diff --git a/src/inc/taoserror.h b/src/inc/taoserror.h
index c913b2cf2a6fb1506d5c6d9b1d483ec063bede01..58e19ce52af1402ab34f073c3ed3262bcab00092 100644
--- a/src/inc/taoserror.h
+++ b/src/inc/taoserror.h
@@ -267,6 +267,11 @@ TAOS_DEFINE_ERROR(TSDB_CODE_SYN_NOT_ENABLED,              0, 0x0901, "Sync modul
 TAOS_DEFINE_ERROR(TSDB_CODE_SYN_INVALID_VERSION,          0, 0x0902, "Invalid Sync version")
 TAOS_DEFINE_ERROR(TSDB_CODE_SYN_CONFIRM_EXPIRED,          0, 0x0903, "Sync confirm expired")
 TAOS_DEFINE_ERROR(TSDB_CODE_SYN_TOO_MANY_FWDINFO,         0, 0x0904, "Too many sync fwd infos")
+TAOS_DEFINE_ERROR(TSDB_CODE_SYN_MISMATCHED_PROTOCOL,      0, 0x0905, "Mismatched protocol")
+TAOS_DEFINE_ERROR(TSDB_CODE_SYN_MISMATCHED_CLUSTERID,     0, 0x0906, "Mismatched clusterId")
+TAOS_DEFINE_ERROR(TSDB_CODE_SYN_MISMATCHED_SIGNATURE,     0, 0x0907, "Mismatched signature")
+TAOS_DEFINE_ERROR(TSDB_CODE_SYN_INVALID_CHECKSUM,         0, 0x0908, "Invalid msg checksum")
+TAOS_DEFINE_ERROR(TSDB_CODE_SYN_INVALID_MSGLEN,           0, 0x0909, "Invalid msg length")
 
 // wal
 TAOS_DEFINE_ERROR(TSDB_CODE_WAL_APP_ERROR,                0, 0x1000, "Unexpected generic error in wal")
diff --git a/src/inc/vnode.h b/src/inc/vnode.h
index 95f1d27b591c2503461826e175c3e768c0db77cc..cbe64484b11462fcf3f107625cb0e00b0ac682f4 100644
--- a/src/inc/vnode.h
+++ b/src/inc/vnode.h
@@ -48,7 +48,7 @@ typedef struct {
   void *   pVnode;
   SRpcMsg  rpcMsg;
   SRspRet  rspRet;
-  char     reserveForSync[16];
+  char     reserveForSync[24];
   SWalHead pHead[];
 } SVWriteMsg;
 
diff --git a/src/mnode/inc/mnodeSdb.h b/src/mnode/inc/mnodeSdb.h
index 31ea2da640ef3b20b84ca769a22637332d6ffe34..e4df562d81c7ef91fe1ff62eba6611d76e0a3ff1 100644
--- a/src/mnode/inc/mnodeSdb.h
+++ b/src/mnode/inc/mnodeSdb.h
@@ -59,7 +59,7 @@ typedef struct SSdbRow {
   SMnodeMsg *pMsg;
   int32_t  (*fpReq)(SMnodeMsg *pMsg);
   int32_t  (*fpRsp)(SMnodeMsg *pMsg, int32_t code);
-  char       reserveForSync[16];
+  char       reserveForSync[24];
   SWalHead   pHead[];
 } SSdbRow;
 
diff --git a/src/sync/inc/syncInt.h b/src/sync/inc/syncInt.h
index c00015552fd9cebf5340052e036fc889d8780e6b..535251ba115edf75d2fdfd1efbcf809bc55bc142 100644
--- a/src/sync/inc/syncInt.h
+++ b/src/sync/inc/syncInt.h
@@ -13,12 +13,14 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#ifndef TDENGINE_SYNCINT_H
-#define TDENGINE_SYNCINT_H
+#ifndef TDENGINE_SYNC_INT_H
+#define TDENGINE_SYNC_INT_H
 
 #ifdef __cplusplus
 extern "C" {
 #endif
+#include "syncMsg.h"
+#include "twal.h"
 
 #define sFatal(...) { if (sDebugFlag & DEBUG_FATAL) { taosPrintLog("SYN FATAL ", sDebugFlag, __VA_ARGS__); }}
 #define sError(...) { if (sDebugFlag & DEBUG_ERROR) { taosPrintLog("SYN ERROR ", sDebugFlag, __VA_ARGS__); }}
@@ -27,88 +29,16 @@ extern "C" {
 #define sDebug(...) { if (sDebugFlag & DEBUG_DEBUG) { taosPrintLog("SYN ", sDebugFlag, __VA_ARGS__); }}
 #define sTrace(...) { if (sDebugFlag & DEBUG_TRACE) { taosPrintLog("SYN ", sDebugFlag, __VA_ARGS__); }}
 
-typedef enum {
-  TAOS_SMSG_SYNC_DATA     = 1,
-  TAOS_SMSG_FORWARD       = 2,
-  TAOS_SMSG_FORWARD_RSP   = 3,
-  TAOS_SMSG_SYNC_REQ      = 4,
-  TAOS_SMSG_SYNC_RSP      = 5,
-  TAOS_SMSG_SYNC_MUST     = 6,
-  TAOS_SMSG_STATUS        = 7,
-  TAOS_SMSG_SYNC_DATA_RSP = 8,
-} ESyncMsgType;
-
 #define SYNC_MAX_SIZE (TSDB_MAX_WAL_SIZE + sizeof(SWalHead) + sizeof(SSyncHead) + 16)
 #define SYNC_RECV_BUFFER_SIZE (5*1024*1024)
 #define SYNC_FWD_TIMER  300
 #define SYNC_ROLE_TIMER 10000
 #define SYNC_WAIT_AFTER_CHOOSE_MASTER 3
-#define SYNC_PROTOCOL_VERSION 0
 
 #define nodeRole    pNode->peerInfo[pNode->selfIndex]->role
 #define nodeVersion pNode->peerInfo[pNode->selfIndex]->version
 #define nodeSStatus pNode->peerInfo[pNode->selfIndex]->sstatus
 
-#pragma pack(push, 1)
-
-typedef struct {
-  int8_t   type;        // msg type
-  int8_t   protocol;    // protocol version
-  int8_t   reserved[6]; // not used
-  int32_t  vgId;        // vg ID
-  int32_t  len;         // content length, does not include head
-} SSyncHead;
-
-typedef struct {
-  SSyncHead head;
-  uint16_t  port;
-  uint16_t  tranId;
-  char      fqdn[TSDB_FQDN_LEN];
-  int32_t   sourceId;  // only for arbitrator
-} SSyncMsg;
-
-typedef struct {
-  SSyncHead head;
-  int8_t    sync;
-  int8_t    reserved;
-  uint16_t  tranId;
-} SSyncRsp;
-
-typedef struct {
-  int8_t    role;
-  uint64_t  version;
-} SPeerStatus;
-
-typedef struct {
-  int8_t      role;
-  int8_t      ack;
-  int8_t      type;
-  int8_t      reserved[3];
-  uint16_t    tranId;
-  uint64_t    version;
-  SPeerStatus peersStatus[];
-} SPeersStatus;
-
-typedef struct {
-  char      name[TSDB_FILENAME_LEN];
-  uint32_t  magic;
-  uint32_t  index;
-  uint64_t  fversion;
-  int64_t   size;
-} SFileInfo;
-
-typedef struct {
-  int8_t    sync;
-} SFileAck;
-
-typedef struct {
-  SSyncHead head;
-  uint64_t  version;
-  int32_t   code;
-} SFwdRsp;
-  
-#pragma pack(pop)
-
 typedef struct {
   char *  buffer;
   int32_t bufferSize;
@@ -192,7 +122,6 @@ void    syncRestartConnection(SSyncPeer *pPeer);
 void    syncBroadcastStatus(SSyncNode *pNode);
 void    syncAddPeerRef(SSyncPeer *pPeer);
 int32_t syncDecPeerRef(SSyncPeer *pPeer);
-uint16_t syncGenTranId();
 
 #ifdef __cplusplus
 }
diff --git a/src/sync/inc/syncMsg.h b/src/sync/inc/syncMsg.h
new file mode 100644
index 0000000000000000000000000000000000000000..9a7ff04de1ec18abc5017d18c7f09f113aba8c41
--- /dev/null
+++ b/src/sync/inc/syncMsg.h
@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <jhtao@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef TDENGINE_SYNC_MSG_H
+#define TDENGINE_SYNC_MSG_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+#include "tsync.h"
+
+typedef enum {
+  TAOS_SMSG_START         = 0,
+  TAOS_SMSG_SYNC_DATA     = 1,
+  TAOS_SMSG_SYNC_DATA_RSP = 2,
+  TAOS_SMSG_SYNC_FWD      = 3,
+  TAOS_SMSG_SYNC_FWD_RSP  = 4,
+  TAOS_SMSG_SYNC_REQ      = 5,
+  TAOS_SMSG_SYNC_REQ_RSP  = 6,
+  TAOS_SMSG_SYNC_MUST     = 7,
+  TAOS_SMSG_SYNC_MUST_RSP = 8,
+  TAOS_SMSG_STATUS        = 9,
+  TAOS_SMSG_STATUS_RSP    = 10,
+  TAOS_SMSG_SETUP         = 11,
+  TAOS_SMSG_SETUP_RSP     = 12,
+  TAOS_SMSG_END           = 13,
+} ESyncMsgType;
+
+typedef enum {
+  SYNC_STATUS_BROADCAST,
+  SYNC_STATUS_BROADCAST_RSP,
+  SYNC_STATUS_SETUP_CONN,
+  SYNC_STATUS_SETUP_CONN_RSP,
+  SYNC_STATUS_EXCHANGE_DATA,
+  SYNC_STATUS_EXCHANGE_DATA_RSP,
+  SYNC_STATUS_CHECK_ROLE,
+  SYNC_STATUS_CHECK_ROLE_RSP
+} ESyncStatusType;
+
+#pragma pack(push, 1)
+
+typedef struct {
+  int8_t   type;       // msg type
+  int8_t   protocol;   // protocol version
+  uint16_t signature;  // fixed value
+  int32_t  code;       //
+  int32_t  cId;        // cluster Id
+  int32_t  vgId;       // vg ID
+  int32_t  len;        // content length, does not include head
+  uint32_t cksum;
+} SSyncHead;
+
+typedef struct {
+  SSyncHead head;
+  uint16_t  port;
+  uint16_t  tranId;
+  int32_t   sourceId;  // only for arbitrator
+  char      fqdn[TSDB_FQDN_LEN];
+} SSyncMsg;
+
+typedef struct {
+  SSyncHead head;
+  int8_t    sync;
+  int8_t    reserved;
+  uint16_t  tranId;
+  int8_t    reserverd[4];
+} SSyncRsp;
+
+typedef struct {
+  int8_t    role;
+  uint64_t  version;
+} SPeerStatus;
+
+typedef struct {
+  SSyncHead   head;
+  int8_t      role;
+  int8_t      ack;
+  int8_t      type;
+  int8_t      reserved[3];
+  uint16_t    tranId;
+  uint64_t    version;
+  SPeerStatus peersStatus[TAOS_SYNC_MAX_REPLICA];
+} SPeersStatus;
+
+typedef struct {
+  SSyncHead head;
+  char      name[TSDB_FILENAME_LEN];
+  uint32_t  magic;
+  uint32_t  index;
+  uint64_t  fversion;
+  int64_t   size;
+} SFileInfo;
+
+typedef struct {
+  SSyncHead head;
+  int8_t    sync;
+} SFileAck;
+
+typedef struct {
+  SSyncHead head;
+  uint64_t  version;
+  int32_t   code;
+} SFwdRsp;
+
+#pragma pack(pop)
+
+#define SYNC_PROTOCOL_VERSION 0
+#define SYNC_SIGNATURE ((uint16_t)(0xCDEF))
+
+extern char *statusType[];
+
+uint16_t syncGenTranId();
+int32_t  syncCheckHead(SSyncHead *pHead);
+
+void syncBuildSyncFwdMsg(SSyncHead *pHead, int32_t vgId, int32_t len);
+void syncBuildSyncFwdRsp(SFwdRsp *pMsg, int32_t vgId, uint64_t version, int32_t code);
+void syncBuildSyncReqMsg(SSyncMsg *pMsg, int32_t vgId);
+void syncBuildSyncDataMsg(SSyncMsg *pMsg, int32_t vgId);
+void syncBuildSyncSetupMsg(SSyncMsg *pMsg, int32_t vgId);
+void syncBuildPeersStatus(SPeersStatus *pMsg, int32_t vgId);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  // TDENGINE_VNODEPEER_H
diff --git a/src/sync/src/syncMain.c b/src/sync/src/syncMain.c
index 5e3355e68f46d6dd7e0a76c0affefeeb55b52248..bf0b6e95d487c16b6a72221cc4ea5ee95c9e0824 100644
--- a/src/sync/src/syncMain.c
+++ b/src/sync/src/syncMain.c
@@ -80,32 +80,6 @@ char *syncStatus[] = {
   "invalid"
 };
 
-typedef enum {
-  SYNC_STATUS_BROADCAST,
-  SYNC_STATUS_BROADCAST_RSP,
-  SYNC_STATUS_SETUP_CONN,
-  SYNC_STATUS_SETUP_CONN_RSP,
-  SYNC_STATUS_EXCHANGE_DATA,
-  SYNC_STATUS_EXCHANGE_DATA_RSP,
-  SYNC_STATUS_CHECK_ROLE,
-  SYNC_STATUS_CHECK_ROLE_RSP
-} ESyncStatusType;
-
-char *statusType[] = {
-  "broadcast",
-  "broadcast-rsp",
-  "setup-conn",
-  "setup-conn-rsp",
-  "exchange-data",
-  "exchange-data-rsp",
-  "check-role",
-  "check-role-rsp"
-};
-
-uint16_t syncGenTranId() {
-  return taosRand() & 0XFFFF;
-}
-
 int32_t syncInit() {
   SPoolInfo info = {0};
 
@@ -384,19 +358,13 @@ void syncConfirmForward(int64_t rid, uint64_t version, int32_t code) {
 
   SSyncPeer *pPeer = pNode->pMaster;
   if (pPeer && pNode->quorum > 1) {
-    SFwdRsp fwdRsp = {0};
-
-    fwdRsp.head.type = TAOS_SMSG_FORWARD_RSP;
-    fwdRsp.head.protocol = SYNC_PROTOCOL_VERSION;
-    fwdRsp.head.vgId = pNode->vgId;
-    fwdRsp.head.len = sizeof(SFwdRsp) - sizeof(SSyncHead);
-    fwdRsp.version = version;
-    fwdRsp.code = code;
+    SFwdRsp rsp;
+    syncBuildSyncFwdRsp(&rsp, pNode->vgId, version, code);
 
-    if (taosWriteMsg(pPeer->peerFd, &fwdRsp, sizeof(SFwdRsp)) == sizeof(SFwdRsp)) {
-      sTrace("%s, forward-rsp is sent, code:%x hver:%" PRIu64, pPeer->id, code, version);
+    if (taosWriteMsg(pPeer->peerFd, &rsp, sizeof(SFwdRsp)) == sizeof(SFwdRsp)) {
+      sTrace("%s, forward-rsp is sent, code:0x%x hver:%" PRIu64, pPeer->id, code, version);
     } else {
-      sDebug("%s, failed to send forward ack, restart", pPeer->id);
+      sDebug("%s, failed to send forward-rsp, restart", pPeer->id);
       syncRestartConnection(pPeer);
     }
   }
@@ -864,14 +832,7 @@ static void syncRecoverFromMaster(SSyncPeer *pPeer) {
   sDebug("%s, try to sync", pPeer->id);
 
   SSyncMsg msg;
-  memset(&msg, 0, sizeof(SSyncMsg));
-  msg.head.type = TAOS_SMSG_SYNC_REQ;
-  msg.head.protocol = SYNC_PROTOCOL_VERSION;
-  msg.head.vgId = pNode->vgId;
-  msg.head.len = sizeof(SSyncMsg) - sizeof(SSyncHead);
-  msg.port = tsSyncPort;
-  msg.tranId = syncGenTranId();
-  tstrncpy(msg.fqdn, tsNodeFqdn, TSDB_FQDN_LEN);
+  syncBuildSyncReqMsg(&msg, pNode->vgId);
 
   taosTmrReset(syncNotStarted, tsSyncTimer * 1000, pPeer, tsSyncTmrCtrl, &pPeer->timer);
 
@@ -882,9 +843,8 @@ static void syncRecoverFromMaster(SSyncPeer *pPeer) {
   }
 }
 
-static void syncProcessFwdResponse(char *cont, SSyncPeer *pPeer) {
+static void syncProcessFwdResponse(SFwdRsp *pFwdRsp, SSyncPeer *pPeer) {
   SSyncNode *pNode = pPeer->pSyncNode;
-  SFwdRsp *  pFwdRsp = (SFwdRsp *)cont;
   SSyncFwds *pSyncFwds = pNode->pSyncFwds;
   SFwdInfo * pFwdInfo;
 
@@ -914,7 +874,7 @@ static void syncProcessFwdResponse(char *cont, SSyncPeer *pPeer) {
 
 static void syncProcessForwardFromPeer(char *cont, SSyncPeer *pPeer) {
   SSyncNode *pNode = pPeer->pSyncNode;
-  SWalHead * pHead = (SWalHead *)cont;
+  SWalHead * pHead = (SWalHead *)(cont + sizeof(SSyncHead));
 
   sTrace("%s, forward is received, hver:%" PRIu64 ", len:%d", pPeer->id, pHead->version, pHead->len);
 
@@ -931,9 +891,8 @@ static void syncProcessForwardFromPeer(char *cont, SSyncPeer *pPeer) {
   }
 }
 
-static void syncProcessPeersStatusMsg(char *cont, SSyncPeer *pPeer) {
-  SSyncNode *   pNode = pPeer->pSyncNode;
-  SPeersStatus *pPeersStatus = (SPeersStatus *)cont;
+static void syncProcessPeersStatusMsg(SPeersStatus *pPeersStatus, SSyncPeer *pPeer) {
+  SSyncNode *pNode = pPeer->pSyncNode;
 
   sDebug("%s, status is received, self:%s:%s:%" PRIu64 ", peer:%s:%" PRIu64 ", ack:%d tranId:%u type:%s pfd:%d",
          pPeer->id, syncRole[nodeRole], syncStatus[nodeSStatus], nodeVersion, syncRole[pPeersStatus->role],
@@ -947,23 +906,22 @@ static void syncProcessPeersStatusMsg(char *cont, SSyncPeer *pPeer) {
   }
 }
 
-static int32_t syncReadPeerMsg(SSyncPeer *pPeer, SSyncHead *pHead, char *cont) {
+static int32_t syncReadPeerMsg(SSyncPeer *pPeer, SSyncHead *pHead) {
   if (pPeer->peerFd < 0) return -1;
 
   int32_t hlen = taosReadMsg(pPeer->peerFd, pHead, sizeof(SSyncHead));
   if (hlen != sizeof(SSyncHead)) {
-    sDebug("%s, failed to read msg, hlen:%d", pPeer->id, hlen);
+    sDebug("%s, failed to read msg since %s, hlen:%d", pPeer->id, tstrerror(errno), hlen);
     return -1;
   }
 
-  // head.len = htonl(head.len);
-  if (pHead->len < 0) {
-    sError("%s, invalid msg length, hlen:%d", pPeer->id, pHead->len);
+  int32_t code = syncCheckHead(pHead);
+  if (code != 0) {
+    sError("%s, failed to check msg head since %s, type:%d", pPeer->id, tstrerror(code), pHead->type);
     return -1;
   }
 
-  assert(pHead->len <= TSDB_MAX_WAL_SIZE);
-  int32_t bytes = taosReadMsg(pPeer->peerFd, cont, pHead->len);
+  int32_t bytes = taosReadMsg(pPeer->peerFd, (char *)pHead + sizeof(SSyncHead), pHead->len);
   if (bytes != pHead->len) {
     sError("%s, failed to read, bytes:%d len:%d", pPeer->id, bytes, pHead->len);
     return -1;
@@ -974,23 +932,22 @@ static int32_t syncReadPeerMsg(SSyncPeer *pPeer, SSyncHead *pHead, char *cont) {
 
 static int32_t syncProcessPeerMsg(void *param, void *buffer) {
   SSyncPeer *pPeer = param;
-  SSyncHead  head;
-  char *     cont = buffer;
-
+  SSyncHead *pHead = buffer;
   SSyncNode *pNode = pPeer->pSyncNode;
+  
   pthread_mutex_lock(&pNode->mutex);
 
-  int32_t code = syncReadPeerMsg(pPeer, &head, cont);
+  int32_t code = syncReadPeerMsg(pPeer, pHead);
 
   if (code == 0) {
-    if (head.type == TAOS_SMSG_FORWARD) {
-      syncProcessForwardFromPeer(cont, pPeer);
-    } else if (head.type == TAOS_SMSG_FORWARD_RSP) {
-      syncProcessFwdResponse(cont, pPeer);
-    } else if (head.type == TAOS_SMSG_SYNC_REQ) {
-      syncProcessSyncRequest(cont, pPeer);
-    } else if (head.type == TAOS_SMSG_STATUS) {
-      syncProcessPeersStatusMsg(cont, pPeer);
+    if (pHead->type == TAOS_SMSG_SYNC_FWD) {
+      syncProcessForwardFromPeer(buffer, pPeer);
+    } else if (pHead->type == TAOS_SMSG_SYNC_FWD_RSP) {
+      syncProcessFwdResponse(buffer, pPeer);
+    } else if (pHead->type == TAOS_SMSG_SYNC_REQ) {
+      syncProcessSyncRequest(buffer, pPeer);
+    } else if (pHead->type == TAOS_SMSG_STATUS) {
+      syncProcessPeersStatusMsg(buffer, pPeer);
     }
   }
 
@@ -999,36 +956,29 @@ static int32_t syncProcessPeerMsg(void *param, void *buffer) {
   return code;
 }
 
-#define statusMsgLen sizeof(SSyncHead) + sizeof(SPeersStatus) + sizeof(SPeerStatus) * TAOS_SYNC_MAX_REPLICA
-
 static void syncSendPeersStatusMsgToPeer(SSyncPeer *pPeer, char ack, int8_t type, uint16_t tranId) {
-  SSyncNode *pNode = pPeer->pSyncNode;
-  char       msg[statusMsgLen] = {0};
-
   if (pPeer->peerFd < 0 || pPeer->ip == 0) return;
 
-  SSyncHead *   pHead = (SSyncHead *)msg;
-  SPeersStatus *pPeersStatus = (SPeersStatus *)(msg + sizeof(SSyncHead));
+  SSyncNode *pNode = pPeer->pSyncNode;
+  SPeersStatus msg = {0};
 
-  pHead->type = TAOS_SMSG_STATUS;
-  pHead->len = statusMsgLen - sizeof(SSyncHead);
+  syncBuildPeersStatus(&msg, pNode->vgId);
 
-  pPeersStatus->version = nodeVersion;
-  pPeersStatus->role = nodeRole;
-  pPeersStatus->ack = ack;
-  pPeersStatus->type = type;
-  pPeersStatus->tranId = tranId;
+  msg.role = nodeRole;
+  msg.ack = ack;
+  msg.type = type;
+  msg.tranId = tranId;
+  msg.version = nodeVersion;
 
   for (int32_t i = 0; i < pNode->replica; ++i) {
-    pPeersStatus->peersStatus[i].role = pNode->peerInfo[i]->role;
-    pPeersStatus->peersStatus[i].version = pNode->peerInfo[i]->version;
+    msg.peersStatus[i].role = pNode->peerInfo[i]->role;
+    msg.peersStatus[i].version = pNode->peerInfo[i]->version;
   }
 
-  if (taosWriteMsg(pPeer->peerFd, msg, statusMsgLen) == statusMsgLen) {
+  if (taosWriteMsg(pPeer->peerFd, &msg, sizeof(SPeersStatus)) == sizeof(SPeersStatus)) {
     sDebug("%s, status is sent, self:%s:%s:%" PRIu64 ", peer:%s:%s:%" PRIu64 ", ack:%d tranId:%u type:%s pfd:%d",
            pPeer->id, syncRole[nodeRole], syncStatus[nodeSStatus], nodeVersion, syncRole[pPeer->role],
-           syncStatus[pPeer->sstatus], pPeer->version, pPeersStatus->ack, pPeersStatus->tranId,
-           statusType[pPeersStatus->type], pPeer->peerFd);
+           syncStatus[pPeer->sstatus], pPeer->version, ack, tranId, statusType[type], pPeer->peerFd);
   } else {
     sDebug("%s, failed to send status msg, restart", pPeer->id);
     syncRestartConnection(pPeer);
@@ -1053,15 +1003,7 @@ static void syncSetupPeerConnection(SSyncPeer *pPeer) {
   }
 
   SSyncMsg msg;
-  memset(&msg, 0, sizeof(SSyncMsg));
-  msg.head.type = TAOS_SMSG_STATUS;
-  msg.head.protocol = SYNC_PROTOCOL_VERSION;
-  msg.head.vgId = pPeer->nodeId ? pNode->vgId : 0;
-  msg.head.len = sizeof(SSyncMsg) - sizeof(SSyncHead);
-  msg.port = tsSyncPort;
-  msg.tranId = syncGenTranId();
-  msg.sourceId = pNode->vgId;  // tell arbitrator its vgId
-  tstrncpy(msg.fqdn, tsNodeFqdn, TSDB_FQDN_LEN);
+  syncBuildSyncSetupMsg(&msg, pPeer->nodeId ? pNode->vgId : 0);
 
   if (taosWriteMsg(connFd, &msg, sizeof(SSyncMsg)) == sizeof(SSyncMsg)) {
     sDebug("%s, connection to peer server is setup, pfd:%d sfd:%d tranId:%u", pPeer->id, connFd, pPeer->syncFd, msg.tranId);
@@ -1341,10 +1283,7 @@ static int32_t syncForwardToPeerImpl(SSyncNode *pNode, void *data, void *mhandle
 
     // a hacker way to improve the performance
   pSyncHead = (SSyncHead *)(((char *)pWalHead) - sizeof(SSyncHead));
-  pSyncHead->type = TAOS_SMSG_FORWARD;
-  pSyncHead->protocol = SYNC_PROTOCOL_VERSION;
-  pSyncHead->vgId = pNode->vgId;
-  pSyncHead->len = sizeof(SWalHead) + pWalHead->len;
+  syncBuildSyncFwdMsg(pSyncHead, pNode->vgId, sizeof(SWalHead) + pWalHead->len);
   fwdLen = pSyncHead->len + sizeof(SSyncHead);  // include the WAL and SYNC head
 
   pthread_mutex_lock(&pNode->mutex);
diff --git a/src/sync/src/syncMsg.c b/src/sync/src/syncMsg.c
new file mode 100644
index 0000000000000000000000000000000000000000..dafefc77baab736be646651d6e504d83553a3029
--- /dev/null
+++ b/src/sync/src/syncMsg.c
@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <jhtao@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#define _DEFAULT_SOURCE
+#include "os.h"
+#include "taoserror.h"
+#include "tchecksum.h"
+#include "syncInt.h"
+
+char *statusType[] = {
+  "broadcast",
+  "broadcast-rsp",
+  "setup-conn",
+  "setup-conn-rsp",
+  "exchange-data",
+  "exchange-data-rsp",
+  "check-role",
+  "check-role-rsp"
+};
+
+uint16_t syncGenTranId() {
+  return taosRand() & 0XFFFF;
+}
+
+static void syncBuildHead(SSyncHead *pHead) {
+  pHead->protocol = SYNC_PROTOCOL_VERSION;
+  pHead->signature = SYNC_SIGNATURE;
+  pHead->code = 0;
+  pHead->cId = 0;
+  taosCalcChecksumAppend(0, (uint8_t *)pHead, sizeof(SSyncHead));
+}
+
+int32_t syncCheckHead(SSyncHead *pHead) {
+  if (pHead->protocol != SYNC_PROTOCOL_VERSION) return TSDB_CODE_SYN_MISMATCHED_PROTOCOL;
+  if (pHead->signature != SYNC_SIGNATURE) return TSDB_CODE_SYN_MISMATCHED_SIGNATURE;
+  if (pHead->cId != 0) return TSDB_CODE_SYN_MISMATCHED_CLUSTERID;
+  if (pHead->len <= 0 || pHead->len > TSDB_MAX_WAL_SIZE) return TSDB_CODE_SYN_INVALID_MSGLEN;
+  if (!taosCheckChecksumWhole((uint8_t *)pHead, sizeof(SSyncHead))) return TSDB_CODE_SYN_INVALID_CHECKSUM;
+
+  return TSDB_CODE_SUCCESS;
+}
+
+void syncBuildSyncFwdMsg(SSyncHead *pHead, int32_t vgId, int32_t len) {
+  pHead->type = TAOS_SMSG_SYNC_FWD;
+  pHead->vgId = vgId;
+  pHead->len = len;
+  syncBuildHead(pHead);
+}
+
+void syncBuildSyncFwdRsp(SFwdRsp *pMsg, int32_t vgId, uint64_t version, int32_t code) {
+  pMsg->head.type = TAOS_SMSG_SYNC_FWD_RSP;
+  pMsg->head.vgId = vgId;
+  pMsg->head.len = sizeof(SFwdRsp) - sizeof(SSyncHead);
+  syncBuildHead(&pMsg->head);
+
+  pMsg->version = version;
+  pMsg->code = code;
+}
+
+static void syncBuildMsg(SSyncMsg *pMsg, int32_t vgId, ESyncMsgType type) {
+  pMsg->head.type = type;
+  pMsg->head.vgId = vgId;
+  pMsg->head.len = sizeof(SSyncMsg) - sizeof(SSyncHead);
+  syncBuildHead(&pMsg->head);
+
+  pMsg->port = tsSyncPort;
+  pMsg->tranId = syncGenTranId();
+  pMsg->sourceId = vgId;
+  tstrncpy(pMsg->fqdn, tsNodeFqdn, TSDB_FQDN_LEN);
+}
+
+void syncBuildSyncReqMsg(SSyncMsg *pMsg, int32_t vgId) { syncBuildMsg(pMsg, vgId, TAOS_SMSG_SYNC_REQ); }
+void syncBuildSyncDataMsg(SSyncMsg *pMsg, int32_t vgId) { syncBuildMsg(pMsg, vgId, TAOS_SMSG_SYNC_DATA); }
+void syncBuildSyncSetupMsg(SSyncMsg *pMsg, int32_t vgId) { syncBuildMsg(pMsg, vgId, TAOS_SMSG_SETUP); }
+
+void syncBuildPeersStatus(SPeersStatus *pMsg, int32_t vgId) {
+  pMsg->head.type = TAOS_SMSG_STATUS;
+  pMsg->head.vgId = vgId;
+  pMsg->head.len = sizeof(SPeersStatus) - sizeof(SSyncHead);
+  syncBuildHead(&pMsg->head);
+}
diff --git a/src/sync/src/syncRetrieve.c b/src/sync/src/syncRetrieve.c
index 981716d5615d9375a3a741f1f09195abc8dcbe0a..204f4f90367c2038e40b41d7ab206c579d31b3d6 100644
--- a/src/sync/src/syncRetrieve.c
+++ b/src/sync/src/syncRetrieve.c
@@ -406,14 +406,7 @@ static int32_t syncRetrieveFirstPkt(SSyncPeer *pPeer) {
   SSyncNode *pNode = pPeer->pSyncNode;
 
   SSyncMsg msg;
-  memset(&msg, 0, sizeof(SSyncMsg));
-  msg.head.type = TAOS_SMSG_SYNC_DATA;
-  msg.head.protocol = SYNC_PROTOCOL_VERSION;
-  msg.head.vgId = pNode->vgId;
-  msg.head.len = sizeof(SSyncMsg) - sizeof(SSyncHead);
-  msg.port = tsSyncPort;
-  msg.tranId = syncGenTranId();
-  tstrncpy(msg.fqdn, tsNodeFqdn, TSDB_FQDN_LEN);
+  syncBuildSyncDataMsg(&msg, pNode->vgId);
 
   if (taosWriteMsg(pPeer->syncFd, &msg, sizeof(SSyncMsg)) != sizeof(SSyncMsg)) {
     sError("%s, failed to send sync-data msg since %s, tranId:%u", pPeer->id, strerror(errno), msg.tranId);