Two Most Common LANs

The two most commonly used LANs are Ethernet and Token Ring local area networks.

Ethernet

The Ethernet is a local area network developed by Xerox, Digital (DEC) and Intel and is the most popular LAN in the world, accounting for almost 50 percent of all LANs.

• Topology: Ethernet uses a bus topology. A major circuit running the length on the network connects all computers. When the Ethernet uses a central hub, the topology of it looks like a star (physically) from the outside, but it is really a bus (logically).

• Types of Ethernet:
  • 10Base5: The original Ethernet specification was a 10Mbps data rate using Baseband signaling on thick coaxial cable, called "Thick Ethernet (5)."

  • 10Base2: Today, thin coaxial cable is rapidly replacing the original thick coax because it is considerably cheaper and easier to work with. The 10Base2 standard is often called "Thin Ethernet (2)."

  • 10BaseT: This is the most commonly used type of Ethernet. The name means 10 million bits per second, Baseband, and the "T" means it uses twisted pair wiring. The extremely low cost of 10BaseT made Ethernet very inexpensive and the most popular type of LAN.

  • 10Broad36: It means 10 Mbps, broadband, with a maximum distance of 3600 meters. This standard is most commonly used in backbone networks.

Token Ring

This is a local area network developed by IBM that uses a special twisted wire and the token passing access method. Token Ring LANs are the second most popular type of LAN, with almost 40 percent of all LANs worldwide.

• Topology: A Token Ring network uses a ring topology. All messages pass to each computer in turn. Computers receive all messages, but only process those addressed to themselves. They deliver the rest of messages to the next computer in the network. When central hubs are used, it also looks like a star configuration (physically), but it really is a ring network (logically).

• Media Access Control: Token Ring network uses a token passing technology. A computer with a message to deliver waits until it receives free token. The computer then changes the free token into a busy token, attaches its message to it, and retransmits it on the circuit to the next computer.

• Types of Token Ring: There are two common types of Token Ring networks. The Token Ring developed first was Token Ring-4, transmitting data at 4Mbps over twisted wire. The newer Token Ring network is Token Ring- 16, delivering information at 16Mbps over high quality twisted wire.