diff --git a/net/colo-compare.c b/net/colo-compare.c
index cea9b27..cafd5e3 100644
--- a/net/colo-compare.c
+++ b/net/colo-compare.c
@@ -33,6 +33,8 @@
 #define COLO_COMPARE(obj) \
     OBJECT_CHECK(CompareState, (obj), TYPE_COLO_COMPARE)
 
+#define MAX_QUEUE_SIZE 1024
+
 /*
   + CompareState ++
   |               |
@@ -67,6 +69,11 @@ typedef struct CompareState {
     SocketReadState pri_rs;
     SocketReadState sec_rs;
 
+    /* connection list: the connections belonged to this NIC could be found
+     * in this list.
+     * element type: Connection
+     */
+    GQueue conn_list;
     /* hashtable to save connection */
     GHashTable *connection_track_table;
 } CompareState;
@@ -94,7 +101,9 @@ static int compare_chr_send(CharDriverState *out,
  */
 static int packet_enqueue(CompareState *s, int mode)
 {
+    ConnectionKey key = {{0},};
     Packet *pkt = NULL;
+    Connection *conn;
 
     if (mode == PRIMARY_IN) {
         pkt = packet_new(s->pri_rs.buf, s->pri_rs.packet_len);
@@ -107,17 +116,34 @@ static int packet_enqueue(CompareState *s, int mode)
         pkt = NULL;
         return -1;
     }
-    /* TODO: get connection key from pkt */
+    fill_connection_key(pkt, &key);
 
-    /*
-     * TODO: use connection key get conn from
-     * connection_track_table
-     */
+    conn = connection_get(s->connection_track_table,
+                          &key,
+                          &s->conn_list);
 
-    /*
-     * TODO: insert pkt to it's conn->primary_list
-     * or conn->secondary_list
-     */
+    if (!conn->processing) {
+        g_queue_push_tail(&s->conn_list, conn);
+        conn->processing = true;
+    }
+
+    if (mode == PRIMARY_IN) {
+        if (g_queue_get_length(&conn->primary_list) <=
+                               MAX_QUEUE_SIZE) {
+            g_queue_push_tail(&conn->primary_list, pkt);
+        } else {
+            error_report("colo compare primary queue size too big,"
+                         "drop packet");
+        }
+    } else {
+        if (g_queue_get_length(&conn->secondary_list) <=
+                               MAX_QUEUE_SIZE) {
+            g_queue_push_tail(&conn->secondary_list, pkt);
+        } else {
+            error_report("colo compare secondary queue size too big,"
+                         "drop packet");
+        }
+    }
 
     return 0;
 }
@@ -308,7 +334,12 @@ static void colo_compare_complete(UserCreatable *uc, Error **errp)
     net_socket_rs_init(&s->pri_rs, compare_pri_rs_finalize);
     net_socket_rs_init(&s->sec_rs, compare_sec_rs_finalize);
 
-    /* use g_hash_table_new_full() to new a hashtable */
+    g_queue_init(&s->conn_list);
+
+    s->connection_track_table = g_hash_table_new_full(connection_key_hash,
+                                                      connection_key_equal,
+                                                      g_free,
+                                                      connection_destroy);
 
     return;
 }
@@ -349,6 +380,8 @@ static void colo_compare_finalize(Object *obj)
         qemu_chr_fe_release(s->chr_out);
     }
 
+    g_queue_free(&s->conn_list);
+
     g_free(s->pri_indev);
     g_free(s->sec_indev);
     g_free(s->outdev);
diff --git a/net/colo.c b/net/colo.c
index 8582175..13a8090 100644
--- a/net/colo.c
+++ b/net/colo.c
@@ -16,6 +16,29 @@
 #include "trace.h"
 #include "net/colo.h"
 
+uint32_t connection_key_hash(const void *opaque)
+{
+    const ConnectionKey *key = opaque;
+    uint32_t a, b, c;
+
+    /* Jenkins hash */
+    a = b = c = JHASH_INITVAL + sizeof(*key);
+    a += key->src.s_addr;
+    b += key->dst.s_addr;
+    c += (key->src_port | key->dst_port << 16);
+    __jhash_mix(a, b, c);
+
+    a += key->ip_proto;
+    __jhash_final(a, b, c);
+
+    return c;
+}
+
+int connection_key_equal(const void *key1, const void *key2)
+{
+    return memcmp(key1, key2, sizeof(ConnectionKey)) == 0;
+}
+
 int parse_packet_early(Packet *pkt)
 {
     int network_length;
@@ -59,6 +82,62 @@ int parse_packet_early(Packet *pkt)
     return 0;
 }
 
+void fill_connection_key(Packet *pkt, ConnectionKey *key)
+{
+    uint32_t tmp_ports;
+
+    key->ip_proto = pkt->ip->ip_p;
+
+    switch (key->ip_proto) {
+    case IPPROTO_TCP:
+    case IPPROTO_UDP:
+    case IPPROTO_DCCP:
+    case IPPROTO_ESP:
+    case IPPROTO_SCTP:
+    case IPPROTO_UDPLITE:
+        tmp_ports = *(uint32_t *)(pkt->transport_header);
+        key->src = pkt->ip->ip_src;
+        key->dst = pkt->ip->ip_dst;
+        key->src_port = ntohs(tmp_ports & 0xffff);
+        key->dst_port = ntohs(tmp_ports >> 16);
+        break;
+    case IPPROTO_AH:
+        tmp_ports = *(uint32_t *)(pkt->transport_header + 4);
+        key->src = pkt->ip->ip_src;
+        key->dst = pkt->ip->ip_dst;
+        key->src_port = ntohs(tmp_ports & 0xffff);
+        key->dst_port = ntohs(tmp_ports >> 16);
+        break;
+    default:
+        key->src_port = 0;
+        key->dst_port = 0;
+        break;
+    }
+}
+
+Connection *connection_new(ConnectionKey *key)
+{
+    Connection *conn = g_slice_new(Connection);
+
+    conn->ip_proto = key->ip_proto;
+    conn->processing = false;
+    g_queue_init(&conn->primary_list);
+    g_queue_init(&conn->secondary_list);
+
+    return conn;
+}
+
+void connection_destroy(void *opaque)
+{
+    Connection *conn = opaque;
+
+    g_queue_foreach(&conn->primary_list, packet_destroy, NULL);
+    g_queue_free(&conn->primary_list);
+    g_queue_foreach(&conn->secondary_list, packet_destroy, NULL);
+    g_queue_free(&conn->secondary_list);
+    g_slice_free(Connection, conn);
+}
+
 Packet *packet_new(const void *data, int size)
 {
     Packet *pkt = g_slice_new(Packet);
@@ -84,3 +163,33 @@ void connection_hashtable_reset(GHashTable *connection_track_table)
 {
     g_hash_table_remove_all(connection_track_table);
 }
+
+/* if not found, create a new connection and add to hash table */
+Connection *connection_get(GHashTable *connection_track_table,
+                           ConnectionKey *key,
+                           GQueue *conn_list)
+{
+    Connection *conn = g_hash_table_lookup(connection_track_table, key);
+
+    if (conn == NULL) {
+        ConnectionKey *new_key = g_memdup(key, sizeof(*key));
+
+        conn = connection_new(key);
+
+        if (g_hash_table_size(connection_track_table) > HASHTABLE_MAX_SIZE) {
+            trace_colo_proxy_main("colo proxy connection hashtable full,"
+                                  " clear it");
+            connection_hashtable_reset(connection_track_table);
+            /*
+             * clear the conn_list
+             */
+            while (!g_queue_is_empty(conn_list)) {
+                connection_destroy(g_queue_pop_head(conn_list));
+            }
+        }
+
+        g_hash_table_insert(connection_track_table, new_key, conn);
+    }
+
+    return conn;
+}
diff --git a/net/colo.h b/net/colo.h
index 05dc0b6..c511bcd 100644
--- a/net/colo.h
+++ b/net/colo.h
@@ -20,6 +20,18 @@
 
 #define HASHTABLE_MAX_SIZE 16384
 
+#ifndef IPPROTO_DCCP
+#define IPPROTO_DCCP 33
+#endif
+
+#ifndef IPPROTO_SCTP
+#define IPPROTO_SCTP 132
+#endif
+
+#ifndef IPPROTO_UDPLITE
+#define IPPROTO_UDPLITE 136
+#endif
+
 typedef struct Packet {
     void *data;
     union {
@@ -30,7 +42,34 @@ typedef struct Packet {
     int size;
 } Packet;
 
+typedef struct ConnectionKey {
+    /* (src, dst) must be grouped, in the same way than in IP header */
+    struct in_addr src;
+    struct in_addr dst;
+    uint16_t src_port;
+    uint16_t dst_port;
+    uint8_t ip_proto;
+} QEMU_PACKED ConnectionKey;
+
+typedef struct Connection {
+    /* connection primary send queue: element type: Packet */
+    GQueue primary_list;
+    /* connection secondary send queue: element type: Packet */
+    GQueue secondary_list;
+    /* flag to enqueue unprocessed_connections */
+    bool processing;
+    uint8_t ip_proto;
+} Connection;
+
+uint32_t connection_key_hash(const void *opaque);
+int connection_key_equal(const void *opaque1, const void *opaque2);
 int parse_packet_early(Packet *pkt);
+void fill_connection_key(Packet *pkt, ConnectionKey *key);
+Connection *connection_new(ConnectionKey *key);
+void connection_destroy(void *opaque);
+Connection *connection_get(GHashTable *connection_track_table,
+                           ConnectionKey *key,
+                           GQueue *conn_list);
 void connection_hashtable_reset(GHashTable *connection_track_table);
 Packet *packet_new(const void *data, int size);
 void packet_destroy(void *opaque, void *user_data);
