diff --git a/quic/core/crypto/transport_parameters.cc b/quic/core/crypto/transport_parameters.cc
index e5df9fe..247f407 100644
--- a/quic/core/crypto/transport_parameters.cc
+++ b/quic/core/crypto/transport_parameters.cc
@@ -40,6 +40,7 @@
   kMaxAckDelay = 0xb,
   kDisableMigration = 0xc,
   kPreferredAddress = 0xd,
+  kActiveConnectionIdLimit = 0xe,
 
   kGoogleQuicParam = 18257,  // Used for non-standard Google-specific params.
   kGoogleQuicVersion =
@@ -90,6 +91,8 @@
       return "disable_migration";
     case TransportParameters::kPreferredAddress:
       return "preferred_address";
+    case TransportParameters::kActiveConnectionIdLimit:
+      return "active_connection_id_limit";
     case TransportParameters::kGoogleQuicParam:
       return "google";
     case TransportParameters::kGoogleQuicVersion:
@@ -273,6 +276,7 @@
     rv += " " + TransportParameterIdToString(kPreferredAddress) + " " +
           preferred_address->ToString();
   }
+  rv += active_connection_id_limit.ToString(/*for_use_in_list=*/true);
   if (google_quic_params) {
     rv += " " + TransportParameterIdToString(kGoogleQuicParam);
   }
@@ -302,7 +306,8 @@
                     kDefaultMaxAckDelayTransportParam,
                     0,
                     kMaxMaxAckDelayTransportParam),
-      disable_migration(false)
+      disable_migration(false),
+      active_connection_id_limit(kActiveConnectionIdLimit)
 // Important note: any new transport parameters must be added
 // to TransportParameters::AreValid, SerializeTransportParameters and
 // ParseTransportParameters.
@@ -350,7 +355,8 @@
                   initial_max_stream_data_uni.IsValid() &&
                   initial_max_streams_bidi.IsValid() &&
                   initial_max_streams_uni.IsValid() &&
-                  ack_delay_exponent.IsValid() && max_ack_delay.IsValid();
+                  ack_delay_exponent.IsValid() && max_ack_delay.IsValid() &&
+                  active_connection_id_limit.IsValid();
   if (!ok) {
     QUIC_DLOG(ERROR) << "Invalid transport parameters " << *this;
   }
@@ -431,7 +437,8 @@
       !in.initial_max_streams_bidi.WriteToCbb(&params) ||
       !in.initial_max_streams_uni.WriteToCbb(&params) ||
       !in.ack_delay_exponent.WriteToCbb(&params) ||
-      !in.max_ack_delay.WriteToCbb(&params)) {
+      !in.max_ack_delay.WriteToCbb(&params) ||
+      !in.active_connection_id_limit.WriteToCbb(&params)) {
     QUIC_BUG << "Failed to write integers for " << in;
     return false;
   }
@@ -692,6 +699,9 @@
             QuicMakeUnique<TransportParameters::PreferredAddress>(
                 preferred_address);
       } break;
+      case TransportParameters::kActiveConnectionIdLimit:
+        parse_success = out->active_connection_id_limit.ReadFromCbs(&value);
+        break;
       case TransportParameters::kGoogleQuicParam: {
         if (out->google_quic_params) {
           QUIC_DLOG(ERROR) << "Received a second Google parameter";
diff --git a/quic/core/crypto/transport_parameters.h b/quic/core/crypto/transport_parameters.h
index 27b5fe7..368a7bf 100644
--- a/quic/core/crypto/transport_parameters.h
+++ b/quic/core/crypto/transport_parameters.h
@@ -161,6 +161,10 @@
   // Used to effect a change in server address at the end of the handshake.
   std::unique_ptr<PreferredAddress> preferred_address;
 
+  // Maximum number of connection IDs from the peer that an endpoint is willing
+  // to store.
+  IntegerParameter active_connection_id_limit;
+
   // Transport parameters used by Google QUIC but not IETF QUIC. This is
   // serialized into a TransportParameter struct with a TransportParameterId of
   // kGoogleQuicParamId.
diff --git a/quic/core/crypto/transport_parameters_test.cc b/quic/core/crypto/transport_parameters_test.cc
index 7776af1..3f7e339 100644
--- a/quic/core/crypto/transport_parameters_test.cc
+++ b/quic/core/crypto/transport_parameters_test.cc
@@ -36,6 +36,7 @@
 const uint64_t kFakeAckDelayExponent = 10;
 const uint64_t kFakeMaxAckDelay = 51;
 const bool kFakeDisableMigration = true;
+const uint64_t kFakeActiveConnectionIdLimit = 52;
 const QuicConnectionId kFakePreferredConnectionId = TestConnectionId(0xBEEF);
 const uint8_t kFakePreferredStatelessResetTokenData[16] = {
     0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
@@ -96,6 +97,8 @@
   orig_params.ack_delay_exponent.set_value(kFakeAckDelayExponent);
   orig_params.max_ack_delay.set_value(kFakeMaxAckDelay);
   orig_params.disable_migration = kFakeDisableMigration;
+  orig_params.active_connection_id_limit.set_value(
+      kFakeActiveConnectionIdLimit);
 
   std::vector<uint8_t> serialized;
   ASSERT_TRUE(SerializeTransportParameters(orig_params, &serialized));
@@ -126,6 +129,8 @@
   EXPECT_EQ(kFakeAckDelayExponent, new_params.ack_delay_exponent.value());
   EXPECT_EQ(kFakeMaxAckDelay, new_params.max_ack_delay.value());
   EXPECT_EQ(kFakeDisableMigration, new_params.disable_migration);
+  EXPECT_EQ(kFakeActiveConnectionIdLimit,
+            new_params.active_connection_id_limit.value());
 }
 
 TEST_F(TransportParametersTest, RoundTripServer) {
@@ -151,6 +156,8 @@
   orig_params.max_ack_delay.set_value(kFakeMaxAckDelay);
   orig_params.disable_migration = kFakeDisableMigration;
   orig_params.preferred_address = CreateFakePreferredAddress();
+  orig_params.active_connection_id_limit.set_value(
+      kFakeActiveConnectionIdLimit);
 
   std::vector<uint8_t> serialized;
   ASSERT_TRUE(SerializeTransportParameters(orig_params, &serialized));
@@ -192,6 +199,8 @@
             new_params.preferred_address->connection_id);
   EXPECT_EQ(kFakePreferredStatelessResetToken,
             new_params.preferred_address->stateless_reset_token);
+  EXPECT_EQ(kFakeActiveConnectionIdLimit,
+            new_params.active_connection_id_limit.value());
 }
 
 TEST_F(TransportParametersTest, IsValid) {
@@ -252,7 +261,7 @@
 TEST_F(TransportParametersTest, ParseClientParams) {
   // clang-format off
   const uint8_t kClientParams[] = {
-      0x00, 0x44,              // length of the parameters array that follows
+      0x00, 0x49,              // length of the parameters array that follows
       // idle_timeout
       0x00, 0x01,  // parameter id
       0x00, 0x02,  // length
@@ -296,6 +305,10 @@
       // disable_migration
       0x00, 0x0c,  // parameter id
       0x00, 0x00,  // length
+      // active_connection_id_limit
+      0x00, 0x0e,  // parameter id
+      0x00, 0x01,  // length
+      0x34,  // value
       // Google version extension
       0x47, 0x52,  // parameter id
       0x00, 0x04,  // length
@@ -330,6 +343,8 @@
   EXPECT_EQ(kFakeAckDelayExponent, new_params.ack_delay_exponent.value());
   EXPECT_EQ(kFakeMaxAckDelay, new_params.max_ack_delay.value());
   EXPECT_EQ(kFakeDisableMigration, new_params.disable_migration);
+  EXPECT_EQ(kFakeActiveConnectionIdLimit,
+            new_params.active_connection_id_limit.value());
 }
 
 TEST_F(TransportParametersTest, ParseClientParamsFailsWithStatelessResetToken) {
@@ -418,7 +433,7 @@
 TEST_F(TransportParametersTest, ParseServerParams) {
   // clang-format off
   const uint8_t kServerParams[] = {
-      0x00, 0xa2,  // length of parameters array that follows
+      0x00, 0xa7,  // length of parameters array that follows
       // original_connection_id
       0x00, 0x00,  // parameter id
       0x00, 0x08,  // length
@@ -483,6 +498,10 @@
       0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xBE, 0xEF,  // connection ID
       0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,  // stateless reset token
       0x88, 0x89, 0x8A, 0x8B, 0x8C, 0x8D, 0x8E, 0x8F,
+      // active_connection_id_limit
+      0x00, 0x0e,  // parameter id
+      0x00, 0x01,  // length
+      0x34,  // value
       // Google version extension
       0x47, 0x52,  // parameter id
       0x00, 0x0d,  // length
@@ -531,6 +550,8 @@
             new_params.preferred_address->connection_id);
   EXPECT_EQ(kFakePreferredStatelessResetToken,
             new_params.preferred_address->stateless_reset_token);
+  EXPECT_EQ(kFakeActiveConnectionIdLimit,
+            new_params.active_connection_id_limit.value());
 }
 
 TEST_F(TransportParametersTest, ParseServerParametersRepeated) {