Chapter 1

Question 1

Networks

Answer 1

Collection of devices, routers, links.

Question 2

Network protocols

Answer 2

Computers rather than humans

Question 3

Access Network

Answer 3

Network that connect the edge device into the first hop router, into the larger internet

Question 4

Transmission Rate

Answer 4

How fast a network is

Question 5

Cable Access Network

Answer 5

A physical cable connecting multiple homes to a single cable head.

Question 6

Bit

Answer 6

Propagates between transmitter / receiver pairs.

Question 7

Physical Link

Answer 7

What lies between transmitter and receiver.

Question 8

Guided Media

Answer 8

Some kind of physical wire / cable.

Question 9

Unguided Media

Answer 9

Signals propagate freely (ex. Radio)

Question 10

Packet Switching

Answer 10

End hosts take application level messages, divide them into chunks, put them inside packets and sent them into the internet.

Question 11

Forwarding

Answer 11

A local action. Moving an arriving packet from the input link of the router to its appropriate output link. Controlled by the forwarding table.

Question 12

Routing

Answer 12

A global action. Determined the source to destination paths taken by paths.

Question 13

Packet Transmission Delay

Answer 13

Takes L / R seconds to transmit (push out) L-bit packet into link at R bits.

Question 14

Packet Transmission Delay

Answer 14

Takes L / R seconds to transmit (push out) L-bit packet into link at R bits.

Question 15

Store and Forward

Answer 15

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

Question 16

Queueing

Answer 16

Occurs when work arrives faster than it can be serviced.

Question 17

Packet Queuing

Answer 17

If arrival rate (in bps) to link exceeds transmission rate (in bps) of link for some period of time.

Question 18

Packet Loss

Answer 18

With packet queueing, packets can be dropped (lost) if memory (buffer) in router fills up

Question 19

Frequency Division Multiplex (FDM)

Answer 19

Each allocated each own band. Can transmit at max rate or that narrow band.

Question 20

Time Division Multiplexing (TDM)

Answer 20

Each call allocated periodic slots, can transmit at max rate of wider frequency band only during its time slot.

Question 21

Excessive Congestion Possible

Answer 21

Packet delay and loss due to buffer overflow.

Question 22

Sources of Delay

Answer 22

1. Processing delay
2. Queuing delay
3. Transmission delay
4. Propagation delay

Question 23

Processing Delay

Answer 23

Associated with forwarding table lookup forwarding a packet through the switch.

Question 24

Queueing Delay

Answer 24

Amount of time a packet has to wait to queue at an output link for transmission.

Question 25

Transmission Delay

Answer 25

Time is takes for all the bits in those packets to be pushed into outgoing link.

Question 26

Propagation Delay

Answer 26

Amount it takes from when a bit first enters the sending side of the link till it’s out.

Question 27

Throughput

Answer 27

The rate (bits / sec) that are being sent from a sender to a receiver.

Question 28

Layers

Answer 28

1. Application layer 2. Transport layer 3. Network layer 4. Link layer 5. Physical layer

Question 29

Application layer

Answer 29

Includes application layer protocols that control the sending and receiving of messages among the distributed pieces of the system. (HTML, IMAP, SMTP, DNS)

Question 30

Transport Layer

Answer 30

Transports application layer messages form one process to another (TCP, UDP).

Question 31

Network Layer

Answer 31

Transports data from one end device or host to another. Routing of data grams from source to destination (IP, Routing protocols).

Question 32

Link Layer

Answer 32

Transfers data between two network devices that are at either ends of the same communication link. Data transfer between neighboring network devices elements (Ethernet, WiFi).

Question 33

Physical Layer

Answer 33

Controls the sending of bits into this communication link. Bits on wire

Question 34

Application Layer Role

Answer 34

Exchanges **messages** to implement some application service using services of transport layer.

Question 35

Transport Layer Role

Answer 35

Exchanges those messages from one part of the network to the other. It will take a message from the application layer and include some additional information with that message to create a new data unit, known as a **segment**.

Question 36

Network Layer Role

Answer 36

Encapsulated the transport layer segment and adds its own link layer intonation header to create a network layer **datagram**.

Question 37

Link Layer Role

Answer 37

Encapsulated the network layer datagram and adds its own link layer information header. The protocol data unit is transferred between the link sender and the link layer is known as a **frame**.

Question 38

Packet Sniffing

Answer 38

Broadcast media. Promiscuous network interface reads / records all packets passing by.

Question 39

Denial of Service (DoS)

Answer 39

Attackers make resources unavailable to legitimate traffic by overwhelming resource with bogus traffic.

Question 40

Lines of Defense

Answer 40

1. Authentication 2. Confidentiality 3. Integrity Checks 4. Access Restrictions 5. Firewalls

Question 41

Lines of Defense

Answer 41

1. Authentication 2. Confidentiality 3. Integrity Checks 4. Access Restrictions 5. Firewalls