Midterm Exam of ECE453 – Computer Networks
10/8/2008, Fall Semester
Your name (please print): ______________________
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Computer Networks - Midterm Examination | ECE 453, Exams of Computer Systems Networking and Telecommunications
Material Type: Exam; Class: Introduction to Computer Networks; Subject: Electrical And Computer Engr; University: University of Tennessee - Knoxville; Term: Fall 2008;
Typology: Exams
Pre 2010
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Midterm Exam of ECE453 – Computer Networks
10/8/2008, Fall Semester
Your name (please print): ______________________
A. Multiple-choice (50 points, 2 points each, there is only one correct answer):
Which of the following is a local area network (LAN)? ( ) A. Ethernet B. Internet C. WiMAX D. 3G cellular networks
How many layers do TCP/IP model have? ( ) A. 7 B. 5 C. 3 D. dynamic
Which layer in ISO concerns only logic transmission? ( ) A. Physical layer B. Network layer C. Transport layer D. Data link layer
What is the difference between message switching and packet switching? ( ) A. Message switching uses TCP protocol while packet switching is for UDP B. Message switching involves only logical communications while packet switching involves more C. Message switching keeps the integrity of the message while packet switching does not D. Message switching uses a dedicated connection while packet switching does not
What is FEC? ( ) A. Forward Error Correction B. Forward Error Connection C. False Event Correction D. Full Error Correction
How many errors can Hamming code correct? ( ) A. 0 B. 1 C. 2 D. 3
Why ADSL allocates more bandwidth to downstream ( ) A. Downstream has higher speed B. The data requirement of downstream is more C. Control packets are transmitted in downstream D. Many users have to share the same downstream
In Go-Back-N protocol, if the sender receivers ACK for packet 3 but fails in transmitting packet 2 (packet 3 is after packet 2), what will it do? ( ) A resend packets 2 and 3 B resend only packet 2 C go ahead to send packet 4 D send a NACK to the receiver
What is the maximum number of bit errors that a code with dmin = can detect? ( ) A 1 B 2
C 3
D 4
What does a CSMA transmitter do when it has data to transmit? ( ) A. sense the channel to see if it is busy B. send out an RTS to all other transmitters C. send out the data immediately D. broadcast ‘ALOHA’ to all other transmitters
Which is a feature of Aloha? ( ) A. sense the channel before transmitting B. if finding the channel is idle, transmits C. if finding the channel is busy, waits for a random period of time and repeats sensing D. if a collision happens, waits for a random period of time and start over again
Metcalfe ate his words with ( )
A. (syrup) B. (dumping)
C. (T-bone) D. (cake)
- Which of the following does not provide traffic isolation? ( ) A. router B. hub C. bridge D. switch
In ARP (address resolution protocol), what does node A do first if it wants to get physical address of node B if node B’s IP address is known? ( ) A. check nearest router’s routing table B. send a unicast packet to node B to ask for the physical address C. check its ARP table D. broadcast an ARP packet
Which one is a feature of IPv6, different from IPv4? ( ) A. more fragmentation B. 128 bit IP address C. variable length header D. a field of ‘More Fragments’ (MF)
Which of the following is not a type of congestion control in networks layer? A. Load shedding B. Choke packets C. Admission control D. Exponential transmission window
B. Physical Layer (10 points)
- Suppose that, in a communication system with 4MHz bandwidth, there is no noise. Then, what is the maximum transmission rate if using a QPSK symbol? (5 points)
- If signal-to-noise ratio (SNR) is 10dB. Then, what is maximum reliable transmission rate (suppose the bandwidth is 1MHz)? (5 points)
D. MAC Sublayer (10 points)
Explain how pure Aloha and slotted Aloha work (10 points for undergraduate students and 5 points for graduate students)
Provide a quantified analysis for the performance of pure Aloha and slotted Aloha (5 points for graduate students; undergraduate students need not answer it)
E. Network Layer I: QoS (10 points)
Suppose a token bucket has capability of 100kB and its maximum output rate is 25Mbps; the token arrival rate is 2Mbps. A data burst arrives with rate 50Mbps and duration 20ms. Please plot the traffic shape at the token bucket from 0ms to 500ms.
Under: 86.0000 (max) 64.1250 (mean) 62.0000 (median)
Grad: 90.0000 (max) 75.4615 (mean) 78.0000 (median)