Computer networks allow computers to communicate and share resources. They can be used for simultaneous access to shared data and devices, personal communications like email and messaging, video and audio conferencing, and easier backups. Networks connect computers through hardware, software, and communication media. They transmit information electronically between locations using technologies like cables, wireless transmission, and networking protocols. Common network topologies include bus, star, ring, and mesh configurations.

1. Computer Networks

4. The Telecommunications System

16. Star Topology Hub Server Comp1 Comp2 Comp3 Comp4 Most common topology All nodes connected through hub Some hubs- intelligent hubs can monitor traffic and prevent collisions Broken connection affects node only Broken hub affects all

17. Ring Topology Server comp1 comp2 comp3 comp4 Nodes are connected in circular chain Each node examines data as it travels through ring A small packet called token is circulated in the ring If token is not addressed to the node examining it, it passes to the next node No danger of collisions as only one packet of data travels at a time in the ring

18. Mesh Topology Comp1 comp2 comp3 comp4 Least used topology Most expensive to implement A cable runs from every computer to other computers Advantage- data can never fail to be delivered as there are alternate paths

19. Hierarchical Topology Main Frame Mini1 Mini2 Mini3 comp1 comp2 compn

20. Hybrid Topology Server comp1 Printer Printer Main frame Mini Mini Star Ring Hierarchical