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computer networking
Questions and Answers of
Computer Networking
Assume we change the Stop-and-Wait Protocol to include a NAK (negative feedback), which is used only when a corrupted frame arrives and is discarded. Redraw Figure 11.9 to show this change.Figure
Compare and contrast byte-stuffing and bit-stuffing.
Unstuff the following frame payload: 00011111000001111101110100111011111000001111
Compare and contrast byte-oriented and bit-oriented protocols.
Bit-stuff the following frame payload: 00011111110011111010001111 111110000111
Assume a new character-oriented protocol is using the 16-bit Unicode as the character set. What should the size of the flag be in this protocol?
Unstuff the following frame payload in which E is the escape byte, F is the flag byte, and D is a data byte other than an escape or a flag character. D DEF E D DD DE E
Explain why flags are needed when we use variable-size frames.
Byte-stuff the following frame payload in which E is the escape byte, F is the flag byte, and D is a data byte other than an escape or a flag character. DEDDF D D E|ED F|D
Define framing and give the reason it is needed.
Figure 9.7 shows a system as either a host or a router. What would be the actual entity (host or router) of system A and B in each of the following cases:Figure 9.7a. If the link is the first one in
How many IP addresses and how many link-layer addresses should a router have when it is connected to five links?
Assume the network in Figure 9.7 does not support broadcasting. What do you suggest for sending the ARP request in this network?Figure 9.7 LAN System A System B N, L, N, L2 Request N3L3 N, L4
Why does a router normally have more than one interface?
In Figure 9.7, assume system B is not running the ARP program. What would happen?Figure 9.7 LAN System A System B N, L, N, L2 Request N3L3 N, L4 Request: Looking for link-layer address of a node with
Why does a host or a router need to run the ARP program all of the time in the background?
In Figure 9.5, assume Link 2 is broken. How can Alice communicate with Bob?Figure 9.5 To another link N3 L3 Frame Alice L2 L, NNg Data N, L, RI N4 L4 N¡ L Link 1 Order of addresses N: IP
In Figure 9.9, how does system A know what the link-layer address of system B is when it receives the ARP reply?Figure 9.9 System A System B N2 N1 L1 L2 (Not known by A) Ox0001 Ox04 Ox0800 Ох06
When we send a letter using the services provided by the post office, do we use an end-to-end address? Does the post office necessarily use an end-to-end address to deliver the mail? Explain.
In Figure 9.9, why is the destination hardware address of the frame from A to B a broadcast address?Figure 9.9 System A System B N2 N1 L1 L2 (Not known by A) Ox0001 Ox04 Ox0800 Ох06 Ox0001 ARP
In the previous problem, assume Alice cannot find a direct flight from the Los Angeles to the Chicago. If she needs to change flights in Denver,a. Find the end-to-end addresses in this scenario.b.
In Figure 9.9, why is the destination hardware address all 0s in the ARP request message?Figure 9.9 System A System B N2 N1 L1 L2 (Not known by A) Ox0001 Ox04 Ox0800 Ох06 Ox0001 ARP request L1 N1
Assume Alice is travelling from 2020 Main Street in Los Angeles to 1432 American Boulevard in Chicago. If she is travelling by air from Los Angeles Airport to Chicago Airport,a. find the end-to-end
Assume we have an isolated link (not connected to any other link) such as a private network in a company. Do we still need addresses in both the network layer and the data-link layer? Explain.
Is the current Internet using circuit-switching or packet-switching at the datalink layer? Explain.
What is the size of an ARP packet when the protocol is IPv4 and the hardware is Ethernet?
Explain why we may need a router in Figure 9.16. Bob Alice R Alice's site Bob's site
Is the size of the ARP packet fixed? Explain.
Explain why we do not need the router in Figure 9.15.
Can two hosts in two different networks have the same link-layer address? Explain.
Distinguish between a point-to-point link and a broadcast link.
Distinguish between communication at the network layer and communication at the data-link layer.
When we say that the transport layer multiplexes and demultiplexes applicationlayer messages, do we mean that a transport-layer protocol can combine several messages from the application layer in one
The presentation of data is becoming more and more important in todays Internet. Some people argue that the TCP/IP protocol suite needs to add a new layer to take care of the presentation
Can you explain why we did not mention multiplexing/demultiplexing services for the application layer?
Assume we want to connect two isolated hosts together to let each host communicate with the other. Do we need a link-layer switch between the two? Explain.
If there is a single path between the source host and the destination host, do we need a router between the two hosts?
What is the relationship between period and frequency?
What does the amplitude of a signal measure? What does the frequency of a signal measure? What does the phase of a signal measure?
Given the following periods, calculate the corresponding frequencies.a. 5 sb. 12 μsc. 220 ns
How can a composite signal be decomposed into its individual frequencies?
What is the phase shift for the following?a. A sine wave with the maximum amplitude at time zerob. A sine wave with maximum amplitude after 1/4 cyclec. A sine wave with zero amplitude after 3/4 cycle
Name three types of transmission impairment.
What is the bandwidth of a signal that can be decomposed into five sine waves with frequencies at 0, 20, 50, 100, and 200 Hz? All peak amplitudes are the same. Draw the bandwidth.
Distinguish between baseband transmission and broadband transmission.
A periodic composite signal with a bandwidth of 2000 Hz is composed of two sine waves. The first one has a frequency of 100 Hz with a maximum amplitude of 20 V; the second one has a maximum amplitude
Distinguish between a low-pass channel and a band-pass channel.
Which signal has a wider bandwidth, a sine wave with a frequency of 100 Hz or a sine wave with a frequency of 200 Hz?
What does the Nyquist theorem have to do with communications?
What is the bit rate for each of the following signals?a. A signal in which 1 bit lasts 0.001 s.b. A signal in which 1 bit lasts 2 ms.c. A signal in which 10 bits last 20 μs.
What does the Shannon capacity have to do with communications?
A device is sending out data at the rate of 1000 bps.a. How long does it take to send out 10 bits?b. How long does it take to send out a single character (8 bits)?c. How long does it take to send a
Why do optical signals used in fiber optic cables have a very short wave length?
What is the bit rate for the signal inFigure 3.35? 16 ns Time
Can we say whether a signal is periodic or nonperiodic by just looking at its frequency domain plot? How?
What is the frequency of the signal inFigure 3.36? 4 ms Time
What is the bandwidth of the composite signal shown inFigure 3.37? Frequency 180 5 5 5 5
Is the frequency domain plot of an alarm system discrete or continuous?
A periodic composite signal contains frequencies from 10 to 30 KHz, each with an amplitude of 10 V. Draw the frequency spectrum.
We send a voice signal from a microphone to a recorder. Is this baseband or broadband transmission?
A nonperiodic composite signal contains frequencies from 10 to 30 KHz. The peak amplitude is 10 V for the lowest and the highest signals and is 30 V for the 20-KHz signal. Assuming that the
We send a digital signal from one station on a LAN to another station. Is this baseband or broadband transmission?
A TV channel has a bandwidth of 6 MHz. If we send a digital signal using one channel, what are the data rates if we use one harmonic, three harmonics, and five harmonics?
We modulate several voice signals and send them through the air. Is this baseband or broadband transmission?
A signal travels from point A to point B. At point A, the signal power is 100 W. At point B, the power is 90 W. What is the attenuation in decibels?
The attenuation of a signal is −10 dB. What is the final signal power if it was originally 5 W?
A signal has passed through three cascaded amplifiers, each with a 4 dB gain. What is the total gain? How much is the signal amplified?
A line has a signal-to-noise ratio of 1000 and a bandwidth of 4000 KHz. What is the maximum data rate supported by this line?
We measure the performance of a telephone line (4 KHz of bandwidth). When the signal is 10 V, the noise is 5 mV. What is the maximum data rate supported by this telephone line?
A file contains 2 million bytes. How long does it take to download this file using a 56-Kbps channel? 1-Mbps channel?
A computer monitor has a resolution of 1200 by 1000 pixels. If each pixel uses 1024 colors, how many bits are needed to send the complete contents of a screen?
A signal with 200 milliwatts power passes through 10 devices, each with an average noise of 2 microwatts. What is the SNR? What is the SNRdB?
If the peak voltage value of a signal is 20 times the peak voltage value of the noise, what is the SNR? What is the SNRdB?
What is the theoretical capacity of a channel in each of the following cases?a. Bandwidth: 20 KHz SNRdB = 40b. Bandwidth: 200 KHz SNRdB = 4c. Bandwidth: 1 MHz SNRdB = 20
We need to upgrade a channel to a higher bandwidth. Answer the following questions:a. How is the rate improved if we double the bandwidth?b. How is the rate improved if we double the SNR?
We have a channel with 4 KHz bandwidth. If we want to send data at 100 Kbps, what is the minimum SNRdB? What is the SNR?
What is the transmission time of a packet sent by a station if the length of the packet is 1 million bytes and the bandwidth of the channel is 200 Kbps?
What is the length of a bit in a channel with a propagation speed of 2 × 108 m/s if the channel bandwidth isa. 1 Mbps?b. 10 Mbps?c. 100 Mbps?
How many bits can fit on a link with a 2 ms delay if the bandwidth of the link isa. 1 Mbps?b. 10 Mbps?c. 100 Mbps?
What is the total delay (latency) for a frame of size 5 million bits that is being sent on a link with 10 routers each having a queuing time of 2 μs and a processing time of 1 μs. The length of the
Calculate the value of the signal rate for each case in Figure 4.2 if the data rate is 1 Mbps and c = 1/2.Figure 4.2a. One data element per one signal element (r = 1)b. One data element per two
Distinguish between a signal element and a data element.
In a digital transmission, the sender clock is 0.2 percent faster than the receiver clock. How many extra bits per second does the sender send if the data rate is 1 Mbps?
Distinguish between data rate and signal rate.
Draw the graph of the NRZ-L scheme using each of the following data streams, assuming that the last signal level has been positive. From the graphs, guess the bandwidth for this scheme using the
Define baseline wandering and its effect on digital transmission.
Define a DC component and its effect on digital transmission.
Define the characteristics of a self-synchronizing signal.
Repeat Problem P4-3 for the 2B1Q scheme, but use the following data streams.a. 0000000000000000b. 1111111111111111c. 0101010101010101d. 0011001100110011Problem 4-3Draw the graph of the NRZ-L scheme
Repeat Problem P4-3 for the MLT-3 scheme, but use the following data streams.a. 00000000b. 11111111c. 01010101d. 00011000Problem 4-3Draw the graph of the NRZ-L scheme using each of the following data
Find the 8-bit data stream for each case depicted in Figure 4.36. Time a. NRZ-I Time b. differential Manchester
An NRZ-I signal has a data rate of 100 Kbps. Using Figure 4.6, calculate the value of the normalized energy (P) for frequencies at 0 Hz, 50 KHz, and 100 KHz.Figure 4.6 10 | 0 | 1 0 | r = 1 Save = N/2
A Manchester signal has a data rate of 100 Kbps. Using Figure 4.8, calculate the value of the normalized energy (P) for frequencies at 0 Hz, 50 KHz, 100 KHz.Figure 4.8 O is L 1 is 1 Save = N ave 2
The input stream to a 4B/5B block encoder is0100 0000 0000 0000 0000 0001Answer the following questions:a. What is the output stream?b. What is the length of the longest consecutive sequence of 0s in
What is the result of scrambling the sequence 11100000000000 using each of the following scrambling techniques? Assume that the last non-zero signal level has been positive.a. B8ZSb. HDB3 (The number
What is the Nyquist sampling rate for each of the following signals?a. A low-pass signal with bandwidth of 200 KHz?b. A band-pass signal with bandwidth of 200 KHz if the lowest frequency is 100 KHz?
What is the maximum data rate of a channel with a bandwidth of 200 KHz if we use four levels of digital signaling.
We have a baseband channel with a 1-MHz bandwidth. What is the data rate for this channel if we use each of the following line coding schemes?a. NRZ-Lb. Manchesterc. MLT-3d. 2B1Q
Which of the four digital-to-analog conversion techniques (ASK, FSK, PSK or QAM) is the most susceptible to noise? Defend your answer.
What is the position of the transmission media in the OSI or the Internet model?
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