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1. Which of the following statements about synchronous and asynchronous I/O is NOT true?
(a) An ISR is invoked on completion of I/O in synchronous I/O but not in asynchronous I/O
(b) In both synchronous and asynchronous I/O an ISR (Interrupt Service Routine) is invoked after completion of the I/O
(c) A process making a synchronous I/O call waits until I/O is complete, but a process making an asynchronous I/O call
does not wait for completion of the I/O
(d) In the case of synchronous I/O, the process waiting for the completion of I/O is woken up by the ISR that is invoked
after the completion of I/O
2. Which of the following is NOT true of deadlock prevention and
deadlock avoidance schemes?
(a) In dead Lock prevention, the request for resources is always granted if the resulting state is safe
(b) In deadlock avoidance, the request for resources is always granted if the resulting state is safe
(c) Deadlock avoidance is less restrictive than deadlock prevention
(d) Deadlock avoidance requires knowledge of resource requirements a priori
3
4. A processor uses 36 bit physical addresses and 32 bit virtual addresses, with a page frame size of 4 Kbytes. Each page table entry is of size 4 bytes. A three level page table is used for virtual-to-physical address translation, where the virtual address is used as follows
bits 30-31 are used to index into the first level page table,
• bits 21-29 are used to index into the second level page table
• bits 12-20 are used to index into the third level page table
• bits 0-11 are used as offset within the page
The number of bits required for addressing the next level page table (or page frame) in the page table entry of the first, second and third level page tables are respectively.
(a) 20, 20 and 20
(b) 24, 24, and 24
(c) 24, 24 and 20.
(d) 25, 25 and 24
5. In which one of the following page replacement policies, Belady’s anomaly may occur?
(a) FIFO
(b) Optimal
(c) LRU
(d) MRU
6. The essential content(s) in each entry of a page table is/are
(a) virtual page number
(b) page frame number
(c) both virtual page number and page frame number
(d) access right information
7. Consider a system with 4 types of resources RI (3 units), R2 (2 units), R3 (3 units), R4 (2 units). A non-preemptive resource allocation policy is used. At any given instance, a request is not entertained if it cannot be completely satisfied. Three processes P1, P2, P3 request the resources as follows if executed independently.
Which one of the following statements is TRUE if all three processes run concurrently starting at time t = 0?
(a) All processes will finish without any deadlock
(b) Only P1 and P2 will be in deadlock
(c) Only P1 and P3 will be in deadlock
(d) All three processes will be in deadlock
8. Consider a disk system with 100 cylinders. The requests to access the cylinders occur in following sequence:
4,34, 10,7, 19, 73, 2,15, 6,20
Assuming that the head is currently at cylinder 50, what is the time taken to satisfy all requests if it takes 1 ms to move from one cylinder to adjacent one and shortest seek time first policy is used?
(a) 95ms
(b) 119rns
(c) 233 ms
(d) 276 ms
9. Which of the following assertions is FALSE about the Internet Protocol (IP)?
(a) It is possible for a computer to have multiple IP addresses
(b) IP packets from the same source to the same destination can take different routes in the network
(c) IP ensures that a packet is forwarded if it is unable to reach its destination within a given number of hopes
(d) The packet source cannot set the route of an outgoing packets; the route is determined only by the routing tables in the routers on the way
10. Which of the following functionalities must be implemented by a transport protocol over and above the network protocol?
(a) Recovery from packet losses
(b) Detection of duplicate packets
(c) Packet delivery in the correct order
(d) End to end connectivity
11. The subnet mask for a particular network is 255.255.3.1 . Which of the following pairs of IP addresses could belong to this network?
(a) 172.57.88.62 and 172.56.87.23.2
(b) 10.35.28.2 and 10.35.29.4
(c) 191.203.31.87 and 191.234.31.88
(d) 128.8.129.43 and 128.8.161.55
12. A 2 km long broadcast LAN has 107 bps bandwidth and uses CSMA/CD. The signal travels along the wire at 2 x 108 m/s. What is the minimum packet size that can be used on this network?
(a) 50 bytes
(b) 100 bytes
(c) 200 bytes
(d) None of the above
13. Host A is sending data to host B over a full duplex link. A and B are using the sliding window protocol for flow control. The send and receive window sizes are 5 packets each. Data packets (sent only from A to B) are all 1000 bytes long and the transmission time for such a packet is 50 micro s. Acknowledgment packets (sent only from B to A) are very small and require negligible transmission time. The propagation delay over the link is 200 micro s.. What is the maximum achievable throughput in this communication?
(a) 7.69 x 106 bps
(b) 11.11 x 106 bps
(c) 12.33 x 106 bps
(d) 15.00 x 106 bps
14.Choose the best matching between Group I and Group 2.
(al P-1 Q-4, R-3
(b) P-2, Q-4, R-1
(c) P-2, Q-3, R-1
(d) P-1, Q-3, R-2
15. Which of the following is NOT true with respect to a transparent bridge and a router?
(a) Both bridge and router selectively forward data packets
(b) A bridge uses IP addresses while a router uses MAC addresses
(c) A bridge builds up its routing table by inspecting incoming packets
(d) A router can connect between a LAN and a WAN
16. How many 8-bit characters can be transmitted per second over a 9600 baud serial communication link using asynchronous mode of transmission with one start bit, eight data bits, and one parity bit?
(a)600
(b) 800
(c)876
(d) 1200
17. A and B are the only two stations on an Ethernet. Each has a steady queue of frames to send. Both Aand B attempt to transmit a frame, collide, and A wins the first backoff race. At the end of this successful transmission by A, both A and B attempt to transmit and collide. The probability that A wins the second backoff race is
(a) 0.5
(b) 0.625
(c) 0.75
(d) 1.0
18.The routing table of a router is shown below:
On which interfaces will the router forward packets addressed to destinations 128.75.43.16 and 192.12.17.10 respectively?
(a) Eth1 and Eth2
(b) Eth0 and Eth2
(c) Eth0 andEth3
(d) Eth1 and Eth3
Data for Q. 19& Q. 20 are given below. Solve the problems and
choose the correct answers.
Consider three IP networks A, B and C. Host HA in network A sends
messages each containing 180 bytes of application data to a host HC in network C. The TCP layer prefixes a 20 byte header to the message. This passes through an intermediate network B. The maximum packet size, including 20 byte IP header, in each network is
A : 1000bytes
B : 100bytes
C : 1000bytes
The network A and B are connected through a 1 Mbps link, while B and C are connected by a 512 Kbps link (bps = bits per second).
19. Assuming that the packets are correctly delivered, how many bytes, including headers, are delivered to the IP layer at the destination for one application message, in the best case? Consider only data packets.
(a) 200
(b) 220
(c) 240
(d) 260
20. What is the rate at which application data is transferred to host H HC ?
Ignore errors, acknowledgments, and other overheads.
(a)325.5 Kbps
(b) 354.5 Kbps
(c)409.6 Kbps
(d) 512.0 Kbps
21. Packets of the same session may be routed through different paths n
(a) TCP, but not UDP
(b) TCP and UDP
(c) UDP, but not TCP
(d) Neither TCP, nor UDP
22. The address resolution protocol (ARP) is used for
(a) Finding the IP address from the DNS
(b) Finding the IP address of the default gateway
(c) Finding the IP address that corresponds to a MAC address
(d) Finding the MAC address that corresponds to an IP address
23. The maximum window size for data transmission using the selective
reject protocol with n-bit frame sequence numbers is
(a)2n
(b)2n-1
(c)2n-1
(d)2n-2
24. Tn a network of LANs connected by bridges, packets are sent from one LAN to another through intermediate bridges. Since more than one path may exist between two LANs, packets may have to be routed through multiple bridges. Why is the spanning tree algorithm used for bridge-routing?
(a) For shortest path routing between LANs
(b) For avoiding loops in the routing paths
(c) For fault tolerance
(d) For minimizing collisions
25. An organization has a class B network and wishes to form subnets for 64 departments. The subnet mask would be
(a)255.255.0.0
(b) 255.255.64.0
(c)255.255.128.0
(d) 255.255.255.0
Answers :
1 b
2 b
3 b
4 b
5 a
6 b
7 a
8 b
9 d
10 d
11 d
12 c
13 b
14 a
15 b
16 a
17 b
18 a
19 d
20 b
21 b
22 d
23 b
24 b
25 d
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