Introduction of a Router

Prerequisite – Network Devices

A Router is a networking device that forwards data packets between computer networks. One or more packet-switched networks or subnetworks can be connected using a router. By sending data packets to their intended IP addresses, it manages traffic between different networks and permits several devices to share an Internet connection.

Let us understand this by a very general example, suppose you search for www.google.com in your web browser then this will be a request which will be sent from your system to google`s server to serve that webpage, now your request which is nothing but a stream of packets don`t just go the google`s server straightaway they go through a series of networking devices known as a router which accepts this packets and forwards them to correct path and hence it reaches to the destination server. A router has several interfaces by which it can connect to several host systems.

Router

Types of Router

There are several types of routers available in the market. Some of them are mentioned below:

1. Broadband Routers: These are one of the important kinds of routers. It is used to do different types of things. it is used to connect computers or it is also used to connect to the internet.
2. Wireless routers: These routers are used to create a wireless signal in your office or home. Wireless routers receive data packets over wired broadband, convert the packets written in binary code into radio signals that are picked up by electronic devices, and then convert them back into previous packets. 
3. Edge Routers: As the name indicates, these are located at the edges usually connected to an Internet Service Provider, and distribute packets across multiple packets.
4. Core Routers: Core routers distribute packets within the same network. The main task is to carry heavy data transfers.

Functions of a Router

The router performs two major functions: 

1. Forwarding: The router receives the packets from its input ports, checks its header, performs some basic functions like checking checksum, and then looks up to the routing table to find the appropriate output port to dump the packets onto, and forwards the packets onto that output port.
2. Routing: Routing is the process by which the router ascertains what is the best path for the packet to reach the destination, It maintains a routing table that is made using different algorithms by the router only.

Architecture of a Router

A Generic router consists of the following components: 

The architecture of a Router

1. Input Port: This is the interface by which packets are admitted into the router, it performs several key functions as terminating the physical link at the router, this is done by the leftmost part in the below diagram, and the middle part does the work of interoperating with the link-layer like decapsulation, in the last part of the input port the forwarding table is looked up and is used to determine the appropriate output port based on the destination address.
2. Switching Fabric: This is the heart of the Router, It connects the input ports with the output ports. It is kind of a network inside a networking device. The switching fabric can be implemented in several ways some of the prominent ones are: 
   • Switching via memory: In this, we have a processor which copies the packet from input ports and sends it to the appropriate output port. It works as a traditional CPU with input and output ports acting as input and output devices
   • Switching via bus: In this implementation, we have a bus that connects all the input ports to all the output ports. On receiving a packet and determining which output port it must be delivered to, the input port puts a particular token on the packet and transfers it to the bus. All output ports can see the packets but they will be delivered to the output port whose token has been put in, the token is then scraped off by that output port and the packet is forwarded
   • Switching via interconnection network: This is a more sophisticated network, here instead of a single bus we use a 2N bus to connect n input ports to n output ports.
3. Output Port: This is the segment from which packets are transmitted out of the router. The output port looks at its queuing buffers (when more than one packets have to be transmitted through the same output port queuing buffers are formed) and takes packets, does link layer functions, and finally transmits the packets to an outgoing link
4. Routing Processor: It executes the routing protocols, and it works like a traditional CPU. It employs various routing algorithms like the link-state algorithm, distance-vector algorithm, etc. to prepare the forwarding table, which is looked up to determine the route and the output port.

Advantages of Router

1. Easier Connection: Sharing a single network connection among numerous machines is the router’s main job. This enables numerous people to connect to the internet, boosting total productivity. In addition, routers have connections between various media and network designs.
2. Security: Undoubtedly, installing a router is the first step in securing a network connection. Because using a modem to connect directly to the internet exposes your PC to several security risks. So that the environment is somewhat secure, routers can be utilized as an intermediary between two networks. While not a firewall or antivirus replacement.
3. NAT Usage: Routers use Network Address Translation (NAT) to map multiple private IP addresses into one public IP address. This allows for a better Internet connection and information flow between all devices connected to the network.
4. Supports Dynamic Routing: The router employs dynamic routing strategies to aid in network communication. The internet work’s optimum path is chosen through dynamic routing. Additionally, it creates collision and broadcast domains. Overall, this can lessen network traffic.
5. Filtering of Packets: Switching between packets and filtering packets are two more router services. A collection of filtering rules are used by routers to filter the network. The packets are either allowed or passed through.

Disadvantages of Router

1. Slower: Routers analyze multiple layers of information, from the physical layer to the network layer, which slows down connections. The same issue can also be encountered when multiple devices are connected to these network devices, causing “connection waiting”.
2. High Cost: They are more expensive than some other tools for systems administration. This includes security, extension, and the focal point. As a result, routers are typically not the greatest option for issues.
3. Need for configuration: The router must be properly configured to work properly. In general, the more complex the intended use, the more configuration is required. This requires professional installation, which can add to the cost of buying a router.
4. Quality Issues: The time transitions are not always accurate. Even yet, some modern devices use the 2.4GHz band, which is frequently deactivated. These kinds of separations are frequently possible for those who live in apartments and condominiums.
5. Bandwidth shortages: Dynamic routing techniques used by routers to support connections tend to cause network overhead, consuming a lot of bandwidth. This leads to a bandwidth shortage that significantly slows down the internet connection between connected devices.

For more details, please refer How does a Router Work?, and Types of Routing.