Section A : Basic Concepts (30 Marks)
1.A digital signal has a bit interval of 40 microseconds. What is the bit rate?
(a) 25 Kbps (b) 30 Kbps (c) 25 bps (d) 30 bps (e) 25 Mbps.
2.Which one of the following is a balanced interface?
(a) RS-232C (b) RS-423 (c) RS-449 (d) RS-422 (e) RS-433.
3.The sampling interval of a telephone voice signal is _____
(a) 125 Micro sec (b) 25 Micro sec (c) 50 Micro sec (d) 100 Micro sec (e) 200 Micro sec.
4.Packet generation in ALHOA network follows
(a) Poisson distribution (b) Gaussian distribution (c) Normal distribution (d) Abnormal distribution (e) Exponential distribution.
5.Attenuation in an optical fiber can be as small as _____________.
(a) 1 dB/km (b) 3.4 dB/km (c) 8 dB/km (d) 20 dB/km (e) 3.5 dB/km.
6.Quantization is the process of _______________.
(a) Assignment of frequences to values
(b) Assignment of applitudes to range of values
(c) Assignment of a specific range of values to signal phases
(d) Assignment of a specific range of values to signal amplitudes
(e) Assignment of phases to values.
7.What sampling rate is needed for a signal with a bandwidth of 10,000 Hz (1,000 to 11,000 Hz)?
(a) 20,000 samples/s (b) 22,000 samples/s (c) 21,000 samples/s (d) 19,000 samples/s(e) 23,000 samples/s.
8.A graded-index fiber has which of the following advantage over a step-index fiber?
(a) Lower attenuation (b) Lower dispersion (c) Lower cost (d) Easier to manufacture(e) Lower expansion.
9.What are the limitations of unipolar encoding technique?
(a) AC component (b) DC component (c) Synchronization (d) Bandwith (e) Both (b) and (c) above.
10.A digital signal has a bit rate of 2000 bps. What is the duration of each bit?
(a) 200 Micro seconds(b) 600 Micro seconds(c) 500 Micro seconds(d) 700 Micro seconds(e) 800 Micro seconds.
11. In Go-back-N ARQ, if frames 4, 5 and 6 are received successfully, the receiver may send an ACK _____ to the sender.
(a) 6 (b) 7 (c) 5 (d) 4 (e) 9.
12. For stop-and-wait flow control, for n data packets sent, ______ acknowledgments are needed.
(a) 2n (b) n (c) n+1 (d) n – 1 (e) 2n+1.
13. Which mutiplexing technique involves signals composed of light beams?
(a) FDM (b) Synchronous TDM (c) Asynchronous TDM (d) WDM (e) SDM.
14. Which type of telephone service is least expensive?
(a) Analog switched line (b) Analog leased line (c) Switched/56 service (d) DDS service (e) ISDN service.
15. Deliberate violations of alternate mark inversion are used in what type of digital-to-digital encoding?
(a) AMI (b) NRZ (c) Manchester (d) HDB3 (e) RZ.
16. _________ is the access protocol used by traditional Ethernet.
(a) CSMA (b) CSMA/CD (c) CSMA/CA (d) Token ring (e) Token bus.
17. What fields in the MAC frame of FDDI are variable length?
(a) Preambles (b) Address fields (c) Data fields (d) Both (b) and (c) above (e) All (a), (b) and (c) above.
18. In Token Ring, when a frame reaches its destination station, which of the following occurs?
(a) The message is copied
(b) Four bits in the packet are changed
(c) The message is taken off the ring and replaced by the token
(d) The message is not copied
(e) The message is sent back.
19. A wireless LAN uses __________frames for the initial communication between stations and the access points.
(a) Management (b) Control (c) Data (d) Acknowledgement (e) Parity.
20. _________ is a Frame Relay option that transmits voice through the network.
(a) LMI (b) VOFR (c) FRAD (d) DLCI (e) VFOR.
21. Which layer in ATM protocol has a 53-byte cell as an end product?.
(a) Physical (b) Application adaptation (c) ATM (d) Cell transformation (e) Logical.
22. In which of the following layer, Frame Relay can operate?
(a) Physical Layer
(b) Data Link Layer
(c) Physical and Network layer
(d) Datalink and Network layer
(e) Data link and Physical layer.
23. Which of the following ISDN plane is associated with signaling and the D channel?
(a) User (b) Control (c) Supervisory (d) Management (e) Virtual. 24. The ______channel in ISDN is used for applications requiring a transmission rate greater the 64 Kbps.
(a) B (b) C (c) D (d) E (e) H.
25. What type of Bridge builds and updates its tables from address information on packets?
(a) Transparent (b) Simple (c) Multiport (d) Complex (e) Transient.
26. HTTP has similarities to both _________and __________.
(a) FTP; SNMP (b) FTP; TELNET (c) FTP; POP (d) FTP; DHCP (e) FTP; SMTP.
27. A network using the CSMA random-access method with p equal to 0.25 will send ________percent of the time after accessing an idle line.
(a) 30 (b) 50 (c) 25 (d) 75 (e) 100.
28. IP is responsible for __________________communication while TCP is responsible for ________communication.
(a) Process-to-Process; Host-to-Host
(b) Node-to-Node; Process-to-Process
(c) Process-to-Process; Node-to-Node
(d) Host-to-Host; Process-to-Process
(e) Node-to-Node; Host-to-Host.
29. Which of the following protocol provides temporary IP addresses for a limited period of time?
(a) BOOTP (b) DHCP (c) DNS (d) FTP (e) HTTP.
30. The client TELNET translates characters that come from the local terminal into ______ form and delivers them to the network.
(a) ASCII (b) BCD (c) NVT (d) EBCDI (e) ABCD.
Section B : Problems (50 Marks)
1. 01001100011 encode this bit stream for the following digital-to-digital encoding formats?
a. NRZ – L
b. NRZ-I
c. Bipolar-AMI
d. Manchester
e. Differential Manchester. (2 + 2 + 2 + 2 + 2 = 10 marks)
2. a. What is multiplexing? What are the different types of multiplexing methods possible for analog signals? Explain.
b. Five signal sources are multiplexed using synchronous TDM. Each source produces 100 characters per second. Assume that there is byte interleaving and that each frame requires one bit for synchronization. What is the frame rate? What is the bit rate on the path? (8 + 2 = 10 marks)
3. What is the goal of ISDN? Explain subscriber access to ISDN and User Interfaces. (10 marks) 4. What is the difference between a physical address and a logical address? Explain IP addressing. (10 marks)
5. a. Describe different propagation modes of fiber optic cables. Explain advantages and disadvantages of fiber optic cables.
b. A signal is sampled. Each sample represents one of four levels. How many bits are needed to represent each sample? If the sampling rate is 8000 samples per second. What is the bit rate?
(8 + 2 = 10 marks)
Section C : Applied Theory (20 Marks)
6. a. What is ATM? Explain design goals and architecture?
b. Why is the control field from HDLC totally dropped from Frame Relay? (8 + 2 = 10 marks)
7. Explain responsibilities of TCP/IP protocol layer architectural model. Distinguish between TCP/IP model and OSI model. (10 marks)
Suggested Answers
1.
Answer : (a)
Reason : A digital signal has a bit interval of 40 microseconds. The bit rate is 25 kbps.
2.
Answer : (e)
Reason : RS-433 is the balanced interface
3.
Answer : (d)
Reason :. The sampling interval of a telephone voice signal is 100 Msec
4.
Answer : (c)
Reason : Packet generation in ALHOA network follows Normal distribution.
5.
Answer : (b)
Reason : Attenuation in an optical fiber can be as small as 3.4 dB/km
6.
Answer : (d)
Reason : Quantization is the process of a specific range of values to signal amplitudes.
7.
Answer : (b)
Reason : The sampling rate must be twice the highest frequency in the signal;
Sampling rate=2x11,000=22,000 samples/s
8.
Answer : (b)
Reason : A graded-index fiber has lower dispersion than the step-index fiber
9.
Answer : (e)
Reason : DC component and Synchronization are the limitations of unipolar encoding technique
10.
Answer : (c)
Reason : A digital signal has a bit rate of 2000 bps. The bit interval is the inverse of the bit rate.Bit interval=1/bir rate=1/2000=0.00050 s = 0.000500x106 micro sec = 500 Micro sec
11.
Answer : (b)
Reason : In Go-back-N ARQ, if frames 4,5, and 6 are received successfully, the receiver may send an ACK 7 to the sender.
12.
Answer : (b)
Reason : For stop-and-wait flow control, for n data packets sent, n acknowledgments are needed
13.
Answer : (d)
Reason : Wave Division Multiplexing (WDM) technique is involved signals composed of light beams because the medium is fiber optic cable.
14.
Answer : (a)
Reason : Analog Switched telephone service is least expensive.
15.
Answer : (d)
Reason : High Density Bipolar 3 (HDB3) d/d encoding technique is used to deliberately violate the alternate mark inversion..
16.
Answer : (b)
Reason : CSMA/CD is the access protocol used by traditional Ethernet.
17.
Answer : (d)
Reason : Address and data fields are variable length fields in MAC frame of FDDI.
18.
Answer : (a)
Reason : In Token Ring, when a frame reaches its destination station, the message is copied and the frame is sent back to the sender.
19.
Answer : (a)
Reason : A wireless LAN uses management frames for the initial communication between stations and the access points.
20.
Answer : (b)
Reason : Voice Over Frame Relay (VOFR) is a Frame Relay option that transmits voice through the network.
21.
Answer : (c)
Reason : ATM layer in ATM protocol has a 53-byte cell as an end product
22.
Answer : (e)
Reason : Frame Relay can operate in Data link and Physical layer
23.
Answer : (b)
Reason : Control plane is associated with signaling and the D channel
24.
Answer : (e)
Reason : The H channel in ISDN is used for applications requiring a transmission rate greater the 64 Kbps
25.
Answer : (a)
Reason : Transparent Bridge builds and updates its tables from address information on packets.
26.
Answer : (e)
Reason : HTTP has similarities to both FTP and SMTP
27.
Answer : (c)
Reason : A network using the CSMA random-access method with p equal to 0.25 will send 25 percent of the time after accessing an idle line.
28.
Answer : (d)
Reason : IP is responsible for Host to Host communication while TCP is responsible for Process to process communication.
29.
Answer : (b)
Reason : Dynamic Host Configuration Protocol (DHCP) provides temporary IP addresses for a limited period of time.
30.
Answer : (c)
Reason : The client TELNET translates characters that come from the local terminal into Network Virtual Terminal (NVT) form and delivers them to the network.
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