Virtual Private Networking

Question

I've tried to research this subject before I posted, but I really haven't found any good explanation - I've had an icon at the top right of my screen since I've had my computer - it's for "VPN" - which I've basically ignored until today - I'm curious as to its function. Like I said - I tried to find out more about it, but every explanation is unclear to me. Can anyone tell me, very simply, what exactly is VPN?

Answer 1

The name kind of says it all, but a practical example often helps.
First, think of a private network as any local area network such as that used in an office, your home, etc. Everything on that local area network (LAN) is private, and protected from the internet by firewalls, NAT devices, etc.
That's all well and good for people inside the office. However there are many cases where people outside the office would also benefit from access to the internal/private machines. For example, sales people might benefit from accessing the corporate database on product availability, client profile, etc., or maybe want access to a corporate file server or email server.
One option is to open those services to the outside world, but you then run into issues with protecting the data from unwanted users - e.g. hackers trying to crack into the corporate database, download financial information, etc.
It's possible to do using various authentication systems, encryption systems, etc., but you have to apply the same rules over and over again to every service that you want to be able to access remotely, and missing just one leaves your entire network vulnerable.
Enter the VPN.
The VPN extends the concept of the private LAN to specific remote systems. Remote users connected to the VPN (e.g. that sales guy on the road, the IT guy working from home, etc.) authenticate once to a VPN server and then appear to be in the LAN, just as if they were at a desk in the office.
As far as all the internal servers are concerned, the user is local. He can do anything he'd be able to do in the office, including printing on office printers, accessing file servers, etc., without the need to specially configure each service, and without the need to open lots of holes in the corporate firewall.
So the user on the VPN appears to be on the local network, but isn't - hence the 'Virtual' part of the equation.
VPNs can be scaled to support anywhere from one or two users to thousands of users across multiple continents - it's not uncommon, for example, for multi-national corporations to have VPN connections between offices. That way anyone in any office can connect, securely and easily, with anyone else, without having to worry (too much) about where that resource is, or whether it's available outside of the office.
Does that help?