Auburn is playing Nebraska in the Cotton Bowl.
The Cotton Bowl is NOT a BCS contest.
It is a second tier bowl game.
The 5 BCS bowls are:
BCS Champioship
Orange
Rose
Fiesta
Sugar
The Cotton Bowl has applied for BCS affiliation, but this has not yet been worked out due to stadium requirements for the BCS and the availability of such facilities in the DFW area. This is basically the same reason Dallas does not ever host a Super Bowl - they want either a warm weather stadium or a dome, and they want a certain minimum capacity.