Overview of IPsec Protocol
IPsec protocol provides the security for the unicast IP protocol traffic. Whether you implement site-to-site or remote access VPN, IPsec is used to protect information as it travels from one private network to another private network over a public network. IPsec consists of a suite of protocols that are defined in RFC 2401 as the following:
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Security protocols Authentication header (AH) and encapsulation security payload (ESP)
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Key management ISAKMP, IKE, SKEME
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Algorithms for encryption and authentication
Before going into the details of security protocols and key management components, it is important to understand the encryption and authentication protocols which are discussed in the next section.