When a group of two or more computers interconnects together to communicate and share the resources refers to a network. For interconnecting the systems we use common standards ( called protocols) and network devices ( like hubs, switches, routers). Within the networks, devices can share the resources like printers, file servers etc. and communicate with each other.
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Example of Network:
Here is the simple example showing How to connect the two computers using the LAN cable. We need Cross over cable to connect the same type of devices. In below example, we have used CAT5 cross over a cable connected to ethernet cards of both the PC.
After connecting two devices with the LAN cable, we need to configure the IP address in both the PCs. After the IP configuration data exchange and communication can be started between both the computers.
In above example, we have seen that it is very easy to connect two computers but now the Question arises how can we connect more than two computers because we have an only one ethernet card in each device and it can be used to connect the only single device.
To connect more devices we can use network devices like Hubs and Switches.
Let’s understand each term one by one. So let’s start with Hub.
What is a Network HUB?
An Ethernet HUB is a network device having multiple ethernet ports use to connect segments of LAN. Generally, Hub contains 8 or 16 ethernet ports. When a packet arrives at one port, the copy of the packet is copied to other ports. In general, term, when any packet is received on any port of the hub, it is forwarded to all the remaining ports of the hub. This way each device connecting to hub receives the copy of the frame.
Limitation of Network Hub:
a. Hubs are unable to differentiate the devices on the network. It means if one computer tries to send a packet to another computer, the hub will forward that packet to all the connected computers consuming unnecessary bandwidth for each transfer.
b. Hub has a single collision domain and is half-duplex. Which means a computer to hub either can send the packet or can receive the packet at a single time. Parallel communication of sending and receiving the packet is not possible in a hub.
c. Due to a single collision domain, two devices can not communicate at a single time. Only a single device can use a hub network for communication at a time.
What is a Network Switch?
A network switch is more intelligent device use to connect the network devices like printers, computers, Access Point, VoIP phones etc. A network switch serves as a controller, enabling network devices to connect and communicate with each other efficiently.
A switch is capable of learning the mac-address of the devices connects to it. It connects the devices on a computer network by using packet switching to receive, process and forward packets to the destination device.
Each device connecting to switch have its own collision domain means all the devices can communicate with each other parallel at a single point of time.
Switches are full-duplex devices means all the connected devices can send and receive the packets at the same time (which was a limitation in the hub)
The switch comes under 24 or 48 ports. The switch provides many features like VLAN, STP, EtherChannel etc. We will discuss all these protocols in upcoming posts.
Type of Network Switches and their capabilities:
a. Un-managed Switch: A un-managed switch work like plug and play device. It can be directly used after unboxing. We can not do any configuration in the un-managed switches resulting in fewer features and network capacity when compared to managed switches. Un-managed swithces are generally used in home networking equipment.
They are easy to use, no need for installation or set up required for their working.
Limitations of Un-managed Switches:
a. No configuration options are there in Un-managed Switches.
b. Un-managed switches have fewer features and less network capacity than managed switches.
b. Managed Switch: A managed network switch is configurable have security features such as login passwords, provides more features and more network capacity. We can monitor and do the configuration locally or remotely. It gives great control.
Below is the example of how to connect the multiple devices using switches.
A Computer Network must have the following characteristics:
a. Performance
b. Reliability
c. Security
Let’s discuss each one by one:
Network Performance:
Network performance can be measured on the following basis:
a.Response Time: It is the length of the time elapsed between the enquiry and response to the request.
b. Transit Time: It is the time taken to travel a packet from source to destination or vice-versa.
Network Reliability:
The rate of network failure during the operations. Less the network failure take place more the network is reliable. To avoid a network failure, networks are designed with redundancy.
Network Security:
Security is the most important and crucial part of the networks. As data pass through many layers and many devices before it is delivered to the destination device. Any tampering of data such as copying the data, modification of data, data theft etc. Any modification in the message when it travels from senders to destination computer or node is the breach in the security. Network Security is the different part, we will be discussing the same in future posts.
Now you have got the basic idea of networks, Let’s discuss the type to network topologies
Type of Network Topology
Network Topology is the arrangement of network with a shematic description of how the device connects together, which devices are used, how the data will flow from sender device to destination device.
a. Bus Topology
Bus topology is the network type where all the devices are connected together with a single cable. The cable to which all the devices connects is termed as Backbone cable.
Features of BUS Topology:
a. It works well in the small networks.
b. It is simple and easy to implement compared to any other topology.
c. It requires less cable compare to other topologies and cost-effective.
d. It transmits the data in one direction.
Disadvantages of BUS Topology:
a. It is very difficult to find the problem if the whole network goes down.
b. Any fault in the cable comes, either the whole network will get down or will split into two different networks.
b. Star Topology
Star topology is a topology for a LAN network, where all the devices connect to central network point like a hub or switch. All the devices are connected in a manner such as if a single cable fails to connect the device will not affect the rest of the nodes.
Features of Star Topology:
a. Every device has its own dedicated connection to the central point.
b. If any cable fails, it will not impact other devices.
c. Easy to add new devices.
Limitations of Star Topology:
a. Higher Cost of implementation compare to bus topology.
b. Totally dependent on the single central connecting device, if the central device fails all the connecting device will get down.
c. The network performance is totally dependent on the central connecting device.
c. Ring Topology:
Ring Topology is a topology in which each device connects to exactly two other devices in such a way device connections creates a circular data path.
Advantages of Ring Topology:
a. No need for central connection point for communication.
b. The data transmission is uni-directional, which means if we have 50 computers in a ring topology and 1 st computer wants to send data to the last computer. It will travel from 1st computer to remaining 48 computers before it gets actually deliver to the destination computer.
c. Repeaters are widely used in Ring topology because data travels from all the nodes and chances of losing the data increases, so we use repeaters in between the ring topology.
d. We can also make the data transmission bi-directional by making two connections between each node.
Limitations of Ring Topology:
a. Failure of a single node affects the whole network.
b. Adding or removing the new computers disturbs the whole network.
c. Not easy to troubleshoot.
d. Mesh Topology
In mesh network topology, each network node, computers, printers, etc. (means all the devices) are interconnected to each other. It is a point to point connection where every device is connected with all other devices directly.
A mesh topology can be a full mesh topology or partial mesh topology
In a full mesh topology, every node in the network has a point to point connection with all other nodes within the network. The number of connection requirement can be calculated by simple formula n(n-1)/2 where n is the number of computers (nodes).
In a partial mesh topology, we require at least two computers(nodes) to have a connection with all other nodes. If any of the nodes fails, it will not affect the current network and data transmission can take place with other nodes.
Advantages of Mesh Topology
a. Easy to manage a high amount of traffic because multiple nodes can transmit the data simultaneously.
b. Adding or removing the new device does not affect the network.
c. Failure of any device does not affect the network.
Disadvantages of Mesh Topology:
a. Cost is very high.
b. Building and maintaining the topology requires extra efforts and monitoring of the same is difficult as so many connections are there in the network.
5. Hybrid Topology
Hybrid topology is the combination of two or more other network topologies, including bus topology, star topology, ring topology, mesh topology and tree topology. For example, in a office one department computers are using bus topology to communicate with each other and to communicate between the other departments using the ring topology.
Features of Hybrid Topology:
a. It is a combination of two or more topologies.
b. Can be designed according to network requirement.
c. Cost effective compared to mesh topology.
6. Tree Topology:
It is a hierarchical topology, which has one root node and all other nodes are connected together to form a tree-like structure. The minimum requirement is to have at least three levels to the hhierarchy
It can also be termed as the combination of star and bus topology, where multiple nodes are connected together through a single lateral connection.
Advantages of Tree Topology:
a. Expansion of node is easy and possible.
b. Can be easily managed.
c. Easy to detect errors in the network.
Disadvantages of Tree topology:
a. If the primary node fails, affects the whole network.
b. Costly.
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