Cs2600 Networking Exam 2

Front 1

6 of the Largest foreign telecom carriers

Back 1

- Vodafone (UK)

- France Telecom

- China Mobile

- Telecom Italia

- Deutsche Telekom

- Telefonica (spain)

Front 2

Characteristics of DS1/T1 and DS3/T3 Circuits

Back 2

- Provide point-to-point (non-switched) digital data transfer over conditioned copper wiring

- DS1 links operate at 1.5Mbps

- DS3 service is 45Mbps

- Both require an interface device on both ends called a DSU/CSU (data service unit/channel service unit)

- Rates or Tarrifs based on distance

Front 3

Advantages of DS1/T1 and DS3/T3 Circuits

Back 3

- Economical for ongoing bulk transfer between fixed points

- Reliable, with accurate diagnostics

- widely available in U.S. cities

Front 4

Disadvantages of DS1/T1 and DS3/T3 Circuits

Back 4

- Point-to-Point circuit (not switched)

- Relatively high cost

Front 5

What is the bandwidth of Dial-up service?

Back 5

Which internet service has a bandwidth between 28-56kbps and is obsolete in the US?

Front 6

What is the bandwidth of ISDN service?

Back 6

Which internet service has a bandwidth between 64-128kbps and is mostly obsolete?

Front 7

What is the bandwidth of DSL?

Back 7

Which internet service has a bandwidth between 128kbps-100Mbps and is considered "broadband"?

Front 8

What is the bandwidth of CATV? (cable TV)

Back 8

Which internet service has a bandwidth between 1-40Mbps and is considered "broadband"?

Front 9

What is the bandwidth of FTTH?

(fiber to the home)

Back 9

Which internet service has a broadband between 50Mbps - 1Gbps and is considered "broadband"?

Front 10

What is Encoding?

Back 10

What is the process of converting digital data into a suitable format for communication over digital communication system?

Front 11

What is Modulation (shift keying)?

Back 11

What is the process of converting digital data in a form suitable for communication over an analog communication system?

Front 12

What does a modem do?

Back 12

What hardware will take bits out of memory and convert them into an analog signal using modulation or shift keying processes?

Front 13

What is a codec (coder-decoder)?

Back 13

What is the hardware for digital transmission and reception on a guided medium called?

Front 14

What does a codec do?

Back 14

What hardware takes bits out of memory and converts them into a digital signal using encoding?

Front 15

What are the three main examples of encoding strategies?

Back 15

NRZ, NRZI, and Manchester are all examples of what type of strategies?

Front 16

What do the following encoding strategies look like? (in order)

- NRZ

- NRZI

- Manchester

Back 16

What are the tree different encoding strategies used from top to bottom?

Front 17

What are the encoding rules for NRZ?

Back 17

Which encoding strategy follows these rules?

- Low level = 0

- High level = 1

Front 18

What are the encoding rules for NRZI?

Back 18

Which encoding strategy follows these rules?

- No level transition = 0;

- mid-bit level transition = 1;

Front 19

What are the encoding rules for Manchester?

Back 19

Which encoding strategy follows these rules?

- Mid-bit low-to-high transition = 0;

- Mid-bit high-to-low transition = 1;

Front 20

What does an Analog Carrier Signal look like?

Back 20

What kind of signal is this an example of?

Front 21

What does amplitude shift keying look like?

Back 21

This signal is an example of what?

Front 22

What does frequency shift keying look like?

Back 22

This signal is an example of what?

Front 23

What happens when a digital signal encounters noise?

Back 23

This picture gives an example on the effects of noise on what kind of signal?

Front 24

What factors influence Noise-Related Bit errors?

Back 24

-Distance from transmission medium noise to source

- Amplitude of signal, relative to the amplitude of the noise

- Type of signaling system used

- Type of noise

- Data rate

These are all examples of factors that influence what type of Bit Error?

Front 25

What is Crosstalk?

Back 25

When one channel or circuit "spills over" into another we call it?

Front 26

What is Impulse Noise?

Back 26

What type of noise consists of short, strong noise bursts or "spikes"?

Front 27

What are some major characteristics of crosstalk?

Back 27

The following are characteristics of what type of noise?

- Caused by leakage between different circuits in the same cable or overlapping radio or TV channels

- Fairly easy to predict and "design around"

Front 28

What are some major characteristics of Impulse Noise?

Back 28

The following are major characteristics of what kind of noise?

- Caused by anything that generates an electrical spark or arc.

- unpredictable

- not a big problem for analog voice networks

- major problem for data transmission

Front 29

What is the most significant noise problem in data communications?

Back 29

Besides being one of the most common causes of bit errors, what else is Impulse Noise known for?

Front 30

What are the best methods to suppress noise?

Back 30

The following are all great methods to do what?

- using shielded cables

- relocating cables

- using optical fibre

Front 31

Who is Claude Shannon?

Back 31

Who is "The Father of Information Theory"?

Front 32

What is the Shannon-Hartley Theorem?

Back 32

What theory does the following equation belong to?

C = B log2(1 + S/N)

Front 33

What does the Shannon-Hartley Theorem do?

Back 33

Which Theorem expresses the maximum theoretical data rate of a link, given a certain analog bandwidth and Signal to Noise Ratio?

Front 34

In the SHTheorem, What does the "C" represent?

Back 34

What symbol is used to represent the channel capacity (error-free data rate in bps) in the SHTheorem?

Front 35

In the SHTheorem, What does the "B" represent?

Back 35

What symbol is used to represent an analog (true) bandwidth range in Hz in the SHTheorem?

ex. (550MHz for CAT 6 UTP)

ex. if range == (3300Hz - 300Hz) = 3000Hz

Front 36

How do you get S/N ratio from dB to a fraction?

Back 36

In the SHTheorem you can get the ratio by converting from what in the following example?

dB = 10x log10(S/N) --> S/N = 10^(dB/10)

Front 37

How can you get Log2 of any number?

Back 37

What do you get if you divide Log10 N by Log10 2?

(Log10 N / Log10 2)

Front 38

What is the third principle of Network Design?

Back 38

"Packets are encapsulated within frames" is what?

Front 39

What are the first 3 problems associated with Framing?

Back 39

The following are problems associated with what?

- Design a frame format flexible enough to carry many types of data as a payload

- Determining where the frame begins and ends

- Identifying where various sections within the frame begin and end

Front 40

What does the BISYNC Frame Format look like?

Back 40

This is an example of what type of Frame Format?

Front 41

What does the PPP Frame Format look like?

(Point to Point Protocol)

Back 41

This is an example of what type of Frame Format?

Front 42

What does the HDLC Frame Format look like?

Back 42

This is an example of what type of Frame Format?

Front 43

What are some Bit-Oriented Synchronous Data-Link Layer Protocols?

Back 43

The following are all examples of what type of Data-Link Layer Protocols?

Immediate HDLC Family Members:

- HDLC: high level data link control (CCITT/ITU)

- PPP: Point to Point Protocol, TCP/IP serial Link

- Logical Link Control (IEEE 802.2)

Front 44

What are three main HDLC frame types?

Back 44

The following are frame types for what type of frame format?

- Information ("I") frames

- Supervisory frames

- Un-numbered frames

Front 45

What does an information frame do?

Back 45

Which HDLC frame carries data in the PAYLOAD field that follows the header?

Front 46

What does a supervisory frame do?

Back 46

Which HDLC frame does not carry data, and is used for flow control and error control after the connection has been established?

Front 47

What does an Un-numbered frame do?

Back 47

Which HDLC frame does not carry data, and are transmitted to establish and terminate connections, and handle server errors?

Front 48

What is Flow Control?

Back 48

What is the mechanism that allows the receiver to tell the sender to slow down?

Front 49

What is Error Control?

Back 49

What is the mechanism that the receiver uses to tell the sender that it received a bad frame?

Front 50

In an HDLC frame how does the sender indicate the start and end of a frame?

Back 50

What does an HDLC frame accomplish by transmitting the flag pattern (01111110)?

Front 51

In an HDLC frame, when the sender needs to send a pattern containing five or more 1-bits in a sequence as data, what happens?

Back 51

When does the sender's hardware stuff in a 0-bit, in HDLC frames?

Front 52

In HDLC frames, what happens when there are five consecutive 1-bits followed by a 0-bit?

Back 52

In HDLC, the bit is deleted, restoring the data pattern to its original form when what bit pattern occurs?

Front 53

In HDLC frames, what happens when there are six consecutive 1-bits followed by a 0-bit?

Back 53

In HDLC, a flag marks the beginning or end of a frame when what bit pattern occurs?

(flags are discarded after being received)

Front 54

In HDLC frames, what happens when there are six consecutive 1-bits followed by another 1-bit?

Back 54

In HDLC, an error has occurred and the entire frame is discarded when what bit pattern occurs?

Front 55

What is the main difference between HDLC and PPP frame format?

Back 55

What does this picture demonstrate?

Front 56

What are some major characteristics of error detection algorithms?

Back 56

- The strength of the algorithm (the probability of detecting the error)

- The transmission overhead (number of error detection code bits added to the message - typically 8, 16, or 32 bits)

- The processing overhead (amount of processing required to run it)

Front 57

What does an asynchronous frame look like?

Back 57

What type of frame does this diagram show?

Front 58

What is one dimensional parity?

(simple parity)

Back 58

What type of error detection will calculate the number of 1-bits in a set of data bits to make an even number of 1-bits.

Front 59

What does one dimensional parity look like?

Back 59

This diagram is an example of what?

Front 60

What does two dimensional parity look like?

Back 60

This diagram is an example of what?

Front 61

How does the internet checksum algorithm catch for an error?

Back 61

Which error detection algorithm uses one's complement addition?

Front 62

What makes the CRC Algorithm reliable?

Back 62

The following are examples of the reliability of what algorithm?

- detects all single bit errors

- detects all double bit errors

- detects all odd number of bit errors

- detects all error bursts less than R*

*R = number of bits in the chosen polynomial.

Front 63

Common CRC Polynomials:

Back 63

Front 64

In other nations who provides data services? and what are they called?

Back 64

PTT's or (post telephone and telegraph) is used where, to provide data services?

Front 65

What is SONET? (Synchronous Optical Network)

Back 65

What is the fiber optic network standard called?

Front 66

What is ISDN?

(integrated services digital network)

Back 66

What was developed back in the 1980's to be the worldwide digital replacement for analog dial-up phone circuits?

Front 67

What is a quartz crystal oscillator "Clock"?

Back 67

What is used to synchronize with the sender when the transmission begins?

Front 68

How does a clock synchronize?

Back 68

What happens when the receiver clock checks the edge of a state change to determine where the next clock interval begins?

Front 69

What is a clock drift?

Back 69

What happens when there are almost no state changes in a sequence?

ex. in NRZ a long sequence of zeroes.

Front 70

What is the baud rate?

Back 70

What is the maximum rate per second that a transmission system can change states?

Front 71

What is 4B/5B encoding?

Back 71

Which encoding method takes the data and separates it into 4bit segments then translates them into corresponding 5bit segments, and then uses NRZI encoding?

Front 72

What is DSL?

(Digital Subsciber Line)

Back 72

What is the second most popular method for residential broadband internet access?

Front 73

What are some characteristics of DSL?

Back 73

The following are some characteristics of what?

- Runs on a single copper pair over existing analog phone network local loop

- Provides

Front 74

What is an ACK?

(Acknowledgement)

Back 74

The following describes what?

- Feedback from the receiver to the sender that says "I have received the message correctly"

- Implies that the sender can discard the copy of the message that it was holding for possible retransmission

Front 75

What is a NAK?

(Negative Acknowledgment)

Back 75

The following describes what?

- Feedback from the receiver to the sender that says "I received a frame with errors"

- Feedback that may also say "I am missing a frame that was supposed to be sent"

Front 76

What is the fourth principle of Network Design?

Back 76

The Phrase: "No undetected duplicate frames" is what?

Front 77

What limits stop and wait time?

Back 77

The fact that stop and wait time transmits a maximum of one frame per round trip time causes what?

Front 78

When is stop and wait time wasteful?

Back 78

What happens to stop and wait time when the volume of the pipe is larger than the size of a typical frame?

Front 79

What affects stop and wait time?

Back 79

The following do what?

- having a bigger pipe, longer distance, or higher data rate

- sending a small message

Front 80

What is the fifth principle of network design?

Back 80

The following saying is what?

"In general, stop and wait ARQ works better on LANs than it does on WANs"

(there are exceptions)

Front 81

What is SeqNum?

Back 81

What is the frame number?

(must be one greater than the number of previous frame)

Front 82

What is SWS?

(send window size)

Back 82

What is the maximum number of unacknowledged frames that can be transmitted?

(a constant in data link protocols)