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Appendix A: Virtual Private Networking
A.1 What is the VPN?
A Virtual Private Network (VPN) is a shared network where private data is segmented from other traffic so
that only the intended recipient has access. It allows organizations to securely transmit data over a public
medium like the Internet. VPNs utilize tunnels, which allow data to be safely delivered to the intended
recipient.
Because private networks lack data security, IPSec-based VPNs employ encryption technologies that
protect a private network from data theft or tampering. These private networks can be implemented over
any type of IP network, which allows for excellent flexibility.
A.1.1 VPN Applications
VPNs are traditionally used three ways:
- Extranets: Extranets are secure connections between two or more organizations. IPSec-based VPNs are
ideal for extranet connections, as they can be quickly and inexpensively installed. Extranets are often used
to securely share a company's information with suppliers, vendors, customers, or other businesses.
- Intranets: Intranets are private networks that connect an organization's locations together. These
locations range from a headquarters, to branch offices, to a remote employee's home. Intranets are often
used for email and for sharing applications and files. A firewall protects Intranets from unauthorized access.
- Remote Access: Remote access enables mobile workers to access email and business applications.
Remote access VPNs greatly reduce expenses by enabling mobile workers to dial a local Internet
connection and then set up a secure IPSec-based VPN communications to their organization.
A.2 What is the IPSec?
Internet Protocol Security (IPSec) is a set of protocols and algorithms that provide data authentication,
integrity, and confidentiality as data is transferred across IP networks. IPSec provides data security at the
IP packet level, and protects against possible security risks by protecting data. IPSec is widely used to
establish VPNs.
There are three major functions of IPSec:
- Confidentiality: Conceals data through encryption.
- Integrity: Ensures that contents did not change in transit.
- Authentication: Verifies that packets received are actually from the claimed sender.
Multi-Homing Security Gateway User's Manual
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