A new QUIC version for network property communication

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Table of Contents

1. Introduction

The basic idea of the QUIC version described in this document is to create an independent message flow between a client endpoint and devices in the network, in parallel to an end-to-end QUIC connection [RFC 9000], to exchange network properties. This independent flow uses a separate version of QUIC. This document will not describe what information is exchanged for these properties, but rather the overall way in which the communication functions.¶

The new version of QUIC described in this document adheres to the version-independent properties of QUIC specified in RFC 8999. This version of QUIC uses long headers for all its communication. The version of QUIC defined in this document protects packets using publicly known keys, which means that confidentiality and integrity of protocol payload cannot be guaranteed. The document describes how a connection can be upgraded to a QUIC version that supports full TLS protection.¶

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. New QUIC Version

RFC 8999 defines the version independent properties of QUIC to consist of long and short header packets and version negotiation packets. This document defines a new version of QUIC which exclusively uses Long header packets.¶

This version of QUIC has a single packet type, and a set of frame types used to communicate network properties. Furthermore, packets are protected using publicly-know keys, similar to the way Initial packets are protected in QUIC version 1.¶

4. QUIC Long Header Packet Format

This version of QUIC only uses long header packets with the following format:¶

Long Header Packet {
  Header Form (1) = 1,
  Fixed Bit (1) = 0,
  Forward Bit (1) = 0,
  Packet Type (2) = 0,
  Reserved Bits (3),
  Version (32),
  Destination Connection ID Length (8),
  Destination Connection ID (8..160),
  Source Connection ID Length (8),
  Source Connection ID (8..160),
  Payload (..),
}

Header Form:

The most significant bit (0x80) of byte 0 (the first byte) is set to 1 for long headers.¶

Fixed Bit:

The next bit (0x40) of byte 0 is set to 1.¶

Forward Bit:

The next bit (0x20) of byte 0 indicates if a network device that replies to this packet should consume or forward it. By default it SHOULD be set to 0.¶

Packet Type:

The next two bits contain a packet type. A single packet type is defined for this protocol with the value 0b00. Future extensions MAY add new packet types. A network device MUST ignore packets with unknown packet types and SHOULD forward such packets.¶

Reserved Bits:

These bits are reserved for future use and SHOULD be set to 0.¶

Version:

This QUIC version uses the value 0x5509c337, which was chosen at random.¶

Destination Connection ID Length:

The byte following the version contains the length in bytes of the Destination Connection ID field that follows it. This length is encoded as an 8-bit unsigned integer.¶

Destination Connection ID:

The Destination Connection ID field follows the Destination Connection ID Length field, which indicates the length of this field. A Destination Connection ID MUST be at least 8 bytes long.¶

Source Connection ID Length:

The byte following the Destination Connection ID contains the length in bytes of the Source Connection ID field that follows it. This length is encoded as an 8-bit unsigned integer.¶

Source Connection ID:

The Source Connection ID field follows the Source Connection ID Length field, which indicates the length of this field. A Source Connection ID MUST be at least 8 bytes long.¶

5. Packet Protection

This version of QUIC uses packet protection as defined for Initial packets in section 5 of [QUIC-TLS].¶

This version of QUIC does not use packet numbers, therefore nonces are created by combining the initial Destination Connection ID with the Source Connection ID of the packet. A sender MUST generate a Source Connection ID with a high probability of being unique for each packet.¶

6. Frames

The payload of a packet using this QUIC version consists of a sequence of frames. Frames consist of a type field optionally followed by type-specific payload.¶

PADDING Frame {
  Type (i) = 0x00,
}

DATA Frame {
  Type (i) = 0x01,
  Length (i),
  Payload (..),
}

Alternative Hosts Frame {
  Type (i) = 0x02,
  Host (..)..,
}

7. Communication Overview

The goal of this QUIC version is to provide a way to communicate properties between an on-path network device and a QUIC client endpoint, with the QUIC client responsible for the initiation of that communication.¶

Before establishing the communication, a QUIC client usually establishes a QUIC version 1 or 2 end-to-end connection as per RFC 9000. Once this is done, the client opportunistically sends a QUIC long header packet destined to the same endpoint IP address and port using this new version. This packet can be parsed by any capable network element on the path that supports this new QUIC version. If the Forward Bit is set, a capable element MUST forward these packets and send an Alternative Hosts Frame with its own IP address and port number to be used for further communication. This option can be used if more than one capable device might be on the path and needs to see the contents. All capable elements are able to respond to the initial packet in a similar fashion, by creating their own QUIC packets for this QUIC version and sending them to the QUIC client matching the IP/port tuple being utilized by the end-to-end QUIC connection.¶

The QUIC client must be able to distinguish the end-to-end QUIC version 1 or 2 packets and the new QUIC version packets. This can be done by looking for the pattern of packets, combined with trial decryption.¶

8. On Path Verification

Communication using this new QUIC version MUST only be done with network elements that can be verified to be on the same network path as an end to end QUIC flow. This is because this communication is only meant to be done with network elements that have the ability to, for example, modify and drop packets relevant to an end-to-end QUIC flow. As QUIC packets for this new version are themselves carried in separate UDP datagrams from the end to end QUIC flow, there is not an inherent guarantee that they were generated by a network element.¶

A capable network device MUST set the Destination Connection ID Length and Destination Connection ID fields to the values received in the most recently observed new version QUIC packet sent by a client.¶

9. Extensibility To Provide Confidentiality and Authenticity

The use of keys derived from a publicly known salt does not allow for confidentiality or authenticity of the communication. The only manner of authenticity defined in this document is verification of the on-path nature of a network element. It may be desirable for this version of QUIC to be extended to allow for confidentiality and authenticity.¶

Confidentiality with this protocol could be achieved by further leveraging the provisions of QUIC version 1 to do a TLS handshake between the QUIC client and a capable network element. Authenticity could similarly leverage the provisions of TLS. However, this comes with significant complications. TLS achieves authenticity by using Public Key Infrastructure (PKI), where each participant can choose to trust the certificate offered by their peer. While this PKI exists today for Internet endpoints, there is no such existing PKI for network elements. It is important to note that conducting a TLS handshake would restrict the communication between the QUIC client and exactly one on-path network element.¶

Alternatively, a network element could advertise a set of hosts to which the client can connect using QUIC version 1.¶

10. Security Considerations

TODO Security¶

11. IANA Considerations

TBD - QUIC version.¶

12. Normative References

[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/rfc/rfc2119>.

[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/rfc/rfc8174>.

Acknowledgments

TODO acknowledge.¶

Authors' Addresses