VPN - Virtual Private Network

         A virtual private network or VPN gives you online privacy and anonymity by creating a private network from a public internet connection. VPNs mask your IP (internet protocol) address so your online actions are virtually untraceable. Most important, VPN services establish secure and encrypted connections to provide greater privacy than even a secured Wi-Fi hotspot. VPNs can be used to access region-restricted websites, shield your browsing activity from prying eyes on public Wi-Fi, and more.

 A VPN connection usually works like this. Data is transmitted from your client machine to a point in your VPN network. The VPN point encrypts your data and sends it through the internet. Another point in your VPN network decrypt your data and sends it to the appropriate internet resource, such as a web server, an email server, or your company's intranet. Then the internet resource sends data back to a point in your VPN network, where it gets encrypted. That encrypted data is sent through the internet to another point in your VPN network, which decrypt the data and sends it back to your client machine. 

Let's discuss how the encryption happens in the VPNs. An encryption key tells the computer what computations to perform on data in order to encrypt or decrypt it. The most common forms of encryption are symmetric-key encryption or public-key encryption. In symmetric-key encryption, all computers share the same key used to both encrypt and decrypt a message. In public-key encryption, each computer or user has a public-private key pair. One computer uses its private key to encrypt a message, and another computer uses the corresponding public key to decrypt that message. In a VPN, the computers at each end of the tunnel encrypt the data entering the tunnel and decrypt it at the other end. However, a VPN needs more than just a pair of keys to apply encryption. That's where protocols come in. A site-to-site VPN could use either internet protocol security protocol or generic routing encapsulation. Generic routing encapsulation provides the framework for how to package the passenger protocol for transport over the internet protocol. This framework includes information on what type of packet you're encapsulating and the connection between sender and receiver. Internet protocol security protocol is a widely used protocol for securing traffic on IP networks, including the internet. Internet protocol security protocol can encrypt data between various devices, including router to router, firewall to router, desktop to router, and desktop to server. IPSec consists of two sub-protocols which provide the instructions a VPN needs to secure its packets. Encapsulated Security Payload (ESP) encrypts the packet's payload with a symmetric key. Authentication Header (AH) uses a hashing operation on the packet header to help hide certain packet information (like the sender's identity) until it gets to its destination. Networked devices can use internet protocol security protocol in one of two encryption modes. In transport mode, devices encrypt the data traveling between them. In tunnel mode, the devices build a virtual tunnel between two networks. As you might guess, VPNs use IPSec in tunnel mode with internet protocol security protocol ESP and internet protocol security protocol AH working together. In a remote- access VPN, tunneling typically relies on Point-to-point Protocol (PPP) which is part of the native protocols used by the internet. More accurately, though, remote-access VPNs use one of three protocols based on PPP.L2F (Layer 2 Forwarding) uses any authentication scheme supported by PPP PPTP (Point-to-point Tunneling Protocol) Supports 40-bit and 128-bit encryption and any authentication scheme supported by PPP. L2TP (Layer 2 Tunneling Protocol)  Combines features of PPTP and L2F and fully supports IPSec  also applicable in site-to-site VPNs

  When it comes to the vpn it has both advantages and disadvantages of using it. If concern about the advantages, Since a VPN hides your IP address and encrypts your online traffic, it essentially makes sure your digital footprints can’t be tracked on the Internet. Online hackers won’t be able to use your real IP address to find out personal details about you. When using the free wifi your details may lead to them stealing your data but if you use a VPN, though, you won’t need to worry about those dangers. Why? Because a VPN uses encryption to secure your online communications, effectively making sure nobody can monitor them. When you’re at work, school, the airport, or even in a hotel, you might have to deal with annoying network firewalls that prevent you from accessing certain websites but you can easily bypass any firewall you encounter with a VPN since it hides your IP address – the address the firewall restrictions have been applied to. VPN encrypts your connections and hides your IP address, there are plenty of reasons to use such a service to improve your gaming experience. You’ll be able to play in any geographical regions you’ll want, you’ll get to play banned games, you’ll keep yourself safe from DDoS attacks, and you’ll even manage to avoid unfair IP bans. Basically when your ISP limits your bandwidth, effectively lowering your online speeds, since a VPN encrypts all your Internet traffic, your ISP won’t be able to see what you’re doing online.

These kind of advantages can be achieved by using VPNs. Now let's discuss about some disadvantages of using VPNs. If we talk about Virtual Private Networks being used by enterprises, the main use case is to allow remote employees, and users to be able to connect to the company’s network, as if they were physically present there. This allows for ease of use, but also brings with it many security concerns. Since the devices being used to access the VPN aren’t all present at the company’s buildings, the network admins have little to no control over the devices that remote users are using to connect. They have to trust the users to use secure methods to access the network. VPN encrypts all of your network traffic, to ensure anonymity, and security. However, stronger encryption naturally takes more time, and resources. This is why most VPNs are disappointingly slow, because encryption of network traffic introduces quite a bit of overhead. This is not always the case, and you can find many VPN providers that don’t compromise on security, while still maintaining a good connection speed. However, most of these will be paid. Better quality Virtual Private Networks usually use a large number of network topologies, protocols, and hardware devices to create the network. While this does ensure that you get a much more robust network, it also increases the network complexity. 

There are many points to consider when you’re choosing a VPNs. Concern about how it works, what are the advantages and what are the disadvantages and use it safely.