The top four will be the seeded teams in each World Cup group, with every pool then allocated one team from the second tier and one from the third.
In short, the top four sides avoid each other until the knockout stages of the World Cup to be held in England.
England, who have to face Australia, South Africa and then world champions New Zealand before the draw, are determined to be in the top four for their home World Cup.
If the draw were held now, England, Wales (6th), Argentina (7th) and Ireland (8th) would all be in the second tier of nations.
Ninth-placed Scotland would in the third tier with Samoa, Italy and Tonga.
The IRB rankings are calculated using a points exchange system in which sides take points off each other based on the match result.
Whatever a side gains, the other loses.
The exchanges are based on the match result, the relative strength of each team and the margin of victory, and there is an allowance for home advantage.
Under the system, the higher-rated side (especially allowing for home advantage) would pick up fewer points than a lower-ranked team if they won the match, and would give away more points if they lost.
It leaves Australia vulnerable against the in-form but lower-ranked English side.
Wallabies winger Digby Ioane said the players were intent purely on regaining winning form against England and putting the crushing French defeat behind them.
"For us, it's just a case of getting back to the office and seeing where we are at," Ioane said.
"We expect them to come at us pretty hard in defence and approach the game in the same way the French did and we just need to be ready for them."
- AAP