diff --git a/framework-t/src/android/app/usage/NetworkStatsManager.java b/framework-t/src/android/app/usage/NetworkStatsManager.java
index 903983d..8d93354 100644
--- a/framework-t/src/android/app/usage/NetworkStatsManager.java
+++ b/framework-t/src/android/app/usage/NetworkStatsManager.java
@@ -125,6 +125,19 @@
     private final Context mContext;
     private final INetworkStatsService mService;
 
+    /**
+     * Type constants for reading different types of Data Usage.
+     * @hide
+     */
+    // @SystemApi(client = MODULE_LIBRARIES)
+    public static final String PREFIX_DEV = "dev";
+    /** @hide */
+    public static final String PREFIX_XT = "xt";
+    /** @hide */
+    public static final String PREFIX_UID = "uid";
+    /** @hide */
+    public static final String PREFIX_UID_TAG = "uid_tag";
+
     /** @hide */
     public static final int FLAG_POLL_ON_OPEN = 1 << 0;
     /** @hide */
diff --git a/framework-t/src/android/net/NetworkIdentity.java b/framework-t/src/android/net/NetworkIdentity.java
index 04d1d68..097b9be 100644
--- a/framework-t/src/android/net/NetworkIdentity.java
+++ b/framework-t/src/android/net/NetworkIdentity.java
@@ -17,12 +17,15 @@
 package android.net;
 
 import static android.net.ConnectivityManager.TYPE_WIFI;
+import static android.net.NetworkTemplate.NETWORK_TYPE_ALL;
 
+import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.content.Context;
 import android.net.wifi.WifiInfo;
 import android.service.NetworkIdentityProto;
-import android.telephony.Annotation.NetworkType;
+import android.telephony.Annotation;
+import android.telephony.TelephonyManager;
 import android.util.proto.ProtoOutputStream;
 
 import com.android.net.module.util.NetworkCapabilitiesUtils;
@@ -37,9 +40,13 @@
  *
  * @hide
  */
+// @SystemApi(client = MODULE_LIBRARIES)
 public class NetworkIdentity implements Comparable<NetworkIdentity> {
     private static final String TAG = "NetworkIdentity";
 
+    /** @hide */
+    // TODO: Remove this after migrating all callers to use
+    //  {@link NetworkTemplate#NETWORK_TYPE_ALL} instead.
     public static final int SUBTYPE_COMBINED = -1;
 
     /**
@@ -59,21 +66,22 @@
     public static final int OEM_PRIVATE = 0x2;
 
     final int mType;
-    final int mSubType;
+    final int mRatType;
     final String mSubscriberId;
-    final String mNetworkId;
+    final String mWifiNetworkKey;
     final boolean mRoaming;
     final boolean mMetered;
     final boolean mDefaultNetwork;
     final int mOemManaged;
 
+    /** @hide */
     public NetworkIdentity(
-            int type, int subType, String subscriberId, String networkId, boolean roaming,
-            boolean metered, boolean defaultNetwork, int oemManaged) {
+            int type, int ratType, @Nullable String subscriberId, @Nullable String wifiNetworkKey,
+            boolean roaming, boolean metered, boolean defaultNetwork, int oemManaged) {
         mType = type;
-        mSubType = subType;
+        mRatType = ratType;
         mSubscriberId = subscriberId;
-        mNetworkId = networkId;
+        mWifiNetworkKey = wifiNetworkKey;
         mRoaming = roaming;
         mMetered = metered;
         mDefaultNetwork = defaultNetwork;
@@ -82,7 +90,7 @@
 
     @Override
     public int hashCode() {
-        return Objects.hash(mType, mSubType, mSubscriberId, mNetworkId, mRoaming, mMetered,
+        return Objects.hash(mType, mRatType, mSubscriberId, mWifiNetworkKey, mRoaming, mMetered,
                 mDefaultNetwork, mOemManaged);
     }
 
@@ -90,9 +98,9 @@
     public boolean equals(@Nullable Object obj) {
         if (obj instanceof NetworkIdentity) {
             final NetworkIdentity ident = (NetworkIdentity) obj;
-            return mType == ident.mType && mSubType == ident.mSubType && mRoaming == ident.mRoaming
+            return mType == ident.mType && mRatType == ident.mRatType && mRoaming == ident.mRoaming
                     && Objects.equals(mSubscriberId, ident.mSubscriberId)
-                    && Objects.equals(mNetworkId, ident.mNetworkId)
+                    && Objects.equals(mWifiNetworkKey, ident.mWifiNetworkKey)
                     && mMetered == ident.mMetered
                     && mDefaultNetwork == ident.mDefaultNetwork
                     && mOemManaged == ident.mOemManaged;
@@ -104,18 +112,18 @@
     public String toString() {
         final StringBuilder builder = new StringBuilder("{");
         builder.append("type=").append(mType);
-        builder.append(", subType=");
-        if (mSubType == SUBTYPE_COMBINED) {
+        builder.append(", ratType=");
+        if (mRatType == NETWORK_TYPE_ALL) {
             builder.append("COMBINED");
         } else {
-            builder.append(mSubType);
+            builder.append(mRatType);
         }
         if (mSubscriberId != null) {
             builder.append(", subscriberId=")
                     .append(NetworkIdentityUtils.scrubSubscriberId(mSubscriberId));
         }
-        if (mNetworkId != null) {
-            builder.append(", networkId=").append(mNetworkId);
+        if (mWifiNetworkKey != null) {
+            builder.append(", wifiNetworkKey=").append(mWifiNetworkKey);
         }
         if (mRoaming) {
             builder.append(", ROAMING");
@@ -153,12 +161,13 @@
         }
     }
 
+    /** @hide */
     public void dumpDebug(ProtoOutputStream proto, long tag) {
         final long start = proto.start(tag);
 
         proto.write(NetworkIdentityProto.TYPE, mType);
 
-        // Not dumping mSubType, subtypes are no longer supported.
+        // TODO: dump mRatType as well.
 
         proto.write(NetworkIdentityProto.ROAMING, mRoaming);
         proto.write(NetworkIdentityProto.METERED, mMetered);
@@ -168,50 +177,68 @@
         proto.end(start);
     }
 
+    /** @hide */
     public int getType() {
         return mType;
     }
 
-    public int getSubType() {
-        return mSubType;
+    /** @hide */
+    public int getRatType() {
+        return mRatType;
     }
 
+    /** @hide */
     public String getSubscriberId() {
         return mSubscriberId;
     }
 
-    public String getNetworkId() {
-        return mNetworkId;
+    /** @hide */
+    public String getWifiNetworkKey() {
+        return mWifiNetworkKey;
     }
 
+    /** @hide */
     public boolean getRoaming() {
         return mRoaming;
     }
 
+    /** @hide */
     public boolean getMetered() {
         return mMetered;
     }
 
+    /** @hide */
     public boolean getDefaultNetwork() {
         return mDefaultNetwork;
     }
 
+    /** @hide */
     public int getOemManaged() {
         return mOemManaged;
     }
 
     /**
-     * Build a {@link NetworkIdentity} from the given {@link NetworkStateSnapshot} and
-     * {@code subType}, assuming that any mobile networks are using the current IMSI.
-     * The subType if applicable, should be set as one of the TelephonyManager.NETWORK_TYPE_*
-     * constants, or {@link android.telephony.TelephonyManager#NETWORK_TYPE_UNKNOWN} if not.
+     * Assemble a {@link NetworkIdentity} from the passed arguments.
+     *
+     * This methods builds an identity based on the capabilities of the network in the
+     * snapshot and other passed arguments. The identity is used as a key to record data usage.
+     *
+     * @param snapshot the snapshot of network state. See {@link NetworkStateSnapshot}.
+     * @param defaultNetwork whether the network is a default network.
+     * @param ratType the Radio Access Technology(RAT) type of the network. Or
+     *                {@link TelephonyManager#NETWORK_TYPE_UNKNOWN} if not applicable.
+     *                See {@code TelephonyManager.NETWORK_TYPE_*}.
+     * @hide
      */
+    // TODO: Remove this after all callers are migrated to use new Api.
+    @NonNull
     public static NetworkIdentity buildNetworkIdentity(Context context,
-            NetworkStateSnapshot snapshot, boolean defaultNetwork, @NetworkType int subType) {
+            @NonNull NetworkStateSnapshot snapshot,
+            boolean defaultNetwork, @Annotation.NetworkType int ratType) {
         final int legacyType = snapshot.getLegacyType();
 
         final String subscriberId = snapshot.getSubscriberId();
-        String networkId = null;
+        String wifiNetworkKey = null;
         boolean roaming = !snapshot.getNetworkCapabilities().hasCapability(
                 NetworkCapabilities.NET_CAPABILITY_NOT_ROAMING);
         boolean metered = !(snapshot.getNetworkCapabilities().hasCapability(
@@ -226,19 +253,19 @@
                     .getTransportInfo();
             if (transportInfo instanceof WifiInfo) {
                 final WifiInfo info = (WifiInfo) transportInfo;
-                networkId = info != null ? info.getCurrentNetworkKey() : null;
+                wifiNetworkKey = info != null ? info.getCurrentNetworkKey() : null;
             }
         }
 
-        return new NetworkIdentity(legacyType, subType, subscriberId, networkId, roaming, metered,
-                defaultNetwork, oemManaged);
+        return new NetworkIdentity(legacyType, ratType, subscriberId, wifiNetworkKey, roaming,
+                metered, defaultNetwork, oemManaged);
     }
 
     /**
      * Builds a bitfield of {@code NetworkIdentity.OEM_*} based on {@link NetworkCapabilities}.
      * @hide
      */
-    public static int getOemBitfield(NetworkCapabilities nc) {
+    public static int getOemBitfield(@NonNull NetworkCapabilities nc) {
         int oemManaged = OEM_NONE;
 
         if (nc.hasCapability(NetworkCapabilities.NET_CAPABILITY_OEM_PAID)) {
@@ -252,16 +279,17 @@
     }
 
     @Override
-    public int compareTo(NetworkIdentity another) {
+    public int compareTo(@NonNull NetworkIdentity another) {
+        Objects.requireNonNull(another);
         int res = Integer.compare(mType, another.mType);
         if (res == 0) {
-            res = Integer.compare(mSubType, another.mSubType);
+            res = Integer.compare(mRatType, another.mRatType);
         }
         if (res == 0 && mSubscriberId != null && another.mSubscriberId != null) {
             res = mSubscriberId.compareTo(another.mSubscriberId);
         }
-        if (res == 0 && mNetworkId != null && another.mNetworkId != null) {
-            res = mNetworkId.compareTo(another.mNetworkId);
+        if (res == 0 && mWifiNetworkKey != null && another.mWifiNetworkKey != null) {
+            res = mWifiNetworkKey.compareTo(another.mWifiNetworkKey);
         }
         if (res == 0) {
             res = Boolean.compare(mRoaming, another.mRoaming);
diff --git a/framework-t/src/android/net/NetworkIdentitySet.java b/framework-t/src/android/net/NetworkIdentitySet.java
index abbebef..c2d8ea1 100644
--- a/framework-t/src/android/net/NetworkIdentitySet.java
+++ b/framework-t/src/android/net/NetworkIdentitySet.java
@@ -18,6 +18,7 @@
 
 import static android.net.ConnectivityManager.TYPE_MOBILE;
 
+import android.annotation.NonNull;
 import android.service.NetworkIdentitySetProto;
 import android.util.proto.ProtoOutputStream;
 
@@ -25,6 +26,7 @@
 import java.io.DataOutput;
 import java.io.IOException;
 import java.util.HashSet;
+import java.util.Objects;
 
 /**
  * Identity of a {@code iface}, defined by the set of {@link NetworkIdentity}
@@ -32,6 +34,7 @@
  *
  * @hide
  */
+// @SystemApi(client = MODULE_LIBRARIES)
 public class NetworkIdentitySet extends HashSet<NetworkIdentity> implements
         Comparable<NetworkIdentitySet> {
     private static final int VERSION_INIT = 1;
@@ -41,9 +44,14 @@
     private static final int VERSION_ADD_DEFAULT_NETWORK = 5;
     private static final int VERSION_ADD_OEM_MANAGED_NETWORK = 6;
 
+    /**
+     * Construct a {@link NetworkIdentitySet} object.
+     */
     public NetworkIdentitySet() {
+        super();
     }
 
+    /** @hide */
     public NetworkIdentitySet(DataInput in) throws IOException {
         final int version = in.readInt();
         final int size = in.readInt();
@@ -52,7 +60,7 @@
                 final int ignored = in.readInt();
             }
             final int type = in.readInt();
-            final int subType = in.readInt();
+            final int ratType = in.readInt();
             final String subscriberId = readOptionalString(in);
             final String networkId;
             if (version >= VERSION_ADD_NETWORK_ID) {
@@ -91,22 +99,23 @@
                 oemNetCapabilities = NetworkIdentity.OEM_NONE;
             }
 
-            add(new NetworkIdentity(type, subType, subscriberId, networkId, roaming, metered,
+            add(new NetworkIdentity(type, ratType, subscriberId, networkId, roaming, metered,
                     defaultNetwork, oemNetCapabilities));
         }
     }
 
     /**
      * Method to serialize this object into a {@code DataOutput}.
+     * @hide
      */
     public void writeToStream(DataOutput out) throws IOException {
         out.writeInt(VERSION_ADD_OEM_MANAGED_NETWORK);
         out.writeInt(size());
         for (NetworkIdentity ident : this) {
             out.writeInt(ident.getType());
-            out.writeInt(ident.getSubType());
+            out.writeInt(ident.getRatType());
             writeOptionalString(out, ident.getSubscriberId());
-            writeOptionalString(out, ident.getNetworkId());
+            writeOptionalString(out, ident.getWifiNetworkKey());
             out.writeBoolean(ident.getRoaming());
             out.writeBoolean(ident.getMetered());
             out.writeBoolean(ident.getDefaultNetwork());
@@ -114,7 +123,10 @@
         }
     }
 
-    /** @return whether any {@link NetworkIdentity} in this set is considered metered. */
+    /**
+     * @return whether any {@link NetworkIdentity} in this set is considered metered.
+     * @hide
+     */
     public boolean isAnyMemberMetered() {
         if (isEmpty()) {
             return false;
@@ -127,7 +139,10 @@
         return false;
     }
 
-    /** @return whether any {@link NetworkIdentity} in this set is considered roaming. */
+    /**
+     * @return whether any {@link NetworkIdentity} in this set is considered roaming.
+     * @hide
+     */
     public boolean isAnyMemberRoaming() {
         if (isEmpty()) {
             return false;
@@ -140,8 +155,11 @@
         return false;
     }
 
-    /** @return whether any {@link NetworkIdentity} in this set is considered on the default
-            network. */
+    /**
+     * @return whether any {@link NetworkIdentity} in this set is considered on the default
+     *         network.
+     * @hide
+     */
     public boolean areAllMembersOnDefaultNetwork() {
         if (isEmpty()) {
             return true;
@@ -172,7 +190,8 @@
     }
 
     @Override
-    public int compareTo(NetworkIdentitySet another) {
+    public int compareTo(@NonNull NetworkIdentitySet another) {
+        Objects.requireNonNull(another);
         if (isEmpty()) return -1;
         if (another.isEmpty()) return 1;
 
@@ -183,6 +202,7 @@
 
     /**
      * Method to dump this object into proto debug file.
+     * @hide
      */
     public void dumpDebug(ProtoOutputStream proto, long tag) {
         final long start = proto.start(tag);
diff --git a/framework-t/src/android/net/NetworkStatsCollection.java b/framework-t/src/android/net/NetworkStatsCollection.java
index 9f9d73f..f169fed 100644
--- a/framework-t/src/android/net/NetworkStatsCollection.java
+++ b/framework-t/src/android/net/NetworkStatsCollection.java
@@ -32,6 +32,8 @@
 
 import static com.android.net.module.util.NetworkStatsUtils.multiplySafeByRational;
 
+import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.os.Binder;
 import android.service.NetworkStatsCollectionKeyProto;
 import android.service.NetworkStatsCollectionProto;
@@ -77,6 +79,7 @@
  *
  * @hide
  */
+// @SystemApi(client = MODULE_LIBRARIES)
 public class NetworkStatsCollection implements FileRotator.Reader, FileRotator.Writer {
     private static final String TAG = NetworkStatsCollection.class.getSimpleName();
     /** File header magic number: "ANET" */
@@ -100,15 +103,23 @@
     private long mTotalBytes;
     private boolean mDirty;
 
+    /**
+     * Construct a {@link NetworkStatsCollection} object.
+     *
+     * @param bucketDuration duration of the buckets in this object, in milliseconds.
+     * @hide
+     */
     public NetworkStatsCollection(long bucketDuration) {
         mBucketDuration = bucketDuration;
         reset();
     }
 
+    /** @hide */
     public void clear() {
         reset();
     }
 
+    /** @hide */
     public void reset() {
         mStats.clear();
         mStartMillis = Long.MAX_VALUE;
@@ -117,6 +128,7 @@
         mDirty = false;
     }
 
+    /** @hide */
     public long getStartMillis() {
         return mStartMillis;
     }
@@ -124,6 +136,7 @@
     /**
      * Return first atomic bucket in this collection, which is more conservative
      * than {@link #mStartMillis}.
+     * @hide
      */
     public long getFirstAtomicBucketMillis() {
         if (mStartMillis == Long.MAX_VALUE) {
@@ -133,26 +146,32 @@
         }
     }
 
+    /** @hide */
     public long getEndMillis() {
         return mEndMillis;
     }
 
+    /** @hide */
     public long getTotalBytes() {
         return mTotalBytes;
     }
 
+    /** @hide */
     public boolean isDirty() {
         return mDirty;
     }
 
+    /** @hide */
     public void clearDirty() {
         mDirty = false;
     }
 
+    /** @hide */
     public boolean isEmpty() {
         return mStartMillis == Long.MAX_VALUE && mEndMillis == Long.MIN_VALUE;
     }
 
+    /** @hide */
     @VisibleForTesting
     public long roundUp(long time) {
         if (time == Long.MIN_VALUE || time == Long.MAX_VALUE
@@ -168,6 +187,7 @@
         }
     }
 
+    /** @hide */
     @VisibleForTesting
     public long roundDown(long time) {
         if (time == Long.MIN_VALUE || time == Long.MAX_VALUE
@@ -182,10 +202,12 @@
         }
     }
 
+    /** @hide */
     public int[] getRelevantUids(@NetworkStatsAccess.Level int accessLevel) {
         return getRelevantUids(accessLevel, Binder.getCallingUid());
     }
 
+    /** @hide */
     public int[] getRelevantUids(@NetworkStatsAccess.Level int accessLevel,
                 final int callerUid) {
         final ArrayList<Integer> uids = new ArrayList<>();
@@ -206,6 +228,7 @@
     /**
      * Combine all {@link NetworkStatsHistory} in this collection which match
      * the requested parameters.
+     * @hide
      */
     public NetworkStatsHistory getHistory(NetworkTemplate template, SubscriptionPlan augmentPlan,
             int uid, int set, int tag, int fields, long start, long end,
@@ -331,6 +354,7 @@
      * @param end - end of the range, timestamp in milliseconds since the epoch.
      * @param accessLevel - caller access level.
      * @param callerUid - caller UID.
+     * @hide
      */
     public NetworkStats getSummary(NetworkTemplate template, long start, long end,
             @NetworkStatsAccess.Level int accessLevel, int callerUid) {
@@ -377,6 +401,7 @@
 
     /**
      * Record given {@link android.net.NetworkStats.Entry} into this collection.
+     * @hide
      */
     public void recordData(NetworkIdentitySet ident, int uid, int set, int tag, long start,
             long end, NetworkStats.Entry entry) {
@@ -387,8 +412,12 @@
 
     /**
      * Record given {@link NetworkStatsHistory} into this collection.
+     *
+     * @hide
      */
-    private void recordHistory(Key key, NetworkStatsHistory history) {
+    public void recordHistory(@NonNull Key key, @NonNull NetworkStatsHistory history) {
+        Objects.requireNonNull(key);
+        Objects.requireNonNull(history);
         if (history.size() == 0) return;
         noteRecordedHistory(history.getStart(), history.getEnd(), history.getTotalBytes());
 
@@ -403,8 +432,11 @@
     /**
      * Record all {@link NetworkStatsHistory} contained in the given collection
      * into this collection.
+     *
+     * @hide
      */
-    public void recordCollection(NetworkStatsCollection another) {
+    public void recordCollection(@NonNull NetworkStatsCollection another) {
+        Objects.requireNonNull(another);
         for (int i = 0; i < another.mStats.size(); i++) {
             final Key key = another.mStats.keyAt(i);
             final NetworkStatsHistory value = another.mStats.valueAt(i);
@@ -433,6 +465,7 @@
         }
     }
 
+    /** @hide */
     @Override
     public void read(InputStream in) throws IOException {
         read((DataInput) new DataInputStream(in));
@@ -472,6 +505,7 @@
         }
     }
 
+    /** @hide */
     @Override
     public void write(OutputStream out) throws IOException {
         write((DataOutput) new DataOutputStream(out));
@@ -514,6 +548,7 @@
      * See {@code NetworkStatsService#maybeUpgradeLegacyStatsLocked}.
      *
      * @deprecated
+     * @hide
      */
     @Deprecated
     public void readLegacyNetwork(File file) throws IOException {
@@ -559,6 +594,7 @@
      * See {@code NetworkStatsService#maybeUpgradeLegacyStatsLocked}.
      *
      * @deprecated
+     * @hide
      */
     @Deprecated
     public void readLegacyUid(File file, boolean onlyTags) throws IOException {
@@ -629,6 +665,7 @@
      * Remove any {@link NetworkStatsHistory} attributed to the requested UID,
      * moving any {@link NetworkStats#TAG_NONE} series to
      * {@link TrafficStats#UID_REMOVED}.
+     * @hide
      */
     public void removeUids(int[] uids) {
         final ArrayList<Key> knownKeys = new ArrayList<>();
@@ -669,6 +706,7 @@
         return keys;
     }
 
+    /** @hide */
     public void dump(IndentingPrintWriter pw) {
         for (Key key : getSortedKeys()) {
             pw.print("ident="); pw.print(key.ident.toString());
@@ -683,6 +721,7 @@
         }
     }
 
+    /** @hide */
     public void dumpDebug(ProtoOutputStream proto, long tag) {
         final long start = proto.start(tag);
 
@@ -706,6 +745,7 @@
         proto.end(start);
     }
 
+    /** @hide */
     public void dumpCheckin(PrintWriter pw, long start, long end) {
         dumpCheckin(pw, start, end, NetworkTemplate.buildTemplateMobileWildcard(), "cell");
         dumpCheckin(pw, start, end, NetworkTemplate.buildTemplateWifiWildcard(), "wifi");
@@ -768,16 +808,32 @@
         return false;
     }
 
-    private static class Key implements Comparable<Key> {
+    /**
+     * the identifier that associate with the {@link NetworkStatsHistory} object to identify
+     * a certain record in the {@link NetworkStatsCollection} object.
+     */
+    public static class Key implements Comparable<Key> {
+        /** @hide */
         public final NetworkIdentitySet ident;
+        /** @hide */
         public final int uid;
+        /** @hide */
         public final int set;
+        /** @hide */
         public final int tag;
 
         private final int mHashCode;
 
-        Key(NetworkIdentitySet ident, int uid, int set, int tag) {
-            this.ident = ident;
+        /**
+         * Construct a {@link Key} object.
+         *
+         * @param ident a Set of {@link NetworkIdentity} that associated with the record.
+         * @param uid Uid of the record.
+         * @param set Set of the record, see {@code NetworkStats#SET_*}.
+         * @param tag Tag of the record, see {@link TrafficStats#setThreadStatsTag(int)}.
+         */
+        public Key(@NonNull NetworkIdentitySet ident, int uid, int set, int tag) {
+            this.ident = Objects.requireNonNull(ident);
             this.uid = uid;
             this.set = set;
             this.tag = tag;
@@ -790,7 +846,7 @@
         }
 
         @Override
-        public boolean equals(Object obj) {
+        public boolean equals(@Nullable Object obj) {
             if (obj instanceof Key) {
                 final Key key = (Key) obj;
                 return uid == key.uid && set == key.set && tag == key.tag
@@ -800,7 +856,8 @@
         }
 
         @Override
-        public int compareTo(Key another) {
+        public int compareTo(@NonNull Key another) {
+            Objects.requireNonNull(another);
             int res = 0;
             if (ident != null && another.ident != null) {
                 res = ident.compareTo(another.ident);
diff --git a/framework-t/src/android/net/NetworkStatsHistory.java b/framework-t/src/android/net/NetworkStatsHistory.java
index 428bc6d..90054c6 100644
--- a/framework-t/src/android/net/NetworkStatsHistory.java
+++ b/framework-t/src/android/net/NetworkStatsHistory.java
@@ -30,6 +30,7 @@
 
 import static com.android.net.module.util.NetworkStatsUtils.multiplySafeByRational;
 
+import android.annotation.NonNull;
 import android.compat.annotation.UnsupportedAppUsage;
 import android.os.Build;
 import android.os.Parcel;
@@ -64,18 +65,25 @@
  *
  * @hide
  */
-public class NetworkStatsHistory implements Parcelable {
+// @SystemApi(client = MODULE_LIBRARIES)
+public final class NetworkStatsHistory implements Parcelable {
     private static final int VERSION_INIT = 1;
     private static final int VERSION_ADD_PACKETS = 2;
     private static final int VERSION_ADD_ACTIVE = 3;
 
+    /** @hide */
     public static final int FIELD_ACTIVE_TIME = 0x01;
+    /** @hide */
     public static final int FIELD_RX_BYTES = 0x02;
+    /** @hide */
     public static final int FIELD_RX_PACKETS = 0x04;
+    /** @hide */
     public static final int FIELD_TX_BYTES = 0x08;
+    /** @hide */
     public static final int FIELD_TX_PACKETS = 0x10;
+    /** @hide */
     public static final int FIELD_OPERATIONS = 0x20;
-
+    /** @hide */
     public static final int FIELD_ALL = 0xFFFFFFFF;
 
     private long bucketDuration;
@@ -108,15 +116,18 @@
         public long operations;
     }
 
+    /** @hide */
     @UnsupportedAppUsage
     public NetworkStatsHistory(long bucketDuration) {
         this(bucketDuration, 10, FIELD_ALL);
     }
 
+    /** @hide */
     public NetworkStatsHistory(long bucketDuration, int initialSize) {
         this(bucketDuration, initialSize, FIELD_ALL);
     }
 
+    /** @hide */
     public NetworkStatsHistory(long bucketDuration, int initialSize, int fields) {
         this.bucketDuration = bucketDuration;
         bucketStart = new long[initialSize];
@@ -130,11 +141,13 @@
         totalBytes = 0;
     }
 
+    /** @hide */
     public NetworkStatsHistory(NetworkStatsHistory existing, long bucketDuration) {
         this(bucketDuration, existing.estimateResizeBuckets(bucketDuration));
         recordEntireHistory(existing);
     }
 
+    /** @hide */
     @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.R, trackingBug = 170729553)
     public NetworkStatsHistory(Parcel in) {
         bucketDuration = in.readLong();
@@ -150,7 +163,7 @@
     }
 
     @Override
-    public void writeToParcel(Parcel out, int flags) {
+    public void writeToParcel(@NonNull Parcel out, int flags) {
         out.writeLong(bucketDuration);
         writeLongArray(out, bucketStart, bucketCount);
         writeLongArray(out, activeTime, bucketCount);
@@ -162,6 +175,7 @@
         out.writeLong(totalBytes);
     }
 
+    /** @hide */
     public NetworkStatsHistory(DataInput in) throws IOException {
         final int version = in.readInt();
         switch (version) {
@@ -204,6 +218,7 @@
         }
     }
 
+    /** @hide */
     public void writeToStream(DataOutput out) throws IOException {
         out.writeInt(VERSION_ADD_ACTIVE);
         out.writeLong(bucketDuration);
@@ -221,15 +236,18 @@
         return 0;
     }
 
+    /** @hide */
     @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.R, trackingBug = 170729553)
     public int size() {
         return bucketCount;
     }
 
+    /** @hide */
     public long getBucketDuration() {
         return bucketDuration;
     }
 
+    /** @hide */
     @UnsupportedAppUsage
     public long getStart() {
         if (bucketCount > 0) {
@@ -239,6 +257,7 @@
         }
     }
 
+    /** @hide */
     @UnsupportedAppUsage
     public long getEnd() {
         if (bucketCount > 0) {
@@ -250,6 +269,7 @@
 
     /**
      * Return total bytes represented by this history.
+     * @hide
      */
     public long getTotalBytes() {
         return totalBytes;
@@ -258,6 +278,7 @@
     /**
      * Return index of bucket that contains or is immediately before the
      * requested time.
+     * @hide
      */
     @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.R, trackingBug = 170729553)
     public int getIndexBefore(long time) {
@@ -273,6 +294,7 @@
     /**
      * Return index of bucket that contains or is immediately after the
      * requested time.
+     * @hide
      */
     public int getIndexAfter(long time) {
         int index = Arrays.binarySearch(bucketStart, 0, bucketCount, time);
@@ -286,6 +308,7 @@
 
     /**
      * Return specific stats entry.
+     * @hide
      */
     @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.R, trackingBug = 170729553)
     public Entry getValues(int i, Entry recycle) {
@@ -301,6 +324,7 @@
         return entry;
     }
 
+    /** @hide */
     public void setValues(int i, Entry entry) {
         // Unwind old values
         if (rxBytes != null) totalBytes -= rxBytes[i];
@@ -322,6 +346,7 @@
     /**
      * Record that data traffic occurred in the given time range. Will
      * distribute across internal buckets, creating new buckets as needed.
+     * @hide
      */
     @Deprecated
     public void recordData(long start, long end, long rxBytes, long txBytes) {
@@ -332,6 +357,7 @@
     /**
      * Record that data traffic occurred in the given time range. Will
      * distribute across internal buckets, creating new buckets as needed.
+     * @hide
      */
     public void recordData(long start, long end, NetworkStats.Entry entry) {
         long rxBytes = entry.rxBytes;
@@ -392,6 +418,7 @@
     /**
      * Record an entire {@link NetworkStatsHistory} into this history. Usually
      * for combining together stats for external reporting.
+     * @hide
      */
     @UnsupportedAppUsage
     public void recordEntireHistory(NetworkStatsHistory input) {
@@ -402,6 +429,7 @@
      * Record given {@link NetworkStatsHistory} into this history, copying only
      * buckets that atomically occur in the inclusive time range. Doesn't
      * interpolate across partial buckets.
+     * @hide
      */
     public void recordHistory(NetworkStatsHistory input, long start, long end) {
         final NetworkStats.Entry entry = new NetworkStats.Entry(
@@ -483,6 +511,7 @@
 
     /**
      * Clear all data stored in this object.
+     * @hide
      */
     public void clear() {
         bucketStart = EmptyArray.LONG;
@@ -498,9 +527,10 @@
 
     /**
      * Remove buckets older than requested cutoff.
+     * @hide
      */
-    @Deprecated
     public void removeBucketsBefore(long cutoff) {
+        // TODO: Consider use getIndexBefore.
         int i;
         for (i = 0; i < bucketCount; i++) {
             final long curStart = bucketStart[i];
@@ -522,7 +552,9 @@
             if (operations != null) operations = Arrays.copyOfRange(operations, i, length);
             bucketCount -= i;
 
-            // TODO: subtract removed values from totalBytes
+            totalBytes = 0;
+            if (rxBytes != null) totalBytes += CollectionUtils.total(rxBytes);
+            if (txBytes != null) totalBytes += CollectionUtils.total(txBytes);
         }
     }
 
@@ -536,6 +568,7 @@
      * @param start - start of the range, timestamp in milliseconds since the epoch.
      * @param end - end of the range, timestamp in milliseconds since the epoch.
      * @param recycle - entry instance for performance, could be null.
+     * @hide
      */
     @UnsupportedAppUsage
     public Entry getValues(long start, long end, Entry recycle) {
@@ -550,6 +583,7 @@
      * @param end - end of the range, timestamp in milliseconds since the epoch.
      * @param now - current timestamp in milliseconds since the epoch (wall clock).
      * @param recycle - entry instance for performance, could be null.
+     * @hide
      */
     @UnsupportedAppUsage
     public Entry getValues(long start, long end, long now, Entry recycle) {
@@ -613,6 +647,7 @@
 
     /**
      * @deprecated only for temporary testing
+     * @hide
      */
     @Deprecated
     public void generateRandom(long start, long end, long bytes) {
@@ -631,6 +666,7 @@
 
     /**
      * @deprecated only for temporary testing
+     * @hide
      */
     @Deprecated
     public void generateRandom(long start, long end, long rxBytes, long rxPackets, long txBytes,
@@ -660,12 +696,14 @@
         }
     }
 
+    /** @hide */
     public static long randomLong(Random r, long start, long end) {
         return (long) (start + (r.nextFloat() * (end - start)));
     }
 
     /**
      * Quickly determine if this history intersects with given window.
+     * @hide
      */
     public boolean intersects(long start, long end) {
         final long dataStart = getStart();
@@ -677,6 +715,7 @@
         return false;
     }
 
+    /** @hide */
     public void dump(IndentingPrintWriter pw, boolean fullHistory) {
         pw.print("NetworkStatsHistory: bucketDuration=");
         pw.println(bucketDuration / SECOND_IN_MILLIS);
@@ -700,6 +739,7 @@
         pw.decreaseIndent();
     }
 
+    /** @hide */
     public void dumpCheckin(PrintWriter pw) {
         pw.print("d,");
         pw.print(bucketDuration / SECOND_IN_MILLIS);
@@ -717,6 +757,7 @@
         }
     }
 
+    /** @hide */
     public void dumpDebug(ProtoOutputStream proto, long tag) {
         final long start = proto.start(tag);
 
@@ -776,6 +817,7 @@
         if (array != null) array[i] += value;
     }
 
+    /** @hide */
     public int estimateResizeBuckets(long newBucketDuration) {
         return (int) (size() * getBucketDuration() / newBucketDuration);
     }
@@ -783,6 +825,7 @@
     /**
      * Utility methods for interacting with {@link DataInputStream} and
      * {@link DataOutputStream}, mostly dealing with writing partial arrays.
+     * @hide
      */
     public static class DataStreamUtils {
         @Deprecated
@@ -857,6 +900,7 @@
     /**
      * Utility methods for interacting with {@link Parcel} structures, mostly
      * dealing with writing partial arrays.
+     * @hide
      */
     public static class ParcelUtils {
         public static long[] readLongArray(Parcel in) {
diff --git a/framework-t/src/android/net/NetworkTemplate.java b/framework-t/src/android/net/NetworkTemplate.java
index e9084b0..a7e48d4 100644
--- a/framework-t/src/android/net/NetworkTemplate.java
+++ b/framework-t/src/android/net/NetworkTemplate.java
@@ -364,7 +364,7 @@
     private final int mMetered;
     private final int mRoaming;
     private final int mDefaultNetwork;
-    private final int mSubType;
+    private final int mRatType;
     /**
      * The subscriber Id match rule defines how the template should match networks with
      * specific subscriberId(s). See NetworkTemplate#SUBSCRIBER_ID_MATCH_RULE_* for more detail.
@@ -413,18 +413,18 @@
     /** @hide */
     // TODO: Remove it after updating all of the caller.
     public NetworkTemplate(int matchRule, String subscriberId, String[] matchSubscriberIds,
-            String wifiNetworkKey, int metered, int roaming, int defaultNetwork, int subType,
+            String wifiNetworkKey, int metered, int roaming, int defaultNetwork, int ratType,
             int oemManaged) {
         this(matchRule, subscriberId, matchSubscriberIds,
                 wifiNetworkKey != null ? new String[] { wifiNetworkKey } : new String[0],
-                metered, roaming, defaultNetwork, subType, oemManaged,
+                metered, roaming, defaultNetwork, ratType, oemManaged,
                 NetworkStatsUtils.SUBSCRIBER_ID_MATCH_RULE_EXACT);
     }
 
     /** @hide */
     public NetworkTemplate(int matchRule, String subscriberId, String[] matchSubscriberIds,
             String[] matchWifiNetworkKeys, int metered, int roaming,
-            int defaultNetwork, int subType, int oemManaged, int subscriberIdMatchRule) {
+            int defaultNetwork, int ratType, int oemManaged, int subscriberIdMatchRule) {
         Objects.requireNonNull(matchWifiNetworkKeys);
         mMatchRule = matchRule;
         mSubscriberId = subscriberId;
@@ -435,7 +435,7 @@
         mMetered = metered;
         mRoaming = roaming;
         mDefaultNetwork = defaultNetwork;
-        mSubType = subType;
+        mRatType = ratType;
         mOemManaged = oemManaged;
         mSubscriberIdMatchRule = subscriberIdMatchRule;
         checkValidSubscriberIdMatchRule(matchRule, subscriberIdMatchRule);
@@ -453,7 +453,7 @@
         mMetered = in.readInt();
         mRoaming = in.readInt();
         mDefaultNetwork = in.readInt();
-        mSubType = in.readInt();
+        mRatType = in.readInt();
         mOemManaged = in.readInt();
         mSubscriberIdMatchRule = in.readInt();
     }
@@ -467,7 +467,7 @@
         dest.writeInt(mMetered);
         dest.writeInt(mRoaming);
         dest.writeInt(mDefaultNetwork);
-        dest.writeInt(mSubType);
+        dest.writeInt(mRatType);
         dest.writeInt(mOemManaged);
         dest.writeInt(mSubscriberIdMatchRule);
     }
@@ -500,8 +500,8 @@
             builder.append(", defaultNetwork=").append(NetworkStats.defaultNetworkToString(
                     mDefaultNetwork));
         }
-        if (mSubType != NETWORK_TYPE_ALL) {
-            builder.append(", subType=").append(mSubType);
+        if (mRatType != NETWORK_TYPE_ALL) {
+            builder.append(", ratType=").append(mRatType);
         }
         if (mOemManaged != OEM_MANAGED_ALL) {
             builder.append(", oemManaged=").append(getOemManagedNames(mOemManaged));
@@ -514,7 +514,7 @@
     @Override
     public int hashCode() {
         return Objects.hash(mMatchRule, mSubscriberId, Arrays.hashCode(mMatchWifiNetworkKeys),
-                mMetered, mRoaming, mDefaultNetwork, mSubType, mOemManaged, mSubscriberIdMatchRule);
+                mMetered, mRoaming, mDefaultNetwork, mRatType, mOemManaged, mSubscriberIdMatchRule);
     }
 
     @Override
@@ -526,7 +526,7 @@
                     && mMetered == other.mMetered
                     && mRoaming == other.mRoaming
                     && mDefaultNetwork == other.mDefaultNetwork
-                    && mSubType == other.mSubType
+                    && mRatType == other.mRatType
                     && mOemManaged == other.mOemManaged
                     && mSubscriberIdMatchRule == other.mSubscriberIdMatchRule
                     && Arrays.equals(mMatchWifiNetworkKeys, other.mMatchWifiNetworkKeys);
@@ -635,7 +635,7 @@
      * Get the Radio Access Technology(RAT) type filter of the template.
      */
     public int getRatType() {
-        return mSubType;
+        return mRatType;
     }
 
     /**
@@ -708,8 +708,8 @@
     }
 
     private boolean matchesCollapsedRatType(NetworkIdentity ident) {
-        return mSubType == NETWORK_TYPE_ALL
-                || getCollapsedRatType(mSubType) == getCollapsedRatType(ident.mSubType);
+        return mRatType == NETWORK_TYPE_ALL
+                || getCollapsedRatType(mRatType) == getCollapsedRatType(ident.mRatType);
     }
 
     /**
@@ -837,7 +837,7 @@
         switch (ident.mType) {
             case TYPE_WIFI:
                 return matchesSubscriberId(ident.mSubscriberId)
-                        && matchesWifiNetworkKey(ident.mNetworkId);
+                        && matchesWifiNetworkKey(ident.mWifiNetworkKey);
             default:
                 return false;
         }
diff --git a/service-t/src/com/android/server/net/NetworkStatsService.java b/service-t/src/com/android/server/net/NetworkStatsService.java
index a0710f7..4bb61bd 100644
--- a/service-t/src/com/android/server/net/NetworkStatsService.java
+++ b/service-t/src/com/android/server/net/NetworkStatsService.java
@@ -19,12 +19,15 @@
 import static android.Manifest.permission.NETWORK_STATS_PROVIDER;
 import static android.Manifest.permission.READ_NETWORK_USAGE_HISTORY;
 import static android.Manifest.permission.UPDATE_DEVICE_STATS;
+import static android.app.usage.NetworkStatsManager.PREFIX_DEV;
+import static android.app.usage.NetworkStatsManager.PREFIX_UID;
+import static android.app.usage.NetworkStatsManager.PREFIX_UID_TAG;
+import static android.app.usage.NetworkStatsManager.PREFIX_XT;
 import static android.content.Intent.ACTION_SHUTDOWN;
 import static android.content.Intent.ACTION_UID_REMOVED;
 import static android.content.Intent.ACTION_USER_REMOVED;
 import static android.content.Intent.EXTRA_UID;
 import static android.content.pm.PackageManager.PERMISSION_GRANTED;
-import static android.net.NetworkIdentity.SUBTYPE_COMBINED;
 import static android.net.NetworkStats.DEFAULT_NETWORK_ALL;
 import static android.net.NetworkStats.IFACE_ALL;
 import static android.net.NetworkStats.IFACE_VT;
@@ -243,11 +246,6 @@
 
     private PendingIntent mPollIntent;
 
-    private static final String PREFIX_DEV = "dev";
-    private static final String PREFIX_XT = "xt";
-    private static final String PREFIX_UID = "uid";
-    private static final String PREFIX_UID_TAG = "uid_tag";
-
     /**
      * Settings that can be changed externally.
      */
@@ -257,9 +255,9 @@
         boolean getSampleEnabled();
         boolean getAugmentEnabled();
         /**
-         * When enabled, all mobile data is reported under {@link NetworkIdentity#SUBTYPE_COMBINED}.
-         * When disabled, mobile data is broken down by a granular subtype representative of the
-         * actual subtype. {@see NetworkTemplate#getCollapsedRatType}.
+         * When enabled, all mobile data is reported under {@link NetworkTemplate#NETWORK_TYPE_ALL}.
+         * When disabled, mobile data is broken down by a granular ratType representative of the
+         * actual ratType. {@see NetworkTemplate#getCollapsedRatType}.
          * Enabling this decreases the level of detail but saves performance, disk space and
          * amount of data logged.
          */
@@ -1389,10 +1387,10 @@
             final boolean isMobile = (NetworkCapabilities.TRANSPORT_CELLULAR == displayTransport);
             final boolean isDefault = CollectionUtils.contains(
                     mDefaultNetworks, snapshot.getNetwork());
-            final int subType = combineSubtypeEnabled ? SUBTYPE_COMBINED
-                    : getSubTypeForStateSnapshot(snapshot);
+            final int ratType = combineSubtypeEnabled ? NetworkTemplate.NETWORK_TYPE_ALL
+                    : getRatTypeForStateSnapshot(snapshot);
             final NetworkIdentity ident = NetworkIdentity.buildNetworkIdentity(mContext, snapshot,
-                    isDefault, subType);
+                    isDefault, ratType);
 
             // Traffic occurring on the base interface is always counted for
             // both total usage and UID details.
@@ -1411,7 +1409,7 @@
 
                     // Copy the identify from IMS one but mark it as metered.
                     NetworkIdentity vtIdent = new NetworkIdentity(ident.getType(),
-                            ident.getSubType(), ident.getSubscriberId(), ident.getNetworkId(),
+                            ident.getRatType(), ident.getSubscriberId(), ident.getWifiNetworkKey(),
                             ident.getRoaming(), true /* metered */,
                             true /* onDefaultNetwork */, ident.getOemManaged());
                     final String ifaceVt = IFACE_VT + getSubIdForMobile(snapshot);
@@ -1492,11 +1490,11 @@
     }
 
     /**
-     * For networks with {@code TRANSPORT_CELLULAR}, get subType that was obtained through
+     * For networks with {@code TRANSPORT_CELLULAR}, get ratType that was obtained through
      * {@link PhoneStateListener}. Otherwise, return 0 given that other networks with different
      * transport types do not actually fill this value.
      */
-    private int getSubTypeForStateSnapshot(@NonNull NetworkStateSnapshot state) {
+    private int getRatTypeForStateSnapshot(@NonNull NetworkStateSnapshot state) {
         if (!state.getNetworkCapabilities().hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR)) {
             return 0;
         }