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We performed spectro-temporal analysis in the 0.8--50 keV energy band of theneutron star Z source GX 17+2 using AstroSat Soft X-ray Telescope (SXT) andLarge Area X-ray Proportional Counter (LAXPC) data. The source was found tovary in the normal branch of the Hardness Intensity Diagram. Cross-correlationstudies of LAXPC light curves in soft and hard X-ray band unveiledanticorrelated lags of the order of few hundred seconds. For the first time,Cross-correlation studies were performed using SXT soft and LAXPC hardlightcurves and they exhibited correlated and anti-correlated lags of the orderof a hundred seconds. Power density spectrum displayed NB oscillations of6.7--7.8 Hz (quality factor 1.5--4.0). Spectral modeling resulted in inner diskradius of $\sim$ 12--16 km with $\Gamma$ $\sim$ 2.31--2.44 indicating that diskis close to the ISCO and a similar value of disk radius was noticed based onthe reflection model. Different methods were used to constrain the corona sizein GX 17+2. Using the detected lags, corona size was found to be 27-46 km($\beta$ = 0.1, $\beta$ = v$_{corona}$/v$_{disk}$) and 138--231 km ($\beta$ =0.5). Assuming the X-ray emission to be arising from the Boundary Layer (BL),its size was determined to be 57--71 km. Assuming that BL is ionizing thedisk's inner region, it's size was constrained to $\sim$ 19--86 km. Using NBOfrequency, the transition shell radius was found to be around 32 km. Observedlags and no movement of the inner disk front strongly indicates that thevarying corona structure is causing the X-ray variation in the NB of Z sourceGX 17+2.

Coronal Vertical Structure Variations in Normal Branch of GX 17+2 : AstroSa\v{t}s SXT and LAXPC perspective