draft-ietf-quic-invariants-10.txt   draft-ietf-quic-invariants-11.txt 
QUIC M. Thomson QUIC M. Thomson
Internet-Draft Mozilla Internet-Draft Mozilla
Intended status: Standards Track September 10, 2020 Intended status: Standards Track 25 September 2020
Expires: March 14, 2021 Expires: 29 March 2021
Version-Independent Properties of QUIC Version-Independent Properties of QUIC
draft-ietf-quic-invariants-10 draft-ietf-quic-invariants-11
Abstract Abstract
This document defines the properties of the QUIC transport protocol This document defines the properties of the QUIC transport protocol
that are expected to remain unchanged over time as new versions of that are expected to remain unchanged over time as new versions of
the protocol are developed. the protocol are developed.
Note to Readers Note to Readers
Discussion of this draft takes place on the QUIC working group Discussion of this draft takes place on the QUIC working group
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 14, 2021. This Internet-Draft will expire on 29 March 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Provisions Relating to IETF Documents (https://trustee.ietf.org/ Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document. license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components and restrictions with respect to this document. Code Components
extracted from this document must include Simplified BSD License text extracted from this document must include Simplified BSD License text
as described in Section 4.e of the Trust Legal Provisions and are as described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License. provided without warranty as described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. An Extremely Abstract Description of QUIC . . . . . . . . . . 2
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3 2. Fixed Properties of All QUIC Versions . . . . . . . . . . . . 2
3. An Extremely Abstract Description of QUIC . . . . . . . . . . 3 3. Conventions and Definitions . . . . . . . . . . . . . . . . . 3
4. Notational Conventions . . . . . . . . . . . . . . . . . . . 3 4. Notational Conventions . . . . . . . . . . . . . . . . . . . 3
5. QUIC Packets . . . . . . . . . . . . . . . . . . . . . . . . 4 5. QUIC Packets . . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Long Header . . . . . . . . . . . . . . . . . . . . . . . 4 5.1. Long Header . . . . . . . . . . . . . . . . . . . . . . . 4
5.2. Short Header . . . . . . . . . . . . . . . . . . . . . . 5 5.2. Short Header . . . . . . . . . . . . . . . . . . . . . . 5
5.3. Connection ID . . . . . . . . . . . . . . . . . . . . . . 6 5.3. Connection ID . . . . . . . . . . . . . . . . . . . . . . 6
5.4. Version . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.4. Version . . . . . . . . . . . . . . . . . . . . . . . . . 6
6. Version Negotiation . . . . . . . . . . . . . . . . . . . . . 6 6. Version Negotiation . . . . . . . . . . . . . . . . . . . . . 6
7. Security and Privacy Considerations . . . . . . . . . . . . . 8 7. Security and Privacy Considerations . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1. Normative References . . . . . . . . . . . . . . . . . . 8 9.1. Normative References . . . . . . . . . . . . . . . . . . 8
9.2. Informative References . . . . . . . . . . . . . . . . . 8 9.2. Informative References . . . . . . . . . . . . . . . . . 8
Appendix A. Incorrect Assumptions . . . . . . . . . . . . . . . 9 Appendix A. Incorrect Assumptions . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. An Extremely Abstract Description of QUIC
QUIC is a connection-oriented protocol between two endpoints. Those
endpoints exchange UDP datagrams. These UDP datagrams contain QUIC
packets. QUIC endpoints use QUIC packets to establish a QUIC
connection, which is shared protocol state between those endpoints.
2. Fixed Properties of All QUIC Versions
In addition to providing secure, multiplexed transport, QUIC In addition to providing secure, multiplexed transport, QUIC
[QUIC-TRANSPORT] includes the ability to negotiate a version. This [QUIC-TRANSPORT] allows for the option to negotiate a version. This
allows the protocol to change over time in response to new allows the protocol to change over time in response to new
requirements. Many characteristics of the protocol will change requirements. Many characteristics of the protocol could change
between versions. between versions.
This document describes the subset of QUIC that is intended to remain This document describes the subset of QUIC that is intended to remain
stable as new versions are developed and deployed. All of these stable as new versions are developed and deployed. All of these
invariants are IP-version-independent. invariants are IP-version-independent.
The primary goal of this document is to ensure that it is possible to The primary goal of this document is to ensure that it is possible to
deploy new versions of QUIC. By documenting the properties that deploy new versions of QUIC. By documenting the properties that
cannot change, this document aims to preserve the ability for QUIC cannot change, this document aims to preserve the ability for QUIC
endpoints to negotiate changes to any other aspect of the protocol. endpoints to negotiate changes to any other aspect of the protocol.
As a consequence, this also guarantees a minimal amount of As a consequence, this also guarantees a minimal amount of
information that is made available to entities other than endpoints. information that is made available to entities other than endpoints.
Unless specifically prohibited in this document, any aspect of the Unless specifically prohibited in this document, any aspect of the
protocol can change between different versions. protocol can change between different versions.
Appendix A is a non-exhaustive list of some incorrect assumptions Appendix A is a non-exhaustive list of some incorrect assumptions
that might be made based on knowledge of QUIC version 1; these do not that might be made based on knowledge of QUIC version 1; these do not
apply to every version of QUIC. apply to every version of QUIC.
2. Conventions and Definitions 3. Conventions and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
This document uses terms and notational conventions from This document uses terms and notational conventions from
[QUIC-TRANSPORT]. [QUIC-TRANSPORT].
3. An Extremely Abstract Description of QUIC
QUIC is a connection-oriented protocol between two endpoints. Those
endpoints exchange UDP datagrams. These UDP datagrams contain QUIC
packets. QUIC endpoints use QUIC packets to establish a QUIC
connection, which is shared protocol state between those endpoints.
4. Notational Conventions 4. Notational Conventions
Packet diagrams in this document use a format defined in Packet diagrams in this document use a format defined in
[QUIC-TRANSPORT] to illustrate the order and size of fields. [QUIC-TRANSPORT] to illustrate the order and size of fields.
Complex fields are named and then followed by a list of fields Complex fields are named and then followed by a list of fields
surrounded by a pair of matching braces. Each field in this list is surrounded by a pair of matching braces. Each field in this list is
separated by commas. separated by commas.
Individual fields include length information, plus indications about Individual fields include length information, plus indications about
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5.3. Connection ID 5.3. Connection ID
A connection ID is an opaque field of arbitrary length. A connection ID is an opaque field of arbitrary length.
The primary function of a connection ID is to ensure that changes in The primary function of a connection ID is to ensure that changes in
addressing at lower protocol layers (UDP, IP, and below) do not cause addressing at lower protocol layers (UDP, IP, and below) do not cause
packets for a QUIC connection to be delivered to the wrong QUIC packets for a QUIC connection to be delivered to the wrong QUIC
endpoint. The connection ID is used by endpoints and the endpoint. The connection ID is used by endpoints and the
intermediaries that support them to ensure that each QUIC packet can intermediaries that support them to ensure that each QUIC packet can
be delivered to the correct instance of an endpoint. At the be delivered to the correct instance of an endpoint. At the
endpoint, the connection ID is used to identify which QUIC connection endpoint, the connection ID is used to identify the QUIC connection
the packet is intended for. for which the packet is intended.
The connection ID is chosen by each endpoint using version-specific The connection ID is chosen by each endpoint using version-specific
methods. Packets for the same QUIC connection might use different methods. Packets for the same QUIC connection might use different
connection ID values. connection ID values.
5.4. Version 5.4. Version
The Version field contains a 4-byte identifier. This value can be The Version field contains a 4-byte identifier. This value can be
used by endpoints to identify a QUIC Version. A Version field with a used by endpoints to identify a QUIC Version. A Version field with a
value of 0x00000000 is reserved for version negotiation; see value of 0x00000000 is reserved for version negotiation; see
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the version that it decides to use for subsequent packets. The the version that it decides to use for subsequent packets. The
conditions under which an endpoint changes QUIC version will depend conditions under which an endpoint changes QUIC version will depend
on the version of QUIC that it chooses. on the version of QUIC that it chooses.
See [QUIC-TRANSPORT] for a more thorough description of how an See [QUIC-TRANSPORT] for a more thorough description of how an
endpoint that supports QUIC version 1 generates and consumes a endpoint that supports QUIC version 1 generates and consumes a
Version Negotiation packet. Version Negotiation packet.
7. Security and Privacy Considerations 7. Security and Privacy Considerations
It is possible that middleboxes could use traits of a specific It is possible that middleboxes could observe traits of a specific
version of QUIC and assume that when other versions of QUIC exhibit version of QUIC and assume that when other versions of QUIC exhibit
similar traits the same underlying semantic is being expressed. similar traits the same underlying semantic is being expressed.
There are potentially many such traits (see Appendix A). Some effort There are potentially many such traits; see Appendix A. Some effort
has been made to either eliminate or obscure some observable traits has been made to either eliminate or obscure some observable traits
in QUIC version 1, but many of these remain. Other QUIC versions in QUIC version 1, but many of these remain. Other QUIC versions
might make different design decisions and so exhibit different might make different design decisions and so exhibit different
traits. traits.
The QUIC version number does not appear in all QUIC packets, which The QUIC version number does not appear in all QUIC packets, which
means that reliably extracting information from a flow based on means that reliably extracting information from a flow based on
version-specific traits requires that middleboxes retain state for version-specific traits requires that middleboxes retain state for
every connection ID they see. every connection ID they see.
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<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
9.2. Informative References 9.2. Informative References
[QUIC-TLS] Thomson, M., Ed. and S. Turner, Ed., "Using Transport [QUIC-TLS] Thomson, M., Ed. and S. Turner, Ed., "Using Transport
Layer Security (TLS) to Secure QUIC", Work in Progress, Layer Security (TLS) to Secure QUIC", Work in Progress,
Internet-Draft, draft-ietf-quic-tls-30, September 10, Internet-Draft, draft-ietf-quic-tls-31, 25 September 2020,
2020, <https://tools.ietf.org/html/draft-ietf-quic-tls-31>.
<https://tools.ietf.org/html/draft-ietf-quic-tls-30>.
[QUIC-TRANSPORT] [QUIC-TRANSPORT]
Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", Work in Progress, Multiplexed and Secure Transport", Work in Progress,
Internet-Draft, draft-ietf-quic-transport-30, September Internet-Draft, draft-ietf-quic-transport-31, 25 September
10, 2020, <https://tools.ietf.org/html/draft-ietf-quic- 2020, <https://tools.ietf.org/html/draft-ietf-quic-
transport-30>. transport-31>.
[RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated [RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated
Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008, Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008,
<https://www.rfc-editor.org/info/rfc5116>. <https://www.rfc-editor.org/info/rfc5116>.
Appendix A. Incorrect Assumptions Appendix A. Incorrect Assumptions
There are several traits of QUIC version 1 [QUIC-TRANSPORT] that are There are several traits of QUIC version 1 [QUIC-TRANSPORT] that are
not protected from observation, but are nonetheless considered to be not protected from observation, but are nonetheless considered to be
changeable when a new version is deployed. changeable when a new version is deployed.
This section lists a sampling of incorrect assumptions that might be This section lists a sampling of incorrect assumptions that might be
made based on knowledge of QUIC version 1. Some of these statements made based on knowledge of QUIC version 1. Some of these statements
are not even true for QUIC version 1. This is not an exhaustive are not even true for QUIC version 1. This is not an exhaustive
list; it is intended to be illustrative only. list; it is intended to be illustrative only.
The following statements are NOT guaranteed to be true for every QUIC *Any and all of the following statements can be false for a given
version: QUIC version:*
* QUIC uses TLS [QUIC-TLS] and some TLS messages are visible on the * QUIC uses TLS [QUIC-TLS] and some TLS messages are visible on the
wire wire
* QUIC long headers are only exchanged during connection * QUIC long headers are only exchanged during connection
establishment establishment
* Every flow on a given 5-tuple will include a connection * Every flow on a given 5-tuple will include a connection
establishment phase establishment phase
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