diff --git a/NEWS b/NEWS
index ac75844f31..ca564c43cd 100644
--- a/NEWS
+++ b/NEWS
@@ -167,6 +167,19 @@ New Functionality
 
 - Add parsing, analysis, and logging support for MQTT protocol v3.1/v3.1.1.
 
+- Zeek now supports duration thresholding on connections, similarly to how it supports
+  byte and packet thresholds.
+
+  - New events:
+    - ConnThreshold::duration_threshold_crossed
+    - conn_duration_threshold_crossed
+
+  - New functions:
+    - ConnThreshold::set_duration_threshold
+    - ConnThreshold::delete_duration_threshold
+    - set_current_conn_duration_threshold
+    - get_current_conn_duration_threshold
+
 Changed Functionality
 ---------------------
 
diff --git a/doc b/doc
index bf7b3d5ced..b044d24df7 160000
--- a/doc
+++ b/doc
@@ -1 +1 @@
-Subproject commit bf7b3d5ced664a048f7ae9369cd7c6a17be43dbe
+Subproject commit b044d24df7e40d1acff7f178610de4ce3c39adb0
diff --git a/scripts/base/init-bare.zeek b/scripts/base/init-bare.zeek
index b0e7439438..12fcce29b2 100644
--- a/scripts/base/init-bare.zeek
+++ b/scripts/base/init-bare.zeek
@@ -96,6 +96,13 @@ type table_string_of_count: table[string] of count;
 ##    directly and then remove this alias.
 type files_tag_set: set[Files::Tag];
 
+## A set of intervals.
+##
+## .. todo:: We need this type definition only for declaring builtin functions
+##    via ``bifcl``. We should extend ``bifcl`` to understand composite types
+##    directly and then remove this alias.
+type interval_set: set[interval];
+
 ## A structure indicating a MIME type and strength of a match against
 ## file magic signatures.
 ##
diff --git a/scripts/base/protocols/conn/thresholds.zeek b/scripts/base/protocols/conn/thresholds.zeek
index d4ae21e1ab..c47f218d88 100644
--- a/scripts/base/protocols/conn/thresholds.zeek
+++ b/scripts/base/protocols/conn/thresholds.zeek
@@ -8,8 +8,9 @@ export {
 	type Thresholds: record {
 		orig_byte: set[count] &default=count_set(); ##< current originator byte thresholds we watch for
 		resp_byte: set[count] &default=count_set(); ##< current responder byte thresholds we watch for
-		orig_packet: set[count] &default=count_set(); ##< corrent originator packet thresholds we watch for
-		resp_packet: set[count] &default=count_set(); ##< corrent responder packet thresholds we watch for
+		orig_packet: set[count] &default=count_set(); ##< current originator packet thresholds we watch for
+		resp_packet: set[count] &default=count_set(); ##< current responder packet thresholds we watch for
+		duration: set[interval] &default=interval_set(); ##< current duration thresholds we watch for
 	};
 
 	## Sets a byte threshold for connection sizes, adding it to potentially already existing thresholds.
@@ -36,6 +37,16 @@ export {
 	## Returns: T on success, F on failure.
 	global set_packets_threshold: function(c: connection, threshold: count, is_orig: bool): bool;
 
+	## Sets a duration threshold for a connection, adding it to potentially already existing thresholds.
+	## conn_duration_threshold_crossed will be raised for each set threshold.
+	##
+	## cid: The connection id.
+	##
+	## threshold: Threshold in seconds.
+	##
+	## Returns: T on success, F on failure.
+	global set_duration_threshold: function(c: connection, threshold: interval): bool;
+
 	## Deletes a byte threshold for connection sizes.
 	##
 	## cid: The connection id.
@@ -58,6 +69,15 @@ export {
 	## Returns: T on success, F on failure.
 	global delete_packets_threshold: function(c: connection, threshold: count, is_orig: bool): bool;
 
+	## Deletes a duration threshold for a connection.
+	##
+	## cid: The connection id.
+	##
+	## threshold: Threshold in packets.
+	##
+	## Returns: T on success, F on failure.
+	global delete_duration_threshold: function(c: connection, threshold: interval): bool;
+
 	## Generated for a connection that crossed a set byte threshold
 	##
 	## c: the connection
@@ -75,12 +95,26 @@ export {
 	##
 	## is_orig: True if the threshold was crossed by the originator of the connection
 	global packets_threshold_crossed: event(c: connection, threshold: count, is_orig: bool);
+
+	## Generated for a connection that crossed a set duration threshold. Note that this event is
+	## not raised at the exact moment that a duration threshold is crossed; instead it is raised
+	## when the next packet is seen after the threshold has been crossed. On a connection that is
+	## idle, this can be raised significantly later.
+	##
+	## c: the connection
+	##
+	## threshold: the threshold that was set
+	##
+	## is_orig: True if the threshold was crossed by the originator of the connection
+	global duration_threshold_crossed: event(c: connection, threshold: interval, is_orig: bool);
 }
 
 redef record connection += {
 	thresholds: ConnThreshold::Thresholds &optional;
 };
 
+type threshold_type: enum { BYTES, PACKETS, DURATION };
+
 function set_conn(c: connection)
 	{
 	if ( c?$thresholds )
@@ -114,43 +148,77 @@ function find_min_threshold(t: set[count]): count
 	return min;
 	}
 
-function set_current_threshold(c: connection, bytes: bool, is_orig: bool): bool
+function find_min_duration_threshold(t: set[interval]): interval
+	{
+	if ( |t| == 0 )
+		return 0secs;
+
+	local first = T;
+	local min: interval = 0 secs;
+
+	for ( i in t )
+		{
+		if ( first )
+			{
+			min = i;
+			first = F;
+			}
+		else
+			{
+			if ( i < min )
+				min = i;
+			}
+		}
+
+	return min;
+	}
+
+function set_current_threshold(c: connection, ttype: threshold_type, is_orig: bool): bool
 	{
 	local t: count = 0;
 	local cur: count = 0;
+	local td: interval = 0 secs;
+	local curd: interval = 0 secs;
 
-	if ( bytes && is_orig )
+	if ( ttype == BYTES && is_orig )
 		{
 		t = find_min_threshold(c$thresholds$orig_byte);
 		cur = get_current_conn_bytes_threshold(c$id, is_orig);
 		}
-	else if ( bytes && ! is_orig )
+	else if ( ttype == BYTES && ! is_orig )
 		{
 		t = find_min_threshold(c$thresholds$resp_byte);
 		cur = get_current_conn_bytes_threshold(c$id, is_orig);
 		}
-	else if ( ! bytes && is_orig )
+	else if ( ttype == PACKETS && is_orig )
 		{
 		t = find_min_threshold(c$thresholds$orig_packet);
 		cur = get_current_conn_packets_threshold(c$id, is_orig);
 		}
-	else if ( ! bytes && ! is_orig )
+	else if ( ttype == PACKETS && ! is_orig )
 		{
 		t = find_min_threshold(c$thresholds$resp_packet);
 		cur = get_current_conn_packets_threshold(c$id, is_orig);
 		}
+	else if ( ttype == DURATION )
+		{
+		td = find_min_duration_threshold(c$thresholds$duration);
+		curd = get_current_conn_duration_threshold(c$id);
+		}
 
-	if ( t == cur )
+	if ( t == cur && td == curd )
 		return T;
 
-	if ( bytes && is_orig )
+	if ( ttype == BYTES && is_orig )
 		return set_current_conn_bytes_threshold(c$id, t, T);
-	else if ( bytes && ! is_orig )
+	else if ( ttype == BYTES && ! is_orig )
 		return set_current_conn_bytes_threshold(c$id, t, F);
-	else if ( ! bytes && is_orig )
+	else if ( ttype == PACKETS && is_orig )
 		return set_current_conn_packets_threshold(c$id, t, T);
-	else if ( ! bytes && ! is_orig )
+	else if ( ttype == PACKETS && ! is_orig )
 		return set_current_conn_packets_threshold(c$id, t, F);
+	else if ( ttype == DURATION )
+		return set_current_conn_duration_threshold(c$id, td);
 	}
 
 function set_bytes_threshold(c: connection, threshold: count, is_orig: bool): bool
@@ -165,7 +233,7 @@ function set_bytes_threshold(c: connection, threshold: count, is_orig: bool): bo
 	else
 		add c$thresholds$resp_byte[threshold];
 
-	return set_current_threshold(c, T, is_orig);
+	return set_current_threshold(c, BYTES, is_orig);
 	}
 
 function set_packets_threshold(c: connection, threshold: count, is_orig: bool): bool
@@ -180,7 +248,19 @@ function set_packets_threshold(c: connection, threshold: count, is_orig: bool):
 	else
 		add c$thresholds$resp_packet[threshold];
 
-	return set_current_threshold(c, F, is_orig);
+	return set_current_threshold(c, PACKETS, is_orig);
+	}
+
+function set_duration_threshold(c: connection, threshold: interval): bool
+	{
+	set_conn(c);
+
+	if ( threshold == 0 secs )
+		return F;
+
+	add c$thresholds$duration[threshold];
+
+	return set_current_threshold(c, DURATION, T);
 	}
 
 function delete_bytes_threshold(c: connection, threshold: count, is_orig: bool): bool
@@ -190,13 +270,13 @@ function delete_bytes_threshold(c: connection, threshold: count, is_orig: bool):
 	if ( is_orig && threshold in c$thresholds$orig_byte )
 		{
 		delete c$thresholds$orig_byte[threshold];
-		set_current_threshold(c, T, is_orig);
+		set_current_threshold(c, BYTES, is_orig);
 		return T;
 		}
 	else if ( ! is_orig && threshold in c$thresholds$resp_byte )
 		{
 		delete c$thresholds$resp_byte[threshold];
-		set_current_threshold(c, T, is_orig);
+		set_current_threshold(c, BYTES, is_orig);
 		return T;
 		}
 
@@ -210,13 +290,27 @@ function delete_packets_threshold(c: connection, threshold: count, is_orig: bool
 	if ( is_orig && threshold in c$thresholds$orig_packet )
 		{
 		delete c$thresholds$orig_packet[threshold];
-		set_current_threshold(c, F, is_orig);
+		set_current_threshold(c, PACKETS, is_orig);
 		return T;
 		}
 	else if ( ! is_orig && threshold in c$thresholds$resp_packet )
 		{
 		delete c$thresholds$resp_packet[threshold];
-		set_current_threshold(c, F, is_orig);
+		set_current_threshold(c, PACKETS, is_orig);
+		return T;
+		}
+
+	return F;
+	}
+
+function delete_duration_threshold(c: connection, threshold: interval): bool
+	{
+	set_conn(c);
+
+	if ( threshold in c$thresholds$duration )
+		{
+		delete c$thresholds$duration[threshold];
+		set_current_threshold(c, DURATION, T);
 		return T;
 		}
 
@@ -225,6 +319,9 @@ function delete_packets_threshold(c: connection, threshold: count, is_orig: bool
 
 event conn_bytes_threshold_crossed(c: connection, threshold: count, is_orig: bool) &priority=5
 	{
+	if ( ! c?$thresholds )
+		return;
+
 	if ( is_orig && threshold in c$thresholds$orig_byte )
 		{
 		delete c$thresholds$orig_byte[threshold];
@@ -236,11 +333,14 @@ event conn_bytes_threshold_crossed(c: connection, threshold: count, is_orig: boo
 		event ConnThreshold::bytes_threshold_crossed(c, threshold, is_orig);
 		}
 
-	set_current_threshold(c, T, is_orig);
+	set_current_threshold(c, BYTES, is_orig);
 	}
 
 event conn_packets_threshold_crossed(c: connection, threshold: count, is_orig: bool) &priority=5
 	{
+	if ( ! c?$thresholds )
+		return;
+
 	if ( is_orig && threshold in c$thresholds$orig_packet )
 		{
 		delete c$thresholds$orig_packet[threshold];
@@ -252,5 +352,19 @@ event conn_packets_threshold_crossed(c: connection, threshold: count, is_orig: b
 		event ConnThreshold::packets_threshold_crossed(c, threshold, is_orig);
 		}
 
-	set_current_threshold(c, F, is_orig);
+	set_current_threshold(c, PACKETS, is_orig);
+	}
+
+event conn_duration_threshold_crossed(c: connection, threshold: interval, is_orig: bool) &priority=5
+	{
+	if ( ! c?$thresholds )
+		return;
+
+	if ( threshold in c$thresholds$duration )
+		{
+		delete c$thresholds$duration[threshold];
+		event ConnThreshold::duration_threshold_crossed(c, threshold, is_orig);
+		}
+
+	set_current_threshold(c, DURATION, is_orig);
 	}
diff --git a/src/analyzer/protocol/conn-size/ConnSize.cc b/src/analyzer/protocol/conn-size/ConnSize.cc
index 1b18335e7f..6a8d911e4c 100644
--- a/src/analyzer/protocol/conn-size/ConnSize.cc
+++ b/src/analyzer/protocol/conn-size/ConnSize.cc
@@ -13,8 +13,9 @@ using namespace analyzer::conn_size;
 ConnSize_Analyzer::ConnSize_Analyzer(Connection* c)
     : Analyzer("CONNSIZE", c),
       orig_bytes(), resp_bytes(), orig_pkts(), resp_pkts(),
-      orig_bytes_thresh(), resp_bytes_thresh(), orig_pkts_thresh(), resp_pkts_thresh()
+      orig_bytes_thresh(), resp_bytes_thresh(), orig_pkts_thresh(), resp_pkts_thresh(), duration_thresh()
 	{
+	start_time = c->StartTime();
 	}
 
 
@@ -54,7 +55,7 @@ void ConnSize_Analyzer::ThresholdEvent(EventHandlerPtr f, uint64 threshold, bool
 	});
 	}
 
-void ConnSize_Analyzer::CheckSizes(bool is_orig)
+void ConnSize_Analyzer::CheckThresholds(bool is_orig)
 	{
 	if ( is_orig )
 		{
@@ -84,6 +85,19 @@ void ConnSize_Analyzer::CheckSizes(bool is_orig)
 			resp_pkts_thresh = 0;
 			}
 		}
+
+	if ( duration_thresh != 0 )
+		{
+		if ( duration_thresh > ( network_time - start_time ) && conn_duration_threshold_crossed )
+			{
+			ConnectionEventFast(conn_duration_threshold_crossed, {
+					BuildConnVal(),
+					new Val(duration_thresh, TYPE_INTERVAL),
+					val_mgr->GetBool(is_orig),
+			});
+			duration_thresh = 0;
+			}
+		}
 	}
 
 void ConnSize_Analyzer::DeliverPacket(int len, const u_char* data, bool is_orig, uint64 seq, const IP_Hdr* ip, int caplen)
@@ -101,10 +115,10 @@ void ConnSize_Analyzer::DeliverPacket(int len, const u_char* data, bool is_orig,
 		resp_pkts ++;
 		}
 
-	CheckSizes(is_orig);
+	CheckThresholds(is_orig);
 	}
 
-void ConnSize_Analyzer::SetThreshold(uint64 threshold, bool bytes, bool orig)
+void ConnSize_Analyzer::SetByteAndPacketThreshold(uint64 threshold, bool bytes, bool orig)
 	{
 	if ( bytes )
 		{
@@ -122,10 +136,10 @@ void ConnSize_Analyzer::SetThreshold(uint64 threshold, bool bytes, bool orig)
 		}
 
 	// Check if threshold is already crossed.
-	CheckSizes(orig);
+	CheckThresholds(orig);
 	}
 
-uint64_t ConnSize_Analyzer::GetThreshold(bool bytes, bool orig)
+uint64_t ConnSize_Analyzer::GetByteAndPacketThreshold(bool bytes, bool orig)
 	{
 	if ( bytes )
 		{
@@ -143,6 +157,14 @@ uint64_t ConnSize_Analyzer::GetThreshold(bool bytes, bool orig)
 		}
 	}
 
+void ConnSize_Analyzer::SetDurationThreshold(double duration)
+	{
+	duration_thresh = duration;
+
+	// for duration thresholds, it does not matter which direction we check.
+	CheckThresholds(true);
+	}
+
 void ConnSize_Analyzer::UpdateConnVal(RecordVal *conn_val)
 	{
 	// RecordType *connection_type is decleared in NetVar.h
@@ -181,4 +203,3 @@ void ConnSize_Analyzer::FlipRoles()
 	orig_pkts = resp_pkts;
 	resp_pkts = tmp;
 	}
-
diff --git a/src/analyzer/protocol/conn-size/ConnSize.h b/src/analyzer/protocol/conn-size/ConnSize.h
index b272f8539c..106b457452 100644
--- a/src/analyzer/protocol/conn-size/ConnSize.h
+++ b/src/analyzer/protocol/conn-size/ConnSize.h
@@ -21,8 +21,11 @@ public:
 	void UpdateConnVal(RecordVal *conn_val) override;
 	void FlipRoles() override;
 
-	void SetThreshold(uint64_t threshold, bool bytes, bool orig);
-	uint64 GetThreshold(bool bytes, bool orig);
+	void SetByteAndPacketThreshold(uint64_t threshold, bool bytes, bool orig);
+	uint64 GetByteAndPacketThreshold(bool bytes, bool orig);
+
+	void SetDurationThreshold(double duration);
+	double GetDurationThreshold() { return duration_thresh; };
 
 	static analyzer::Analyzer* Instantiate(Connection* conn)
 		{ return new ConnSize_Analyzer(conn); }
@@ -30,7 +33,7 @@ public:
 protected:
 	void DeliverPacket(int len, const u_char* data, bool is_orig,
 					uint64 seq, const IP_Hdr* ip, int caplen) override;
-	void CheckSizes(bool is_orig);
+	void CheckThresholds(bool is_orig);
 
 	void ThresholdEvent(EventHandlerPtr f, uint64 threshold, bool is_orig);
 
@@ -43,6 +46,9 @@ protected:
 	uint64_t resp_bytes_thresh;
 	uint64_t orig_pkts_thresh;
 	uint64_t resp_pkts_thresh;
+
+	double start_time;
+	double duration_thresh;
 };
 
 } } // namespace analyzer::* 
diff --git a/src/analyzer/protocol/conn-size/events.bif b/src/analyzer/protocol/conn-size/events.bif
index 9b1007ec3b..7d22133d65 100644
--- a/src/analyzer/protocol/conn-size/events.bif
+++ b/src/analyzer/protocol/conn-size/events.bif
@@ -1,6 +1,6 @@
 ## Generated for a connection that crossed a set byte threshold. Note that this
 ## is a low level event that should usually be avoided for user code. Use
-## ConnThreshold::bytes_threshold_crossed instead.
+## :zeek:see:`ConnThreshold::bytes_threshold_crossed` instead.
 ##
 ## c: the connection
 ##
@@ -9,12 +9,13 @@
 ## is_orig: true if the threshold was crossed by the originator of the connection
 ##
 ## .. zeek:see:: set_current_conn_packets_threshold set_current_conn_bytes_threshold conn_packets_threshold_crossed
-##              get_current_conn_bytes_threshold get_current_conn_packets_threshold
+##               get_current_conn_bytes_threshold get_current_conn_packets_threshold conn_duration_threshold_crossed
+##               set_current_conn_duration_threshold get_current_conn_duration_threshold
 event conn_bytes_threshold_crossed%(c: connection, threshold: count, is_orig: bool%);
 
 ## Generated for a connection that crossed a set packet threshold. Note that this
 ## is a low level event that should usually be avoided for user code. Use
-## ConnThreshold::bytes_threshold_crossed instead.
+## :zeek:see:`ConnThreshold::packets_threshold_crossed` instead.
 ##
 ## c: the connection
 ##
@@ -23,5 +24,25 @@ event conn_bytes_threshold_crossed%(c: connection, threshold: count, is_orig: bo
 ## is_orig: true if the threshold was crossed by the originator of the connection
 ##
 ## .. zeek:see:: set_current_conn_packets_threshold set_current_conn_bytes_threshold conn_bytes_threshold_crossed
-##              get_current_conn_bytes_threshold get_current_conn_packets_threshold
+##               get_current_conn_bytes_threshold get_current_conn_packets_threshold conn_duration_threshold_crossed
+##               set_current_conn_duration_threshold get_current_conn_duration_threshold
 event conn_packets_threshold_crossed%(c: connection, threshold: count, is_orig: bool%);
+
+## Generated for a connection that crossed a set duration threshold. Note that this
+## is a low level event that should usually be avoided for user code. Use
+## :zeek:see:`ConnThreshold::duration_threshold_crossed` instead.
+##
+## Note that this event is not raised at the exact moment that a duration threshold is crossed; instead
+## it is raised when the next packet is seen after the threshold has been crossed. On a connection that is
+## idle, this can be raised significantly later.
+##
+## c: the connection
+##
+## threshold: the threshold that was set
+##
+## is_orig: true if the threshold was crossed by the originator of the connection
+##
+## .. zeek:see:: set_current_conn_packets_threshold set_current_conn_bytes_threshold conn_bytes_threshold_crossed
+##               get_current_conn_bytes_threshold get_current_conn_packets_threshold
+##               set_current_conn_duration_threshold get_current_conn_duration_threshold
+event conn_duration_threshold_crossed%(c: connection, threshold: interval, is_orig: bool%);
diff --git a/src/analyzer/protocol/conn-size/functions.bif b/src/analyzer/protocol/conn-size/functions.bif
index 9dc91bb722..74d153363e 100644
--- a/src/analyzer/protocol/conn-size/functions.bif
+++ b/src/analyzer/protocol/conn-size/functions.bif
@@ -18,7 +18,7 @@ static analyzer::Analyzer* GetConnsizeAnalyzer(Val* cid)
 
 ## Sets the current byte threshold for connection sizes, overwriting any potential old
 ## threshold. Be aware that in nearly any case you will want to use the high level API
-## instead (ConnThreshold::set_bytes_threshold).
+## instead (:zeek:see:`ConnThreshold::set_bytes_threshold`).
 ##
 ## cid: The connection id.
 ##
@@ -27,21 +27,22 @@ static analyzer::Analyzer* GetConnsizeAnalyzer(Val* cid)
 ## is_orig: If true, threshold is set for bytes from originator, otherwhise for bytes from responder.
 ##
 ## .. zeek:see:: set_current_conn_packets_threshold conn_bytes_threshold_crossed conn_packets_threshold_crossed
-##              get_current_conn_bytes_threshold get_current_conn_packets_threshold
+##               get_current_conn_bytes_threshold get_current_conn_packets_threshold
+##               set_current_conn_duration_threshold get_current_conn_duration_threshold
 function set_current_conn_bytes_threshold%(cid: conn_id, threshold: count, is_orig: bool%): bool
 	%{
 	analyzer::Analyzer* a = GetConnsizeAnalyzer(cid);
 	if ( ! a )
 		return val_mgr->GetBool(0);
 
-	static_cast<analyzer::conn_size::ConnSize_Analyzer*>(a)->SetThreshold(threshold, 1, is_orig);
+	static_cast<analyzer::conn_size::ConnSize_Analyzer*>(a)->SetByteAndPacketThreshold(threshold, 1, is_orig);
 
 	return val_mgr->GetBool(1);
 	%}
 
 ## Sets a threshold for connection packets, overwtiting any potential old thresholds.
 ## Be aware that in nearly any case you will want to use the high level API
-## instead (ConnThreshold::set_packets_threshold).
+## instead (:zeek:see:`ConnThreshold::set_packets_threshold`).
 ##
 ## cid: The connection id.
 ##
@@ -50,19 +51,42 @@ function set_current_conn_bytes_threshold%(cid: conn_id, threshold: count, is_or
 ## is_orig: If true, threshold is set for packets from originator, otherwhise for packets from responder.
 ##
 ## .. zeek:see:: set_current_conn_bytes_threshold conn_bytes_threshold_crossed conn_packets_threshold_crossed
-##              get_current_conn_bytes_threshold get_current_conn_packets_threshold
+##               get_current_conn_bytes_threshold get_current_conn_packets_threshold
+##               set_current_conn_duration_threshold get_current_conn_duration_threshold
 function set_current_conn_packets_threshold%(cid: conn_id, threshold: count, is_orig: bool%): bool
 	%{
 	analyzer::Analyzer* a = GetConnsizeAnalyzer(cid);
 	if ( ! a )
 		return val_mgr->GetBool(0);
 
-	static_cast<analyzer::conn_size::ConnSize_Analyzer*>(a)->SetThreshold(threshold, 0, is_orig);
+	static_cast<analyzer::conn_size::ConnSize_Analyzer*>(a)->SetByteAndPacketThreshold(threshold, 0, is_orig);
 
 	return val_mgr->GetBool(1);
 	%}
 
-## Gets the current byte threshold size for a connection.
+## Sets the current duration threshold for connection, overwriting any potential old
+## threshold. Be aware that in nearly any case you will want to use the high level API
+## instead (:zeek:see:`ConnThreshold::set_duration_threshold`).
+##
+## cid: The connection id.
+##
+## threshold: Threshold in seconds.
+##
+## .. zeek:see:: set_current_conn_packets_threshold conn_bytes_threshold_crossed conn_packets_threshold_crossed
+##               get_current_conn_bytes_threshold get_current_conn_packets_threshold
+##               get_current_conn_duration_threshold
+function set_current_conn_duration_threshold%(cid: conn_id, threshold: interval%): bool
+	%{
+	analyzer::Analyzer* a = GetConnsizeAnalyzer(cid);
+	if ( ! a )
+		return val_mgr->GetBool(0);
+
+	static_cast<analyzer::conn_size::ConnSize_Analyzer*>(a)->SetDurationThreshold(threshold);
+
+	return val_mgr->GetBool(1);
+	%}
+
+# Gets the current byte threshold size for a connection.
 ##
 ## cid: The connection id.
 ##
@@ -71,14 +95,15 @@ function set_current_conn_packets_threshold%(cid: conn_id, threshold: count, is_
 ## Returns: 0 if no threshold is set or the threshold in bytes
 ##
 ## .. zeek:see:: set_current_conn_packets_threshold conn_bytes_threshold_crossed conn_packets_threshold_crossed
-##              get_current_conn_packets_threshold
+##               get_current_conn_packets_threshold set_current_conn_duration_threshold
+##               get_current_conn_duration_threshold
 function get_current_conn_bytes_threshold%(cid: conn_id, is_orig: bool%): count
 	%{
 	analyzer::Analyzer* a = GetConnsizeAnalyzer(cid);
 	if ( ! a )
 		return val_mgr->GetCount(0);
 
-	return val_mgr->GetCount(static_cast<analyzer::conn_size::ConnSize_Analyzer*>(a)->GetThreshold(1, is_orig));
+	return val_mgr->GetCount(static_cast<analyzer::conn_size::ConnSize_Analyzer*>(a)->GetByteAndPacketThreshold(1, is_orig));
 	%}
 
 ## Gets the current packet threshold size for a connection.
@@ -90,13 +115,29 @@ function get_current_conn_bytes_threshold%(cid: conn_id, is_orig: bool%): count
 ## Returns: 0 if no threshold is set or the threshold in packets
 ##
 ## .. zeek:see:: set_current_conn_packets_threshold conn_bytes_threshold_crossed conn_packets_threshold_crossed
-##              get_current_conn_bytes_threshold
+##               get_current_conn_bytes_threshold set_current_conn_duration_threshold get_current_conn_duration_threshold
 function get_current_conn_packets_threshold%(cid: conn_id, is_orig: bool%): count
 	%{
 	analyzer::Analyzer* a = GetConnsizeAnalyzer(cid);
 	if ( ! a )
 		return val_mgr->GetCount(0);
 
-	return val_mgr->GetCount(static_cast<analyzer::conn_size::ConnSize_Analyzer*>(a)->GetThreshold(0, is_orig));
+	return val_mgr->GetCount(static_cast<analyzer::conn_size::ConnSize_Analyzer*>(a)->GetByteAndPacketThreshold(0, is_orig));
 	%}
 
+## Gets the current duration threshold size for a connection.
+##
+## cid: The connection id.
+##
+## Returns: 0 if no threshold is set or the threshold in seconds
+##
+## .. zeek:see:: set_current_conn_packets_threshold conn_bytes_threshold_crossed conn_packets_threshold_crossed
+##               get_current_conn_packets_threshold set_current_conn_duration_threshold
+function get_current_conn_duration_threshold%(cid: conn_id%): interval
+	%{
+	analyzer::Analyzer* a = GetConnsizeAnalyzer(cid);
+	if ( ! a )
+		return new Val(0.0, TYPE_INTERVAL);
+
+	return new Val(static_cast<analyzer::conn_size::ConnSize_Analyzer*>(a)->GetDurationThreshold(), TYPE_INTERVAL);
+	%}
diff --git a/testing/btest/Baseline/core.conn-size-threshold/.stderr b/testing/btest/Baseline/core.conn-size-threshold/.stderr
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/testing/btest/Baseline/core.conn-size-threshold/.stdout b/testing/btest/Baseline/core.conn-size-threshold/.stdout
index 76ad7c0696..77e3ebf68f 100644
--- a/testing/btest/Baseline/core.conn-size-threshold/.stdout
+++ b/testing/btest/Baseline/core.conn-size-threshold/.stdout
@@ -2,11 +2,14 @@
 0
 0
 0
+0.0
 Threshold set for [orig_h=192.168.1.77, orig_p=57640/tcp, resp_h=66.198.80.67, resp_p=6667/tcp]
 3000
 2000
 63
 50
+0.0
+triggered duration, [orig_h=192.168.1.77, orig_p=57640/tcp, resp_h=66.198.80.67, resp_p=6667/tcp], 0.1, T
 triggered bytes, [orig_h=192.168.1.77, orig_p=57640/tcp, resp_h=66.198.80.67, resp_p=6667/tcp], 2000, F
 triggered bytes, [orig_h=192.168.1.77, orig_p=57640/tcp, resp_h=66.198.80.67, resp_p=6667/tcp], 3000, T
 triggered packets, [orig_h=192.168.1.77, orig_p=57640/tcp, resp_h=66.198.80.67, resp_p=6667/tcp], 50, F
@@ -14,10 +17,12 @@ triggered packets, [orig_h=192.168.1.77, orig_p=57640/tcp, resp_h=66.198.80.67,
 0
 0
 0
+0.0
 Threshold set for [orig_h=192.168.1.77, orig_p=57655/tcp, resp_h=209.197.168.151, resp_p=1024/tcp]
 3000
 2000
 63
 50
+0.1
 triggered bytes, [orig_h=192.168.1.77, orig_p=57655/tcp, resp_h=209.197.168.151, resp_p=1024/tcp], 2000, F
 triggered packets, [orig_h=192.168.1.77, orig_p=57640/tcp, resp_h=66.198.80.67, resp_p=6667/tcp], 63, T
diff --git a/testing/btest/Baseline/scripts.base.protocols.conn.threshold-delete/.stderr b/testing/btest/Baseline/scripts.base.protocols.conn.threshold-delete/.stderr
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/testing/btest/Baseline/scripts.base.protocols.conn.threshold-delete/.stdout b/testing/btest/Baseline/scripts.base.protocols.conn.threshold-delete/.stdout
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/testing/btest/Baseline/scripts.base.protocols.conn.threshold/.stdout b/testing/btest/Baseline/scripts.base.protocols.conn.threshold/.stdout
index f5ae35abc3..0b59896e78 100644
--- a/testing/btest/Baseline/scripts.base.protocols.conn.threshold/.stdout
+++ b/testing/btest/Baseline/scripts.base.protocols.conn.threshold/.stdout
@@ -1,10 +1,12 @@
 Threshold set for [orig_h=192.168.1.77, orig_p=57640/tcp, resp_h=66.198.80.67, resp_p=6667/tcp]
 triggered bytes, [orig_h=192.168.1.77, orig_p=57640/tcp, resp_h=66.198.80.67, resp_p=6667/tcp], 1, T
+triggered duration, [orig_h=192.168.1.77, orig_p=57640/tcp, resp_h=66.198.80.67, resp_p=6667/tcp], 0.2, T
 triggered bytes, [orig_h=192.168.1.77, orig_p=57640/tcp, resp_h=66.198.80.67, resp_p=6667/tcp], 2000, F
 triggered bytes, [orig_h=192.168.1.77, orig_p=57640/tcp, resp_h=66.198.80.67, resp_p=6667/tcp], 2500, T
 triggered bytes, [orig_h=192.168.1.77, orig_p=57640/tcp, resp_h=66.198.80.67, resp_p=6667/tcp], 2700, T
 triggered packets, [orig_h=192.168.1.77, orig_p=57640/tcp, resp_h=66.198.80.67, resp_p=6667/tcp], 50, F
 Threshold set for [orig_h=192.168.1.77, orig_p=57655/tcp, resp_h=209.197.168.151, resp_p=1024/tcp]
 triggered bytes, [orig_h=192.168.1.77, orig_p=57655/tcp, resp_h=209.197.168.151, resp_p=1024/tcp], 1, T
+triggered duration, [orig_h=192.168.1.77, orig_p=57655/tcp, resp_h=209.197.168.151, resp_p=1024/tcp], 0.2, T
 triggered bytes, [orig_h=192.168.1.77, orig_p=57655/tcp, resp_h=209.197.168.151, resp_p=1024/tcp], 2000, F
 triggered packets, [orig_h=192.168.1.77, orig_p=57640/tcp, resp_h=66.198.80.67, resp_p=6667/tcp], 52, F
diff --git a/testing/btest/core/conn-size-threshold.zeek b/testing/btest/core/conn-size-threshold.zeek
index d886846df5..02410a3001 100644
--- a/testing/btest/core/conn-size-threshold.zeek
+++ b/testing/btest/core/conn-size-threshold.zeek
@@ -1,5 +1,6 @@
 # @TEST-EXEC: zeek -r $TRACES/irc-dcc-send.trace %INPUT
 # @TEST-EXEC: btest-diff .stdout
+# @TEST-EXEC: btest-diff .stderr
 
 event connection_established(c: connection)
 	{
@@ -7,6 +8,7 @@ event connection_established(c: connection)
 	print get_current_conn_bytes_threshold(c$id, F);
 	print get_current_conn_packets_threshold(c$id, T);
 	print get_current_conn_packets_threshold(c$id, F);
+	print get_current_conn_duration_threshold(c$id);
 
 	print fmt("Threshold set for %s", cat(c$id));
 	set_current_conn_bytes_threshold(c$id, 3000, T);
@@ -15,10 +17,13 @@ event connection_established(c: connection)
 	set_current_conn_packets_threshold(c$id, 50, F);
 	set_current_conn_packets_threshold(c$id, 63, T);
 
+	set_current_conn_duration_threshold(c$id, 0.1 secs);
+
 	print get_current_conn_bytes_threshold(c$id, T);
 	print get_current_conn_bytes_threshold(c$id, F);
 	print get_current_conn_packets_threshold(c$id, T);
 	print get_current_conn_packets_threshold(c$id, F);
+	print get_current_conn_duration_threshold(c$id);
 	}
 
 event conn_bytes_threshold_crossed(c: connection, threshold: count, is_orig: bool)
@@ -30,3 +35,8 @@ event conn_packets_threshold_crossed(c: connection, threshold: count, is_orig: b
 	{
 	print "triggered packets", c$id, threshold, is_orig;
 	}
+
+event conn_duration_threshold_crossed(c: connection, threshold: interval, is_orig: bool)
+	{
+	print "triggered duration", c$id, threshold, is_orig;
+	}
diff --git a/testing/btest/scripts/base/protocols/conn/threshold-delete.zeek b/testing/btest/scripts/base/protocols/conn/threshold-delete.zeek
new file mode 100644
index 0000000000..e15e2013fd
--- /dev/null
+++ b/testing/btest/scripts/base/protocols/conn/threshold-delete.zeek
@@ -0,0 +1,30 @@
+# @TEST-EXEC: zeek -r $TRACES/irc-dcc-send.trace %INPUT
+# @TEST-EXEC: btest-diff .stdout
+# @TEST-EXEC: btest-diff .stderr
+#
+# This tests that no events are raised once all thresholds have been deleted.
+
+event connection_established(c: connection)
+	{
+	ConnThreshold::set_bytes_threshold(c, 1, T);
+	ConnThreshold::delete_bytes_threshold(c, 1, T);
+	ConnThreshold::set_duration_threshold(c, 0.1secs);
+	ConnThreshold::delete_duration_threshold(c, 0.1secs);
+	ConnThreshold::set_packets_threshold(c, 63, T);
+	ConnThreshold::delete_packets_threshold(c, 63, T);
+	}
+
+event ConnThreshold::bytes_threshold_crossed(c: connection, threshold: count, is_orig: bool)
+	{
+	print "triggered bytes", c$id, threshold, is_orig;
+	}
+
+event ConnThreshold::packets_threshold_crossed(c: connection, threshold: count, is_orig: bool)
+	{
+	print "triggered packets", c$id, threshold, is_orig;
+	}
+
+event ConnThreshold::duration_threshold_crossed(c: connection, threshold: interval, is_orig: bool)
+	{
+	print "triggered duration", c$id, threshold, is_orig;
+	}
diff --git a/testing/btest/scripts/base/protocols/conn/threshold.zeek b/testing/btest/scripts/base/protocols/conn/threshold.zeek
index 4ab01b4dbf..7bdca12861 100644
--- a/testing/btest/scripts/base/protocols/conn/threshold.zeek
+++ b/testing/btest/scripts/base/protocols/conn/threshold.zeek
@@ -10,6 +10,8 @@ event connection_established(c: connection)
 	ConnThreshold::set_bytes_threshold(c, 3000, T);
 	ConnThreshold::delete_bytes_threshold(c, 3000, T);
 	ConnThreshold::set_bytes_threshold(c, 2000, F);
+	ConnThreshold::set_duration_threshold(c, 0.1secs);
+	ConnThreshold::set_duration_threshold(c, 0.2secs);
 
 	ConnThreshold::set_packets_threshold(c, 50, F);
 	ConnThreshold::set_packets_threshold(c, 51, F);
@@ -17,6 +19,7 @@ event connection_established(c: connection)
 	ConnThreshold::delete_packets_threshold(c, 51, F);
 	ConnThreshold::set_packets_threshold(c, 63, T);
 	ConnThreshold::delete_packets_threshold(c, 63, T);
+	ConnThreshold::delete_duration_threshold(c, 0.1secs);
 	}
 
 event ConnThreshold::bytes_threshold_crossed(c: connection, threshold: count, is_orig: bool)
@@ -28,3 +31,8 @@ event ConnThreshold::packets_threshold_crossed(c: connection, threshold: count,
 	{
 	print "triggered packets", c$id, threshold, is_orig;
 	}
+
+event ConnThreshold::duration_threshold_crossed(c: connection, threshold: interval, is_orig: bool)
+	{
+	print "triggered duration", c$id, threshold, is_orig;
+	}