Virtual Private Networks(VPN)
Globalization has changed the world in almost every field of our life especially the way we communicate either it is electronically or not. From the last decades businesses are taking more interest in global markets and they are spreading their offices and branches around the world like mushrooms. But there is one common need that all the business organizations are desperate about: That is the secure and faster exchange of their data. Earlier these organizations were using dedicated leased lines or dial-up lines for their private networks. Although it was secure but the same time it is highly expensive and also its maintenance was difficult. As organizations wanted to expand their networks globally or beyond its geographical boundries it become more expensive and seems impossible on a global platform. So the need rises for virtual private networks (VPN).
Virtual private networks(VPN) provides the facility to organizations and their remote users to access their private or enterprise networks from remote locations and can exchange their data with security, integrity and data confidentiality using public network such as the internet. This gives security and confidentiality for data communication, increases the flexibility for organizations expansion and reduces the cost of connectivity .
Virtual private network enables to connect organizations different branches and their remote users in different areas in a uniform set of network allowing them to share their network facilities as well .
Basically there are two types of VPNs which are commonly in use these days.
- 1. Remote-Access VPN
- 2. Site-to-site VPN
Remote users are those users which can access their company private network from different or remote locations. Remote-access VPN enables company employees to connect to their company private network from remote locations and can use the computing facilities provided by their company private network. This is also known as virtual private dial-up network (VPDN). Organization with large number of remote users (employees) can use enterprise service provider (ESP). The ESP sets up a network access server (NAS) and also provides desktop client software for the remote user's computer which generates a toll-free number for the remote users to get to the NAS in order to access their company private network by using their VPN client software .
Site-to-site VPN enables an organization to connect with their branch offices, business partners and home offices in a secure fashion using large scale of encryption and dedicated equipments over an unsecure public network such as an internet .
There are basically two types of site-to-site VPN
- Site-to-site Intranet-based VPN
- Site-to-site Extranet-based VPN
If a company has one or multiple remote branch offices or remote locations and they want to wrap all of them in a single private network they will make an intranet VPN. The connection will be LAN to LAN .
Organizations that have close relationships with other organizations and partners can make an extranet VPN. Again the connection will be LAN to LAN. They all will work together in a shared environment but the external organizations and partners will have access only to a specific resources or data and will have no access to organization private corporate information .
The documents are arranged by the general categories they apply to. These categories are:
For secure VPNs:
- General IPsec
- ESP and AH (encryption and authentication headers)
- Key exchange (ISAKMP, IKE, and others)
- Cryptographic algorithms
- IPsec policy handling
- Remote access
- SSL and TLS
For trusted VPNs:
- General MPLS
- MPLS constrained by BGP routing
- Transport of layer 2 frames over MPLS
 by jeff tyson http://computer.howstuffworks.com/vpn.htm