diff --git a/go.mod b/go.mod
index a37d7ef..a585310 100644
--- a/go.mod
+++ b/go.mod
@@ -6,7 +6,7 @@ require (
 	github.com/fumiama/go-base16384 v1.2.1
 	github.com/fumiama/go-x25519 v1.0.0
 	github.com/fumiama/gofastTEA v0.0.6
-	github.com/fumiama/water v0.0.0-20211230051437-3d685121087a
+	github.com/fumiama/water v0.0.0-20211230160439-38601da6d162
 	github.com/minio/blake2b-simd v0.0.0-20160723061019-3f5f724cb5b1
 	github.com/sirupsen/logrus v1.8.1
 	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b
diff --git a/go.sum b/go.sum
index 408f1f8..f54b2d6 100644
--- a/go.sum
+++ b/go.sum
@@ -12,6 +12,8 @@ github.com/fumiama/gofastTEA v0.0.6 h1:Yni3MXDbJVa/c4CecgdZDgCJK+fLdvGph+OBqY2mt
 github.com/fumiama/gofastTEA v0.0.6/go.mod h1:+sBZ05nCA2skZkursHNvyr8kULlEetrYTM2y5kA4rQc=
 github.com/fumiama/water v0.0.0-20211230051437-3d685121087a h1:jVm9uuodbGiBqJzPEHSpYjdFZQ+B9SwBrpXCffr90GY=
 github.com/fumiama/water v0.0.0-20211230051437-3d685121087a/go.mod h1:BBnNY9PwK+UUn4trAU+H0qsMEypm7+3Bj1bVFuJItlo=
+github.com/fumiama/water v0.0.0-20211230160439-38601da6d162 h1:4thbCXSKhrmks1cnH8TEWTXBjnp0dwKuUSPgpghSG+M=
+github.com/fumiama/water v0.0.0-20211230160439-38601da6d162/go.mod h1:BBnNY9PwK+UUn4trAU+H0qsMEypm7+3Bj1bVFuJItlo=
 github.com/fumiama/wintun v0.0.0-20211229152851-8bc97c8034c0 h1:WfrSFlIlCAtg6Rt2IGna0HhJYSDE45YVHiYqO4wwsEw=
 github.com/fumiama/wintun v0.0.0-20211229152851-8bc97c8034c0/go.mod h1:dPOG7Af/ArO62RgBz2JJTNFByBn/IXWLo/1kZKcLSe8=
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
diff --git a/gold/link/link.go b/gold/link/link.go
index 53e180b..a8ce8b9 100644
--- a/gold/link/link.go
+++ b/gold/link/link.go
@@ -75,20 +75,20 @@ func (l *Link) Read() *head.Packet {
 
 // Write 向 peer 发包
 func (l *Link) Write(p *head.Packet, istransfer bool) (n int, err error) {
-	if len(p.Data) <= int(l.me.mtu) {
+	if len(p.Data) <= 32768 {
 		return l.write(p, istransfer)
 	}
 	data := p.Data
 	offset := 0
-	for len(data) > int(l.me.mtu) {
+	for len(data) > 32768 {
 		packet := *p
-		packet.Data = data[offset*int(l.me.mtu) : (offset+1)*int(l.me.mtu)]
+		packet.Data = data[offset*32768 : (offset+1)*32768]
 		i, err := l.write(&packet, istransfer)
 		n += i
 		if err != nil {
 			return n, err
 		}
-		data = data[(offset+1)*int(l.me.mtu):]
+		data = data[(offset+1)*32768:]
 	}
 	return n, nil
 }
diff --git a/gold/link/me.go b/gold/link/me.go
index 9a5fdc3..bba8f60 100644
--- a/gold/link/me.go
+++ b/gold/link/me.go
@@ -32,9 +32,6 @@ type Me struct {
 	pipe chan *head.Packet
 	// 本机路由表
 	router *Router
-	// 虚拟链路网卡 MTU
-	// 默认 30000
-	mtu uint16
 }
 
 // NewMe 设置本机参数
@@ -65,10 +62,5 @@ func NewMe(privateKey *[32]byte, myipwithmask string, myEndpoint string, nopipei
 	}
 	m.router.SetDefault(nil)
 	m.loop = m.AddPeer(m.me.String(), nil, "127.0.0.1:56789", []string{myipwithmask}, 0, false, nopipeinlink)
-	m.mtu = 30000
 	return
 }
-
-func (m *Me) SetMTU(mtu uint16) {
-	m.mtu = mtu
-}
diff --git a/lower/nic.go b/lower/nic.go
index ce97cc8..17ca98f 100644
--- a/lower/nic.go
+++ b/lower/nic.go
@@ -1,6 +1,7 @@
 package lower
 
 import (
+	"encoding/binary"
 	"os"
 	"os/exec"
 	"strconv"
@@ -57,7 +58,7 @@ func (nc *NIC) Start(m *link.Me) {
 			logrus.Infoln("[lower] recv write", n, "bytes packet to nic")
 		}
 	}()
-	buf := make([]byte, 32768) // Ring capacity
+	buf := make([]byte, 32704) // 头部 52 + TEA 加密补足 16倍数
 	for nc.hasstart {          // 从 NIC 发送
 		packet := buf
 		n, err := nc.ifce.Read(packet)
@@ -69,22 +70,9 @@ func (nc *NIC) Start(m *link.Me) {
 			continue
 		}
 		packet = packet[:n]
-		if !waterutil.IsIPv4(packet) {
-			logrus.Warnln("[lower] skip to send", len(packet), "bytes non-ipv4 packet")
-			continue
-		}
-		dst := waterutil.IPv4Destination(packet)
-		srcport := waterutil.IPv4SourcePort(packet)
-		dstport := waterutil.IPv4DestinationPort(packet)
-		logrus.Infoln("[lower] sending", n, "bytes packet from :"+strconv.Itoa(int(srcport)), "to", dst.String()+":"+strconv.Itoa(int(dstport)))
-		lnk, err := m.Connect(dst.String())
-		if err != nil {
-			logrus.Warnln("[lower] connect to peer", dst.String(), "err:", err)
-			continue
-		}
-		_, err = lnk.Write(head.NewPacket(head.ProtoData, srcport, dst, dstport, packet), false)
-		if err != nil {
-			logrus.Warnln("[lower] write to peer", dst.String(), "err:", err)
+		_, rem := send(m, packet)
+		for len(rem) > 0 {
+			_, rem = send(m, rem)
 		}
 	}
 }
@@ -110,3 +98,34 @@ func execute(c string, args ...string) {
 		logrus.Panicln("[lower] failed to exec cmd:", err)
 	}
 }
+
+func send(m *link.Me, packet []byte) (n int, rem []byte) {
+	if !waterutil.IsIPv4(packet) {
+		if waterutil.IsIPv6(packet) {
+			n = int(binary.BigEndian.Uint16(packet[4:6])) + 20
+			rem = packet[n:]
+			logrus.Warnln("[lower] skip to send", n, "bytes ipv6 packet")
+			return
+		}
+		logrus.Warnln("[lower] skip to send", len(packet), "bytes non-ipv4/v6 packet")
+		return len(packet), nil
+	}
+	totl := waterutil.IPv4TotalLength(packet)
+	rem = packet[totl:]
+	packet = packet[:totl]
+	n = int(totl)
+	dst := waterutil.IPv4Destination(packet)
+	srcport := waterutil.IPv4SourcePort(packet)
+	dstport := waterutil.IPv4DestinationPort(packet)
+	logrus.Infoln("[lower] sending", len(packet), "bytes packet from :"+strconv.Itoa(int(srcport)), "to", dst.String()+":"+strconv.Itoa(int(dstport)))
+	lnk, err := m.Connect(dst.String())
+	if err != nil {
+		logrus.Warnln("[lower] connect to peer", dst.String(), "err:", err)
+		return
+	}
+	_, err = lnk.Write(head.NewPacket(head.ProtoData, srcport, dst, dstport, packet), false)
+	if err != nil {
+		logrus.Warnln("[lower] write to peer", dst.String(), "err:", err)
+	}
+	return
+}