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VU CS601- Data Communication mid term examination 2006

VU CS601- Data Communication Mid Term Examination 2006



Question # 1


Computers on the Internet are connected by various networks. The complexity of networking is addressed

by dividing the Internet into many layers. The International Organization for Standardization (ISO)

developed a 7 layer network model (Application, Presentation, Session, Transport, Network, Data Link

and Physical layers) long before the Internet has gained popularity. The 7 layer model has been revised to

a 5 layer TCP/IP based Internet Model (Application, Transport, Internet, Network, and Physical layers).

7-Layer ISO Model 5-Layer Internet Model

7. Application Layer: provides user services

such as e-mail and file transfer, synchronization of

users, log-in and log-out procedures.

Application Layer: Application layer defines

generic available network applications or services

the Internet can support. See the table below for

widely used network applications and the

corresponding network protocols.

Application Protocol:


Email: SMTP

File Transfer: FTP

6. Presentation Layer: format and code

conversion services. ——————————

5. Session Layer: establishes, manages, and

terminates sessions. ——————————

4. Transport layer: ensures reliable transmission

of data.

Transmission Control Protocol (TCP) Layer: This

layer concerns how data can be reliably transferred

over the network. UDP (User Datagram Protocol) is

used when speed of data transmission is more

important than reliability.

3. Network Layer: Responsible for the routing of

data (packets) through the network.

Internet Protocol (IP) Layer: This layer handles

address and routing of the network.

2. Data Link Layer: responsibility for

information between adjacent nodes.

Local Network Access Protocol (NAP) Layer:

This is the part of your system that is concerned with

how you communicate with your local network,

whether is Ethernet or token ring.

1. Physical Layer: mechanical, electrical and

functional interface.

Physical Layer: This is the physical connection

whether using a Network Interface Card (NIC) or

with a modem to connect to the local network.


Question # 2


(a) The “Presentation layer” (6th layer) provides the facility to format and code conversion services.

(b) The “Session Layer” (5th layer) Establishes, manages, and terminates sessions.

(c) The “Transport Layer” (4th Layer) Ensures reliable transmission of data.

(d) The “Application layer” (7th Layer) Log-in and log-out procedures.

(e) The “Presentation Layer” (6th Layer) Provides independence from differences in data representation.


Question # 3


S.No Port Address Physical Address Logical Address

1 A port address is an address

assigned by the CPU (0-FFFF)

that can be accessed for i/o

read/write like RAM.

A physical address is an

address in a network card.

A logical address is an address

similar but its like the

information you would use to

get to a physical address.

2 There are many applications

running on the computer. Each

application run with a port

number (logically) on the

computer. This port number for

application is decided by the

Kernel of the OS. This port

number is called port address.

Physical address, also real

address, or binary address, is

the memory address that is

electronically (in the form of

binary number) presented on

the computer address bus

circuitry in order to enable the

data bus to access a particular

storage cell of main memory.

Logical address is the address

at which a memory location

appears to reside from the

perspective of an executing

application program.

3 The port address is used to

identify the particular

application running on the

destination machine.

Physical memory may be

mapped to different logical

addresses for various purposes

This address can be changed

by changing the host position

on the network. So it is called

logical address.

4 A port address is an applicationspecific

or process-specific

software construct serving as a

communications endpoint.

It is used by Transport Layer


A Physical address is a 48-bit

flat address burned into the

ROM of the NIC card which is

a Layer1 device of the OSI


A Logical address is a 32- bit

address assigned to each

system in a network This

works in Layer-3 of OSI

Model. This would be

generally the IP address.

5 Port Address: A Central

Processing Unit (CPU) assigns

a unique ID to the Input or

Output that are attached with a

computer. This unique ID of

Input and Output devices is

called a “Port Address”.

Obtaining a physical address

that is ultimately needed to

perform an operation. All

instructions executing at the

machine level require physical

memory storage or network

node address when referencing

the actual hardware.

The logical address (name) is

turned into a physical address

(machine number) either by the

recipient node or by a router

that maintains a list of address

translations. This is through

ARP (Address-Resolution



1. Logical Address: This address is used by network layer (3rd Layer) to identify a particular

network (source to destination) among the networks.

2. Physical Address: A Physical address is a 48-bit flat address burned into the ROM of the NIC

card which is a Physical Layer (1st Layer) device of the OSI model


3. Port Address: In computer networking, a port address is part of the addressing information used

to identify the senders and receivers of messages. Port address is most commonly used with

TCP/IP connections. This address is used by network layer (3rd Layer).

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Question No. 20

Marks : 01

Marks : 01

Marks : 01

When dot product of two vectors equals zero, this implies that the two vectors are:





parallel to each other

orthogonal (perpendicular) to each other.

intersect each other

equal to each other

Question No. 21

Marks : 04

What is meant by Trivial Accept?

Question No. 22

The Boundary Fill and Flood Fill algorithms:

Marks : 0





Must use 4-connected approach

Must use 8-connected approach

May use 4-connected or 8-connected approach

Must not use recursive approach

VU CS601- Data Communication Mid Term Examination 2006

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