Network Working Group T. Pauly
Internet-Draft E. Kinnear
Intended status: Standards Track Apple Inc.
Expires: April 24, 2020 D. Schinazi
Google LLC
October 22, 2019
An Unreliable Datagram Extension to QUIC
draft-pauly-quic-datagram-04
Abstract
This document defines an extension to the QUIC transport protocol to
add support for sending and receiving unreliable datagrams over a
QUIC connection.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 24, 2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Pauly, et al. Expires April 24, 2020 [Page 1]
Internet-Draft QUIC Datagrams October 2019
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Specification of Requirements . . . . . . . . . . . . . . 2
2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Transport Parameter . . . . . . . . . . . . . . . . . . . . . 3
4. Datagram Frame Type . . . . . . . . . . . . . . . . . . . . . 4
5. Behavior and Usage . . . . . . . . . . . . . . . . . . . . . 4
5.1. Acknowledgement Handling . . . . . . . . . . . . . . . . 5
5.2. Flow Control . . . . . . . . . . . . . . . . . . . . . . 5
5.3. Congestion Control . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
The QUIC Transport Protocol [I-D.ietf-quic-transport] provides a
secure, multiplexed connection for transmitting reliable streams of
application data. Reliability within QUIC is performed on a per-
stream basis, so some frame types are not eligible for
retransmission.
Some applications, particularly those that need to transmit real-time
data, prefer to transmit data unreliably. These applications can
build directly upon UDP [RFC0768] as a transport, and can add
security with DTLS [RFC6347]. Extending QUIC to support transmitting
unreliable application data would provide another option for secure
datagrams, with the added benefit of sharing a cryptographic and
authentication context used for reliable streams.
This document defines four new DATAGRAM QUIC frame types, which carry
application data without requiring retransmissions.
1.1. Specification of Requirements
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.
Pauly, et al. Expires April 24, 2020 [Page 2]
Internet-Draft QUIC Datagrams October 2019
2. Motivation
Transmitting unreliable data over QUIC provides benefits over
existing solutions:
o Applications that open both a reliable TLS stream and an
unreliable DTLS flow to the same peer can benefit by sharing a
single handshake and authentication context between a reliable
QUIC stream and flow of unreliable QUIC datagrams. This can
reduce the latency required for handshakes.
o QUIC uses a more nuanced loss recovery mechanism than the DTLS
handshake, which has a basic packet loss retransmission timer.
This may allow loss recovery to occur more quickly for QUIC data.
o QUIC datagrams, while unreliable, can support acknowledgements,
allowing applications to be aware of whether a datagram was
successfully received.
These reductions in connection latency, and application insight into
the delivery of datagrams, can be useful for optimizing audio/video
streaming applications, gaming applications, and other real-time
network applications.
Unreliable QUIC datagrams can also be used to implement an IP packet
tunnel over QUIC, such as for a Virtual Private Network (VPN).
Internet-layer tunneling protocols generally require a reliable and
authenticated handshake, followed by unreliable secure transmission
of IP packets. This can, for example, require a TLS connection for
the control data, and DTLS for tunneling IP packets. A single QUIC
connection could support both parts with the use of unreliable
datagrams.
3. Transport Parameter
Support for receiving the DATAGRAM frame types is advertised by means
of a QUIC Transport Parameter (name=max_datagram_frame_size,
value=0x0020). The max_datagram_frame_size transport parameter is an
integer value (represented as a variable-length integer) that
represents the maximum size of a DATAGRAM frame (including the frame
type, length, and payload) the endpoint is willing to receive, in
bytes. An endpoint that includes this parameter supports the
DATAGRAM frame types and is willing to receive such frames on this
connection. Endpoints MUST NOT send DATAGRAM frames until they have
sent and received the max_datagram_frame_size transport parameter.
Endpoints MUST NOT send DATAGRAM frames of size strictly larger than
the value of max_datagram_frame_size the endpoint has received from
its peer. An endpoint that receives a DATAGRAM frame when it has not
Pauly, et al. Expires April 24, 2020 [Page 3]
Internet-Draft QUIC Datagrams October 2019
sent the max_datagram_frame_size transport parameter MUST terminate
the connection with error PROTOCOL_VIOLATION. An endpoint that
receives a DATAGRAM frame that is strictly larger than the value it
sent in its max_datagram_frame_size transport parameter MUST
terminate the connection with error PROTOCOL_VIOLATION.
4. Datagram Frame Type
DATAGRAM frames are used to transmit application data in an
unreliable manner. The DATAGRAM frame type takes the form 0b0011000X
(or the values 0x30 and 0x31). The least significant bit of the
DATAGRAM frame type is the LEN bit (0x01). It indicates that there
is a Length field present. If this bit is set to 0, the Length field
is absent and the Datagram Data field extends to the end of the
packet. If this bit is set to 1, the Length field is present.
The DATAGRAM frame is structured as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| [Length (i)] ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Datagram Data (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: DATAGRAM Frame Format
DATAGRAM frames contain the following fields:
Length: A variable-length integer specifying the length of the
datagram in bytes. This field is present only when the LEN bit is
set. If the LEN bit is not set, the datagram data extends to the
end of the QUIC packet.
Datagram Data: The bytes of the datagram to be delivered.
5. Behavior and Usage
When an application sends an unreliable datagram over a QUIC
connection, QUIC will generate a new DATAGRAM frame and send it in
the first available packet. This frame SHOULD be sent as soon as
possible, and MAY be coalesced with other frames.
When a QUIC endpoint receives a valid DATAGRAM frame, it SHOULD
deliver the data to the application immediately, as long as it is
able to process the frame and can store the contents in memory.
Pauly, et al. Expires April 24, 2020 [Page 4]
Internet-Draft QUIC Datagrams October 2019
DATAGRAM frames MUST be protected with either 0-RTT or 1-RTT keys.
Application protocols using datagrams might need to differentiate
categories or flows of datagrams being transmitted over a single QUIC
connection. Each application protocol is expected to define its own
mechanism for adding flow identifiers or similar mechanisms to the
datagram payloads being sent over the QUIC connection. For example,
the use of datagrams with HTTP/3 is defined in
[I-D.schinazi-quic-h3-datagram].
5.1. Acknowledgement Handling
Although DATAGRAM frames are not retransmitted upon loss detection,
they are ack-eliciting ([I-D.ietf-quic-recovery]). Receivers SHOULD
support delaying ACK frames (within the limits specified by
max_ack_delay) in reponse to receiving packets that only contain
DATAGRAM frames, since the timing of these acknowledgements is not
used for loss recovery.
If a sender detects that a packet containing a specific DATAGRAM
frame has been lost, the implementation MAY notify the application
that the datagram was lost. Similarly, if a packet containing a
DATAGRAM frame is acknowledged, the implementation MAY notify the
application that the datagram was successfully transmitted and
received.
5.2. Flow Control
DATAGRAM frames do not provide any explicit flow control signaling,
and do not contribute to any per-flow or connection-wide data limit.
The risk associated with not providing flow control for DATAGRAM
frames is that a receiver may not be able to commit the necessary
resources to process the frames. For example, it may not be able to
store the frame contents in memory. However, since DATAGRAM frames
are inherently unreliable, they MAY be dropped by the receiver if the
receiver cannot process them.
5.3. Congestion Control
DATAGRAM frames are subject to a QUIC connection's congestion
control. Specifically, if a DATAGRAM frame is enqueued to be sent by
the application, but sending a packet with this frame is not allowed
by the congestion control window as specified in
[I-D.ietf-quic-recovery], the packet cannot be sent. The sender
implementation MUST either drop the frame without sending it (at
which point it MAY notify the application) or else delay sending the
frame until the window opens.
Pauly, et al. Expires April 24, 2020 [Page 5]
Internet-Draft QUIC Datagrams October 2019
Implementations can optionally support allowing the application to
specify a sending expiration time, beyond which a congestion-
controlled DATAGRAM frame ought to be dropped without transmission.
6. Security Considerations
The DATAGRAM frame shares the same security properties as the rest of
the data transmitted within a QUIC connection. All application data
transmitted with the DATAGRAM frame, like the STREAM frame, MUST be
protected either by 0-RTT or 1-RTT keys.
7. IANA Considerations
This document registers a new value in the QUIC Transport Parameter
Registry:
Value: 0x0020 (if this document is approved)
Parameter Name: max_datagram_frame_size
Specification: Indicates that the connection should enable support
for unreliable DATAGRAM frames. An endpoint that advertises this
transport parameter can receive datagrams frames from the other
endpoint, up to and including the length in bytes provided in the
transport parameter.
This document also registers a new value in the QUIC Frame Type
registry:
Value: 0x30 and 0x31 (if this document is approved)
Frame Name: DATAGRAM
Specification: Unreliable application data
8. Acknowledgments
Thanks to Ian Swett, who inspired this proposal.
9. References
9.1. Normative References
[I-D.ietf-quic-recovery]
Iyengar, J. and I. Swett, "QUIC Loss Detection and
Congestion Control", draft-ietf-quic-recovery-23 (work in
progress), September 2019.
Pauly, et al. Expires April 24, 2020 [Page 6]
Internet-Draft QUIC Datagrams October 2019
[I-D.ietf-quic-transport]
Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed
and Secure Transport", draft-ietf-quic-transport-23 (work
in progress), September 2019.
9.2. Informative References
[I-D.schinazi-quic-h3-datagram]
Schinazi, D., "Using QUIC Datagrams with HTTP/3", draft-
schinazi-quic-h3-datagram-01 (work in progress), October
2019.
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
DOI 10.17487/RFC0768, August 1980,
<https://www.rfc-editor.org/info/rfc768>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
Authors' Addresses
Tommy Pauly
Apple Inc.
One Apple Park Way
Cupertino, California 95014
United States of America
Email: tpauly@apple.com
Eric Kinnear
Apple Inc.
One Apple Park Way
Cupertino, California 95014
United States of America
Email: ekinnear@apple.com
Pauly, et al. Expires April 24, 2020 [Page 7]
Internet-Draft QUIC Datagrams October 2019
David Schinazi
Google LLC
1600 Amphitheatre Parkway
Mountain View, California 94043
United States of America
Email: dschinazi.ietf@gmail.com
Pauly, et al. Expires April 24, 2020 [Page 8]