Merge branch 'main' into fail-length

Author: ianswett

draft-ietf-moq-transport.md

@@ -19,7 +19,7 @@ author:
   -
     ins: L. Curley
     name: Luke Curley
-    organization: Twitch
+    organization: Discord
     email: [email protected]
 
   -
@@ -40,6 +40,12 @@ author:
     organization: Google
     email: [email protected]
 
+  -
+    ins: I. Swett
+    name: Ian Swett
+    organization: Google
+    email: [email protected]
+    role: editor
 
 normative:
   QUIC: RFC9000
@@ -405,7 +411,9 @@ code, as defined below:
 |------|---------------------------|
 | 0x3  | Protocol Violation        |
 |------|---------------------------|
-| 0x4  | Parameter Length Mismatch |
+| 0x4  | Duplicate Track Alias     |
+|------|---------------------------|
+| 0x5  | Parameter Length Mismatch |
 |------|---------------------------|
 | 0x10 | GOAWAY Timeout            |
 |------|---------------------------|
@@ -420,6 +428,9 @@ code, as defined below:
 * Protocol Violation: The remote endpoint performed an action that was
   disallowed by the specification.
 
+* Duplicate Track Alias: The endpoint attempted to use a Track Alias
+  that was already in use.
+
 * GOAWAY Timeout: The session was closed because the client took too long to
   close the session in response to a GOAWAY ({{message-goaway}}) message.
   See session migration ({{session-migration}}).
@@ -858,8 +869,8 @@ OBJECT Message {
 ~~~
 {: #moq-transport-object-format title="MOQT OBJECT Message"}
 
-* Track Alias : The compressed full track name obtained as part of
-subscription and/or publish control message exchanges.
+* Track Alias :The track identifier as specified in the
+  SUBSCRIBE message {{message-subscribe-req}}.
 
 * Group ID : The object is a member of the indicated group ID
 {{model-group}} within the track.
@@ -927,6 +938,7 @@ The format of SUBSCRIBE is as follows:
 ~~~
 SUBSCRIBE Message {
   Subscribe ID (i),
+  Track Alias (i),
   Track Namespace (b),
   Track Name (b),
   StartGroup (Location),
@@ -938,18 +950,24 @@ SUBSCRIBE Message {
 ~~~
 {: #moq-transport-subscribe-format title="MOQT SUBSCRIBE Message"}
 
-* Track Namespace: Identifies the namespace of the track as defined in
-({{track-name}}).
-
-* Track Name: Identifies the track name as defined in ({{track-name}}).
-
 * Subscribe ID: The subscription identifier that is unique within the session.
 `Subscribe ID` is a monotonically increasing variable length integer which
 MUST not be reused within a session. `Subscribe ID` is used by subscribers and
 the publishers to identify a given subscription. Subscribers specify the
 `Subscribe ID` and it is included in the corresponding SUBSCRIBE_OK or
 SUBSCRIBE_ERROR messages.
 
+* Track Alias: A session specific identifier for the track.
+Messages that reference a track, such as OBJECT ({{message-object}}),
+reference this Track Alias instead of the Track Name and Track Namespace to
+reduce overhead. If the Track Alias is already in use, the publisher MUST
+close the session with a Duplicate Track Alias error ({{session-termination}}).
+
+* Track Namespace: Identifies the namespace of the track as defined in
+({{track-name}}).
+
+* Track Name: Identifies the track name as defined in ({{track-name}}).
+
 * StartGroup: The Location of the requested group.  StartGroup's Mode MUST NOT be
 None.
 
@@ -1038,9 +1056,6 @@ A SUBSCRIBE_OK control message is sent for successful subscriptions.
 SUBSCRIBE_OK
 {
   Subscribe ID (i),
-  Track Namespace (b),
-  Track Name (b),
-  Track Alias (i),
   Expires (i)
 }
 ~~~
@@ -1053,11 +1068,6 @@ SUBSCRIBE_OK
 
 * Track Name: Identifies the track name as defined in ({{track-name}}).
 
-* Track Alias: Session specific identifier that is used as an alias for the
-Full Track Name in the Track Alias field of the OBJECT ({{message-object}})
-message headers of the requested track. Track Aliases are shorter
-than Full Track Names and thus reduce the overhead in OBJECT messages.
-
 * Expires: Time in milliseconds after which the subscription is no
 longer valid. A value of 0 indicates that the subscription stays active
 until it is explicitly unsubscribed.
@@ -1074,6 +1084,7 @@ SUBSCRIBE_ERROR
   Subscribe ID (i),
   Error Code (i),
   Reason Phrase (b),
+  Track Alias (i),
 }
 ~~~
 {: #moq-transport-subscribe-error format title="MOQT SUBSCRIBE_ERROR Message"}
@@ -1082,10 +1093,14 @@ SUBSCRIBE_ERROR
 
 * Error Code: Identifies an integer error code for subscription failure.
 
-* Reason Phrase Length: The length in bytes of the reason phrase.
-
 * Reason Phrase: Provides the reason for subscription error.
 
+* Track Alias: When Error Code is TBD, the subscriber SHOULD re-issue the
+  SUBSCRIBE with this Track Alias instead. If this Track Alias is already in use,
+  the receiver MUST close the connection with a Duplicate Track Alias error
+  ({{session-termination}}).
+  TODO: Add a registry for subscribe error codes and make this field conditional.
+
 
 ## UNSUBSCRIBE {#message-unsubscribe}