diff --git a/trunk/src/protocol/srs_protocol_kbps.cpp b/trunk/src/protocol/srs_protocol_kbps.cpp
index 554d6615e0..0c6234e6d6 100644
--- a/trunk/src/protocol/srs_protocol_kbps.cpp
+++ b/trunk/src/protocol/srs_protocol_kbps.cpp
@@ -120,13 +120,13 @@ void SrsKbps::set_io(ISrsProtocolStatistic* in, ISrsProtocolStatistic* out)
     }
     // save the old in bytes.
     if (is.io.in) {
-        is.bytes += is.last_bytes - is.io_bytes_base;
+        is.bytes += is.io.in->get_recv_bytes() - is.io_bytes_base;
     }
     // use new io.
     is.io.in = in;
     is.last_bytes = is.io_bytes_base = 0;
     if (in) {
-        is.bytes += is.io.in->get_recv_bytes() - is.io_bytes_base;
+        is.last_bytes = is.io_bytes_base = in->get_recv_bytes();
     }
     // resample
     is.sample();
@@ -199,11 +199,16 @@ int64_t SrsKbps::get_send_bytes()
     // session start bytes.
     int64_t bytes = os.bytes;
     
-    // session delta.
+    // When exists active session, use it to get the last bytes.
     if (os.io.out) {
         bytes += os.io.out->get_send_bytes() - os.io_bytes_base;
+        return bytes;
     }
     
+    // When no active session, the last_bytes record the last valid bytes.
+    // TODO: Maybe the bellow bytes is zero, because the ios.io.out is NULL.
+    bytes += os.last_bytes - os.io_bytes_base;
+
     return bytes;
 }
 
@@ -216,11 +221,16 @@ int64_t SrsKbps::get_recv_bytes()
     // session start bytes.
     int64_t bytes = is.bytes;
     
-    // session delta.
+    // When exists active session, use it to get the last bytes.
     if (is.io.in) {
         bytes += is.io.in->get_recv_bytes() - is.io_bytes_base;
+        return bytes;
     }
     
+    // When no active session, the last_bytes record the last valid bytes.
+    // TODO: Maybe the bellow bytes is zero, because the ios.io.out is NULL.
+    bytes += is.last_bytes - is.io_bytes_base;
+
     return bytes;
 }
 
@@ -274,3 +284,8 @@ void SrsKbps::sample()
     os.sample();
 }
 
+int SrsKbps::size_memory()
+{
+    return sizeof(SrsKbps);
+}
+
diff --git a/trunk/src/protocol/srs_protocol_kbps.hpp b/trunk/src/protocol/srs_protocol_kbps.hpp
index 5c54520153..dd5a8ada09 100644
--- a/trunk/src/protocol/srs_protocol_kbps.hpp
+++ b/trunk/src/protocol/srs_protocol_kbps.hpp
@@ -157,14 +157,14 @@ class IKbpsDelta
  *      delta->resample();
  *      printf("delta is %d/%d", delta->get_send_bytes_delta(), delta->get_recv_bytes_delta());
  *      delta->cleanup();
- *   the server never know how many bytes already send/recv, for the connection maybe closed.
  * 4. kbps used as ISrsProtocolStatistic, to provides raw bytes:
  *      SrsKbps* kbps = ...;
  *      kbps->set_io(in, out);
  *      // both kbps->get_recv_bytes() and kbps->get_send_bytes() are available.
- *      // we can use the kbps as the data source of another kbps:
+*       // we can use the kbps as the data source of another kbps:
  *      SrsKbps* user = ...;
  *      user->set_io(kbps, kbps);
+ *   the server never know how many bytes already send/recv, for the connection maybe closed.
  */
 class SrsKbps : public virtual ISrsProtocolStatistic, public virtual IKbpsDelta
 {
@@ -198,26 +198,15 @@ class SrsKbps : public virtual ISrsProtocolStatistic, public virtual IKbpsDelta
     // 5m
     virtual int get_send_kbps_5m();
     virtual int get_recv_kbps_5m();
+// interface ISrsProtocolStatistic
 public:
-    /**
-    * get the total send/recv bytes, from the startup of the oldest io.
-    * @remark, use sample() to update data.
-    */
     virtual int64_t get_send_bytes();
     virtual int64_t get_recv_bytes();
+// interface IKbpsDelta
 public:
-    /**
-    * resample to get the delta.
-    */
     virtual void resample();
-    /**
-    * get the delta of send/recv bytes.
-    */
     virtual int64_t get_send_bytes_delta();
     virtual int64_t get_recv_bytes_delta();
-    /**
-    * cleanup the delta.
-    */
     virtual void cleanup();
 public:
     /**
@@ -235,6 +224,9 @@ class SrsKbps : public virtual ISrsProtocolStatistic, public virtual IKbpsDelta
     *       use the add_delta() is better solutions.
     */
     virtual void sample();
+// interface ISrsMemorySizer
+public:
+    virtual int size_memory();
 };
 
 #endif