Shared Communication Channels
The development started in early 1960 and 1970s.
For the short distances, the LAN is used because it uses a shared medium which reduces the number of connections, has becoming a cheaper solution.
But due to this shared medium, the computers compete against each other to use the channel because they have to wait for their turns.
For long distances, the point-to-point approach is used.
Locality of Reference Principle
This principle helps to predict the communication patterns.
There are 2 patterns:
Spatial
In this pattern, computers which are located nearby are likely to communicate with each other.
Temporal
In this pattern, the computers are likely to communicate repeatedly to the same computers.
LAN is effective due to spatial locality of reference.
LAN Topologies
There are 3 popular LAN topologies:
Star
In this topology, the devices are attached to the central device called the hub.
Ring
In this topology, the computers are connected to each other in a closed loop.
One computer sends message to 2nd one, the 2nd one sends to 3rd one and so on.
Bus
In this topology, all the computers are connected to same back-bone cable.
The computers have to coordinate to wait for their turns.
Ethernet
It was invented in 1970s.
Intel and others defined it in a standard called DIX standard.
It is now managed by IEEE under standard 802.3 which defines the length and voltages etc.
It uses bus topology and is also called as a segment which is limited to 500 meters in length.
The minimum separation between connections is 3 meters.
Ethernet Speeds
- Originally, it was 3 Mbps.
- Standard now a days is 10 Mbps
- The fast ethernet operates at 100 Mbps ones
- But there are also which touches Giga bits per second.
Encoding Used in Ethernet
The encoding technique used in it is called manchester.
0is represented by voltage drop.1is represented by voltage increase.