1. Network Essentials -III Prof. Sujata Rao Lesson 12

2. Physical node-to-node bit-by-bit Network host-to-host Link node-to-node frame-by-frame 101101001000100101010

4. HUB

5. Hubs A hub is a physical layer device. HUB is a network device used to connect multiple network connections. It is also known as concentrator. When it receives a bit from one of its interface, it simply repeats it on all its outgoing interfaces. It helps in simplification of cabling. It increases reliability in case of transmission problem Simplifies trouble shooting

6. Switch

7. Switches A switch is a link-layer devices. It operates on Ethernet frames. When a frame is received, it checks the destination address and either forwards it to correct interface or drops (filters) it.

8. Bridges, Gateways & Routers These are devices which help one network to communicate to other. Used to link network positioned in different location Bridges are used to connect 2 network with different topologies Gateways used to connect 2 network with different protocols. Routers are used to connect 2 network irrespective of topologies or protocol

9. Modems Used to communicate over the telephone line Does mudulation & demodulation Used for temporary connection for remote users Node Used to denote any device on a network It can also refer to the intersection ‘T’

10. Bandwidth, Load Amount of data that can be transmitted over a given segment, of the communication media, within a specific time is known as bandwidth of a network. Usually measured in kbps or mbps Load is the demand on a network. Demand of 100 users on network > 10 users on the network.

11. Overhad & Lag The amount of bandwidth required to complete a given network operation sucessfully is the network overhead. Lag This term defines the sluggishness of operation of an overworked network. When the overhead or the load on the network reaches the current bandwidth the network experiences a LAG.

12. Computing Models Centralised or Mainframe Model Client Server Computing Model Distributive Multiple Servers with data distributed across servers Data-processing is distributed across multiple servers on the network. Collaborative Two or more servers that work together. The capabilities of both servers are combined to complete a task instead of splitting a task.

13. Advantage of Client Server Model Low Network traffic Less RAM required by client High level of Data security Easy Database Management

14. THE OSI Reference Model OSI - Open system Interconnection Developed by ISO in 1977 to develop data communication standards. OSI is a set of rules for various functions with in each layer of communication by a variety of protocols. Has 7 layers

15. NUS.SOC.CS2105 Ooi Wei Tsang Application Transport Network Data Link Physical Presentation Session Files Transfer, user acess Formats Data Maintains communication between the devices Provides reliable data transmissioin Switches and routes information units Provides data exchange between devices on the same medium Transmit bit stream to physical medium HOSTHOST NETWORKNETWORK