diff --git a/src/inet/linklayer/ieee80211/mac/Ieee80211Duration.h b/src/inet/linklayer/ieee80211/mac/Ieee80211Duration.h
new file mode 100644
index 00000000000..7496df17bfa
--- /dev/null
+++ b/src/inet/linklayer/ieee80211/mac/Ieee80211Duration.h
@@ -0,0 +1,44 @@
+//
+// SPDX-License-Identifier: LGPL-3.0-or-later
+//
+
+#ifndef __INET_IEEE80211DURATION_H
+#define __INET_IEEE80211DURATION_H
+
+#include "inet/common/INETDefs.h"
+
+namespace inet {
+namespace ieee80211 {
+
+// Only the ordinary 15-bit encoding denotes a reservation. Reserved and
+// special Duration/ID values must not enter response-duration arithmetic.
+inline simtime_t getIeee80211OrdinaryDuration(simtime_t duration)
+{
+    return duration >= SIMTIME_ZERO && duration <= SimTime(32767, SIMTIME_US) ? duration : SIMTIME_ZERO;
+}
+
+inline simtime_t normalizeIeee80211Duration(simtime_t duration)
+{
+    // IEEE Std 802.11-2024, 9.2.5.1: negative calculations become zero; fractions round upward.
+    if (duration <= SIMTIME_ZERO)
+        return SIMTIME_ZERO;
+    // 9.2.4.2, Table 9-9: ordinary Duration is 15 bits. AID is a separate representation.
+    if (duration > SimTime(32767, SIMTIME_US))
+        throw cRuntimeError("Calculated IEEE 802.11 Duration exceeds 32767 microseconds");
+    auto microseconds = duration.inUnit(SIMTIME_US);
+    if (SimTime(microseconds, SIMTIME_US) < duration)
+        microseconds++;
+    return SimTime(microseconds, SIMTIME_US);
+}
+
+inline uint16_t encodeIeee80211Duration(simtime_t duration)
+{
+    if (duration < SIMTIME_ZERO)
+        throw cRuntimeError("Cannot serialize an unset or negative IEEE 802.11 Duration");
+    return static_cast<uint16_t>(normalizeIeee80211Duration(duration).inUnit(SIMTIME_US));
+}
+
+} // namespace ieee80211
+} // namespace inet
+
+#endif
diff --git a/src/inet/linklayer/ieee80211/mac/Ieee80211MacHeaderSerializer.cc b/src/inet/linklayer/ieee80211/mac/Ieee80211MacHeaderSerializer.cc
index 2a482cded2f..c33160c40bd 100644
--- a/src/inet/linklayer/ieee80211/mac/Ieee80211MacHeaderSerializer.cc
+++ b/src/inet/linklayer/ieee80211/mac/Ieee80211MacHeaderSerializer.cc
@@ -6,6 +6,7 @@
 
 
 #include "inet/linklayer/ieee80211/mac/Ieee80211MacHeaderSerializer.h"
+#include "inet/linklayer/ieee80211/mac/Ieee80211Duration.h"
 
 #include "inet/common/checksum/Checksum.h"
 #include "inet/common/packet/serializer/ChunkSerializerRegistry.h"
@@ -185,7 +186,7 @@ void Ieee80211MacHeaderSerializer::serializeFields(MemoryOutputStream& stream, c
     // variants -- not just plain Data (ST_DATA) and QoS-Data (ST_DATA_WITH_QOS).
     if (macHeader->getFrameType() == 2) {
         auto dataHeader = dynamicPtrCast<const Ieee80211DataHeader>(chunk);
-        stream.writeUint16Le(dataHeader->getDurationField().inUnit(SIMTIME_US));
+        stream.writeUint16Le(ieee80211::encodeIeee80211Duration(dataHeader->getDurationField()));
         stream.writeMacAddress(dataHeader->getReceiverAddress());
         stream.writeMacAddress(dataHeader->getTransmitterAddress());
         stream.writeMacAddress(dataHeader->getAddress3());
@@ -222,7 +223,7 @@ void Ieee80211MacHeaderSerializer::serializeFields(MemoryOutputStream& stream, c
         case ST_ACTION:
         case ST_NOACKACTION: {
             auto mgmtHeader = dynamicPtrCast<const Ieee80211MgmtHeader>(chunk);
-            stream.writeUint16Le(mgmtHeader->getDurationField().inUnit(SIMTIME_US));
+            stream.writeUint16Le(ieee80211::encodeIeee80211Duration(mgmtHeader->getDurationField()));
             stream.writeMacAddress(mgmtHeader->getReceiverAddress());
             stream.writeMacAddress(mgmtHeader->getTransmitterAddress());
             stream.writeMacAddress(mgmtHeader->getAddress3());
@@ -298,7 +299,7 @@ void Ieee80211MacHeaderSerializer::serializeFields(MemoryOutputStream& stream, c
         }
         case ST_RTS: {
             auto rtsFrame = dynamicPtrCast<const Ieee80211RtsFrame>(chunk);
-            stream.writeUint16Le(rtsFrame->getDurationField().inUnit(SIMTIME_US));
+            stream.writeUint16Le(ieee80211::encodeIeee80211Duration(rtsFrame->getDurationField()));
             stream.writeMacAddress(rtsFrame->getReceiverAddress());
             stream.writeMacAddress(rtsFrame->getTransmitterAddress());
             if (stream.getLength() - startPos != rtsFrame->getChunkLength())
@@ -308,7 +309,7 @@ void Ieee80211MacHeaderSerializer::serializeFields(MemoryOutputStream& stream, c
         }
         case ST_CTS: {
             auto ctsFrame = dynamicPtrCast<const Ieee80211CtsFrame>(chunk);
-            stream.writeUint16Le(ctsFrame->getDurationField().inUnit(SIMTIME_US));
+            stream.writeUint16Le(ieee80211::encodeIeee80211Duration(ctsFrame->getDurationField()));
             stream.writeMacAddress(ctsFrame->getReceiverAddress());
             if (stream.getLength() - startPos != ctsFrame->getChunkLength())
                 throw cRuntimeError("Cannot serialize the Ieee80211CtsFrame: chunkLength is %d B, does not match the %d B of serialized fields",
@@ -317,7 +318,7 @@ void Ieee80211MacHeaderSerializer::serializeFields(MemoryOutputStream& stream, c
         }
         case ST_ACK: {
             auto ackFrame = dynamicPtrCast<const Ieee80211AckFrame>(chunk);
-            stream.writeUint16Le(ackFrame->getDurationField().inUnit(SIMTIME_US));
+            stream.writeUint16Le(ieee80211::encodeIeee80211Duration(ackFrame->getDurationField()));
             stream.writeMacAddress(ackFrame->getReceiverAddress());
             if (stream.getLength() - startPos != ackFrame->getChunkLength())
                 throw cRuntimeError("Cannot serialize the Ieee80211AckFrame: chunkLength is %d B, does not match the %d B of serialized fields",
@@ -326,7 +327,7 @@ void Ieee80211MacHeaderSerializer::serializeFields(MemoryOutputStream& stream, c
         }
         case ST_BLOCKACK_REQ: {
             auto blockAckReq = dynamicPtrCast<const Ieee80211BlockAckReq>(chunk);
-            stream.writeUint16Le(blockAckReq->getDurationField().inUnit(SIMTIME_US));
+            stream.writeUint16Le(ieee80211::encodeIeee80211Duration(blockAckReq->getDurationField()));
             stream.writeMacAddress(blockAckReq->getReceiverAddress());
             stream.writeMacAddress(blockAckReq->getTransmitterAddress());
             bool multiTid = blockAckReq->getMultiTid();
@@ -362,7 +363,7 @@ void Ieee80211MacHeaderSerializer::serializeFields(MemoryOutputStream& stream, c
         }
         case ST_BLOCKACK: {
             auto blockAck = dynamicPtrCast<const Ieee80211BlockAck>(chunk);
-            stream.writeUint16Le(blockAck->getDurationField().inUnit(SIMTIME_US));
+            stream.writeUint16Le(ieee80211::encodeIeee80211Duration(blockAck->getDurationField()));
             stream.writeMacAddress(blockAck->getReceiverAddress());
             stream.writeMacAddress(blockAck->getTransmitterAddress());
             bool multiTid = blockAck->getMultiTid();
diff --git a/src/inet/linklayer/ieee80211/mac/Rx.cc b/src/inet/linklayer/ieee80211/mac/Rx.cc
index 19b9da0889c..0627ec68f5d 100644
--- a/src/inet/linklayer/ieee80211/mac/Rx.cc
+++ b/src/inet/linklayer/ieee80211/mac/Rx.cc
@@ -99,8 +99,11 @@ bool Rx::lowerFrameReceived(Packet *packet)
     if (isFrameOk) {
         EV_INFO << "Received frame from PHY: " << packet << endl;
         const auto& header = packet->peekAtFront<Ieee80211MacHeader>();
-        if (header->getReceiverAddress() != address)
-            setOrExtendNav(header->getDurationField());
+        // IEEE Std 802.11-2024, 9.2.4.2: bit 15 distinguishes special
+        // Duration/ID encodings; they are not ordinary NAV intervals.
+        auto duration = header->getDurationField();
+        if (header->getReceiverAddress() != address && duration >= SIMTIME_ZERO && duration <= SimTime(32767, SIMTIME_US))
+            setOrExtendNav(duration);
         return true;
     }
     else {
diff --git a/src/inet/linklayer/ieee80211/mac/aggregation/MsduDeaggregation.cc b/src/inet/linklayer/ieee80211/mac/aggregation/MsduDeaggregation.cc
index bd4b3e82321..6681e7ae443 100644
--- a/src/inet/linklayer/ieee80211/mac/aggregation/MsduDeaggregation.cc
+++ b/src/inet/linklayer/ieee80211/mac/aggregation/MsduDeaggregation.cc
@@ -69,6 +69,7 @@ std::vector<Packet *> *MsduDeaggregation::deaggregateFrame(Packet *aggregatedFra
         if (header->getToDS() && header->getFromDS())
             header->addChunkLength(B(6));
         header->setTid(tid);
+        header->setDurationField(amsduHeader->getDurationField());
         header->setSequenceNumber(SequenceNumberCyclic(0));
         setExplodedFrameAddress(header, msduSubframeHeader, amsduHeader);
         frame->insertAtFront(header);
diff --git a/src/inet/linklayer/ieee80211/mac/blockack/RecipientBlockAckProcedure.cc b/src/inet/linklayer/ieee80211/mac/blockack/RecipientBlockAckProcedure.cc
index ab7cb050e5f..74d63f2c446 100644
--- a/src/inet/linklayer/ieee80211/mac/blockack/RecipientBlockAckProcedure.cc
+++ b/src/inet/linklayer/ieee80211/mac/blockack/RecipientBlockAckProcedure.cc
@@ -5,6 +5,7 @@
 //
 
 
+#include "inet/linklayer/ieee80211/mac/Ieee80211Duration.h"
 #include "inet/linklayer/ieee80211/mac/blockack/RecipientBlockAckProcedure.h"
 
 #include "inet/linklayer/ieee80211/mac/blockack/RecipientBlockAckAgreement.h"
@@ -25,6 +26,7 @@ void RecipientBlockAckProcedure::processReceivedBlockAckReq(Packet *blockAckPack
         if (ackPolicy->isBlockAckNeeded(basicBlockAckReq, agreement)) {
             auto blockAck = buildBlockAck(basicBlockAckReq, agreement);
             auto duration = ackPolicy->computeBasicBlockAckDurationField(blockAckPacketReq, basicBlockAckReq);
+            duration = normalizeIeee80211Duration(duration);
             blockAck->setDurationField(duration);
             auto blockAckPacket = new Packet("BasicBlockAck", blockAck);
             EV_DEBUG << "Duration for " << blockAckPacket->getName() << " is set to " << duration << " s.\n";
diff --git a/src/inet/linklayer/ieee80211/mac/coordinationfunction/Dcf.cc b/src/inet/linklayer/ieee80211/mac/coordinationfunction/Dcf.cc
index ddb1cf9aa65..1452ed3ca71 100644
--- a/src/inet/linklayer/ieee80211/mac/coordinationfunction/Dcf.cc
+++ b/src/inet/linklayer/ieee80211/mac/coordinationfunction/Dcf.cc
@@ -5,6 +5,7 @@
 //
 
 
+#include "inet/linklayer/ieee80211/mac/Ieee80211Duration.h"
 #include "inet/linklayer/ieee80211/mac/coordinationfunction/Dcf.h"
 
 #include "inet/common/ModuleAccess.h"
@@ -194,6 +195,7 @@ void Dcf::transmitFrame(Packet *packet, simtime_t ifs)
     auto pendingPacket = channelAccess->getInProgressFrames()->getPendingFrameFor(packet);
     auto duration = originatorProtectionMechanism->computeDurationField(packet, header, pendingPacket, pendingPacket == nullptr ? nullptr : pendingPacket->peekAtFront<Ieee80211DataOrMgmtHeader>());
     const auto& updatedHeader = packet->removeAtFront<Ieee80211MacHeader>();
+    duration = normalizeIeee80211Duration(duration);
     updatedHeader->setDurationField(duration);
     EV_DEBUG << "Duration for " << packet->getName() << " is set to " << duration << " s.\n";
     packet->insertAtFront(updatedHeader);
diff --git a/src/inet/linklayer/ieee80211/mac/coordinationfunction/Hcf.cc b/src/inet/linklayer/ieee80211/mac/coordinationfunction/Hcf.cc
index e64ce4db852..9292a1f17ac 100644
--- a/src/inet/linklayer/ieee80211/mac/coordinationfunction/Hcf.cc
+++ b/src/inet/linklayer/ieee80211/mac/coordinationfunction/Hcf.cc
@@ -5,6 +5,7 @@
 //
 
 
+#include "inet/linklayer/ieee80211/mac/Ieee80211Duration.h"
 #include "inet/linklayer/ieee80211/mac/coordinationfunction/Hcf.h"
 
 #include "inet/common/ModuleAccess.h"
@@ -719,6 +720,7 @@ void Hcf::transmitFrame(Packet *packet, simtime_t ifs)
             const auto& pendingHeader = pendingPacket == nullptr ? nullptr : pendingPacket->peekAtFront<Ieee80211DataOrMgmtHeader>();
             auto duration = singleProtectionMechanism->computeDurationField(packet, header, pendingPacket, pendingHeader, txop, recipientAckPolicy);
             auto header = packet->removeAtFront<Ieee80211MacHeader>();
+            duration = normalizeIeee80211Duration(duration);
             header->setDurationField(duration);
             EV_DEBUG << "Duration for " << packet->getName() << " is set to " << duration << " s.\n";
             packet->insertAtFront(header);
diff --git a/src/inet/linklayer/ieee80211/mac/recipient/CtsPolicy.cc b/src/inet/linklayer/ieee80211/mac/recipient/CtsPolicy.cc
index 17edca5ffea..d90db6f5d1e 100644
--- a/src/inet/linklayer/ieee80211/mac/recipient/CtsPolicy.cc
+++ b/src/inet/linklayer/ieee80211/mac/recipient/CtsPolicy.cc
@@ -6,6 +6,7 @@
 
 
 #include "inet/linklayer/ieee80211/mac/recipient/CtsPolicy.h"
+#include "inet/linklayer/ieee80211/mac/Ieee80211Duration.h"
 
 #include "inet/common/ModuleAccess.h"
 
@@ -35,7 +36,7 @@ simtime_t CtsPolicy::computeCtsDuration(Packet *rtsPacket, const Ptr<const Ieee8
 //
 simtime_t CtsPolicy::computeCtsDurationField(Packet *rtsPacket, const Ptr<const Ieee80211RtsFrame>& rtsFrame) const
 {
-    simtime_t duration = rtsFrame->getDurationField() - modeSet->getSifsTime() - computeCtsDuration(rtsPacket, rtsFrame);
+    simtime_t duration = getIeee80211OrdinaryDuration(rtsFrame->getDurationField()) - modeSet->getSifsTime() - computeCtsDuration(rtsPacket, rtsFrame);
     return duration < 0 ? 0 : duration;
 }
 
diff --git a/src/inet/linklayer/ieee80211/mac/recipient/CtsProcedure.cc b/src/inet/linklayer/ieee80211/mac/recipient/CtsProcedure.cc
index dd0dad9936f..0cb1c24fdee 100644
--- a/src/inet/linklayer/ieee80211/mac/recipient/CtsProcedure.cc
+++ b/src/inet/linklayer/ieee80211/mac/recipient/CtsProcedure.cc
@@ -5,6 +5,7 @@
 //
 
 
+#include "inet/linklayer/ieee80211/mac/Ieee80211Duration.h"
 #include "inet/linklayer/ieee80211/mac/recipient/CtsProcedure.h"
 
 namespace inet {
@@ -18,6 +19,7 @@ void CtsProcedure::processReceivedRts(Packet *rtsPacket, const Ptr<const Ieee802
     if (ctsPolicy->isCtsNeeded(rtsFrame)) {
         auto ctsFrame = buildCts(rtsFrame);
         auto duration = ctsPolicy->computeCtsDurationField(rtsPacket, rtsFrame);
+        duration = normalizeIeee80211Duration(duration);
         ctsFrame->setDurationField(duration);
         auto ctsPacket = new Packet("CTS", ctsFrame);
         EV_DEBUG << "Duration for " << ctsPacket->getName() << " is set to " << duration << " s.\n";
diff --git a/src/inet/linklayer/ieee80211/mac/recipient/QosCtsPolicy.cc b/src/inet/linklayer/ieee80211/mac/recipient/QosCtsPolicy.cc
index afd8af57f9d..8fe29cce3ea 100644
--- a/src/inet/linklayer/ieee80211/mac/recipient/QosCtsPolicy.cc
+++ b/src/inet/linklayer/ieee80211/mac/recipient/QosCtsPolicy.cc
@@ -6,6 +6,7 @@
 
 
 #include "inet/linklayer/ieee80211/mac/recipient/QosCtsPolicy.h"
+#include "inet/linklayer/ieee80211/mac/Ieee80211Duration.h"
 
 #include "inet/common/ModuleAccess.h"
 
@@ -36,7 +37,7 @@ simtime_t QosCtsPolicy::computeCtsDuration(Packet *rtsPacket, const Ptr<const Ie
 //
 simtime_t QosCtsPolicy::computeCtsDurationField(Packet *rtsPacket, const Ptr<const Ieee80211RtsFrame>& rtsFrame) const
 {
-    simtime_t duration = rtsFrame->getDurationField() - modeSet->getSifsTime() - computeCtsDuration(rtsPacket, rtsFrame);
+    simtime_t duration = getIeee80211OrdinaryDuration(rtsFrame->getDurationField()) - modeSet->getSifsTime() - computeCtsDuration(rtsPacket, rtsFrame);
     return duration < 0 ? 0 : duration;
 }
 
diff --git a/src/inet/linklayer/ieee80211/mac/recipient/RecipientAckPolicy.cc b/src/inet/linklayer/ieee80211/mac/recipient/RecipientAckPolicy.cc
index af8077331bb..59e0e201c7f 100644
--- a/src/inet/linklayer/ieee80211/mac/recipient/RecipientAckPolicy.cc
+++ b/src/inet/linklayer/ieee80211/mac/recipient/RecipientAckPolicy.cc
@@ -6,6 +6,7 @@
 
 
 #include "inet/linklayer/ieee80211/mac/recipient/RecipientAckPolicy.h"
+#include "inet/linklayer/ieee80211/mac/Ieee80211Duration.h"
 
 #include "inet/common/ModuleAccess.h"
 
@@ -53,7 +54,7 @@ bool RecipientAckPolicy::isAckNeeded(const Ptr<const Ieee80211DataOrMgmtHeader>&
 simtime_t RecipientAckPolicy::computeAckDurationField(Packet *packet, const Ptr<const Ieee80211DataOrMgmtHeader>& header) const
 {
     if (header->getMoreFragments()) {
-        auto duration = header->getDurationField() - modeSet->getSifsTime() - computeAckDuration(packet, header);
+        auto duration = getIeee80211OrdinaryDuration(header->getDurationField()) - modeSet->getSifsTime() - computeAckDuration(packet, header);
         duration = ceil(duration, SimTime(1, SIMTIME_US));
         if (duration < 0)
             EV_WARN << "ACK duration field would be negative, returning 0 instead.\n";
diff --git a/src/inet/linklayer/ieee80211/mac/recipient/RecipientAckProcedure.cc b/src/inet/linklayer/ieee80211/mac/recipient/RecipientAckProcedure.cc
index 064934a2c1c..fc4975eb49e 100644
--- a/src/inet/linklayer/ieee80211/mac/recipient/RecipientAckProcedure.cc
+++ b/src/inet/linklayer/ieee80211/mac/recipient/RecipientAckProcedure.cc
@@ -5,6 +5,7 @@
 //
 
 
+#include "inet/linklayer/ieee80211/mac/Ieee80211Duration.h"
 #include "inet/linklayer/ieee80211/mac/recipient/RecipientAckProcedure.h"
 
 namespace inet {
@@ -18,6 +19,7 @@ void RecipientAckProcedure::processReceivedFrame(Packet *packet, const Ptr<const
     if (ackPolicy->isAckNeeded(dataOrMgmtHeader)) {
         auto ackFrame = buildAck(dataOrMgmtHeader);
         auto duration = ackPolicy->computeAckDurationField(packet, dataOrMgmtHeader);
+        duration = normalizeIeee80211Duration(duration);
         ackFrame->setDurationField(duration);
         auto ackPacket = new Packet("WlanAck", ackFrame);
         EV_DEBUG << "Duration for " << ackFrame->getName() << " is set to " << duration << " s.\n";
diff --git a/src/inet/linklayer/ieee80211/mac/recipient/RecipientQosAckPolicy.cc b/src/inet/linklayer/ieee80211/mac/recipient/RecipientQosAckPolicy.cc
index 29f793f0110..3a80fb3fa42 100644
--- a/src/inet/linklayer/ieee80211/mac/recipient/RecipientQosAckPolicy.cc
+++ b/src/inet/linklayer/ieee80211/mac/recipient/RecipientQosAckPolicy.cc
@@ -6,6 +6,7 @@
 
 
 #include "inet/linklayer/ieee80211/mac/recipient/RecipientQosAckPolicy.h"
+#include "inet/linklayer/ieee80211/mac/Ieee80211Duration.h"
 
 #include "inet/common/ModuleAccess.h"
 
@@ -78,7 +79,7 @@ bool RecipientQosAckPolicy::isBlockAckNeeded(const Ptr<const Ieee80211BlockAckRe
 //
 simtime_t RecipientQosAckPolicy::computeAckDurationField(Packet *packet, const Ptr<const Ieee80211DataOrMgmtHeader>& header) const
 {
-    simtime_t duration = header->getDurationField() - modeSet->getSifsTime() - computeAckDuration(packet, header);
+    simtime_t duration = getIeee80211OrdinaryDuration(header->getDurationField()) - modeSet->getSifsTime() - computeAckDuration(packet, header);
     return duration < 0 ? 0 : duration;
 }
 
@@ -91,9 +92,10 @@ simtime_t RecipientQosAckPolicy::computeAckDurationField(Packet *packet, const P
 //
 simtime_t RecipientQosAckPolicy::computeBasicBlockAckDurationField(Packet *packet, const Ptr<const Ieee80211BasicBlockAckReq>& basicBlockAckReq) const
 {
-    return basicBlockAckReq->getDurationField() - modeSet->getSifsTime() - computeBasicBlockAckDuration(packet, basicBlockAckReq);
+    simtime_t duration = getIeee80211OrdinaryDuration(basicBlockAckReq->getDurationField()) - modeSet->getSifsTime() - computeBasicBlockAckDuration(packet, basicBlockAckReq);
+    // IEEE Std 802.11-2024, 9.2.5.1: a negative calculated Duration/ID is inserted as zero.
+    return duration < 0 ? 0 : duration;
 }
 
 } /* namespace ieee80211 */
 } /* namespace inet */
-
diff --git a/tests/unit/Ieee80211BlockAckDuration_1.test b/tests/unit/Ieee80211BlockAckDuration_1.test
new file mode 100644
index 00000000000..cfddc72de71
--- /dev/null
+++ b/tests/unit/Ieee80211BlockAckDuration_1.test
@@ -0,0 +1,50 @@
+%description:
+A Basic BlockAck response must clamp a negative calculated Duration to zero
+before it reaches the model header or serializer (IEEE 802.11-2024, 9.2.5.1).
+
+%includes:
+#include "inet/linklayer/ieee80211/mac/recipient/RecipientQosAckPolicy.h"
+using namespace inet;
+using namespace inet::ieee80211;
+using namespace inet::physicallayer;
+
+%global:
+class FixedBlockAckRate : public IQosRateSelection
+{
+  public:
+    const IIeee80211Mode *mode = Ieee80211ModeSet::getModeSet("a")->getMode(Mbps(24));
+    virtual const IIeee80211Mode *computeResponseBlockAckFrameMode(Packet *, const Ptr<const Ieee80211BlockAckReq>&) override { return mode; }
+    virtual const IIeee80211Mode *computeResponseCtsFrameMode(Packet *, const Ptr<const Ieee80211RtsFrame>&) override { throw cRuntimeError("unexpected CTS lookup"); }
+    virtual const IIeee80211Mode *computeResponseAckFrameMode(Packet *, const Ptr<const Ieee80211DataOrMgmtHeader>&) override { throw cRuntimeError("unexpected ACK lookup"); }
+    virtual const IIeee80211Mode *computeMode(Packet *, const Ptr<const Ieee80211MacHeader>&, TxopProcedure *) override { throw cRuntimeError("unexpected data lookup"); }
+};
+class BlockAckDurationPolicy : public RecipientQosAckPolicy
+{
+  public:
+    void configure(IQosRateSelection *selection) {
+        rateSelection = selection;
+        modeSet = const_cast<Ieee80211ModeSet *>(Ieee80211ModeSet::getModeSet("a"));
+    }
+};
+
+%activity:
+FixedBlockAckRate rate;
+BlockAckDurationPolicy policy;
+policy.configure(&rate);
+Packet packet("BAR");
+const auto elapsed = Ieee80211ModeSet::getModeSet("a")->getSifsTime() + rate.mode->getDuration(LENGTH_BASIC_BLOCKACK);
+for (auto duration : {SIMTIME_ZERO, elapsed - SimTime(1, SIMTIME_US), elapsed, elapsed + SimTime(37, SIMTIME_US)}) {
+    auto bar = makeShared<Ieee80211BasicBlockAckReq>();
+    bar->setDurationField(duration);
+    auto actual = policy.computeBasicBlockAckDurationField(&packet, bar);
+    ASSERT(actual == (duration <= elapsed ? SIMTIME_ZERO : SimTime(37, SIMTIME_US)));
+}
+for (int special : {32768, 65535}) {
+    auto bar = makeShared<Ieee80211BasicBlockAckReq>();
+    bar->setDurationField(SimTime(special, SIMTIME_US));
+    ASSERT(policy.computeBasicBlockAckDurationField(&packet, bar) == SIMTIME_ZERO);
+}
+EV << "BlockAck duration is zero for insufficient reservations and preserves positive residuals.\n";
+
+%contains: stdout
+BlockAck duration is zero for insufficient reservations and preserves positive residuals.
diff --git a/tests/unit/Ieee80211DurationRounding_1.test b/tests/unit/Ieee80211DurationRounding_1.test
new file mode 100644
index 00000000000..2761a19b91b
--- /dev/null
+++ b/tests/unit/Ieee80211DurationRounding_1.test
@@ -0,0 +1,86 @@
+%description:
+Ordinary Duration/ID fields round fractional microseconds upward in every
+supported MAC header family (IEEE 802.11-2024, 9.2.5.1).
+
+%includes:
+#include "inet/common/packet/Packet.h"
+#include "inet/common/packet/chunk/BytesChunk.h"
+#include "inet/linklayer/ieee80211/mac/Ieee80211Frame_m.h"
+#include "inet/linklayer/ieee80211/mac/Ieee80211Duration.h"
+#include "inet/linklayer/ieee80211/mac/Rx.h"
+using namespace inet;
+using namespace inet::ieee80211;
+
+%global:
+class TestRx : public Rx {
+  public:
+    int updates = 0;
+    virtual bool isFcsOk(Packet *) const override { return true; }
+  protected:
+    virtual void setOrExtendNav(simtime_t) override { updates++; }
+};
+static Ptr<Ieee80211MacHeader> frame(int family)
+{
+    switch (family) {
+        case 0: return makeShared<Ieee80211DataHeader>();
+        case 1: {
+            auto header = makeShared<Ieee80211MgmtHeader>();
+            header->setType(ST_AUTHENTICATION);
+            return header;
+        }
+        case 2: return makeShared<Ieee80211RtsFrame>();
+        case 3: return makeShared<Ieee80211CtsFrame>();
+        case 4: return makeShared<Ieee80211AckFrame>();
+        case 5: return makeShared<Ieee80211BasicBlockAckReq>();
+        default: {
+            auto header = makeShared<Ieee80211BasicBlockAck>();
+            for (int i = 0; i < 64; i++)
+                for (int bit = 0; bit < 16; bit++)
+                    header->getBlockAckBitmapForUpdate(i).setBit(bit, false);
+            return header;
+        }
+    }
+}
+
+%activity:
+ASSERT(normalizeIeee80211Duration(SimTime(-1, SIMTIME_US)) == SIMTIME_ZERO);
+ASSERT(normalizeIeee80211Duration(SimTime(44800, SIMTIME_NS)) == SimTime(45, SIMTIME_US));
+ASSERT(normalizeIeee80211Duration(SimTime(32766800, SIMTIME_NS)) == SimTime(32767, SIMTIME_US));
+for (auto invalid : {SimTime(-1, SIMTIME_US), SimTime(32767100, SIMTIME_NS)}) {
+    bool rejected = false;
+    try { encodeIeee80211Duration(invalid); }
+    catch (const cRuntimeError&) { rejected = true; }
+    ASSERT(rejected);
+}
+for (int family = 0; family < 7; family++) {
+    for (int nanoseconds : {0, 1, 44000, 44800, 32766800}) {
+        auto header = frame(family);
+        if (auto data = dynamicPtrCast<Ieee80211DataOrMgmtHeader>(header))
+            data->setSequenceNumber(SequenceNumberCyclic(0));
+        if (auto bar = dynamicPtrCast<Ieee80211BasicBlockAckReq>(header))
+            bar->setStartingSequenceNumber(SequenceNumberCyclic(0));
+        if (auto ba = dynamicPtrCast<Ieee80211BasicBlockAck>(header))
+            ba->setStartingSequenceNumber(SequenceNumberCyclic(0));
+        header->setDurationField(SimTime(nanoseconds, SIMTIME_NS));
+        Packet packet("duration", header);
+        const auto bytes = packet.peekAllAsBytes()->getBytes();
+        ASSERT(bytes.size() >= 4);
+        int encoded = bytes[2] | (bytes[3] << 8);
+        ASSERT(encoded == (nanoseconds + 999) / 1000);
+    }
+}
+TestRx rx;
+for (int duration : {-1, 0, 32767, 32768, 65535}) {
+    auto header = makeShared<Ieee80211DataHeader>();
+    header->setReceiverAddress(MacAddress("02:00:00:00:00:12"));
+    header->setDurationField(SimTime(duration, SIMTIME_US));
+    auto packet = new Packet("nav", header);
+    int before = rx.updates;
+    ASSERT(rx.lowerFrameReceived(packet));
+    ASSERT(rx.updates - before == (duration >= 0 && duration <= 32767 ? 1 : 0));
+    delete packet;
+}
+EV << "All seven ordinary MAC Duration fields round upward.\n";
+
+%contains: stdout
+All seven ordinary MAC Duration fields round upward.
diff --git a/tests/unit/Ieee80211MsduAggregation_1.test b/tests/unit/Ieee80211MsduAggregation_1.test
index c6b142c9e29..7c78c00971b 100644
--- a/tests/unit/Ieee80211MsduAggregation_1.test
+++ b/tests/unit/Ieee80211MsduAggregation_1.test
@@ -67,6 +67,8 @@ for (bool toDS : {false, true}) {
         // OriginatorQosMacDataService assigns the sequence after aggregation, before transmission.
         auto sequencedHeader = aggregate->removeAtFront<Ieee80211DataHeader>();
         sequenceNumbers.assignSequenceNumber(sequencedHeader);
+        // The MAC assigns Duration before a frame is serialized for transmission.
+        sequencedHeader->setDurationField(SIMTIME_ZERO);
         aggregate->insertAtFront(sequencedHeader);
         auto outer = aggregate->peekAtFront<Ieee80211DataHeader>();
         ASSERT(outer->getReceiverAddress() == ra);
diff --git a/tests/unit/Ieee80211OnWireBitCompliance_1.test b/tests/unit/Ieee80211OnWireBitCompliance_1.test
index afebe6f9f27..33742bd38ec 100644
--- a/tests/unit/Ieee80211OnWireBitCompliance_1.test
+++ b/tests/unit/Ieee80211OnWireBitCompliance_1.test
@@ -21,6 +21,7 @@ for (int ds = 0; ds < 4; ds++) {
     for (int policy = 0; policy < 4; policy++) {
         auto header = makeShared<Ieee80211DataHeader>();
         header->setType(ST_DATA_WITH_QOS);
+        header->setDurationField(SIMTIME_ZERO);
         header->setSequenceNumber(SequenceNumberCyclic(0));
         header->setToDS(ds & 1);
         header->setFromDS(ds & 2);
diff --git a/tests/unit/Ieee80211ResponseDuration_1.test b/tests/unit/Ieee80211ResponseDuration_1.test
new file mode 100644
index 00000000000..3d1225908e8
--- /dev/null
+++ b/tests/unit/Ieee80211ResponseDuration_1.test
@@ -0,0 +1,60 @@
+%description:
+Reserved/special Duration/ID encodings do not become ordinary ACK or CTS
+reservations; valid ordinary durations preserve their residual airtime.
+
+%includes:
+#include "inet/linklayer/ieee80211/mac/recipient/CtsPolicy.h"
+#include "inet/linklayer/ieee80211/mac/rateselection/RateSelection.h"
+#include "inet/linklayer/ieee80211/mac/rateselection/QosRateSelection.h"
+#include "inet/linklayer/ieee80211/mac/recipient/QosCtsPolicy.h"
+#include "inet/linklayer/ieee80211/mac/recipient/RecipientAckPolicy.h"
+#include "inet/linklayer/ieee80211/mac/recipient/RecipientQosAckPolicy.h"
+using namespace inet;
+using namespace inet::ieee80211;
+using namespace inet::physicallayer;
+
+%global:
+template<typename T> class TestCts : public T {
+  public:
+    TestCts() { this->modeSet = const_cast<Ieee80211ModeSet *>(Ieee80211ModeSet::getModeSet("a")); }
+  protected:
+    virtual simtime_t computeCtsDuration(Packet *, const Ptr<const Ieee80211RtsFrame>&) const override { return SimTime(10, SIMTIME_US); }
+};
+template<typename T> class FixedAckRate : public T {
+  public:
+    virtual const IIeee80211Mode *computeResponseAckFrameMode(Packet *, const Ptr<const Ieee80211DataOrMgmtHeader>&) override {
+        return Ieee80211ModeSet::getModeSet("a")->getMode(Mbps(24));
+    }
+};
+template<typename T, typename Rate> class TestAck : public T {
+  protected:
+    FixedAckRate<Rate> rate;
+  public:
+    TestAck() {
+        this->modeSet = const_cast<Ieee80211ModeSet *>(Ieee80211ModeSet::getModeSet("a"));
+        this->rateSelection = &rate;
+    }
+};
+
+%activity:
+TestCts<CtsPolicy> dcfCts;
+TestCts<QosCtsPolicy> hcfCts;
+TestAck<RecipientAckPolicy, RateSelection> dcfAck;
+TestAck<RecipientQosAckPolicy, QosRateSelection> hcfAck;
+Packet packet("request");
+for (int duration : {-1, 0, 200, 32768, 65535}) {
+    auto rts = makeShared<Ieee80211RtsFrame>();
+    rts->setDurationField(SimTime(duration, SIMTIME_US));
+    auto data = makeShared<Ieee80211DataHeader>();
+    data->setMoreFragments(true);
+    data->setDurationField(SimTime(duration, SIMTIME_US));
+    auto expected = duration == 200 ? SimTime(174, SIMTIME_US) : SIMTIME_ZERO;
+    ASSERT(dcfCts.computeCtsDurationField(&packet, rts) == expected);
+    ASSERT(hcfCts.computeCtsDurationField(&packet, rts) == expected);
+    ASSERT(dcfAck.computeAckDurationField(&packet, data) == (duration == 200 ? SimTime(156, SIMTIME_US) : SIMTIME_ZERO));
+    ASSERT(hcfAck.computeAckDurationField(&packet, data) == (duration == 200 ? SimTime(156, SIMTIME_US) : SIMTIME_ZERO));
+}
+EV << "ACK and CTS policies ignore non-duration encodings.\n";
+
+%contains: stdout
+ACK and CTS policies ignore non-duration encodings.