FINALTERM EXAMINATION Fall 2008
CS610- Computer Network
Time: 120 min
M a r k s: 70
Question No: 1 ( M a r k s: 1 ) http://vuzs.net
Computer networks are often called -------------- because they use packet technology.
► Ethernet
► Switch networks
► Packet networks
► None of the given
Question No: 2 ( M a r k s: 1 ) http://vuzs.net
A network uses a ------arranges for computers to be connected in a closed loop.
► Star Topology
► Ring Topology
► Bus Topology
► None of the given
In a ring topology each computer is connected to other thorough a ring
Question No: 3 ( M a r k s: 1 ) http://vuzs.net
An ------------method, the network hardware designers specify how type information is included in the frame and the value use to identify various frame types.
► Explicit frame type
► Ideal frame type
► Implicit frame type
► None of the given
EXPLICIT FRAME TYPE:
In this type the identifying value is included with frame describes types of
included data.
Question No: 4 ( M a r k s: 1 ) http://vuzs.net
An interface for thin Ethernet must have an ____________ connector , and must generate signals according to the_____________ specification.
► RJ-45, 10 Base T
► RJ-45, 10 Base 5
► BNC, 10 Base 2
► BNC, 10 Base T
Question No: 5 ( M a r k s: 1 ) http://vuzs.net
A Bridge forwards or filters a frame by comparing the information in its address table to the frame’s_________
► Layer 2 source address
► Source node’s physical address
► Layer 2 destination address
► Layer 3 destination address
Question No: 6 ( M a r k s: 1 ) http://vuzs.net
Most WAN systems include a mechanism that can be used to eliminate the common case of duplication routing is called___________
► Hierarchal address
► Default route
► Shortest path
► None of the given
Most WAN systems include a mechanism that can be used to eliminate the common case of duplication routing is called Default route. The mechanism allows a single entry in a forwarding table to replace a long list of entries that have the same next hope value
Question No: 7 ( M a r k s: 1 ) http://vuzs.net
________ of TCP/IP layering model, corresponds to basic network hardware.
► Physical Layer
► Network Interface Layer
► Internet Layer
► Transport Layer
LAYER 1:
Corresponds to basic network hardware layer in OSI
Question No: 8 ( M a r k s: 1 ) http://vuzs.net
_______ protocols of TCP/IP layering model specify how to ensure reliable transfer.
► Physical Layer
► Network Interface Layer
► Internet Layer
► Transport Layer
Fourth layer which is transport layer will take care of reliable transfer
Question No: 9 ( M a r k s: 1 ) http://vuzs.net
________is called an end-to-end protocol because it provide a connection directly from an application on one computer to an application on a remote computer.
► IP
► UDP
► TCP
► None of the given
UDP has the following characteristics.
It is an end-to-end protocol. It provides application-to-application communication.
Question No: 10 ( M a r k s: 1 )
____________ uses distance vector approach to define routing
► BGP
► OSPF
► RIP
► None of the given
DISTANCE-VECTOR ROUTING:
• It is very simple to implement.
• Packet switch updates its own routing table first.
• It is used in RIP
Question No: 11 ( M a r k s: 1 ) http://vuzs.net
_______ is ideal in a situation where the group is small and all members are attached to contiguous Local Area Networks.
► Flood-and -Prune
► Configuration-and -Tunneling
► Core-Based Discovery
► None of the given
FLOOD-AND-PRUNE:
Flood-and-prune is ideal in a situation where the group is small and all members
are attached to contiguous Local Area Networks.
Question No: 12 ( M a r k s: 1 ) http://vuzs.net
Router that decrements TTL to __ sends ICMP time exceeded message, with router’s address as source address
► 3
► 2
► 1
► 0
outer that decrements TTL to 0 sends ICMP time exceeded message, with router’s
address as source address
Question No: 13 ( M a r k s: 1 ) http://vuzs.net
Protocol addresses are abstractions provided by ___________.
► hardware
► software
► operating system
► internet
PROTOCOL ADDRESSES AND PACKET DELIVERY:
Protocol addresses are abstractions provided by software
Question No: 14 ( M a r k s: 1 ) http://vuzs.net
Although message exchange can be used to bind addresses, sending a request for each binding is hopelessly inefficient.
► True
► False
CASHING ARP RESPONSES:
Although message exchange can be used to bind addresses, sending a request for
each binding is hopelessly inefficient
Question No: 15 ( M a r k s: 1 ) http://vuzs.net
ARP is almost always used to bind a ___-bit IP address to a ___-bit Ethernet address.
► 32, 48
► 24, 32
► 32, 64
► 32, 128
ARP is almost always used to bind a 32-bit IP address to a 48-bit Ethernet address
Question No: 16 ( M a r k s: 1 ) http://vuzs.net
In the 1970s large organizations began to acquire multiple networks. Each network in the organization formed island. Employees needed to choose a computer appropriate for each task. So they needed multiple screens, keyboards and computers.
► False
► True
Question No: 17 ( M a r k s: 1 ) http://vuzs.net
In which method of Address Resolution Protocol the protocol address is determined by hardware address?
Were "T" stands for Table lookup, "C" for Closed-form Computation and "D" for Data Exchange?
Features
| Types of Resolution |
Use full with any hardware | T |
Address change affects all hosts | T |
Protocol address is determined by hardware address | C |
► T
► D
► C
► T, C
Question No: 18 ( M a r k s: 1 ) http://vuzs.net
The general form of an IP datagram is with a header followed by data. The header contains information that controls where and how the datagram is to be sent.
► True
► False
Header contains all information needed to deliver datagram to the destination
computer. It contains:
• Destination address
• Source address
• Identifier
• Other delivery information
Question No: 19 ( M a r k s: 1 ) http://vuzs.net
To save traffic, an EGP does not summarize routing information from the autonomous system before passing it to another autonomous system.
► True
► False
Question No: 20 ( M a r k s: 1 ) http://vuzs.net
Which of the following is a correct representation of the IPv6?
► 105.220.136.100.255.255.255.255.0.0.18.128.140.10.255.255
► 105.220.136.100.255.255.255.256.0.0.18.128.140.10.255.255
► 105.220.136.100.255.255.255.255.0.0.18.128.140.10.255.255.256
► 105.220.136.100.255.255.255.255.0.0.18.128.140.10.255
Question No: 21 ( M a r k s: 2 )
Is there a comparison between TCP/IP reference model and OSI reference model.
Both the TCP/IP and OSI are international standards for data communication. Both use the concept of protocol layering. These are the conceptual tools that is often used to show how various protocols and technologies fit together to implement networks. The functions that the model represents are much the same. This means that the TCP/IP and the OSI models are really quite similar in nature even if they don't carve up the network functionality pie in precisely the same way. There is a fairly natural correspondence between the TCP/IP and OSI layers; it just isn't always a “one-to-one” relationship. Since the OSI model is used so widely, it is common to explain the TCP/IP architecture both in terms of the TCP/IP layers and the corresponding OSI layers
Question No: 22 ( M a r k s: 2 )
How can a datagram be transmitted across a physical network that does not understand the datagram format?
Encapsulate!
The network interface layer encapsulates an entire datagram in the data area of a hardware frame.
The network hardware ignores the datagram format.
The hardware treats a frame containing a datagram like any other frame.
The sender places a frame type in the frame header indicating that the frame contains a datagram.
The receiver reads the frame type and knows the frame contains a datagram.
Question No: 23 ( M a r k s: 2 )
What is the basic concept of Twice NAT (Network Address Translation)?
Twice NAT is another variant of NAT. it is used with site that runs server. In this process NAT box is connected to Domain Name.
Question No: 24 ( M a r k s: 3 )
What format is used for an internet packet?
Question No: 25 ( M a r k s: 3 )
“To achieve a hierarchy, OSPF allows an autonomous system to be partitioned for routing purposes”. Does this feature make OSPF more complex or powerful?
Question No: 26 ( M a r k s: 3 )
Why does IPv6 use separate Extension Headers?
IPv6 use separate Extension Headers. Fragmentation information is kept in separate extension header. Each fragment has base header and (inserted) fragmentation header. Entire datagram including originalheader may be fragmented.
Question No: 27 ( M a r k s: 5 )
Consider the IP addresses: 178.200.127.5 and the corresponding subnet masks 255.255.255.0, then find out the following:
a. The number of bits used for subnetting (Answer 8 bits)
b. Total number of host in the subnet (Answer 254 )
= 2^8 = 256-2 = 254 ( 8 bits are used for host and -2 is used for broadcast and netwrok ID)
c. The network address of the subnet. (Answer 178.200.127.0)
(By Zubair ,vuzs.net, feb11)
Start by using 256, the subnet mask, which is 256-0=256. The first subnet is 8. The next subnet would be 16, then 24, and then 32. This host is in the 24 subnet, the broadcast address is 31, and the valid host range is 25 through 31. See Chapter 3 for more information on IP addressing.
Here is the online calculator for subnetting
http://www.subnetmask.info/
NOTE. This is just for concept not included in the answer
The subnet mask determines what portion of the TCP/IP address represents your network and what portion can be used for your hosts. The network number represents the street I live on, and the host portion is used for the numbers on all the houses on my street.
A subnet mask of 255.255.255.0 means that the first three octets of the address will be used for the network, and thus our network number is192.168.1. This means we can have 254 computers on this network, because the fourth octet is not being used by the network portion of the address. We know this because of the 0 in the subnet mask (255.255.255.0).
Question No: 28 ( M a r k s: 5 )
How does IP software reassemble fragments that arrive out of order?
A unique ID number of each outgoing datagram
When a router fragments the datagram, the router copies the ID number into each fragment.
The fragment OFFSET field tells a receiver how to order fragmentswithin a given datagram
The process of creating a copy of the original datagram from fragments is called reassembly.
Question No: 29 ( M a r k s: 5 )
Write down the comparison of Distance- vector and Link – state algorithm?
COMPARISON:
DISTANCE-VECTOR ROUTING:
• It is very simple to implement.
• Packet switch updates its own routing table first.
• It is used in RIP.
LINK-STATE ALGORITHM:
• It is much more complex.
• Switches perform independent computations.
• It is used in OSPF.
Question No: 30 ( M a r k s: 10 )
Descibe in detail what is the purpose of the following table? What sort of information can be extracted?
First Four Bits Of address | Table index in decimal | Class of Address |
0000 | 0 | A |
0001 | 1 | A |
0010 | 2 | A |
0011 | 3 | A |
0100 | 4 | A |
0101 | 5 | A |
0110 | 6 | A |
0111 | 7 | A |
1000 | 8 | B |
1001 | 9 | B |
1010 | 10 | B |
1011 | 11 | B |
1100 | 12 | C |
1101 | 13 | C |
1110 | 14 | D |
1111 | 15 | E |
The table shows in the figure, how the class of address can be computed.
Question No: 31 ( M a r k s: 10 )
List down and describe atleast five charachteristics of Routing Information Protocol.
ROUTING INFORMATION PROTOCOL (RIP):
It has the following characteristics:
"It is used for routing within an autonomous system (IGP).
"Hop Count Metric: RIP measures distance in network hops, where each network
between the source and destination counts as a single hop.
"It uses UDP for all message transmissions.
"RIP is used over LAN. Version 1 of RIP uses hardware broadcast and version 2 allows
delivery via multicast.
"It can be used to advertise default route propagation. An organization can use RIP to
install a default route in each router.
"It uses distance vector algorithm.
"RIP allows hosts to listen passively and update its routing table
