Lesson 1: Networking Basic

Networking History |  How a LAN Is Built | LAN Topologies | LAN/WAN Devices

LAN Topologies

You may hear the word topology used with respect to networks. “Topology” refers to the physical arrangement of network components and media within an enterprise networking structure. There are four primary kinds of LAN topologies: bus, tree, star, and ring.

Bus and Tree topology

Bus topology is

 - A linear LAN architecture in which transmissions from network components propagate the length   of the medium and are received by all other components.
 - The bus portion is the common physical signal path composed of wires or other media across    which signals can be sent from one part of a network to another. Sometimes called a highway.
 - Ethernet/IEEE 802.3 networks commonly implement a bus topology

Tree topology is

 - Similar to bus topology, except that tree networks can contain branches with multiple nodes. As    in bus topology, transmissions from one component propagate the length of the medium and are    received by all other components.

The disadvantage of bus topology is that if the connection to any one user is broken, the entire network goes down, disrupting communication between all users. Because of this problem, bus topology is rarely used today.
The advantage of bus topology is that it requires less cabling (therefore, lower cost) than star topology.

Star topology

Star topology is a LAN topology in which endpoints on a network are connected to a common central switch or hub by point-to-point links. Logical bus and ring topologies re often implemented physically in a star topology.

 - The benefit of star topology is that even if the connection to any one user is broken, the network    stays functioning, and communication between the remaining users is not disrupted.
 - The disadvantage of star topology is that it requires more cabling (therefore, higher cost) than    bus topology.

Star topology may be thought of as a bus in a box.

Ring topology

Ring topology consists of a series of repeaters connected to one another by unidirectional transmission links to form a single closed loop.

 - Each station on the network connects to the network at a repeater.
 - While logically a ring, ring topologies are most often organized in a closed-loop star. A ring    topology that is organized as a star implements a unidirectional closed-loop star, instead of    point-to-point links.
 - One example of a ring topology is Token Ring.

Redundancy is used to avoid collapse of the entire ring in the event that a connection between two components fails.

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