Zyxel-communications P-661H Series Bedienungsanleitung PDF herunterladen (Seite 197)

P-661H/HW Series User’s Guide

Chapter 12 Introduction to IPSec 197

CHAPTER 12

Introduction to IPSec

This chapter introduces the basics of IPSec VPNs.

12.1 VPN Overview

A VPN (Virtual Private Network) provides secure communications between sites without the

expense of leased site-to-site lines. A secure VPN is a combination of tunneling, encryption,

authentication, access control and auditing technologies/services used to transport traffic over

the Internet or any insecure network that uses the TCP/IP protocol suite for communication.

12.1.1 IPSec

Internet Protocol Security (IPSec) is a standards-based VPN that offers flexible solutions for

secure data communications across a public network like the Internet. IPSec is built around a

number of standardized cryptographic techniques to provide confidentiality, data integrity and

authentication at the IP layer.

12.1.2 Security Association

A Security Association (SA) is a contract between two parties indicating what security

parameters, such as keys and algorithms they will use.

12.1.3 Other Terminology

12.1.3.1 Encryption

Encryption is a mathematical operation that transforms data from "plaintext" (readable) to

"ciphertext" (scrambled text) using a "key". The key and clear text are processed by the

encryption operation, which leads to the data scrambling that makes encryption secure.

Decryption is the opposite of encryption: it is a mathematical operation that transforms

“ciphertext” to plaintext. Decryption also requires a key.

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Zyxel-communications P-661H Series Bedienungsanleitung Seite 197