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Table of Contents
Learning Goals
Learning Goals
What do all of the Topologies do.
How do all the Topologies function.
Difference between Logical and Physical Topologies.
Network Topologies
Network Topologies
Physical Topology
Physical Topology
What is a physical topology?
A physical topology describes the way a network is wired.
Bus: One cable (Trunk Cable) with nodes at the end of the trunk or tapped into the trunk using offshoot cables (Drop Cables)
Signals that travel from one node are broadcasted to all other nodes.
Nodes: Ports of devices (Ethernet Port)
Terminators are placed at both ends of a trunk cable
These are to prevent signals from bouncing back and forth on the bus.
If any part of the Trunk Cable is broken, the entire network goes down.
Rating: BAD network topology
Pros:
Easy for small groups that need to communicate.
No centralized device needed.
Cons:
Hard to isolate network problems.
No redundancy.
No ability to selectively send to one device.
Outdated; A hub does its job better and is easier to use.
Ring: Connects every device to the next device until it loops back around to the first device.
Signals travel in one direction around the ring
Each device acts as a repeater, extending the signal to the next device
Rating: MID network topology
Pros:
Only sends file along the line until it reaches its destination
If one cable goes down, the whole network doesn't go down.
Multiple cables provides some redundancy
If a cable goes down, PC's down-stream of the cable can still communicate
Cons:
Isolating problems requires going around the entire ring (time consuming)
If a wire breaks, PC's behind the break can not communicate with the pc's in front of the break
Has to send file to every pc in the way of the destination PC
Star: Uses a hub / switch to connect all network connections to a single physical location (a hub / switch)
All network connections connect to one location
Rating: AMAZING network topology
Pros:
Since all network communications are in a single place, it is easy to trouble shoot
If a wire breaks, only that PC is affected
If the entire network goes down, it is easy to tell the problem (hub / switch is broken)
Adding and Removing devices from the network is easy
(Switch only) Allows for data to be sent to specific PC's rather than entire network
Hubs do not do this, they are glorified trunk cables.
Cons:
If there are problems with your central device, your entire network goes down
Mesh: when there are more than one paths between any two nodes on a network.
Created using point-to-point connections.
Basically, Imagine getting ethernet cables and connecting every devices to every other / multiple other devices.
Commonly used as a redundancy for wireless routers.
Two types:
Partial mesh: There are some redundant paths in the network
Full mesh: Every node is connected to every other node
Rating: PRETTY GOOD network topology
Pros:
Provides a LOT of redundancy, especially full meshes.
Multiple cables have to go down to have communications go down between devices
Useful for important infrastructure that can't afford to go down.
Full meshes are commonly used to connect routers together.
Cons:
Full meshes become increasingly impractical as you add devices onto the network.
Each host added equals 1 cable times the number of current nodes, which would rack up costs quickly
Extremely Costly to set up
Hybrid Topologies: Combines two or more topologies together to help with scalability.
E.X. having multiple star topologies and connecting the network devices together with a bus, ring, or mesh topology
Logical Topology
Logical Topology
Logical Topology: describes the way messages are sent digitally. Some physical topologies can digitally send data differently than normal
Bus: Messages are sent out to all devices on a network
Usable by Bus and Star physical topologies
A hub is an example of a star using a logical bus topology.
Ring: Messages are sent from one device to the next device in a specific order and direction until they reach the destination device
Usable by Ring and Star topologies
Star: Messages are sent directly to (and only to) the destination device
Mesh: Messages are sent from one device to the next until they reach the destination device
Unlike ring, this is not in any given order and routing protocols determine the fastest way from point A to point B in this case
Star and Mesh topologies can only use Star and Mesh logical topologies respectively
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