IPsec supports two encryption modes: Transport and Tunnel. Transport mode encrypts only the data portion (payload) of each packet, but leaves the header untouched. The more secure Tunnel mode encrypts both the header and the payload. On the receiving side, an IPSec-compliant device decrypts each packet.

For IPsec to work, the sending and receiving devices must share a public key. This is accomplished through a protocol known as Internet Security Association and Key Management Protocol/Oakley (ISAKMP/Oakley), which allows the receiver to obtain a public key and authenticate the sender using digital certificates.

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IP Security Working Group
Describes the IETF IP Security working group and includes contact and mailing list information and links to Internet drafts and Request for Comments documents.

Securing iSCSI Using IPSec
IP-based SANs are attractive alternatives to their more expensive and complex Fibre Channel counterparts, but securing IP communications remains a significant concern. This article examines how the IP Security Protocol (IPSec) can ensure the security of an iSCSI storage network's data.

Securing iSCSI Using IPSec, Part 2
How to secure communications using IPSec in a Windows 2003 Server environment.