VPN–Tunnel essentials

Types of Tunnels – Site to Site or Network to Network

VPNs can be either remote-access (connecting a computer to a network) or site-to-site (connecting two  networks).   In a corporate setting, remote-access VPNs allow employees to access their company’s intranet from home or while travelling outside the office, and site-to-site VPNs allow employees in geographically disparate offices to share one cohesive virtual network.

TWO STEPS to a VPN tunnel

There are two steps to making a VPN work.

  1. Authenticate the Tunnel Endpoints
  2. Define the tunneling protocol to be used (which also includes encryption support for encrypting the traffic between endpoints )

Authenticate Tunnel Endpoints

Tunnel endpoints must be authenticated before secure VPN tunnels can be established. User-created remote-access VPNs may use passwords, biometrics, two-factor authentication or other cryptographic methods. Network-to-network tunnels often use passwords or digital certificates. They permanently store the key to allow the tunnel to establish automatically, without intervention from the administrator.

Define Tunneling Protocol

Secure VPN Protocols include:

  • Internet Protocol Security (IPsec) was initially developed by the Internet Engineering Task Force (IETF) for IPv6, which was required in all standards-compliant implementations of IPv6 before RFC 6434 made it only a recommendation.[7] This standards-based security protocol is also widely used with IPv4 and the Layer 2 Tunneling Protocol. Its design meets most security goals: authentication, integrity, and confidentiality. IPsec uses encryption, encapsulating an IP packet inside an IPsec packet. De-encapsulation happens at the end of the tunnel, where the original IP packet is decrypted and forwarded to its intended destination.
  • Transport Layer Security (SSL/TLS) can tunnel an entire network’s traffic (as it does in the OpenVPN project and SoftEther VPN project[8]) or secure an individual connection. A number of vendors provide remote-access VPN capabilities through SSL. An SSL VPN can connect from locations where IPsec runs into trouble with Network Address Translation and firewall rules.
  • Secure Shell (SSH) VPN – OpenSSH offers VPN tunneling (distinct from port forwarding) to secure remote connections to a network or to inter-network links. OpenSSH server provides a limited number of concurrent tunnels. The VPN feature itself does not support personal authentication.

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Anuj Varma – who has written posts on Anuj Varma, Technology Architect.


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