Changeset 11163 for dotorg/trunk/html/beps/bep_0029.rst

Timestamp:

06/25/09 11:05:57 (9 months ago)

Author:

arvid

Message:

added handshake diagram

Files:

• dotorg/trunk/html/beps/bep_0029.rst (modified) (3 diffs)

dotorg/trunk/html/beps/bep_0029.rst

@@ -44 +44 @@
 The main drawbacks with this solution are:
 
-1. The user needs to configure his/her BitTorrent client, it won't
+#. The user needs to configure his/her BitTorrent client, it won't
    work out-of-the-box.
-2. The user needs to know his/her internet connection's upload
+#. The user needs to know his/her internet connection's upload
    capacity. This capacity may change, especially on laptops that
    may connect to a large number of different networks.
-3. The headroom of 20% is arbitrary and wastes bandwidth. Whenever
+#. The headroom of 20% is arbitrary and wastes bandwidth. Whenever
    there is no interactive traffic competing with BitTorrent, the
    extra 20% are wasted. Whenever there is competing interactive
@@ -253 +253 @@
 
 ST_STATE = 2
-        State packet. Used to transmit an ACK with no data.
+        State packet. Used to transmit an ACK with no data. Packets that don't
+        include any payload do not increase the ``seq_nr``.
 
 ST_RESET = 3
@@ -290 +291 @@
 ----------------
 
-*describe the initial connection setup sequence*
+Here is a diagram illustrating the exchanges and states to initiate
+a connection. The c.* refers to a state in the socket itself, pkt.*
+refers to a field in the packet header.
+
+::
+
+   initiating endpoint                           accepting endpoint     
+
+             | c.state = CS_SYN_SENT                         |
+             | c.seq_nr = 1                                  |
+             | c.conn_id_recv = rand()                       |
+             | c.conn_id_send = c.conn_id_recv + 1           |
+             |                                               |
+             |                                               |
+             | ST_SYN                                        |
+             |   seq_nr=c.seq_nr++                           |
+             |   ack_nr=*                                    |
+             |   conn_id=c.rcv_conn_id                       |
+             | >-------------------------------------------> | 
+             |             c.receive_conn_id = pkt.conn_id+1 | 
+             |             c.send_conn_id = pkt.conn_id      | 
+             |             c.seq_nr = rand()                 | 
+             |             c.ack_nr = pkt.seq_nr             |
+             |             c.state = CS_CONNECTED            |
+             |                                               |
+             |                                               |
+             |                                               |
+             |                                               |
+             |                     ST_STATE                  |
+             |                       seq_nr=c.seq_nr++       |
+             |                       ack_nr=c.ack_nr         |
+             |                       conn_id=c.send_conn_id  |
+             | <------------------------------------------<  |
+             | c.state = CS_CONNECTED                        |
+             | c.ack_nr = pkt.seq_nr                         |
+             |                                               |
+             |                                               | connection established
+        .. ..|.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ..|.. ..
+             |                                               |
+             |                                               |
+             | ST_DATA                                       |
+             |   seq_nr=c.seq_nr++                           |
+             |   ack_nr=c.ack_nr                             |
+             |   conn_id=c.conn_id_send                      |
+             | >-------------------------------------------> | 
+             |                         c.ack_nr = pkt.seq_nr |
+             |                                               |
+             |                                               |
+             |                                               |
+             |                     ST_DATA                   |
+             |                       seq_nr=c.seq_nr++       |
+             |                       ack_nr=c.ack_nr         |
+             |                       conn_id=c.send_conn_id  |
+             | <------------------------------------------<  |
+             | c.ack_nr = pkt.seq_nr                         |
+             |                                               |
+             |                                               |
+             V                                               V
+
 
 packet loss