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Land Datagram Preferred (PR #342) (#344)
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Update main to reflect the tx-mode branch after #342 was merged.
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@ianswett
ianswett authored Jan 22, 2024
2 parents 124aec9 + be469ed commit d97485d
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112 changes: 75 additions & 37 deletions draft-ietf-moq-transport.md
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Expand Up @@ -685,41 +685,43 @@ MOQT Message {
~~~
{: #moq-transport-message-format title="MOQT Message"}

|-------|----------------------------------------------------|
| ID | Messages |
|------:|:---------------------------------------------------|
| 0x0 | OBJECT_STREAM ({{object-message-formats}}) |
|-------|----------------------------------------------------|
| 0x3 | SUBSCRIBE ({{message-subscribe-req}}) |
|-------|----------------------------------------------------|
| 0x4 | SUBSCRIBE_OK ({{message-subscribe-ok}}) |
|-------|----------------------------------------------------|
| 0x5 | SUBSCRIBE_ERROR ({{message-subscribe-error}}) |
|-------|----------------------------------------------------|
| 0x6 | ANNOUNCE ({{message-announce}}) |
|-------|----------------------------------------------------|
| 0x7 | ANNOUNCE_OK ({{message-announce-ok}}) |
|-------|----------------------------------------------------|
| 0x8 | ANNOUNCE_ERROR ({{message-announce-error}}) |
|-------|----------------------------------------------------|
| 0x9 | UNANNOUNCE ({{message-unannounce}}) |
|-------|----------------------------------------------------|
| 0xA | UNSUBSCRIBE ({{message-unsubscribe}}) |
|-------|----------------------------------------------------|
| 0xB | SUBSCRIBE_FIN ({{message-subscribe-fin}}) |
|-------|----------------------------------------------------|
| 0xC | SUBSCRIBE_RST ({{message-subscribe-rst}}) |
|-------|----------------------------------------------------|
| 0x10 | GOAWAY ({{message-goaway}}) |
|-------|----------------------------------------------------|
| 0x40 | CLIENT_SETUP ({{message-setup}}) |
|-------|----------------------------------------------------|
| 0x41 | SERVER_SETUP ({{message-setup}}) |
|-------|----------------------------------------------------|
| 0x50 | STREAM_HEADER_TRACK ({{multi-object-streams}}) |
|-------|----------------------------------------------------|
| 0x51 | STREAM_HEADER_GROUP ({{multi-object-streams}}) |
|-------|----------------------------------------------------|
|-------|-----------------------------------------------------|
| ID | Messages |
|------:|:----------------------------------------------------|
| 0x0 | OBJECT_STREAM ({{object-message-formats}}) |
|-------|-----------------------------------------------------|
| 0x1 | OBJECT_PREFER_DATAGRAM ({{object-message-formats}}) |
|-------|-----------------------------------------------------|
| 0x3 | SUBSCRIBE ({{message-subscribe-req}}) |
|-------|-----------------------------------------------------|
| 0x4 | SUBSCRIBE_OK ({{message-subscribe-ok}}) |
|-------|-----------------------------------------------------|
| 0x5 | SUBSCRIBE_ERROR ({{message-subscribe-error}}) |
|-------|-----------------------------------------------------|
| 0x6 | ANNOUNCE ({{message-announce}}) |
|-------|-----------------------------------------------------|
| 0x7 | ANNOUNCE_OK ({{message-announce-ok}}) |
|-------|-----------------------------------------------------|
| 0x8 | ANNOUNCE_ERROR ({{message-announce-error}}) |
|-------|-----------------------------------------------------|
| 0x9 | UNANNOUNCE ({{message-unannounce}}) |
|-------|-----------------------------------------------------|
| 0xA | UNSUBSCRIBE ({{message-unsubscribe}}) |
|-------|-----------------------------------------------------|
| 0xB | SUBSCRIBE_FIN ({{message-subscribe-fin}}) |
|-------|-----------------------------------------------------|
| 0xC | SUBSCRIBE_RST ({{message-subscribe-rst}}) |
|-------|-----------------------------------------------------|
| 0x10 | GOAWAY ({{message-goaway}}) |
|-------|-----------------------------------------------------|
| 0x40 | CLIENT_SETUP ({{message-setup}}) |
|-------|-----------------------------------------------------|
| 0x41 | SERVER_SETUP ({{message-setup}}) |
|-------|-----------------------------------------------------|
| 0x50 | STREAM_HEADER_TRACK ({{multi-object-streams}}) |
|-------|-----------------------------------------------------|
| 0x51 | STREAM_HEADER_GROUP ({{multi-object-streams}}) |
|-------|-----------------------------------------------------|

## Parameters {#params}

Expand Down Expand Up @@ -889,14 +891,16 @@ group.
{{send-order}} or priority {{ordering-by-priorities}} value.

* Object Forwarding Preference: An enumeration indicating how a sender sends an
object. The preferences are Track, Group, and Object. An Object MUST be sent
according to its `Object Forwarding Preference`, described below.
object. The preferences are Track, Group, Object and Datagram. An Object MUST
be sent according to its `Object Forwarding Preference`, described below.

* Object Payload: An opaque payload intended for the consumer and SHOULD
NOT be processed by a relay.

### Object Message Formats

**Object Stream Message**

An `OBJECT_STREAM` message carries a single object on a stream. There is no
explicit length of the payload; it is determined by the end of the stream. An
`OBJECT_STREAM` message MUST be the first and only message on a unidirectional
Expand Down Expand Up @@ -931,6 +935,36 @@ the receiver MUST close the session with a Protocol Violation.

* Other fields: As described in {{canonical-object-fields}}.

**Object Prefer Datagram Message**

An `OBJECT_PREFER_DATAGRAM` message carries a single object in a datagram or
a stream. There is no explicit length of the payload; it is determined by the
length of the datagram or stream. If this message appears on a stream, it MUST
be the only message on a unidirectional stream.

An Object received in an `OBJECT_PREFER_DATAGRAM` message has an `Object
Forwarding Preference` = `Datagram`.

To send an Object with `Object Forwarding Preference` = `Datagram`, determine
the length of the fields and payload, and compare the length with the maximum
datagram size of the session. If the object size is less than or equal maximum
datagram size, send the serialized data as a datagram. Otherwise, open a
stream, send the serialized data and terminate the stream. An implementation
SHOULD NOT send an Object with `Object Forwarding Preference` = `Datagram` on a
stream if it is possible to send it as a datagram.

~~~
OBJECT_PREFER_DATAGRAM Message {
Subscription ID (i),
Track Alias (i),
Group ID (i),
Object ID (i),
Object Send Order (i),
Object Payload (...),
}
~~~
{: #object-datagram-format title="MOQT OBJECT_PREFER_DATAGRAM Message"}

### Multi-Object Streams

When multiple objects are sent on a stream, the stream begins with a stream
Expand All @@ -944,6 +978,8 @@ same stream header message type and fields.

TODO: figure out how a relay closes these streams

**Stream Header Track**

When a stream begins with `STREAM_HEADER_TRACK`, all objects on the stream
belong to the track requested in the Subscribe message identified by `Subscribe
ID`. All objects on the stream have the `Object Send Order` specified in the
Expand Down Expand Up @@ -976,6 +1012,8 @@ stream that is associated with the subscription, or open a new one and send the
~~~
{: #object-track-format title="MOQT Track Stream Object Fields"}

**Stream Header Group**

A sender MUST NOT send an Object on a stream if its Group ID is less than a
previously sent Group ID on that stream, or if its Object ID is less than or
equal to a previously sent Object ID within a given group on that stream.
Expand Down

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