diff --git a/openbsc/include/openbsc/mgcp.h b/openbsc/include/openbsc/mgcp.h
index 8ab52ce..0d64590 100644
--- a/openbsc/include/openbsc/mgcp.h
+++ b/openbsc/include/openbsc/mgcp.h
@@ -114,6 +114,7 @@
 	char *audio_fmtp_extra;
 	char *audio_name;
 	int audio_payload;
+	int audio_send_ptime;
 	int audio_loop;
 
 	int omit_rtcp;
diff --git a/openbsc/include/openbsc/mgcp_internal.h b/openbsc/include/openbsc/mgcp_internal.h
index d59c5d7..20c433a 100644
--- a/openbsc/include/openbsc/mgcp_internal.h
+++ b/openbsc/include/openbsc/mgcp_internal.h
@@ -114,6 +114,12 @@
 	struct sockaddr_in forward;
 };
 
+struct mgcp_lco {
+	char *string;
+	int pkt_period_min; /* time in ms */
+	int pkt_period_max; /* time in ms */
+};
+
 enum mgcp_type {
 	MGCP_RTP_DEFAULT	= 0,
 	MGCP_RTP_TRANSCODED,
@@ -123,7 +129,7 @@
 	int allocated;
 	uint32_t ci;
 	char *callid;
-	char *local_options;
+	struct mgcp_lco local_options;
 	int conn_mode;
 	int orig_mode;
 
diff --git a/openbsc/src/libmgcp/mgcp_network.c b/openbsc/src/libmgcp/mgcp_network.c
index bf205d1..40227af 100644
--- a/openbsc/src/libmgcp/mgcp_network.c
+++ b/openbsc/src/libmgcp/mgcp_network.c
@@ -200,6 +200,58 @@
 	return 1;
 }
 
+/* Set the timestamp offset according to the packet duration. */
+static int adjust_rtp_timestamp_offset(struct mgcp_endpoint *endp,
+				       struct mgcp_rtp_state *state,
+				       struct mgcp_rtp_end *rtp_end,
+				       struct sockaddr_in *addr,
+				       int16_t delta_seq, uint32_t timestamp)
+{
+	int32_t tsdelta = state->packet_duration;
+	int timestamp_offset;
+
+	if (tsdelta == 0) {
+		tsdelta = state->out_stream.last_tsdelta;
+		if (tsdelta != 0) {
+			LOGP(DMGCP, LOGL_NOTICE,
+			     "A fixed packet duration is not available on 0x%x, "
+			     "using last output timestamp delta instead: %d "
+			     "from %s:%d in %d\n",
+			     ENDPOINT_NUMBER(endp), tsdelta,
+			     inet_ntoa(addr->sin_addr), ntohs(addr->sin_port),
+			     endp->conn_mode);
+		} else {
+			tsdelta = rtp_end->rate * 20 / 1000;
+			LOGP(DMGCP, LOGL_NOTICE,
+			     "Fixed packet duration and last timestamp delta "
+			     "are not available on 0x%x, "
+			     "using fixed 20ms instead: %d "
+			     "from %s:%d in %d\n",
+			     ENDPOINT_NUMBER(endp), tsdelta,
+			     inet_ntoa(addr->sin_addr), ntohs(addr->sin_port),
+			     endp->conn_mode);
+		}
+	}
+
+	timestamp_offset =
+		state->out_stream.last_timestamp - timestamp +
+		delta_seq * tsdelta;
+
+	if (state->timestamp_offset != timestamp_offset) {
+		state->timestamp_offset = timestamp_offset;
+
+		LOGP(DMGCP, LOGL_NOTICE,
+		     "Timestamp offset change on 0x%x SSRC: %u "
+		     "SeqNo delta: %d, TS offset: %d, "
+		     "from %s:%d in %d\n",
+		     ENDPOINT_NUMBER(endp), state->in_stream.ssrc,
+		     delta_seq, state->timestamp_offset,
+		     inet_ntoa(addr->sin_addr), ntohs(addr->sin_port),
+		     endp->conn_mode);
+	}
+
+	return timestamp_offset;
+}
 
 /**
  * The RFC 3550 Appendix A assumes there are multiple sources but
@@ -248,6 +300,15 @@
 			state->seq_offset, state->packet_duration,
 			inet_ntoa(addr->sin_addr), ntohs(addr->sin_port),
 			endp->conn_mode);
+		if (state->packet_duration == 0 && rtp_end->force_constant_timing)
+			LOGP(DMGCP, LOGL_ERROR,
+			"Cannot patch timestamps on 0x%x: "
+			"RTP packet duration is unknown, SSRC: %u, "
+			"from %s:%d in %d\n",
+			ENDPOINT_NUMBER(endp), state->in_stream.ssrc,
+			inet_ntoa(addr->sin_addr), ntohs(addr->sin_port),
+			endp->conn_mode);
+
 	} else if (state->in_stream.ssrc != ssrc) {
 		LOGP(DMGCP, LOGL_NOTICE,
 			"The SSRC changed on 0x%x: %u -> %u  "
@@ -259,22 +320,14 @@
 
 		state->in_stream.ssrc = ssrc;
 		if (rtp_end->force_constant_ssrc) {
-			int32_t tsdelta = state->out_stream.last_tsdelta;
-			if (tsdelta == 0) {
-				tsdelta = state->packet_duration;
-				LOGP(DMGCP, LOGL_NOTICE,
-				     "Timestamp delta is not available on 0x%x, "
-				     "using packet duration instead: %d "
-				     "from %s:%d in %d\n",
-				     ENDPOINT_NUMBER(endp), tsdelta,
-				     inet_ntoa(addr->sin_addr), ntohs(addr->sin_port),
-				     endp->conn_mode);
-			}
+			const int16_t delta_seq = 1;
+
 			state->seq_offset =
-				(state->out_stream.last_seq + 1) - seq;
-			state->timestamp_offset =
-				(state->out_stream.last_timestamp + tsdelta) -
-				timestamp;
+				(state->out_stream.last_seq + delta_seq) - seq;
+
+			adjust_rtp_timestamp_offset(endp, state, rtp_end, addr,
+						    delta_seq, timestamp);
+
 			state->patch_ssrc = 1;
 			ssrc = state->orig_ssrc;
 			if (rtp_end->force_constant_ssrc != -1)
@@ -282,10 +335,10 @@
 
 			LOGP(DMGCP, LOGL_NOTICE,
 			     "SSRC patching enabled on 0x%x SSRC: %u "
-			     "offset: %d tsdelta: %d "
+			     "SeqNo offset: %d, TS offset: %d "
 			     "from %s:%d in %d\n",
 			     ENDPOINT_NUMBER(endp), state->in_stream.ssrc,
-			     state->seq_offset, tsdelta,
+			     state->seq_offset, state->timestamp_offset,
 			     inet_ntoa(addr->sin_addr), ntohs(addr->sin_port),
 			     endp->conn_mode);
 		}
@@ -307,22 +360,12 @@
 
 	if (rtp_end->force_constant_timing &&
 	    state->out_stream.ssrc == ssrc && state->packet_duration) {
-		int delta_seq = seq + state->seq_offset - state->out_stream.last_seq;
-		int timestamp_offset =
-			state->out_stream.last_timestamp - timestamp +
-			delta_seq * state->packet_duration;
-		if (state->timestamp_offset != timestamp_offset) {
-			state->timestamp_offset = timestamp_offset;
+		/* Update the timestamp offset */
+		const int delta_seq =
+			seq + state->seq_offset - state->out_stream.last_seq;
 
-			LOGP(DMGCP, LOGL_NOTICE,
-			     "Timestamp patching enabled on 0x%x SSRC: %u "
-			     "SeqNo delta: %d, TS offset: %d, "
-			     "from %s:%d in %d\n",
-			     ENDPOINT_NUMBER(endp), state->in_stream.ssrc,
-			     delta_seq, state->timestamp_offset,
-			     inet_ntoa(addr->sin_addr), ntohs(addr->sin_port),
-			     endp->conn_mode);
-		}
+		adjust_rtp_timestamp_offset(endp, state, rtp_end, addr,
+					    delta_seq, timestamp);
 	}
 
 	/* Store the updated SSRC back to the packet */
diff --git a/openbsc/src/libmgcp/mgcp_protocol.c b/openbsc/src/libmgcp/mgcp_protocol.c
index ab94164..7d3ad74 100644
--- a/openbsc/src/libmgcp/mgcp_protocol.c
+++ b/openbsc/src/libmgcp/mgcp_protocol.c
@@ -230,11 +230,12 @@
 	const char *addr = endp->cfg->local_ip;
 	const char *fmtp_extra = endp->bts_end.fmtp_extra;
 	char sdp_record[4096];
+	int len;
 
 	if (!addr)
 		addr = endp->cfg->source_addr;
 
-	snprintf(sdp_record, sizeof(sdp_record) - 1,
+	len = snprintf(sdp_record, sizeof(sdp_record) - 1,
 			"I: %u\n\n"
 			"v=0\r\n"
 			"o=- %u 23 IN IP4 %s\r\n"
@@ -247,7 +248,25 @@
 			endp->net_end.local_port, endp->bts_end.payload_type,
 			endp->bts_end.payload_type, endp->tcfg->audio_name,
 			fmtp_extra ? fmtp_extra : "", fmtp_extra ? "\r\n" : "");
+
+	if (len < 0 || len >= sizeof(sdp_record))
+		goto buffer_too_small;
+
+	if (endp->bts_end.packet_duration_ms > 0 && endp->tcfg->audio_send_ptime) {
+		int nchars = snprintf(sdp_record + len, sizeof(sdp_record) - len,
+				      "a=ptime:%d\r\n",
+				      endp->bts_end.packet_duration_ms);
+		if (nchars < 0 || nchars >= sizeof(sdp_record) - len)
+			goto buffer_too_small;
+
+		len += nchars;
+	}
 	return create_resp(endp, 200, " OK", msg, trans_id, NULL, sdp_record);
+
+buffer_too_small:
+	LOGP(DMGCP, LOGL_ERROR, "SDP buffer too small: %d (needed %d)\n",
+	     sizeof(sdp_record), len);
+	return NULL;
 }
 
 /*
@@ -562,25 +581,64 @@
 {
 	char *line;
 	int found_media = 0;
+	int audio_payload = -1;
 
 	for_each_line(line, p->save) {
 		switch (line[0]) {
-		case 'a':
 		case 'o':
 		case 's':
 		case 't':
 		case 'v':
 			/* skip these SDP attributes */
 			break;
+		case 'a': {
+			int payload;
+			int rate;
+			int channels = 1;
+			int ptime, ptime2 = 0;
+			char audio_name[64];
+			char audio_codec[64];
+
+			if (audio_payload == -1)
+				break;
+
+			if (sscanf(line, "a=rtpmap:%d %64s",
+				   &payload, audio_name) == 2) {
+				if (payload != audio_payload)
+					break;
+
+				if (sscanf(audio_name, "%[^/]/%d/%d",
+					  audio_codec, &rate, &channels) < 2)
+					break;
+
+				rtp->rate = rate;
+				if (channels != 1)
+					LOGP(DMGCP, LOGL_NOTICE,
+					     "Channels != 1 in SDP: '%s' on 0x%x\n",
+					     line, ENDPOINT_NUMBER(p->endp));
+			} else if (sscanf(line, "a=ptime:%d-%d",
+					  &ptime, &ptime2) >= 1) {
+				if (ptime2 > 0 && ptime2 != ptime)
+					rtp->packet_duration_ms = 0;
+				else
+					rtp->packet_duration_ms = ptime;
+			} else if (sscanf(line, "a=maxptime:%d", &ptime2) == 1) {
+				if (ptime2 * rtp->frame_duration_den >
+				    rtp->frame_duration_num * 1500)
+					/* more than 1 frame */
+					rtp->packet_duration_ms = 0;
+			}
+			break;
+		}
 		case 'm': {
 			int port;
-			int payload;
+			audio_payload = -1;
 
 			if (sscanf(line, "m=audio %d RTP/AVP %d",
-				   &port, &payload) == 2) {
+				   &port, &audio_payload) == 2) {
 				rtp->rtp_port = htons(port);
 				rtp->rtcp_port = htons(port + 1);
-				rtp->payload_type = payload;
+				rtp->payload_type = audio_payload;
 				found_media = 1;
 			}
 			break;
@@ -608,12 +666,33 @@
 
 	if (found_media)
 		LOGP(DMGCP, LOGL_NOTICE,
-		     "Got media info via SDP: port %d, payload %d, addr %s\n",
-		     ntohs(rtp->rtp_port), rtp->payload_type, inet_ntoa(rtp->addr));
+		     "Got media info via SDP: port %d, payload %d, "
+		     "duration %d, addr %s\n",
+		     ntohs(rtp->rtp_port), rtp->payload_type,
+		     rtp->packet_duration_ms, inet_ntoa(rtp->addr));
 
 	return found_media;
 }
 
+/* Set the LCO from a string (see RFC 3435).
+ * The string is stored in the 'string' field. A NULL string is handled excatly
+ * like an empty string, the 'string' field is never NULL after this function
+ * has been called. */
+static void set_local_cx_options(void *ctx, struct mgcp_lco *lco,
+				 const char *options)
+{
+	char *p_opt;
+
+	talloc_free(lco->string);
+	lco->pkt_period_min = lco->pkt_period_max = 0;
+	lco->string = talloc_strdup(ctx, options ? options : "");
+
+	p_opt = strstr(lco->string, "p:");
+	if (p_opt && sscanf(p_opt, "p:%d-%d",
+			    &lco->pkt_period_min, &lco->pkt_period_max) == 1)
+		lco->pkt_period_max = lco->pkt_period_min;
+}
+
 void mgcp_rtp_end_config(struct mgcp_endpoint *endp, int expect_ssrc_change,
 			 struct mgcp_rtp_end *rtp)
 {
@@ -712,8 +791,8 @@
 	/* copy some parameters */
 	endp->callid = talloc_strdup(tcfg->endpoints, callid);
 
-	if (local_options)
-		endp->local_options = talloc_strdup(tcfg->endpoints, local_options);
+	set_local_cx_options(endp->tcfg->endpoints, &endp->local_options,
+			     local_options);
 
 	if (parse_conn_mode(mode, &endp->conn_mode) != 0) {
 		    error_code = 517;
@@ -789,6 +868,7 @@
 	int error_code = 500;
 	int silent = 0;
 	char *line;
+	const char *local_options = NULL;
 
 	if (p->found != 0)
 		return create_err_response(NULL, 510, "MDCX", p->trans);
@@ -812,7 +892,7 @@
 			break;
 		}
 		case 'L':
-			/* skip */
+			local_options = (const char *) line + 3;
 			break;
 		case 'M':
 			if (parse_conn_mode(line + 3, &endp->conn_mode) != 0) {
@@ -838,6 +918,9 @@
 		}
 	}
 
+	set_local_cx_options(endp->tcfg->endpoints, &endp->local_options,
+			     local_options);
+
 	/* policy CB */
 	if (p->cfg->policy_cb) {
 		int rc;
@@ -1045,6 +1128,7 @@
 	cfg->trunk.trunk_type = MGCP_TRUNK_VIRTUAL;
 	cfg->trunk.audio_name = talloc_strdup(cfg, "AMR/8000");
 	cfg->trunk.audio_payload = 126;
+	cfg->trunk.audio_send_ptime = 1;
 	cfg->trunk.omit_rtcp = 0;
 
 	INIT_LLIST_HEAD(&cfg->trunks);
@@ -1067,6 +1151,7 @@
 	trunk->trunk_nr = nr;
 	trunk->audio_name = talloc_strdup(cfg, "AMR/8000");
 	trunk->audio_payload = 126;
+	trunk->audio_send_ptime = 1;
 	trunk->number_endpoints = 33;
 	trunk->omit_rtcp = 0;
 	llist_add_tail(&trunk->entry, &cfg->trunks);
@@ -1148,8 +1233,8 @@
 	talloc_free(endp->callid);
 	endp->callid = NULL;
 
-	talloc_free(endp->local_options);
-	endp->local_options = NULL;
+	talloc_free(endp->local_options.string);
+	endp->local_options.string = NULL;
 
 	mgcp_rtp_end_reset(&endp->bts_end);
 	mgcp_rtp_end_reset(&endp->net_end);
diff --git a/openbsc/src/libmgcp/mgcp_vty.c b/openbsc/src/libmgcp/mgcp_vty.c
index e48b050..235b8bd 100644
--- a/openbsc/src/libmgcp/mgcp_vty.c
+++ b/openbsc/src/libmgcp/mgcp_vty.c
@@ -105,6 +105,8 @@
 	if (g_cfg->trunk.audio_fmtp_extra)
 		vty_out(vty, "  sdp audio fmtp-extra %s%s",
 			g_cfg->trunk.audio_fmtp_extra, VTY_NEWLINE);
+	vty_out(vty, "  %ssdp audio-payload send-ptime%s",
+		g_cfg->trunk.audio_send_ptime ? "" : "no ", VTY_NEWLINE);
 	vty_out(vty, "  loop %u%s", !!g_cfg->trunk.audio_loop, VTY_NEWLINE);
 	vty_out(vty, "  number endpoints %u%s", g_cfg->trunk.number_endpoints - 1, VTY_NEWLINE);
 	if (g_cfg->call_agent_addr)
@@ -391,6 +393,26 @@
       "sdp audio payload name NAME",
       SDP_STR AUDIO_STR AUDIO_STR "Name\n" "Payload name\n")
 
+DEFUN(cfg_mgcp_sdp_payload_send_ptime,
+      cfg_mgcp_sdp_payload_send_ptime_cmd,
+      "sdp audio-payload send-ptime",
+      SDP_STR AUDIO_STR
+      "Send SDP ptime (packet duration) attribute\n")
+{
+	g_cfg->trunk.audio_send_ptime = 1;
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_mgcp_no_sdp_payload_send_ptime,
+      cfg_mgcp_no_sdp_payload_send_ptime_cmd,
+      "no sdp audio-payload send-ptime",
+      NO_STR SDP_STR AUDIO_STR
+      "Send SDP ptime (packet duration) attribute\n")
+{
+	g_cfg->trunk.audio_send_ptime = 0;
+	return CMD_SUCCESS;
+}
+
 DEFUN(cfg_mgcp_loop,
       cfg_mgcp_loop_cmd,
       "loop (0|1)",
@@ -568,6 +590,8 @@
 			trunk->audio_payload, VTY_NEWLINE);
 		vty_out(vty, "  sdp audio-payload name %s%s",
 			trunk->audio_name, VTY_NEWLINE);
+		vty_out(vty, "  %ssdp audio-payload send-ptime%s",
+			trunk->audio_send_ptime ? "" : "no ", VTY_NEWLINE);
 		vty_out(vty, "  loop %d%s",
 			trunk->audio_loop, VTY_NEWLINE);
 		if (trunk->omit_rtcp)
@@ -649,6 +673,28 @@
 	return CMD_SUCCESS;
 }
 
+DEFUN(cfg_trunk_sdp_payload_send_ptime,
+      cfg_trunk_sdp_payload_send_ptime_cmd,
+      "sdp audio-payload send-ptime",
+      SDP_STR AUDIO_STR
+      "Send SDP ptime (packet duration) attribute\n")
+{
+	struct mgcp_trunk_config *trunk = vty->index;
+	trunk->audio_send_ptime = 1;
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_trunk_no_sdp_payload_send_ptime,
+      cfg_trunk_no_sdp_payload_send_ptime_cmd,
+      "no sdp audio-payload send-ptime",
+      NO_STR SDP_STR AUDIO_STR
+      "Send SDP ptime (packet duration) attribute\n")
+{
+	struct mgcp_trunk_config *trunk = vty->index;
+	trunk->audio_send_ptime = 0;
+	return CMD_SUCCESS;
+}
+
 DEFUN(cfg_trunk_omit_rtcp,
       cfg_trunk_omit_rtcp_cmd,
       "rtcp-omit",
@@ -966,6 +1012,8 @@
 	install_element(MGCP_NODE, &cfg_mgcp_no_patch_rtp_ts_cmd);
 	install_element(MGCP_NODE, &cfg_mgcp_no_patch_rtp_cmd);
 	install_element(MGCP_NODE, &cfg_mgcp_sdp_fmtp_extra_cmd);
+	install_element(MGCP_NODE, &cfg_mgcp_sdp_payload_send_ptime_cmd);
+	install_element(MGCP_NODE, &cfg_mgcp_no_sdp_payload_send_ptime_cmd);
 
 	install_element(MGCP_NODE, &cfg_mgcp_trunk_cmd);
 	install_node(&trunk_node, config_write_trunk);
@@ -983,6 +1031,8 @@
 	install_element(TRUNK_NODE, &cfg_trunk_no_patch_rtp_ts_cmd);
 	install_element(TRUNK_NODE, &cfg_trunk_no_patch_rtp_cmd);
 	install_element(TRUNK_NODE, &cfg_trunk_sdp_fmtp_extra_cmd);
+	install_element(TRUNK_NODE, &cfg_trunk_sdp_payload_send_ptime_cmd);
+	install_element(TRUNK_NODE, &cfg_trunk_no_sdp_payload_send_ptime_cmd);
 
 	return 0;
 }
diff --git a/openbsc/tests/mgcp/mgcp_test.c b/openbsc/tests/mgcp/mgcp_test.c
index 7c02d09..9777a4d 100644
--- a/openbsc/tests/mgcp/mgcp_test.c
+++ b/openbsc/tests/mgcp/mgcp_test.c
@@ -81,7 +81,8 @@
 		 "c=IN IP4 0.0.0.0\r\n"		\
 		 "t=0 0\r\n"			\
 		 "m=audio 0 RTP/AVP 126\r\n"	\
-		 "a=rtpmap:126 AMR/8000\r\n"
+		 "a=rtpmap:126 AMR/8000\r\n"	\
+		 "a=ptime:20\r\n"
 #define MDCX4 "MDCX 18983216 1@mgw MGCP 1.0\r\n" \
 		 "C: 2\r\n"          \
 		 "I: 1\r\n"                    \
@@ -92,8 +93,9 @@
 		 "c=IN IP4 0.0.0.0\r\n"		\
 		 "t=0 0\r\n"			\
 		 "m=audio 4441 RTP/AVP 99\r\n"	\
-		 "a=rtpmap:99 AMR/8000\r\n"
-#define MDCX4_RET "200 18983216 OK\r\n"		\
+		 "a=rtpmap:99 AMR/8000\r\n"	\
+		 "a=ptime:40\r\n"
+#define MDCX4_RET(Ident) "200 " Ident " OK\r\n"	\
 		 "I: 1\n"			\
 		 "\n"				\
 		 "v=0\r\n"			\
@@ -101,7 +103,47 @@
 		 "c=IN IP4 0.0.0.0\r\n"		\
 		 "t=0 0\r\n"			\
 		 "m=audio 0 RTP/AVP 126\r\n"	\
-		 "a=rtpmap:126 AMR/8000\r\n"
+		 "a=rtpmap:126 AMR/8000\r\n"	\
+		 "a=ptime:20\r\n"
+
+#define MDCX4_PT1 "MDCX 18983217 1@mgw MGCP 1.0\r\n" \
+		 "C: 2\r\n"          \
+		 "I: 1\r\n"                    \
+		 "L: p:20-40, a:AMR, nt:IN\r\n"    \
+		 "\n"				\
+		 "v=0\r\n"			\
+		 "o=- 1 23 IN IP4 0.0.0.0\r\n"	\
+		 "c=IN IP4 0.0.0.0\r\n"		\
+		 "t=0 0\r\n"			\
+		 "m=audio 4441 RTP/AVP 99\r\n"	\
+		 "a=rtpmap:99 AMR/8000\r\n"	\
+		 "a=ptime:40\r\n"
+
+#define MDCX4_PT2 "MDCX 18983218 1@mgw MGCP 1.0\r\n" \
+		 "C: 2\r\n"          \
+		 "I: 1\r\n"                    \
+		 "L: p:20-20, a:AMR, nt:IN\r\n"    \
+		 "\n"				\
+		 "v=0\r\n"			\
+		 "o=- 1 23 IN IP4 0.0.0.0\r\n"	\
+		 "c=IN IP4 0.0.0.0\r\n"		\
+		 "t=0 0\r\n"			\
+		 "m=audio 4441 RTP/AVP 99\r\n"	\
+		 "a=rtpmap:99 AMR/8000\r\n"	\
+		 "a=ptime:40\r\n"
+
+#define MDCX4_PT3 "MDCX 18983219 1@mgw MGCP 1.0\r\n" \
+		 "C: 2\r\n"          \
+		 "I: 1\r\n"                    \
+		 "L: a:AMR, nt:IN\r\n"    \
+		 "\n"				\
+		 "v=0\r\n"			\
+		 "o=- 1 23 IN IP4 0.0.0.0\r\n"	\
+		 "c=IN IP4 0.0.0.0\r\n"		\
+		 "t=0 0\r\n"			\
+		 "m=audio 4441 RTP/AVP 99\r\n"	\
+		 "a=rtpmap:99 AMR/8000\r\n"	\
+		 "a=ptime:40\r\n"
 
 #define SHORT2	"CRCX 1"
 #define SHORT2_RET "510 000000 FAIL\r\n"
@@ -112,11 +154,13 @@
 #define CRCX	 "CRCX 2 1@mgw MGCP 1.0\r\n"	\
 		 "M: sendrecv\r\n"		\
 		 "C: 2\r\n"			\
+		 "L: p:20\r\n"		\
 		 "\r\n"				\
 		 "v=0\r\n"			\
 		 "c=IN IP4 123.12.12.123\r\n"	\
 		 "m=audio 5904 RTP/AVP 97\r\n"	\
-		 "a=rtpmap:97 GSM-EFR/8000\r\n"
+		 "a=rtpmap:97 GSM-EFR/8000\r\n"	\
+		 "a=ptime:40\r\n"
 
 #define CRCX_RET "200 2 OK\r\n"			\
 		 "I: 1\n"			\
@@ -126,8 +170,8 @@
 		 "c=IN IP4 0.0.0.0\r\n"		\
 		 "t=0 0\r\n"			\
 		 "m=audio 0 RTP/AVP 126\r\n"	\
-		 "a=rtpmap:126 AMR/8000\r\n"
-
+		 "a=rtpmap:126 AMR/8000\r\n"	\
+		 "a=ptime:20\r\n"
 
 #define CRCX_ZYN "CRCX 2 1@mgw MGCP 1.0\r"	\
 		 "M: sendrecv\r"		\
@@ -145,7 +189,8 @@
 		 "c=IN IP4 0.0.0.0\r\n"		\
 		 "t=0 0\r\n"			\
 		 "m=audio 0 RTP/AVP 126\r\n"	\
-		 "a=rtpmap:126 AMR/8000\r\n"
+		 "a=rtpmap:126 AMR/8000\r\n"	\
+		 "a=ptime:20\r\n"
 
 #define DLCX	 "DLCX 7 1@mgw MGCP 1.0\r\n"	\
 		 "C: 2\r\n"
@@ -184,7 +229,10 @@
 	{ "MDCX2", MDCX_UNALLOCATED, MDCX_RET },
 	{ "CRCX", CRCX, CRCX_RET, 97, 126 },
 	{ "MDCX3", MDCX3, MDCX3_RET, PTYPE_NONE, 126 },
-	{ "MDCX4", MDCX4, MDCX4_RET, 99, 126 },
+	{ "MDCX4", MDCX4, MDCX4_RET("18983216"), 99, 126 },
+	{ "MDCX4_PT1", MDCX4_PT1, MDCX4_RET("18983217"), 99, 126 },
+	{ "MDCX4_PT2", MDCX4_PT2, MDCX4_RET("18983218"), 99, 126 },
+	{ "MDCX4_PT3", MDCX4_PT3, MDCX4_RET("18983219"), 99, 126 },
 	{ "DLCX", DLCX, DLCX_RET, -1, -1 },
 	{ "CRCX_ZYN", CRCX_ZYN, CRCX_ZYN_RET, 97, 126 },
 	{ "EMPTY", EMPTY, EMPTY_RET },
@@ -245,6 +293,7 @@
 	for (i = 0; i < cfg->trunk.number_endpoints; i++) {
 		endp = &cfg->trunk.endpoints[i];
 		endp->net_end.payload_type = PTYPE_NONE;
+		endp->net_end.packet_duration_ms = -1;
 	}
 
 	for (i = 0; i < ARRAY_SIZE(tests); i++) {
@@ -266,6 +315,27 @@
 			printf("%s failed '%s'\n", t->name, (char *) msg->data);
 		msgb_free(msg);
 
+		if (last_endpoint != -1) {
+			endp = &cfg->trunk.endpoints[last_endpoint];
+
+			if (endp->net_end.packet_duration_ms != -1)
+				printf("Detected packet duration: %d\n",
+				       endp->net_end.packet_duration_ms);
+			else
+				printf("Packet duration not set\n");
+			if (endp->local_options.pkt_period_min ||
+			    endp->local_options.pkt_period_max)
+				printf("Requested packetetization period: "
+				       "%d-%d\n",
+				       endp->local_options.pkt_period_min,
+				       endp->local_options.pkt_period_max);
+			else
+				printf("Requested packetization period not set\n");
+
+			endp->net_end.packet_duration_ms = -1;
+		}
+
+
 		/* Check detected payload type */
 		if (t->exp_net_ptype != PTYPE_IGNORE ||
 		    t->exp_bts_ptype != PTYPE_IGNORE) {
@@ -305,6 +375,13 @@
 
 	mgcp_endpoints_allocate(mgcp_trunk_alloc(cfg, 1));
 
+	/* reset endpoints */
+	for (i = 0; i < cfg->trunk.number_endpoints; i++) {
+		struct mgcp_endpoint *endp;
+		endp = &cfg->trunk.endpoints[i];
+		endp->bts_end.packet_duration_ms = 20;
+	}
+
 	for (i = 0; i < ARRAY_SIZE(retransmit); i++) {
 		const struct mgcp_test *t = &retransmit[i];
 		struct msgb *inp;
diff --git a/openbsc/tests/mgcp/mgcp_test.ok b/openbsc/tests/mgcp/mgcp_test.ok
index 3beeb59..f9dd7cb 100644
--- a/openbsc/tests/mgcp/mgcp_test.ok
+++ b/openbsc/tests/mgcp/mgcp_test.ok
@@ -16,10 +16,29 @@
 Testing MDCX1
 Testing MDCX2
 Testing CRCX
+Detected packet duration: 40
+Requested packetetization period: 20-20
 Testing MDCX3
+Packet duration not set
+Requested packetization period not set
 Testing MDCX4
+Detected packet duration: 40
+Requested packetetization period: 20-20
+Testing MDCX4_PT1
+Detected packet duration: 40
+Requested packetetization period: 20-40
+Testing MDCX4_PT2
+Detected packet duration: 40
+Requested packetetization period: 20-20
+Testing MDCX4_PT3
+Detected packet duration: 40
+Requested packetization period not set
 Testing DLCX
+Detected packet duration: 20
+Requested packetization period not set
 Testing CRCX_ZYN
+Packet duration not set
+Requested packetization period not set
 Testing EMPTY
 Testing SHORT1
 Testing SHORT2
@@ -28,6 +47,8 @@
 Testing RQNT1
 Testing RQNT2
 Testing DLCX
+Detected packet duration: 20
+Requested packetization period not set
 Testing CRCX
 Re-transmitting CRCX
 Testing RQNT1