Introduction of a Router

Network devices are physical devices that allow hardware on a computer network to communicate and interact with one another. For example Repeater, Hub, Bridge, Switch, Routers, Gateway, Router, and NIC, etc.

What is a Router?

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 that 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 to 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. Routers are the devices that are operated on the Network Layer of the OSI Model, these are the most common devices used in networking.

How Does Router Work?

• A router determines a packet's future path by examining the destination IP address of the header and comparing it to the routing database. The list of routing tables outlines how to send the data to a specific network location. They use a set of rules to determine the most effective way to transmit the data to the specified IP address.
• To enable communication between other devices and the internet, routers utilize a modem, such as a cable, fiber, or DSL modem. Most routers include many ports that can connect a variety of devices to the internet simultaneously. In order to decide where to deliver data and where traffic is coming from, it needs routing tables.
• A routing table primarily specifies the router's default path. As a result, it might not determine the optimum path to forward the data for a particular packet. For instance, the office router directs all networks to its internet service provider through a single default channel.
• Static and dynamic tables come in two varieties in the router. The dynamic routing tables are automatically updated by dynamic routers based on network activity, whereas the static routing tables are configured manually.

Types of Router

There are several types of routers. 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.
3. Wired Routers: Wired Router is used to connects multiple wired devices using a Ethernet cable, It takes the transmission data from the modem and distribute it to a further network, it is widely used in schools and small offices.
4. 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.
5. Core Routers: Core routers distribute packets within the same network. The main task is to carry heavy data transfers.
6. Virtual Router: They are implemented using a software on the virtual machine , and they are more flexible and scalable.
7. Portable Routers: They are used to create private Wi-Fi and hence designed for easy portability.

Functions of Router 

The router performs below 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.
3. Network Address Translation (NAT): Routers use NAT to translate between different IP address ranges. This allows devices on a private network to access the internet using a single public IP address.
4. Security: Routers can be configured with firewalls and other security features to protect the network from unauthorized access, malware, and other threats.
5. Quality of Service (QoS): Routers can prioritize network traffic based on the type of data being transmitted. This ensures that critical applications and services receive adequate bandwidth and are not affected by lower-priority traffic.
6. Virtual Private Network (VPN) connectivity: Routers can be configured to allow remote users to connect securely to the network using a VPN.
7. Bandwidth management: Routers can be used to manage network bandwidth by controlling the amount of data that is allowed to flow through the network. This can prevent network congestion and ensure that critical applications and services receive adequate bandwidth.
8. Monitoring and diagnostics: Routers can be configured to monitor network traffic and provide diagnostics information in the event of network failures or other issues. This allows network administrators to quickly identify and resolve problems.

Architecture of Router 

A generic router consists of the following components: 

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.

Security Challenges in Router

There are several challenges faced by the router, due to which an unauthorized access is taken by another party. Here below are some security challenges in router:

1. Vulnerability Exploits

Firmware is automatically installed on all hardware-based routers to assist the operation of the router. Like any other programme, router firmware frequently has flaws that hackers could use against it. Vendors of routers usually release updates to fix these flaws. Router firmware needs to be updated on a frequent basis as a result. Attackers have the ability to monitor traffic on unpatched routers and utilise them as part of a botnet.

2. DDoS Attacks

Distributed Denial-Of-Service (DDoS) attacks against network infrastructure frequently target both large and small organisations. Network outages can be caused by unmitigated network layer DDoS attacks, which can overload routers or bring them down. Using Cloudflare Magic Transit is one way to defend networks and routers against DDoS attacks of this nature.

3. Administration Credentials

To carry out administration tasks, a set of admin credentials is included with every router. The default values for these credentials are "admin" for the username and "admin" for the password. As soon as possible, change the username and password to something more secure since, if they are not changed, attackers can use them to remotely take over the router. They are aware of the typical default values for these credentials.

Advantages of Router

• Easier Connection: Sharing a single network connection among numerous machines is the main advantage of router. This enables numerous people to connect to the internet, boosting total productivity. In addition, routers have connections between various media and network designs.
• 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 computer 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.
• 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.
• 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.
• 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

• 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”.
• 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.
• 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.
• 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.
• 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.

Applications of Router

There are several applications of router because nowadays routers are widely used in most of the networking communication for better communication:

• Hardware equipment, such as servers from BSC, MGW, IN, SGSN, and other remote location networks, is connected to these networks via routers.
• It is utilised in both wired and wireless communication since it supports a high speed of data transmission due to its utilisation of STM connections for connectivity.
• Routers are frequently used by internet service providers to transfer data, such as audio, video, image, and email, from one location to another. Additionally, it can transmit data globally by utilising the destination's IP address.
• Routers provide access control. It can be set up so that some users can access all of the data while others can access just a subset of it.

Routing Protocol

The router can recognise other routers on the network and decide on a dynamic basis where to deliver all network messages through the routing protocol. Several protocols exist, some of which are listed below:

• Open Shortest Path First: As packets travel across several networks, it is utilised to determine the optimal path for them to take in order to arrive at their destination.
• Border Gateway Protocol (BGP): It facilitates information sharing between edge routers to control internet packet routing. For routers, it offers network stability. It can easily switch to another network connection to transfer the packets.
• Interior Gateway Routing Protocol (IGRP) : IGRP outlines the protocol for exchanging routing data between gateways inside the separate networks. The routing information can then be used by the other network protocols to decide how data packets should be routed.
• Enhanced Interior Gateway Routing Protocol (EIGRP): This protocol requests a router to route its neighbours if it cannot find a path to a destination from the routing tables. The neighbours then forward the request to further neighbours until a router finds the path.
• Exterior Gateway Protocol (EGP): It is also frequently used for the communication of routing table data between internet hosts.

You can also refer the article Difference between Router and Modem.