Reliable QUIC Stream Resets

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Table of Contents

1. Introduction

QUIC version 1 ([RFC9000]) allows streams to be reset. When a stream is reset, the sender doesn't retransmit stream data for the respective stream. On the receiver side, the QUIC stack is free to surface the stream reset to the application immediately, even if it has already received stream data for that stream.¶

Applications running on top of QUIC might need to send an identifier at the beginning of the stream in order to associate that stream with a specific subpart of the application. For example, WebTransport ([WEBTRANSPORT]) uses a variable-length-encoded integer (as defined in QUIC version 1) to transmit the ID of the WebTransport session to the receiver. It is desirable that the receiver is able to associate incoming streams with their respective subpart of the application, even if the QUIC stream is reset before the identifier at the beginning of the stream was read.¶

Another use-case is relaying data from an external data source. When a relay is sending data being read from an external source and encounters an error, it might want to use a stream reset to signal that error, at the same time making sure that all data being read previously is delivered to the peer.¶

This document describes a QUIC extension defining a new frame type, the CLOSE_STREAM frame. This frame allows an endpoint to mark a portion at the beginning of the stream which will then be guaranteed to be delivered to receiver's application, even if the stream was reset.¶

2. Conventions and Definitions

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.¶

3. Negotiating Extension Use

Endpoints advertise their support of the extension described in this document by sending the close_stream (0x17f7586d2cb570) transport parameter (Section 7.4 of [RFC9000]) with an empty value. An implementation that understands this transport parameter MUST treat the receipt of a non-empty value as a connection error of type TRANSPORT_PARAMETER_ERROR.¶

In order to allow reliable stream resets in 0-RTT packets, both endpoints MUST remember the value of this transport parameter. If 0-RTT data is accepted by the server, the server MUST NOT disable this extension on the resumed connection.¶

4. CLOSE_STREAM Frame

Conceptually, the CLOSE_STREAM frame is a RESET_STREAM frame with an added Reliable Size field.¶

CLOSE_STREAM Frame {
  Type (i) = 0x20,
  Stream ID (i),
  Application Protocol Error Code (i),
  Final Size (i),
  Reliable Size (i),
}

The CLOSE_STREAM frames contain the following fields:¶

Stream ID: A variable-length integer encoding of the stream ID of the stream being terminated.¶

Application Protocol Error Code: A variable-length integer containing the application protocol error code (see Section 20.2) that indicates why the stream is being closed.¶

Final Size: A variable-length integer indicating the final size of the stream by the RESET_STREAM sender, in units of bytes; see (Section 4.5 of [RFC9000]).¶

Reliable Size: A variable-length integer indicating the amount of data that needs to be delivered to the application even though the stream is reset.¶

If the Reliable Size is larger than the Final Size, the receiver MUST close the connection with a connection error of type FRAME_ENCODING_ERROR.¶

CLOSE_STREAM frames are ack-eliciting. When lost, they MUST be retransmitted, unless the stream state has transitioned to "Data Recvd" or "Reset Recvd" due to transmission and acknowledgement of other frames (see Section 5.1).¶

5. Resetting Streams

When resetting a stream, the node has the choice between using a RESET_STREAM frame and a CLOSE_STREAM frame. When using a RESET_STREAM frame, the behavior is unchanged from the behavior described in ([RFC9000]).¶

When using a CLOSE_STREAM frame, the initiator MUST guarantee reliable delivery of stream data of at least Reliable Size bytes. If STREAM frames containing data up to that byte offset are lost, the initiator MUST retransmit this data, as described in (Section 13.3 of [RFC9000]). Data sent beyond that byte offset SHOULD NOT be retransmitted.¶

As described in (Section 3.2 of [RFC9000]), it MAY deliver data beyond that offset to the application.¶

6. Security Considerations

TODO Security¶

7. IANA Considerations

Acknowledgments

TODO acknowledge.¶

Authors' Addresses