Intro Adnan

Question 1

In many ways, the cargo is segmented and loaded into a fleet of trucks, packets are analogous to
___, communication links are analogous to ___, packet switches are
analogous to ___, and end systems are analogous to ___. Link-layer switches are
typically used in ___, while routers are typically used in the ___.

Answer 1

trucks, highways and roads, intersections, buildings, access networks, network core

Question 2

TCP supports connection-oriented services. True or False?

Answer 2

True

Question 3

UDP supports connection-oriented services. True or False?

Answer 3

False

Question 4

Which apps use TCP? Provide examples

Answer 4

HTTP, FTP, Telnet

Question 5

Which apps use UDP? Provide examples

Answer 5

Streaming media, DNS, Teleconferencing

Question 6

Role of bit in physical media

Answer 6

propagates between

transmitter/rcvr pairs

Question 7

Physical link

Answer 7

what lies
between transmitter &
receiver

Question 8

Packet transmission delay formula

Answer 8

length of packet / transmission rate

Question 9

Describe ring topology? Pros and cons

Answer 9

Every computer serves as a repeater to boost signals. Very expensive to add computers, more expensive

Question 10

Bus Topology? Pros and cons?

Answer 10

Simple, low cost, single cable called trunk, only one computer can send message at a time

Question 11

Star Topology

Answer 11

Every computer connected to a single host, more cabling, more expensive

Question 12

Which topology does not exist? Mesh, Bus, Ring, Star, Hybrid, Total

Answer 12

Total

Question 13

How long does it take to send a file of 640,000
bits from host A to host B over a circuit-switched
network?
▪ All links are 1.536 Mbps
▪ Each link uses TDM with 24 slots/sec
▪ 500 msec to establish end-to-end circuit

Answer 13

1,536,000/24 = 64000
640,000/64,000=10 seconds
10 + .5 = 1-.5seconds

Question 14

one-hop numerical example:
▪ L = 7.5 Mbits
▪ R = 1.5 Mbps
▪ one-hop transmission
delay? end-to-end delay?

Answer 14

one-hop transmission = 5

end-to-end delay = 10

Question 15

PAN is

Answer 15

Personal Area Network

Question 16

LAN

Answer 16

Local Area Network

Question 17

CAN

Answer 17

Campus Area Network

Question 18

WAN

Answer 18

Wide Area Network

Question 19

MAN

Answer 19

Metropolitan Area Network

Question 20

You are at distance of 10 000 meters. which area network will u cover?

Answer 20

MAN

Question 21

Why should one use and not use Peer-Peer architecture?

Give two examples for yes, and two for no

Answer 21

Less expensive hardware, easy to setup, low cost, easy to administer - yes

Not secure, no central point, additional load - no

Question 22

Describe Peer-Peer Architecture

Answer 22

Each computer is available for making its resources available to the other computers in network

Question 23

Which is bigger MAN or WAN?

Answer 23

WAN

Question 24

Name for sources of packet delay

Answer 24

Processing, Queuing, Transmission, Propagation

Question 25

Which delays are usually ignored?

Answer 25

Processing and Queueing

Question 26

Why does processing delay occur?

Answer 26

Check bit errors, determine output link

Question 27

Why does queuing delay occur?

Answer 27

Because of congestion level, if router not available, packet queued.

Question 28

Transmission delay formula

Answer 28

L/R

Question 29

Propagation delay formula

Answer 29

D/S

Question 30

L is 1000 bits and R (bandwith) is 1Kbps, what is transmission delay dt?

Answer 30

Dt= L / R = 1024 bps / 1000 bits = 1,024 sec

Question 31

If d =2.1 km and the efficiency is 70%, then what is dp

in µsec?

Answer 31

2.1 x10 3 m / 2.1x10 8 m/sec = 10-5

sec = 10-2msec = 10µsec

Question 32

Efficiency formula

Answer 32

Efficiency = dt-data /(dt-data + 2dp) = 1 / (1 + 2(dp

/dt-data)) . a = dp/dt

Question 33

RTT formula

Answer 33

2 * delay_prop

Question 34

Traffic intensity formula

Answer 34

La / R, a = d_p/d_t

Question 35

What does traffic intensity say us?

Answer 35

La/R ~ 0: avg. queueing delay small
La/R >= 1: avg. queueing delay large
La/R > 1: more “work” arriving
than can be serviced, average delay infinite!

Question 36

throughput?

Answer 36

rate (bits/time unit) at which bits

transferred between sender/receiver

Question 37

Derive throughput formula

Answer 37

Throughput = L / dtotal= L /(dt+2dp) = L * (R/R)/(dt+2dp)
(If we neglect dq + dnp + dt-ack) = R * (L/R) / (dt + 2dp) = R* dt / (dt + 2dp)
= R* 1 / (1 + 2a)
= n*R.

Question 38

Transmision time (dt) is 1 msec and propagation time (do) is 1 msec. what is efficiency

Answer 38

n = 1/3

Question 39

Which OSI models are not present in TCP/IP Model

Answer 39

Presentation Session

Question 40

Name OSI Model Layers

Answer 40

Application, Presentation, Session, Transport, Network, Data Link, Physical

Question 41

Name TCP/IP Model Layers

Answer 41

Application, Transport, Internet, Network, Physical