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Appendix E: Virtual Private Networking
E.1 What is a 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.
E.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.
E.2 What is IPSec?
Internet Protocol Security (IPSec) is a set of protocols and algorithms that provide