diff --git a/clock.c b/clock.c
index 0dc9b437..75853520 100644
--- a/clock.c
+++ b/clock.c
@@ -67,6 +67,8 @@ struct clock {
 	int fault_fd[CLK_N_PORTS];
 	time_t fault_timeout;
 	int nports; /* does not include the UDS port */
+	int free_running;
+	int freq_est_interval;
 	int utc_timescale;
 	tmv_t master_offset;
 	tmv_t path_delay;
@@ -398,7 +400,7 @@ UInteger8 clock_class(struct clock *c)
 }
 
 struct clock *clock_create(int phc_index, struct interface *iface, int count,
-			   enum timestamp_type timestamping, struct defaultDS *ds,
+			   enum timestamp_type timestamping, struct default_ds *dds,
 			   enum servo_type servo)
 {
 	int i, fadj = 0, max_adj = 0.0, sw_ts = timestamping == TS_SOFTWARE ? 1 : 0;
@@ -415,7 +417,10 @@ struct clock *clock_create(int phc_index, struct interface *iface, int count,
 	if (c->nports)
 		clock_destroy(c);
 
-	if (c->dds.free_running) {
+	c->free_running = dds->free_running;
+	c->freq_est_interval = dds->freq_est_interval;
+
+	if (c->free_running) {
 		c->clkid = CLOCK_INVALID;
 	} else if (phc_index >= 0) {
 		snprintf(phc, 31, "/dev/ptp%d", phc_index);
@@ -449,7 +454,7 @@ struct clock *clock_create(int phc_index, struct interface *iface, int count,
 		return NULL;
 	}
 
-	c->dds = *ds;
+	c->dds = dds->dds;
 
 	/* Initialize the parentDS. */
 	clock_update_grandmaster(c);
@@ -788,7 +793,7 @@ void clock_remove_fda(struct clock *c, struct port *p, struct fdarray fda)
 
 int clock_slave_only(struct clock *c)
 {
-	return c->dds.slaveOnly;
+	return c->dds.flags & DDS_SLAVE_ONLY;
 }
 
 UInteger16 clock_steps_removed(struct clock *c)
@@ -828,7 +833,7 @@ enum servo_state clock_synchronize(struct clock *c,
 	if (!c->path_delay)
 		return state;
 
-	if (c->dds.free_running)
+	if (c->free_running)
 		return clock_no_adjust(c);
 
 	adj = servo_sample(c->servo, c->master_offset, ingress, &state);
@@ -853,7 +858,7 @@ enum servo_state clock_synchronize(struct clock *c,
 
 void clock_sync_interval(struct clock *c, int n)
 {
-	int shift = c->dds.freq_est_interval - n;
+	int shift = c->freq_est_interval - n;
 
 	if (shift < 0)
 		shift = 0;
diff --git a/clock.h b/clock.h
index ca2071d1..eb295b70 100644
--- a/clock.h
+++ b/clock.h
@@ -65,12 +65,12 @@ UInteger8 clock_class(struct clock *c);
  * @param interface    An array of network interfaces.
  * @param count        The number of elements in @a interfaces.
  * @param timestamping The timestamping mode for this clock.
- * @param ds           A pointer to a default data set for the clock.
+ * @param dds          A pointer to a default data set for the clock.
  * @param servo        The servo that this clock will use.
  * @return             A pointer to the single global clock instance.
  */
 struct clock *clock_create(int phc_index, struct interface *iface, int count,
-			   enum timestamp_type timestamping, struct defaultDS *ds,
+			   enum timestamp_type timestamping, struct default_ds *dds,
 			   enum servo_type servo);
 
 /**
diff --git a/config.c b/config.c
index 1fc5da4d..23154433 100644
--- a/config.c
+++ b/config.c
@@ -153,7 +153,7 @@ static enum parser_result parse_global_setting(const char *option,
 	UInteger8 u8;
 	unsigned char mac[MAC_LEN];
 
-	struct defaultDS *dds = &cfg->dds;
+	struct defaultDS *dds = &cfg->dds.dds;
 	struct port_defaults *pod = &cfg->pod;
 
 	enum parser_result r;
@@ -165,13 +165,20 @@ static enum parser_result parse_global_setting(const char *option,
 	if (!strcmp(option, "twoStepFlag")) {
 		if (1 != sscanf(value, "%d", &val))
 			return BAD_VALUE;
-		dds->twoStepFlag = val ? 1 : 0;
+		if (val)
+			dds->flags |=  DDS_TWO_STEP_FLAG;
+		else
+			dds->flags &= ~DDS_TWO_STEP_FLAG;
 
 	} else if (!strcmp(option, "slaveOnly")) {
 		if (1 != sscanf(value, "%d", &val))
 			return BAD_VALUE;
-		if (!(cfg_ignore & CFG_IGNORE_SLAVEONLY))
-			dds->slaveOnly = val ? 1 : 0;
+		if (!(cfg_ignore & CFG_IGNORE_SLAVEONLY)) {
+			if (val)
+				dds->flags |=  DDS_SLAVE_ONLY;
+			else
+				dds->flags &= ~DDS_SLAVE_ONLY;
+		}
 
 	} else if (!strcmp(option, "priority1")) {
 		if (1 != sscanf(value, "%hhu", &u8))
@@ -207,12 +214,12 @@ static enum parser_result parse_global_setting(const char *option,
 	} else if (!strcmp(option, "free_running")) {
 		if (1 != sscanf(value, "%d", &val))
 			return BAD_VALUE;
-		dds->free_running = val ? 1 : 0;
+		cfg->dds.free_running = val ? 1 : 0;
 
 	} else if (!strcmp(option, "freq_est_interval")) {
 		if (1 != sscanf(value, "%d", &val) || !(val >= 0))
 			return BAD_VALUE;
-		dds->freq_est_interval = val;
+		cfg->dds.freq_est_interval = val;
 		pod->freq_est_interval = val;
 
 	} else if (!strcmp(option, "assume_two_step")) {
diff --git a/config.h b/config.h
index 5ceba9dd..497d6839 100644
--- a/config.h
+++ b/config.h
@@ -58,7 +58,7 @@ struct config {
 	enum transport_type transport;
 	enum delay_mechanism dm;
 
-	struct defaultDS dds;
+	struct default_ds dds;
 	struct port_defaults pod;
 	int *assume_two_step;
 	int *tx_timestamp_retries;
diff --git a/ds.h b/ds.h
index 630986f0..64f4317a 100644
--- a/ds.h
+++ b/ds.h
@@ -24,17 +24,25 @@
 
 /* clock data sets */
 
+#define DDS_TWO_STEP_FLAG (1<<0)
+#define DDS_SLAVE_ONLY    (1<<1)
+
 struct defaultDS {
-	Boolean              twoStepFlag;
-	Boolean              slaveOnly;
+	UInteger8            flags;
+	UInteger8            reserved1;
 	UInteger16           numberPorts;
 	UInteger8            priority1;
 	struct ClockQuality  clockQuality;
 	UInteger8            priority2;
 	struct ClockIdentity clockIdentity;
 	UInteger8            domainNumber;
-	int                  free_running;
-	int                  freq_est_interval; /*log seconds*/
+	UInteger8            reserved2;
+} PACKED;
+
+struct default_ds {
+	struct defaultDS dds;
+	int free_running;
+	int freq_est_interval; /*log seconds*/
 };
 
 struct dataset {
diff --git a/ptp4l.c b/ptp4l.c
index 0132d381..5e015217 100644
--- a/ptp4l.c
+++ b/ptp4l.c
@@ -40,14 +40,15 @@ static int running = 1;
 
 static struct config cfg_settings = {
 	.dds = {
-		.twoStepFlag = TRUE,
-		.slaveOnly = FALSE,
-		.priority1 = 128,
-		.clockQuality.clockClass = 248,
-		.clockQuality.clockAccuracy = 0xfe,
-		.clockQuality.offsetScaledLogVariance = 0xffff,
-		.priority2 = 128,
-		.domainNumber = 0,
+		.dds = {
+			.flags = DDS_TWO_STEP_FLAG,
+			.priority1 = 128,
+			.clockQuality.clockClass = 248,
+			.clockQuality.clockAccuracy = 0xfe,
+			.clockQuality.offsetScaledLogVariance = 0xffff,
+			.priority2 = 128,
+			.domainNumber = 0,
+		},
 		.free_running = 0,
 		.freq_est_interval = 1,
 	},
@@ -137,7 +138,7 @@ int main(int argc, char *argv[])
 	enum transport_type *transport = &cfg_settings.transport;
 	enum timestamp_type *timestamping = &cfg_settings.timestamping;
 	struct clock *clock;
-	struct defaultDS *ds = &cfg_settings.dds;
+	struct defaultDS *ds = &cfg_settings.dds.dds;
 	int phc_index = -1, required_modes = 0;
 
 	if (SIG_ERR == signal(SIGINT, handle_int_quit_term)) {
@@ -205,7 +206,7 @@ int main(int argc, char *argv[])
 			req_phc = optarg;
 			break;
 		case 's':
-			ds->slaveOnly = TRUE;
+			ds->flags |= DDS_SLAVE_ONLY;
 			*cfg_ignore |= CFG_IGNORE_SLAVEONLY;
 			break;
 		case 'l':
@@ -235,7 +236,7 @@ int main(int argc, char *argv[])
 	if (config && (c = config_read(config, &cfg_settings))) {
 		return c;
 	}
-	if (ds->slaveOnly) {
+	if (ds->flags & DDS_SLAVE_ONLY) {
 		ds->clockQuality.clockClass = 255;
 	}
 
@@ -256,7 +257,7 @@ int main(int argc, char *argv[])
 		return -1;
 	}
 
-	if (!ds->twoStepFlag) {
+	if (!(ds->flags & DDS_TWO_STEP_FLAG)) {
 		switch (*timestamping) {
 		case TS_SOFTWARE:
 		case TS_LEGACY_HW:
@@ -302,7 +303,7 @@ int main(int argc, char *argv[])
 	}
 
 	/* determine PHC Clock index */
-	if (ds->free_running) {
+	if (cfg_settings.dds.free_running) {
 		phc_index = -1;
 	} else if (*timestamping == TS_SOFTWARE || *timestamping == TS_LEGACY_HW) {
 		phc_index = -1;
@@ -330,7 +331,8 @@ int main(int argc, char *argv[])
 	}
 
 	clock = clock_create(phc_index, iface, cfg_settings.nports,
-			     *timestamping, ds, cfg_settings.clock_servo);
+			     *timestamping, &cfg_settings.dds,
+			     cfg_settings.clock_servo);
 	if (!clock) {
 		fprintf(stderr, "failed to create a clock\n");
 		return -1;