Use abbrevs to compress relay command table a bit more

1 files changed, 42 insertions, 40 deletions

diff --git a/spec/tor-spec/relay-cells.md b/spec/tor-spec/relay-cells.md
index 3fabbcc..a665c4f 100644
--- a/spec/tor-spec/relay-cells.md
+++ b/spec/tor-spec/relay-cells.md
@@ -32,41 +32,41 @@ enveloped relay message, encoded as follows:
 
 The relay commands are:
 
-| Command | Identifier      | Direction           | Control?
-| ------- | ----------      | ---------           | --------
-|  1      | BEGIN     | forward             |
-|  2      | DATA      | forward or backward |
-|  3      | END       | forward or backward |
-|  4      | CONNECTED | backward            |
-|  5      | SENDME    | forward or backward | sometimes control
-|  6      | EXTEND    | forward             | control
-|  7      | EXTENDED  | backward            | control
-|  8      | TRUNCATE  | forward             | control
-|  9      | TRUNCATED | backward            | control
-| 10      | DROP      | forward or backward | control
-| 11      | RESOLVE   | forward             |
-| 12      | RESOLVED  | backward            |
-| 13      | BEGIN_DIR | forward             |
-| 14      | EXTEND2   | forward             | control
-| 15      | EXTENDED2 | backward            | control
-| 16..18  | Reserved for UDP; Not yet in use, see [prop339].
-| 19      | CONFLUX_LINK        | forward   | control
-| 20      | CONFLUX_LINKED      | backward  | control
-| 21      | CONFLUX_LINKED_ACK  | forward   | control
-| 22      | CONFLUX_SWITCH      | forward or backward | control
-| 32      | ESTABLISH_INTRO     | forward   | control
-| 33      | ESTABLISH_RENDEZVOUS | forward   | control
-| 34      | INTRODUCE1          | forward   | control
-| 35      | INTRODUCE2          | backward  | control
-| 36      | RENDEZVOUS1         | forward   | control
-| 37      | RENDEZVOUS2         | backward  | control
-| 38      | INTRO_ESTABLISHED   | backward  | control
-| 39      | RENDEZVOUS_ESTABLISHED | backward | control
-| 40      | INTORDUCE_ACK       | backward  | control
-| 41      | PADDING_NEGOTIATE   | forward   | control
-| 42      | PADDING_NEGOTIATED  | backward  | control
-| 43      | XON  (See Sec 4 of [prop324])  | forward or backward |
-| 44      | XOFF (See Sec 4 of [prop324])  | forward or backward |
+| Command | Identifier  | Type
+| ------- | ----------  | ----
+|  1      | BEGIN     | **F**
+|  2      | DATA      | **F**/**B**
+|  3      | END       | **F**/**B**
+|  4      | CONNECTED | **B**
+|  5      | SENDME    | **F**/**B**, **C?**
+|  6      | EXTEND    | **F**, **C**
+|  7      | EXTENDED  | **B**, **C**
+|  8      | TRUNCATE  | **F**, **C**
+|  9      | TRUNCATED | **B**, **C**
+| 10      | DROP      | **F**/**B**, **C**
+| 11      | RESOLVE   | **F**
+| 12      | RESOLVED  | **B**
+| 13      | BEGIN_DIR | **F**
+| 14      | EXTEND2   | **F**, **C**
+| 15      | EXTENDED2 | **B**, **C**
+| 16..18  | Reserved; see [prop339].
+| 19      | CONFLUX_LINK        | **F**, **C**
+| 20      | CONFLUX_LINKED      | **B**, **C**
+| 21      | CONFLUX_LINKED_ACK  | **F**, **C**
+| 22      | CONFLUX_SWITCH      | **F**/**B**, **C**
+| 32      | ESTABLISH_INTRO     | **F**, **C**
+| 33      | ESTABLISH_RENDEZVOUS | **F**, **C**
+| 34      | INTRODUCE1          | **F**, **C**
+| 35      | INTRODUCE2          | **B**, **C**
+| 36      | RENDEZVOUS1         | **F**, **C**
+| 37      | RENDEZVOUS2         | **B**, **C**
+| 38      | INTRO_ESTABLISHED   | **B**, **C**
+| 39      | RENDEZVOUS_ESTABLISHED | **B**, **C**
+| 40      | INTRODUCE_ACK       | **B**, **C**
+| 41      | PADDING_NEGOTIATE   | **F**, **C**
+| 42      | PADDING_NEGOTIATED  | **B**, **C**
+| 43      | XON  (See Sec 4 of [prop324])  | **F**/**B**
+| 44      | XOFF (See Sec 4 of [prop324])  | **F**/**B**
 
 [prop324]: ../proposals/324-rtt-congestion-control.txt
 [prop329]: ../proposals/329-traffic-splitting.md
@@ -74,10 +74,12 @@ The relay commands are:
 [rendezvous spec]: ../rend-spec/index.md
 ["Circuit-level padding"]: ../padding-spec/circuit-level-padding.md#circuit-level-padding
 
-Commands labelled as "forward" must only be sent by the originator
-of the circuit. Commands labelled as "backward" must only be sent by
-other nodes in the circuit back to the originator. Commands marked
-as either can be sent either by the originator or other nodes.
+- **F** (Forward): Must only be sent by the originator of the circuit.
+- **B** (Backward): Must only be sent by other nodes in the circuit
+  back towards the originator.
+- **F**/**B** (Forward or backward): May be sent in either direction.
+- **C**: (Control) must have a zero-valued stream ID.
+  (Other commands must have a nonzero stream ID.)
 
 The 'recognized' field is used as a simple indication that the cell
 is still encrypted. It is an optimization to avoid calculating
@@ -112,7 +114,7 @@ All relay messages pertaining to the same tunneled stream have the same
 stream ID.  StreamIDs are chosen arbitrarily by the OP.  No stream
 may have a StreamID of zero. Rather, relay messages that affect the
 entire circuit rather than a particular stream use a StreamID of zero
--- they are marked in the table above as "\[control\]" style
+-- they are marked in the table above as "**C**" ([control") style
 cells. (Sendme cells are marked as "sometimes control" because they
 can include a StreamID or not depending on their purpose -- see
 [Flow control](./flow-control.md#flow-control).)