IPv6, IPSec, and other client connections (pptp, etc)

We're building what will be the largest VPN network in the world
(www.WorldWideVPN.com), and have some questions concerning IPv6.

Our basic structure is hub and spoke, with the hubs that permanently
inter-connect called the backbone, and those that connect temporarily
considered the "dial-up" users.

We would like to look into using IPv6 for the VPN network created by the
backbone servers. The backbone servers will inter-connect to each other via
IPSec, does IPSec have any conflict with IPv6?

Also, what do we have to do in consideration of clients that connect into
the network? Are there any client OSes that don't support IPv6, or are
there network PTP protocols that wouldn't support IPv6?

Thanks!

In article <hDMBb.15798$8y1.61839@attbi_s52>, Wed, 10 Dec 2003 14:55:25
-0700, "/dev/null" <dev.null@beginthread.com> wrote:

> We're building what will be the largest VPN network in the world
> (www.WorldWideVPN.com), and have some questions concerning IPv6.
>
> Our basic structure is hub and spoke, with the hubs that permanently
> inter-connect called the backbone, and those that connect temporarily
> considered the "dial-up" users.

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