diff --git a/cmd/main.go b/cmd/main.go
index 112f2f2..fddb10a 100644
--- a/cmd/main.go
+++ b/cmd/main.go
@@ -41,11 +41,11 @@ Usage:
     -tcp_bs   tcp的发送接收缓冲区大小，默认1MB
               Tcp send and receive buffer size, default 1MB
 
-    -tcp_mw   tcp的最大窗口，默认100
+    -tcp_mw   tcp的最大窗口，默认10000
               The maximum window of tcp, the default is 100
 
-    -tcp_rst  tcp的超时发送时间，默认200ms
-              Tcp timeout resend time, default 200ms
+    -tcp_rst  tcp的超时发送时间，默认400ms
+              Tcp timeout resend time, default 400ms
 `
 
 func main() {
@@ -59,7 +59,7 @@ func main() {
 	tcpmode := flag.Int("tcp", 0, "tcp mode")
 	tcpmode_buffersize := flag.Int("tcp_bs", 1024*1024, "tcp mode buffer size")
 	tcpmode_maxwin := flag.Int("tcp_mw", 100, "tcp mode max win")
-	tcpmode_resend_timems := flag.Int("tcp_rst", 200, "tcp mode resend time ms")
+	tcpmode_resend_timems := flag.Int("tcp_rst", 400, "tcp mode resend time ms")
 	flag.Usage = func() {
 		fmt.Printf(usage)
 	}
diff --git a/framemgr.go b/framemgr.go
index f321c9a..f2baba5 100644
--- a/framemgr.go
+++ b/framemgr.go
@@ -28,6 +28,9 @@ type FrameMgr struct {
 	close        bool
 	remoteclosed bool
 	closesend    bool
+
+	lastPingTime int64
+	rttms        int
 }
 
 func NewFrameMgr(buffersize int, windowsize int, resend_timems int) *FrameMgr {
@@ -40,7 +43,8 @@ func NewFrameMgr(buffersize int, windowsize int, resend_timems int) *FrameMgr {
 		windowsize: windowsize, resend_timems: resend_timems,
 		sendwin: list.New(), sendlist: list.New(), sendid: 0,
 		recvwin: list.New(), recvlist: list.New(), recvid: 0,
-		close: false, remoteclosed: false, closesend: false}
+		close: false, remoteclosed: false, closesend: false,
+		lastPingTime: time.Now().UnixNano(), rttms: resend_timems}
 
 	return fm
 }
@@ -66,6 +70,8 @@ func (fm *FrameMgr) Update() {
 	fm.combineWindowToRecvBuffer()
 
 	fm.calSendList()
+
+	fm.ping()
 }
 
 func (fm *FrameMgr) cutSendBufferToWindow() {
@@ -166,6 +172,10 @@ func (fm *FrameMgr) preProcessRecvList() (map[int32]int, map[int32]int, map[int3
 		} else if f.Type == (int32)(Frame_DATA) {
 			tmpackto[f.Id] = f
 			loggo.Debug("recv data %d %d", f.Id, len(f.Data))
+		} else if f.Type == (int32)(Frame_PING) {
+			fm.processPing(f)
+		} else if f.Type == (int32)(Frame_PONG) {
+			fm.processPong(f)
 		}
 	}
 	fm.recvlist.Init()
@@ -202,17 +212,18 @@ func (fm *FrameMgr) processRecvList(tmpreq map[int32]int, tmpack map[int32]int,
 			Dataid: make([]int32, len(tmpackto))}
 		index := 0
 		for id, rf := range tmpackto {
-			f.Dataid[index] = id
-			index++
-			fm.addToRecvWin(rf)
-			loggo.Debug("add data to win %d %d", rf.Id, len(rf.Data))
+			if fm.addToRecvWin(rf) {
+				f.Dataid[index] = id
+				index++
+				loggo.Debug("add data to win %d %d", rf.Id, len(rf.Data))
+			}
 		}
 		fm.sendlist.PushBack(f)
 		loggo.Debug("send ack %d %s", f.Id, common.Int32ArrayToString(f.Dataid, ","))
 	}
 }
 
-func (fm *FrameMgr) addToRecvWin(rf *Frame) {
+func (fm *FrameMgr) addToRecvWin(rf *Frame) bool {
 
 	begin := fm.recvid
 	end := fm.recvid + fm.windowsize
@@ -222,14 +233,14 @@ func (fm *FrameMgr) addToRecvWin(rf *Frame) {
 	}
 	if id > end || id < begin {
 		loggo.Debug("recv frame not in range %d %d %d", begin, end, id)
-		return
+		return false
 	}
 
 	for e := fm.recvwin.Front(); e != nil; e = e.Next() {
 		f := e.Value.(*Frame)
 		if f.Id == rf.Id {
 			loggo.Debug("recv frame ignore %d %d", f.Id, len(f.Data))
-			return
+			return true
 		}
 	}
 
@@ -239,12 +250,13 @@ func (fm *FrameMgr) addToRecvWin(rf *Frame) {
 		if fm.compareId(rf, f) < 0 {
 			fm.recvwin.InsertBefore(rf, e)
 			loggo.Debug("insert recv win %d %d before %d", rf.Id, len(rf.Data), f.Id)
-			return
+			return true
 		}
 	}
 
 	fm.recvwin.PushBack(rf)
 	loggo.Debug("insert recv win last %d %d", rf.Id, len(rf.Data))
+	return true
 }
 
 func (fm *FrameMgr) compareId(lf *Frame, rf *Frame) int {
@@ -300,7 +312,7 @@ func (fm *FrameMgr) combineWindowToRecvBuffer() {
 	id = fm.recvid
 	for len(reqtmp) < fm.windowsize && e != nil {
 		f := e.Value.(*Frame)
-		loggo.Debug("start add req id %d %d", f.Id, id)
+		loggo.Debug("start add req id %d %d %d", fm.recvid, f.Id, id)
 		if f.Id != (int32)(id) {
 			reqtmp[id]++
 			loggo.Debug("add req id %d ", id)
@@ -353,3 +365,30 @@ func (fm *FrameMgr) Close() {
 func (fm *FrameMgr) IsRemoteClosed() bool {
 	return fm.remoteclosed
 }
+
+func (fm *FrameMgr) ping() {
+	cur := time.Now().UnixNano()
+	if cur-fm.lastPingTime > int64(1000*1000) {
+		f := &Frame{Type: (int32)(Frame_PING), Resend: false, Sendtime: cur,
+			Id: 0}
+		fm.sendlist.PushBack(f)
+		loggo.Debug("send ping %d", cur)
+		fm.lastPingTime = cur
+	}
+}
+
+func (fm *FrameMgr) processPing(f *Frame) {
+	rf := &Frame{Type: (int32)(Frame_PONG), Resend: false, Sendtime: f.Sendtime,
+		Id: 0}
+	fm.sendlist.PushBack(rf)
+	loggo.Debug("recv ping %d", f.Sendtime)
+}
+
+func (fm *FrameMgr) processPong(f *Frame) {
+	cur := time.Now().UnixNano()
+	if cur > f.Sendtime {
+		rtt := (cur - f.Sendtime) / 1000
+		fm.rttms = (fm.rttms + (int)(rtt)) / 2
+		loggo.Debug("recv pong %d %d", rtt, fm.rttms)
+	}
+}
diff --git a/msg.pb.go b/msg.pb.go
index df82ed3..6c3a92f 100644
--- a/msg.pb.go
+++ b/msg.pb.go
@@ -54,18 +54,24 @@ const (
 	Frame_DATA Frame_TYPE = 0
 	Frame_REQ  Frame_TYPE = 1
 	Frame_ACK  Frame_TYPE = 2
+	Frame_PING Frame_TYPE = 3
+	Frame_PONG Frame_TYPE = 4
 )
 
 var Frame_TYPE_name = map[int32]string{
 	0: "DATA",
 	1: "REQ",
 	2: "ACK",
+	3: "PING",
+	4: "PONG",
 }
 
 var Frame_TYPE_value = map[string]int32{
 	"DATA": 0,
 	"REQ":  1,
 	"ACK":  2,
+	"PING": 3,
+	"PONG": 4,
 }
 
 func (x Frame_TYPE) String() string {
@@ -292,29 +298,29 @@ func init() {
 func init() { proto.RegisterFile("msg.proto", fileDescriptor_c06e4cca6c2cc899) }
 
 var fileDescriptor_c06e4cca6c2cc899 = []byte{
-	// 372 bytes of a gzipped FileDescriptorProto
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-	0x7e, 0xf8, 0xb9, 0x0c, 0xce, 0x10, 0x09, 0xc7, 0xd8, 0x0b, 0x88, 0xec, 0x69, 0x5f, 0xc3, 0x29,
-	0x7c, 0x71, 0xe5, 0x6e, 0xc8, 0x00, 0x6f, 0x71, 0x43, 0xe2, 0x38, 0xf4, 0x76, 0x1c, 0x7b, 0xaa,
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-	0x54, 0x02, 0x00, 0x00,
+	// 383 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x64, 0x51, 0x5d, 0xab, 0xd3, 0x30,
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+	0xed, 0xc1, 0xf0, 0x99, 0xeb, 0x78, 0xa2, 0xe9, 0x0b, 0x08, 0xd6, 0x9f, 0x57, 0xf7, 0x2c, 0x82,
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+	0x38, 0xb8, 0x9d, 0x7d, 0x81, 0x4e, 0x35, 0xb5, 0x39, 0x34, 0x8d, 0xfc, 0xb6, 0x0d, 0x71, 0xe9,
+	0x37, 0xff, 0x02, 0x00, 0x00, 0xff, 0xff, 0x10, 0x46, 0x79, 0xfa, 0x68, 0x02, 0x00, 0x00,
 }
diff --git a/msg.proto b/msg.proto
index a0d5553..429bc22 100644
--- a/msg.proto
+++ b/msg.proto
@@ -27,6 +27,8 @@ message Frame {
     DATA = 0;
     REQ = 1;
     ACK = 2;
+    PING = 3;
+    PONG = 4;
   }
   
   int32 type = 1;