Q1. Assume six devices are arranged in a mesh topology. How many cables are
needed? How many ports are needed for each device?
Answer: Cables needed 15 and, Each device needs to be connected to 5 other devices. So, each device needs to have 5 ports. Six devices times five ports equals 30 total ports
.
Q2. We have two computers connected by an Ethernet hub at home. Is this a LAN or a WAN? Explain the reason?
Answer: Ethernet is used in a LAN and has a limit to the length of cable used. Wireless networking is also considered a LAN. Your connection to you ISP, however, would be considered part of a MAN. MAN - Metropolitan Area Network is used in cities and towns and uses fiber optics, coax cables, telephone wires (DSL), and, in some cases, wireless.
Q3. In the ring topology in Figure 1.7, what happens if one of the stations is
unplugged?
Answer: In a ring topology, unplugging one station interrupts the ring. However, most ring networks use a mechanism that bypasses the station; the ring can continue its operation.
Q4.Performance is inversely related to delay. When we use the Internet, which of following applications are more sensitive to delay?
A. Sending an e-mail B. Copying a file C. Surfing the Internet
Answer:
A. Sending An E-Mail: E mail is not an interactive application. Even if it is delivered immediately, it may stay in the mail-box of the receiver for a while. It is not sensitive to delay.
B. Copying A File: We normally do not expect a file to be copied immediately. It is not very sensitive to delay.
C. Surfing The Internet: Surfing the Internet is the application very sensitive to delay. We except to get access to the site we are searching.
Q5. Compare the telephone network and the Internet. What are the similarities? What are the differences?
Answer: The two networks are similar in the fact that both are made of interconnections of small network. The telephone network is mostly a circuit switched network; the Internet is mostly packet-switched network.
Q6.Answer the following questions about Figure 2.2 when the communication is from Maria to Ann:
a. What is the service provided by layer 1 to layer 2 at Maria’s site?
b. What is the service provided by layer 1 to layer 2 at Ann’s site?
Answer: a. Layer q pulls the cipher text from layer 2 an inserts it in an envelope before sending it.
b. Layer e encrypts or decrypts the cipher text to plain text and send it to layer 3 so they it could understand easily.
Q7. Assume that the number of hosts connected to the Internet at year 2010 is five hundred million. If the number of hosts increases only 20 percent per year, what is the number of hosts in year 2020?
Answer: 3096 million is the number of hosts in year 2020.
Q8. Assume a system uses five protocol layers. If the application program creates a message of 100 bytes and each layer (including the fifth and the first) adds a header of 10 bytes to the data unit, what is the efficiency (the ratio of application layer bytes to the number of bytes transmitted) of the system?
Answer: E = 100 / 150 = 66.7 %.
Q9. Assume we have created a packet-switched internet. Using the TCP/IP protocol suite, we need to transfer a huge file. What are the advantage and disadvantage of sending large packets?
Answer: The advantage is that the packet is routed along the fastest available route by routers that read the destination address and forwards each IP packet independently. The disadvantage is that larger packets take longer to transmit as they contain more data.
Q10. Match the following to one or more layers of the TCP/IP protocol suite:
a. creating user datagrams.
b. responsibility for handling frames between adjacent nodes.
c. transforming bits to electromagnetic signals.
Answer:
a. Transfer and network.
b. Data link.
c. Physical.
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