Virtual Private Network (VPN)

A Virtual Private Network (VPN)  is a technology that creates an encrypted connection over a less secure network. The benefit of using a VPN is that it ensures the appropriate level of security to the connected systems when the underlying network infrastructure alone cannot provide it. The justification for using a VPN instead of a private network usually boils down to cost and feasibility: It is either not feasible to have a private network (e.g., for a traveling sales rep) or it is too costly to do so. The most common types of VPNs are remote-access VPNs and site-to-site VPNs. 

Advantages, Benefits and Use of VPN. Why VPN?

Access a Business Network While Travelling: VPNs are frequently used by business travelers to access their business’ network, including all its local network resources, while on the road. The local resources don’t have to be exposed directly to the Internet, which increases security.

Access Your Home Network While Travelling: You can also set up your own VPN to access your own network while travelling. This will allow you to access a Windows Remote Desktop over the Internet, use local file shares, and play games over the Internet as if you were on the same LAN (local area network).

Hide Your Browsing Activity from Your Local Network and ISP: If you’re using a public Wi-Fi connection, your browsing activity on non-HTTPS websites is visible to everyone neraby, if they know how to look. If you want to hide your browsing activity for a bit more privacy, you can connect to a VPN. The local network will only see a single, secure VPN connection. All the other traffic will travel over the VPN connection. While this can be used to bypass connection-monitoring by your Internet service provider, bear in mind that VPN providers may opt to log the traffic on their ends.

Access Geo-Blocked Websites: Whether you’re an American trying to access your Netflix account while travelling out of the country or you wish you could use American media sites like Netflix, Pandora, and Hulu, you’ll be able to access these region-restricted services if you connect to a VPN located in the USA.

Bypass Internet Censorship: Many Chinese people use VPNs to get around the Great Firewall of China and gain access to the entire Internet. (However, the Great Firewall has apparently started interfering with VPNs recently.)

Downloading Files: Yes, let’s be honest – many people use VPN connections to download files via Bit Torrent. This can actually be useful even if you’re downloading completely legal torrents – if your ISP is throttling BitTorrent and making it extremely slow, you can use BitTorrent on a VPN to get faster speeds. The same is true for other types of traffic your ISP might interfere with (unless they interfere with VPN traffic itself.)

Advantages of VPN

The Low Cost of a VPN

One way a VPN lowers costs is by eliminating the need for expensive long-distance leased lines. With VPNs, an organization needs only a relatively short dedicated connection to the service provider. This connection could be a local leased line (much less expensive than a long-distance one), or it could be a local broadband connection such as DSL service.

Another way VPNs reduce costs is by lessening the need for long-distance telephone charges for remote access. Recall that to provide remote access service, VPN clients need only call into the nearest service provider's access point. In some cases this may require a long distance call, but in many cases a local call will suffice.

A third, more subtle way that VPNs may lower costs is through offloading of the support burden. With VPNs, the service provider rather than the organization must support dial-up access for example. Service providers can in theory charge much less for their support than it costs a company internally because the public provider's cost is shared amongst potentially thousands of customers.

Scalability and VPNs

The cost to an organization of traditional leased lines may be reasonable at first but can increase exponentially as the organization grows. A company with two branch offices, for example, can deploy just one dedicated line to connect the two locations. If a third branch office needs to come online, just two additional lines will be required to directly connect that location to the other two.

However, as an organization grows and more companies must be added to the network, the number of leased lines required increases dramatically. Four branch offices require six lines for full connectivity, five offices require ten lines, and so on. Mathematicians call this phenomenon a combinatorial explosion, and in a traditional WAN this explosion limits the flexibility for growth. VPNs that utilize the Internet avoid this problem by simply tapping into the geographically-distributed access already available.

Disadvantages of VPNs

1. VPNs require an in-depth understanding of public network security issues and proper deployment of precautions.

2. The availability and performance of an organization's wide-area VPN (over the Internet in particular) depends on factors largely outside of their control.

3. VPN technologies from different vendors may not work well together due to immature standards.

4. VPNs need to accommodate protocols other than IP and existing ("legacy") internal network technology.

Limitations of a VPN

1. VPNs require detailed understanding of network security issues and careful installation / configuration to ensure sufficient protection on a public network like the Internet.

2. The reliability and performance of an Internet-based VPN is not under an organization's direct control. Instead, the solution relies on an ISP and their quality of service.

3. Historically, VPN products and solutions from different vendors have not always been compatible due to issues with VPN technology standards. Attempting to mix and match equipment may cause technical problems, and using equipment from one provider may not give as great a cost savings.