiplexing. Used in circuit switching. Time divided into slots, each call allocated periodic slots

Question 28

Packet Switching VS Circuit Switching

Answer 28

Circuit-switching can only serve up to 10 users at a time, while packet-switching can serve 10 or more users. However, packet switching can lead to data loss as resources are not reserved.

Question 29

Regional ISP

Answer 29

Provides access to subscribers in a franchise area. Higher then Access ISP

Question 30

IXP

Answer 30

Internet Exchange Point. Physical location through which ISP companies can exchange internet traffic. Higher then Regional ISP

Question 31

Tier 1 ISP

Answer 31

Commercial ISPs, national and international coverage (Sprint, AT&T, NTT), Higher then IXP, same as Content Provider Network

Question 32

Content Provider Network

Answer 32

Private network that connects data centers to internet, bypass Tier-1 and Regional ISPs. Same level as Tier-1

Question 33

When does Packet Loss occur?

Answer 33

Occurs when memory to hold queued packets fills up

Question 34

Packet Delay Calculation

Answer 34

Nodal processing + queueing delay + transmission delay + propagation delay = packet delay

Question 35

Nodal Processing

Answer 35

Time it takes for router to process incoming packets (check bit errors, determine output link)

Question 36

Queuing Delay

Answer 36

Time spent waiting for output link, depends on congestion level of router

Question 37

Transmission Delay

Answer 37

Time it takes for packet to leave router through output link. L/R, L is packet length (bits) and R is link transmission rate (bps)

Question 38

Propagation Delay

Answer 38

Time it takes for packet to travel to next router or final destination. d/s, d is length of physical link and s is propagation speed

Question 39

Traceroute Program

Answer 39

Provides delay measurement from source to each router along end-end Internet path to destination. Sends three packets to each router on path, router then returns packets and time is calculated.

Question 40

Throughput

Answer 40

Rate (bits/time unit) at which bits are being sent to receiver.

Question 41

Instantaneous Throughput

Answer 41

Rate (bits/time unit) at given point in time

Question 42

Average Throughput

Answer 42

Rate (bits/time unit) over longer period of time, uses minimum throughput of entire path

Question 43

Bottleneck Link

Answer 43

Link on end-end path that constrains overall throughput