diff --git a/lib/hooks/jitter_calc.c b/lib/hooks/jitter_calc.c
new file mode 100644
index 000000000..a2aeda9f6
--- /dev/null
+++ b/lib/hooks/jitter_calc.c
@@ -0,0 +1,84 @@
+/** Calc jitter, mean and variance of GPS vs NTP TS.
+ *
+ * @author Umar Farooq <umar.farooq@rwth-aachen.de>
+ * @copyright 2017, Institute for Automation of Complex Power Systems, EONERC
+ *********************************************************************************/
+
+/** @addtogroup hooks Hook functions
+ * @{
+ */
+
+#include "hook.h"
+#include "plugin.h"
+#include "timing.h"
+
+#define CALC_GPS_NTP_DELAY 0		/* @todo move to global config file */
+#define GPS_NTP_DELAY_WIN_SIZE 16
+
+static int64_t jitter_val[GPS_NTP_DELAY_WIN_SIZE] = {0};
+static int64_t delay_series[GPS_NTP_DELAY_WIN_SIZE] = {0};
+static int64_t moving_avg[GPS_NTP_DELAY_WIN_SIZE] = {0};
+static int64_t moving_var[GPS_NTP_DELAY_WIN_SIZE] = {0};
+static int64_t delay_mov_sum = 0, delay_mov_sum_sqrd = 0;
+static int curr_count = 0;
+
+/**
+ * Hook to calculate jitter between GTNET-SKT GPS timestamp and Villas node NTP timestamp.
+ *
+ * Drawbacks: No protection for out of order packets. Default positive delay assumed,
+ * so GPS timestamp should be earlier than NTP timestamp. If difference b/w NTP and GPS ts
+ * is high (i.e. several mins depending on GPS_NTP_DELAY_WIN_SIZE), 
+ * the variance value will overrun the 64bit value.
+ */
+int hook_jitter_ts(struct hook *h, struct sample *smps[], size_t *cnt)
+{
+	/* @todo save data for each node, not just displaying on the screen, doesn't work for more than one node!!! */
+	struct timespec now = time_now();
+	int64_t delay_sec, delay_nsec, curr_delay_us;
+
+	for(int i = 0; i < *cnt; i++) {
+		delay_sec = now.tv_sec - smps[i]->ts.origin.tv_sec;
+		delay_nsec = now.tv_nsec - smps[i]->ts.origin.tv_nsec;
+
+		/* Calc on microsec instead of nenosec delay as variance formula overflows otherwise.*/
+		curr_delay_us = delay_sec*1000000 + delay_nsec/1000;
+		
+		delay_mov_sum = delay_mov_sum + curr_delay_us - delay_series[curr_count];
+		moving_avg[curr_count] = delay_mov_sum/(GPS_NTP_DELAY_WIN_SIZE); /* Will be valid after GPS_NTP_DELAY_WIN_SIZE initial values */
+		
+		delay_mov_sum_sqrd = delay_mov_sum_sqrd + (curr_delay_us*curr_delay_us) - (delay_series[curr_count]*delay_series[curr_count]);
+		moving_var[curr_count] = (delay_mov_sum_sqrd - (delay_mov_sum*delay_mov_sum)/GPS_NTP_DELAY_WIN_SIZE)/(GPS_NTP_DELAY_WIN_SIZE-1);
+		
+		delay_series[curr_count] = curr_delay_us; /* Update the last delay value */
+
+		/* Jitter calc formula as used in Wireshark according to RFC3550 (RTP)
+			D(i,j) = (Rj-Ri)-(Sj-Si) = (Rj-Sj)-(Ri-Si)
+			J(i) = J(i-1)+(|D(i-1,i)|-J(i-1))/16
+		*/
+		jitter_val[(curr_count+1)%GPS_NTP_DELAY_WIN_SIZE] = jitter_val[curr_count] + (abs(curr_delay_us) - jitter_val[curr_count])/16;
+		
+		info("jitter %ld usec, moving average %ld usec, moving variance %ld usec\n", jitter_val[(curr_count+1)%GPS_NTP_DELAY_WIN_SIZE], moving_avg[curr_count], moving_var[curr_count]);
+		
+		curr_count++;
+		if(curr_count >= GPS_NTP_DELAY_WIN_SIZE)
+			curr_count = 0;
+	}
+	return 0;
+}
+
+#if CALC_GPS_NTP_DELAY == 1
+static struct plugin p = {
+	.name		= "jitter_calc",
+	.description	= "Calc jitter, mean and variance of GPS vs NTP TS",
+	.type		= PLUGIN_TYPE_HOOK,
+	.hook		= {
+		.priority = 0,
+		.builtin = true,
+		.read	= hook_jitter_ts,
+	}
+};
+
+REGISTER_PLUGIN(&p)
+#endif
+
+/** @} */