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Which of the four digital-to-analog conversion techniques (ASK, FSK, PSK or QAM) is the most susceptible to noise? Defend your answer. Define baseline wandering and its effect on digital transmission. 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 a signal element and a data element. We have a channel with 4 KHz bandwidth. If we want to send data at 100 Kbps, what is the minimum SNR dB ? What is the SNR? 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? We modulate several voice signals and send them through the air. Is this baseband or broadband transmission? We send a voice signal from a microphone to a recorder. Is this baseband or broadband transmission? What is the bandwidth of the composite signal shown in Figure 3.37? Frequency 180 5 5 5 5 Why do optical signals used in fiber optic cables have a very short wave length? 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... 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? Distinguish between baseband transmission and broadband transmission. How can a composite signal be decomposed into its individual frequencies? What is the relationship between period and frequency? 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. Can you explain why we did not mention multiplexing/demultiplexing services for the application 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... How many IP addresses and how many link-layer addresses should a router have when it is connected to five links? In a byte-oriented protocol, should we first unstuff the extra bytes and then remove the flags or reverse the process? In Example 11.4 (Figure 11.13), assume the round trip time for a frame is 40 milliseconds. Explain what will happen if we set the time-out in each of the following cases. Figure 11.13 a. 35... In Figure 11.11, show what happens in each of the following cases: Figure 11.11 a. The receiver is in the ready state and a packet comes from the network layer. b. The receiver is in the ready state... Compare the flag byte and the escape byte in PPP. Are they are the same? Explain. In the previous problem, we found the probability of success for a station to send a frame successfully during the vulnerable time. The throughput of a network with a limited number of stations is... In a bus CSMA/CD network with a data rate of 10 Mbps, a collision occurs 20 s after the first bit of the frame leaves the sending station. What should the length of the frame be so that the sender... Assume the propagation delay in a broadcast network is 5 s and the frame transmission time is 10 s. a. How long does it take for the first bit to reach the destination? b. How long does it take for... To understand why we need to have a minimum frame size T fr = 2 T p in a CDMA/CD network, assume we have a bus network with only two stations, A and B, in which T fr = 40 s and T p = 25 s. Station A... Manually simulate the Adler algorithm (Figure 10.19) to calculate the checksum of the following words: (FBFF) 16 and (EFAA) 16 . Also show that the result is a weighted checksum. Figure 10.19 Start... Show how the Adler algorithm (Figure 10.19) attaches weights to the data items when calculating the checksum. Figure 10.19 Start Notes L: Left 16-bit checksum R: Right 16-bit checksum D;: Next 16-bit... Given the dataword 101001111 and the divisor 10111, show the generation of the CRC codeword at the sender site (using binary division). In CRC, if the dataword is 5 bits and the codeword is 8 bits, how many 0s need to be added to the dataword to make the dividend? What is the size of the remainder? What is the size of the divisor? Equation 1.1 gives a formula for the end-to-end delay of sending one packet of length L over N links of transmission rate R. Generalize this formula for sending P such packets back-to-back over the N... Consider Figure 1.19(a). Assume that we know the bottleneck link along the path from the server to the client is the first link with rate R s bits/sec. Suppose we send a pair of packets back to back... Recall the simple model for HTTP streaming shown in Figure 9.3. Recall that B denotes the size of the client's application buffer, and Q denotes the number of bits that must be buffered before the... Suppose now that the leftmost router in Figure 6.33 is replaced by a switch. Hosts A, B, C, and D and the right router are all star-connected into this switch. Give the source and destination MAC... Pl. Consider the network below. a. Show the forwarding table in router A, such that all traffic destined to host H3 is forwarded through interface 3. b. Can you write down a forwarding table in... Is an oil pipeline a simplex system, a half-duplex system, a full-duplex system, or none of the above? What about a river or a walkie-talkie-style communication? Consider the throughput example corresponding to Figure 1.20(b). Now suppose that there are M client-server pairs rather than 10. Denote R s , R c , and R for the rates of the server links, client... A modem constellation diagram similar to Fig. 2-23 has data points at the following coordinates: (1, 1), (1, 1), (1, 1), and (1, 1). How many bps can a modem with these parameters achieve at 1200... In Fig. 2-40, the user data rate for OC-3 is stated to be 148.608 Mbps. Show how this number can be derived from the SONET OC-3 parameters. What will be the gross, SPE, and user data rates of an... What is the length of a contention slot in CSMA/CD for (a) A 2-km twin-lead cable (signal propagation speed is 82% of the signal propagation speed in vacuum)?, (b) A 40-km multi mode fiber optic... Describe two major differences between the ECN method and the RED method of congestion avoidance. While IP addresses are tried to specific networks, Ethernet addresses are not. Can you think of a good reason why they are not? Two users can establish a shared secret key using the Diffie-Hellman algorithm, even if they have never met, share no secrets, and have no certificates (a) Explain how this algorithm is susceptible... Consider a 50,000-customer video server, where each customer watches three movies per month. Two-thirds of the movies are served at 9 P.M. How many movies does the server have to transmit at once... A binary file is 4560 bytes long. How long will it be if encoded using base 64 encoding, with a CR+LF pair inserted after every 110 bytes sent and at the end? When a resident uses a dial-up or DLS service to connect to the Internet, what is the role of the telephone company? Five equal-size datagrams belonging to the same message leave for the destination one after another. However, they travel through different paths as shown in Table 8.1. We assume that the delay for... Why is there no need for CSMA/CD on a full-duplex Ethernet LAN? What are the three major components of a telephone network? What is LATA? What are intra-LATA and inter-LATA services? Describe the SS7 service and its relation to the telephone network. What is dial-up modem technology? List some of the common modem standards discussed in this chapter and give their data rates. What is DSL technology? What are the services provided by the telephone companies using DSL? Distinguish between a DSL modem and a DSLAM. Compare and contrast a traditional cable network with a hybrid fiber-coaxial network. Why is SNR in a wireless LAN normally lower than SNR in a wired LAN? What are some reasons that CSMA/CD cannot be used in a wireless LAN? Explain why we have only one frame type in a wired LAN, but four frame types in a wireless LAN. An AP may connect a wireless network to a wired network. Does the AP need to have two MAC addresses in this case? Can a piconet have more than eight stations? Explain. What is the spread spectrum technique used by Bluetooth? What MAC protocol is used in the baseband layer of Bluetooth? Draw a cell pattern with a frequency-reuse factor of 3. Use Keplers law to check the accuracy of a given period and altitude for an Iridium satellite. Why is routing the responsibility of the network layer? In other words, why cant the routing be done at the transport layer or the data-link layer? Find the class of the following classful IP addresses: a. 01110111 11110011 10000111 11011101 b. 11101111 11000000 11110000 00011101 c. 11011111 10110000 00011111 01011101 Explain how DHCP can be used when the size of the block assigned to an organization is less than the number of hosts in the organization. In an IPv4 datagram, the value of the header-length (HLEN) field is (6) 16 . How many bytes of options have been added to the packet? Create a foreign agent advertisement message using 1672 as the sequence number and a lifetime of 4 hours. Select your own values for the bits in the code field. Use at least three care-of addresses... Explain why policy routing can be implemented on an interdomain routing, but it cannot be implemented on a intradomain routing. Explain why we can have different intradomain routing protocols in different ASs, but we need only one interdomain routing protocol in the whole Internet. In Figure 20.24, assume that the intra-AS routing protocol used by AS4 and AS3 is RIP. Explain how R8 can find how to route a packet to N13. Figure 20.24 A sample internet with four ASs N13 ASI N7 N8... In Figure 20.24, assume that the intra-AS routing protocol used by AS1 is OSPF, but the one used by AS2 is RIP. Explain how R5 can find how to route a packet to N4. Figure 20.24 A sample internet... In computer science, when we encounter an algorithm, we often need to ask about the complexity of that algorithm (how many computations we need to do). To find the complexity of the distance vectors... Explain the concept of hop count in RIP. Can you explain why no hop is counted between N1 and R1 in Figure 20.15? Figure 20.15 Hop counts in RIP NI N2 N3 N4 Source Destination RI R2 R3 1 hop (N4) 2... In a graph, if we know that the shortest path from node A to node G is (A B E G), what is the shortest path from node G to node A? When we send an e-mail to multiple recipients, are we are using multicasting or multiple unicasting? Give the reason for your answer. A multicast address for a group is 232.24.60.9. What is its 48-bit Ethernet address for a LAN using TCP/IP? Change the following IP multicast addresses to Ethernet multicast addresses. How many of them specify the same Ethernet address? a. 224.18.72.8 b. 235.18.72.8 c. 237.18.6.88 d. 224.88.12.8 Can a host have more than one multicast address? Explain. It is obvious that we need to have spanning trees for both unicasting and multicasting. How many leaves of the tree are involved in a transmission in each case? a. A unicast transmission b. A... Assume we have 20 hosts in a small AS. There are only four groups in this AS. Find the number of spanning trees in each of the following approaches: a. Source-based tree b. Group-shared tree In the network of Figure 21.17, find the shortest path trees for router R if the network is using MOSPF with the source connected to the router marked as S. Assume that all routers have interest in... Does RPF actually create a shortest path tree? Explain. Explain the advantages of IPv6 when compared to IPv4. Explain the use of the flow field in IPv6. What is the potential application of this field? List three protocols in the IPv4 network layer that are combined into a single protocol in IPv6. What is the purpose of including the IP header and the first 8 bytes of datagram data in the error-reporting ICMP messages? If you are assigned an IPv6 address by your ISP for your personal computer at home, what should be the first (leftmost) three bits of this address? Write a program to simulate the sending-site FSMs for the Go-Back-N protocol (Figure 23.27). Write a program to simulate the sending-site FSMs for the Selective Repeat protocol (Figure 23.34). Figure 23.34 FSMS for SR protocol Sender Time-out. Resend all outstanding packets in window. Reset... In a network with fixed value for m > 1, we can either use the Go-Back-N or the Selective-Repeat protocol. Describe the advantage and the disadvantage of using each. What other network criteria... In the Selective-Repeat protocol, the size of the send and receive windows is the same. Does this mean that there are supposed to be no packets in transit? Assume we need to design a Selective-Repeat sliding window protocol for a network in which the bandwidth is 1 Gbps and the average distance between the sender and receiver is 5,000 km. Assume the... Answer the following questions: a. What is the minimum size of a UDP user datagram? b. What is the maximum size of a UDP user datagram? c. What is the minimum size of the application-layer payload... The control field in a TCP segment is 6 bits. We can have 64 different combinations of bits. List some combinations that you think are normally used. In TCP, does a SYN segment open a connection in only one direction or in both directions? In TCP, does a FIN segment close a connection in only one direction or in both directions? Distinguish between a time-out event and the threeduplicate-ACKs event. Which one is a stronger sign of congestion in the network? Why? Can you mention some tasks that can be done by one or a combination of TCP segments?
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