[or-cvs] bring docs closer to reality

[Roger Dingledine]

Update of /home/or/cvsroot/doc
In directory moria.mit.edu:/home/arma/work/onion/cvs/doc

Modified Files:
	FAQ HACKING tor-spec.txt 
Log Message:
bring docs closer to reality


Index: FAQ
===================================================================
RCS file: /home/or/cvsroot/doc/FAQ,v
retrieving revision 1.2
retrieving revision 1.3
diff -u -d -r1.2 -r1.3
--- FAQ	19 Mar 2003 22:44:29 -0000	1.2
+++ FAQ	5 Apr 2003 19:04:05 -0000	1.3
@@ -38,17 +38,16 @@
 
 3. Running tor.
 
-3.1. What's this about roles? What kind of server should I run?
+3.1. What kind of server should I run?
 
 The same executable ("or") functions as both client and server, depending
-on the value of the config variable named 'Role'. Role represents a
-combination of which tasks this particular tor server will do. The default
-Role (role 15) is an onion router: it listens for onion routers, listens
-for onion proxies, listens for application proxies, and it connects to
-all other onion routers it learns about. A directory server (role 63)
-does all of the above and also serves directory requests. A simple
-onion proxy, on the other hand (role 8), only listens for application
-proxies. See part 3.1 of the HACKING document for more technical details.
+on which ports are specified in the configuration file. You can specify:
+* APPort: client applications (eg privoxy, Mozilla) can speak socks to
+  this port.
+* OPPort: onion proxies (client onion routers) connect to this port.
+* ORPort: other onion routers connect to this port
+* DirPort: onion proxies and onion routers speak http to this port, to
+  pull down a directory of which nodes are currently available.
 
 3.2. So I can just run a full onion router and join the network?
 

Index: HACKING
===================================================================
RCS file: /home/or/cvsroot/doc/HACKING,v
retrieving revision 1.1
retrieving revision 1.2
diff -u -d -r1.1 -r1.2
--- HACKING	18 Mar 2003 03:28:03 -0000	1.1
+++ HACKING	5 Apr 2003 19:04:05 -0000	1.2
@@ -8,16 +8,20 @@
 
 1. The programs.
 
-1.1. "or". This is the main program here. It functions as both a server
-and a client, depending on which config file you give it. ...
+1.1. "or". This is the main program here. It functions as either a server
+or a client, depending on which config file you give it.
+
+1.2. "orkeygen". Use "orkeygen file-for-privkey file-for-pubkey" to
+generate key files for an onion router.
 
 2. The pieces.
 
 2.1. Routers. Onion routers, as far as the 'or' program is concerned,
 are a bunch of data items that are loaded into the router_array when
-the program starts. After it's loaded, the router information is never
-changed. When a new OR connection is started (see below), the relevant
-information is copied from the router struct to the connection struct.
+the program starts. Periodically it downloads a new set of routers
+from a directory server, and updates the router_array. When a new OR
+connection is started (see below), the relevant information is copied
+from the router struct to the connection struct.
 
 2.2. Connections. A connection is a long-standing tcp socket between
 nodes. A connection is named based on what it's connected to -- an "OR
@@ -26,34 +30,36 @@
 other server on the other end, and an "AP connection" has an application
 proxy (and thus a user) on the other end.
 
-2.3. Circuits. A circuit is a single conversation between two
-participants over the onion routing network. One end of the circuit has
-an AP connection, and the other end has an exit connection. AP and exit
+2.3. Circuits. A circuit is a path over the onion routing
+network. Applications can connect to one end of the circuit, and can
+create exit connections at the other end of the circuit. AP and exit
 connections have only one circuit associated with them (and thus these
 connection types are closed when the circuit is closed), whereas OP and
 OR connections multiplex many circuits at once, and stay standing even
 when there are no circuits running over them.
 
+2.4. Topics. Topics are specific conversations between an AP and an exit.
+Topics are multiplexed over circuits.
+
 2.4. Cells. Some connections, specifically OR and OP connections, speak
-"cells". This means that data over that connection is bundled into 128
-byte packets (8 bytes of header and 120 bytes of payload). Each cell has
+"cells". This means that data over that connection is bundled into 256
+byte packets (8 bytes of header and 248 bytes of payload). Each cell has
 a type, or "command", which indicates what it's for.
 
 
 3. Important parameters in the code.
 
-3.1. Role.
 
 
 4. Robustness features.
 
 4.1. Bandwidth throttling. Each cell-speaking connection has a maximum
 bandwidth it can use, as specified in the routers.or file. Bandwidth
-throttling occurs on both the sender side and the receiving side. The
-sending side sends cells at regularly spaced intervals (e.g., a connection
-with a bandwidth of 12800B/s would queue a cell every 10ms). The receiving
-side protects against misbehaving servers that send cells more frequently,
-by using a simple token bucket:
+throttling can occur on both the sender side and the receiving side. If
+the LinkPadding option is on, the sending side sends cells at regularly
+spaced intervals (e.g., a connection with a bandwidth of 25600B/s would
+queue a cell every 10ms). The receiving side protects against misbehaving
+servers that send cells more frequently, by using a simple token bucket:
 
 Each connection has a token bucket with a specified capacity. Tokens are
 added to the bucket each second (when the bucket is full, new tokens
@@ -79,22 +85,12 @@
 of the circuit. These bottlenecks can propagate back through the entire
 network, mucking up everything.
 
-To handle this congestion, each circuit starts out with a receive
-window at each node of 100 cells -- it is willing to receive at most 100
-cells on that circuit. (It handles each direction separately; so that's
-really 100 cells forward and 100 cells back.) The edge of the circuit
-is willing to create at most 100 cells from data coming from outside the
-onion routing network. Nodes in the middle of the circuit will tear down
-the circuit if a data cell arrives when the receive window is 0. When
-data has traversed the network, the edge node buffers it on its outbuf,
-and evaluates whether to respond with a 'sendme' acknowledgement: if its
-outbuf is not too full, and its receive window is less than 90, then it
-queues a 'sendme' cell backwards in the circuit. Each node that receives
-the sendme increments its window by 10 and passes the cell onward.
+(See the tor-spec.txt document for details of how congestion control
+works.)
 
 In practice, all the nodes in the circuit maintain a receive window
-close to 100 except the exit node, which stays around 0, periodically
-receiving a sendme and reading 10 more data cells from the webserver.
+close to maximum except the exit node, which stays around 0, periodically
+receiving a sendme and reading more data cells from the webserver.
 In this way we can use pretty much all of the available bandwidth for
 data, but gracefully back off when faced with multiple circuits (a new
 sendme arrives only after some cells have traversed the entire network),
@@ -108,7 +104,7 @@
 
 4.3. Router twins. In many cases when we ask for a router with a given
 address and port, we really mean a router who knows a given key. Router
-twins are two or more routers that all share the same private key. We thus
+twins are two or more routers that share the same private key. We thus
 give routers extra flexibility in choosing the next hop in the circuit: if
 some of the twins are down or slow, it can choose the more available ones.
 

Index: tor-spec.txt
===================================================================
RCS file: /home/or/cvsroot/doc/tor-spec.txt,v
retrieving revision 1.8
retrieving revision 1.9
diff -u -d -r1.8 -r1.9
--- tor-spec.txt	24 Mar 2003 03:31:11 -0000	1.8
+++ tor-spec.txt	5 Apr 2003 19:04:05 -0000	1.9
@@ -163,7 +163,7 @@
 
         First, the OP generates a pair of 8-byte symmetric keys (one
         [K_f] for the 'forward' stream from OP to OR, and one
-        [K_b] for the 'backward' stream from OR to OP.
+        [K_b] for the 'backward' stream from OR to OP).
 
         The OP generates a message [M] in the following format:
            Maximum bandwidth (bytes/s)      [4 bytes]
@@ -223,15 +223,15 @@
 3. Cell Packet format
 
    The basic unit of communication for onion routers and onion
-   proxies is a fixed-width "Cell."  Each Cell contains the following
+   proxies is a fixed-width "cell".  Each cell contains the following
    fields:
 
         ACI (anonymous circuit identifier)    [2 bytes]
         Command                               [1 byte]
         Length                                [1 byte]
         Sequence number (unused, set to 0)    [4 bytes]
-        Payload (padded with 0 bytes)         [120 bytes]
-                                         [Total size: 128 bytes]
+        Payload (padded with 0 bytes)         [248 bytes]
+                                         [Total size: 256 bytes]
 
    The 'Command' field holds one of the following values:
          0 -- PADDING     (Padding)                 (See Sec 6.2)
@@ -242,10 +242,10 @@
 
    The interpretation of 'Length' and 'Payload' depend on the type of
    the cell.
-      PADDING: Length is 0; Payload is 120 bytes of 0's. 
-      CREATE: Length is a value between 1 and 120; the first 'length'
+      PADDING: Length is 0; Payload is 248 bytes of 0's. 
+      CREATE: Length is a value between 1 and 248; the first 'length'
         bytes of payload contain a portion of an onion.
-      DATA: Length is a value between 4 and 120; the first 'length'
+      DATA: Length is a value between 4 and 248; the first 'length'
         bytes of payload contain useful data.
       DESTROY: Neither field is used.
       SENDME: Length encodes a window size, payload is unused.
@@ -335,10 +335,10 @@
           side, then let the high bit of the ACI be 1, else 0.
 
        3. To send M over the wire, prepend a 4-byte integer containing
-          Len(M).  Call the result M'.  Let N=ceil(Len(M')/120).
+          Len(M).  Call the result M'.  Let N=ceil(Len(M')/248).
           Divide M' into N chunks, such that:
-             Chunk_I = M'[(I-1)*120:I*120]  for 1 <= I <= N-1
-             Chunk_N = M'[(N-1)*120:Len(M')]
+             Chunk_I = M'[(I-1)*248:I*248]  for 1 <= I <= N-1
+             Chunk_N = M'[(N-1)*248:Len(M')]
 
        4. Send N CREATE cells along the connection, setting the ACI
           on each to the selected ACI, setting the payload on each to