CS422: Fall2002 Midterm
Part 1. Answer True or False (T/F) (1 point each).
___ In digital encoding the amount of energy is proportional to the item sent.
___ Optical fibers ar succeptible to electromagnetic noise.
___ The RS232C standard uses asynchronous communication.
___ Low-Earth orbit satellites stay at the same point in the sky relative to the earth.
___ In RS232, a 0 is +15V.
___ By being digital, serial lines are immune to noise
___ In half duplex communication each end may both transmit and receive at different times.
___ In RS232 there is always one start and one stop bits in each byte that is sent correctly.
___ Information is modulated in oscillating signals to travel long distances.
___ Frequency modulation is more tolerant to noise than amplitud modulation.
___ Token ring uses time division multiplexing.
___ In frequency division multiplexing, two or more signals that use different carriers can be transmitted over the same medium without interference.
___ In RS232 it is full duplex communication requires two wires.
___ The shorter a packet is, the smaller the delay in the network.
___ With byte stuffing the size of a packet could potentially triple in length.
___ The 100Mbps Ethernet accomplishes this speed by having larger packets.
___ The ethernet type in the ethernet header indicates if the packet is UDP, TCP or ICMP.
___ Conectionless networks are more approriate to send real-time data.
___ Shanon's theorem will always give a more pessimistic limit in the throughput than Nyquist theorem.
___ An ATM cell uses 43 bytes for data.
Part2. Answer the following questions:
1. (3 pts.) Given the sequence of bytes 0101, 0110, 0010,
a) Give the checksum
b) Give a different sequence of bytes that give the same checksum
c) Add the parity bit X to the byte X1001010 assuming even parity.
2. (3 pts.) Explain what CSMA/CA means. Explain how the CA part works.
3. (3 pts.) Explain why CSMA/CD is not used in wireless LANs.
4. (3 pts.) When is inverse multiplexing used and how it works.
5. (3 pts.) Give the througput for the following circuit capacities: T1,
6.(3 pts.) Asusme that the delay in a network without traffic is .01sec. What is the delay if the network is being used at 20% of its capacity?
7. (3 pts.) Mention the reasons why the ATM technology was not successful in the Internet.
8. (3 pts.) Mention the differences between the distance vector and link-state
9. (3 pts.) Mention the differences between a PVC and a SVC.
10. (3 pts.) "Segment 1 List" and "Segment 2 List" are the lists of hosts
that the bridge knows ar in each segment. Write under each "segment list"
the name of the hosts after each event: (3 pts)
11. (25 pts) Write a client program that requests a file from a server
and prints it to standard output. The syntax of the command is the following:
getfile <host> <port> <file>Assume that the server expects the name of the file followed by <cr><lf> . The server will reply with the file. If the file does not exist the server will just close the connection. Try to be as detailed as possible.Feel free to continue writing your program in the back of the page. In the next question you will write the matching server
12. (25 pts) Write the server program that serves a request from the
client in question 11. The syntax of the server command is the following::
getfiled <port>Assume that the server expects the name of the file followed by <cr><lf> . The server will reply with the file. If the file does not exist the server will just close the connection. Try to be as detailed as possible. Make the server concurrent by using fork() in each request.