| Network Topologies |
There are 4 basic topologies with variations
Bus Topology
- Bus consists of a single linear cable called a trunk.
- Data is sent to all computers on the trunk. Each computer examines EVERY packet on the wire to determine who the packet is for and accepts only messages addressed to them.
- Bus is a passive topology.
- Performance degrades as more computers are added to the bus.
- Signal bounce is eliminated by a terminator at each end of the bus.
- Barrel connectors can be used to lengthen cable.
- Repeaters can be used to regenerate signals.
- Usually uses Thinnet or Thicknet
- both of these require 50 ohm terminator
- good for a temporary, small (fewer than 10 people) network
- But its difficult to isolate malfunctions and if the backbone goes down, the entire network goes down.
Star Topology
- Computers are connected by cable segments to a centralized hub.
- Signal travels through the hub to all other computers.
- Requires more cable.
- If hub goes down, entire network goes down.
- If a computer goes down, the network functions normally.
- most scalable and reconfigurable of all topologies
Ring Topology
- Computers are connected on a single circle of cable.
- usually seen in a Token Ring or FDDI (fiber optic) network
- Each computer acts as a repeater and keeps the signal strong => no need for repeaters on a ring topology
- No termination required => because its a ring
- Token passing is used in Token Ring networks. The token is passed from one computer to the next, only the computer with the token can transmit. The receiving computer strips the data from the token and sends the token back to the sending computer with an acknowledgment. After verification, the token is regenerated.
- Relatively easy to install, requiring ;minimal hardware
Mesh
- The mesh topology connects each computer on the network to the others
- Meshes use a significantly larger amount of network cabling than do the other network topologies, which makes it more expensive.
- The mesh topology is highly fault tolerant.
- Every computer has multiple possible connection paths to the other computers on the network, so a single cable break will not stop network communications between any two computers.
Star Bus Topology
- Several star topologies linked with a linear bus.
- No single computer can take the whole network down. If a single hub fails, only the computers and hubs connected to that hub are affected.
Star Ring Topology
- Also known as star wired ring because the hub itself is wired as a ring. This means it’s a physical star, but a logical ring.
- This topology is popular for Token Ring networks because it is easier to implement than a physical ring, but it still provides the token passing capabilities of a physical ring inside the hub.
- Just like in the ring topology, computers are given equal access to the network media through
- the passing of the token.
- A single computer failure cannot stop the entire network, but if the hub fails, the ring that the hub controls also fails.
Hybrid Mesh
- most important aspect is that a mesh is fault tolerant
- a true mesh is expensive because of all the wire needed
another option is to mesh only the servers that contain information that everyone has to get to. This way the servers (not all the workstations) have fault tolerance at the cabling level.
