1. Networking
IT-402

2. Data Communication & Networks
Agenda
Networks
Concept & Benefits
Types of Computer Network
Network Topologies
Network Devices
OSI Model

3. Network Concept: A network consists of two or more computers
that are linked in order to share resources (such as printers and CDs), exchange files, or allow electronic communications.
The computers on a network may be linked
through cables, telephone lines, radio waves,
satellites, or infrared light beams.

4. Benefits of Network Helps to enhance connectivity
Networking helps in sharing of hardware 
Eases out management of data.
Internet
Data Sharing
Easier Communication
Money Saving

5. Types of Computer Network
Depending upon the geographical area covered by a network, it is classified as: – Local Area Network (LAN) – Metropolitan Area Network (MAN) – Wide Area Network (WAN) – Personal Area Network (PAN)

6. LAN (Local Area Network)
A LAN is a network that is used for communicating among computer devices, usually within an office building or home.
LAN’s enable the sharing of resources such as files or hardware devices that may be needed by multiple users.
Is limited in size, typically spanning a few hundred meters, and no more than a mile.
Is fast, with speeds from 10 Mbps to 10 Gbps
Requires little wiring, typically a single cable connecting to each device
Has lower cost compared to MAN’s or WAN’s

7. LAN’s can be either wired or wireless.
Nodes in a LAN are linked together with a certain topology. These topologies include:
– Bus – Ring – Star
LANs are capable of very high transmission rates (100s Mb/s to G b/s).
Advantages
Disadvantages
Speed
Cost
Security
Resource Sharing
Expensive To Install
Requires Administrative Time
File Server May Fail
Cables May Break

8. Peer-to-Peer Network Client Server Network LAN
a peer-to-peer (P2P) network is created when two or more PCs are connected and share resources without going through a separate server computer.
Client Server Network
client/server network. A computer network in which one centralized, powerful computer (called the server) is a hub to which many less powerful personal computers or workstations (called clients) are connected.

9. Metropolitan Area Network (MAN)
A Metropolitan Area Network (MAN) is a large computer network that usually spans a city or a large campus.
A MAN is optimized for a larger geographical area than a LAN, ranging from several blocks of buildings to entire cities.
A MAN might be owned and operated by a single organization, but it usually will be used by many individuals and organizations.
A MAN often acts as a high speed network to allow sharing of regional resources.
A MAN typically covers an area of between 5 and 50 km diameter.
Examples of MAN: Telephone company network that provides a high speed DSL to customers and cable TV network.

11. Wide Area Network (WAN)
WAN covers a large geographic area such as country, continent or even whole of the world.
A WAN is two or more LANs connected together. The LANs can be many miles apart.
To cover great distances, WANs may transmit data over leased high-speed phone lines or wireless links such as satellites.
Multiple LANs can be connected together using devices such as bridges, routers, or gateways, which enable them to share data.
The world's most popular WAN is the Internet.

12. Wide Area Network

13. Personal Area Network (PAN)
personal area network (PAN) is a computer network used for communication among computer devices, including telephones and personal digital assistants, in proximity to an individual's body.
A PAN is a network that is used for communicating among computers and computer devices (including telephones) in close proximity of around a few meters within a room.
It can be used for communicating between the devices themselves, or for connecting to a larger network such as the internet.
PAN’s can be wired or wireless.
The reach of a PAN is typically a few meters.

14. Network Topologies

15. Network Topologies
The Physical layout or the way in which network connections are made is called Topology.
It refers especially to the locations of computers and how the cable runs between them.
It is important to select the right topology for proper use of computer network
There are three basic topologies
Bus Topology
Star Topology
Ring Topology

16. Bus Topology
All networked nodes are interconnected, peer to peer, using a single, open-ended cable
Both ends of the bus must be terminated with a terminating resistor to prevent signal bounce.

17. Advantages of Bus Topology
Easy to implement and extend.
Well suited for temporary networks that must be set up in a hurry.
Typically the least cheapest topology to implement.
Failure of one station does not affect others.
Disadvantages of Bus Topology
Difficult to administer/troubleshoot
Limited cable length and number of stations
A cable break can disable the entire network; no redundancy
Maintenance costs may be higher in the long run
Performance degrades as additional computers are added

18. Ring topology
Each computer is connected to the next computer with the last one connected to the first.
Each networked workstation had two connections: one to each of its nearest neighbors
Data was transmitted unidirectional around the ring
Sending and receiving of data takes place by the help of TOKEN

19. Advantages of Ring topology
This type of network topology is very organized
Performance is better than that of Bus topology
No need for network server to control the connectivity between workstations
Additional components do not affect the performance of network
Each computer has equal access to resources
Disadvantages of Ring topology
Each packet of data must pass through all the computers between source and destination, slower than star topology
If one workstation or port goes down, the entire network gets affected
Network is highly dependent on the wire which connects different components

20. Star topology
Have connections to networked devices that “radiate” out form a common point
Each networked device in star topology can access the media independently
Have become the dominant topology type in contemporary LANs
Stars have made buses and rings obsolete in LAN topologies

21. Advantages of star topology
Compared to Bus topology it gives far much better performance
Easy to connect new nodes or devices
Centralized management. It helps in monitoring the network
Failure of one node or link doesn’t affect the rest of network
Disadvantages of star topology
If central device fails whole network goes down
The use of hub, a router or a switch as central device increases the overall cost of the network
Performance and as well number of nodes which can be added in such topology is depended on capacity of central device

22. Network Devices

23. What is a Network Device?
Components used to connect computers as well as other electrical devices together in order to share resources such as printers and fax machines.
The different devices or components used in networking include:
Hubs
Switches
Routers
Network bridges
Gateways
Firewalls
Wireless AP (Access Points)

24. What is a Hub?
A small rectangular box that joins computers together through ports on the back of the hub.
How does a Hub work?
A hub receives data packets and passes on all the Information it receives to all the other computers connected to the hub.
Information is also sent to the computer that sent the information.
Hubs can be used for a smaller network such as a home network or a small office network.
Hubs may not be the best option for sophisticated or complex networks.
Example: if computer 1 wants to communicate with computer 3, the data will be sent to all the computers on the network since hubs do not know the destination of the information it receives. J

25. Diagram of a hub network
Main PC
Hub
Ethernet
PC 1
PC 2

26. What is a Switch? How does a Switch work?
Switches look similar to hubs in that they are rectangular in shape.
Manageable switches are usually a little bigger than unmanageable switches. A switch also has ports on the back.
Switches are a better option than hubs for larger networks or home networks with 4 or more connected computers.
How does a Switch work?
Switches work about the same way as hubs. Unlike hubs, switches can identify the destination of a packet.
Switches send information only to the computer that is suppose to receive the information.
Switches can also send and retrieve information at the same time which makes sending information faster to retrieve than hubs.

27. Diagram of a Switch Network

28. What is a Router?
A specialized computer programmed to interface between different networks.
Routers make sure data sent over the Internet goes where it needs to go and not where it is not needed.
Routers are the only type of equipment that looks at every single packet passing by on the network.
How does it works?
A router receives data from the user.
Looks for the remote address of the other computer making routing decisions along the way
Forwards the user data out to a different interface that is closer to the remote computer

29. Diagram of a Router

30. What is a Bridge?
A hardware device used to create a connection between two separate computer networks or to divide one network into two.
Filters data traffic at a network boundary and reduces the amount of traffic on a LAN dividing it into two segments.
How does it works?
Each bridge consist of a MAC address and operates at layer 2 of the OSI model
When a packet is received on the bridge ports the forwarding table including the MAC address is automatically updated to map the source MAC address to the network port from which the packet originated
The gateway then process the received packet according to the packet’s type.

31. Diagram of a Bridge
A bridge examines each message on a LAN and passes the ones known to be within the same LAN.
Computer addresses have no relationship to location in a bridging network.
A bridge is sometimes referred to as a brouter.

32. What is a Gateway?
A communication device that provides a remote network with connectivity to the host network.
On the Internet a node or stopping point can be a gateway.
The computers controlling traffic within a network are gateway nodes.
A gateway is also associated with a router.
How a Gateway Works?
The gateway node acts like a proxy server and firewall
The gateway uses forwarding tables to determine where packet are to be sent

33. Gateway Diagram

34. What is a Firewall?
Hardware or software device that protects a computer network from unauthorized access.
Most home network routers have built in firewall.
The term “firewall” originated from firefighting, where a firewall is a barrier established to prevent the spread of a fire.
A firewall works with the proxy server making request on behalf of workstation users.
There are a number of features firewalls can include from logging and reporting to setting alarms of an attack.

35. How a Firewall works
Firewalls filters the information coming through the Internet connection into a user private network.
To control traffic in and out of the network firewalls one or more of the three methods are used including:
Packet filtering
Proxy service
Stateful inspection

36. Diagram of Firewall

37. What is a Wireless Access Point?
A small hardware device featuring built-in network adapter, antenna, and radio signals.
Configured nodes on a WLAN.
The access point usually connects to the router
A hotspot is a application wireless users can connect to the Internet.
Aps are used throughout a home network, usually through only one AP.

38. How a Wireless Access Point works?
Operates using radio frequency technology
Broadcast wireless signals computers can detect and use
A wireless network adapter is implemented while using a wireless access point, most computers today already have network adapters built into the computer.

39. Diagram of Wireless Access Point
RxNT – The eprescribing System. [online image]. Available

40. OSI MODEL

41. OSI Model Background Introduced in 1978 and revised in 1984
Formulates the communication process into structured layers
There are seven layers in the model, hence the name the 7-Layer model
The model acts as a frame of reference in the design of communications and networking products

42. THE SEVEN OSI REFERENCE MODEL LAYERS

43. LAYER 7: APPLICATION
The application layer is the OSI layer that is closest to the user.
It provides network services to the user’s applications.
It differs from the other layers in that it does not provide services to any other OSI layer, but rather, only to applications outside the OSI model.
Examples of such applications are spreadsheet programs, word processing programs, and bank terminal programs.
The application layer establishes the availability of intended communication partners, synchronizes and establishes agreement on procedures for error recovery and control of data integrity.

44. LAYER 6: PRESENTATION
The presentation layer ensures that the information that the application layer of one system sends out is readable by the application layer of another system.
If necessary, the presentation layer translates between multiple data formats by using a common format.
Provides encryption and compression of data.

45. LAYER 5: SESSION
The session layer defines how to start, control and end conversations (called sessions) between applications.
This includes the control and management of multiple bi-directional messages using dialogue control.
It also synchronizes dialogue between two hosts' presentation layers and manages their data exchange.
The session layer offers provisions for efficient data transfer.

46. LAYER 4: TRANSPORT
The transport layer regulates information flow to ensure end-to-end connectivity between host applications reliably and accurately.
The transport layer segments data from the sending host's system and reassembles the data into a data stream on the receiving host's system.
The boundary between the transport layer and the session layer can be thought of as the boundary between application protocols and data-flow protocols. Whereas the application, presentation, and session layers are concerned with application issues, the lower four layers are concerned with data transport issues.
Layer 4 protocols include TCP (Transmission Control Protocol) and UDP (User Datagram Protocol).

47. LAYER 3: NETWORK Defines end-to-end delivery of packets.
Defines logical addressing so that any endpoint can be identified.
Defines how routing works and how routes are learned so that the packets can be delivered.
The network layer also defines how to fragment a packet into smaller packets to accommodate different media.
Routers operate at Layer 3.

48. LAYER 2: DATA LINK
The data link layer provides access to the networking media and physical transmission across the media and this enables the data to locate its intended destination on a network.
The data link layer provides reliable transit of data across a physical link by using the Media Access Control (MAC) addresses.
The data link layer uses the MAC address to define a hardware or data link address in order for multiple stations to share the same medium and still uniquely identify each other.
Concerned with network topology, network access, error notification, ordered delivery of frames, and flow control.

49. LAYER 1: PHYSICAL
The physical layer deals with the physical characteristics of the transmission medium.
It defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between end systems.
Such characteristics as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, physical connectors, and other similar attributes are defined by physical layer specifications.

50. Thank you…!!!