diff --git a/doc/protocol.md b/doc/protocol.md
index addb917..29622e2 100644
--- a/doc/protocol.md
+++ b/doc/protocol.md
@@ -7,6 +7,57 @@ All messages begins with `P2P-JAVA-PROJECT VERSION 1.0\n` (this version of the p
 
 ## Server responses
 - The response to `LIST` request is in the format `LIST\n<FILENAME 1>\n<FILENAME 2>\n[…]<LAST FILENAME>\n\n`
-- The response to `DOWNLOAD` request is `LOAD\n<FILESIZE (BYTES)>\n<CONTENT OF FILE>` or `NOT FOUND\n` if the file doesn't exists.
+- The response to `DOWNLOAD` request is `LOAD\n<FILESIZE (BYTES)>\n<POSITION>\n<CONTENT OF FILE>` or `NOT FOUND\n` if the file doesn't exists.
 - The server send a `PROTOCOL ERROR\n` message if it doesn't understands what the client sent.
 - The server send a `INTERNAL ERROR\n` message if it encounters an internal error.
+
+# P2P-JAVA-PROJECT version 1.1 (Binary protocol for step 1)
+
+```Datagram format
+
+[0-7: VERSION(0x11, first quartet is major version, second is minor)]
+[8-15: REQUEST/RESPONSE CODE]
+[16-31: RESERVED FOR FUTURE USE]
+[32-63: PAYLOAD SIZE IN BYTES]
+[64-xx: PAYLOAD]
+
+```
+
+## Requests and responses codes
+- REQUESTS (msb is 0):
+	- `LIST` (0x00)
+	- `DOWNLOAD` (0x01)
+
+- RESPONSES (msb is 1):
+	- `LIST` (0x80)
+	- `LOAD` (0x81)
+	- `NOT FOUND` (0x82)
+	- `PROTOCOL ERROR` (0x83)
+	- `INTERNAL ERROR` (0x84)
+
+### List
+Payload size for list request is always zero.
+Payload for list response is filenames separated by `\n`.
+
+### Download
+#### Not found
+Response when the file requested is not found on the server.
+Payload size for Not found is zero
+
+#### Protocol error
+Response when the request cannot be interpreted.
+Payload size for Protocol error is zero
+
+#### Internal error
+Response in internal failure case.
+Payload size for Internal error is zero
+
+#### Load response
+Payload contains
+
+```
+[64-127: OFFSET OF FILE CONTENT IN BYTES]
+[128-159: TOTAL FILESIZE]
+[<FILENAME>\n]
+[FILE CONTENT]
+```