network topologies
Talking about the Local area network, we should be familiar with the concept of the LAN topology that we use. There are many types of LAN topologies for different types of networks. We should also be familiar between physical topology and logical topology. Physical topology describes the layout of a network media such as copper cable, fiber optic cable, and most popular today is the wireless. While the logical topology is concerned about logical path through the network that data can take from one place to another.
The following are basic types of LAN topology
- Bus
- Star
- Ring
- Mesh
- Hybrids
But in this chapter we consider only in three types of it, Bus, Star, and ring
Bus topology
w All network nodes connect to the bus, which is a single communications channel, such as twisted pair, coaxial cable, or fiber optic cable.
Advantages:
LAN Bus topology is very simple and inexpensive to implement, there is only one main trunk.
Disadvantages:
- LAN Bus topology requires proper termination on both ends of the bus. Improper termination will cause the network to be malfunction
- One single trunk cable becomes a single point of failure, one break, causes all the network impact.
- Difficult in troubleshooting since you only have one single cable to share for all the computers on the network.
Star topology:
All network nodes connect to a single computer, typically the file server.
Advantages:
Any single failure of the port will not impact the whole network. See also
Installation of the cable in each port will not disrupt LAN services
No termination needed like in bus topology.
Ring topology:
Network nodes are connected to adjacent nodes to form a closed loop.
In a ring topology, access to the network is controlled through a token that is passed from node to node as the arbitration mechanism. Each node takes its turn at claiming the token as the token passes from neighbor to neighbor, and when a node possesses the token, it takes its turn to transmit onto the ring
Advantages:
- No collision detection mechanism is required, so Token ring provides greater overall bandwidth use.
- Troubleshooting is easy by the fact that each node only knows its upstream and downstream neighbors.
Disadvantages:
- The firmware required to manage the ring is somewhat complicated and must be on every network card that participates in the ring
- Expensive to implement and mostly the LANs today use Ethernet technology which dominate the market today.
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