Chapter 1

Question 1

Host or end systems

Answer 1

A network of billions of computing devices

Question 2

Internet Protocol address

Answer 2

unique, numeric value assigned to each host

Question 3

packets

Answer 3

clusters of data. labeled with IP address of sender and receiver

Question 4

Direct traffic using addresses on the packets

Answer 4

routers and switches

Question 5

Internet

Answer 5

worldwide network of interconnected computers

Question 6

Web

Answer 6

worldwide network of interconnected hypertext pages, connects to web server apps, one of many apps built on top of the internet

Question 7

protocols

Answer 7

define how devices should interoperate

Question 8

network protocol

Answer 8

defines proper communication patterns between devices; types of messages that can be sent; structure of the messages; possible responses and actions to take

Question 9

Network edge

Answer 9

hosts: clients and servers; have only one link to the internet

Question 10

network core

Answer 10

routers connecting various Internet parts; like hosts with multiple links and living only to relay others’ packets

Question 11

physical media

Answer 11

wired and wireless communications links

Question 12

circuit switching

Answer 12

electrical connection is established end-to-end for each call; originally done by moving cabled plugged into switchboards; later pulse and tone dialing automated switching

Question 13

Public Switched Telephone Network (PSTN)

Answer 13

still uses analog signals on twisted pair cables

Question 14

coaxial cables

Answer 14

much better signal carrier, less sensitive to noise, and carry more data; designed to carry video

Question 15

Digital Subscriber Line

Answer 15

phone calls do not interfere with data exchange; splitter after the DSLAM and before the modem

Question 16

Frequency Division Multiplexing

Answer 16

way to share a single communication medium; different channels are simultaneously transmitted on different frequency bands; no taking turns; coaxial cable

Question 17

Radio

Answer 17

wireless/unguided medium; signal flows through open space; objects can block or reflect signal; no need to wire up every device; lots of noise, interference, and competition for the spectrum

Question 18

circuit switching in the PSTN

Answer 18

need a dedicated electrical path that remains that way until the parties hang up; guaranteed performance; may have to wait for a free line; wasting during silence

Question 19

Packet switching

Answer 19

way in which computer networks send data by sending packets

Question 20

Packet

Answer 20

destination address; sender address; limited space for message; large messages must be split into multiple pockets; may arrive in any order; may take different paths to destination; delivery is “best effort” and not guaranteed

Question 21

throughput

Answer 21

rate of data transfer (bandwidth); measured in bps; data arrives in discrete packets so throughput is calculated as an average over some time window

Question 22

latency

Answer 22

delay of an action; network latency is the time it takes for a bit of data to arrive at the destination

Question 23

communication link

Answer 23

bi-directional, point-to-point connection, allow 0’s or 1’s to be transmitted or idle, propagation delay, operates at a certain, constant bitrate

Question 24

propagation delay

Answer 24

the time it takes for bits to flow from sender to receiver

Question 25

store and forward

Answer 25

data takes several hops to reach destination; each intermediate router has a queue of packets waiting to be sent along to the next hop; FIFO order

Question 26

Packet switching

Answer 26

1) no fixed resource allocation 2) no theoretical limit to the number of users 3) In practice, it allows more users to use network

Question 27

Routers 2 responsibilities

Answer 27

1) distributed routing algorithms 2) packet forwarding

Question 28

Distributed routing algorithms

Answer 28

determine which address ranges are most quickly reachable on each of its outbound links

Question 29

Packet forwarding

Answer 29

direct packets according to the decisions made by the distributed routing algorithms

Question 30

Fours sources of packet delay

Answer 30

1) dproc: nodal processing delay - check bit errors 2) dqueue: queueing delay - time waiting at output link for transmission 3) dtransL transmission delay - packet size/ link bandwidth 4) dprop: propagation delay - length of the link / speed of light

Question 31

Structure of the Internet

Answer 31

Tiers

Question 32

TCP/IP stack

Answer 32

app; transport; network; link; PHY

Question 33

Application

Answer 33

supporting network applications

Question 34

transport

Answer 34

process-to-process data transfer

Question 35

network

Answer 35

routing of diagrams from source to destination hosts

Question 36

Link

Answer 36

data transfer between neighboring network elements

Question 37

PHY

Answer 37

bits "on the wire"

Question 38

Network layers in WWW

Answer 38

HTTP, TLS, TCP, IP, Ethernet Wifi

Question 39

HTTP

Answer 39

get web pages, images, etc. and post data to servers

Question 40

TLS

Answer 40

encrypt traffic

Question 41

TCP

Answer 41

byte streams (ordering, delivery confirmation, pacing); gives a file-like interface to network connections (read and write bytes); handles limited packet size, dropped and reordered packets

Question 42

IP

Answer 42

Forward packets across multiple hops; makes best-effort attempt to route packets to their destination IP

Question 43

Ethernet/wifi

Answer 43

share a communication link with multiple local devices

Question 44

sockets

Answer 44

analogous to a door; sending process shoves message door; sending process relies on transport infrastructure on other side of door which brings message to socket at receiving process; IP address is device's unique identifier

Question 45

TCP Streams

Answer 45

provides applications with a file-like abstraction for a network connection (read and write); packets are a reassembled and ordered automatically by the OS/library; must establish a connection first (3 way handshake)

Question 46

TCP provides

Answer 46

- port numbers os a computer can have multiple network connections - message fragmentation and reassembly - delivery confirmation and retransmission - flow control: sender won't overwhelm receiver - congestion control: throttle sender when network is overloaded

Question 47

UDP

Answer 47

- simpler than TCP - No reliable connection - Protocols deal with more error conditions -