Network+ Exam Objectives 2.3

2.3 Identify common physical network topologies.

Topology is simply how a network is organized. Physical topology involves how a network is physically mapped. Topology also involves logical topology, which considers how data flows and is processed on a network. Generally physical and logical topologies are mapped in the same way, but in some network topology types the two can be different.

• Star – Star topology is a network when all nodes in a network are connected to a centralized point such as a switch or hub. Star topology is often used with 10Base10 and 100BaseTX. Star topology is inexpensive, easy to maintain, very reliable, and is one of the most commonly used physical network topology today. Star topology is prone to collisions and other security problems.

• Mesh – Mesh network topology is very different from most topologies in the fact that all parts of the network can connect to each other through multiple hops. This means that broken paths can be easily rerouted as alternative paths can be used. A fully connected mesh network occurs when every other network node is connected. Mesh topology is generally used in WANS and most importantly the Internet. Mesh topology provides high fault tolerance so if a node were to fail, the network can still run. However mesh topology is extremely complicated as well as costly to set up and maintain.

• Bus – Bus topology is quite simple: the network is set up in a linear, straight sequence of nodes that is terminated in both ends. Bus topology is used with both Thinnet and Thicknet. Though simple, bus topology is rarely used today because it is unreliable. If a node within the network fails, the entire network will not work. Bus topology is pretty much obsolete in today’s world.

• Ring – In ring topology, packets travel to the next mode within the ring formation. This means that only one node at a time has the token. Ring topology in the logical fashion is often used in ordinance with physical star topology. Ring topology is used in Token Rings as well as FDDI. Ring topology is great in the fact that collisions rarely occur however the topology is expensive and hard to troubleshoot. The topology is prone to failure and if one of the nodes fails, the entire network fails.

• Point to point – Point to point topology is when a switch is used in order to provide for many point-to-point circuits through microsegmentation. This allows for each node to have a set circuit as well as access to full duplex connections.

• Point to multipoint – In point to multipoint topology, a hub is used which then creates a network circuit that divides the bandwidth from the hub for each node that is connected. Point to multipoint topology is used in ATM, X.25 networks, wireless internet, and Frame Relay links.

• Hybrid – Hybrid networks are simply those networks that use a combination of two or more topologies. With this combination the outcome does not meet any of the commonly used topology types. An example is two connected star networks or a star ring network.

 

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