Until fairly recently, this has meant the use of leased lines
to maintain a wide area network (WAN). Leased lines,
ranging from ISDN (integrated services digital network, 128
Kbps) to OC3 (Optical Carrier-3, 155 Mbps) fiber, provided
a company with a way to expand its private network beyond
its immediate geographic area. A WAN had obvious advant-
ages over a public network like the Internet when it came to
reliability, performance and security. But maintaining a WAN,
particularly when using leased lines, can become quite exp-
ensive and often rises in cost as the distance between the
offices increases.

As the popularity of the Internet grew, businesses turned to
it as a means of extending their own networks. First came
intranets, which are password-protected sites designed for
use only by company employees. Now, many companies are
creating their own VPN (virtual private network) to acc-
ommodate the needs of remote employees and distant offices.

Basically, a VPN is a private network that uses a public network
(usually the Internet) to connect remote sites or users together.
Instead of using a dedicated, real-world connection such as
leased line, a VPN uses "virtual" connections routed through the
Internet from the company's private network to the remote site
or employee. In this article, you will gain a fundamental under-
standing of VPNs, and learn about basic VPN components, tech-
nologies, tunneling and security.

A typical VPN might have a main LAN at the corporate headquarters of a company,
other LANs at remote offices or facilities and individual users connecting from out
in the field.

HS Communications Limited in collaboration with its expatriate partners
provide industry tailored VPN solutions to corporate organizations. This
secured, scalable, reliable, manageable and policy featured VPNs sol-
utions are of two different types:

• Remote Access:
  Remote-access, also called a virtual private dial-up network
  (VPDN), is a user-to-LAN connection used by a company that
  has employees who need to connect to the private network
  from various remote locations. Typically, a corporation that
  wishes to set up a large remote-access VPN will outsource to
  an enterprise service provider (ESP). The ESP sets up a network
  access server (NAS) and provides the remote users with desktop
  client software for their computers. The telecommuters can then
  dial a toll-free number to reach the NAS and use their VPN client
  software to access the corporate network.
• Site-to-site VPN:
  Through the use of dedicated equipment and large-scale encryption,
  a company can connect multiple fixed sites over a public network such
  as the Internet. Site-to-site VPNs can be one of two types:
  • Intranet-based - If a company has one or more remote locations
    that they wish to join in a single private network, they can create
    an intranet VPN to connect LAN to LAN.
  • Extranet-based - When a company has a close relationship with
    another company (for example, a partner, supplier or customer),
    they can build an extranet VPN that connects LAN to LAN, and that
    allows all of the various companies to work in a shared environment.