| Internet-Draft | QUIC Reliable Messages | March 2025 |
| Seemann | Expires 24 September 2025 | [Page] |
This document introduces a new way to transmit reliable messages on top of QUIC.¶
This note is to be removed before publishing as an RFC.¶
The latest revision of this draft can be found at https://marten-seemann.github.io/draft-seemann-quic-reliable-message/draft-seemann-quic-reliable-message.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-seemann-quic-reliable-message/.¶
Discussion of this document takes place on the QUIC Working Group mailing list (mailto:quic@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/quic/. Subscribe at https://www.ietf.org/mailman/listinfo/quic/.¶
Source for this draft and an issue tracker can be found at https://github.com/marten-seemann/draft-seemann-quic-reliable-message.¶
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Applications running on top of QUIC ([RFC9000]) have two options to transmit data. First, they can send data on top of (unidirectional or bidirectional) QUIC streams. Second, [RFC9221] defines an unreliable datagram extension to QUIC. In the case of packet loss, data sent on QUIC streams is retransmitted, unless the stream was reset. DATAGRAM frames are not retransmitted.¶
This document defines an extension to QUIC that introduces a new frame, the MESSAGE frame. This frame is intended for short (sub-MTU) messages that need to be delivered reliably. However, implementations may allow the application to update the message before sending a retransmission.¶
If the extension is negotiated, an endpoint is allowed to send MESSAGE frames up to the maximum sequence number the peer advertised in the max_message_id transport parameter. Endpoints SHOULD regularly increase the maximum sequence number by sending MAX_MESSAGE frames as MESSAGE frames are consumed.¶
When a MESSAGE frame is declared lost, implementations MUST do one of two things: They either MUST retransmit the frame, or they MUST inform the application. The application MAY decide that the frame does not need to be retransmitted, or it MAY update the contents of the message. If the contents of the message are updated, it MUST be transmitted using a new sequence number.¶
The receiver of a MESSAGE frame MUST deliver the frame to the application. It MUST NOT drop the frame, unless the connection is closed.¶
There are two frames, the MESSAGE frame, and the MAX_MESSAGE frame.¶
MESSAGE Frame {
Type (i) = TBD,
Sequence Number (i),
Message Data (...),
}
¶
The MESSAGE frame contains the following fields:¶
A variable-length integer encoding of the sequence number of the message. Sequence numbers start at 0 and SHOULD be used sequentially.¶
The message data to be delivered.¶
An endpoint that receives a MESSAGE frame with a Sequence Number larger than the maximum sequence number it has previously advertised to the peer MUST close the connection with a connection error of type PROTOCOL_VIOLATION.¶
MAX_MESSAGE Frame {
Type (i) = TBD+1,
Maximum Sequence Number (i),
}
¶
The MAX_MESSAGE frame contains the following fields:¶
The maximum sequence number that the peer is willing to receive.¶
The Maximum Sequence Number MUST NOT be decreased. However, due to reordering on the wire, MAX_MESSAGE frames might be received out of order. The receiver MUST ignore MAX_MESSAGE frames that do not increase the Maximum Sequence Number.¶
Endpoints advertise their support of the extension described in this document by sending the max_message_id (TBD) transport parameter (Section 7.4 of [RFC9000]) with variable-length integer value specifying the maximum sequence number of MESSAGE frames it is willing to receive. An implementation that understands this transport parameter MUST treat the receipt of an invalid value as a connection error of type TRANSPORT_PARAMETER_ERROR.¶
When using 0-RTT, both endpoints MUST remember the value of this transport parameter. This allows use of this extension in 0-RTT packets. When the server accepts 0-RTT data, the server MUST NOT disable this extension or reduce the value on the resumed connection.¶
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.¶
A malicious node could attempt to overwhelm an endpoint by sending a large number of MESSAGE frames. Endpoints SHOULD make sure to define reasonable limits using the transport parameter and the MAX_MESSAGE frame.¶
TODO: consider transport parameter and frame types¶
TODO acknowledge.¶