9.3. IPsec Components
This section looks at the IPsec standards and describes in general terms the various components,
techniques and algorithms that are used in IPsec based VPNs.
9.3.1. Overview
Internet Protocol Security (IPsec) is a set of protocols defined by the Internet Engineering Task
Force (IETF) to provide IP security at the network layer. An IPsec based VPN is made up of two
parts:
•
Internet Key Exchange protocol (IKE)
•
IPsec protocols (AH/ESP/both)
The first part, IKE, is the initial negotiation phase, where the two VPN endpoints agree on which
methods will be used to provide security for the underlying IP traffic. Furthermore, IKE is used to
manage connections, by defining a set of Security Associations, SAs, for each connection. SAs are
unidirectional, so there are usually at least two for each IPsec connection.
The second part is the actual IP data being transferred, using the encryption and authentication
methods agreed upon in the IKE negotiation. This can be accomplished in a number of ways; by
using IPsec protocols ESP, AH, or a combination of both.
The flow of events can be briefly described as follows:
•
IKE negotiates how IKE should be protected
•
IKE negotiates how IPsec should be protected
•
IPsec moves data in the VPN
The following sections will describe each of these stages in detail.
9.3.2. Internet Key Exchange (IKE)
This section describes IKE, the Internet Key Exchange protocol, and the parameters that are used
with it.
Encrypting and authenticating data is fairly straightforward, the only things needed are encryption
and authentication algorithms, and the keys used with them. The Internet Key Exchange (IKE)
protocol, IKE, is used as a method of distributing these "session keys", as well as providing a way
for the VPN endpoints to agree on how the data should be protected.
IKE has three main tasks:
•
Provide a means for the endpoints to authenticate each other
•
Establish new IPsec connections (create SA pairs)
•
Manage existing connections
Security Associations (SAs)
IKE keeps track of connections by assigning a set of Security Associations, SAs, to each connection.
An SA describes all parameters associated with a particular connection, such as the IPsec protocol
used (ESP/AH/both) as well as the session keys used to encrypt/decrypt and/or authenticate/verify
the transmitted data.
9.3. IPsec Components
Chapter 9. VPN
397
Summary of Contents for NetDefend DFL-260E
Page 27: ...1 3 NetDefendOS State Engine Packet Flow Chapter 1 NetDefendOS Overview 27...
Page 79: ...2 7 3 Restore to Factory Defaults Chapter 2 Management and Maintenance 79...
Page 146: ...3 9 DNS Chapter 3 Fundamentals 146...
Page 227: ...4 7 5 Advanced Settings for Transparent Mode Chapter 4 Routing 227...
Page 241: ...5 4 IP Pools Chapter 5 DHCP Services 241...
Page 339: ...6 7 Blacklisting Hosts and Networks Chapter 6 Security Mechanisms 339...
Page 360: ...7 4 7 SAT and FwdFast Rules Chapter 7 Address Translation 360...
Page 382: ...8 3 Customizing HTML Pages Chapter 8 User Authentication 382...
Page 386: ...The TLS ALG 9 1 5 The TLS Alternative for VPN Chapter 9 VPN 386...
Page 439: ...Figure 9 3 PPTP Client Usage 9 5 4 PPTP L2TP Clients Chapter 9 VPN 439...
Page 450: ...9 7 6 Specific Symptoms Chapter 9 VPN 450...
Page 488: ...10 4 6 Setting Up SLB_SAT Rules Chapter 10 Traffic Management 488...
Page 503: ...11 6 HA Advanced Settings Chapter 11 High Availability 503...
Page 510: ...12 3 5 Limitations Chapter 12 ZoneDefense 510...
Page 533: ...13 9 Miscellaneous Settings Chapter 13 Advanced Settings 533...
