To communicate data through different transmission media and to configure networks with different functionality, we require different devices like Modem, Hub, Switch, Repeater, Router, Gateway, etc. In this post, we will see different Network Devices and Network Topologies.
1. Modem:
Modem stands for ‘MOdulator DEModulator’. It refers to a device used for conversion between analog signals and digital bits. We know computers store and process data in terms of 0s and 1s. However, to transmit data from a sender to a receiver, or while browsing the internet, digital data are converted to an analog signal and the medium (be it free space or a physical media) carries the signal to the receiver. There are modems connected to both the source and destination nodes. The modem at the sender’s end acts as a modulator that converts the digital data into analog signals. The modem at the receiver’s end acts as a demodulator that converts the analog signals into digital data for the destination node to understand.
2. Ethernet Card:
An Ethernet card, also known as Network Interface Card (NIC card in short) is a network adapter used to set up a wired network. It acts as an interface between the computer and the network. It is a circuit board mounted on the motherboard of a computer. The Ethernet cable connects the computer to the network through NIC. Ethernet cards can support data transfer between 10 Mbps and 1 Gbps (1000 Mbps). Each NIC has a MAC address, which helps in uniquely identifying the computer on the network.
3. RJ45:
RJ 45 or Registered Jack-45 is an eight-pin connector that is used exclusively with Ethernet cables for networking. It is a standard networking interface that can be seen at the end of all network cables. Basically, it is a small plastic plug that fits into RJ-45 jacks of the Ethernet cards present in various computing devices.
4. Repeater:
Data are carried in the form of signals over the cable. These signals can travel a specified distance (usually about 100 m). Signals lose their strength beyond this limit and become weak. In such conditions, original signals need to be regenerated. A repeater is an analog device that works with signals on the cables to which it is connected. The weakened signal appearing on the cable is regenerated and put back on the cable by a repeater.
5. Hub:
An Ethernet hub is a network device used to connect different devices through wires. Data arriving on any of the lines are sent out on all the others. The limitation of Hub is that if data from two devices come at the same time, they will collide.
6. Switch:
A switch is a networking device that plays a central role in a Local Area Network (LAN). As a hub, a network switch is used to connect multiple computers or communicating devices. When data arrives, the switch extracts the destination address from the data packet and looks it up in a table to see where to send the packet. Thus, it sends signals to only selected devices instead of sending them to all. It can forward multiple packets at the same time. A switch does not forward the signals which are noisy or corrupted. It drops such signals and asks the sender to resend it. Cables connected to a network switch Ethernet switches are common in homes/offices to connect multiple devices thus creating LANs or to access the Internet.
7. Router:
A router is a network device that can receive the data, analyze it and transmit it to other networks. A router connects a local area network to the internet. Compared to a hub or a switch, a router has advanced capabilities as it can analyze the data being carried over a network, decide/alter how it is packaged, and send it to another network of a different type. For example, data has been divided into packets of a certain size. Suppose these packets are to be carried over a different type of network which cannot handle bigger packets. In such a case, the data is to be repackaged as smaller packets and then sent over the network by a router.
8. Gateway:
As the term “Gateway” suggests, it is a key access point that acts as a “gate” between an organization’s network and the outside world of the Internet. The gateway serves as the entry and exit point of a network, as all data coming in or going out of a network must first pass through the gateway in order to use routing paths. Besides routing data packets, gateways also maintain information about the host network’s internal connection paths and the identified paths of other remote networks. If a node from one network wants to communicate with a node of a foreign network, it will pass the data packet to the gateway, which then routes it to the destination using the best possible route.
Networking Topologies
We have already discussed that a number of computing devices are connected together to form a Local Area Network (LAN), and interconnections among millions of LANs forms the Internet. The arrangement of computers and other peripherals in a network is called its topology. Common network topologies are Mesh, Ring, Bus, Star, and Tree.
1. Mesh Topology
In this networking topology, each communicating device is connected with every other device in the network. Such a network can handle large amounts of traffic since multiple nodes can transmit data simultaneously. Also, such networks are more reliable in the sense that even if a node gets down, it does not cause any break in the transmission of data between other nodes. This topology is also more secure as compared to other topologies because each cable between two nodes carries different data. However, wiring is complex and cabling cost is high in creating such networks and there are many redundant or unutilized connections.
2. Ring Topology
In-ring topology, each node is connected to two other devices, one each on either side, as shown in Figure 10.16. The nodes connected with each other thus form a ring. The link in a ring topology is unidirectional. Thus, data can be transmitted in one direction only (clockwise or counterclockwise).
3. Bus Topology
In a bus topology, each communicating device connects to a transmission medium, known as a bus. Data sent from a node are passed on to the bus and hence are transmitted to the length of the bus in both directions. That means data can be received by any of the nodes connected to the bus. In this topology, a single backbone wire called a bus is shared among the nodes, which makes it cheaper and easier to maintain. Both ring and bus topologies are considered to be less secure and less reliable.
4. Star Topology:
In star topology, each communicating device is connected to a central node, which is a networking device like a hub or a switch.. Star topology is considered very effective, efficient, and fast as each device is directly connected with the central device. Although disturbance in one device will not affect the rest of the network, any failure in a central networking device may lead to the failure of the complete network.
5. Tree or Hybrid Topology:
It is a hierarchical topology, in which there are multiple branches and each branch can have one or more basic topologies like a star, ring, and bus. Such topologies are usually realized in WANs where multiple LANs are connected. Those LANs may be in the form of a ring, bus, or star. A hybrid topology is shown connecting 4-star topologies in a bus. In this type of network, data transmitted from the source first reaches the centralized device and from there the data passes through every branch where each branch can have links for more nodes.
