UNIT 1
1.ISO stands for
International Organization for Standardization
2.The main principle of layered architecture is
Separation of responsibility
3.In layered architecture, each layer is responsible for a
Finite
4.The convention and rules used in such communications are collectively known as
Layer protocol
5.OSI has two meanings refers to
Both a & b
6.Network is the term used for a group of
both a and b
7.The information exchanged between two computers is physically carried by means of
Electrical signal
8.For two computers to reliably exchange data, they must have a
Both a & b
9.Transmission media deals with the types of medium used , which is dictated by the
All of these
10. In error control, this corruption could be in the form of
Both a & b
11.Protocols should provide at least logical channels per connection
2
12.Data exchange can take place between any workstations
2
13.Depending on the nature of the involved application in layered architecture, the dialog type may be
All of these
14.Some good examples of presentation problems are the existing incompatibilities between the
Both a & b
15.This is the entities in the same layers but on different computers
Peer entities
16.Which function of the layer provides certain services
Service provider
17.Which function of the layer uses certain services
service user
18.Which is the point from where services can be accessed .each point is the unique address
SAP
19.Which is the reliable connectionless service with acknowledgement
Registered E-mail
20.Which is the unreliable connectionless service without acknowledgement
Junk E-mail
21.Which service is specified by a set of primitives available to a service user to interact with the service provider
Both a & b
22.Which are parameters to define conditions
Primitives
23.A confirmed services is defined with a
All of these
24.The OSI interface is a process of communication between adjacent layers in which data is passed between
All of these
25.The functions of the physical layer are
All of these
26.Examples of data link layers are
Both a & b
27.The data link layer also deals with the issue of addressing what is popularly known as
All of these
28.Some of the examples of MAC are
Both a & b
29.The routing of network layer may be
None of these
30.Which protocol uses the transport layer
TCP/IP
31.Some examples of APIs are
All of these
32.The data link layer is also known as
Link layer
33.TCP/IP layer specifies the
Physical layer
34.The Packet format and protocol at internet layer is called
Internet protocol
35.Which protocols are found in a Internet Layer of TCP/IP model
All of these
36.E-mail has two parts namely
Both a & b
37.MTA stands for
Message Transfer Agent
38.Which is the user interface to the mail system
User agent
39.There are a number of e-mail packages available. Some of them are free like
All of these
40.E-mail address has three parts
All of these
41.Data communication system within a building or campus is________
LAN
42.Application layer is implemented in ____________
End system
43.Which transmission media provides the highest transmission speed in a network?
optical fiber
44.The fiber optics transmission runs at ------------
1000
45.Physical layer accepts data or information from the data link layer and converts it into hardware specific operations so as to transfer the message through---------------------
physical cables
46.SMTP is the
de facto
47.SMTP uses
Tcp
48.The SMTP server also allows
Telnet service
49.MIME stands for
Multipurpose Internet Mail Extensions
50.POP3 stands for
Post Office Protocol
UNIT 2
1 Which of the following tasks is not done by data link layer?
d) channel coding
2 Which sublayer of the data link layer performs data link functions that depend upon the type of medium?
b) media access control sublayer
3 Automatic repeat request error management mechanism is provided by ________
a) logical link control sublayer
4 When 2 or more bits in a data unit has been changed during the transmission, the error is called ____________
burst error
5 CRC stands for __________
a) cyclic redundancy check
6 Which of the following is a data link protocol?
d)all of these
7 Which of the following is the multiple access protocol for channel access control?
c) Both CSMA/CD & CSMA/CA
8 The technique of temporarily delaying outgoing acknowledgements so that they can be hooked onto the next outgoing data frame is called ____________
a) piggybacking
9 Which of the following would be found in a Data Link layer header?
The source’s physical address
10 What is a primary function of the trailer information added by the data link layer encapsulation?
Supports error detection
11 Error detection at the data link layer is achieved by?
Cyclic redundancy codes
12 Under mark parity,each parity bit is?
Always set to 1
13 Which of the following devices is a PC component that connects the computer to the network?
NIC (Network Interface Card)
14 Switch is a Device of _________ Layer of OSI Model.
Data Link Layer
15 HUB is a _________ Device and Switch is a ________ Device.
Broadcast, Unicast
16 The data link layer takes the packets from _____ and encapsulates them into frames for transmission.
network layer
17 Which one of the following task is done by data link layer?
Framing
18 In the _________Protocol, if no acknowledgment for a frame has arrived, we resend all outstanding frames.
Go-Back-N ARQ
19 In the _________ protocol we avoid unnecessary transmission by sending only frames that are corrupted.
Selective-Repeat ARQ
20 Both Go-Back-N and Selective-Repeat Protocols use a _________.
sliding window
21 In Go-Back-N ARQ, if 5 is the number of bits for the sequence number, then the maximum size of the send window must be _____.
31
22 In Go-Back-N ARQ, if 5 is the number of bits for the sequence number, then the maximum size of the receive window must be _____.
1
23 In Selective Repeat ARQ, if 5 is the number of bits for the sequence number, then the maximum size of the send window must be _____.
16
24 High-level Data Link Control (HDLC) is a _______ protocol for communication over point-to-point and multipoint links.
bit-oriented
25 The most common protocol for point-to-point access is the Point-to-Point Protocol (PPP), which is a _________protocol.
byte-oriented
26 _______ control refers to a set of procedures used to restrict the amount of data that the sender can send before waiting for acknowledgment.
Flow
27 _________control in the data link layer is based on automatic repeat request, which is the retransmission of data.
Error
28 In Stop-and-Wait ARQ, we use sequence numbers to number the frames. The sequence numbers are based on __________arithmetic.
modulo-4
29 In Stop-and-Wait ARQ, the acknowledgment number always announces in ______ arithmetic the sequence number of the next frame expected.
modulo-2
30 In the Go-Back-N Protocol, if the size of the sequence number field is 8, the sequence numbers are in ________ arithmetic.
modulo-256
31 In _________, the station configuration is unbalanced. We have one primary station and multiple secondary stations.
NRM
32 In _________, the configuration is balanced. The link is point-to-point, and each station can function as a primary and a secondary.
ABM
33 In PPP, the ________ is responsible for establishing, maintaining, configuring, and terminating links.
LCP
34 In PPP, ________ is a simple authentication procedure with a two-step process.
PAP
35 In PPP, _______ is a three-way hand-shaking authentication protocol in which the password is kept secret; it is never sent online.
CHAP
36 _______ is a standard developed by ANSI for fiber-optic networks
SONET
37 _______ is a standard developed by ITU-T.
SDH
38 SONET has defined a hierarchy of signals called ________.
STSs
39 SDH has defined a hierarchy of signals called ________.
STMs
40 Station A uses 32 byte packets to transmit messages to Station B using a sliding window protocol. The round trip delay between A and B is 80 milliseconds and the bottleneck bandwidth on the path between A and B is 128 kbps. What is the optimal window size that A should use?
40
41 A bit-stuffing based framing protocol uses an 8-bit delimiter pattern of 01111110. If the output bit-string after stuffing is 01111100101, then the input bit-string is
111110101
42 Consider a selective repeat sliding window protocol that uses a frame size of 1 KB to send data on a 1.5 Mbps link with a one-way latency of 50 msec. To achieve a link utilization of 60%, the minimum number of bits required to represent the sequence number field is ________.
5
43 The message 11001001 is to be transmitted using the CRC polynomial x^3 + 1 to protect it from errors. The message that should be transmitted is:
11001001011
44 In a token ring network the transmission speed is 10^7 bps and the propagation speed is 200 metres/micro second. The 1-bit delay in this network is equivalent to:
20 metres of cable
45 There are n stations in a slotted LAN. Each station attempts to transmit with a probability p in each time slot. What is the probability that ONLY one station transmits in a given time slot? np(1-p)^(n-1)
46 In Ethernet when Manchester encoding is used, the bit rate is:
none of these
47 Consider the data of previous question. Suppose that the sliding window protocol is used with the sender window size of 2^i where is the number of bits identified in the previous question and acknowledgments are always piggybacked. After sending 2^i frames, what is the minimum time the sender will have to wait before starting transmission of the next frame? (Identify the closest choice ignoring the frame processing time.)
20ms
48 Frames of 1000 bits are sent over a 10^6 bps duplex link between two hosts. The propagation time is 25ms. Frames are to be transmitted into this link to maximally pack them in transit (within the link). What is the minimum number of bits (i) that will be required to represent the sequence numbers distinctly? Assume that no time gap needs to be given between transmission of two frames.
5
49 Let G(x) be the generator polynomial used for CRC checking. What is the condition that should be satisfied by G(x) to detect odd number of bits in error?
1+x is a factor of G(x)
50 Determine the maximum length of the cable (in km) for transmitting data at a rate of 500 Mbps in an Ethernet LAN with frames of size 10,000 bits. Assume the signal speed in the cable to be 2,00,000 km/s
2
UNIT 3
1 Which one of the following is not a function of network layer?
d) error control
2 The network layer protocol for internet is __________
b) internet protocol
3 ICMP is primarily used for __________
a) error and diagnostic functions
4 Which of the following is not applicable for IP?
a) Error reporting
5 Which field helps to check rearrangement of the fragments?
a) offset
6 The size of an IP address in IPv6 is _________
b) 128 bits
7 IPv6 does not use _________ type of address.
a) broadcast
8 The source-quench message in ICMP was designed to add a kind of ____________ to the IP. b) flow control
9 The term that is used to place packet in its route to its destination is called __________
c) Forwarding
10 Next-Hop Method is used to reduce contents of a _________
c) Routing Table
11 In Unicast Routing, Dijkstra algorithm creates a shortest path tree from a ________
a) Graph
12 Which protocol gives a full route table update every 30 seconds?
b) RIP
13 An area is _______.
a. part of an AS
14 To create a neighborhood relationship, a router running BGP sends an ________ message. a. open
15 The telephone line is an example of
d. Point-to-point link
16 In path vector routing, the Internet is divided into hierarchical domains called
a. Autonomous networks
17 IGMP operates __________.
a. locally
18 Which of the following routing algorithms can be used for network layer design?
d) all of the mentioned
19 Which one of the following algorithm is not used for congestion control?
d) routing information protocol
20 The _________ field determines the lifetime of IPv6 datagram
a) Hop limit
21 Which among the following features is present in IPv6 but not in IPv4?
d) Anycast address
22 Internet Control Message Protocol (ICMP) has been designed to compensate _________
d) All of the mentioned
23 Which of these is not a type of error-reporting message?
c) Router error
24 In Multicast Routing Protocol, flooding is used to broadcast packets but it creates ________ b) Loops
25 Which command displays RIP routing updates?
b) Debug IP rip
26 _________ is the default administrative distance of RIP.
c) 120
27 The computation of the shortest path in OSPF is usually done by ____________
c) Dijkstra’s algorithm
28 In ________ routing, we assume that there is one node (or more) in each autonomous system that acts on behalf of the entire autonomous system.
b. path vector
29 ___________ is an interdomain routing protocol using path vector routing.
a. BGP
30 In _______, the router may forward the received packet through several of its interfaces. b. multicasting
31 Multicast link state routing uses the _______ tree approach.
a. source-based
32 MOSPF is a _______ protocol.
a. data-driven
33 PIM-DM is used in a _______ multicast environment, such as a LAN.
d. none of the above
34 In distance vector routing algorithm, the routing tables are updated .....................
a. by exchanging information with the neighbours
35 To do multicast routing, each router computes a .....................
c. Spanning tree
36 A normal Flooding technique is an example of ..................
d. Broadcasting
37 When a host knows its physical address but not its IP address, it can use _____.
d. RARP
38 In an IPv4 packet, the value of HLEN is
b.5
39 In IPv4, formula for Length of data =
b. Total length - header length
40 A 4 byte IP address consists of __________
c) network address & host address
41 The TTL field has value 10. How many routers (max) can process this datagram?
c) 10
42 During debugging, we can use the ____________ program to find if a host is alive and responding.
c) ping
43 In windows ____________ can be used to trace the route of the packet from the source to the destination.
b) tracert
44 "What is the correct order of the operations of OSPF?i – Hello packets
ii – Propagation of link-state information and building of routing tables
iii – Establishing adjacencies and synchronization of database
"
b) i-iii-ii
45 In OSPF database descriptor packet, which field is used to detect a missing packet?
c) Database descriptor sequence number
46 What is the IP protocol number for OSPF packets?
a) 89
47 A _______ message tells an upstream router to stop sending multicast messages for a specific group through a specific router.
c. prune
48 The idea of aggregation is equal to
b. Subnetting
49 An IGMP query is sent from a _______ to a _______.
c. router; host or router
50 How can you see the address of the DHCP server from which a client received its IP address? c. By using IPCONFIG/ALL
UNIT 4
1 Which of the following are transport layer protocols used in networking?
c) TCP and UDP
2 An endpoint of an inter-process communication flow across a computer network is called __________
a) socket
3 Which one of the following is a version of UDP with congestion control?
a) datagram congestion control protocol
4 Transport layer protocols deals with ____________
b) process to process communication
5 Which of the following is a transport layer protocol?
a) stream control transmission protocol
6 Which of the following is false with respect to TCP?
d) Unreliable
7 In TCP, sending and receiving data is done as _______
a) Stream of bytes
8 In segment header, sequence number and acknowledgement number fields refer to _______
a) Byte number
9 Size of TCP segment header ranges between ___________
c) 20 and 60 bytes
10 Return value of the UDP port “Chargen” is _______
a) String of characters
11 Beyond IP, UDP provides additional services such as _______
d) Demultiplexing and error checking
12 What is the main advantage of UDP?
c) Low overhead
13 Port number used by Network Time Protocol (NTP) with UDP is ________
b) 123
14 What is the header size of a UDP packet?
a) 8 bytes
15 “Total length” field in UDP packet header is the length of _________
d) UDP header plus data
16 In an SCTP packet, control chunks come ___________ data chunks.
B) before
17 The server program tells its TCP that it is ready to accept a connection. This process is called ___________
d) Passive open
18 SYNC flooding attack belongs to a type of security attack known as ___________
d) Denial-of-service attack
19 A client that wishes to connect to an open server tells its TCP that it needs to be connected to that particular server. The process is called ___________
a) Active open
20 Stream control transmission protocol is a new
a)message oriented transport layer protocol
21 SCTP protocol combines the best features of
d)Both a and c
22 The combination of IP address and port number is called
c)socket address
23 The value of window size determined by
b)the receiver
24 In SCTP, the acknowledgment number and window size are part of each ________.
B) control chunk
25 A connection in SCTP is called an ____________.
B) association
26 The association identifier in SCTP is __________________.
A) a unique verification tag
27 In SCTP, a data chunk is numbered using ________.
A) a TSN
28 UDP needs the _______ address to deliver the user datagram to the correct application process.
A) port
29 Transmission control protocol ___________
d) all of the mentioned
30 Socket-style API for windows is called ____________
b) winsock
31 TCP process may not write and read data at the same speed. So we need __________ for storage.
b) Buffers
32 TCP groups a number of bytes together into a packet called _______
c) Segment
33 Communication offered by TCP is ________
a) Full-duplex
34 The value of acknowledgement field in a segment defines _______
c) sequence number of the next byte to be received
35 The receiver of the data controls the amount of data that are to be sent by the sender is referred to as ___________
a) Flow control
36 What allows TCP to detect lost segments and in turn recover from that loss?
b) Acknowledgment number
37 Which of the following is false with respect to UDP?
a) Connection-oriented
38 Which is the correct expression for the length of UDP datagram?
a) UDP length = IP length – IP header’s length
39 The ______ field is used to detect errors over the entire user datagram.
b) checksum
40 In Three-Way Handshaking process, the situation where both the TCP’s issue an active open is ___________
c) Simultaneous open
41 Flow control in SCTP is similar to that in
a)TCP
42 SCTP,association allows multiple IP address for
b)each end
43 The FIN+ACK segment consumes--------------sequence number if it does not carry data c)one
44 SCTP allows __________ service in each association.
B) multistream
45 SCTP association allows _____________ for each end.
B) multiple IP addresses
46 There is no need for a header length field in SCTP because ________________.
C) both a and b
47 User datagram protocol is called connectionless because _____________
a) all UDP packets are treated independently by transport layer
48 A _____ is a TCP name for a transport service access point.
a) port
49 To achieve reliable transport in TCP, ___________ is used to check the safe and sound arrival of data.
d) Acknowledgment
50 Suppose a TCP connection is transferring a file of 1000 bytes. The first byte is numbered 10001. What is the sequence number of the segment if all data is sent in only one segment?
b) 10001
51 TCP allows the sending process to deliver data as a _______of bytes and allows the receiving process to obtain data as a _________ of bytes.
B) stream; stream
52 The ports ranging from 49,152 to 65,535 can be used as temporary or private port numbers. They are called the ________ ports.
C) dynamic
53 The inclusion of the checksum in the TCP segment is ________.
B) mandatory
54 __________ control regulates the amount of data a source can send before receiving an acknowledgment from the destination.
B) Flow
49. SCTP association allows _____________ for each end.
A) only one IP address
B) multiple IP addresses
C) only two IP address
D) none of the above
50. UDP needs the _______ address to deliver the user datagram to the correct application process.
A) port
B) application
C) internet
D) none of the above
UNIT 5
1 Which is not a application layer protocol?
d) TCP
2 The packet of information at the application layer is called __________
b) Message
3 Application layer offers _______ service.
a) End to end
4 Pick the odd one out.
d) Interactive games
5 Which of the following is an application layer service?
d) All of the mentioned
6 Electronic mail uses which Application layer protocol?
a) SMTP
7 Application layer protocol defines ____________
d) all of the mentioned
8 Which one of the following protocol delivers/stores mail to reciever server?
a) simple mail transfer protocol
9 Which one of the following is not an application layer protocol?
c) resource reservation protocol
10 When displaying a web page, the application layer uses the _____________
a) HTTP protocol
11 The values GET, POST, HEAD etc are specified in ____________ of HTTP message
a) Request line
12 What is a web browser?
d) all of the mentioned
13 Common gateway interface is used to _______
a) generate executable files from web content by web server
14 Which one of the following allows client to update their DNS entry as their IP address change?
a) dynamic DNS
15 In Network Management System, the division that is responsible for controlling access to network based on a predefined policy is called _________
d) Security Management
16 Full duplex mode increases the capacity of each domain by ________
a) 10 to 20 mbps
17 _______ allows you to connect and login to a remote computer
a) Telnet
18 Telnet is used for _______
c) Remote Login
19 All telnet operations are sent as ________
b) 8 bits
20 FTP uses _________ parallel TCP connections to transfer a file.
b) 2
21 FTP server _____________
a) Maintains state information
22 The commands, from client to server, and replies, from server to client, are sent across the control connection in ________ bit ASCII format.
b) 7
23 The data transfer mode of FTP, in which all the fragmenting has to be done by TCP is ________
a) Stream mode
24 The password is sent to the server using ________ command
b) PASS
25 Secure shell (SSH) network protocol is used for __________
d) all of the mentioned
26 Which one of the following authentication method is used by SSH?
c) password
27 An email client needs to know the _________ of its initial SMTP server.
a) IP address
28 SMTP defines _______
a) message transport
29 Which one of the following is an architecture paradigms?
d) Both Peer-to-Peer & Client-Server
30 Application developer has permission to decide the following on transport layer side
c) Both Transport layer protocol and Maximum buffer size
31 E-mail is _________
c) Elastic application
32 To deliver a message to the correct application program running on a host, the _______ address must be consulted.
c) Port
33 Which is a time-sensitive service?
d) Internet telephony
34 Transport services available to applications in one or another form _________
d) All of the mentioned
35 The ____________ translates internet domain and host names to IP address.
a) domain name system
36 Which one of the following is an internet standard protocol for managing devices on IP network?
b) simple network management protocol
37 Which one of the following is not correct?
d) All of the mentioned
38 The HTTP request message is sent in _________ part of three-way handshake.
c) Third
39 A DNS client is called _________
b) DNS resolver
40 If a server has no clue about where to find the address for a hostname then _______
a) server asks to the root server
41 The application-level protocol in which a few manager stations control a set of agents is called ______
c) SNMP
42 SNMP is the framework for managing devices in an internet using the ______
a) TCP/IP protocol
43 Configuration management can be divided into which two subsystems?
a) Reconfiguration and documentation
44 Which operating mode of telnet is full duplex?
c) line mode
45 AbsoluteTelnet is a telnet client for _______ Operating system.
a) windows
46 If 5 files are transferred from server A to client B in the same session. The number of TCP connections between A and B is _______
d) 6
47 SSH can be used in only _____________
c) both unix-like and windows systems
48 SMTP is not used to deliver messages to ______
c) user’s word processor
49 Which one of the following allows a user at one site to establish a connection to another site and then pass keystrokes from local host to remote host?
c) Telnet
50 The ASCII encoding of binary data is called
a) base 64 encoding
51 Which protocol is a signaling communication protocol used for controlling multimedia communication sessions?
a) session initiation protocol
52 The default connection type used by HTTP is _________
a) Persistent
53 The time taken by a packet to travel from client to server and then back to the client is called __________
b) RTT
54 A piece of icon or image on a web page associated with another webpage is called ______ b) hyperlink
55 Which one of the following is not used to generate dynamic web pages?
d) CSS
56 The entire hostname has a maximum of ___________
a) 255 characters
57 The domain name system is maintained by _______
a) distributed database system
58 FTP is built on _____ architecture.
a) Client-server
59 SSH uses ___________ to authenticate the remote computer.
a) public-key cryptography
60 SSH-2 does not contain ______________
c) physical layer
Computer Edu Gate
1. Determine the maximum length of the cable (in km) for transmitting data at a rate of 500 Mbps in an Ethernet LAN with frames of size 10,000 bits. Assume the signal speed in the cable to be 2,00,000 km/s.
a. 1
b. 2
c. 2.5
d. 5
Answer: (b).2
2. Let G(x) be the generator polynomial used for CRC checking. What is the condition that should be satisfied by G(x) to detect odd number of bits in error?
a. G(x) contains more than two terms
b. G(x) does not divide 1+x^k, for any k not exceeding the frame length
c. 1+x is a factor of G(x)
d. G(x) has an odd number of terms
Answer: (c).1+x is a factor of G(x)
3. Frames of 1000 bits are sent over a 10^6 bps duplex link between two hosts. The propagation time is 25ms. Frames are to be transmitted into this link to maximally pack them in transit (within the link). What is the minimum number of bits (i) that will be required to represent the sequence numbers distinctly? Assume that no time gap needs to be given between transmission of two frames.
a. i = 2
b. i = 3
c. i = 4
d. i = 5
Answer: (d).i = 5
4. In Ethernet when Manchester encoding is used, the bit rate is:
a. Half the baud rate
b. Twice the baud rate
c. Same as the baud rate
d. None of the above
Answer: (a).Half the baud rate
5. There are n stations in a slotted LAN. Each station attempts to transmit with a probability p in each time slot. What is the probability that ONLY one station transmits in a given time slot?
a. (1-p)^(n-1)
b. np(1-p)^(n-1)
c. p(1-p)^(n-1)
d. 1-(1-p)^(n-1)
Answer: (b).np(1-p)^(n-1)
6. In a token ring network the transmission speed is 10^7 bps and the propagation speed is 200 metres/micro second. The 1-bit delay in this network is equivalent to:
a. 500 metres of cable
b. 200 metres of cable
c. 20 metres of cable
d. 50 metres of cable
Answer: (c).20 metres of cable
7. The message 11001001 is to be transmitted using the CRC polynomial x^3 + 1 to protect it from errors. The message that should be transmitted is:
a. 11001001000
b. 11001001011
c. 11001010
d. 110010010011
Answer: (b).11001001011
8. Consider a token ring network with a length of 2 km having 10 stations including a monitoring station. The propagation speed of the signal is 2 × 10^8 m/s and the token transmission time is ignored. If each station is allowed to hold the token for 2 μsec, the minimum time for which the monitoring station should wait (in μsec)before assuming that the token is lost is _______.
a. 28 to 30
b. 20 to 22
c. 0 to 2
d. 31 to 33
Answer: (a).28 to 30
9. Consider a selective repeat sliding window protocol that uses a frame size of 1 KB to send data on a 1.5 Mbps link with a one-way latency of 50 msec. To achieve a link utilization of 60%, the minimum number of bits required to represent the sequence number field is ________.
a. 3
b. 4
c. 5
d. 6
Answer: (c).5
10. A bit-stuffing based framing protocol uses an 8-bit delimiter pattern of 01111110. If the output bit-string after stuffing is 01111100101, then the input bit-string is
a. 0111110100
b. 0111110101
c. 0111111101
d. 0111111111
Answer: (b).0111110101
11. Station A uses 32 byte packets to transmit messages to Station B using a sliding window protocol. The round trip delay between A and B is 80 milliseconds and the bottleneck bandwidth on the path between A and B is 128 kbps. What is the optimal window size that A should use?
a. 20
b. 40
c. 160
d. 320
Answer: (b).40
12. Suppose the round trip propagation delay for a 10 Mbps Ethernet having 48-bit jamming signal is 46.4 ms. The minimum frame size is
a. 94
b. 416
c. 464
d. 512
Answer: (c).464
13. 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, two stop bits, and one parity bit ?
a. 600
b. 800
c. 876
d. 1200
Answer: (b).800
14. A and B are the only two stations on an Ethernet. Each has a steady queue of frames to send. Both A and 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
Answer: (b).0.625
15. A 2 km long broadcast LAN has 10^7 bps bandwidth and uses CSMA/CD. The signal travels along the wire at 2 × 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 these
Answer: (d).None of these
16. 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 µs. Acknowledgement packets (sent only from B to A) are very small and require negligible transmission time. The propagation delay over the link is 200 us. What is the maximum achievable throughput in this communication?
a. 7.69 × 10^6 bytes per second
b. 11.11 × 10^6 bytes per second
c. 12.33 × 10^6 bytes per second
d. 15.00 × 10^6 bytes per second
Answer: (b).11.11 × 10^6 bytes per second
17. In serial data transmission, every byte of data is padded with a ‘0’ in the beginning and one or two ‘I’ s at the end of byte because
a. Receiver is to be synchronized for byte reception
b. Receiver recovers lost ‘0’ and ‘1’s from these padded bits
c. Padded bits are useful in parity computation
d. None of these
Answer: (a).Receiver is to be synchronized for byte reception
18. Consider a LAN with four nodes S1, S2, S3 and S4. Time is divided into fixed-size slots, and a node can begin its transmission only at the beginning of a slot. A collision is said to have occurred if more than one node transmit in the same slot. The probabilities of generation of a frame in a time slot by S1, S2, S3 and S4 are 0.1, 0.2, 0.3 and 0.4, respectively. The probability of sending a frame in the first slot without any collision by any of these four stations is _________.
a. 0.462
b. 0.711
c. 0.5
d. 0.652
Answer: (a).0.462
19. Suppose that the stop-and-wait protocol is used on a link with a bit rate of 64 kilobits per second and 20 milliseconds propagation delay. Assume that the transmission time for the acknowledgment and the processing time at nodes are negligible. Then the minimum frame size in bytes to achieve a link utilization of at least 50% is _________.
a. 160
b. 320
c. 640
d. 220
Answer: (b).320
20. Consider a CSMA/CD network that transmits data at a rate of 100 Mbps (108 bits per second) over a 1 km (kilometer) cable with no repeaters. If the minimum frame size required for this network is 1250 bytes, what is the signal speed (km/sec) in the cable?
a. 8000
b. 10000
c. 16000
d. 20000
Answer: (d).20000
21. Which one of the following statements is FALSE ?
a. Packet switching leads to better utilization of bandwidth resources than circuit switching
b. Packet switching results in less variation in delay than circuit switching
c. Packet switching requires more per packet processing than circuit switching
d. Packet switching can lead to reordering unlike in circuit switching
Answer: (b).Packet switching results in less variation in delay than circuit switching
22. Which of the following statements is TRUE about CSMA/CD ?
a. IEEE 802.11 wireless LAN runs CSMA/CD protocol
b. Ethernet is not based on CSMA/CD protocol
c. CSMA/CD is not suitable for a high propagation delay network like satellite network
d. There is no contention in a CSMA/CD network
Answer: (c).CSMA/CD is not suitable for a high propagation delay network like satellite network
23. Which of the following statements is FALSE regarding a bridge?
a. Bridge is a layer 2 device
b. Bridge reduces collision domain
c. Bridge is used to connect two or more LAN segments
d. Bridge reduces broadcast domain
Answer: (d).Bridge reduces broadcast domain
24. A network with CSMA/CD protocol in the MAC layer is running at 1 Gbps over a 1 km cable with no repeaters. The signal speed in the cable is 2 x 108 m/sec. The minimum frame size for this network should be
a. 10000 bits
b. 10000 bytes
c. 5000 bits
d. 5000 bytes
Answer: (a).10000 bits
25. A channel has a bit rate of 4 kbps and one-way propagation delay of 20 ms. The channel uses stop and wait protocol. The transmission time of the acknowledgement frame is negligible. To get a channel efficiency of at least 50%, the minimum frame size should be
a. 80 bytes
b. 80 bits
c. 160 bytes
d. 160 bits
Answer: (d).160 bits
26. In a TDM medium access control bus LAN, each station is assigned one time slot per cycle for transmission. Assume that the length of each time slot is the time to transmit 100 bits plus the end-to-end propagation delay. Assume a propagation speed of 2 x 10^8 m/sec. The length of the LAN is 1 km with a bandwidth of 10 Mbps. The maximum number of stations that can be allowed in the LAN so that the throughput of each station can be 2/3 Mbps is
a. 3
b. 5
c. 10
d. 20
Answer: (c).10
27. Consider the following message M = 1010001101. The cyclic redundancy check (CRC) for this message using the divisor polynomial x^5 + x^4 + x^2 + 1 is :
a. 01110
b. 01011
c. 10101
d. 10110
Answer: (a).01110
28. A sender uses the Stop-and-Wait ARQ protocol for reliable transmission of frames. Frames are of size 1000 bytes and the transmission rate at the sender is 80 Kbps (1Kbps = 1000 bits/second). Size of an acknowledgement is 100 bytes and the transmission rate at the receiver is 8 Kbps. The one-way propagation delay is 100 milliseconds. Assuming no frame is lost, the sender throughput is __________ bytes/second.
a. 2500
b. 2000
c. 1500
d. 500
Answer: (a).2500
29. In an Ethernet local area network, which one of the following statements is TRUE ?
a. A station stops to sense the channel once it starts transmitting a frame
b. The purpose of the jamming signal is to pad the frames that are smaller than the minimum frame size
c. A station continues to transmit the packet even after the collision is detected
d. The exponential backoff mechanism reduces the probability of collision on retransmissions
Answer: (d).The exponential backoff mechanism reduces the probability of collision on retransmissions
30. A network has a data transmission bandwidth of 20 × 10 6 bits per second. It uses CSMA/CD in the MAC layer. The maximum signal propagation time from one node to another node is 40 microseconds. The minimum size of a frame in the network is _________ bytes.
a. 200
b. 250
c. 400
d. 1200
Answer: (a).200
31. Consider a 128×10 3 bits/second satellite communication link with one way propagation delay of 150 milliseconds. Selective retransmission (repeat) protocol is used on this link to send data with a frame size of 1 kilobyte. Neglect the transmission time of acknowledgement. The minimum number of bits required for the sequence number field to achieve 100% utilization is ___________
a. 2
b. 4
c. 6
d. 8
Answer: (b).4
32. How many bytes of data can be sent in 15 seconds over a serial link with baud rate of 9600 in asynchronous mode with odd parity and two stop bits in the frame?
a. 10,000 bytes
b. 12,000 bytes
c. 15,000 bytes
d. 27,000 bytes
Answer: (b).12,000 bytes
33. A 1Mbps satellite link connects two ground stations. The altitude of the satellite is 36,504 km and speed of the signal is 3 × 10^8 m/s. What should be the packet size for a channel utilization of 25% for a satellite link using go-back-127 sliding window protocol? Assume that the acknowledgment packets are negligible in size and that there are no errors during communication.
a. 120 bytes
b. 60 bytes
c. 240 bytes
d. 90 bytes
Answer: (a).120 bytes
34. The minimum frame size required for a CSMA/CD based computer network running at 1 Gbps on a 200m cable with a link speed of 2 × 10^8m/s is
a. 125 bytes
b. 250 bytes
c. 500 bytes
d. None of these
Answer: (b).250 bytes
35. In an IPv4 datagram, the M bit is 0, the value of HLEN is 10, the value of total length is 400 and the fragment offset value is 300. The position of the datagram, the sequence numbers of the first and the last bytes of the payload, respectively are
a. Last fragment, 2400 and 2789
b. First fragment, 2400 and 2759
c. Last fragment, 2400 and 2759
d. Middle fragment, 300 and 689
Answer: (c).Last fragment, 2400 and 2759
36. Consider a source computer(S) transmitting a file of size 106 bits to a destination computer(D)over a network of two routers (R1 and R2) and three links(L1, L2, and L3). L1connects S to R1; L2 connects R1 to R2; and L3 connects R2 to D.Let each link be of length 100 km. Assume signals travel over each link at a speed of 108 meters per second.Assume that the link bandwidth on each link is 1Mbps. Let the file be broken down into 1000 packets each of size 1000 bits. Find the total sum of transmission and propagation delays in transmitting the file from S to D?
a. 1005 ms
b. 1010 ms
c. 3000 ms
d. 3003 ms
Answer: (a).1005 ms
37. One of the header fields in an IP datagram is the Time to Live(TTL)field.Which of the following statements best explains the need for this field?
a. It can be used to prioritize packets
b. It can be used to reduce delays
c. It can be used to optimize throughput
d. It can be used to prevent packet looping
Answer: (d).It can be used to prevent packet looping
38. For which one of the following reasons does Internet Protocol (IP) use the time-to- live (TTL) field in the IP datagram header
a. Ensure packets reach destination within that time
b. Discard packets that reach later than that time
c. Prevent packets from looping indefinitely
d. Limit the time for which a packet gets queued in intermediate routers
Answer: (c).Prevent packets from looping indefinitely
39. Consider the following three statements about link state and distance vector routing protocols, for a large network with 500 network nodes and 4000 links.
[S1] The computational overhead in link state protocols
is higher than in distance vector protocols.
[S2] A distance vector protocol (with split horizon)
avoids persistent routing loops, but not a link
state protocol.
[S3] After a topology change, a link state protocol
will converge faster than a distance vector
protocol.
Which one of the following is correct about S1, S2, and S3 ?
a. S1, S2, and S3 are all true
b. S1, S2, and S3 are all false
c. S1 and S2 are true, but S3 is false
d. S1 and S3 are true, but S2 is false
Answer: (d).S1 and S3 are true, but S2 is false
40. Which one of the following is TRUE about interior Gateway routing protocols - Routing Information Protocol (RIP) and Open Shortest Path First (OSPF)?
a. RIP uses distance vector routing and OSPF uses link state routing
b. OSPF uses distance vector routing and RIP uses link state routing
c. Both RIP and OSPF use link state routing
d. Both RIP and OSPF use distance vector routing
Answer: (a).RIP uses distance vector routing and OSPF uses link state routing
41. An IP machine Q has a path to another IP machine H via three IP routers R1, R2, and R3.
Q—R1—R2—R3—H
H acts as an HTTP server, and Q connects to H via HTTP and downloads a file. Session layer encryption is used, with DES as the shared key encryption protocol. Consider the following four pieces of information:
[I1] The URL of the file downloaded by Q
[I2] The TCP port numbers at Q and H
[I3] The IP addresses of Q and H
[I4] The link layer addresses of Q and H
Which of I1, I2, I3, and I4 can an intruder learn through sniffing at R2 alone?
a. Only I1 and I2
b. Only I1
c. Only I2 and I3
d. Only I3 and I4
Answer: (c).Only I2 and I3
42. Host A (on TCP/IP v4 network A) sends an IP datagram D to host B (also on TCP/IP v4 network B). Assume that no error occurred during the transmission of D. When D reaches B, which of the following IP header field(s) may be different from that of the original datagram D?
(i) TTL
(ii) Checksum
(iii) Fragment Offset
a. (i) only
b. (i) and (ii) only
c. (ii) and (iii) only
d. (i), (ii) and (iii)
Answer: (d).(i), (ii) and (iii)
43. Classless Inter-domain Routing (CIDR) receives a packet with address 131.23.151.76. The router’s routing table has the following entries:
Prefix Output Interface Identifier
131.16.0.0/12 3
131.28.0.0/14 5
131.19.0.0/16 2
131.22.0.0/15 1
The identifier of the output interface on which this packet will be forwarded is ______.
a. 1
b. 2
c. 3
d. 5
Answer: (a).1
44. Every host in an IPv4 network has a 1-second resolution real-time clock with battery backup. Each host needs to generate up to 1000 unique identifiers per second. Assume that each host has a globally unique IPv4 address. Design a 50-bit globally unique ID for this purpose. After what period (in seconds) will the identifiers generated by a host wrap around?
a. 128
b. 64
c. 256
d. 512
Answer: (c).256
45. An IP router with a Maximum Transmission Unit (MTU) of 1500 bytes has received an IP packet of size 4404 bytes with an IP header of length 20 bytes. The values of the relevant fields in the header of the third IP fragment generated by the router for this packet are
a. MF bit: 0, Datagram Length: 1444; Offset: 370
b. MF bit: 1, Datagram Length: 1424; Offset: 185
c. MF bit: 1, Datagram Length: 1500; Offset: 37
d. MF bit: 0, Datagram Length: 1424; Offset: 2960
Answer: (a).MF bit: 0, Datagram Length: 1444; Offset: 370
46. Two computers C1 and C2 are configured as follows. C1 has IP address 203.197.2.53 and netmask 255.255.128.0. C2 has IP address 203.197.75.201 and netmask 255.255.192.0. which one of the following statements is true?
a. C1 and C2 both assume they are on the same network
b. C2 assumes C1 is on same network, but C1 assumes C2 is on a different network
c. C1 assumes C2 is on same network, but C2 assumes C1 is on a different network
d. C1 and C2 both assume they are on different networks
Answer: (c).C1 assumes C2 is on same network, but C2 assumes C1 is on a different network
47. Station A needs to send a message consisting of 9 packets to Station B using a sliding window (window size 3) and go-back-n error control strategy. All packets are ready and immediately available for transmission. If every 5th packet that A transmits gets lost (but no acks from B ever get lost), then what is the number of packets that A will transmit for sending the message to B?
a. 12
b. 14
c. 16
d. 18
Answer: (c).16
48. 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
Answer: (d).Finding the MAC address that corresponds to an IP address
49. In a packet switching network, packets are routed from source to destination along a single path having two intermediate nodes. If the message size is 24 bytes and each packet contains a header of 3 bytes, then the optimum packet size is:
a. 4
b. 6
c. 7
d. 9
Answer: (d).9
50. The routing table of a router is shown below:
Destination Sub net mask Interface
128.75.43.0 255.255.255.0 Eth0
128.75.43.0 255.255.255.128 Eth1
192.12.17.5 255.255.255.255 Eth3
default Eth2
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 and Eth3
d. Eth1 and Eth3
Answer: (a).Eth1 and Eth2
51. 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 discarded if it is unable to reach its destination within a given number of hops
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
Answer: (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
52. Routers forward a packet using forwarding table entries. The network address of incoming packet may match multiple entries. How routers resolve this?
a. Forward it the the router whose entry matches with the longest prefix of incoming packet
b. Forward the packet to all routers whose network addresses match
c. Discard the packet
d. Forward it the the router whose entry matches with the longest suffix of incoming packet
Answer: (a).Forward it the the router whose entry matches with the longest prefix of incoming packet
53. Which one of the following fields of an IP header is NOT modified by a typical IP router?
a. Checksum
b. Source address
c. Time to Live (TTL)
d. Length
Answer: (b).Source address
54. In the network 200.10.11.144/27, the fourth octet (in decimal) of the last IP address of the network which can be assigned to a host is ________.
a. 158
b. 255
c. 222
d. 223
Answer: (a).158
55. If a Company require 60 hosts then What is the best possible subnet mask?
a. 255.255.255.0
b. 255.255.255.192
c. 255.255.225.224
d. 225.225.255.240
Answer: (b).255.255.255.192
56. In class C , if subnet mask is 255.255.255.224, then calculates number of subnet?
a. 6
b. 8
c. 4
d. None of the Above
Answer: (a).6
57. A subnet has been assigned a subnet mask of 255.255.255.192. What is the maximum number of hosts that can belong to this subnet?
a. 14
b. 30
c. 62
d. 126
Answer: (c).62
58. A host is connected to a Department network which is part of a University network. The University network, in turn, is part of the Internet. The largest network in which the Ethernet address of the host is unique is:
a. the subnet to which the host belongs
b. the Department network
c. the University network
d. the Internet
Answer: (d).the Internet
59. In TCP, a unique sequence number is assigned to each
a. byte
b. word
c. segment
d. message
Answer: (a).byte
60. Which of the following objects can be used in expressions and scriplets in JSP (Java Server Pages) without explicitly declaring them?
a. session and request only
b. request and response only
c. response and session only
d. session, request and response
Answer: (d).session, request and response
61. In the TCP/IP protocol suite, which one of the following is NOT part of the IP header?
a. Fragment Offset
b. Source IP address
c. Destination IP address
d. Destination port number
Answer: (d).Destination port number
62. Suppose that the maximum transmit window size for a TCP connection is 12000 bytes. Each packet consists of 2000 bytes. At some point of time, the connection is in slow-start phase with a current transmit window of 4000 bytes. Subsequently, the transmitter receives two acknowledgements. Assume that no packets are lost and there are no time-outs. What is the maximum possible value of the current transmit window?
a. 4000 bytes
b. 8000 bytes
c. 10000 bytes
d. 12000 bytes
Answer: (b).8000 bytes
63. Traceroute reports a possible route that is taken by packets moving from some host A to some other host B. Which of the following options represents the technique used by traceroute to identify these hosts
a. By progressively querying routers about the next router on the path to B using ICMP packets, starting with the first router
b. By requiring each router to append the address to the ICMP packet as it is forwarded to B. The list of all routers en-route to B is returned by B in an ICMP reply packet
c. By ensuring that an ICMP reply packet is returned to A by each router en-route to B, in the ascending order of their hop distance from A
d. By locally computing the shortest path from A to B
Answer: (a).By progressively querying routers about the next router on the path to B using ICMP packets, starting with the first router
64. Count to infinity is a problem associated with
a. link state routing protocol
b. distance vector routing protocol
c. DNS while resolving host name
d. TCP for congestion control
Answer: (b).distance vector routing protocol
65. In a communication network, a packet of length L bits takes link L1 with a probability of p1or link L2 with a probability of p2. Link L1 and L2 have bit error probability of b1 and b2 respectively. The probability that the packet will be received without error via either L1 or L2 is
a. (1 - b1)Lp1 + (1 - b2)Lp2
b. [1 - (b1 + b2)L]p1p2
c. (1 - b1)L (1 - b2)Lp1p2
d. 1 - (b1Lp1 + b2Lp2)
Answer: (a).(1 - b1)Lp1 + (1 - b2)Lp2
66. A company has a class C network address of 204.204.204.0. It wishes to have three subnets, one with 100 hosts and two with 50 hosts each. Which one of the following options represents a feasible set of subnet address/subnet mask pairs?
a. 204.204.204.128/255.255.255.192 204.204.204.0/255.255.255.128 204.204.204.64/255.255.255.128
b. 204.204.204.0/255.255.255.192 204.204.204.192/255.255.255.128 204.204.204.64/255.255.255.128
c. 204.204.204.128/255.255.255.128 204.204.204.192/255.255.255.192 204.204.204.224/255.255.255.192
d. 204.204.204.128/255.255.255.128 204.204.204.64/255.255.255.192 204.204.204.0/255.255.255.192
Answer: (d).204.204.204.128/255.255.255.128 204.204.204.64/255.255.255.192 204.204.204.0/255.255.255.192
67. Assume that "host1.mydomain.dom" has an IP address of 145.128.16.8. Which of the following options would be most appropriate as a subsequence of steps in performing the reverse lookup of 145.128.16.8? In the following options "NS" is an abbreviation of "nameserver".
a. Query a NS for the root domain and then NS for the "dom" domains
b. Directly query a NS for "dom" and then a NS for "mydomain.dom" domains
c. Query a NS for in-addr.arpa and then a NS for 128.145.in-addr.arpa domains
d. Directly query a NS for 145.in-addr.arpa and then a NS for 128.145.in-addr.arpa domains
Answer: (c).Query a NS for in-addr.arpa and then a NS for 128.145.in-addr.arpa domains
68. An IP datagram of size 1000 bytes arrives at a router. The router has to forward this packet on a link whose MTU (maximum transmission unit) is 100 bytes. Assume that the size of the IP header is 20 bytes. The number of fragments that the IP datagram will be divided into for transmission is :
a. 10
b. 50
c. 12
d. 13
Answer: (d).13
69. Which of the following statements is TRUE ?
a. Both Ethernet frame and IP packet include checksum fields
b. Ethernet frame includes a checksum field and IP packet includes a CRC field
c. Ethernet frame includes a CRC field and IP packet includes a checksum field
d. Both Ethernet frame and IP packet include CRC fields
Answer: (c).Ethernet frame includes a CRC field and IP packet includes a checksum field
70. Two popular routing algorithms are Distance Vector(DV) and Link State (LS) routing. Which of the following are true?
(S1) Count to infinity is a problem only with DV and not LS routing
(S2) In LS, the shortest path algorithm is run only at one node
(S3) In DV, the shortest path algorithm is run only at one node
(S4) DV requires lesser number of network messages than LS
a. S1, S2 and S4 only
b. S1, S3 and S4 only
c. S2 and S3 only
d. S1 and S4 only
Answer: (d).S1 and S4 only
71. Host X has IP address 192.168.1.97 and is connected through two routers R1 and R2 to another host Y with IP address 192.168.1.80. Router R1 has IP addresses 192.168.1.135 and 192.168.1.110. R2 has IP addresses 192.168.1.67 and 192.168.1.155. The netmask used in the network is 255.255.255.224.
Given the information above, how many distinct subnets are guaranteed to already exist in the network?
a. 1
b. 2
c. 3
d. 6
Answer: (c).3
72. The transport layer protocols used for real time multimedia, file transfer, DNS and email, respectively are:
a. TCP, UDP, UDP and TCP
b. UDP, TCP, TCP and UDP
c. UDP, TCP, UDP and TCP
d. TCP, UDP, TCP and UDP
Answer: (c).UDP, TCP, UDP and TCP
73. Which of the following transport layer protocols is used to support electronic mail?
a. SMTP
b. IP
c. TCP
d. UDP
Answer: (c).TCP
74. Consider an instance of TCP’s Additive Increase Multiplicative Decrease (AIMD) algorithm where the window size at the start of the slow start phase is 2 MSS and the threshold at the start of the first transmission is 8 MSS. Assume that a timeout occurs during the fifth transmission. Find the congestion window size at the end of the tenth transmission.
a. 8 MSS
b. 14 MSS
c. 7 MSS
d. 12 MSS
Answer: (c).7 MSS
75. A layer-4 firewall (a device that can look at all protocol headers up to the transport layer) CANNOT
a. block entire HTTP traffic during 9:00PM and 5 :0OAM
b. block all ICMP traffic
c. stop incoming traffic from a specific IP address but allow outgoing traffic to the same IP address
d. block TCP traffic from a specific user on a multi-user system during 9:00PM and 5:00AM
Answer: (d).block TCP traffic from a specific user on a multi-user system during 9:00PM and 5:00AM
76. While opening a TCP connection, the initial sequence number is to be derived using a time-of-day(ToD) clock that keeps running even when the host is down. The low order 32 bits of the counter of the ToD clock is to be used for the initial sequence numbers. The clock counter increments once per millisecond. The maximum packet lifetime is given to be 64s. Which one of the choices given below is closest to the minimum permissible rate at which sequence numbers used for packets of a connection can increase?
a. 0.015/s
b. 0.064/s
c. 0.135/s
d. 0.327/s
Answer: (a).0.015/s
77. Which of the following system calls results in the sending of SYN packets?
a. socket
b. bind
c. listen
d. connect
Answer: (d).connect
78. In the slow start phase of the TCP congestion control algorithm, the size of the congestion window
a. does not increase
b. increases linearly
c. increases quadratically
d. increases exponentially
Answer: (d).increases exponentially
79. Which one of the following uses UDP as the transport protocol?
a. HTTP
b. Telnet
c. DNS
d. SMTP
Answer: (c).DNS
80. Let the size of congestion window of a TCP connection be 32 KB when a timeout occurs. The round trip time of the connection is 100 msec and the maximum segment size used is 2 KB. The time taken (in msec) by the TCP connection to get back to 32 KB congestion window is _________.
a. 1100 to 1300
b. 800 to 1000
c. 1400 to 1600
d. 1500 to 1700
Answer: (a).1100 to 1300
81. Which one of the following socket API functions converts an unconnected active TCP socket into a passive socket.
a. connect
b. bind
c. listen
d. accept
Answer: (c).listen
82. Packets of the same session may be routed through different paths in
a. TCP, but not UDP
b. TCP and UDP
c. UDP, but not TCP
d. Neither TCP, nor UDP
Answer: (b).TCP and UDP
83. The maximum window size for data transmission using the selective reject protocol with n-bit frame sequence numbers is:
a. 2^n
b. 2^(n-1)
c. 2^n – 1
d. 2^(n-2)
Answer: (b).2^(n-1)
84. 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
Answer: (d).End to end connectivity
85. Which of the following is not true about User Datagram Protocol in transport layer?
a. Works well in unidirectional communication, suitable for broadcast information
b. It does three way handshake before sending datagrams
c. It provides datagrams, suitable for modeling other protocols such as in IP tunneling or Remote Procedure Call and the Network File System
d. The lack of retransmission delays makes it suitable for real-time applications
Answer: (b).It does three way handshake before sending datagrams
86. Suppose two hosts use a TCP connection to transfer a large file. Which of the following statements is/are False with respect to the TCP connection?
1. If the sequence number of a segment is m, then the sequence
number of the subsequent segment is always m+1.
2. If the estimated round trip time at any given point of time
is t sec, the value of the retransmission timeout is always
set to greater than or equal to t sec.
3. The size of the advertised window never changes during the
course of the TCP connection.
4. The number of unacknowledged bytes at the sender is always
less than or equal to the advertised window
a. 3 only
b. 1 and 3 only
c. 1 and 4 only
d. 2 and 4 only
Answer: (b).1 and 3 only
87. A link has a transmission speed of 10^6 bits/sec. It uses data packets of size 1000 bytes each. Assume that the acknowledgment has negligible transmission delay, and that its propagation delay is the same as the data propagation delay. Also assume that the processing delays at nodes are negligible. The efficiency of the stop-and-wait protocol in this setup is exactly 25%. The value of the one-way propagation delay (in milliseconds) is ___________.
a. 4
b. 8
c. 12
d. 16
Answer: (c).12
88. Identify the correct order in which a server process must invoke the function calls accept, bind, listen, and recv according to UNIX socket API.
a. listen, accept, bind recv
b. bind, listen, accept, recv
c. bind, accept, listen, recv
d. accept, listen, bind, recv
Answer: (b).bind, listen, accept, recv
89. Assume that the bandwidth for a TCP connection is 1048560 bits/sec. Let α be the value of RTT in milliseconds (rounded off to the nearest integer) after which the TCP window scale option is needed. Let β be the maximum possible window size with window scale option. Then the values of α and β are
a. 63 milliseconds 65535 × 21^4
b. 63 milliseconds 65535 × 2^16
c. 500 milliseconds 65535 × 2^14
d. 500 milliseconds 65535 × 2^16
Answer: (c).500 milliseconds 65535 × 2^14
90. Consider the following statements.
I. TCP connections are full duplex.
II. TCP has no option for selective acknowledgment
III. TCP connections are message streams.
a. Only I is correct
b. Only I and II are correct
c. Only II and III are correct
d. All of I, II and III are correct
Answer: (a).Only I is correct
91. Consider a network connecting two systems located 8000 kilometers apart. The bandwidth of the network is 500 × 10^6 bits per second. The propagation speed of the media is 4 × 10^6 meters per second. It is needed to design a Go-Back-N sliding window protocol for this network. The average packet size is 10^7 bits. The network is to be used to its full capacity. Assume that processing delays at nodes are negligible. Then, the minimum size in bits of he sequence number field has to be ________.
a. 2
b. 4
c. 8
d. 16
Answer: (c).8
92. On a TCP connection, current congestion window size is Congestion Window = 4 KB. The window size advertised by the receiver is Advertise Window = 6 KB. The last byte sent by the sender is LastByteSent = 10240 and the last byte acknowledged by the receiver is LastByteAcked = 8192. The current window size at the sender is
a. 2048 bytes
b. 4096 bytes
c. 6144 bytes
d. 8192 bytes
Answer: (b).4096 bytes
93. For a host machine that uses the token bucket algorithm for congestion control, the token bucket has a capacity of 1 megabyte and the maximum output rate is 20 megabytes per second. Tokens arrive at a rate to sustain output at a rate of 10 megabytes per second. The token bucket is currently full and the machine needs to send 12 megabytes of data. The minimum time required to transmit the data is _________________ seconds.
a. 1.1
b. 0.1
c. 2.1
d. 2.0
Answer: (a).1.1
94. Consider the following statements about the timeout value used in TCP. i. The timeout value is set to the RTT (Round Trip Time) measured during TCP connection establishment for the entire duration of the connection. ii. Appropriate RTT estimation algorithm is used to set the timeout value of a TCP connection. iii. Timeout value is set to twice the propagation delay from the sender to the receiver. Which of the following choices hold?
a. (i) is false, but (ii) and (iii) are true
b. (i) and (iii) are false, but (ii) is true
c. (i) and (ii) are false, but (iii) is true
d. (i), (ii) and (iii) are false
Answer: (b).(i) and (iii) are false, but (ii) is true
95. Consider a TCP connection in a state where there are no outstanding ACKs. The sender sends two segments back to back. The sequence numbers of the first and second segments are 230 and 290 respectively. The first segment was lost, but the second segment was received correctly by the receiver. Let X be the amount of data carried in the first segment (in bytes), and Y be the ACK number sent by the receiver. The values of X and Y (in that order) are
a. 60 and 290
b. 230 and 291
c. 60 and 231
d. 60 and 230
Answer: (d).60 and 230
96. Which of the following statements are TRUE?
(S1) TCP handles both congestion and flow control
(S2) UDP handles congestion but not flow control
(S3) Fast retransmit deals with congestion but not flow control
(S4) Slow start mechanism deals with both congestion and flow control
a. S1, S2 and S3 only
b. S1 and S3 only
c. S3 and S4 only
d. S1, S3 and S4 only
Answer: (b).S1 and S3 only
97. Consider different activities related to email.
m1: Send an email from a mail client to a mail server
m2: Download an email from mailbox server to a mail client
m3: Checking email in a web browser
Which is the application level protocol used in each activity?
a. ml: HTTP m2: SMTP m3: POP
b. ml: SMTP m2: FTP m3: HTTP
c. ml: SMTP m2: POP m3: HTTP
d. ml: POP m2: SMTP m3: IMAP
Answer: (c).ml: SMTP m2: POP m3: HTTP
98. Identify the correct order in which the following actions take place in an interaction between a web browser and a web server.
1. The web browser requests a webpage using HTTP.
2. The web browser establishes a TCP connection
with the web server.
3. The web server sends the requested webpage
using HTTP.
4. The web browser resolves the domain name
using DNS.
a. 4,2,1,3
b. 1,2,3,4
c. 4,1,2,3
d. 2,4,1,3
Answer: (a).4,2,1,3
99. A graphical HTML browser resident at a network client machine Q accesses a static HTML webpage from a HTTP server S. The static HTML page has exactly one static embedded image which is also at S. Assuming no caching, which one of the following is correct about the HTML webpage loading (including the embedded image)?
a. Q needs to send at least 2 HTTP requests to S, each necessarily in a separate TCP connection to server S
b. Q needs to send at least 2 HTTP requests to S, but a single TCP connection to server S is sufficient
c. A single HTTP request from Q to S is sufficient, and a single TCP connection between Q and S is necessary for this
d. A single HTTP request from Q to S is sufficient, and this is possible without any TCP connection between Q and S
Answer: (b).Q needs to send at least 2 HTTP requests to S, but a single TCP connection to server S is sufficient
100. Consider the following statements: I. telnet, ftp and http are application layer protocols. II.l EJB (Enterprise Java Beans) components can be deployed in a J2EE (Java2 Enterprise Edition) application server. III. If two languages conform to the Common Language Specification (CLS) of the Microsoft.NET framework, then a class defined in any one of them may be inherited in the other. Which statements are true?
a. l and II only
b. II and III only
c. l and III only
d. I, II and III
Answer: (a).l and II only
101. Which of the following is/are example(s) of stateful application layer protocols?
(i) HTTP
(ii) FTP
(iii) TCP
(iv) POP3
a. (i) and (ii) only
b. (ii) and (iii) only
c. (ii) and (iv) only
d. (iv) only
Answer: (c).(ii) and (iv) only
102. Which one of the following is not a client server application?
a. Internet chat
b. Web browsing
c. E-mail
d. ping
Answer: (d).ping
103. Match the following:
(P) SMTP (1) Application layer
(Q) BGP (2) Transport layer
(R) TCP (3) Data link layer
(S) PPP (4) Network layer
(5) Physical layer
a. P – 2 Q – 1 R – 3 S – 5
b. P – 1 Q – 4 R – 2 S – 3
c. P – 1 Q – 4 R – 2 S – 5
d. P – 2 Q – 4 R – 1 S – 3
Answer: (b).P – 1 Q – 4 R – 2 S – 3
104. In the following pairs of OSI protocol layer/sub-layer and its functionality, the INCORRECT pair is
a. Network layer and Routing
b. Data Link Layer and Bit synchronization
c. Transport layer and End-to-end process communication
d. Medium Access Control sub-layer and Channel sharing
Answer: (b).Data Link Layer and Bit synchronization
105. Choose the best matching between Group 1 and Group 2.
Group-1 Group-2
P. Data link 1. Ensures reliable transport of data over a physical point-to-point link
Q. Network layer 2. Encoder/decodes data for physical transmission
R. Transport layer 3. Allows end-to-end communication between two processes
4. Routes data from one network node to the next
a. 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
Answer: (a).P-1, Q-4, R-3
106. 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
Answer: (b).A bridge uses IP addresses while a router uses MAC addresses
107. Host A sends a UDP datagram containing 8880 bytes of user data to host B over an Ethernet LAN. Ethernet frames may carry data up to 1500 bytes (i.e. MTU = 1500 bytes). Size of UDP header is 8 bytes and size of IP header is 20 bytes. There is no option field in IP header. How may total number of IP fragments will be transmitted and what will be the contents of offset field in the last fragment?
a. 6 and 925
b. 6 and 7400
c. 7 and 1110
d. 7 and 8880
Answer: (c).7 and 1110
108. Since it is a network that uses switch, every packet goes through two links, one from source to switch and other from switch to destination. Since there are 10000 bits and packet size is 5000, two packets are sent. Transmission time for each packet is 5000 / 10^7 bits per second links. Each link has a propagation delay of 20 microseconds. The switch begins forwarding a packet 35 microseconds after it receives the same. If 10000 bits of data are to be transmitted between the two hosts using a packet size of 5000 bits, the time elapsed between the transmission of the first bit of data and the reception of the last bit of the data in microseconds is _________.
a. 1075
b. 1575
c. 2220
d. 2200
Answer: (b).1575
109. Which one of the following statements is FALSE?
a. TCP guarantees a minimum communication rate
b. TCP ensures in-order delivery
c. TCP reacts to congestion by reducing sender window size
d. TCP employs retransmission to compensate for packet loss
Answer: (a).TCP guarantees a minimum communication rate
110. Which one of the following statements is FALSE?
a. HTTP runs over TCP
b. HTTP describes the structure of web pages
c. HTTP allows information to be stored in a URL
d. HTTP can be used to test the validity of a hypertext link
Answer: (b).HTTP describes the structure of web pages
111. A serial transmission Ti uses 8 information bits, 2 start bits, 1 stop bit and 1 parity bit for each character. A synchronous transmission T2 uses 3 eight bit sync characters followed by 30 eight bit information characters. If the bit rate is 1200 bits/second in both cases, what are the transfer rates of Ti and T2?
a. 100 characters/sec, 153 characters/sec
b. 80 characters/sec, 136 characters/sec
c. 100 characters/sec, 136 characters/sec
d. 80 characters/sec, 153 characters/sec
Answer: (c).100 characters/sec, 136 characters/sec
112. In a sliding window ARQ scheme, the transmitter's window size is N and the receiver's window size is M. The minimum number of distinct sequence numbers required to ensure correct operation of the ARQ scheme is
a. min (M, N)
b. max (M, N)
c. M + N
d. MN
Answer: (c).M + N
113. Which one of the following protocols is NOT used to resolve one form of address to another one?
a. DNS
b. ARP
c. DHCP
d. RARP
Answer: (c).DHCP
114. Identify the correct sequence in which the following packets are transmitted on the network by a host when a browser requests a webpage from a remote server, assuming that the host has just been restarted.
a. HTTP GET request, DNS query, TCP SYN
b. DNS query, HTTP GET request, TCP SYN
c. DNS query, TCP SYN, HTTP GET request
d. TCP SYN, DNS query, HTTP GET request
Answer: (c).DNS query, TCP SYN, HTTP GET request
115. A firewall is to be configured to allow hosts in a private network to freely open TCP connections and send packets on open connections. However, it will only allow external hosts to send packets on existing open TCP connections or connections that are being opened (by internal hosts) but not allow them to open TCP connections to hosts in the private network. To achieve this the minimum capability of the firewall should be that of
a. A combinational circuit
b. A finite automaton
c. A pushdown automaton with one stack
d. A pushdown automaton with two stacks
Answer: (d).A pushdown automaton with two stacks
116. Which protocol will be used to automate the IP configuration mechanism which includes IP address, subnet mask, default gateway, and DNS information?
a. SMTP
b. DHCP
c. ARP
d. TCP/IP
Answer: (b).DHCP
117. In Go–back 3 flow control protocol every 6th packet is lost. If we have to send 11 packets. How many transmissions will be needed ?
a. 10
b. 17
c. 12
d. 9
Answer: (b).17
118. What will be the total minimum bandwidth of the channel required for 7 channels of 400 kHz bandwidth multiplexed together with each guard band of 20 kHz?
a. 2800 khz
b. 2600 khz
c. 3600 khz
d. 2920 khz
Answer: (d).2920 khz
119. Which of the following is false:
a. Digital signature is used to verify that a message is authentic
b. Digital certificate is issued by a third party
c. Digital certificate ensures integrity of the message
d. Digital signature ensures non-repudiation
Answer: (c).Digital certificate ensures integrity of the message
120. The subnet mask for a particular network is 255.255.31.0. Which of the following pairs of IP addresses could belong to this network?
a. 172.57.88.62 and 172.56.87.233
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
Answer: (d).128.8.129.43 and 128.8.161.55
121. 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 : 1000 bytes B : 100 bytes C : 1000 bytes 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).
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
Answer: (d).260
122. 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 : 1000 bytes B : 100 bytes C : 1000 bytes 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).
What is the rate at which application data is transferred to host HC? Ignore errors, acknowledgements, and other overheads.
a. 325.5 Kbps
b. 354.5 Kbps
c. 409.6 Kbps
d. 512.0 Kbps
Answer: (b).354.5 Kbps
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