CS2302 COMPUTER NETWORKS
UNIT I
Network architecture – layers – Physical links – Channel access on links – Hybrid
multiple access techniques - Issues in the data link layer - Framing – Error correction and
detection – Link-level Flow Control
INTRODUCTION TO DATA COMMUNICATIONS:
It is the exchange of data between two devices through some transmission
medium.
Types:
1. Local
2. Remote
1. Local:
If the devices are restricted in a geographical area.
2. Remote:
If the devices are farther away without any geographical restriction.
Fundamental Characteristics:
1. Delivery
2. Accuracy
3. Timeliness
Components:
Data communication systems are made up of five components.
1. Message
2. sender
3. Receiver
4. Medium
5. Protocol
1. Message:
This is the information to be communicated. It can consist of text, numbers,
pictures, sound or video or any combination of these.
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2. Sender:
It is the device that sends the data message. It may be a computer, workstation,
telephone handset, video camera…
3. Receiver:
It is the device that receives the message. It may be a computer, workstation,
telephone handset, television…
4. Medium:
It is the physical path which a message travels from sender to receiver. It may
consist of twisted pair wire, coaxial cable, fiber optic cable, laser or radio waves.
5. Protocol:
It is a set of rules that governs data communication. It is a agreement between the
communication devices.
NETWORKS:
A network is a set of devices connected by a media link. Devices often referred to
as nodes can be a computer, printer, or any other devices capable of sending/ receiving
data.
Distributed processing:
Here tasks are divided among multiple computers. Each separate computer
handles a subset.
Advantages:
1. Security/ Encapsulation
2. Distributed database
3. Faster problem solving
4. Security through redundancy
5. collaborative processing
Network Criteria:
A network must meet a number of criteria to be considered as effective and
efficient.
The criteria are,
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1. Performance
2. Reliability
3. Security
1. Performance:
The performance can be measured by two times are,
I. Transit time
II. Response time
I. Transit time:
It is the amount of time required for a message to travel from one device to
another device.
II. Response time:
It is the elapsed time between an inquiry and a response.
The performance can be measured by number factors are,
i. Number of user
ii. Type of transition medium
iii. Hardware
iv. Software
i. Number of user:
Large number of concurrent users produces slow response time and heavy traffic
loads.
ii. Type of transition medium:
The medium defines the speed of data travel.
iii. Hardware:
The type of hardware can affect the speed and capacity of transmission.
iv. Software:
The software can affect speed and reliability of a network link.
2. Reliability:
The reliability is measured by frequency to failure, the time it takes a link to
recover from a failure and the network‟s robustness in a catastrophe.
i. Frequency of Failure:
A network that fails often.
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ii. Recovery time:
How much time it takes to recover service after a failure has occurred?
iii. Catastrophe:
Failures due to such reasons are fire, earthquake, theft…
3. Security:
It refers to protecting data from unauthorized access and viruses.
i. Unauthorized Access:
Sensitive data must be protected from unauthorized access. Protection can be
done by user identification and passwords at the lowest level. At the highest level,
encryption techniques may use.
ii. Viruses:
A virus is an illicitly introduced code that damages the system.
CATEGORIES OF NETWORKS:
There are three primary categories are,
1. Local area network.
2. Metropolitan area network.
3. Wide area network.
1. Local Area Network:
They are usually privately owned and link the devices in a single office, building
and campus. Currently LAN size is limited to a few kilometers. It may be from two PC‟s
to throughout a company.
The most common LAN topologies are bus, ring and star. They have data rates
from 4 to 16 Mbps. Today the speed is on increasing and can reach 100 mbps.
2. Metropolitan Area Network:
They are designed to extend over an entire city. It may be a single network or
connecting a number of LANs into a large network. So the resources are shared between
LANs. Example of MAN is, telephone companies provide a popular MAN service called
switched multi megabit data service (SMDS).
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3. Wide Area Network:
It provides a long distance transmission of data, voice, image and video
information over a large geographical are like country, continent or even the whole
world.
TYPE OF CONNECTION:
There are two types are,
1. Point to point
2. Multi point
Download this Visit: www.annauniversityplus.com
UNIT I
Network architecture – layers – Physical links – Channel access on links – Hybrid
multiple access techniques - Issues in the data link layer - Framing – Error correction and
detection – Link-level Flow Control
INTRODUCTION TO DATA COMMUNICATIONS:
It is the exchange of data between two devices through some transmission
medium.
Types:
1. Local
2. Remote
1. Local:
If the devices are restricted in a geographical area.
2. Remote:
If the devices are farther away without any geographical restriction.
Fundamental Characteristics:
1. Delivery
2. Accuracy
3. Timeliness
Components:
Data communication systems are made up of five components.
1. Message
2. sender
3. Receiver
4. Medium
5. Protocol
1. Message:
This is the information to be communicated. It can consist of text, numbers,
pictures, sound or video or any combination of these.
www.annauniversityplus.com
Page 1 of 122
www.Annauniversityplus.com
2. Sender:
It is the device that sends the data message. It may be a computer, workstation,
telephone handset, video camera…
3. Receiver:
It is the device that receives the message. It may be a computer, workstation,
telephone handset, television…
4. Medium:
It is the physical path which a message travels from sender to receiver. It may
consist of twisted pair wire, coaxial cable, fiber optic cable, laser or radio waves.
5. Protocol:
It is a set of rules that governs data communication. It is a agreement between the
communication devices.
NETWORKS:
A network is a set of devices connected by a media link. Devices often referred to
as nodes can be a computer, printer, or any other devices capable of sending/ receiving
data.
Distributed processing:
Here tasks are divided among multiple computers. Each separate computer
handles a subset.
Advantages:
1. Security/ Encapsulation
2. Distributed database
3. Faster problem solving
4. Security through redundancy
5. collaborative processing
Network Criteria:
A network must meet a number of criteria to be considered as effective and
efficient.
The criteria are,
www.annauniversityplus.com
Page 2 of 122
www.Annauniversityplus.com
1. Performance
2. Reliability
3. Security
1. Performance:
The performance can be measured by two times are,
I. Transit time
II. Response time
I. Transit time:
It is the amount of time required for a message to travel from one device to
another device.
II. Response time:
It is the elapsed time between an inquiry and a response.
The performance can be measured by number factors are,
i. Number of user
ii. Type of transition medium
iii. Hardware
iv. Software
i. Number of user:
Large number of concurrent users produces slow response time and heavy traffic
loads.
ii. Type of transition medium:
The medium defines the speed of data travel.
iii. Hardware:
The type of hardware can affect the speed and capacity of transmission.
iv. Software:
The software can affect speed and reliability of a network link.
2. Reliability:
The reliability is measured by frequency to failure, the time it takes a link to
recover from a failure and the network‟s robustness in a catastrophe.
i. Frequency of Failure:
A network that fails often.
www.annauniversityplus.com
Page 3 of 122
www.Annauniversityplus.com
ii. Recovery time:
How much time it takes to recover service after a failure has occurred?
iii. Catastrophe:
Failures due to such reasons are fire, earthquake, theft…
3. Security:
It refers to protecting data from unauthorized access and viruses.
i. Unauthorized Access:
Sensitive data must be protected from unauthorized access. Protection can be
done by user identification and passwords at the lowest level. At the highest level,
encryption techniques may use.
ii. Viruses:
A virus is an illicitly introduced code that damages the system.
CATEGORIES OF NETWORKS:
There are three primary categories are,
1. Local area network.
2. Metropolitan area network.
3. Wide area network.
1. Local Area Network:
They are usually privately owned and link the devices in a single office, building
and campus. Currently LAN size is limited to a few kilometers. It may be from two PC‟s
to throughout a company.
The most common LAN topologies are bus, ring and star. They have data rates
from 4 to 16 Mbps. Today the speed is on increasing and can reach 100 mbps.
2. Metropolitan Area Network:
They are designed to extend over an entire city. It may be a single network or
connecting a number of LANs into a large network. So the resources are shared between
LANs. Example of MAN is, telephone companies provide a popular MAN service called
switched multi megabit data service (SMDS).
www.annauniversityplus.com
Page 4 of 122
www.Annauniversityplus.com
3. Wide Area Network:
It provides a long distance transmission of data, voice, image and video
information over a large geographical are like country, continent or even the whole
world.
TYPE OF CONNECTION:
There are two types are,
1. Point to point
2. Multi point
Download this Visit: www.annauniversityplus.com
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