5. NETWORKS:
A network is a set of devices (often referred to as nodes) connected by
communication links.
Network Criteria:
⢠Performance (response time)
⢠Reliability (Frequency of failure)
⢠Security (Protecting data)
6. Physical Structures:
Type of Connection
Point to Point - Single transmitter and receiver
Multipoint - Multiple recipients of single transmission
8. ⢠Point -to âPoint connection
⢠In simplex required links :
n(n-1)
⢠A fully connected mesh can
have :
n(n-1)/2 physical.
(n-1) i/o ports.
Mesh topology
Figure- A fully connected mesh topology
(five devices)
9. Advantages:
1. Reduces traffic problem.
2. Robust
3. Privacy and security.
4. Easy to fault identification and fault isolation
Disadvantages:
1. Large number of ports and cabling.
2. Highly expensive
10. Star Topology
⢠Point-to-Point link to the central.
⢠No direct traffic between devices.
⢠The transmission are occurred only
through the central "hub".
⢠No of links: n
Figure - A star topology connecting
four stations
11. Advantages :
1.Less expensive then mesh .
2.Less cabling is need then mesh.
3.Robustness.
4. No disruptions to the network.
Disadvantages:
1.Cabling large compared to ring & bus.
2.Dependency
12. Bus Topology
⢠Multipoint connection.
⢠Here one long cable act as a
backbone to link all the devices are
connected to the backbone by drop
lines and taps.
⢠This allows only one device to
transmit at a time.
Figure - A bus topology connecting four
stations
13. Advantages:
1. Ease of installation
2. Less cabling
.
Disadvantages:
1.Difficult reconfiguration and fault isolation.
2.Difficult to add new devices.
3.If any fault in backbone can stops all transmission
14. Ring Topology
⢠Here each device has a dedicated
connection with two devices on either
side.
⢠Each device have repeater.
⢠To add or delete a device requires
changing only two connections.
⢠No of links : n
Figure - A ring topology connecting
four stations
15. Advantages:
1. Easy to install.
2. Easy to reconfigure.
3. Fault identification is easy.
Disadvantages:
1. Unidirectional traffic.
2. Break in a single ring can break entire network.
16. THE OSI MODEL
⢠An ISO standard that covers all aspects of network communications is
the Open Systems Interconnection (OSI) model.
⢠It was first introduced in the late 1970s.
19. Physical Layer
⢠Representation of bits
⢠Data Rate
⢠Synchronization
⢠Transmission mode
⢠Topology
Note- The physical layer is responsible for movements of individual bits
from one hop (node) to the next.
20. Data link Layer
⢠Framing
⢠Physical Address
⢠Flow Control
⢠Error Control
⢠Access Control
Note- The data link layer is responsible for moving frames from
one hop (node) to the next.
21. Network layer
⢠Routing
⢠Fragmentation
⢠Logical Addressing
Note-The network layer is responsible for the delivery of individual
packets from the source host to the destination host.
22. Transport Layer
⢠Segmentation and Reassembly
⢠Connection control
Note-The transport layer is responsible for the delivery of a message from
one process to another.