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2  LAN (Local Area Network) ◦ A group of computers and associated devices (printers, etc.) ◦ connected through a wired or wireless medium ◦ by networking devices (hubs, switches, routers) ◦ use protocols for communication

 Topology ◦ Layout of how devices connect on network  Wired Networks  Wireless Networks RD-CSY10173

4 Two types of connections:  Dedicated or Point-to-point ◦ Direct connection between two computers  Shared ◦ Multiple computers share the media

 Topology: Physical layout of network.  Some of the popular network topologies are: ◦ Star Topology  Distributed Star ◦ Bus Topology ◦ Ring Topology ◦ Tree Topology ◦ Mesh  Full Mesh  Partial Mesh RD-CSY10175

6 Advantages  Each network connection is independent  It can be customised to suit the type of data ◦ for example: data speed and technology  It is easy to enforce security and privacy. Disadvantages Not scalable for large networks Computer A Point to Point network Black links show four connections from computer A to all computers in the network

RD-CSY10177 Star Topology  Individual computers are connected to a central point – a hardware device, called a hub/switch.  Max distance between a computer and hub/switch is restricted based on cable used. ◦ With UTP cable, distance limited to 100m.  Popular topology for LAN (local area networks)  Adv: Failure of any computer does not affect other communications in the network  Disadv: Failure of hub/switch can bring the network down, also called SPF( Single Point of Failure) Star Topology Extended Star Topology

 Also called a "hierarchical" or "star of stars" topology  Nodes are connected in groups of star-configured workstations that branch out from a single "root,"  The root node usually controls the network and sometimes network traffic flow.  This topology is easy to extend: when new users need to be added 8RD-CSY1017

 Full mesh topology ◦ each node is physically connected to every other node  Adv : Highly fault tolerant: when one node fails, traffic can easily be diverted to other nodes  Disadv : Not scalable for large networks  Partial mesh topologies are popular for backbone networks, where redundancy is desirable Partial Mesh Full Mesh 9RD-CSY1017

10  Computers are connected to each other to form a closed loop.  Common Examples ◦ FDDI Network  Usually Fibre optic cable based backbone networks ◦ Token Ring Network  Example: IBM token ring network  Proprietary network  Adding and removing computers disrupts the network.  What should be done to provide redundancy in a ring topology ? computer cable

 Most wireless implementations are based on ◦ Star, tree or line topology  Two modes: ◦ Ad hoc  No need of central access point  Problem: Not scalable ◦ Infrastructure (more common)  Central Access Point (AP) is needed  Scalable  Many wireless implementations are based on more than one topology RD-CSY101711

RD-CSY  Star Hotspots, Offices and WISP's Point to Multipoint The most common infrastructure in wireless networking point-2-point Connecting two wireless clients directly Building to building (when one has Internet connection and the other one does not) point-2-point - Repeating Necessary when direct line of sight (LOS) is obstructed

 Mesh topologies are an interesting option mainly in ◦ dynamic environments (urban areas) where central infrastructure is hard to implement ◦ when redundancy is desired  Typical cases are: municipal networks, campus networks etc. RD-CSY101713

 At the center of any cellular technology is the cellular transceiver, an omni- directional antenna whose range projects a circular "footprint." This footprint is the "cell" that gives cellular technology its name  As the cellular user moves from one cell to another, the user's signal is transferred from one antenna to another 14RD-CSY1017

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 Use packet tracer to set up a network using following Topologies ◦ Star ◦ Distributed Star ◦ Point-to-point ◦ Tree  Refer to your task sheet for details 17RD-CSY1017