Juniper ADVPN and Cisco DVPN are used generally by large enterprises with a number of remote sites connecting using IPSEC VPN over the internet to a VPN conncentrator at the central site.
These technologies provide a simplicfication of deploy configuration for the large remote site and a measure of automation on the connection and routing that needs to occur for the enterprise WAN.
This free book: Day One: ADVPN Design & Implementation may be of interest.
http://forums.juniper.net/t5/Day-One-Books/Day-One-ADVPN-Design-And-Implementation/ba-p/281108