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Module 3
Lesson 2
The importance of topology

Objective
Recognize the impact of topology on network performance, media type, and cost.

So why does the topology, or shape, of the network matter? There are a number of reasons:

  • The network topology impacts performance.

  • The network topology is a factor in determining the media type used to cable the network.

  • The network topology impacts the cost of cabling the network.

  • Some access methods can work only with specific topologies.
     
Topology and performance

The path traveled by a data packet--the distance traveled and the layout of the path--as it moves from the sending computer to the receiving computer on the network greatly impacts the speed of communication.

The animation below illustrates how different topologies affect the speed of network communication.


Transcript


 
Knowing the layout of your network will help you to not only optimize your network's operation, but also troubleshoot performance issues.
 
Topology and media type

In addition to understanding performance issues, you also need to know how topology impacts network implementation through media type and cost. Different network layouts use different media types or materials. You will learn more about these different topologies later in the module. For example, thin coaxial cable is usually associated with the linear bus topology, while unshielded twisted pair cable is associated with the star bus topology. The type of cabling you wish to use for the network may determine the topology you will implement.

The table below shows the cable types associated with each common topology.
 

Topology Cable Type
Linear bus Thin coaxial Thick coaxial
Star bus Unshielded twisted pair (UTP)
Ring Shielded twisted pair (STP) Unshielded twisted pair (UTP) Fiber optic (FDDI rings)


 

 

TIP:Media types will be discussed in more detail later in the course.




 
Topology and cabling cost

Network layout, or topology, impacts cost in two ways:
  • Cable types that are associated with different topologies vary in cost.

  • Different topologies require different amounts of cable.

In general, thin coaxial and UTP are the least expensive cable types on a per-foot basis. STP and thick coaxial are in a middle price range, and fiber optic is the most expensive.

Coaxial cable is often referred to as "coax." The second cost factor is the amount of cable required for a particular layout or topology. The four most popular topologies used in laying out local area networks (LANs) are:

  • Linear bus

  • Star bus

  • Ring

  • Mesh (and hybrid or partial mesh)

The FlipBook below illustrates the differences in cable length requirements for each topology.
 


Transcript


 
Topology and access method

Topology may also determine a network's media access method. Different network topologies are associated with different media access methods. The media access method is the means by which access to the network is controlled and data collisions (computers "talking at the same time") are prevented.

Some access methods are associated with more than one topology. For example, token passing is an access method that is used with a ring topology (token ring) or a star or linear bus (ARCnet, token bus).
 


TIP:Media access methods will be discussed in more detail later in the course.




 
Next lesson

In the next lesson, you will learn to differentiate between logical and physical topology.
 
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