When to play f6 in french opening ??

[Event "Challenge"]
[Site "http://www.redhotpawn.com"]
[Date "2008.08.29"]
[EndDate "2008.08.31"]
[Round "?"]
[White "tomtom232"]
[Black "robbie carrobie"]
[WhiteRating "1428"]
[BlackRating "1500"]
[WhiteELO "1428"]
[BlackELO "1500"]
[Result "1-0"]
[GameId "5373111"]
1. e4 e6 2. d4 d5 3. exd5 exd5 4. c4 Bf8b4 5. Bc1d2 Qd8e7 6. Bf1e2 dxc4
7. Ng1f3 Bb4xd2 8. Nb1xd2 b5 9. O-O Ng8f6 10. Rf1e1 Bc8e6 11. a4 c6
12. axb5 cxb5 13. Nf3g5 O-O 14. Be2f3 Nb8d7 15. d5 Nf6xd5 16. Ng5xe6 Qe7xe6
17. Re1xe6 fxe6 18. Bf3xd5 exd5 19. Nd2xc4 bxc4 20. Qd1xd5 Rf8f7 21. Qd5xa8 1-0