The BSE benchmark index Sensex which gained 172 points in early trade today was trading 101 points up at 17,402 a short while ago. In a similar fashion, the wide-based National Stock Exchange index Nifty which moved up by 44 points in the opening session was trading 17 points up at 5252, a short while ago.The rise in Sensex is on the back of buying by funds and retail investors. It is also driven by encouraging quarterly earnings by corporates and firming trend on the other Asian bourses.