  We performed spectro-temporal analysis in the 0.8--50 keV energy band of the
neutron star Z source GX 17+2 using AstroSat Soft X-ray Telescope (SXT) and
Large Area X-ray Proportional Counter (LAXPC) data. The source was found to
vary in the normal branch of the Hardness Intensity Diagram. Cross-correlation
studies of LAXPC light curves in soft and hard X-ray band unveiled
anticorrelated lags of the order of few hundred seconds. For the first time,
Cross-correlation studies were performed using SXT soft and LAXPC hard
lightcurves and they exhibited correlated and anti-correlated lags of the order
of a hundred seconds. Power density spectrum displayed NB oscillations of
6.7--7.8 Hz (quality factor 1.5--4.0). Spectral modeling resulted in inner disk
radius of $\sim$ 12--16 km with $\Gamma$ $\sim$ 2.31--2.44 indicating that disk
is close to the ISCO and a similar value of disk radius was noticed based on
the reflection model. Different methods were used to constrain the corona size
in 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 the
disk's inner region, it's size was constrained to $\sim$ 19--86 km. Using NBO
frequency, the transition shell radius was found to be around 32 km. Observed
lags and no movement of the inner disk front strongly indicates that the
varying corona structure is causing the X-ray variation in the NB of Z source
GX 17+2.
