2. Topology
Topology refers to the layout of connected
devices on a network.
Here, some logical layout of topology.
Mesh
Star
Bus
Ring
Tree and Hybrid
4. Mesh Topology
Here every device has a point to point link to
every other device.
Node 1 node must be connected with n-1
nodes.
A fully connected mesh can have n(n-1)/2
physical channels to link n devices.
It must have n-1 I/O ports.
5. Mesh Topology
Advantages:
1. They use dedicated links so each link can only
carry its own data load. So traffic problem can be
avoided.
2. It is robust. If any one link get damaged it cannot
affect others.
3. It gives privacy and security.(Message travels
along a dedicated link)
4. Fault identification and fault isolation are easy.
8. Mesh Topology
Disadvantages:
1. The amount of cabling and the number of I/O ports
required are very large. Since every device is
connected to each devices through dedicated links.
2. The bulk of wiring is larger then the available space.
3. Hardware required to connected each device is
highly expensive.
10. Star Topology
Here each device has a dedicated point-to-point link to
the central controller called “Hub”(Act as a
Exchange).
There is no direct traffic between devices.
The transmission are occurred only through the
central “hub”.
When device 1 wants to send data to device 2; First
sends the data to hub. Which then relays the data to
the other connected device.
13. Star Topology
Advantages:
1. Less expensive then mesh since each device is
connected only to the hub.
2. Installation and configuration are easy.
3. Less cabling is need then mesh.
4. Robustness.(if one link fails, only that links is affected.
All other links remain active)
5. Easy to fault identification & to remove parts.
6. No distruptions to the network then connecting(or)
removing devices.
14. Star Topology
Disadvantages:
1. Even it requires less cabling then mesh when
compared with other topologies it still large.(Ring or
bus).
2. Dependency(whole n/w dependent on one single
point(hub). When it goes down. The whole system is
dead.
17. Asynchronous Transfer Mode
By the mid 1980s, three types of communication
networks had evolved.
The telephone network carries voice calls, television
network carries video transmissions, and newly
emerging computer network carries data.
Telephone companies realized that voice
communication was becoming a commodity service
and that the profit margin would decrease over time.
They realized that data communication was
increasing.
The telecommunication industry decided to expand its
business by developing networks to carry traffic other
than voice.
18. Asynchronous Transfer Mode (ATM) is a switching technique for
telecommunication networks. It uses asynchronous time-division
multiplexing,[1][2] and it encodes data into small, fixed-sized cells.
ATM differs from networks such as the Internet or Ethernet LANs that use variable
sized packets or frames. ATM provides data link layer services that run
over OSI Layer 1 physical links. ATM has functional similarity with
both circuit switched networking and small packet switched networking.
This makes it a good choice for a network that must handle both traditional high-
speed data traffic (e.g., file transfers), and real-time, low-latency content such as
voice and video.
Asynchronous Transfer Mode
20. ATM is more complex, but this complexity allows to give guarantees as to data
rate, maximum delay, and jitter.
These are usually called Quality of Service.
JITTER:
In voice over IP (VoIP), jitter is the variation in the time between packets
arriving, caused by network congestion, timing drift, or route changes. A jitter
buffer can be used to handle jitter.
Jitter is the deviation in or displacement of some aspect of the pulses in a high-
frequency digital signal.
Quality of Service or QoS is a method of providing better service for selected
traffic types over various types of packet-switched networks.
21. Advantages
Universality
Mixed traffic types, real-time and non-real-time
Scalability
LANs, MANs, WANs, WLANs
Efficient use of network resources Bandwidth on
demand concept
Simplified network infrastructure
22. Disadvantages
ATM has not been widely accepted. Although some phone
companies still use it in their backbone networks.
The expense, complexity and lack of interoperability with
other technologies have prevented ATM from becoming
more prevalent.
23. Disadvantages
Complexity of QoS: The complexity of the specification
makes implementation cumbersome and difficult. Many
implementations do not support the full standard.
Assumption of Homogeneity: ATM is designed to be a
single, universal networking system. There is minimal
provision for interoperating with other technologies
24. Bus Topology
A bus topology is multipoint.
Here one long cable act as a backbone to link all the
devices are connected to the backbone by drop lines
and taps.
Drop line- is the connection b/w the devices and the
cable.
Tap- is the splitter that cut the main link.
This allows only one device to transmit at a time.
29. Bus Topology
A device want to communicate with other device on
the n/ws sends a broadcast message onto the wire all
other devices see.
But only the intended devices accepts and process the
message.
30. Bus Topology
Advantages:
1. Ease of installation
2. Less cabling
Disadvantages:
1. Difficult reconfiguration and fault isolation.
2. Difficult to add new devices.
3. Signal reflection at top can degradation in quality.
4. If any fault in backbone can stops all transmission.
32. Ring Topology
Here each device has a dedicated connection with two
devices on either side.
The signal is passed in one direction from device to
device until it reaches the destination and each device
have repeater.
When one device received signals instead of intended
another device, its repeater then regenerates the data
and passes them along.
To add or delete a device requires changing only two
connections.
36. Ring Topology
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.
37. Ring Topology
Applications:
Ring topologies are found in some office buildings or
school campuses.
Today high speed LANs made this topology less
popular.
EX… IBM Token Ring,FDDI
38. • IBM created IEEE(Institute of Electrical and Electronics Engineers)
802.5 standard known as Token Ring
• it uses a special packet known as Token
• Multi-station Access Unit (MSAU)
39. A Token Ring network is a local area network (LAN) in
which all computers are connected in a ring or star
topology and a bit- or token-passing scheme is used in
order to prevent the collision of data between two
computers that want to send messages at the same
time. The Token Ring protocol is the second most
widely-used protocol on local area networks after
Ethernet. The IBM Token Ring protocol led to a
standard version, specified as IEEE 802.5. Both
protocols are used and are very similar. The IEEE 802.5
Token Ring technology provides for data transfer rates
of either 4 or 16 megabits per second.
40. FDDI (Fiber Distributed Data
Interface)
FDDI is a standard developed by the American
National Standards Institute (ANSI)
for transmitting data on optical fibers
Supports transmission rates of up to 200 Mbps
Uses a dual ring
First ring used to carry data at 100 Mbps
Second ring used for primary backup in
case first ring fails
If no backup is needed, second ring can
also carry data, increasing the data rate up to 200 Mbps
Supports up to 1000 nodes
Has a range of up to 200 km
The possessor of the token is allowed to put a new token onto the ring as soon
as it finished transmitting its frames
41. Tree Topology
Alternatively referred to as a star bus topology.
Tree topology is one of the most common network
setups that is similar to a bus topology and a star
topology.
A tree topology connects multiple star networks to
other star networks. Below is a visual example of a
simple computer setup on a network using the star
topology.
45. Considerations for choosing
topology
Money-Bus n/w may be the least expensive way to
install a n/w.
Length-of cable needed- the linear bus n/w uses
shorter lengths of cable.
Future growth-with star topology, expending a n/w is
easily done by adding another devices.
Cable type-most common used cable in commercial
organization is twisted pair. Which often
used with star topologies.
46. Full mesh topology is theoretically the best since
every device is connected to every other device.(thus
maximizing speed and security. however, it quite
expensive to install)
Next best would be tree topology, which is basically a
connection of star.
47. • 1973 by Bob Metacalfe (IEEE standard called 802.3 CSMA/CD)
48. Ethernet Overview
Most popular packet-switched LAN technology
Bandwidths: 10Mbps, 100Mbps, 1Gbps
Max bus length: 2500m
500m segments with 4 repeaters
Bus and Star topologies are used to connect hosts
Hosts attach to network via Ethernet transceiver or hub or switch
Detects line state and sends/receives signals
Hubs are used to facilitate shared connections
All hosts on an Ethernet are competing for access to the medium
Switches break this model
Problem: Distributed algorithm that provides fair access
49. Ethernet by definition is a broadcast protocol
Any signal can be received by all hosts
Switching enables individual hosts to communicate
Network layer packets are transmitted over an
Ethernet by encapsulating
Frame Format
Dest
addr
64 48 32
CRCPreamble Src
addr
Type Body
1648
50. • a section of a network where data packets can collide with one
another when being sent on a shared medium
• the larger the collision domain, the more likely it is that collision
will occur
51. •Carrier Sense Multiple Access/Collision Detect (CSMA/CD) is the
protocol for carrier transmission access in Ethernet networks. On
Ethernet, any device can try to send a frame at any time. Each device
senses whether the line is idle and therefore available to be used. If it
is, the device begins to transmit its first frame. If another device has
tried to send at the same time, a collision is said to occur and the
frames are discarded. Each device then waits a random amount of
time and retries until successful in getting its transmission sent.
52. Intranet is system in which multiple PCs are connected to each other.
PCs in intranet are not available to the world outside the intranet.
Usually each company or organization has their own Intranet
network and members/employees of that company can access the
computers in their intranet.
Each computer in Intranet is also identified by an IP Address which is
unique among the computers in that Intranet.
Intranet
(HCL)
Intranet
(Wipro)Internet
Extranet
