Resources for learning how IPSec works

Do you know where, ideally on the Web, I can find a straightforward explanation of how IPSec works and the meaning...

of some of the terms, like ISAKMP for example? Many thanks.

You pose an excellent question, for a couple of reasons. First, IPSec has gotten so complex, it's hard to figure it all out. Secondly, it's good to know where to look for such thingies. I'm very fond of the site www.whatis.com for whenever I need to find good, straightforward definitions of technical terms. For IPSec, www.whatis.com provides this nice definition at a high level. For more detail, look at http://www.ietf.org/internet-drafts/draft-ietf-ipsec-properties-02.txt. Or, check out this SearchSecurity.com Webcast.

Finally, ISAKMP is an older term. It stood for Internet Security Association and Key Management Protocol. It has been renamed the much simpler to say IKE, Internet Key Exchange.