| Internet-Draft | moq-chat | November 2023 |
| Frindell | Expires 24 May 2024 | [Page] |
MoQ Chat (moq-chat) is a simple text based protocol for exercising MoQ Transport.¶
This note is to be removed before publishing as an RFC.¶
The latest revision of this draft can be found at https://afrind.github.io/draft-frindell-moq-chat/draft-frindell-moq-chat.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-frindell-moq-chat/.¶
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Source for this draft and an issue tracker can be found at https://github.com/afrind/draft-frindell-moq-chat.¶
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MoQ Chat (moq-chat) is a simple text based protocol for exercising MoQ Transport [MOQT]. The protocol allows many participants to join a virtual chat room, publish messages to the room and receive messages published by others.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
Commonly used terms in this document are described below.¶
The moq-chat catalog is used to determine the list of participants in the chat. The format is a text file with text delta encodings.¶
Object 0 in any Group is a complete list of the usernames of the participants in the chat at the time the Object was published, one per-line. The first line of Object 0 is the version of the catalog format specificaiton. The format described here is moq-chat catalog format version 1.¶
Object 0 Example:¶
version=1 alice bob charlie¶
Any Object in a Group with sequence number higher than 0 is a delta encoding, with new participants prefaced with a '+' character and participants that have left the chat prefaced with a '-' character. Every delta encoding object MUST be applied for an endpoint to have a current list of participants.¶
Delta Encoding Exmaple:¶
+daphne -bob¶
Every username in the catalog MUST be unique. If an endpoint receives a catalog or delta encoding that would result in the same username more than once, it MUST close the session with an error.¶
Every object in a catalog group MUST be on a single stream, so that updates are delivered in order.¶
The protocol requires that one entity operate as a chat server. The function of the server is to maintain the list of participants in the chat and publish catalog updates.¶
Every chat has a unique ID. The ID is a string of arbitrary length and uniquely identifies the chat. The creation of chat IDs and discovery of the server endpoint is out of the scope of this document.¶
The catalog for a given chat is available by subscribing to moq-chat/id.¶
To join the chat a participant sends a SUBSCRIBE message to moq-chat/id in order to get the participant list and subsequent participant updates. This SUBSCRIBE requires the AUTHORIZATION_INFO to contain the participant's ASCII string username. It is RECOMMENDED the participant request the catalog starting from the beginning of the current Group. The moq-chat server will reply with an SUBSCRIBE_OK if joining was successful or SUBSCRIBE_ERROR if the join failed.¶
The participant also sends an ANNOUNCE message to the server with a track namespace of moq-chat/id/participant/username, and an empty Track Name.¶
When a moq-chat server receives a SUBSCRIBE and sends an SUBSCRIBE OK, it MUST update the catalog. It can either publish a new Group with the updated particiant list, a delta encoding against the current Group, or both.¶
After receiving the most recent catalog information, a client SHOULD subscribe to the track for each active participant.¶
Upon receiving a delta update removing a participant, a client SHOULD unsubscribe from that track if it had previously subscribed.¶
Upone receiving a delta update adding a participant, a client should subscribe to the new track.¶
Each chat message is sent in a new Group and new Object. The format of a chat chat message for version 1 catalogs is UTF-8 Encoded text. There is no limit to the length of a chat message beyond those imposed on QUIC streams.¶
When a user leaves the chat, it would be nice if they could send a message indicating that their track is complete or no longer available, but the protocol has no such message (yet).¶
When a server or relay detects a MOQT session has terminated, it MUST update the catalog and remove any participants that had sent ANNOUNCE messages on that session.¶
There is no prescription for how to map catalog or chat messages onto QUIC streams. Endpoints can choose to use one stream per track, one stream per group or one stream per object.¶
If a client detects a MOQT session has been closed by the server, it assumes the server has exited or crashed, and does not attempt to reconnect.¶
TODO Security¶
This document has no IANA actions.¶
TODO acknowledge.¶