Welcome

VPN TECHNOLOGY

What is a VPN ?

A virtual private network (VPN) gives you online privacy and anonymity by creating a private network from a public internet connection. VPNs mask your internet protocol (IP) address so your online actions are virtually untraceable. Most important, VPN services establish secure and encrypted connections to provide greater privacy than even a secured Wi-Fi hotspot.

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Why do you need a VPN ?

Surfing the web or transacting on an unsecured Wi-Fi network means you could be exposing your private information and browsing habits. That’s why a virtual private network, better known as a VPN, should be a must for anyone concerned about their online security and privacy.

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How does a VPN work ?

VPNs essentially create a data tunnel between your local network and an exit node in another location, which could be thousands of miles away, making it seem as if you’re in another place. This benefit allows online freedom, or the ability to access your favorite apps and websites while on the go.

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ADDRESS BINDING

For addressing TCP and UDP use a 4tuple of :

Local IP address
Loca Port number
Foreign IP address
Foreign Port number

TCP requires these 4-tuples to be unique. UDP does not. User programs do not always know proper values to use for the local address and local port, because a host can reside on multiple networks. The set of allocated port numbers is not directly accessible to a user. To avoid these problems, leave parts of the address unspecified and let the system assign the parts appropriately when needed. Various portions of these tuples can be specified by various parts of the sockets API:

Bind Socket - Local address or local port or both

Connect Socket - Foreign address and foreign port

Each network interface on a host typically has a unique IP address. Sockets with wildcard local addresses can receive messages that are directed to the specified port number. Messages that are sent to any of the possible addresses that are assigned to a host are also received by sockets with wildcard local addresses. To allow only hosts on a specific network to connect to the server, a server binds the address of the interface on the appropriate network.

The system uses two criteria to select the local port number:

Internet port numbers less than 1024 (IPPORT_RESERVED) are reserved for privileged users. Nonprivileged users can use any Internet port number that is greater than 1024. The largest Internet port number is 65535.

The port number is not currently bound to some other socket.

With this call, local addresses already in use can be bound. This binding does not violate the uniqueness requirement. The system still verifies at connect time that any other sockets with the same local address and local port do not have the same foreign address and foreign port. If the association already exists, the error EADDRINUSE is returned