Microsoft pptp vpn vulnerabilities Exploits in Action

IKE (Internet Key Exchange)
RFC 2409 
http://www.ietf.org/rfc/rfc2409.txt
describes IKE in detail. A 
(very) brief summary follows:
RFC 2409  [IKE] 
“…a hybrid protocol.” “…to negotiate,
and provide authenticated keying material for, security associations in a 
protected manner.”
In summary, IKE uses pieces of other technologies, those are:
ISAKMP for auth and key exchange
•
Oakley for different key exchange modes
•
SKEME for “anonymity, repudiability, and quick key refreshment”.
•
L2TP (Layer 2 Tunneling Protocol)
RFC 2661 
http://www.ietf.org/rfc/rfc2661.txt
describes L2TP in detail. A 
(very) brief summary follows:
RFC 2661 Abstract 
“…L2TP facilitates the tunneling of PPP packets 
across an intervening network in a way that is as transparent as possible to both 
end-users and applications.”
Two key components of L2TP are:
Control Messages – establish, maintain and clear tunnels and calls, also 
•
providing guaranteed delivery.
Data Messages – encapsulate PPP frames being carried over  the tunnel, 
•
data packets are NOT retransmitted when packet loss occurs.