Network Topology Description

    Network Topology

Network Topology is the arrangement of various devices like links or nodes of a computer Network.A network Topology explains how data flows within the network. LAN (Local Area Network) is one of the best examples of a network topology. Conversely saying that mapping the data flow between the components determines the logical topology of the network.

The types of Topology are as Follows :

1. Bus Topology 
2. Star Topology
3. Ring Topology
4. Mesh Topology
5. Hybrid Topology

 

Properties of Network Topology

The properties of Network Topology are as follows:
Cable: The type of networking cable used to create a topology.
Speed: Speed of a networking cable that is sending data.
Central Device: The central node which connects all the nodes in the Topology. 
Access Methods: An Access method is a set of rules that how the computer sends and receives data from the cable. In a network all the traffic appears to move simultaneously without any interruption but the reality is that the computer is taking turns accessing for a period of time.
Multiple computers must share access to the cable that has connected them but if two computers were to put data onto the cable at the same time, the data packets from one computer would collide with the packets from the other computer, and both sets of data packets would be destroyed. 

The types of Access Methods are as follows:

• Carrier-sense Multiple Access Methods (with collision detection ).
• Token-passing methods that allow only a single opportunity to send data.
• Demand-Priority Methods. 

Carrier-Sense Multiple Access with Collision Detection (CSMA/CD) 

In this method Computers listen to or "sense" the cable (Carrier-sense). Commonly, many computers on the network attempt to transmit data (multiple access), each one first listens to detect any possible collisions. If a computer detects a possible collision, it waits for a random period of time before retransmitting (collision detection).

  

Token-Passing Methods

In the access method known as token passing, a special type of packet, called a token, circulates around a cable ring from computer to computer. When any computer on the ring needs to send data across the network, it must wait for a free token. When a free token is detected, the computer will take control of it if the computer has data to send. The computer can now transmit data. Data is transmitted in frames, and additional information such as addressing, is attached to the frame in the form of headers and trailers .

Demand Priority Method 

Demand priority is a relatively new access method designed for the 100-Mbps Ethernet standard known as 100VG-AnyLAN. This access method is based on the fact that repeaters and end nodes are the two components that make up all 100VG-AnyLAN networks. The repeaters manage network access by doing round-robin searches for requests to send from all nodes on the network. The repeater, or hub, is responsible for noting all addresses, links, and end nodes and verifying that they are all functioning. According to the 100VG-AnyLAN definition, an end node can be a computer, bridge, router, or switch.

Description of Topology 

Star Topology 

A Star Topology is a network topology used in LAN where each device is connected to one central node which can be a hub or a switch.

Advantages:

• If one cable of a node falls,that node will only be brought down.

Disadvantages:

• Expensive because it requires more cabling.

 Properties

• Cable=Coaxial/UTP
• Speed=10/100 mbps
• Access method = CSMA/CD
• Central Device=Hub/Switch

Ring Topology

A Ring Topology is a network topology which is connected with two or more than two nodes in a continuous pathway like a ring.

Advantages 

• All data can flow in one direction which gives us a leverage of reducing packet collisions.

• Network server is not required for connectivity between work stations.

•  Data will be transferred at high speeds.

Disadvantages

• Data must be passed through each node to reach its destination which makes it slower.

• If one workstation or a node goes down the entire network will also go down.

Properties

• Cable=UTP
• Speed=4 to 16 Mbps
• Access method = Token Rising
• Central Device=Hub

  Bus Topology

A Bus Topology is a network topology where nodes are directly connected to half duplex link.

Advantages

• Requires less cabling.

• Easiest network topology for connecting computers on a linear fashion.

• Works great on a small network .

Disadvantages

• Limits on cable length and nodes network.

• Maintenance cost is higher.

• Not suitable for networks with heavy traffics.

Properties

• Cable=Coaxial/UTP
• Speed=10/100 mbps
• Access method = CSMA/CD
• Central Device=Hub/Switch

Mesh Topology

A Mesh Topology is a network topology in which each node relays data on each network.Mesh topology uses two techniques to relay messages .The flooding technique and the Routing technique. When all nodes are connected with each other in a  mesh network then it is called a fully connected network.

Hybrid Topology

A Hybrid Topology is a type of network topology that uses two or more other network topologies including Bus topology, Ring Topology and Star Topology.

Note : Hybrid and Mesh Topologies are not much discussed because the are made with other combine Topologies so they don't have any unique characteristics.