draft-ietf-quic-manageability-11.txt   draft-ietf-quic-manageability-12.txt 
Network Working Group M. Kuehlewind Network Working Group M. Kuehlewind
Internet-Draft Ericsson Internet-Draft Ericsson
Intended status: Informational B. Trammell Intended status: Informational B. Trammell
Expires: 23 October 2021 Google Switzerland GmbH Expires: 1 January 2022 Google Switzerland GmbH
21 April 2021 30 June 2021
Manageability of the QUIC Transport Protocol Manageability of the QUIC Transport Protocol
draft-ietf-quic-manageability-11 draft-ietf-quic-manageability-12
Abstract Abstract
This document discusses manageability of the QUIC transport protocol, This document discusses manageability of the QUIC transport protocol,
focusing on the implications of QUIC's design and wire image on focusing on the implications of QUIC's design and wire image on
network operations involving QUIC traffic. Its intended audience is network operations involving QUIC traffic. Its intended audience is
network operators and equipment vendors who rely on the use of network operators and equipment vendors who rely on the use of
transport-aware network functions. transport-aware network functions.
Status of This Memo Status of This Memo
skipping to change at page 1, line 35 skipping to change at page 1, line 35
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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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
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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 23 October 2021. This Internet-Draft will expire on 1 January 2022.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Features of the QUIC Wire Image . . . . . . . . . . . . . . . 4 2. Features of the QUIC Wire Image . . . . . . . . . . . . . . . 3
2.1. QUIC Packet Header Structure . . . . . . . . . . . . . . 4 2.1. QUIC Packet Header Structure . . . . . . . . . . . . . . 4
2.2. Coalesced Packets . . . . . . . . . . . . . . . . . . . . 6 2.2. Coalesced Packets . . . . . . . . . . . . . . . . . . . . 6
2.3. Use of Port Numbers . . . . . . . . . . . . . . . . . . . 6 2.3. Use of Port Numbers . . . . . . . . . . . . . . . . . . . 6
2.4. The QUIC Handshake . . . . . . . . . . . . . . . . . . . 7 2.4. The QUIC Handshake . . . . . . . . . . . . . . . . . . . 6
2.5. Integrity Protection of the Wire Image . . . . . . . . . 11 2.5. Integrity Protection of the Wire Image . . . . . . . . . 11
2.6. Connection ID and Rebinding . . . . . . . . . . . . . . . 11 2.6. Connection ID and Rebinding . . . . . . . . . . . . . . . 11
2.7. Packet Numbers . . . . . . . . . . . . . . . . . . . . . 12 2.7. Packet Numbers . . . . . . . . . . . . . . . . . . . . . 12
2.8. Version Negotiation and Greasing . . . . . . . . . . . . 12 2.8. Version Negotiation and Greasing . . . . . . . . . . . . 12
3. Network-Visible Information about QUIC Flows . . . . . . . . 12 3. Network-Visible Information about QUIC Flows . . . . . . . . 13
3.1. Identifying QUIC Traffic . . . . . . . . . . . . . . . . 13 3.1. Identifying QUIC Traffic . . . . . . . . . . . . . . . . 13
3.1.1. Identifying Negotiated Version . . . . . . . . . . . 13 3.1.1. Identifying Negotiated Version . . . . . . . . . . . 13
3.1.2. First Packet Identification for Garbage Rejection . . 14 3.1.2. First Packet Identification for Garbage Rejection . . 14
3.2. Connection Confirmation . . . . . . . . . . . . . . . . . 14 3.2. Connection Confirmation . . . . . . . . . . . . . . . . . 14
3.3. Distinguishing Acknowledgment Traffic . . . . . . . . . . 15 3.3. Distinguishing Acknowledgment Traffic . . . . . . . . . . 15
3.4. Server Name Indication (SNI) . . . . . . . . . . . . . . 15 3.4. Server Name Indication (SNI) . . . . . . . . . . . . . . 15
3.4.1. Extracting Server Name Indication (SNI) 3.4.1. Extracting Server Name Indication (SNI)
Information . . . . . . . . . . . . . . . . . . . . . 15 Information . . . . . . . . . . . . . . . . . . . . . 15
3.5. Flow Association . . . . . . . . . . . . . . . . . . . . 17 3.5. Flow Association . . . . . . . . . . . . . . . . . . . . 16
3.6. Flow Teardown . . . . . . . . . . . . . . . . . . . . . . 17 3.6. Flow Teardown . . . . . . . . . . . . . . . . . . . . . . 17
3.7. Flow Symmetry Measurement . . . . . . . . . . . . . . . . 17 3.7. Flow Symmetry Measurement . . . . . . . . . . . . . . . . 17
3.8. Round-Trip Time (RTT) Measurement . . . . . . . . . . . . 18 3.8. Round-Trip Time (RTT) Measurement . . . . . . . . . . . . 17
3.8.1. Measuring Initial RTT . . . . . . . . . . . . . . . . 18 3.8.1. Measuring Initial RTT . . . . . . . . . . . . . . . . 18
3.8.2. Using the Spin Bit for Passive RTT Measurement . . . 18 3.8.2. Using the Spin Bit for Passive RTT Measurement . . . 18
4. Specific Network Management Tasks . . . . . . . . . . . . . . 20 4. Specific Network Management Tasks . . . . . . . . . . . . . . 20
4.1. Passive Network Performance Measurement and 4.1. Passive Network Performance Measurement and
Troubleshooting . . . . . . . . . . . . . . . . . . . . 20 Troubleshooting . . . . . . . . . . . . . . . . . . . . 20
4.2. Stateful Treatment of QUIC Traffic . . . . . . . . . . . 20 4.2. Stateful Treatment of QUIC Traffic . . . . . . . . . . . 20
4.3. Address Rewriting to Ensure Routing Stability . . . . . . 22 4.3. Address Rewriting to Ensure Routing Stability . . . . . . 22
4.4. Server Cooperation with Load Balancers . . . . . . . . . 22 4.4. Server Cooperation with Load Balancers . . . . . . . . . 22
4.5. Filtering Behavior . . . . . . . . . . . . . . . . . . . 23 4.5. Filtering Behavior . . . . . . . . . . . . . . . . . . . 23
4.6. UDP Blocking or Throttling . . . . . . . . . . . . . . . 23 4.6. UDP Blocking or Throttling . . . . . . . . . . . . . . . 23
4.7. DDoS Detection and Mitigation . . . . . . . . . . . . . . 24 4.7. DDoS Detection and Mitigation . . . . . . . . . . . . . . 24
4.8. Quality of Service handling and ECMP . . . . . . . . . . 25 4.8. Quality of Service Handling and ECMP Routing . . . . . . 25
4.9. Handling ICMP Messages . . . . . . . . . . . . . . . . . 26 4.9. Handling ICMP Messages . . . . . . . . . . . . . . . . . 25
4.10. Guiding Path MTU . . . . . . . . . . . . . . . . . . . . 26 4.10. Guiding Path MTU . . . . . . . . . . . . . . . . . . . . 26
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
6. Security Considerations . . . . . . . . . . . . . . . . . . . 27 6. Security Considerations . . . . . . . . . . . . . . . . . . . 27
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 28 7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 28
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 28 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 28
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 28 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 28
9.1. Normative References . . . . . . . . . . . . . . . . . . 28 9.1. Normative References . . . . . . . . . . . . . . . . . . 28
9.2. Informative References . . . . . . . . . . . . . . . . . 29 9.2. Informative References . . . . . . . . . . . . . . . . . 29
Appendix A. Distinguishing IETF QUIC and Google QUIC Versions . 32 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32
A.1. Extracting the CRYPTO frame . . . . . . . . . . . . . . . 33
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 34
1. Introduction 1. Introduction
QUIC [QUIC-TRANSPORT] is a new transport protocol that is QUIC [QUIC-TRANSPORT] is a new transport protocol that is
encapsulated in UDP. QUIC integrates TLS [QUIC-TLS] to encrypt all encapsulated in UDP. QUIC integrates TLS [QUIC-TLS] to encrypt all
payload data and most control information. QUIC version 1 was payload data and most control information. QUIC version 1 was
designed primarily as a transport for HTTP, with the resulting designed primarily as a transport for HTTP, with the resulting
protocol being known as HTTP/3 [QUIC-HTTP]. protocol being known as HTTP/3 [QUIC-HTTP].
This document provides guidance for network operations that manage This document provides guidance for network operations that manage
QUIC traffic. This includes guidance on how to interpret and utilize QUIC traffic. This includes guidance on how to interpret and utilize
information that is exposed by QUIC to the network, requirements and information that is exposed by QUIC to the network, requirements and
assumptions of the QUIC design with respect to network treatment, and assumptions of the QUIC design with respect to network treatment, and
a description of how common network management practices will be a description of how common network management practices will be
impacted by QUIC. impacted by QUIC.
QUIC is an end-to-end transport protocol. No information in the QUIC is an end-to-end transport protocol. No information in the
protocol header, even that which can be inspected, is meant to be protocol header, even that which can be inspected, is mutable by the
mutable by the network. This is achieved through integrity network. This is achieved through integrity protection of the wire
protection of the wire image [WIRE-IMAGE]. Encryption of most image [WIRE-IMAGE]. Encryption of most control signaling means that
control signaling means that less information is visible to the less information is visible to the network than is the case with TCP.
network than is the case with TCP.
Integrity protection can also simplify troubleshooting, because none Integrity protection can also simplify troubleshooting, because none
of the nodes on the network path can modify transport layer of the nodes on the network path can modify transport layer
information. However, it does imply that in-network operations that information. However, it means in-network operations that depend on
depend on modification of data are not possible without the modification of data are not possible without the cooperation of an
cooperation of an QUIC endpoint. This might be possible with the QUIC endpoint. This might be possible with the introduction of a
introduction of a proxy which authenticates as an endpoint. Proxy proxy which authenticates as an endpoint. Proxy operations are not
operations are not in scope for this document. in scope for this document.
Network management is not a one-size-fits-all endeavour: practices Network management is not a one-size-fits-all endeavour: practices
considered necessary or even mandatory within enterprise networks considered necessary or even mandatory within enterprise networks
with certain compliance requirements, for example, would be with certain compliance requirements, for example, would be
impermissible on other networks without those requirements. This impermissible on other networks without those requirements. This
document therefore does not make any specific recommendations as to document therefore does not make any specific recommendations as to
which practices should or should not be applied; for each practice, which practices should or should not be applied; for each practice,
it describes what is and is not possible with the QUIC transport it describes what is and is not possible with the QUIC transport
protocol as defined. protocol as defined.
2. Features of the QUIC Wire Image 2. Features of the QUIC Wire Image
In this section, we discuss those aspects of the QUIC transport This section discusses those aspects of the QUIC transport protocol
protocol that have an impact on the design and operation of devices that have an impact on the design and operation of devices that
that forward QUIC packets. Here, we are concerned primarily with the forward QUIC packets. This section is therefore primarily
unencrypted part of QUIC's wire image [WIRE-IMAGE], which we define considering the unencrypted part of QUIC's wire image [WIRE-IMAGE],
as the information available in the packet header in each QUIC which is defined as the information available in the packet header in
packet, and the dynamics of that information. Since QUIC is a each QUIC packet, and the dynamics of that information. Since QUIC
versioned protocol, the wire image of the header format can also is a versioned protocol, the wire image of the header format can also
change from version to version. However, the field that identifies change from version to version. However, the field that identifies
the QUIC version in some packets, and the format of the Version the QUIC version in some packets, and the format of the Version
Negotiation Packet, are both inspectable and invariant Negotiation Packet, are both inspectable and invariant
[QUIC-INVARIANTS]. [QUIC-INVARIANTS].
This document describes version 1 of the QUIC protocol, whose wire This document describes version 1 of the QUIC protocol, whose wire
image is fully defined in [QUIC-TRANSPORT] and [QUIC-TLS]. Features image is fully defined in [QUIC-TRANSPORT] and [QUIC-TLS]. Features
of the wire image described herein may change in future versions of of the wire image described herein may change in future versions of
the protocol, except when specified as an invariant the protocol, except when specified as an invariant
[QUIC-INVARIANTS], and cannot be used to identify QUIC as a protocol [QUIC-INVARIANTS], and cannot be used to identify QUIC as a protocol
or to infer the behavior of future versions of QUIC. or to infer the behavior of future versions of QUIC.
Appendix A provides non-normative guidance on the identification of
QUIC version 1 packets compared to some pre-standard versions.
2.1. QUIC Packet Header Structure 2.1. QUIC Packet Header Structure
QUIC packets may have either a long header or a short header. The QUIC packets may have either a long header or a short header. The
first bit of the QUIC header is the Header Form bit, and indicates first bit of the QUIC header is the Header Form bit, and indicates
which type of header is present. The purpose of this bit is which type of header is present. The purpose of this bit is
invariant across QUIC versions. invariant across QUIC versions.
The long header exposes more information. In version 1 of QUIC, it The long header exposes more information. It contains a version
is used during connection establishment, including version number, as well as source and destination connection IDs for
negotiation, retry, and 0-RTT data. It contains a version number, as associating packets with a QUIC connection. The definition and
well as source and destination connection IDs for grouping packets location of these fields in the QUIC long header are invariant for
belonging to the same flow. The definition and location of these future versions of QUIC, although future versions of QUIC may provide
fields in the QUIC long header are invariant for future versions of additional fields in the long header [QUIC-INVARIANTS].
QUIC, although future versions of QUIC may provide additional fields
in the long header [QUIC-INVARIANTS]. In version 1 of QUIC, the long header is used during connection
establishment to transmit crypto handshake data, perform version
negotiation, retry, and send 0-RTT data.
Short headers contain only an optional destination connection ID and Short headers contain only an optional destination connection ID and
the spin bit for RTT measurement. In version 1 of QUIC, they are the spin bit for RTT measurement. In version 1 of QUIC, they are
used after connection establishment. used after connection establishment.
The following information is exposed in QUIC packet headers in all The following information is exposed in QUIC packet headers in all
versions of QUIC: versions of QUIC:
* version number: the version number is present in the long header, * version number: the version number is present in the long header,
and identifies the version used for that packet. During Version and identifies the version used for that packet. During Version
Negotiation (see Section 17.2.1 of [QUIC-TRANSPORT] and Negotiation (see Section 17.2.1 of [QUIC-TRANSPORT] and
Section 2.8), the version number field has a special value Section 2.8), the version number field has a special value
(0x00000000) that identifies the packet as a Version Negotiation (0x00000000) that identifies the packet as a Version Negotiation
packet. QUIC version 1 uses version 0x00000001. Operators should packet. QUIC version 1 uses version 0x00000001. Operators should
expect to observe packets with other version numbers as a result expect to observe packets with other version numbers as a result
of various Internet experiments, future standards, and greasing. of various Internet experiments, future standards, and greasing
All deployed versions are maintained in an IANA registry (see ([RFC7801]). All deployed versions are maintained in an IANA
Section 22.2 of [QUIC-TRANSPORT]). registry (see Section 22.2 of [QUIC-TRANSPORT]).
* source and destination connection ID: short and long packet * source and destination connection ID: short and long packet
headers carry a destination connection ID, a variable-length field headers carry a destination connection ID, a variable-length field
that can be used to identify the connection associated with a QUIC that can be used to identify the connection associated with a QUIC
packet, for load-balancing and NAT rebinding purposes; see packet, for load-balancing and NAT rebinding purposes; see
Section 4.4 and Section 2.6. Long packet headers additionally Section 4.4 and Section 2.6. Long packet headers additionally
carry a source connection ID. The source connection ID carry a source connection ID. The source connection ID
corresponds to the destination connection ID the source would like corresponds to the destination connection ID the source would like
to have on packets sent to it, and is only present on long packet to have on packets sent to it, and is only present on long packet
headers. On long header packets, the length of the connection IDs headers. On long header packets, the length of the connection IDs
skipping to change at page 6, line 20 skipping to change at page 6, line 8
explicit in both cases. explicit in both cases.
Retry (Section 17.2.5 of [QUIC-TRANSPORT]) and Version Negotiation Retry (Section 17.2.5 of [QUIC-TRANSPORT]) and Version Negotiation
(Section 17.2.1 of [QUIC-TRANSPORT]) packets are not encrypted or (Section 17.2.1 of [QUIC-TRANSPORT]) packets are not encrypted or
obfuscated in any way. For other kinds of packets, version 1 of QUIC obfuscated in any way. For other kinds of packets, version 1 of QUIC
cryptographically obfuscates other information in the packet headers: cryptographically obfuscates other information in the packet headers:
* packet number: All packets except Version Negotiation and Retry * packet number: All packets except Version Negotiation and Retry
packets have an associated packet number; however, this packet packets have an associated packet number; however, this packet
number is encrypted, and therefore not of use to on-path number is encrypted, and therefore not of use to on-path
observers. The offset of the packet number is encoded in long observers. The offset of the packet number can be decoded in long
headers, while it is implicit (depending on destination connection headers, while it is implicit (depending on destination connection
ID length) in short headers. The length of the packet number is ID length) in short headers. The length of the packet number is
cryptographically obfuscated. cryptographically obfuscated.
* key phase: The Key Phase bit, present in short headers, specifies * key phase: The Key Phase bit, present in short headers, specifies
the keys used to encrypt the packet to support key rotation. The the keys used to encrypt the packet to support key rotation. The
Key Phase bit is cryptographically obfuscated. Key Phase bit is cryptographically obfuscated.
2.2. Coalesced Packets 2.2. Coalesced Packets
Multiple QUIC packets may be coalesced into a UDP datagram, with a Multiple QUIC packets may be coalesced into a single UDP datagram,
datagram carrying one or more long header packets followed by zero or with a datagram carrying one or more long header packets followed by
one short header packets. When packets are coalesced, the Length zero or one short header packets. When packets are coalesced, the
fields in the long headers are used to separate QUIC packets; see Length fields in the long headers are used to separate QUIC packets;
Section 12.2 of [QUIC-TRANSPORT]. The length header field is see Section 12.2 of [QUIC-TRANSPORT]. The Length field is variable
variable length, and its position in the header is also variable length, and its position in the header is also variable depending on
depending on the length of the source and destination connection ID; the length of the source and destination connection ID; see
see Section 17.2 of [QUIC-TRANSPORT]. Section 17.2 of [QUIC-TRANSPORT].
2.3. Use of Port Numbers 2.3. Use of Port Numbers
Applications that have a mapping for TCP as well as QUIC are expected Applications that have a mapping for TCP as well as QUIC are expected
to use the same port number for both services. However, as for all to use the same port number for both services. However, as for all
other IETF transports [RFC7605], there is no guarantee that a other IETF transports [RFC7605], there is no guarantee that a
specific application will use a given registered port, or that a specific application will use a given registered port, or that a
given port carries traffic belonging to the respective registered given port carries traffic belonging to the respective registered
service, especially when application layer information is encrypted. service, especially when application layer information is encrypted.
For example, [QUIC-HTTP] specifies the use of Alt-Svc for discovery For example, [QUIC-HTTP] specifies the use of Alt-Svc for discovery
of HTTP/3 services on other ports. of HTTP/3 services on other ports.
Further, as QUIC has a connection ID, it is also possible to maintain Further, as QUIC has a connection ID, it is also possible to maintain
multiple QUIC connections over one 5-tuple. However, if the multiple QUIC connections over one 5-tuple. However, if the
connection ID is zero-length, all packets of the 5-tuple belong to connection ID is zero-length, all packets of the 5-tuple likely
the same QUIC connection. belong to the same QUIC connection.
2.4. The QUIC Handshake 2.4. The QUIC Handshake
New QUIC connections are established using a handshake, which is New QUIC connections are established using a handshake, which is
distinguishable on the wire and contains some information that can be distinguishable on the wire and contains some information that can be
passively observed. passively observed.
To illustrate the information visible in the QUIC wire image during To illustrate the information visible in the QUIC wire image during
the handshake, we first show the general communication pattern the handshake, we first show the general communication pattern
visible in the UDP datagrams containing the QUIC handshake, then visible in the UDP datagrams containing the QUIC handshake, then
examine each of the datagrams in detail. examine each of the datagrams in detail.
The QUIC handshake can normally be recognized on the wire through at The QUIC handshake can normally be recognized on the wire through
least four datagrams we'll call "Client Initial", "Server Initial", four flights of datagrams labelled "Client Initial", "Server
and "Client Completion", and "Server Completion", for purposes of Initial", "Client Completion", and "Server Completion", in the
this illustration, as shown in Figure 1. illustration shown in Figure 1.
Packets in the handshake belong to three separate cryptographic and Packets in the handshake belong to three separate cryptographic and
transport contexts ("Initial", which contains observable payload, and transport contexts ("Initial", which contains observable payload, and
"Handshake" and "1-RTT", which do not). QUIC packets in separate "Handshake" and "1-RTT", which do not). QUIC packets in separate
contexts during the handshake are generally coalesced (see contexts during the handshake can be coalesced (see Section 2.2) in
Section 2.2) in order to reduce the number of UDP datagrams sent order to reduce the number of UDP datagrams sent during the
during the handshake. handshake. QUIC packets can be lost and reordered, so packets within
a flight might not be sent close in time, though the sequence of the
flights will not change, because one flight depends upon the peer's
previous flight.
As shown here, the client can send 0-RTT data as soon as it has sent As shown here, the client can send 0-RTT data as soon as it has sent
its Client Hello, and the server can send 1-RTT data as soon as it its Client Hello, and the server can send 1-RTT data as soon as it
has sent its Server Hello. has sent its Server Hello.
Client Server Client Server
| | | |
+----Client Initial----------------------->| +----Client Initial----------------------->|
+----(zero or more 0RTT)------------------>| +----(zero or more 0RTT)------------------>|
| | | |
|<-----------------------Server Initial----+ |<-----------------------Server Initial----+
|<---------(1RTT encrypted data starts)----+ |<---------(1RTT encrypted data starts)----+
| | | |
+----Client Completion-------------------->| +----Client Completion-------------------->|
+----(1RTT encrypted data starts)--------->| +----(1RTT encrypted data starts)--------->|
| | | |
|<--------------------Server Completion----+ |<--------------------Server Completion----+
| | | |
Figure 1: General communication pattern visible in the QUIC handshake Figure 1: General communication pattern visible in the QUIC handshake
A typical handshake starts with the client sending of a Client
Initial datagram as shown in Figure 2, which elicits a Server Initial
datagram as shown in Figure 3 typically containing three packets: an
Initial packet with the Server Initial, a Handshake packet with the
rest of the server's side of the TLS handshake, and initial 1-RTT
data, if present.
The Client Completion datagram contains at least one Handshake packet A handshake starts with the client sending one or more datagrams
and some also include an Initial packet. containing Initial packets as shown in Figure 2, which elicits the
Server Initial response as shown in Figure 3 typically containing
three types of packets: Initial packet(s) with the beginning of the
server's side of the TLS handshake, Handshake packet(s) with the rest
of the server's portion of the TLS handshake, and 1-RTT packet(s), if
present.
Datagrams that contain a Client Initial Packet (Client Initial, The Client Completion flight contains at least one Handshake packet
Server Initial, and some Client Completion) contain at least 1200 and could also include an Initial packet.
octets of UDP payload. This protects against amplification attacks
and verifies that the network path meets the requirements for the
minimum QUIC IP packet size; see Section 14 of [QUIC-TRANSPORT].
This is accomplished by either adding PADDING frames within the
Initial packet, coalescing other packets with the Initial packet, or
leaving unused payload in the UDP packet after the Initial packet. A
network path needs to be able to forward at least this size of packet
for QUIC to be used.
The content of Client Initial packets are encrypted using Initial Datagrams that contain an Initial packet (Client Initial, Server
Secrets, which are derived from a per-version constant and the Initial, and some Client Completion) contain at least 1200 octets of
client's destination connection ID; they are therefore observable by UDP payload. This protects against amplification attacks and
any on-path device that knows the per-version constant. They are verifies that the network path meets the requirements for the minimum
therefore considered visible in this illustration. The content of QUIC IP packet size; see Section 14 of [QUIC-TRANSPORT]. This is
QUIC Handshake packets are encrypted using keys established during accomplished by either adding PADDING frames within the Initial
the initial handshake exchange, and are therefore not visible. packet, coalescing other packets with the Initial packet, or leaving
unused payload in the UDP packet after the Initial packet. A network
path needs to be able to forward at least this size of packet for
QUIC to be used.
Initial, Handshake, and the Short Header packets transmitted after The content of Initial packets is encrypted using Initial Secrets,
the handshake belong to cryptographic and transport contexts. The which are derived from a per-version constant and the client's
Client Completion Figure 4 and the Server Completion Figure 5 destination connection ID; they are therefore observable by any on-
datagrams finish these first two contexts, by sending the final path device that knows the per-version constant and considered
acknowledgment and finishing the transmission of CRYPTO frames. visible in this illustration. The content of QUIC Handshake packets
are encrypted using keys established during the initial handshake
exchange, and are therefore not visible.
Initial, Handshake, and 1-RTT packets belong to different
cryptographic and transport contexts. The Client Completion Figure 4
and the Server Completion Figure 5 flights conclude the Initial and
Handshake contexts, by sending final acknowledgments and CRYPTO
frames.
+----------------------------------------------------------+ +----------------------------------------------------------+
| UDP header (source and destination UDP ports) | | UDP header (source and destination UDP ports) |
+----------------------------------------------------------+ +----------------------------------------------------------+
| QUIC long header (type = Initial, Version, DCID, SCID) (Length) | QUIC long header (type = Initial, Version, DCID, SCID) (Length)
+----------------------------------------------------------+ | +----------------------------------------------------------+ |
| QUIC CRYPTO frame header | | | QUIC CRYPTO frame header | |
+----------------------------------------------------------+ | +----------------------------------------------------------+ |
| TLS Client Hello (incl. TLS SNI) | | | | TLS Client Hello (incl. TLS SNI) | | |
+----------------------------------------------------------+ | +----------------------------------------------------------+ |
| QUIC PADDING frames | | | QUIC PADDING frames | |
+----------------------------------------------------------+<-+ +----------------------------------------------------------+<-+
Figure 2: Typical Client Initial datagram pattern without 0-RTT Figure 2: Example Client Initial datagram without 0-RTT
The Client Initial datagram exposes version number, source and A Client Initial packet exposes the version, source and destination
destination connection IDs without encryption. Information in the connection IDs without encryption. The payload of the Initial packet
TLS Client Hello frame, including any TLS Server Name Indication is obfuscated using the Initial secret. The complete TLS Client
(SNI) present, is obfuscated using the Initial secret. Note that the Hello, including any TLS Server Name Indication (SNI) present, is
location of PADDING is implementation-dependent, and PADDING frames sent in one or more CRYPTO frames across one or more QUIC Initial
might not appear in a coalesced Initial packet. packets.
+------------------------------------------------------------+ +------------------------------------------------------------+
| UDP header (source and destination UDP ports) | | UDP header (source and destination UDP ports) |
+------------------------------------------------------------+ +------------------------------------------------------------+
| QUIC long header (type = Initial, Version, DCID, SCID) (Length) | QUIC long header (type = Initial, Version, DCID, SCID) (Length)
+------------------------------------------------------------+ | +------------------------------------------------------------+ |
| QUIC CRYPTO frame header | | | QUIC CRYPTO frame header | |
+------------------------------------------------------------+ | +------------------------------------------------------------+ |
| TLS Server Hello | | | TLS Server Hello | |
+------------------------------------------------------------+ | +------------------------------------------------------------+ |
skipping to change at page 9, line 32 skipping to change at page 9, line 25
+------------------------------------------------------------+<-+ +------------------------------------------------------------+<-+
| QUIC long header (type = Handshake, Version, DCID, SCID) (Length) | QUIC long header (type = Handshake, Version, DCID, SCID) (Length)
+------------------------------------------------------------+ | +------------------------------------------------------------+ |
| encrypted payload (presumably CRYPTO frames) | | | encrypted payload (presumably CRYPTO frames) | |
+------------------------------------------------------------+<-+ +------------------------------------------------------------+<-+
| QUIC short header | | QUIC short header |
+------------------------------------------------------------+ +------------------------------------------------------------+
| 1-RTT encrypted payload | | 1-RTT encrypted payload |
+------------------------------------------------------------+ +------------------------------------------------------------+
Figure 3: Typical Server Initial datagram pattern Figure 3: Coalesced Server Initial datagram pattern
The Server Initial datagram also exposes version number, source and The Server Initial datagram also exposes version number, source and
destination connection IDs in the clear; information in the TLS destination connection IDs in the clear; the payload of the Initial
Server Hello message is obfuscated using the Initial secret. packet(s) is obfuscated using the Initial secret.
+------------------------------------------------------------+ +------------------------------------------------------------+
| UDP header (source and destination UDP ports) | | UDP header (source and destination UDP ports) |
+------------------------------------------------------------+ +------------------------------------------------------------+
| QUIC long header (type = Initial, Version, DCID, SCID) (Length) | QUIC long header (type = Initial, Version, DCID, SCID) (Length)
+------------------------------------------------------------+ | +------------------------------------------------------------+ |
| QUIC ACK frame (acknowledging Server Initial Initial) | | | QUIC ACK frame (acknowledging Server Initial) | |
+------------------------------------------------------------+<-+ +------------------------------------------------------------+<-+
| QUIC long header (type = Handshake, Version, DCID, SCID) (Length) | QUIC long header (type = Handshake, Version, DCID, SCID) (Length)
+------------------------------------------------------------+ | +------------------------------------------------------------+ |
| encrypted payload (presumably CRYPTO/ACK frames) | | | encrypted payload (presumably CRYPTO/ACK frames) | |
+------------------------------------------------------------+<-+ +------------------------------------------------------------+<-+
| QUIC short header | | QUIC short header |
+------------------------------------------------------------+ +------------------------------------------------------------+
| 1-RTT encrypted payload | | 1-RTT encrypted payload |
+------------------------------------------------------------+ +------------------------------------------------------------+
Figure 4: Typical Client Completion datagram pattern
The Client Completion datagram does not expose any additional Figure 4: Coalesced Client Completion datagram pattern
information; however, recognizing it can be used to determine that a
handshake has completed (see Section 3.2), and for three-way The Client Completion flight does not expose any additional
handshake RTT estimation as in Section 3.8. information; however, as the destination connection ID is server-
selected, it usually is not the same ID than in the Client Initial.
Client Completion flights contain 1-RTT packets which indicate the
handshake has completed (see Section 3.2) on the client, and for
three-way handshake RTT estimation as in Section 3.8.
+------------------------------------------------------------+ +------------------------------------------------------------+
| UDP header (source and destination UDP ports) | | UDP header (source and destination UDP ports) |
+------------------------------------------------------------+ +------------------------------------------------------------+
| QUIC long header (type = Handshake, Version, DCID, SCID) (Length) | QUIC long header (type = Handshake, Version, DCID, SCID) (Length)
+------------------------------------------------------------+ | +------------------------------------------------------------+ |
| encrypted payload (presumably ACK frame) | | | encrypted payload (presumably ACK frame) | |
+------------------------------------------------------------+<-+ +------------------------------------------------------------+<-+
| QUIC short header | | QUIC short header |
+------------------------------------------------------------+ +------------------------------------------------------------+
| 1-RTT encrypted payload | | 1-RTT encrypted payload |
+------------------------------------------------------------+ +------------------------------------------------------------+
Figure 5: Typical Server Completion datagram pattern Figure 5: Coalesced Server Completion datagram pattern
Similar to Client Completion, Server Completion also exposes no Similar to Client Completion, Server Completion also exposes no
additional information; observing it serves only to determine that additional information; observing it serves only to determine that
the handshake has completed. the handshake has completed.
When the client uses 0-RTT connection resumption, 0-RTT data may also When the client uses 0-RTT connection resumption, the Client Initial
be seen in the Client Initial datagram, as shown in Figure 6. flight can also include one or more 0-RTT packets, as shown in
Figure 6.
+----------------------------------------------------------+ +----------------------------------------------------------+
| UDP header (source and destination UDP ports) | | UDP header (source and destination UDP ports) |
+----------------------------------------------------------+ +----------------------------------------------------------+
| QUIC long header (type = Initial, Version, DCID, SCID) (Length) | QUIC long header (type = Initial, Version, DCID, SCID) (Length)
+----------------------------------------------------------+ | +----------------------------------------------------------+ |
| QUIC CRYPTO frame header | | | QUIC CRYPTO frame header | |
+----------------------------------------------------------+ | +----------------------------------------------------------+ |
| TLS Client Hello (incl. TLS SNI) | | | TLS Client Hello (incl. TLS SNI) | |
+----------------------------------------------------------+<-+ +----------------------------------------------------------+<-+
| QUIC long header (type = 0RTT, Version, DCID, SCID) (Length) | QUIC long header (type = 0RTT, Version, DCID, SCID) (Length)
+----------------------------------------------------------+ | +----------------------------------------------------------+ |
| 0-rtt encrypted payload | | | 0-rtt encrypted payload | |
+----------------------------------------------------------+<-+ +----------------------------------------------------------+<-+
Figure 6: Typical 0-RTT Client Initial datagram pattern Figure 6: Coalesced 0-RTT Client Initial datagram
In a 0-RTT Client Initial datagram, the PADDING frame is only present When a 0-RTT packet is coalesced with an Initial packet, the datagram
if necessary to increase the size of the datagram with 0RTT data to will be padded to 1200 byes. Additional datagrams containing only
at least 1200 bytes. Additional datagrams containing only 0-RTT 0-RTT packets with long headers can be sent after the client Initial
protected long header packets may be sent from the client to the packet(s), containing more 0-RTT data. The amount of 0-RTT protected
server after the Client Initial datagram, containing the rest of the data that can be sent in the first flight is limited by the initial
0-RTT data. The amount of 0-RTT protected data that can be sent in congestion window, typically to around 10 packets (see Section 7.2 of
the first round is limited by the initial congestion window, [QUIC-RECOVERY]).
typically around 10 packets (see Section 7.2 of [QUIC-RECOVERY]).
2.5. Integrity Protection of the Wire Image 2.5. Integrity Protection of the Wire Image
As soon as the cryptographic context is established, all information As soon as the cryptographic context is established, all information
in the QUIC header, including exposed information, is integrity- in the QUIC header, including exposed information, is integrity
protected. Further, information that was exposed in packets sent protected. Further, information that was exposed in packets sent
before the cryptographic context was established is validated during before the cryptographic context was established is validated during
the cryptographic handshake. Therefore, devices on path cannot alter the cryptographic handshake. Therefore, devices on path cannot alter
any information or bits in QUIC packets. Such alterations would any information or bits in QUIC packets. Such alterations would
cause the integrity check to fail, which results in the receiver cause the integrity check to fail, which results in the receiver
discarding the packet. Some parts of Initial packets could be discarding the packet. Some parts of Initial packets could be
altered by removing and re-applying the authenticated encryption altered by removing and re-applying the authenticated encryption
without immediate discard at the receiver. However, the without immediate discard at the receiver. However, the
cryptographic handshake validates most fields and any modifications cryptographic handshake validates most fields and any modifications
in those fields will result in connection establishment failing later in those fields will result in connection establishment failing
on. later.
2.6. Connection ID and Rebinding 2.6. Connection ID and Rebinding
The connection ID in the QUIC packet headers allows association of The connection ID in the QUIC packet headers allows association of
QUIC packets using information independent of the five-tuple. This QUIC packets using information independent of the five-tuple. This
allows rebinding of a connection after one of one endpoint allows rebinding of a connection after one of the endpoints
experienced an address change - usually the client. Further it can experienced an address change - usually the client. Further it can
be used by in-network devices to ensure that related 5-tuple flows be used by in-network devices to ensure that related 5-tuple flows
are appropriately balanced together. are appropriately balanced together.
Client and server negotiate connection IDs during the handshake; Client and server each choose a connection ID during the handshake;
typically, however, only the server will request a connection ID for for example, a server might request that a client use a connection
the lifetime of the connection. Connection IDs for either endpoint ID, whereas the client might choose a zero-length value. Connection
may change during the lifetime of a connection, with the new IDs for either endpoint may change during the lifetime of a
connection ID being supplied via encrypted frames (see Section 5.1 of connection, with the new connection ID being supplied via encrypted
[QUIC-TRANSPORT]). Therefore, observing a new connection ID does not frames (see Section 5.1 of [QUIC-TRANSPORT]). Therefore, observing a
necessary indicate a new connection. new connection ID does not necessarily indicate a new connection.
[QUIC_LB] specifies algorithms for encoding the server mapping in a [QUIC_LB] specifies algorithms for encoding the server mapping in a
connection ID in order to share this information with selected on- connection ID in order to share this information with selected on-
path devices such as load balancers. Server mappings should only be path devices such as load balancers. Server mappings should only be
exposed to selected entities. Uncontrolled exposure would allow exposed to selected entities. Uncontrolled exposure would allow
linkage of multiple IP addresses to the same host if the server also linkage of multiple IP addresses to the same host if the server also
supports migration which opens an attack vector on specific servers supports migration that opens an attack vector on specific servers or
or pools. The best way to obscure an encoding is to appear random to pools. The best way to obscure an encoding is to appear random to
any other observers, which is most rigorously achieved with any other observers, which is most rigorously achieved with
encryption. As a result any attempt to infer information from encryption. As a result, any attempt to infer information from
specific parts of a connection ID is unlikely to be useful. specific parts of a connection ID is unlikely to be useful.
2.7. Packet Numbers 2.7. Packet Numbers
The packet number field is always present in the QUIC packet header The Packet Number field is always present in the QUIC packet header
in version 1; however, it is always encrypted. The encryption key in version 1; however, it is always encrypted. The encryption key
for packet number protection on handshake packets sent before for packet number protection on Initial packets -- which are sent
cryptographic context establishment is specific to the QUIC version, before cryptographic context establishment -- is specific to the QUIC
while packet number protection on subsequent packets uses secrets version, while packet number protection on subsequent packets uses
derived from the end-to-end cryptographic context. Packet numbers secrets derived from the end-to-end cryptographic context. Packet
are therefore not part of the wire image that is visible to on-path numbers are therefore not part of the wire image that is visible to
observers. on-path observers.
2.8. Version Negotiation and Greasing 2.8. Version Negotiation and Greasing
Version Negotiation packets are used by the server to indicate that a Version Negotiation packets are used by the server to indicate that a
requested version from the client is not supported (see Section 6 of requested version from the client is not supported (see Section 6 of
[QUIC-TRANSPORT]. Version Negotiation packets are not intrinsically [QUIC-TRANSPORT]. Version Negotiation packets are not intrinsically
protected, but future QUIC versions will use later encrypted messages protected, but future QUIC versions will use later encrypted messages
to verify that they were authentic. Therefore any modification of to verify that they were authentic. Therefore, any modification of
this list will be detected and may cause the endpoints to terminate this list will be detected and may cause the endpoints to terminate
the connection attempt. the connection attempt.
Also note that the list of versions in the Version Negotiation packet Also note that the list of versions in the Version Negotiation packet
may contain reserved versions. This mechanism is used to avoid may contain reserved versions. This mechanism is used to avoid
ossification in the implementation on the selection mechanism. ossification in the implementation on the selection mechanism.
Further, a client may send a Initial Client packet with a reserved Further, a client may send an Initial packet with a reserved version
version number to trigger version negotiation. In the Version number to trigger version negotiation. In the Version Negotiation
Negotiation packet, the connection IDs of the Client Initial packet packet, the connection IDs of the client's Initial packet are
are reflected to provide a proof of return-routability. Therefore, reflected to provide a proof of return-routability. Therefore,
changing this information will also cause the connection to fail. changing this information will also cause the connection to fail.
QUIC is expected to evolve rapidly, so new versions, both QUIC is expected to evolve rapidly, so new versions, both
experimental and IETF standard versions, will be deployed in the experimental and IETF standard versions, will be deployed on the
Internet more often than with traditional Internet- and transport- Internet more often than with traditional Internet- and transport-
layer protocols. Using a particular version number to recognize layer protocols. Using a particular version number to recognize
valid QUIC traffic is likely to persistently miss a fraction of QUIC valid QUIC traffic is likely to persistently miss a fraction of QUIC
flows and completely fail in the near future, and is therefore not flows and completely fail in the near future, and is therefore not
recommended. In addition, due to the speed of evolution of the recommended. In addition, due to the speed of evolution of the
protocol, devices that attempt to distinguish QUIC traffic from non- protocol, devices that attempt to distinguish QUIC traffic from non-
QUIC traffic for purposes of network admission control should admit QUIC traffic for purposes of network admission control should admit
all QUIC traffic regardless of version. all QUIC traffic regardless of version.
3. Network-Visible Information about QUIC Flows 3. Network-Visible Information about QUIC Flows
This section addresses the different kinds of observations and This section addresses the different kinds of observations and
inferences that can be made about QUIC flows by a passive observer in inferences that can be made about QUIC flows by a passive observer in
the network based on the wire image in Section 2. Here we assume a the network based on the wire image in Section 2. Here we assume a
bidirectional observer (one that can see packets in both directions bidirectional observer (one that can see packets in both directions
in the sequence in which they are carried on the wire) unless noted. in the sequence in which they are carried on the wire) unless noted,
but typically without access to any keying information.
3.1. Identifying QUIC Traffic 3.1. Identifying QUIC Traffic
The QUIC wire image is not specifically designed to be The QUIC wire image is not specifically designed to be
distinguishable from other UDP traffic. distinguishable from other UDP traffic by a passive observer in the
network.
The only application binding defined by the IETF QUIC WG is HTTP/3 The only application binding defined by the IETF QUIC WG is HTTP/3
[QUIC-HTTP] at the time of this writing; however, many other [QUIC-HTTP] at the time of this writing; however, many other
applications are currently being defined and deployed over QUIC, so applications are currently being defined and deployed over QUIC, so
an assumption that all QUIC traffic is HTTP/3 is not valid. HTTP/3 an assumption that all QUIC traffic is HTTP/3 is not valid. HTTP/3
uses UDP port 443 by default, although URLs referring to resources uses UDP port 443 by convention but various methods can be used to
available over HTTP/3 may specify alternate port numbers. Simple specify alternate port numbers. Simple assumptions about whether a
assumptions about whether a given flow is using QUIC based upon a UDP given flow is using QUIC based upon a UDP port number may therefore
port number may therefore not hold; see also Section 5 of [RFC7605]. not hold; see also Section 5 of [RFC7605].
While the second-most-significant bit (0x40) of the first octet is While the second-most-significant bit (0x40) of the first octet is
set to 1 in most QUIC packets of the current version (see Section 2.1 set to 1 in most QUIC packets of the current version (see Section 2.1
and Section 17 of [QUIC-TRANSPORT]), this method of recognizing QUIC and Section 17 of [QUIC-TRANSPORT]), this method of recognizing QUIC
traffic is not reliable. First, it only provides one bit of traffic is not reliable. First, it only provides one bit of
information and is prone to collision with UDP-based protocols other information and is prone to collision with UDP-based protocols other
than those considered in [RFC7983]. Second, this feature of the wire than those considered in [RFC7983]. Second, this feature of the wire
image is not invariant [QUIC-INVARIANTS] and may change in future image is not invariant [QUIC-INVARIANTS] and may change in future
versions of the protocol, or even be negotiated during the handshake versions of the protocol, or even be negotiated during the handshake
via the use of an extension. via the use of an extension.
Even though transport parameters transmitted in the client's Initial Even though transport parameters transmitted in the client's Initial
packet are observable by the network, they cannot be modified by the packet are observable by the network, they cannot be modified by the
network without risking connection failure. Further, the reply from network without causing connection failure. Further, the reply from
the server cannot be observed, so observers on the network cannot the server cannot be observed, so observers on the network cannot
know which parameters are actually in use. know which parameters are actually in use.
3.1.1. Identifying Negotiated Version 3.1.1. Identifying Negotiated Version
An in-network observer assuming that a set of packets belongs to a An in-network observer assuming that a set of packets belongs to a
QUIC flow can infer the version number in use by observing the QUIC flow might infer the version number in use by observing the
handshake: for QUIC version 1, if the version number in the Initial handshake: for QUIC version 1, if the version number in the Initial
packet from a client is the same as the version number in the Initial packet from a client is the same as the version number in the Initial
packet of the server response, that version has been accepted by both packet of the server response, that version has been accepted by both
endpoints to be used for the rest of the connection. endpoints to be used for the rest of the connection.
The negotiated version cannot be identified for flows for which a The negotiated version cannot be identified for flows for which a
handshake is not observed, such as in the case of connection handshake is not observed, such as in the case of connection
migration; however, it might be possible to associate a flow with a migration; however, it might be possible to associate a flow with a
flow for which a version has been identified; see Section 3.5. flow for which a version has been identified; see Section 3.5.
skipping to change at page 14, line 18 skipping to change at page 14, line 23
port known to be associated with QUIC is a valid QUIC packet. This port known to be associated with QUIC is a valid QUIC packet. This
determination supports in-network filtering of garbage UDP packets determination supports in-network filtering of garbage UDP packets
(reflection attacks, random backscatter, etc.). While heuristics (reflection attacks, random backscatter, etc.). While heuristics
based on the first byte of the packet (packet type) could be used to based on the first byte of the packet (packet type) could be used to
separate valid from invalid first packet types, the deployment of separate valid from invalid first packet types, the deployment of
such heuristics is not recommended, as bits in the first byte may such heuristics is not recommended, as bits in the first byte may
have different meanings in future versions of the protocol. have different meanings in future versions of the protocol.
3.2. Connection Confirmation 3.2. Connection Confirmation
This document focuses on QUIC version 1, and this section applies This document focuses on QUIC version 1, and this Connection
only to packets belonging to QUIC version 1 flows; for purposes of Confirmation section applies only to packets belonging to QUIC
on-path observation, it assumes that these packets have been version 1 flows; for purposes of on-path observation, it assumes that
identified as such through the observation of a version number these packets have been identified as such through the observation of
exchange as described above. a version number exchange as described above.
Connection establishment uses Initial and Handshake packets Connection establishment uses Initial and Handshake packets
containing a TLS handshake, and Retry packets that do not contain containing a TLS handshake, and Retry packets that do not contain
parts of the handshake. Connection establishment can therefore be parts of the handshake. Connection establishment can therefore be
detected using heuristics similar to those used to detect TLS over detected using heuristics similar to those used to detect TLS over
TCP. A client initiating a connection may also send data in 0-RTT TCP. A client initiating a connection may also send data in 0-RTT
packets directly after the Initial packet containing the TLS Client packets directly after the Initial packet containing the TLS Client
Hello. Since these packets may be reordered in the network, 0-RTT Hello. Since packets may be reordered or lost in the network, 0-RTT
packets could be seen before the Initial packet. packets could be seen before the Initial packet.
Note that in this version of QUIC, clients send Initial packets Note that in this version of QUIC, clients send Initial packets
before servers do, servers send Handshake packets before clients do, before servers do, servers send Handshake packets before clients do,
and only clients send Initial packets with tokens. Therefore, an and only clients send Initial packets with tokens. Therefore, an
endpoint can be identified as a client or server by an on-path endpoint can be identified as a client or server by an on-path
observer. An attempted connection after Retry can be detected by observer. An attempted connection after Retry can be detected by
correlating the contents of the Retry packet with the Token and the correlating the contents of the Retry packet with the Token and the
Destination Connection ID fields of the new Initial packet. Destination Connection ID fields of the new Initial packet.
3.3. Distinguishing Acknowledgment Traffic 3.3. Distinguishing Acknowledgment Traffic
Some deployed in-network functions distinguish pure-acknowledgment Some deployed in-network functions distinguish pure-acknowledgment
(ACK) packets from packets carrying upper-layer data in order to (ACK) packets from packets carrying upper-layer data in order to
attempt to enhance performance, for example by queueing ACKs attempt to enhance performance, for example by queueing ACKs
differently or manipulating ACK signaling. Distinguishing ACK differently or manipulating ACK signaling [RFC3449]. Distinguishing
packets is trivial in TCP, but not supported by QUIC, since ACK packets is possible in TCP, but is not supported by QUIC, since
acknowledgment signaling is carried inside QUIC's encrypted payload, acknowledgment signaling is carried inside QUIC's encrypted payload,
and ACK manipulation is impossible. Specifically, heuristics and ACK manipulation is impossible. Specifically, heuristics
attempting to distinguish ACK-only packets from payload-carrying attempting to distinguish ACK-only packets from payload-carrying
packets based on packet size are likely to fail, and are not packets based on packet size are likely to fail, and are not
recommended to use as a way to construe internals of QUIC's operation recommended to use as a way to construe internals of QUIC's operation
as those mechanisms can change, e.g., due to the use of extensions. as those mechanisms can change, e.g., due to the use of extensions.
3.4. Server Name Indication (SNI) 3.4. Server Name Indication (SNI)
The client's TLS ClientHello may contain a Server Name Indication The client's TLS ClientHello may contain a Server Name Indication
skipping to change at page 15, line 37 skipping to change at page 15, line 37
supports; an observer can deduce that one of those protocols will be supports; an observer can deduce that one of those protocols will be
used if the connection continues. used if the connection continues.
Work is currently underway in the TLS working group to encrypt the Work is currently underway in the TLS working group to encrypt the
contents of the ClientHello in TLS 1.3 [TLS-ECH]. This would make contents of the ClientHello in TLS 1.3 [TLS-ECH]. This would make
SNI-based application identification impossible by on-path SNI-based application identification impossible by on-path
observation for QUIC and other protocols that use TLS. observation for QUIC and other protocols that use TLS.
3.4.1. Extracting Server Name Indication (SNI) Information 3.4.1. Extracting Server Name Indication (SNI) Information
If the ClientHello is not encrypted, it can be derived from the If the ClientHello is not encrypted, SNI can be derived from the
client's Initial packet by calculating the Initial secret to decrypt client's Initial packet by calculating the Initial secret to decrypt
the packet payload and parsing the QUIC CRYPTO Frame containing the the packet payload and parsing the QUIC CRYPTO frame(s) containing
TLS ClientHello. the TLS ClientHello.
As both the derivation of the Initial secret and the structure of the As both the derivation of the Initial secret and the structure of the
Initial packet itself are version-specific, the first step is always Initial packet itself are version-specific, the first step is always
to parse the version number (second to sixth bytes of the long to parse the version number (the second through fifth bytes of the
header). Note that only long header packets carry the version long header). Note that only long header packets carry the version
number, so it is necessary to also check if the first bit of the QUIC number, so it is necessary to also check if the first bit of the QUIC
packet is set to 1, indicating a long header. packet is set to 1, indicating a long header.
Note that proprietary QUIC versions, that have been deployed before Note that proprietary QUIC versions, that have been deployed before
standardization, might not set the first bit in a QUIC long header standardization, might not set the first bit in a QUIC long header
packet to 1. To parse these versions, example code is provided in packet to 1. However, it is expected that these versions will
the appendix (see Appendix A). However, it is expected that these gradually disappear over time.
versions will gradually disappear over time.
When the version has been identified as QUIC version 1, the packet When the version has been identified as QUIC version 1, the packet
type needs to be verified as an Initial packet by checking that the type needs to be verified as an Initial packet by checking that the
third and fourth bits of the header are both set to 0. Then the third and fourth bits of the header are both set to 0. Then the
Destination Connection ID needs to be extracted to calculate the Destination Connection ID needs to be extracted from the packet. The
Initial secret using the version-specific Initial salt, as described Initial secret is calculated using the version-specific Initial salt,
in Section 5.2 of [QUIC-TLS]. The length of the connection ID is as described in Section 5.2 of [QUIC-TLS]. The length of the
indicated in the 6th byte of the header followed by the connection ID connection ID is indicated in the 6th byte of the header followed by
itself. the connection ID itself.
Note that subsequent Initial packets might contain a Destination
Connection ID other than the one used to generate the Initial secret.
Therefore, attempts to decrypt these packets using the procedure
above might fail unless the Initial secret is retained by the
observer.
To determine the end of the header and find the start of the payload, To determine the end of the header and find the start of the payload,
the packet number length, the source connection ID length, and the the packet number length, the source connection ID length, and the
token length need to be extracted. The packet number length is token length need to be extracted. The packet number length is
defined by the seventh and eight bits of the header as described in defined by the seventh and eight bits of the header as described in
Section 17.2 of [QUIC-TRANSPORT], but is obfuscated as described in Section 17.2 of [QUIC-TRANSPORT], but is obfuscated as described in
Section 5.4 of [QUIC-TLS]. The source connection ID length is Section 5.4 of [QUIC-TLS]. The source connection ID length is
specified in the byte after the destination connection ID. The token specified in the byte after the destination connection ID. The token
length, which follows the source connection ID, is a variable-length length, which follows the source connection ID, is a variable-length
integer as specified in Section 16 of [QUIC-TRANSPORT]. integer as specified in Section 16 of [QUIC-TRANSPORT].
After decryption, the client's Initial packet can be parsed to detect After decryption, the client's Initial packet can be parsed to detect
the CRYPTO frame that contains the TLS ClientHello, which then can be the CRYPTO frame(s) that contains the TLS ClientHello, which then can
parsed similarly to TLS over TCP connections. The client's Initial be parsed similarly to TLS over TCP connections. Note that there can
packet may contain other frames, so the first bytes of each frame be multiple CRYPTO frames, and they might not be in order, so
need to be checked to identify the frame type, and if needed skip reassembling the CRYPTO stream by parsing offsets and lengths is
over it. Note that the length of the frames is dependent on the required. Further, the client's Initial packet may contain other
frame type. In QUIC version 1, the packet is expected to contain frames, so the first bytes of each frame need to be checked to
only CRYPTO frames and optionally PADDING frames. PADDING frames, identify the frame type, and if needed skipped over it. Note that
each consisting of a single zero byte, may occur before, after, or the length of the frames is dependent on the frame type; see
between CRYPTO frames. There might be multiple CRYPTO frames. Section 18 of [QUIC-TRANSPORT]. E.g. PADDING frames, each
Finally, an extension might define additional frame types which could consisting of a single zero byte, may occur before, after, or between
be present. CRYPTO frames. However, extensions might define additional frame
types. If an unknown frame type is encountered, it is impossible to
Note that subsequent Initial packets might contain a Destination know the length of that frame which prevents skipping over it, and
Connection ID other than the one used to generate the Initial secret. therefore parsing fails.
Therefore, attempts to decrypt these packets using the procedure
above might fail unless the Initial secret is retained by the
observer.
3.5. Flow Association 3.5. Flow Association
The QUIC connection ID (see Section 2.6) is designed to allow a The QUIC connection ID (see Section 2.6) is designed to allow a
coordinating on-path device, such as a load-balancer, to associate coordinating on-path device, such as a load-balancer, to associate
two flows when one of the endpoints changes address or port. This two flows when one of the endpoints changes address. This change can
change can be due to NAT rebinding or address migration. be due to NAT rebinding or address migration.
The connection ID must change upon intentional address change by an The connection ID must change upon intentional address change by an
endpoint, and connection ID negotiation is encrypted, so it is not endpoint, and connection ID negotiation is encrypted, so it is not
possible for a passive observer to link intended changes of address possible for a passive observer to link intended changes of address
using the connection ID. using the connection ID.
When one endpoint unintentionally changes its address, as is the case When one endpoint's address unintentionally changes, as is the case
with NAT rebinding, an on-path observer may be able to use the with NAT rebinding, an on-path observer may be able to use the
connection ID to associate the flow on the new address with the flow connection ID to associate the flow on the new address with the flow
on the old address. on the old address.
A network function that attempts to use the connection ID to A network function that attempts to use the connection ID to
associate flows must be robust to the failure of this technique. associate flows must be robust to the failure of this technique.
Since the connection ID may change multiple times during the lifetime Since the connection ID may change multiple times during the lifetime
of a connection, packets with the same five-tuple but different of a connection, packets with the same five-tuple but different
connection IDs might or might not belong to the same connection. connection IDs might or might not belong to the same connection.
Likewise, packets with the same connection ID but different five- Likewise, packets with the same connection ID but different five-
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QUIC explicitly exposes which side of a connection is a client and QUIC explicitly exposes which side of a connection is a client and
which side is a server during the handshake. In addition, the which side is a server during the handshake. In addition, the
symmetry of a flow (whether primarily client-to-server, primarily symmetry of a flow (whether primarily client-to-server, primarily
server-to-client, or roughly bidirectional, as input to basic traffic server-to-client, or roughly bidirectional, as input to basic traffic
classification techniques) can be inferred through the measurement of classification techniques) can be inferred through the measurement of
data rate in each direction. While QUIC traffic is protected and data rate in each direction. While QUIC traffic is protected and
ACKs may be padded, padding is not required. ACKs may be padded, padding is not required.
3.8. Round-Trip Time (RTT) Measurement 3.8. Round-Trip Time (RTT) Measurement
The round-trip time of QUIC flows can be inferred by observation once The round-trip time (RTT) of QUIC flows can be inferred by
per flow, during the handshake, as in passive TCP measurement; this observation once per flow, during the handshake, as in passive TCP
requires parsing of the QUIC packet header and recognition of the measurement; this requires parsing of the QUIC packet header and
handshake, as illustrated in Section 2.4. It can also be inferred recognition of the handshake, as illustrated in Section 2.4. It can
during the flow's lifetime, if the endpoints use the spin bit also be inferred during the flow's lifetime, if the endpoints use the
facility described below and in Section 17.3.1 of [QUIC-TRANSPORT]. spin bit facility described below and in Section 17.3.1 of
[QUIC-TRANSPORT].
3.8.1. Measuring Initial RTT 3.8.1. Measuring Initial RTT
In the common case, the delay between the client's Initial packet In the common case, the delay between the client's Initial packet
(containing the TLS ClientHello) and the server's Initial packet (containing the TLS ClientHello) and the server's Initial packet
(containing the TLS ServerHello) represents the RTT component on the (containing the TLS ServerHello) represents the RTT component on the
path between the observer and the server. The delay between the path between the observer and the server. The delay between the
server's first Handshake packet and the Handshake packet sent by the server's first Handshake packet and the Handshake packet sent by the
client represents the RTT component on the path between the observer client represents the RTT component on the path between the observer
and the client. While the client may send 0-RTT packets after the and the client. While the client may send 0-RTT packets after the
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use of the spin bit by default, others only in specific deployment use of the spin bit by default, others only in specific deployment
scenarios, e.g. for servers and clients where the RTT would reveal scenarios, e.g. for servers and clients where the RTT would reveal
the presence of a VPN or proxy. To avoid making these connections the presence of a VPN or proxy. To avoid making these connections
identifiable based on the usage of the spin bit, all endpoints identifiable based on the usage of the spin bit, all endpoints
randomly disable "spinning" for at least one eighth of connections, randomly disable "spinning" for at least one eighth of connections,
even if otherwise enabled by default. An endpoint not participating even if otherwise enabled by default. An endpoint not participating
in spin bit signaling for a given connection can use a fixed spin in spin bit signaling for a given connection can use a fixed spin
value for the duration of the connection, or can set the bit randomly value for the duration of the connection, or can set the bit randomly
on each packet sent. on each packet sent.
When in use and a QUIC flow sends data continuously, the latency spin When in use, the latency spin bit in each direction changes value
bit in each direction changes value once per round-trip time (RTT). once per RTT any time that both endpoints are sending packets
An on-path observer can observe the time difference between edges continuously. An on-path observer can observe the time difference
(changes from 1 to 0 or 0 to 1) in the spin bit signal in a single between edges (changes from 1 to 0 or 0 to 1) in the spin bit signal
direction to measure one sample of end-to-end RTT. This mechanism in a single direction to measure one sample of end-to-end RTT. This
follows the principles of protocol measurability laid out in [IPIM]. mechanism follows the principles of protocol measurability laid out
in [IPIM].
Note that this measurement, as with passive RTT measurement for TCP, Note that this measurement, as with passive RTT measurement for TCP,
includes any transport protocol delay (e.g., delayed sending of includes any transport protocol delay (e.g., delayed sending of
acknowledgements) and/or application layer delay (e.g., waiting for a acknowledgments) and/or application layer delay (e.g., waiting for a
response to be generated). It therefore provides devices on path a response to be generated). It therefore provides devices on path a
good instantaneous estimate of the RTT as experienced by the good instantaneous estimate of the RTT as experienced by the
application. application.
However, application-limited and flow-control-limited senders can However, application-limited and flow-control-limited senders can
have application and transport layer delay, respectively, that are have application and transport layer delay, respectively, that are
much greater than network RTT. When the sender is application- much greater than network RTT. When the sender is application-
limited and e.g. only sends small amount of periodic application limited and e.g. only sends small amount of periodic application
traffic, where that period is longer than the RTT, measuring the spin traffic, where that period is longer than the RTT, measuring the spin
bit provides information about the application period, not the bit provides information about the application period, not the
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4. Specific Network Management Tasks 4. Specific Network Management Tasks
In this section, we review specific network management and In this section, we review specific network management and
measurement techniques and how QUIC's design impacts them. measurement techniques and how QUIC's design impacts them.
4.1. Passive Network Performance Measurement and Troubleshooting 4.1. Passive Network Performance Measurement and Troubleshooting
Limited RTT measurement is possible by passive observation of QUIC Limited RTT measurement is possible by passive observation of QUIC
traffic; see Section 3.8. No passive measurement of loss is possible traffic; see Section 3.8. No passive measurement of loss is possible
with the present wire image. Extremely limited observation of with the present wire image. Limited observation of upstream
upstream congestion may be possible via the observation of CE congestion may be possible via the observation of CE markings on ECN-
markings on ECN-enabled QUIC traffic. enabled QUIC traffic.
On-path devices can also make measurements of RTT, loss and other
performance metrics when information is carried in an additional
network-layer packet header (Section 6 of
[I-D.ietf-tsvwg-transport-encrypt] describes use of operations,
administration and management (OAM) information). Using network-
layer approaches also has the advantage that common observation and
analysis tools can be consistently used by multiple transport
protocols, however, these techniques are often limited to
measurements within one or multiple cooperating domains.
4.2. Stateful Treatment of QUIC Traffic 4.2. Stateful Treatment of QUIC Traffic
Stateful treatment of QUIC traffic (e.g., at a firewall or NAT Stateful treatment of QUIC traffic (e.g., at a firewall or NAT
middlebox) is possible through QUIC traffic and version middlebox) is possible through QUIC traffic and version
identification (Section 3.1) and observation of the handshake for identification (Section 3.1) and observation of the handshake for
connection confirmation (Section 3.2). The lack of any visible end- connection confirmation (Section 3.2). The lack of any visible end-
of-flow signal (Section 3.6) means that this state must be purged of-flow signal (Section 3.6) means that this state must be purged
either through timers or through least-recently-used eviction, either through timers or through least-recently-used eviction,
depending on application requirements. depending on application requirements.
While QUIC has no clear network-visible end-of-connection signal and While QUIC has no clear network-visible end-of-connection signal and
therefore does require timer-based state removal, the QUIC handshake therefore does require timer-based state removal, the QUIC handshake
indicates confirmation by both ends of a valid bidirectional indicates confirmation by both ends of a valid bidirectional
transmission. As soon as the handshake completed, timers should be transmission. As soon as the handshake completed, timers should be
set long enough to also allow for short idle time during a valid set long enough to also allow for short idle time during a valid
transmission. transmission.
[RFC4787] requires a timeout that is not less than 2 minutes for most [RFC4787] requires a network state timeout that is not less than 2
UDP traffic. However, in practice, timers are sometimes lower, in minutes for most UDP traffic. However, in practice, a QUIC endpoint
the range of 30 to 60 seconds. In contrast, [RFC5382] recommends a can experience lower timeouts, in the range of 30 to 60 seconds.
timeout of more than 2 hours for TCP, given that TCP is a connection-
oriented protocol with well- defined closure semantics.
Even though QUIC has explicitly been designed tolerate NAT In contrast, [RFC5382] recommends a state timeout of more than 2
rebindings, decreasing the NAT timeout is not recommended, as it may hours for TCP, given that TCP is a connection-oriented protocol with
negatively impact application performance or incentivize endpoints to well- defined closure semantics. Even though QUIC has explicitly
send very frequent keep-alive packets. Instead it is recommended, been designed to tolerate NAT rebindings, decreasing the NAT timeout
even when lower timers are used for other UDP traffic, to use a timer is not recommended, as it may negatively impact application
of at least two minutes for QUIC traffic. performance or incentivize endpoints to send very frequent keep-alive
packets.
The recommendation is therefore that, even when lower state timeouts
are used for other UDP traffic, a state timeout of at least two
minutes ought to be used for QUIC traffic.
If state is removed too early, this could lead to black-holing of If state is removed too early, this could lead to black-holing of
incoming packets after a short idle period. To detect this incoming packets after a short idle period. To detect this
situation, a timer at the client needs to expire before a re- situation, a timer at the client needs to expire before a re-
establishment can happen (if at all), which would lead to unnecessary establishment can happen (if at all), which would lead to unnecessary
long delays in an otherwise working connection. long delays in an otherwise working connection.
Furthermore, not all endpoints use routing architectures where Furthermore, not all endpoints use routing architectures where
connections will survive a port or address change. So even when the connections will survive a port or address change. So even when the
client revives the connection, a NAT rebinding can cause a routing client revives the connection, a NAT rebinding can cause a routing
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might support address migration. For these reasons, the limits in might support address migration. For these reasons, the limits in
[RFC4787] are important to avoid black-holing of packets (and hence [RFC4787] are important to avoid black-holing of packets (and hence
avoid interrupting the flow of data to the client), especially where avoid interrupting the flow of data to the client), especially where
devices are able to distinguish QUIC traffic from other UDP payloads. devices are able to distinguish QUIC traffic from other UDP payloads.
The QUIC header optionally contains a connection ID which could The QUIC header optionally contains a connection ID which could
provide additional entropy beyond the 5-tuple. The QUIC handshake provide additional entropy beyond the 5-tuple. The QUIC handshake
needs to be observed in order to understand whether the connection ID needs to be observed in order to understand whether the connection ID
is present and what length it has. However, connection IDs may be is present and what length it has. However, connection IDs may be
renegotiated after the handshake, and this renegotiation is not renegotiated after the handshake, and this renegotiation is not
visible to the path. Therefore using the connection ID as a flow key visible to the path. Therefore, using the connection ID as a flow
field for stateful treatment of flows is not recommended as key field for stateful treatment of flows is not recommended as
connection ID changes will cause undetectable and unrecoverable loss connection ID changes will cause undetectable and unrecoverable loss
of state in the middle of a connection. Specially, the use of the of state in the middle of a connection. Specially, the use of the
connection ID for functions that require state to make a forwarding connection ID for functions that require state to make a forwarding
decison is not viable as it will break connectivity or at minimum decison is not viable as it will break connectivity or at minimum
cause long timeout-based delays before this problem is detected by cause long timeout-based delays before this problem is detected by
the endpoints and the connection can potentially be re-established. the endpoints and the connection can potentially be re-established.
Use of connection IDs is specifically discouraged for NAT Use of connection IDs is specifically discouraged for NAT
applications. If a NAT hits an operational limit, it is recommended applications. If a NAT hits an operational limit, it is recommended
to rather drop the initial packets of a flow (see also Section 4.5), to rather drop the initial packets of a flow (see also Section 4.5),
which potentially triggers a fallback to TCP. Use of the connection which potentially triggers a fallback to TCP. Use of the connection
ID to multiplex multiple connections on the same IP address/port pair ID to multiplex multiple connections on the same IP address/port pair
is not a viable solution as it risks connectivity breakage, in case is not a viable solution as it risks connectivity breakage, in case
the connection ID changes. the connection ID changes.
4.3. Address Rewriting to Ensure Routing Stability 4.3. Address Rewriting to Ensure Routing Stability
While QUIC's migration capability makes it possible for an server to While QUIC's migration capability makes it possible for a connection
survive address changes, this does not work if the routers or to survive client address changes, this does not work if the routers
switches in the server infrastructure route using the address-port or switches in the server infrastructure route using the address-port
4-tuple. If infrastructure routes on addresses only, NAT rebinding 4-tuple. If infrastructure routes on addresses only, NAT rebinding
or address migration will cause packets to be delivered to the wrong or address migration will cause packets to be delivered to the wrong
server. [QUIC_LB] describes a way to addresses this problem by server. [QUIC_LB] describes a way to addresses this problem by
coordinating the selection and use of connection IDs between load- coordinating the selection and use of connection IDs between load-
balancers and servers. balancers and servers.
Applying address translation at a middlebox to maintain a stable Applying address translation at a middlebox to maintain a stable
address-port mapping for flows based on connection ID might seem like address-port mapping for flows based on connection ID might seem like
a solution to this problem. However, hiding information about the a solution to this problem. However, hiding information about the
change of the IP address or port conceals important and security- change of the IP address or port conceals important and security-
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function that hides peer address changes prevents the other end from function that hides peer address changes prevents the other end from
detecting and mitigating attacks as the endpoint cannot verify detecting and mitigating attacks as the endpoint cannot verify
connectivity to the new address using QUIC PATH_CHALLENGE and connectivity to the new address using QUIC PATH_CHALLENGE and
PATH_RESPONSE frames. PATH_RESPONSE frames.
In addition, a change of IP address or port is also an input signal In addition, a change of IP address or port is also an input signal
to other internal mechanisms in QUIC. When a path change is to other internal mechanisms in QUIC. When a path change is
detected, path-dependent variables like congestion control parameters detected, path-dependent variables like congestion control parameters
will be reset protecting the new path from overload. will be reset protecting the new path from overload.
Therefore, the use of address rewriting to ensure routing stability
can open QUIC up to various attacks, as it conceals client address
changes, and as such masks important signals that drive security
mechanisms.
4.4. Server Cooperation with Load Balancers 4.4. Server Cooperation with Load Balancers
In the case of networking architectures that include load balancers, In the case of networking architectures that include load balancers,
the connection ID can be used as a way for the server to signal the connection ID can be used as a way for the server to signal
information about the desired treatment of a flow to the load information about the desired treatment of a flow to the load
balancers. Guidance on assigning connection IDs is given in balancers. Guidance on assigning connection IDs is given in
[QUIC-APPLICABILITY]. [QUIC_LB] describes a system for coordinating [QUIC-APPLICABILITY]. [QUIC_LB] describes a system for coordinating
selection and use of connection IDs between load-balancers and selection and use of connection IDs between load-balancers and
servers. servers.
4.5. Filtering Behavior 4.5. Filtering Behavior
[RFC4787] describes possible packet filtering behaviors that relate [RFC4787] describes possible packet filtering behaviors that relate
to NATs but is often also used is other scenarios where packet to NATs but is often also used is other scenarios where packet
filtering is desired. Though the guidance there holds, a filtering is desired. Though the guidance there holds, a
particularly unwise behavior is to admit a handful of UDP packets and particularly unwise behavior admits a handful of UDP packets and then
then make a decision as to whether or not to filter it. QUIC makes a decision to whether or not filter later packets in the same
applications are encouraged to fail over to TCP if early packets do connection. QUIC applications are encouraged to fail over to TCP if
not arrive at their destination [I-D.ietf-quic-applicability], as early packets do not arrive at their destination
QUIC is based on UDP and there are known blocks of UDP traffic (see [I-D.ietf-quic-applicability], as QUIC is based on UDP and there are
Section 4.6). Admitting a few packets allows the QUIC endpoint to known blocks of UDP traffic (see Section 4.6). Admitting a few
determine that the path accepts QUIC. Sudden drops afterwards will packets allows the QUIC endpoint to determine that the path accepts
result in slow and costly timeouts before abandoning the connection. QUIC. Sudden drops afterwards will result in slow and costly
timeouts before abandoning the connection.
4.6. UDP Blocking or Throttling 4.6. UDP Blocking or Throttling
Today, UDP is the most prevalent DDoS vector, since it is easy for Today, UDP is the most prevalent DDoS vector, since it is easy for
compromised non-admin applications to send a flood of large UDP compromised non-admin applications to send a flood of large UDP
packets (while with TCP the attacker gets throttled by the congestion packets (while with TCP the attacker gets throttled by the congestion
controller) or to craft reflection and amplification attacks. Some controller) or to craft reflection and amplification attacks. Some
networks therefore block UDP traffic. With increased deployment of networks therefore block UDP traffic. With increased deployment of
QUIC, there is also an increased need to allow UDP traffic on ports QUIC, there is also an increased need to allow UDP traffic on ports
used for QUIC. However, if UDP is generally enabled on these ports, used for QUIC. However, if UDP is generally enabled on these ports,
UDP flood attacks may also use the same ports. One possible response UDP flood attacks may also use the same ports. One possible response
to this threat is to throttle UDP traffic on the network, allocating to this threat is to throttle UDP traffic on the network, allocating
a fixed portion of the network capacity to UDP and blocking UDP a fixed portion of the network capacity to UDP and blocking UDP
datagrams over that cap. As the portion of QUIC traffic compared to datagrams over that cap. As the portion of QUIC traffic compared to
TCP is also expected to increase over time, using such a limit is not TCP is also expected to increase over time, using such a limit is not
recommended but if done, limits might need to be adapted dynamically. recommended but if done, limits might need to be adapted dynamically.
Further, if UDP traffic is desired to be throttled, it is recommended Further, if UDP traffic is desired to be throttled, it is recommended
to block individual QUIC flows entirely rather than dropping packets to block individual QUIC flows entirely rather than dropping packets
randomly. When the handshake is blocked, QUIC-capable applications indiscriminately. When the handshake is blocked, QUIC-capable
may failover to TCP However, blocking a random fraction of QUIC applications may fail over to TCP. However, blocking a random
packets across 4-tuples will allow many QUIC handshakes to complete, fraction of QUIC packets across 4-tuples will allow many QUIC
preventing a TCP failover, but the connections will suffer from handshakes to complete, preventing a TCP failover, but these
severe packet loss (see also Section 4.5). Therefore UDP throttling connections will suffer from severe packet loss (see also
should be realized by per-flow policing as opposed to per-packet Section 4.5). Therefore, UDP throttling should be realized by per-
policing. Note that this per-flow policing should be stateless to flow policing, as opposed to per-packet policing. Note that this
avoid problems with stateful treatment of QUIC flows (see per-flow policing should be stateless to avoid problems with stateful
Section 4.2), for example blocking a portion of the space of values treatment of QUIC flows (see Section 4.2), for example blocking a
of a hash function over the addresses and ports in the UDP datagram. portion of the space of values of a hash function over the addresses
While QUIC endpoints are often able to survive address changes, e.g. and ports in the UDP datagram. While QUIC endpoints are often able
by NAT rebindings, blocking a portion of the traffic based on 5-tuple to survive address changes, e.g. by NAT rebindings, blocking a
hashing increases the risk of black-holing an active connection when portion of the traffic based on 5-tuple hashing increases the risk of
the address changes. black-holing an active connection when the address changes.
4.7. DDoS Detection and Mitigation 4.7. DDoS Detection and Mitigation
On-path observation of the transport headers of packets can be used On-path observation of the transport headers of packets can be used
for various security functions. For example, Denial of Service (DOS) for various security functions. For example, Denial of Service (DOS)
and Distributed DOS (DDOS) attacks against the infrastructure or and Distributed DOS (DDOS) attacks against the infrastructure or
against an endpoint can be detected and mitigated by characterising against an endpoint can be detected and mitigated by characterising
anomalous traffic. Other uses include support for security audits anomalous traffic. Other uses include support for security audits
(e.g., verifying the compliance with ciphersuites); client and (e.g., verifying the compliance with ciphersuites); client and
application fingerprinting for inventory; and to provide alerts for application fingerprinting for inventory; and to provide alerts for
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Beyond in-network DDoS protection mechanisms, TCP syncookies Beyond in-network DDoS protection mechanisms, TCP syncookies
[RFC4937] are a well-established method of mitigating some kinds of [RFC4937] are a well-established method of mitigating some kinds of
TCP DDoS attacks. QUIC Retry packets are the functional analogue to TCP DDoS attacks. QUIC Retry packets are the functional analogue to
syncookies, forcing clients to prove possession of their IP address syncookies, forcing clients to prove possession of their IP address
before committing server state. However, there are safeguards in before committing server state. However, there are safeguards in
QUIC against unsolicited injection of these packets by intermediaries QUIC against unsolicited injection of these packets by intermediaries
who do not have consent of the end server. See [QUIC_LB] for who do not have consent of the end server. See [QUIC_LB] for
standard ways for intermediaries to send Retry packets on behalf of standard ways for intermediaries to send Retry packets on behalf of
consenting servers. consenting servers.
4.8. Quality of Service handling and ECMP 4.8. Quality of Service Handling and ECMP Routing
It is expected that any QoS handling in the network, e.g. based on It is expected that any QoS handling in the network, e.g. based on
use of DiffServ Code Points (DSCPs) [RFC2475] as well as Equal-Cost use of DiffServ Code Points (DSCPs) [RFC2475] as well as Equal-Cost
Multi-Path (ECMP) routing, is applied on a per flow-basis (and not Multi-Path (ECMP) routing, is applied on a per flow-basis (and not
per-packet) and as such that all packets belonging to the same QUIC per-packet) and as such that all packets belonging to the same QUIC
connection get uniform treatment. Using ECMP to distribute packets connection get uniform treatment.
from a single flow across multiple network paths or any other non-
uniform treatment of packets belong to the same connection could
result in variations in order, delivery rate, and drop rate. As
feedback about loss or delay of each packet is used as input to the
congestion controller, these variations could adversely affect
performance.
Depending of the loss recovery mechanism implemented, QUIC may be Using ECMP to distribute packets from a single flow across multiple
more tolerant of packet re-ordering than traditional TCP traffic (see network paths or any other non-uniform treatment of packets belong to
Section 2.7). However, it cannot be known by the network which exact the same connection could result in variations in order, delivery
recovery mechanism is used and therefore reordering tolerance should rate, and drop rate. As feedback about loss or delay of each packet
be considered as unknown. is used as input to the congestion controller, these variations could
adversely affect performance. Depending on the loss recovery
mechanism implemented, QUIC may be more tolerant of packet re-
ordering than traditional TCP traffic (see Section 2.7). However,
the recovery mechanism used by a flow cannot be known by the network
and therefore reordering tolerance should be considered as unknown.
4.9. Handling ICMP Messages 4.9. Handling ICMP Messages
Datagram Packetization Layer PMTU Discovery (PLPMTUD) can be used by Datagram Packetization Layer PMTU Discovery (PLPMTUD) can be used by
QUIC to probe for the supported PMTU. PLPMTUD optionally uses ICMP QUIC to probe for the supported PMTU. PLPMTUD optionally uses ICMP
messages (e.g., IPv6 Packet Too Big messages). Given known attacks messages (e.g., IPv6 Packet Too Big messages). Given known attacks
with the use of ICMP messages, the use of PLPMTUD in QUIC has been with the use of ICMP messages, the use of PLPMTUD in QUIC has been
designed to safely use but not rely on receiving ICMP feedback (see designed to safely use but not rely on receiving ICMP feedback (see
Section 14.2.1. of [QUIC-TRANSPORT]). Section 14.2.1. of [QUIC-TRANSPORT]).
Networks are recommended to forward these ICMP messages and retain as Networks are recommended to forward these ICMP messages and retain as
much of the original packet as possible without exceeding the minimum much of the original packet as possible without exceeding the minimum
MTU for the IP version when generating ICMP messages as recommended MTU for the IP version when generating ICMP messages as recommended
in [RFC1812] and [RFC4443]. in [RFC1812] and [RFC4443].
4.10. Guiding Path MTU 4.10. Guiding Path MTU
Some networks support 1500-byte packets, but can only do so by Some network segments support 1500-byte packets, but can only do so
fragmenting at a lower layer before traversing a smaller MTU segment, by fragmenting at a lower layer before traversing a network segment
and then reassembling. This is permissible even when the IP layer is with a smaller MTU, and then reassembling within the network segment.
IPv6 or IPv4 with the DF bit set, because it occurs below the IP This is permissible even when the IP layer is IPv6 or IPv4 with the
layer. However, this process can add to compute and memory costs, DF bit set, because fragmention occurs below the IP layer. However,
leading to a bottleneck that limits network capacity. In such this process can add to compute and memory costs, leading to a
networks this generates a desire to influence a majority of senders bottleneck that limits network capacity. In such networks this
to use smaller packets, so that the limited reassembly capacity is generates a desire to influence a majority of senders to use smaller
not exceeded. packets, to avoid exceeding limited reassembly capacity.
For TCP, MSS clamping (Section 3.2 of [RFC4459]) is often used to For TCP, MSS clamping (Section 3.2 of [RFC4459]) is often used to
change the sender's maximum TCP segment size, but QUIC requires a change the sender's TCP maximum segment size, but QUIC requires a
different approach. Section 14 of [QUIC-TRANSPORT] advises senders different approach. Section 14 of [QUIC-TRANSPORT] advises senders
to probe larger sizes using Datagram Packetization Layer PMTU to probe larger sizes using Datagram Packetization Layer PMTU
Discovery ([DPLPMTUD]) or Path Maximum Transmission Unit Discovery Discovery ([DPLPMTUD]) or Path Maximum Transmission Unit Discovery
(PMTUD: [RFC1191] and [RFC8201]). This mechanism will encourage (PMTUD: [RFC1191] and [RFC8201]). This mechanism encourages senders
senders to approach the maximum size, which could cause fragmentation to approach the maximum packet size, which could then cause
with a network segment that they may not be aware of. fragmentation within a network segment of which they may not be
aware.
If path performance is limited when sending larger packets, an on- If path performance is limited when forwarding larger packets, an on-
path device should support a maximum packet size for a specific path device should support a maximum packet size for a specific
transport flow and then consistently drop all packets that exceed the transport flow and then consistently drop all packets that exceed the
configured size when the inner IPv4 packet has DF set, or IPv6 is configured size when the inner IPv4 packet has DF set, or IPv6 is
used. Endpoints can cache PMTU information between IP flows, in the used.
IP-layer cache, so short-term consistency between the PMTU for flows
can help avoid an endpoint using a PMTU that is inefficient.
Networks with configurations that would lead to fragmentation of Networks with configurations that would lead to fragmentation of
large packets should drop such packets rather than fragmenting them. large packets within a network segment should drop such packets
Network operators who plan to implement a more selective policy may rather than fragmenting them. Network operators who plan to
start by focussing on QUIC. QUIC flows cannot always be easily implement a more selective policy may start by focusing on QUIC.
distinguished from other UDP traffic, but we assume at least some
portion of QUIC traffic can be identified (see Section 3.1). For QUIC flows cannot always be easily distinguished from other UDP
QUIC endpoints using DPLPMTUD it is recommended for the path to drop traffic, but we assume at least some portion of QUIC traffic can be
a packet larger than the supported size. A QUIC probe packet is used identified (see Section 3.1). For networks supporting QUIC, it is
to discover the PMTU. If lost, this does not impact the flow of QUIC recommended that a path drops any packet larger than the
data. fragmentation size. When a QUIC endpoint uses DPLPMTUD, it will use
a QUIC probe packet to discover the PMTU. If this probe is lost, it
will not impact the flow of QUIC data.
IPv4 routers generate an ICMP message when a packet is dropped IPv4 routers generate an ICMP message when a packet is dropped
because the link MTU was exceeded. [RFC8504] specifies how an IPv6 because the link MTU was exceeded. [RFC8504] specifies how an IPv6
node generates an ICMPv6 Packet Too Big message (PTB) in this case. node generates an ICMPv6 Packet Too Big message (PTB) in this case.
PMTUD relies upon an endpoint receiving such PTB messages [RFC8201], PMTUD relies upon an endpoint receiving such PTB messages [RFC8201],
whereas DPLPMTUD does not reply upon these messages, but still can whereas DPLPMTUD does not reply upon these messages, but still can
optionally use these to improve performance Section 4.6 of optionally use these to improve performance Section 4.6 of
[DPLPMTUD]. [DPLPMTUD].
Since a network cannot know in advance which discovery method a QUIC A network cannot know in advance which discovery method is used by a
endpoint is using, it should always send a PTB message in addition to QUIC endpoint, so it should send a PTB message in addition to
dropping the oversized packet. A generated PTB message should be dropping an oversized packet. A generated PTB message should be
compliant with the validation requirements of Section 14.2.1 of compliant with the validation requirements of Section 14.2.1 of
[QUIC-TRANSPORT], otherwise it will be ignored by DPLPMTUD. This [QUIC-TRANSPORT], otherwise it will be ignored for PMTU discovery.
will likely provide the right signal for the endpoint to keep the This provides a signal to the endpoint to prevent the packet size
packet size small and thereby avoid network fragmentation for that from growing too large, which can entirely avoid network segment
flow entirely. fragmentation for that flow.
Endpoints can cache PMTU information, in the IP-layer cache. This
short-term consistency between the PMTU for flows can help avoid an
endpoint using a PMTU that is inefficient. The IP cache can also
influence the PMTU value of other IP flows that use the same path
[RFC8201][RFC8899], including IP packets carrying protocols other
than QUIC. The representation of an IP path is implementation-
specific [RFC8201].
5. IANA Considerations 5. IANA Considerations
This document has no actions for IANA. This document has no actions for IANA.
6. Security Considerations 6. Security Considerations
QUIC is an encrypted and authenticated transport. That means, once QUIC is an encrypted and authenticated transport. That means, once
the cryptographic handshake is complete, QUIC endpoints discard most the cryptographic handshake is complete, QUIC endpoints discard most
packets that are not authenticated, greatly limiting the ability of packets that are not authenticated, greatly limiting the ability of
skipping to change at page 28, line 7 skipping to change at page 28, line 7
confidentiality of QUIC's control information; this entire document confidentiality of QUIC's control information; this entire document
is therefore security-relevant. is therefore security-relevant.
More security considerations for QUIC are discussed in More security considerations for QUIC are discussed in
[QUIC-TRANSPORT] and [QUIC-TLS], generally considering active or [QUIC-TRANSPORT] and [QUIC-TLS], generally considering active or
passive attackers in the network as well as attacks on specific QUIC passive attackers in the network as well as attacks on specific QUIC
mechanism. mechanism.
Version Negotiation packets do not contain any mechanism to prevent Version Negotiation packets do not contain any mechanism to prevent
version downgrade attacks. However, future versions of QUIC that use version downgrade attacks. However, future versions of QUIC that use
Version Negotiation packets are require to define a mechanism that is Version Negotiation packets are required to define a mechanism that
robust against version downgrade attacks. Therefore a network node is robust against version downgrade attacks. Therefore, a network
should not attempt to impact version selection, as version downgrade node should not attempt to impact version selection, as version
may result in connection failure. downgrade may result in connection failure.
7. Contributors 7. Contributors
The following people have contributed text to sections of this The following people have contributed text to sections of this
document: document:
* Dan Druta * Dan Druta
* Martin Duke * Martin Duke
skipping to change at page 28, line 49 skipping to change at page 28, line 49
for a Middleboxed Internet (MAMI), and by the Swiss State Secretariat for a Middleboxed Internet (MAMI), and by the Swiss State Secretariat
for Education, Research, and Innovation under contract no. 15.0268. for Education, Research, and Innovation under contract no. 15.0268.
This support does not imply endorsement. This support does not imply endorsement.
9. References 9. References
9.1. Normative References 9.1. Normative References
[QUIC-TLS] Thomson, M. and S. Turner, "Using TLS to Secure QUIC", [QUIC-TLS] Thomson, M. and S. Turner, "Using TLS to Secure QUIC",
Work in Progress, Internet-Draft, draft-ietf-quic-tls-34, Work in Progress, Internet-Draft, draft-ietf-quic-tls-34,
14 January 2021, 14 January 2021, <https://datatracker.ietf.org/doc/html/
<https://tools.ietf.org/html/draft-ietf-quic-tls-34>. draft-ietf-quic-tls-34>.
[QUIC-TRANSPORT] [QUIC-TRANSPORT]
Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed
and Secure Transport", Work in Progress, Internet-Draft, and Secure Transport", Work in Progress, Internet-Draft,
draft-ietf-quic-transport-34, 14 January 2021, draft-ietf-quic-transport-34, 14 January 2021,
<https://tools.ietf.org/html/draft-ietf-quic-transport- <https://datatracker.ietf.org/doc/html/draft-ietf-quic-
34>. transport-34>.
9.2. Informative References 9.2. Informative References
[DOTS-ARCH] [DOTS-ARCH]
Mortensen, A., Reddy, T., Andreasen, F., Teague, N., and Mortensen, A., Ed., Reddy.K, T., Ed., Andreasen, F.,
R. Compton, "DDoS Open Threat Signaling (DOTS) Teague, N., and R. Compton, "DDoS Open Threat Signaling
Architecture", Work in Progress, Internet-Draft, draft- (DOTS) Architecture", RFC 8811, DOI 10.17487/RFC8811,
ietf-dots-architecture-18, 6 March 2020, August 2020, <https://www.rfc-editor.org/rfc/rfc8811>.
<https://tools.ietf.org/html/draft-ietf-dots-architecture-
18>.
[DPLPMTUD] Fairhurst, G., Jones, T., Tüxen, M., Rüngeler, I., and T. [DPLPMTUD] Fairhurst, G., Jones, T., Tüxen, M., Rüngeler, I., and T.
Völker, "Packetization Layer Path MTU Discovery for Völker, "Packetization Layer Path MTU Discovery for
Datagram Transports", RFC 8899, DOI 10.17487/RFC8899, Datagram Transports", RFC 8899, DOI 10.17487/RFC8899,
September 2020, <https://www.rfc-editor.org/rfc/rfc8899>. September 2020, <https://www.rfc-editor.org/rfc/rfc8899>.
[I-D.ietf-quic-applicability] [I-D.ietf-quic-applicability]
Kuehlewind, M. and B. Trammell, "Applicability of the QUIC Kuehlewind, M. and B. Trammell, "Applicability of the QUIC
Transport Protocol", Work in Progress, Internet-Draft, Transport Protocol", Work in Progress, Internet-Draft,
draft-ietf-quic-applicability-11, 21 April 2021, draft-ietf-quic-applicability-11, 21 April 2021,
<https://tools.ietf.org/html/draft-ietf-quic- <https://datatracker.ietf.org/doc/html/draft-ietf-quic-
applicability-11>. applicability-11>.
[I-D.ietf-tsvwg-transport-encrypt]
Fairhurst, G. and C. Perkins, "Considerations around
Transport Header Confidentiality, Network Operations, and
the Evolution of Internet Transport Protocols", Work in
Progress, Internet-Draft, draft-ietf-tsvwg-transport-
encrypt-21, 20 April 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-tsvwg-
transport-encrypt-21>.
[IPIM] Allman, M., Beverly, R., and B. Trammell, "In-Protocol [IPIM] Allman, M., Beverly, R., and B. Trammell, "In-Protocol
Internet Measurement (arXiv preprint 1612.02902)", 9 Internet Measurement (arXiv preprint 1612.02902)", 9
December 2016, <https://arxiv.org/abs/1612.02902>. December 2016, <https://arxiv.org/abs/1612.02902>.
[QUIC-APPLICABILITY] [QUIC-APPLICABILITY]
Kuehlewind, M. and B. Trammell, "Applicability of the QUIC Kuehlewind, M. and B. Trammell, "Applicability of the QUIC
Transport Protocol", Work in Progress, Internet-Draft, Transport Protocol", Work in Progress, Internet-Draft,
draft-ietf-quic-applicability-11, 21 April 2021, draft-ietf-quic-applicability-11, 21 April 2021,
<https://tools.ietf.org/html/draft-ietf-quic- <https://datatracker.ietf.org/doc/html/draft-ietf-quic-
applicability-11>. applicability-11>.
[QUIC-HTTP] [QUIC-HTTP]
Bishop, M., "Hypertext Transfer Protocol Version 3 Bishop, M., "Hypertext Transfer Protocol Version 3
(HTTP/3)", Work in Progress, Internet-Draft, draft-ietf- (HTTP/3)", Work in Progress, Internet-Draft, draft-ietf-
quic-http-34, 2 February 2021, quic-http-34, 2 February 2021,
<https://tools.ietf.org/html/draft-ietf-quic-http-34>. <https://datatracker.ietf.org/doc/html/draft-ietf-quic-
http-34>.
[QUIC-INVARIANTS] [QUIC-INVARIANTS]
Thomson, M., "Version-Independent Properties of QUIC", Thomson, M., "Version-Independent Properties of QUIC",
Work in Progress, Internet-Draft, draft-ietf-quic- Work in Progress, Internet-Draft, draft-ietf-quic-
invariants-13, 14 January 2021, invariants-13, 14 January 2021,
<https://tools.ietf.org/html/draft-ietf-quic-invariants- <https://datatracker.ietf.org/doc/html/draft-ietf-quic-
13>. invariants-13>.
[QUIC-RECOVERY] [QUIC-RECOVERY]
Iyengar, J. and I. Swett, "QUIC Loss Detection and Iyengar, J. and I. Swett, "QUIC Loss Detection and
Congestion Control", Work in Progress, Internet-Draft, Congestion Control", Work in Progress, Internet-Draft,
draft-ietf-quic-recovery-34, 14 January 2021, draft-ietf-quic-recovery-34, 14 January 2021,
<https://tools.ietf.org/html/draft-ietf-quic-recovery-34>. <https://datatracker.ietf.org/doc/html/draft-ietf-quic-
recovery-34>.
[QUIC_LB] Duke, M. and N. Banks, "QUIC-LB: Generating Routable QUIC [QUIC_LB] Duke, M. and N. Banks, "QUIC-LB: Generating Routable QUIC
Connection IDs", Work in Progress, Internet-Draft, draft- Connection IDs", Work in Progress, Internet-Draft, draft-
ietf-quic-load-balancers-06, 4 February 2021, ietf-quic-load-balancers-06, 4 February 2021,
<https://tools.ietf.org/html/draft-ietf-quic-load- <https://datatracker.ietf.org/doc/html/draft-ietf-quic-
balancers-06>. load-balancers-06>.
[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, [RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
DOI 10.17487/RFC1191, November 1990, DOI 10.17487/RFC1191, November 1990,
<https://www.rfc-editor.org/rfc/rfc1191>. <https://www.rfc-editor.org/rfc/rfc1191>.
[RFC1812] Baker, F., Ed., "Requirements for IP Version 4 Routers", [RFC1812] Baker, F., Ed., "Requirements for IP Version 4 Routers",
RFC 1812, DOI 10.17487/RFC1812, June 1995, RFC 1812, DOI 10.17487/RFC1812, June 1995,
<https://www.rfc-editor.org/rfc/rfc1812>. <https://www.rfc-editor.org/rfc/rfc1812>.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, DOI 10.17487/RFC2475, December 1998, Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
<https://www.rfc-editor.org/rfc/rfc2475>. <https://www.rfc-editor.org/rfc/rfc2475>.
[RFC3449] Balakrishnan, H., Padmanabhan, V., Fairhurst, G., and M.
Sooriyabandara, "TCP Performance Implications of Network
Path Asymmetry", BCP 69, RFC 3449, DOI 10.17487/RFC3449,
December 2002, <https://www.rfc-editor.org/rfc/rfc3449>.
[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", STD 89, Protocol Version 6 (IPv6) Specification", STD 89,
RFC 4443, DOI 10.17487/RFC4443, March 2006, RFC 4443, DOI 10.17487/RFC4443, March 2006,
<https://www.rfc-editor.org/rfc/rfc4443>. <https://www.rfc-editor.org/rfc/rfc4443>.
[RFC4459] Savola, P., "MTU and Fragmentation Issues with In-the- [RFC4459] Savola, P., "MTU and Fragmentation Issues with In-the-
Network Tunneling", RFC 4459, DOI 10.17487/RFC4459, April Network Tunneling", RFC 4459, DOI 10.17487/RFC4459, April
2006, <https://www.rfc-editor.org/rfc/rfc4459>. 2006, <https://www.rfc-editor.org/rfc/rfc4459>.
skipping to change at page 31, line 28 skipping to change at page 31, line 43
[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan, [RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol "Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301, Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <https://www.rfc-editor.org/rfc/rfc7301>. July 2014, <https://www.rfc-editor.org/rfc/rfc7301>.
[RFC7605] Touch, J., "Recommendations on Using Assigned Transport [RFC7605] Touch, J., "Recommendations on Using Assigned Transport
Port Numbers", BCP 165, RFC 7605, DOI 10.17487/RFC7605, Port Numbers", BCP 165, RFC 7605, DOI 10.17487/RFC7605,
August 2015, <https://www.rfc-editor.org/rfc/rfc7605>. August 2015, <https://www.rfc-editor.org/rfc/rfc7605>.
[RFC7801] Dolmatov, V., Ed., "GOST R 34.12-2015: Block Cipher
"Kuznyechik"", RFC 7801, DOI 10.17487/RFC7801, March 2016,
<https://www.rfc-editor.org/rfc/rfc7801>.
[RFC7983] Petit-Huguenin, M. and G. Salgueiro, "Multiplexing Scheme [RFC7983] Petit-Huguenin, M. and G. Salgueiro, "Multiplexing Scheme
Updates for Secure Real-time Transport Protocol (SRTP) Updates for Secure Real-time Transport Protocol (SRTP)
Extension for Datagram Transport Layer Security (DTLS)", Extension for Datagram Transport Layer Security (DTLS)",
RFC 7983, DOI 10.17487/RFC7983, September 2016, RFC 7983, DOI 10.17487/RFC7983, September 2016,
<https://www.rfc-editor.org/rfc/rfc7983>. <https://www.rfc-editor.org/rfc/rfc7983>.
[RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed.,
"Path MTU Discovery for IP version 6", STD 87, RFC 8201, "Path MTU Discovery for IP version 6", STD 87, RFC 8201,
DOI 10.17487/RFC8201, July 2017, DOI 10.17487/RFC8201, July 2017,
<https://www.rfc-editor.org/rfc/rfc8201>. <https://www.rfc-editor.org/rfc/rfc8201>.
[RFC8504] Chown, T., Loughney, J., and T. Winters, "IPv6 Node [RFC8504] Chown, T., Loughney, J., and T. Winters, "IPv6 Node
Requirements", BCP 220, RFC 8504, DOI 10.17487/RFC8504, Requirements", BCP 220, RFC 8504, DOI 10.17487/RFC8504,
January 2019, <https://www.rfc-editor.org/rfc/rfc8504>. January 2019, <https://www.rfc-editor.org/rfc/rfc8504>.
[RFC8899] Fairhurst, G., Jones, T., Tüxen, M., Rüngeler, I., and T.
Völker, "Packetization Layer Path MTU Discovery for
Datagram Transports", RFC 8899, DOI 10.17487/RFC8899,
September 2020, <https://www.rfc-editor.org/rfc/rfc8899>.
[TLS-ECH] Rescorla, E., Oku, K., Sullivan, N., and C. A. Wood, "TLS [TLS-ECH] Rescorla, E., Oku, K., Sullivan, N., and C. A. Wood, "TLS
Encrypted Client Hello", Work in Progress, Internet-Draft, Encrypted Client Hello", Work in Progress, Internet-Draft,
draft-ietf-tls-esni-10, 8 March 2021, draft-ietf-tls-esni-11, 14 June 2021,
<https://tools.ietf.org/html/draft-ietf-tls-esni-10>. <https://datatracker.ietf.org/doc/html/draft-ietf-tls-
esni-11>.
[TMA-QOF] Trammell, B., Gugelmann, D., and N. Brownlee, "Inline Data [TMA-QOF] Trammell, B., Gugelmann, D., and N. Brownlee, "Inline Data
Integrity Signals for Passive Measurement (in Proc. TMA Integrity Signals for Passive Measurement (in Proc. TMA
2014)", April 2014. 2014)", April 2014.
[WIRE-IMAGE] [WIRE-IMAGE]
Trammell, B. and M. Kuehlewind, "The Wire Image of a Trammell, B. and M. Kuehlewind, "The Wire Image of a
Network Protocol", RFC 8546, DOI 10.17487/RFC8546, April Network Protocol", RFC 8546, DOI 10.17487/RFC8546, April
2019, <https://www.rfc-editor.org/rfc/rfc8546>. 2019, <https://www.rfc-editor.org/rfc/rfc8546>.
Appendix A. Distinguishing IETF QUIC and Google QUIC Versions
This section contains algorithms that allows parsing versions from
both Google QUIC and IETF QUIC. These mechanisms will become
irrelevant when IETF QUIC is fully deployed and Google QUIC is
deprecated.
Note that other than this appendix, nothing in this document applies
to Google QUIC. And the purpose of this appendix is merely to
distinguish IETF QUIC from any versions of Google QUIC.
This appendix uses the following conventions: * array[i] - one byte
at index i of array * array[i:j] - subset of array starting with
index i (inclusive) up to j-1 (inclusive) * array[i:] - subset of
array starting with index i (inclusive) up to the end of the array
Conceptually, a Google QUIC version is an opaque 32bit field. When
we refer to a version with four printable characters, we use its
ASCII representation: for example, Q050 refers to {'Q', '0', '5',
'0'} which is equal to {0x51, 0x30, 0x35, 0x30}. Otherwise, we use
its hexadecimal representation: for example, 0xff00001d refers to
{0xff, 0x00, 0x00, 0x1d}.
QUIC versions that start with 'Q' or 'T' followed by three digits are
Google QUIC versions. Versions up to and including 43 are documented
by <https://docs.google.com/document/d/
1WJvyZflAO2pq77yOLbp9NsGjC1CHetAXV8I0fQe-B_U/preview>. Versions
Q046, Q050, T050, and T051 are not fully documented, but this
appendix should contain enough information to allow parsing Client
Hellos for those versions.
To extract the version number itself, one needs to look at the first
byte of the QUIC packet, in other words the first byte of the UDP
payload.
first_byte = packet[0]
first_byte_bit1 = ((first_byte & 0x80) != 0)
first_byte_bit2 = ((first_byte & 0x40) != 0)
first_byte_bit3 = ((first_byte & 0x20) != 0)
first_byte_bit4 = ((first_byte & 0x10) != 0)
first_byte_bit5 = ((first_byte & 0x08) != 0)
first_byte_bit6 = ((first_byte & 0x04) != 0)
first_byte_bit7 = ((first_byte & 0x02) != 0)
first_byte_bit8 = ((first_byte & 0x01) != 0)
if (first_byte_bit1) {
version = packet[1:5]
} else if (first_byte_bit5 && !first_byte_bit2) {
if (!first_byte_bit8) {
abort("Packet without version")
}
if (first_byte_bit5) {
version = packet[9:13]
} else {
version = packet[5:9]
}
} else {
abort("Packet without version")
}
A.1. Extracting the CRYPTO frame
counter = 0
while (payload[counter] == 0) {
counter += 1
}
first_nonzero_payload_byte = payload[counter]
fnz_payload_byte_bit3 = ((first_nonzero_payload_byte & 0x20) != 0)
if (first_nonzero_payload_byte != 0x06) {
abort("Unexpected frame")
}
if (payload[counter+1] != 0x00) {
abort("Unexpected crypto stream offset")
}
counter += 2
if ((payload[counter] & 0xc0) == 0) {
crypto_data_length = payload[counter]
counter += 1
} else {
crypto_data_length = payload[counter:counter+2]
counter += 2
}
crypto_data = payload[counter:counter+crypto_data_length]
ParseTLS(crypto_data)
Authors' Addresses Authors' Addresses
Mirja Kuehlewind Mirja Kuehlewind
Ericsson Ericsson
Email: mirja.kuehlewind@ericsson.com Email: mirja.kuehlewind@ericsson.com
Brian Trammell Brian Trammell
Google Switzerland GmbH Google Switzerland GmbH
Gustav-Gull-Platz 1 Gustav-Gull-Platz 1
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