diff --git a/UDPspeeder b/UDPspeeder
index 9a622ce..8db00a8 160000
--- a/UDPspeeder
+++ b/UDPspeeder
@@ -1 +1 @@
-Subproject commit 9a622ce463710925181fde5a2d0fe249780b8e1d
+Subproject commit 8db00a87f433d174f3bdabaf95f8659c66a1c52e
diff --git a/main.cpp b/main.cpp
index 0989fad..cd1e9eb 100644
--- a/main.cpp
+++ b/main.cpp
@@ -34,37 +34,43 @@ static void print_help()
 	printf("    --tun-dev             <number>        sepcify tun device name, for example: tun10, default: a random name such as tun987\n");
 	printf("    -f,--fec              x:y             forward error correction, send y redundant packets for every x packets\n");
 	printf("    --timeout             <number>        how long could a packet be held in queue before doing fec, unit: ms, default: 8ms\n");
-	printf("    --mode                <number>        fec-mode,available values: 0, 1; 0 cost less bandwidth, 1 cost less latency;default: 0)\n");
 	printf("    --report              <number>        turn on send/recv report, and set a period for reporting, unit: s\n");
 	printf("    --keep-reconnect                      re-connect after lost connection,only for client. \n");
 
 
 	printf("advanced options:\n");
+	printf("    --mode                <number>        fec-mode,available values: 0,1; mode 0(default) costs less bandwidth,no mtu problem.\n");
+	printf("                                          mode 1 usually introduces less latency, but you have to care about mtu.\n");
 	printf("    --mtu                 <number>        mtu for fec. for mode 0, the program will split packet to segment smaller than mtu.\n");
 	printf("                                          for mode 1, no packet will be split, the program just check if the mtu is exceed.\n");
 	printf("                                          default value: 1250\n");
 	printf("    -j,--jitter           <number>        simulated jitter. randomly delay first packet for 0~<number> ms, default value: 0.\n");
 	printf("                                          do not use if you dont know what it means.\n");
-	printf("    -i,--interval         <number>        scatter each fec group to a interval of <number> ms, to protect burst packet loss.\n");
+	printf("    -i,--interval         <number>        scatter each fec group to a interval of <number> ms, to defend burst packet loss.\n");
 	printf("                                          default value: 0. do not use if you dont know what it means.\n");
+	printf("    -f,--fec              x1:y1,x2:y2,..  similiar to -f/--fec above,fine-grained fec parameters,may help save bandwidth.\n");
+	printf("                                          example: \"-f 1:3,2:4,10:6,20:10\". check repo for details\n");
 	printf("    --random-drop         <number>        simulate packet loss, unit: 0.01%%. default value: 0\n");
 	printf("    --disable-obscure     <number>        disable obscure, to save a bit bandwidth and cpu\n");
 	printf("    --disable-checksum    <number>        disable checksum to save a bit bandwdith and cpu\n");
-	printf("    --disable-xor         <number>        disable xor encryption to save a bit cpu\n");
+	//printf("    --disable-xor         <number>        disable xor\n");
+	printf("    --persist-tun         <number>        make the tun device persistent, so that it wont be deleted after exited.\n");
+	printf("    --mssfix              <number>        do mssfix for tcp connection, use 0 to disable. default value: 1250\n");
 
 	printf("developer options:\n");
 	printf("    --tun-mtu             <number>        mtu of the tun interface,most time you shouldnt change this\n");
-	printf("    --mssfix              <number>        do mssfix for tcp connection, use 0 to disable. default value: 1250\n");
-	printf("    -i,--interval         imin:imax       similiar to -i above, but scatter randomly between imin and imax\n");
+	printf("    --manual-set-tun      <number>        tell tinyfecvpn to not setup the tun device automatically(e.g. assign ip address),\n");
+	printf("                                          so that you can do it manually later\n");
 	printf("    --fifo                <string>        use a fifo(named pipe) for sending commands to the running program, so that you\n");
 	printf("                                          can change fec encode parameters dynamically, check readme.md in repository for\n");
 	printf("                                          supported commands.\n");
 	printf("    -j ,--jitter          jmin:jmax       similiar to -j above, but create jitter randomly between jmin and jmax\n");
 	printf("    -i,--interval         imin:imax       similiar to -i above, but scatter randomly between imin and imax\n");
-    printf("    -q,--queue-len        <number>        max fec queue len, only for mode 0\n");
+    printf("    -q,--queue-len        <number>        fec queue len, only for mode 0, fec will be performed immediately after queue is full.\n");
+	printf("                                          default value: 200. \n");
     printf("    --decode-buf          <number>        size of buffer of fec decoder,u nit: packet, default: 2000\n");
-    printf("    --fix-latency         <number>        try to stabilize latency, only for mode 0\n");
-    printf("    --delay-capacity      <number>        max number of delayed packets\n");
+//    printf("    --fix-latency         <number>        try to stabilize latency, only for mode 0\n");
+    printf("    --delay-capacity      <number>        max number of delayed packets, 0 means unlimited, default: 0\n");
 	printf("    --disable-fec         <number>        completely disable fec, turn the program into a normal udp tunnel\n");
 	printf("    --sock-buf            <number>        buf size for socket, >=10 and <=10240, unit: kbyte, default: 1024\n");
 	printf("log and help options:\n");