3213 Quiz 1

Question 1

What is ARPANET
-Type of connection, and name?

Answer 1

Computer to computer network
Wide area network

Question 2

How does ARPANET work

Answer 2

Switched network infrastructure
Packets of fixed size

Question 3

What is circuit switching? (Wired telephone network)
Pros/Cons?

Answer 3

Dedicated path between 1 or more links
Pros: Guaranteed QoS, fixed transmission rate, no data loss
Cons: Inefficient, and complex. One connection suffocates link vs packet switching

Question 4

What is Packet switching (ARPANET, Internet, 3G+)
Pros/Cons?

Answer 4

No dedicated path, packets transmitted independently.
Pros: links shared by many packets, packets accepted even under heavy traffic.
Cons: No QoS guarantee, packet delay/loss during traffic, overhead encapsulation traffic.

Question 5

LAN network topologies

Answer 5

Bus Topology
- Simple/inexpensive
- Single point of failure, collision = diminishing capacity
Ring Topology
- small frame (token) circulates dictating who can transmit data
- Fair access
- Breaks if any link fails
Star topology
- Each station connected directly to central node
- Central node broadcast and/or switch

Question 6

Hub vs Switch?

Answer 6

Only one station can transmit otherwise collision occurs, and broadcast data to all connected computers
Switch: Sends data only to specified computers.

Question 7

IP Addressing (Address format + Routing)

Answer 7

IP Address = Net ID + Host ID
IP Packets are routed only based on Net ID in destination IP Address
- Only has to know major networks/ smaller routing table -> Faster routing

Question 8

What is a protocol and its data unit type?

Answer 8

Set of rules that govern how two or more entities in a layer are interacting
ex: HTTP, TCP, IP
Communicate by exchanging Protocol Data units (PDU’s)

Question 9

What are services

Answer 9

Services wrapped in PDU’s, available at Serice Access Points (SAP)
layer n+1 transfers info by invoking services by layer n

Question 10

What is a Data link layer?
4 Main actions

Answer 10

Attempts to provide reliable communication over physical layer(same network)
Divides stream of bits into frames
adds header to specify address of receiver (MAC)
Adds trailer to header to detect/recover lost frames
Flow control

Question 11

What is a Network Layer
- Addressing, Routing, frag

Answer 11

Oversees delivery of packets between devices across multiple networks/links
- Logical addressing / scale to large networks
- provides routing for optimal path across large internetwork
- Fragmentation and reassembly of packets to accommodate different media.

Question 12

What is a transport layer?
Purpose

Answer 12

Network layer gets packet to receiver, transport gets entire message to correct process on receiver.
- Reliable mechanism for process to process
- Ensures data units are delivered error free, in sequence, with no loss/dup

Question 13

Transport Layer supporting purpose
- Addressing, segment, flow

Answer 13

Port addressing: Specifies port address to send to receiver
Segmentation and reassembly: Divide into segments containing sequence number, to reassemble message correctly, and identify/replace missing packets.
Flow and error control: Performed end to end

Question 13

The application layer does what?

Answer 13

Provides actual service/ interface to the user

Question 14

OSI Downfall reason?

Answer 14

TCP/IP Launched same time with 5 layer, less complex, more efficient

Question 15

TCP/IP Address model

Answer 15

Port address: Locally unique to differentiate different applications using same IP Address

IP Address: Globally unique, corresponding node in entire internet.

Physical Address: Globally Unique, or MAC Address, used to locate on LAN

Question 16

TCP/IP Encapsulation Model

Answer 16

TCP Header contains source and destination port numbers
IP Header contains source and destination IP addresses (Transport and protocol type)
D.L Header contains source and dest. MAC addresses (network protocol type)

Question 17

Analog Data

Answer 17

Refers to info that is continuous, continuous values in some interval

Question 18

Digital Data

Answer 18

Refers to discrete states, finite/countable number of values in range

Question 19

How many links for Mesh, ring, bus, and star topology

Answer 19

Mesh = n(n-1)/2
Ring = n links
Bus = n+1 (backbone link required)
Star = n + 1 (backbone link required)

Question 20

Sine wave components

Answer 20

Simple - cannot be decomposed further
Peak amplitude
Frequency
Phase

Question 21

Phase and deg/rad conversion

Answer 21

%offset respect to time = 0
360 = 2 pi rad

radians = degrees * pi / 180

Question 22

Freq/period relation

Answer 22

Frequency = completed cycles per second
Freq = 1/T
Period = Time to complete 1 cycle
Period = 1/f
Inversely proportional

Question 23

If composite signal is periodic, decomp of signals give signals with?

Answer 23

discrete freq

Question 24

If composite signal is non-periodic, decomp of signals give signals with?

Answer 24

continuous freq

Question 25

f is referred to as? (ex: freq = 3f)
int multiples of f are referred to as?

Answer 25

fundamental frequency
harmonics

Question 26

bit interval?
bit rate?

Answer 26

time required to send single bit
number of bit intervals per second

Question 27

A digital signal has 8 levels. How many bits can be represented per level?

Answer 27

log base 2 (8) = 3
3 bits represented per level

Question 28

digital signal, with all its
sudden changes mean what?

Answer 28

composite signal with infinite # of frequencies
Note: To create a perfect square wave of a composite signal, we must add all harmonic frequencies up to infinity to flush out the square shape.
Thus infinite # of frequencies.

Question 29

Bandwidth of a composite periodic analog signal is found how?
Why not digital?

Answer 29

Difference between highest and lowest frequencies in that signal
(B = f high - f low)
Digital has infinite frequency

Question 30

A nonperiodic composite analog signal has a bandwidth of 200 kHz,
with a middle frequency of 140 kHz and peak amplitude of 20 V.
The two extreme frequencies have an amplitude of 0. What is the lowest freq, and highest?

Answer 30

low=40, high = 240