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Chapter 1 Background Flashcards

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1
Q

What is the OSI Model

A
  1. Application Layer
  2. Presentation Layer
  3. Session Layer
  4. Transport Layer
  5. Network Layer
  6. Data Link Layer
  7. Physical Layer
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2
Q

What is the Physical Layer, what occurs in it?

A

The physical layer is responsbile for sending computer bytes along the network. The signaling annd cables. No protocols in this layer

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3
Q

What is the Data Link Layer, what occurs in it?

A

This is the foundation of communication. It has a MAC address on the ethernet. It also is the layer that has switches to control and communicate.

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4
Q

What is the Network Layer, what occurs in it?

A

This is the “routing” layer
Layer of internet Protocol (IP)
Transfer data through the internet

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5
Q

What is the Transport Layer, what occurs in it?

A

Post Office Layers where parcels are sent.
TCP and UDP protocols

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6
Q

What is the Session Layer, what occurs in it?

A

This layer has communication management. It has the control protocols such as: Start, Stop, Restart

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7
Q

What is the Presentation Layer, what occurs in it?

A

This is the encoding layer before the application layer

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8
Q

What is the Application Layer, what occurs in it?

A

The layer the eyes see.

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9
Q

What is an Internet Socket

A

This is a communication endpoint, when a social is creation the application gets back a file descriptor it can use.

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10
Q

The 2 Types of Sockets we talked in class

A

Stream Sockets (TCP)
Datagram Sockets (UDP)

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11
Q

IP Addresses

A

It is used for Host addressing in IPv4 IPv6.

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12
Q

What are ports used for?

A

Ports are used for addressing within the transport layer, UDP and TCP have 16 bit source port numbers

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13
Q

Can a socket be “bound to” a single port only?

A

Yes

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14
Q

If a port has multiple sockets bound to it? how do we know which socket should get the incoming data?

A

When the host recieves incoming data the OS used the source and dest IP Address along with src and dest port numbers and transport layer protocol identity to demultiplex a particiular socket.

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15
Q

what is the socket() function for TCP and UDP

A

For TCP, create a “stream” socket
For UDP, create a “Datagram” socket

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16
Q

what is the blind() functions purpose

A

For both UDP and TCP it associates a socket with a particular port on a local machine

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17
Q

what does the listen() function do

A

It creates a queue from incoming connections; socket is a passive socket

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18
Q

what is the accept() function

A

When there is a new connection this will create a new socket. Bound to the same port as the lisenting socket. This is a blocking call

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19
Q

How does demultiplexing work on TCP server?

A

All new connections are put in the queue for the listening socket bound to the specifed dest port.
All incoming traffic on the connection goes to the socket that was created when the connection was accepted.

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20
Q

What does the recvfrom() function do?

A

In addtion to data it gives you source ip, and src port number of the recieved UDP segement

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21
Q

What does the sendto() function do?

A

sends to the specified dest IP

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22
Q

What is tranmission media?

A

Physical pathways used to transmit signals between devices.
Guided and unguided.

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23
Q

Types of Guided Media?

A

Twisted Pair
Coaxial Cable
Household Wiring
Optical Fiber

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24
Q

Twisted pair

A

Pair of insulated copper wires spiralled together. Variables types. Includes telephone wiring

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25
Coaxial Cable
Better shielding than twisted pair, Higher data rates avaliable. Copper core surronded by insulation. Used in Cable TV Networks
26
Types of Unguided media
- Transmission via radio, microwave, infrared - ISM and U-NII Bands no need for a license to use - Satellites
27
Optical Fiber
Glass core surronded by glass claddingm surroned by plastic covering. Uses near-infrared. Avantges include immunity to electromagnetic interference. Very High data rates and distances possible.
28
What is unguided media
Transmission of data through the air using radio, microwave, infrared or visibile light.
29
What are common unlicensed frequency bands (ISM, U-NII bands)
2.4 GHz, 5 GHz commonly used for wifi, bluetooth, etc
30
What are "white spaces" in wireless communication
Frequences allocated to TV Broadcasts but left ununsed. Avaliable for unlicensed wireless use.
31
Advantage and disadvantage of higher frequency transmission?
Greater data rates and direction focus, but are sensitive to obstructions.
32
What provides stable "line-of-sight" communication
Geostationary Satellites positioned at 35,800km atitude
33
Uses and limitations of geostationary satellites
Broadcast TV, high data rates but long round trip times
34
what is Medium-Earth Orbit satellite
20,000km, GPS Satellites
35
What is a low-earth-orbit satellites
Satellites orbiting under 2000km
36
Advantages of Iridium satellites?
Low propagation delays, global availability.
37
What determines maximum data rate?
Properties of transmission channel, signal power, how the bits are represented as signals on the channel
38
Digital Modulation
The process of covering bits and the signals that represent them.
39
What is the benefit of using more than two channel states for transmission?
It increases data rates by encoding multiple bits in a single channel state
40
What is "baud"
Symbol rate; then umber of symbols tramsitted per second
41
Data rate formula (bps)
bps = bits per symbol * baud rate (symbols per second)
42
Calculate bits per symbol from the number of channel states (V)?
bits per symbol = log2(V), V is distinct channel states
43
What factors limit # of bits encoded by each symbol
Power of signal, complexity of transmitter/reciever, ingenuity of designer.
44
What other factor limits maximum symbol rate (baud)
channel bandwidth
45
Channel Bandwidth
Difference between highest and lowest signal frequencies a channel can transmit well
46
Nyquist's theorm
Maximum symbol rate on noise free channel = 2(H), H is bandwidth
47
Shannons Theorem
Maximum Data Rate bps = H Log2(1 + S/N), where S/N is signal to noise ratio
48
Baseband Modulation
Signals that occupy freqeunces from zero to some maximum based on signaling rate
49
NRZ Encoding
Non-return-to-zero, used distinct neg and pos voltages for bits 1 - 0 respectively
50
Why choose Manchester encoding over NRZ
Better clock revoer and balanced signals. Though less bandwidth efficient.
51
8B/10B encoding improvments on NRZ encoding?
It ensured balanced signals, improved clock recovery, limit run length and balance 0,1s.
52
Passband modulation scheme
Data signals modulate a carrier wave to occupy a certain frequency range
53
Differences between ASK, FSK, PSK modulation
ASK: Varies amplitude FSK: Varies Frequency PSK: Varies Phase
54
What is a quadrature Amplitude Modulation (QAM)
Modulates amplitude of two carrier waves combining both amp and phase modulation
55
Modem
Device converting digital bit streams into analog signals (vice versa)
56
Multipath in wireless communication
Reciever can get multiple copies of signals due to reflection from surfaces
57
Direct-Sequence Spread Sepctrum (DSSS)
Spreads bits accross many frequences using a chipping code to make signals robust against interference
58
Code Vision Multiple Access (CDMA)
DSSS Vairant where multple users can share frequneces at the same time using unique codes
59
Adaptive Frequency Hopping
Rapidly switching frequences to avoid those with interference or fading
60
Orthogonal Frequency Divison Multiplexing (OFDM)
Dividing a channel into many anrrow subchannelsm each carrying data with error correction.
61
Whats an advantage to OFDM regarding multipath interference
Narrow the subchannel experience into uniform multipath effects. Long symbol durations allow guard intervals.
62
What is MIMO and give me examples of systems using MIMO
Multiple-input Multiple-output; uses mutliple sender and reciever antennas to increase data rate or signal reliability. Ex: 4G, 5G, Wifi
63
How does Shannons Theorem apply to wireless "channels"
For wireless, the channel includes air and multipath environment; multiple antennas exploit this multipath environment
64
Explain SISO, SIMO, MISO
SISO: Single input, single output; exploit multipath using fake receiver SIMO: Single input, multiple output; exploit spatial Diversity MISO: Multiple sender, single reciever; H log2(1+mS/N)
65
Packet Switching
Fundamental networking paradigm used in computer networks. Data is broken into smaller units called packets.
66
What is PSTN
Public Switched Telephone Network a large scale, circuit switched communication network using dedicated connections
67
How does PSTN digitize analog voice signals
Using Pulse Code Modulation: Analog signals are smalped 8k per second producing a digitized voice call at 64 Kbps.
68
What multiplexing techniques did PSTN use and what replaced it?
PSTN used Frequency Division Multiplexing FDM on local hops and Time Divison Multiplexing TDM. PSTN is being replaced by Voice-over-IP
69
Five Sources of delay in packet switching networks
Propagation Delay Transmission Delay Store & Forward Delay Queueing Delay Node Processing Delay
70
Difference between Propagation Delay and Transmission Delay?
Prop Delay: Time for signal to travel over link. (len/speed) Trans Delay: Time to send entire packet. (packet size/bit rate)
71
What is Datagram packet switching
Datagram networks have packets of the same flow can follow different paths
72
What is virtual circuit packing switching
packets of the same flow must follow the same path (easier to control traffic loads on links within a network)
73
Two main components of a cellular network?
Radio Access Network (RAN): Base stations wirelessly communicating with devices Core Network (EPC): Forwards data traffic, manages authentication and mobiltiy sessions
74
Generations of cellular network evolution
1G: Analog voice, circuit switching 2G/3G: Digital Voice + packet-swtiched 4G/5G: All-IP packet switched services, high-speed, low latency
75
Goals for 5G networks?
Peak data rates up to 20 Gbps Mobility support up to 500km Radio Latency < 1ms Massiove IoT support

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