From a hadith:
Allah's Apostle used to offer eleven Rakat and that was his prayer. He used to prolong the prostration to such an extent that one could recite fifty verses (of the Quran) before he would lift his head. He used to pray two Rakat (Sunna) before the Fajr prayer and then used to lie down on his right side till the call-maker came and informed him about the prayer. (Bukhari, Book 21, 223)
I've always thought that the sunna prayer before Fajr was before the period when one could pray Fajr (i.e. before the adhan). But from the wording of the hadith it sounds like one would pray this sunna prayer in the late night and then wait for Fajr adhan.
Could someone clarify?