Question about ppvpn-rfc2547bis-01 January 2002

Hey Group:

I would appreciate if I can get answer to the following.

In Draft 2547bis, ppvpn-rfc2547bis-01 January 2002. Pg 12, Section# 4.2, 
three different kinds of Route Distinguisher encoding schemes are described.
Does anybody know which scheme is most widely used?

Thanks for your response.
Sachin Kalra