# Network Topologies. The concept of a topology. The basic function of computers on the LAN is to provide the user with an almost limitless set of applications.

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Network Topologies

The concept of a topology.

The basic function of computers on the LAN is to provide the user with an almost limitless set of applications.

Topologies  Physical Topologies define the actual layout of the wire (media).  For example, this classroom’s wiring is laid out in an extended star  Logical Topologies define how the media is accessed by the hosts.  For example, in this classroom hosts access the media on a first come, first served basis Physical Logical

Physical Topologies Bus Ring Star Extended Star Hierarchical Mesh

Bus Topology  Single backbone  All hosts directly connected to backbone  Each end of the bus must be properly terminated

Ring Topology  No backbone  A host is directly connected to each of its neighbors  Used for token passing logical topologies

Star Topology  All devices connected to a central point  Center of star is usually a hub or a switch  Used for Ethernet technologies

Extended Star Topology  Connects individual star topologies together.  At the center of the star is a hub or a switch.  Extends the length and size of the network.  This is the topology we are using in our lab!

Hierarchical Topology  Like the extended star except a computer controls traffic—not a hub or a switch. Server

Mesh Topology  Each host has its own connection to every other host  Used in situations where communication must not be interrupted.

Logical Topologies  Broadcast Topology  Each host on the LAN sends its data (or broadcasts its data) to every other host.  Access to media is based of “first-come, first- serve.” (Ethernet works this way)  Token Passing Topology  Access to media is controlled by an electronic token.  Possession of the token gives the host the right to pass data to its destination.

AdvantagesDisadvantages Bus Use of cable is economical. Media is inexpensive and easy to work with. System is simple and reliable. Bus is easy to extend. Network can slow down in heavy traffic. Problems are difficult to isolate. Cable break can affect many users. Ring System provides equal access for all computers. Performance is even despite many users. Failure of one computer can impact the rest of the network. Problems are hard to isolate. Network reconfiguration disrupts operation. Star Modifying system and adding new computers is easy. Centralized monitoring and management are possible. Failure of one computer does not affect the rest of the network. If the centralized point fails, the network fails. Mesh System provides increased redundancy and reliability as well as ease of troubleshooting. System is expensive to install because it uses a lot of cabling. Topologies

What kind of topology is this?

The Cloud

What kind of topology is this? The Cloud

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