A virtual private network (VPN) is a network that uses a public telecommunication infrastructure, such as the Internet, to provide remote offices or individual users with secure access to their organization's network. VPN aims to avoid an expensive system of owned or leased lines that can only be used by one organization. The goal of a VPN is to provide the organization with the same, secure capabilities, but at a much lower cost. Virtual Private Networks reduce network costs because they avoid a need for many leased lines that individually connect to the Internet. Users can exchange private data securely, making the expensive leased lines redundant.

VPN in Mobile

Mobile VPNs handle the special circumstances when an endpoint of the VPN is not fixed to a single IP address, but instead roams across various networks such as data networks from cellular carriers or between multiple Wi-Fi access points. Mobile VPNs have been widely used in public safety, where they give law enforcement officers access to mission-critical applications, such as computer-assisted dispatch and criminal databases, as they travel between different subnets of a mobile network.[15] They are also used in field service management and by healthcare organizations, among other industries.

Security in VPN

Secure VPNs use cryptographic tunneling protocols to provide confidentiality by blocking intercepts and packet sniffing, allowing sender authentication to block identity spoofing, and provide message integrity by preventing message alteration. Secure VPN protocols include the following:

• IPsec (Internet Protocol Security)
• Transport Layer Security (SSL/TLS)
• Datagram Transport Layer Security (DTLS)
• Microsoft's Microsoft Point-to-Point Encryption (MPPE)
• Microsoft introduced Secure Socket Tunneling Protocol (SSTP)
• MPVPN (Multi Path Virtual Private Network)
• Secure Shell (SSH) VPN