Manageability of the QUIC Transport Protocol
draft-ietf-quic-manageability-10
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 9312.
|
|
|---|---|---|---|
| Authors | Mirja Kühlewind , Brian Trammell | ||
| Last updated | 2021-02-22 (Latest revision 2021-01-22) | ||
| Replaces | draft-kuehlewind-quic-manageability | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
GENART Last Call review
(of
-14)
by Elwyn Davies
Ready w/nits
|
||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | In WG Last Call | |
| Document shepherd | (None) | ||
| IESG | IESG state | Became RFC 9312 (Informational) | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-quic-manageability-10
Network Working Group M. Kuehlewind
Internet-Draft Ericsson
Intended status: Informational B. Trammell
Expires: 26 August 2021 Google
22 February 2021
Manageability of the QUIC Transport Protocol
draft-ietf-quic-manageability-10
Abstract
This document discusses manageability of the QUIC transport protocol,
focusing on caveats impacting network operations involving QUIC
traffic. Its intended audience is network operators, as well as
content providers that rely on the use of QUIC-aware middleboxes,
e.g. for load balancing.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 26 August 2021.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Simplified BSD License text
as described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License.
Kuehlewind & Trammell Expires 26 August 2021 [Page 1]
Internet-Draft QUIC Manageability February 2021
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Features of the QUIC Wire Image . . . . . . . . . . . . . . . 4
2.1. QUIC Packet Header Structure . . . . . . . . . . . . . . 4
2.2. Coalesced Packets . . . . . . . . . . . . . . . . . . . . 6
2.3. Use of Port Numbers . . . . . . . . . . . . . . . . . . . 6
2.4. The QUIC Handshake . . . . . . . . . . . . . . . . . . . 7
2.5. Integrity Protection of the Wire Image . . . . . . . . . 11
2.6. Connection ID and Rebinding . . . . . . . . . . . . . . . 11
2.7. Packet Numbers . . . . . . . . . . . . . . . . . . . . . 12
2.8. Version Negotiation and Greasing . . . . . . . . . . . . 12
3. Network-visible Information about QUIC Flows . . . . . . . . 13
3.1. Identifying QUIC Traffic . . . . . . . . . . . . . . . . 13
3.1.1. Identifying Negotiated Version . . . . . . . . . . . 13
3.1.2. Rejection of Garbage Traffic . . . . . . . . . . . . 14
3.2. Connection Confirmation . . . . . . . . . . . . . . . . . 14
3.3. Distinguishing Acknowledgment traffic . . . . . . . . . . 15
3.4. Application Identification . . . . . . . . . . . . . . . 15
3.4.1. Extracting Server Name Indication (SNI)
Information . . . . . . . . . . . . . . . . . . . . . 15
3.5. Flow Association . . . . . . . . . . . . . . . . . . . . 17
3.6. Flow teardown . . . . . . . . . . . . . . . . . . . . . . 17
3.7. Flow Symmetry Measurement . . . . . . . . . . . . . . . . 17
3.8. Round-Trip Time (RTT) Measurement . . . . . . . . . . . . 17
3.8.1. Measuring Initial RTT . . . . . . . . . . . . . . . . 18
3.8.2. Using the Spin Bit for Passive RTT Measurement . . . 18
4. Specific Network Management Tasks . . . . . . . . . . . . . . 20
4.1. Stateful Treatment of QUIC Traffic . . . . . . . . . . . 20
4.2. Passive Network Performance Measurement and
Troubleshooting . . . . . . . . . . . . . . . . . . . . . 21
4.3. Server Cooperation with Load Balancers . . . . . . . . . 21
4.4. DDoS Detection and Mitigation . . . . . . . . . . . . . . 21
4.5. UDP Policing . . . . . . . . . . . . . . . . . . . . . . 22
4.6. Handling ICMP Messages . . . . . . . . . . . . . . . . . 22
4.7. Quality of Service handling and ECMP . . . . . . . . . . 23
4.8. QUIC and Network Address Translation (NAT) . . . . . . . 23
4.8.1. Resource Conservation . . . . . . . . . . . . . . . . 24
4.8.2. "Helping" with routing infrastructure issues . . . . 25
4.9. Filtering behavior . . . . . . . . . . . . . . . . . . . 26
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
6. Security Considerations . . . . . . . . . . . . . . . . . . . 26
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 26
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 27
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
9.1. Normative References . . . . . . . . . . . . . . . . . . 27
9.2. Informative References . . . . . . . . . . . . . . . . . 27
Appendix A. Appendix . . . . . . . . . . . . . . . . . . . . . . 30
Kuehlewind & Trammell Expires 26 August 2021 [Page 2]
Internet-Draft QUIC Manageability February 2021
A.1. Distinguishing IETF QUIC and Google QUIC Versions . . . . 30
A.2. Extracting the CRYPTO frame . . . . . . . . . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32
1. Introduction
QUIC [QUIC-TRANSPORT] is a new transport protocol that is
encapsulated in UDP. QUIC integrates TLS [QUIC-TLS] to encrypt all
payload data and most control information. QUIC version 1 was
designed primarily as a transport for HTTP, with the resulting
protocol being known as HTTP/3 [QUIC-HTTP].
Given that QUIC is an end-to-end transport protocol, all information
in the protocol header, even that which can be inspected, is not
meant to be mutable by the network, and is therefore integrity-
protected. While less information is visible to the network than for
TCP, integrity protection can also simplify troubleshooting, because
none of the nodes on the network path can modify the transport layer
information.
This document provides guidance for network operations that manage
QUIC traffic. This includes guidance on how to interpret and utilize
information that is exposed by QUIC to the network, requirements and
assumptions that the QUIC design with respect to network treatment,
and a description of how common network management practices will be
impacted by QUIC.
Since QUIC's wire image [WIRE-IMAGE] is integrity-protected, in-
network operations that depend on modification of data are not
possible without the cooperation of an endpoint. Network operation
practices that alter data are only possible if performed as a QUIC
endpoint; this might be possible with the introduction of a proxy
which authenticates as an endpoint. Proxy operations are not in
scope for this document.
Network management is not a one-size-fits-all endeavour: practices
considered necessary or even mandatory within enterprise networks
with certain compliance requirements, for example, would be
impermissible on other networks without those requirements. This
document therefore does not make any specific recommendations as to
which practices should or should not be applied; for each practice,
it describes what is and is not possible with the QUIC transport
protocol as defined.
Kuehlewind & Trammell Expires 26 August 2021 [Page 3]
Internet-Draft QUIC Manageability February 2021
2. Features of the QUIC Wire Image
In this section, we discuss those aspects of the QUIC transport
protocol that have an impact on the design and operation of devices
that forward QUIC packets. Here, we are concerned primarily with the
unencrypted part of QUIC's wire image [WIRE-IMAGE], which we define
as the information available in the packet header in each QUIC
packet, and the dynamics of that information. Since QUIC is a
versioned protocol, the wire image of the header format can also
change from version to version. However, the field that identifies
the QUIC version in some packets, and the format of the Version
Negotiation Packet, are both inspectable and invariant
[QUIC-INVARIANTS].
This document describes version 1 of the QUIC protocol, whose wire
image is fully defined in [QUIC-TRANSPORT] and [QUIC-TLS]. Features
of the wire image described herein may change in future versions of
the protocol, except when specified as an invariant
[QUIC-INVARIANTS], and cannot be used to identify QUIC as a protocol
or to infer the behavior of future versions of QUIC.
Appendix A.1 provides non-normative guidance on the identification of
QUIC version 1 packets compared to some pre-standard versions.
2.1. QUIC Packet Header Structure
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
which type of header is present. The purpose of this bit is
invariant across QUIC versions.
The long header exposes more information. It is used during
connection establishment, including version negotiation, retry, and
0-RTT data. It contains a version number, as well as source and
destination connection IDs for grouping packets belonging to the same
flow. The definition and location of these fields in the QUIC long
header are invariant for future versions of QUIC, although future
versions of QUIC may provide additional fields in the long header
[QUIC-INVARIANTS].
Short headers are used after connection establishment, and contain
only an optional destination connection ID and the spin bit for RTT
measurement.
The following information is exposed in QUIC packet headers:
Kuehlewind & Trammell Expires 26 August 2021 [Page 4]
Internet-Draft QUIC Manageability February 2021
* "fixed bit": the second most significant bit of the first octet
most QUIC packets of the current version is currently set to 1,
for endpoints to demultiplex with other UDP-encapsulated
protocols. Even thought this bit is fixed in the QUICv1
specification, endpoints may use a version or extension that
varies the bit. Therefore, observers cannot depend on it as an
identifier for QUIC.
* latency spin bit: the third most significant bit of first octet in
the short packet header. The spin bit is set by endpoints such
that tracking edge transitions can be used to passively observe
end-to-end RTT. See Section 3.8.2 for further details.
* header type: the long header has a 2 bit packet type field
following the Header Form and fixed bits. Header types correspond
to stages of the handshake; see Section 17.2 of [QUIC-TRANSPORT]
for details.
* version number: the version number is present in the long header,
and identifies the version used for that packet. During Version
Negotiation (see Section 2.8 and Section 17.2.1 of
[QUIC-TRANSPORT]), the version number field has a special value
(0x00000000) that identifies the packet as a Version Negotiation
packet. Upon time of publishing of this document, QUIC versions
that start with 0xff implement IETF drafts. QUIC version 1 uses
version 0x00000001. Operators should expect to observe packets
with other version numbers as a result of various Internet
experiments and future standards.
* source and destination connection ID: short and long packet
headers carry a destination connection ID, a variable-length field
that can be used to identify the connection associated with a QUIC
packet, for load-balancing and NAT rebinding purposes; see
Section 4.3 and Section 2.6. Long packet headers additionally
carry a source connection ID. The source connection ID
corresponds to the destination connection ID the source would like
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
is also present; on short header packets, the length of the
destination connection ID is implicit.
* length: the length of the remaining QUIC packet after the length
field, present on long headers. This field is used to implement
coalesced packets during the handshake (see Section 2.2).
* token: Initial packets may contain a token, a variable-length
opaque value optionally sent from client to server, used for
validating the client's address. Retry packets also contain a
Kuehlewind & Trammell Expires 26 August 2021 [Page 5]
Internet-Draft QUIC Manageability February 2021
token, which can be used by the client in an Initial packet on a
subsequent connection attempt. The length of the token is
explicit in both cases.
Retry (Section 17.2.5 of [QUIC-TRANSPORT]) and Version Negotiation
(Section 17.2.1 of [QUIC-TRANSPORT]) packets are not encrypted or
obfuscated in any way. For other kinds of packets, other information
in the packet headers is cryptographically obfuscated:
* packet number: All packets except Version Negotiation and Retry
packets have an associated packet number; however, this packet
number is encrypted, and therefore not of use to on-path
observers. The offset of the packet number is encoded in long
headers, while it is implicit (depending on destination connection
ID length) in short headers. The length of the packet number is
cryptographically obfuscated.
* key phase: The Key Phase bit, present in short headers, specifies
the keys used to encrypt the packet to support key rotation. The
Key Phase bit is cryptographically obfuscated.
2.2. Coalesced Packets
Multiple QUIC packets may be coalesced into a UDP datagram, with a
datagram carrying one or more long header packets followed by zero or
one short header packets. When packets are coalesced, the Length
fields in the long headers are used to separate QUIC packets; see
Section 12.2 of [QUIC-TRANSPORT]. The length header field is
variable length, and its position in the header is also variable
depending on the length of the source and destination connection ID;
see Section 17.2 of [QUIC-TRANSPORT].
2.3. Use of Port Numbers
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
other IETF transports [RFC7605], there is no guarantee that a
specific application will use a given registered port, or that a
given port carries traffic belonging to the respective registered
service, especially when application layer information is encrypted.
For example, [QUIC-HTTP] specifies the use of Alt-Svc for discovery
of HTTP/3 services on other ports.
Further, as QUIC has a connection ID, it is also possible to maintain
multiple QUIC connections over one 5-tuple. However, if the
connection ID is not present in the packet header, all packets of the
5-tuple belong to the same QUIC connection.
Kuehlewind & Trammell Expires 26 August 2021 [Page 6]
Internet-Draft QUIC Manageability February 2021
2.4. The QUIC Handshake
New QUIC connections are established using a handshake, which is
distinguishable on the wire and contains some information that can be
passively observed.
To illustrate the information visible in the QUIC wire image during
the handshake, we first show the general communication pattern
visible in the UDP datagrams containing the QUIC handshake, then
examine each of the datagrams in detail.
The QUIC handshake can normally be recognized on the wire through at
least four datagrams we'll call "QUIC Client Hello", "QUIC Server
Hello", and "Initial Completion", and "Handshake Completion", for
purposes of this illustration, as shown in Figure 1.
Packets in the handshake belong to three separate cryptographic and
transport contexts ("Initial", which contains observable payload, and
"Handshake" and "1-RTT", which do not). QUIC packets in separate
contexts during the handshake are generally coalesced (see
Section 2.2) in order to reduce the number of UDP datagrams sent
during the handshake.
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
has sent its Server Hello.
Client Server
| |
+----QUIC Client Hello-------------------->|
+----(zero or more 0RTT)------------------>|
| |
|<--------------------QUIC Server Hello----+
|<---------(1RTT encrypted data starts)----+
| |
+----Initial Completion------------------->|
+----(1RTT encrypted data starts)--------->|
| |
|<-----------------Handshake Completion----+
| |
Figure 1: General communication pattern visible in the QUIC handshake
Kuehlewind & Trammell Expires 26 August 2021 [Page 7]
Internet-Draft QUIC Manageability February 2021
A typical handshake starts with the client sending of a QUIC Client
Hello datagram as shown in Figure 2, which elicits a QUIC Server
Hello datagram as shown in Figure 3 typically containing three
packets: an Initial packet with the Server Hello, a Handshake packet
with the rest of the server's side of the TLS handshake, and initial
1-RTT data, if present.
The Initial Completion datagram contains at least one Handshake
packet and some also include an Initial packet.
Datagrams that contain a QUIC Initial Packet (Client Hello, Server
Hello, and some Initial Completion) contain at least 1200 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 QUIC Initial packets are encrypted using Initial
Secrets, which are derived from a per-version constant and the
client's destination connection ID; they are therefore observable by
any on-path device that knows the per-version constant. They are
therefore considered 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 the Short Header packets transmitted after
the handshake belong to cryptographic and transport contexts. The
Initial Completion Figure 4 and the Handshake Completion Figure 5
datagrams finish these first two contexts, by sending the final
acknowledgment and finishing the transmission of CRYPTO frames.
+----------------------------------------------------------+
| UDP header (source and destination UDP ports) |
+----------------------------------------------------------+
| QUIC long header (type = Initial, Version, DCID, SCID) (Length)
+----------------------------------------------------------+ |
| QUIC CRYPTO frame header | |
+----------------------------------------------------------+ |
| TLS Client Hello (incl. TLS SNI) | |
+----------------------------------------------------------+ |
| QUIC PADDING frames | |
+----------------------------------------------------------+<-+
Figure 2: Typical QUIC Client Hello datagram pattern with no 0-RTT
Kuehlewind & Trammell Expires 26 August 2021 [Page 8]
Internet-Draft QUIC Manageability February 2021
The Client Hello datagram exposes version number, source and
destination connection IDs without encryption. Information in the
TLS Client Hello frame, including any TLS Server Name Indication
(SNI) present, is obfuscated using the Initial secret. Note that the
location of PADDING is implementation-dependent, and PADDING frames
may not appear in a coalesced Initial packet.
+------------------------------------------------------------+
| UDP header (source and destination UDP ports) |
+------------------------------------------------------------+
| QUIC long header (type = Initial, Version, DCID, SCID) (Length)
+------------------------------------------------------------+ |
| QUIC CRYPTO frame header | |
+------------------------------------------------------------+ |
| TLS Server Hello | |
+------------------------------------------------------------+ |
| QUIC ACK frame (acknowledging client hello) | |
+------------------------------------------------------------+<-+
| QUIC long header (type = Handshake, Version, DCID, SCID) (Length)
+------------------------------------------------------------+ |
| encrypted payload (presumably CRYPTO frames) | |
+------------------------------------------------------------+<-+
| QUIC short header |
+------------------------------------------------------------+
| 1-RTT encrypted payload |
+------------------------------------------------------------+
Figure 3: Typical QUIC Server Hello datagram pattern
The Server Hello datagram also exposes version number, source and
destination connection IDs and information in the TLS Server Hello
message which is obfuscated using the Initial secret.
+------------------------------------------------------------+
| UDP header (source and destination UDP ports) |
+------------------------------------------------------------+
| QUIC long header (type = Initial, Version, DCID, SCID) (Length)
+------------------------------------------------------------+ |
| QUIC ACK frame (acknowledging Server Hello Initial) | |
+------------------------------------------------------------+<-+
| QUIC long header (type = Handshake, Version, DCID, SCID) (Length)
+------------------------------------------------------------+ |
| encrypted payload (presumably CRYPTO/ACK frames) | |
+------------------------------------------------------------+<-+
| QUIC short header |
+------------------------------------------------------------+
| 1-RTT encrypted payload |
+------------------------------------------------------------+
Kuehlewind & Trammell Expires 26 August 2021 [Page 9]
Internet-Draft QUIC Manageability February 2021
Figure 4: Typical QUIC Initial Completion datagram pattern
The Initial Completion datagram does not expose any additional
information; however, recognizing it can be used to determine that a
handshake has completed (see Section 3.2), and for three-way
handshake RTT estimation as in Section 3.8.
+------------------------------------------------------------+
| UDP header (source and destination UDP ports) |
+------------------------------------------------------------+
| QUIC long header (type = Handshake, Version, DCID, SCID) (Length)
+------------------------------------------------------------+ |
| encrypted payload (presumably ACK frame) | |
+------------------------------------------------------------+<-+
| QUIC short header |
+------------------------------------------------------------+
| 1-RTT encrypted payload |
+------------------------------------------------------------+
Figure 5: Typical QUIC Handshake Completion datagram pattern
Similar to Initial Completion, Handshake Completion also exposes no
additional information; observing it serves only to determine that
the handshake has completed.
When the client uses 0-RTT connection resumption, 0-RTT data may also
be seen in the QUIC Client Hello datagram, as shown in Figure 6.
+----------------------------------------------------------+
| UDP header (source and destination UDP ports) |
+----------------------------------------------------------+
| QUIC long header (type = Initial, Version, DCID, SCID) (Length)
+----------------------------------------------------------+ |
| QUIC CRYPTO frame header | |
+----------------------------------------------------------+ |
| TLS Client Hello (incl. TLS SNI) | |
+----------------------------------------------------------+<-+
| QUIC long header (type = 0RTT, Version, DCID, SCID) (Length)
+----------------------------------------------------------+ |
| 0-rtt encrypted payload | |
+----------------------------------------------------------+<-+
Figure 6: Typical 0-RTT QUIC Client Hello datagram pattern
In a 0-RTT QUIC Client Hello datagram, the PADDING frame is only
present if necessary to increase the size of the datagram with 0RTT
data to at least 1200 bytes. Additional datagrams containing only
0-RTT protected long header packets may be sent from the client to
Kuehlewind & Trammell Expires 26 August 2021 [Page 10]
Internet-Draft QUIC Manageability February 2021
the server after the Client Hello datagram, containing the rest of
the 0-RTT data. The amount of 0-RTT protected data that can be sent
in the first round is limited by the initial congestion window,
typically around 10 packets (see Section 7.2 of [QUIC-RECOVERY]).
2.5. Integrity Protection of the Wire Image
As soon as the cryptographic context is established, all information
in the QUIC header, including exposed information, is integrity
protected. Further, information that was sent and exposed in
handshake packets sent before the cryptographic context was
established are validated later during the cryptographic handshake.
Therefore, devices on path cannot alter any information or bits in
QUIC packets. Such alterations would cause the integrity check to
fail, which results in the receiver discarding the packet. Some
parts of Initial packets could be altered by removing and re-applying
the authenticated encryption without immediate discard at the
receiver. However, the cryptographic handshake validates most fields
and any modifications in those fields will result in connection
establishment failing later on.
2.6. Connection ID and Rebinding
The connection ID in the QUIC packet headers allows routing of QUIC
packets at load balancers on other than five-tuple information,
ensuring that related flows are appropriately balanced together; and
to allow rebinding of a connection after one of the endpoint's
addresses changes - usually the client's. Client and server
negotiate connection IDs during the handshake; typically, however,
only the server will request a connection ID for the lifetime of the
connection. Connection IDs for either endpoint may change during the
lifetime of a connection, with the new connection ID being negotiated
via encrypted frames. See Section 5.1 of [QUIC-TRANSPORT].
Therefore, observing a new connection ID does not necessary indicate
a new connection.
Server-generated connection IDs should seek to obscure any encoding,
of routing identities or any other information. Exposing the server
mapping would allow linkage of multiple IP addresses to the same host
if the server also supports migration. Furthermore, this opens an
attack vector on specific servers or pools.
The best way to obscure an encoding is to appear random to observers,
which is most rigorously achieved with encryption. Even when
encrypted, a scheme could embed the unencrypted length of the
connection ID in the connection ID itself, instead of remembering it.
Kuehlewind & Trammell Expires 26 August 2021 [Page 11]
Internet-Draft QUIC Manageability February 2021
[QUIC_LB] further specified possible algorithms to generate
connection IDs at load balancers.
2.7. Packet Numbers
The packet number field is always present in the QUIC packet header;
however, it is always encrypted. The encryption key for packet
number protection on handshake packets sent before cryptographic
context establishment is specific to the QUIC version, while packet
number protection on subsequent packets uses secrets derived from the
end-to-end cryptographic context. Packet numbers are therefore not
part of the wire image that is visible to on-path observers.
2.8. Version Negotiation and Greasing
Version Negotiation packets are used by the server to indicate that a
requested version from the client is not supported (see section 6 of
[QUIC-TRANSPORT]. Version Negotiation packets are not intrinsically
protected, but QUIC versions can use later encrypted messages to
verify that they were authentic. Therefore any modification of this
list will be detected and may cause the endpoints to terminate the
connection attempt.
Also note that the list of versions in the Version Negotiation packet
may contain reserved versions. This mechanism is used to avoid
ossification in the implementation on the selection mechanism.
Further, a client may send a Initial Client packet with a reserved
version number to trigger version negotiation. In the Version
Negotiation packet the connection ID and packet number of the Client
Initial packet are reflected to provide a proof of return-
routability. Therefore changing this information will also cause the
connection to fail.
QUIC is expected to evolve rapidly, so new versions, both
experimental and IETF standard versions, will be deployed in the
Internet more often than with traditional Internet- and transport-
layer protocols. Using a particular version number to recognize
valid QUIC traffic is likely to persistently miss a fraction of QUIC
flows and completely fail in the near future, and is therefore not
recommended. In addition, due to the speed of evolution of the
protocol, devices that attempt to distinguish QUIC traffic from non-
QUIC traffic for purposes of network admission control should admit
all QUIC traffic regardless of version.
Kuehlewind & Trammell Expires 26 August 2021 [Page 12]
Internet-Draft QUIC Manageability February 2021
3. Network-visible Information about QUIC Flows
This section addresses the different kinds of observations and
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
bidirectional observer (one that can see packets in both directions
in the sequence in which they are carried on the wire) unless noted.
3.1. Identifying QUIC Traffic
The QUIC wire image is not specifically designed to be
distinguishable from other UDP traffic.
The only application binding defined by the IETF QUIC WG is HTTP/3
[QUIC-HTTP] at the time of this writing; however, many other
applications are currently being defined and deployed over QUIC, so
an assumption that all QUIC traffic is HTTP/3 is not valid. HTTP
over QUIC uses UDP port 443 by default, although URLs referring to
resources available over HTTP/3 may specify alternate port numbers.
Simple assumptions about whether a given flow is using QUIC based
upon a UDP port number may therefore not hold; see also [RFC7605]
section 5.
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
and section 17 of [QUIC-TRANSPORT]), this method of recognizing QUIC
traffic is not reliable. First, it only provides one bit of
information and is prone to collision with UDP-based protocols other
than those that this static bit is meant to allow multiplexing with.
Second, this feature of the wire image is not invariant
[QUIC-INVARIANTS] and may change in future versions of the protocol,
or even be negotiated during the handshake via the use of transport
parameters.
Even though transport parameters transmitted in the client initial
are obserable by the network, they cannot be modified by the network
without risking connection failure. Further, the negotiated reply
from the server cannot be observed, so observers on the network
cannot know which parameters are actually in use.
3.1.1. Identifying Negotiated Version
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
handshake: for QUIC version 1 if the version number in the Initial
packet from a client is the same as the version number in Initial
packet of the server response, that version has been accepted by both
endpoints to be used for the rest of the connection.
Kuehlewind & Trammell Expires 26 August 2021 [Page 13]
Internet-Draft QUIC Manageability February 2021
Negotiated version cannot be identified for flows for which a
handshake is not observed, such as in the case of connection
migration; however, it might be possible to associate a flow with a
flow for which a version has been identified; see Section 3.5.
This document focuses on QUIC Version 1, and this section applies
only to packets belonging to Version 1 QUIC flows; for purposes of
on-path observation, it assumes that these packets have been
identified as such through the observation of a version number
exchange as described above.
3.1.2. Rejection of Garbage Traffic
A related question is whether a first packet of a given flow on a
known QUIC-associated port is a valid QUIC packet, to support in-
network filtering of garbage UDP packets (reflection attacks, random
backscatter). While heuristics based on the first byte of the packet
(packet type) could be used to separate valid from invalid first
packet types, the deployment of such heuristics is not recommended,
as packet types may have different meanings in future versions of the
protocol.
3.2. Connection Confirmation
Connection establishment uses Initial and Handshake packets
containing a TLS handshake, and Retry packets that do not contain
parts of the handshake. Connection establishment can therefore be
detected using heuristics similar to those used to detect TLS over
TCP. A client initiating a 0-RTT connection may also send data
packets in 0-RTT Protected packets directly after the Initial packet
containing the TLS Client Hello. Since these packets may be
reordered in the network, 0-RTT Protected data packets could be seen
before the Initial packet.
Note that clients send Initial packets before servers do, servers
send Handshake packets before clients do, and only clients send
Initial packets with tokens. Therefore, the role as a client or
server can generally be confirmed by an on- path observer. An
attempted connection after Retry can be detected by correlating the
token on the Retry with the token on the subsequent Initial packet
and the destination connection ID of the new Initial packet.
Kuehlewind & Trammell Expires 26 August 2021 [Page 14]
Internet-Draft QUIC Manageability February 2021
3.3. Distinguishing Acknowledgment traffic
Some deployed in-network functions distinguish pure-acknowledgment
(ACK) packets from packets carrying upper-layer data in order to
attempt to enhance performance, for example by queueing ACKs
differently or manipulating ACK signaling. Distinguishing ACK
packets is trivial in TCP, but not supported by QUIC, since
acknowledgment signaling is carried inside QUIC's encrypted payload,
and ACK manipulation is impossible. Specifically, heuristics
attempting to distinguish ACK-only packets from payload-carrying
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
as those mechanisms can change, e.g., due to the use of extensions.
3.4. Application Identification
The cleartext TLS handshake may contain Server Name Indication (SNI)
[RFC6066], by which the client reveals the name of the server it
intends to connect to, in order to allow the server to present a
certificate based on that name. It may also contain information from
Application-Layer Protocol Negotiation (ALPN) [RFC7301], by which the
client exposes the names of application-layer protocols it supports;
an observer can deduce that one of those protocols will be used if
the connection continues.
Work is currently underway in the TLS working group to encrypt the
SNI in TLS 1.3 [TLS-ESNI]. This would make SNI-based application
identification impossible by on-path observation for QUIC and other
protocols that use TLS.
3.4.1. Extracting Server Name Indication (SNI) Information
If the SNI is not encrypted it can be derived from the QUIC Initial
packet by calculating the Initial Secret to decrypt the packet
payload and parse the QUIC CRYPTO Frame containing the TLS
ClientHello.
As both the initial salt for the Initial Secret as well as CRYPTO
frame itself are version-specific, the first step is always to parse
the version number (second to sixth byte of the long header). Note
that only long header packets carry the version number, so it is
necessary to also check the if first bit of the QUIC packet is set to
1, indicating a long header.
Kuehlewind & Trammell Expires 26 August 2021 [Page 15]
Internet-Draft QUIC Manageability February 2021
Note that proprietary QUIC versions, that have been deployed before
standardization, might not set the first bit in a QUIC long header
packets to 1. To parse these versions, example code is provided in
the appendix (see Appendix A.1), however, it is expected that these
versions will gradually disappear over time.
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
third and fourth bit of the header are both set to 0. Then the
client destination connection ID needs to be extracted to calculate
the Initial Secret together with the version specific initial salt,
as described in [QUIC-TLS]. The length of the connection ID is
indicated in the 6th byte of the header followed by the connection ID
itself.
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
token length need to be extracted. The packet number length is
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
[QUIC-TLS]. The source connection ID length is specified in the byte
after the destination connection ID. And the token length, which
follows the source connection ID, is a variable length integer as
specified in Section 16 of [QUIC-TRANSPORT].
After decryption, the Initial Client packet can be parsed to detect
the CRYPTO frame that contains the TLS Client Hello, which then can
be parsed similarly to TLS over TCP connections. The Initial client
packet may contain other frames, so the first bytes of each frame
need to be checked to identify the frame type, and if needed skip
over it. Note that the length of the frames is dependent on the
frame type. In QUIC version 1, the packet is expected to only carry
the CRYPTO frame and optionally padding frames. However, PADDING
frames, each consisting of a single zero byte, may also occur before
or after the CRYPTO frame.
Note that client Initial packets after the first do not always use
the destination connection ID that was used to generate the Initial
keys. Therefore, attempts to decrypt these packets using the
procedure above might fail.
Kuehlewind & Trammell Expires 26 August 2021 [Page 16]
Internet-Draft QUIC Manageability February 2021
3.5. Flow Association
The QUIC connection ID (see Section 2.6) is designed to allow an on-
path device such as a load-balancer to associate two flows as
identified by five-tuple when the address and port of one of the
endpoints changes; e.g. due to NAT rebinding or server IP address
migration. An observer keeping flow state can associate a connection
ID with a given flow, and can associate a known flow with a new flow
when when observing a packet sharing a connection ID and one endpoint
address (IP address and port) with the known flow.
However, since the connection ID may change multiple times during the
lifetime of a flow, and the negotiation of connection ID changes is
encrypted, packets with the same 5-tuple but different connection IDs
may or may not belong to the same connection.
The connection ID value should be treated as opaque; see Section 4.3
for caveats regarding connection ID selection at servers.
3.6. Flow teardown
QUIC does not expose the end of a connection; the only indication to
on-path devices that a flow has ended is that packets are no longer
observed. Stateful devices on path such as NATs and firewalls must
therefore use idle timeouts to determine when to drop state for QUIC
flows, see further section Section 4.1.
3.7. Flow Symmetry Measurement
QUIC explicitly exposes which side of a connection is a client and
which side is a server during the handshake. In addition, the
symmetry of a flow (whether primarily client-to-server, primarily
server-to-client, or roughly bidirectional, as input to basic traffic
classification techniques) can be inferred through the measurement of
data rate in each direction. While QUIC traffic is protected and
ACKs may be padded, padding is not required.
3.8. Round-Trip Time (RTT) Measurement
Round-trip time of QUIC flows can be inferred by observation once per
flow, during the handshake, as in passive TCP measurement; this
requires parsing of the QUIC packet header and recognition of the
handshake, as illustrated in Section 2.4. It can also be inferred
during the flow's lifetime, if the endpoints use the spin bit
facility described below and in [QUIC-TRANSPORT], section 17.3.1.
Kuehlewind & Trammell Expires 26 August 2021 [Page 17]
Internet-Draft QUIC Manageability February 2021
3.8.1. Measuring Initial RTT
In the common case, the delay between the Initial packet containing
the TLS Client Hello and the Handshake packet containing the TLS
Server Hello represents the RTT component on the path between the
observer and the server. The delay between the TLS Server Hello and
the Handshake packet containing the TLS Finished message sent by the
client represents the RTT component on the path between the observer
and the client. While the client may send 0-RTT Protected packets
after the Initial packet during 0-RTT connection re-establishment,
these can be ignored for RTT measurement purposes.
Handshake RTT can be measured by adding the client-to-observer and
observer-to-server RTT components together. This measurement
necessarily includes any transport and application layer delay (the
latter mainly caused by the asymmetric crypto operations associated
with the TLS handshake) at both sides.
3.8.2. Using the Spin Bit for Passive RTT Measurement
The spin bit provides a version-specific method to measure per-flow
RTT from observation points on the network path throughout the
duration of a connection. See section 17.4 of [QUIC-TRANSPORT] for
the definition of the spin bit in Version 1 of QUIC. Endpoint
participation in spin bit signaling is optional. That is, while its
location is fixed in this version of QUIC, an endpoint can
unilaterally choose to not support "spinning" the bit.
Use of the spin bit for RTT measurement by devices on path is only
possible when both endpoints enable it. Some endpoints may disable
use of the spin bit by default, others only in specific deployment
scenarios, e.g. for servers and clients where the RTT would reveal
the presence of a VPN or proxy. To avoid making these connections
identifiable based on the usage of the spin bit, all endpoints
randomly disable "spinning" for at least one eighth of connections,
even if otherwise enabled by default. An endpoint not participating
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
on each packet sent.
When in use and a QUIC flow sends data continuously, the latency spin
bit in each direction changes value once per round-trip time (RTT).
An on-path observer can observe the time difference between edges
(changes from 1 to 0 or 0 to 1) in the spin bit signal in a single
direction to measure one sample of end-to-end RTT. This mechanism
follows the principles of protocol measurability laid out in [IPIM].
Kuehlewind & Trammell Expires 26 August 2021 [Page 18]
Internet-Draft QUIC Manageability February 2021
Note that this measurement, as with passive RTT measurement for TCP,
includes any transport protocol delay (e.g., delayed sending of
acknowledgements) and/or application layer delay (e.g., waiting for a
response to be generated). It therefore provides devices on path a
good instantaneous estimate of the RTT as experienced by the
application.
However, application-limited and flow-control-limited senders can
have application and transport layer delay, respectively, that are
much greater than network RTT. When the sender is application-
limited and e.g. only sends small amount of periodic application
traffic, where that period is longer than the RTT, measuring the spin
bit provides information about the application period, not the
network RTT.
Since the spin bit logic at each endpoint considers only samples from
packets that advance the largest packet number, signal generation
itself is resistant to reordering. However, reordering can cause
problems at an observer by causing spurious edge detection and
therefore inaccurate (i.e., lower) RTT estimates, if reordering
occurs across a spin-bit flip in the stream.
Simple heuristics based on the observed data rate per flow or changes
in the RTT series can be used to reject bad RTT samples due to lost
or reordered edges in the spin signal, as well as application or flow
control limitation; for example, QoF [TMA-QOF] rejects component RTTs
significantly higher than RTTs over the history of the flow. These
heuristics may use the handshake RTT as an initial RTT estimate for a
given flow. Usually such heuristics would also detect if the spin is
either constant or randomly set for a connection.
An on-path observer that can see traffic in both directions (from
client to server and from server to client) can also use the spin bit
to measure "upstream" and "downstream" component RTT; i.e, the
component of the end-to-end RTT attributable to the paths between the
observer and the server and the observer and the client,
respectively. It does this by measuring the delay between a spin
edge observed in the upstream direction and that observed in the
downstream direction, and vice versa.
Kuehlewind & Trammell Expires 26 August 2021 [Page 19]
Internet-Draft QUIC Manageability February 2021
Raw RTT samples generated using these techniques can be processed in
various ways to generate useful network performance metrics. A
simple linear smoothing or moving minimum filter can be applied to
the stream of RTT samples to get a more stable estimate of
application-experienced RTT. RTT samples measured from the spin bit
can also be used to generate RTT distribution information, including
minimum RTT (which approximates network RTT over longer time windows)
and RTT variance (which approximates jitter as seen by the
application).
4. Specific Network Management Tasks
In this section, we review specific network management and
measurement techniques and how QUIC's design impacts them.
4.1. Stateful Treatment of QUIC Traffic
Stateful treatment of QUIC traffic (e.g., at a firewall or NAT
middlebox) is possible through QUIC traffic and version
identification (Section 3.1) and observation of the handshake for
connection confirmation (Section 3.2). The lack of any visible end-
of-flow signal (Section 3.6) means that this state must be purged
either through timers or through least-recently-used eviction,
depending on application requirements.
[RFC4787] requires a timeout that is not less than 2 minutes for most
UDP traffic. However, in pratice, timers are often lower, in the
range of 15 to 30 seconds. In contrast, [RFC5382] recommends a
timeout of more than 2 hours for TCP, given that TCP is a connection-
oriented protocol with well-defined closure semantics. For network
devices that are QUIC-aware, it is recommended to also use longer
timeouts for QUIC traffic, as QUIC is connection-oriented. As such,
a handshake packet from the server indicates the willingness of the
server to communicate with the client.
The QUIC header optionally contains a connection ID which can be used
as additional entropy beyond the 5-tuple, if needed. The QUIC
handshake needs to be observed in order to understand whether the
connection ID is present and what length it has. However, connection
IDs may be renegotiated during after the handshake, and this
renegotiation is not visible to the path. Using the connection ID as
a flow key field for stateful treatment of flows may therefore cause
undetectable and unrecoverable loss of state in the middle of a
connection. Use of connection IDs is specifically discouraged for
NAT applications.
Kuehlewind & Trammell Expires 26 August 2021 [Page 20]
Internet-Draft QUIC Manageability February 2021
4.2. Passive Network Performance Measurement and Troubleshooting
Limited RTT measurement is possible by passive observation of QUIC
traffic; see Section 3.8. No passive measurement of loss is possible
with the present wire image. Extremely limited observation of
upstream congestion may be possible via the observation of CE
markings on ECN-enabled QUIC traffic.
4.3. Server Cooperation with Load Balancers
In the case of content distribution networking architectures
including load balancers, the connection ID provides a way for the
server to signal information about the desired treatment of a flow to
the load balancers. Guidance on assigning connection IDs is given in
[QUIC-APPLICABILITY].
4.4. DDoS Detection and Mitigation
Current practices in detection and mitigation of Distributed Denial
of Service (DDoS) attacks generally involve classification of
incoming traffic (as packets, flows, or some other aggregate) into
"good" (productive) and "bad" (DDoS) traffic, and then differential
treatment of this traffic to forward only good traffic. This
operation is often done in a separate specialized mitigation
environment through which all traffic is filtered; a generalized
architecture for separation of concerns in mitigation is given in
[DOTS-ARCH].
Key to successful DDoS mitigation is efficient classification of this
traffic in the mitigation environment. Limited first-packet garbage
detection as in Section 3.1.2 and stateful tracking of QUIC traffic
as in Section 4.1 above may be useful during classification.
Note that the use of a connection ID to support connection migration
renders 5-tuple based filtering insufficient and requires more state
to be maintained by DDoS defense systems. For the common case of NAT
rebinding, DDoS defense systems can detect a change in the client's
endpoint address by linking flows based on the server's connection
IDs. QUIC's linkability resistance ensures that a deliberate
connection migration is accompanied by a change in the connection ID.
Kuehlewind & Trammell Expires 26 August 2021 [Page 21]
Internet-Draft QUIC Manageability February 2021
It is questionable whether connection migrations must be supported
during a DDoS attack. If the connection migration is not visible to
the network that performs the DDoS detection, an active, migrated
QUIC connection may be blocked by such a system under attack. As
soon as the connection blocking is detected by the client, the client
may rely on the fast resumption mechanism provided by QUIC. When
clients migrate to a new path, they should be prepared for the
migration to fail and attempt to reconnect quickly.
TCP syncookies [RFC4937] are a well-established method of mitigating
some kinds of TCP DDoS attacks. QUIC Retry packets are the
functional analogue to syncookies, forcing clients to prove
possession of their IP address before committing server state.
However, there are safeguards in QUIC against unsolicited injection
of these packets by intermediaries who do not have consent of the end
server. See [QUIC_LB] for standard ways for intermediaries to send
Retry packets on behalf of consenting servers.
4.5. UDP Policing
Today, UDP is the most prevalent DDoS vector, since it is easy for
compromised non-admin applications to send a flood of large UDP
packets (while with TCP the attacker gets throttled by the congestion
controller) or to craft reflection and amplification attacks.
Networks should therefore be prepared for UDP flood attacks on ports
used for QUIC traffic. One possible response to this threat is to
police UDP traffic on the network, allocating a fixed portion of the
network capacity to UDP and blocking UDP datagram over that cap.
The recommended way to police QUIC packets is to either drop them all
or to throttle them based on the hash of the UDP datagram's source
and destination addresses, blocking a portion of the hash space that
corresponds to the fraction of UDP traffic one wishes to drop. When
the handshake is blocked, QUIC-capable applications may failover to
TCP (at least applications using well-known UDP ports). However,
blindly blocking a significant fraction of QUIC packets will allow
many QUIC handshakes to complete, preventing a TCP failover, but the
connections will suffer from severe packet loss.
4.6. Handling ICMP Messages
Datagram Packetization Layer PMTU Discovery (PLPMTUD) can be used by
QUIC to probe for the supported PMTU. PLPMTUD optionally uses ICMP
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
designed to safely use but not rely on receiving ICMP feedback (see
Section 14.2.1. of [QUIC-TRANSPORT]).
Kuehlewind & Trammell Expires 26 August 2021 [Page 22]
Internet-Draft QUIC Manageability February 2021
Networks are recommended to forward these ICMP messages and retain as
much of the original packet as possible without exceeding the minimum
MTU for the IP version when generating ICMP messages as recommended
in [RFC1812] and [RFC4443].
4.7. Quality of Service handling and ECMP
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
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
connection get uniform treatment. Using ECMP to distribute packets
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
more tolerant of packet re-ordering than traditional TCP traffic (see
Section 2.7). However, it cannot be known by the network which exact
recovery mechanism is used and therefore reordering tolerance should
be considered as unknown.
4.8. QUIC and Network Address Translation (NAT)
QUIC Connection IDs are opaque byte fields that are expressed
consistently across all QUIC versions [QUIC-INVARIANTS], see
Section 2.6. This feature may appear to present opportunities to
optimize NAT port usage and simplify the work of the QUIC server. In
fact, NAT behavior that relies on CID may instead cause connection
failure when endpoints change Connection ID, and disable important
protocol security features. NATs should retain their existing 4-
tuple-based operation and refrain from parsing or otherwise using
QUIC connection IDs.
This section uses the colloquial term NAT to mean NAPT (section 2.2
of [RFC3022]), which overloads several IP addresses to one IP address
or to an IP address pool, as commonly deployed in carrier-grade NATs
or residential NATs.
The remainder of this section explains how QUIC supports NATs better
than other connection-oriented protocols, why NAT use of Connection
ID might appear attractive, and how NAT use of CID can create serious
problems for the endpoints.
Kuehlewind & Trammell Expires 26 August 2021 [Page 23]
Internet-Draft QUIC Manageability February 2021
[RFC4787] contains some guidance on building NATs to interact
constructively with a wide range of applications. This section
extends the discussion to QUIC.
By using the CID, QUIC connections can survive NAT rebindings as long
as no routing function in the path is dependent on client IP address
and port to deliver packets between server and NAT. Reducing the
timeout on UDP NATs might be tempting in light of this property, but
not all QUIC server deployments will be robust to rebinding.
4.8.1. Resource Conservation
NATs sometimes hit an operational limit where they exhaust available
public IP addresses and ports, and must evict flows from their
address/port mapping. CIDs might appear to offer a way to multiplex
many connections over a single address and port.
However, QUIC endpoints may negotiate new connection IDs inside
cryptographically protected packets, and begin using them at will.
Imagine two clients behind a NAT that are sharing the same public IP
address and port. The NAT is differentiating them using the incoming
Connection ID. If one client secretly changes its connection ID,
there will be no mapping for the NAT, and the connection will
suddenly break.
QUIC is deliberately designed to fail rather than persist when the
network cannot support its operation. For HTTP/3, this extends to
recommending a fallback to TCP-based versions of HTTP rather than
persisting with a QUIC connection that might be unstable. And
[QUIC-APPLICABILITY] recommends TCP fallback for other protocols on
the basis that this is preferable to sudden connection errors and
time outs. Furthermore, wide deployment of NATs with this behavior
hinders the use of QUIC's migration function, which relies on the
ability to change the connection ID any time during the lifetime of a
QUIC connection.
It is possible, in principle, to encode the client's identity in a
connection ID using the techniques described in [QUIC_LB] and
explicit coordination with the NAT. However, this implies that the
client shares configuration with the NAT, which might be logistically
difficult. This adds administrative overhead while not resolving the
case where a client migrates to a point behind the NAT.
Note that multiplexing connection IDs over a single port anyway
violates the best common practice to avoid "port overloading" as
described in [RFC4787].
Kuehlewind & Trammell Expires 26 August 2021 [Page 24]
Internet-Draft QUIC Manageability February 2021
4.8.2. "Helping" with routing infrastructure issues
Concealing client address changes in order to simplify operational
routing issues will mask important signals that drive security
mechanisms, and therefore opens QUIC up to various attacks.
One challenge in QUIC deployments that want to benefit from QUIC's
migration capability is server infrastructures with routers and
switches that direct traffic based on address-port 4-tuple rather
than connection ID. The use of source IP address means that a NAT
rebinding or address migration will deliver packets to the wrong
server. As all QUIC payloads are encrypted, routers and switches
will not have access to negotiated but not-yet-in-use CIDs. This is
a particular problem for low-state load balancers. [QUIC_LB]
addresses this problem proposing a QUIC extension to allow some
server-load balancer coordination for routable CIDs.
It seems that a NAT anywhere in the front of such an infrastructure
setup could save the effort of converting all these devices by
decoding routable connection IDs and rewriting the packet IP
addresses to allow consistent routing by legacy devices.
Unfortunately, the change of IP address or port is an important
signal to QUIC endpoints. It requires a review of path-dependent
variables like congestion control parameters. It can also signify
various attacks that mislead one endpoint about the best peer address
for the connection (see section 9 of [QUIC-TRANSPORT]). The QUIC
PATH_CHALLENGE and PATH_RESPONSE frames are intended to detect and
mitigate these attacks and verify connectivity to the new address.
This mechanism cannot work if the NAT is bleaching peer address
changes.
For example, an attacker might copy a legitimate QUIC packet and
change the source address to match its own. In the absence of a
bleaching NAT, the receiving endpoint would interpret this as a
potential NAT rebinding and use a PATH_CHALLENGE frame to prove that
the peer endpoint is not truly at the new address, thus thwarting the
attack. A bleaching NAT has no means of sending an encrypted
PATH_CHALLENGE frame, so it might start redirecting all QUIC traffic
to the attacker address and thus allow an observer to break the
connection.
Kuehlewind & Trammell Expires 26 August 2021 [Page 25]
Internet-Draft QUIC Manageability February 2021
4.9. Filtering behavior
[RFC4787] describes possible packet filtering behaviors that relate
to NATs. Though the guidance there holds, a particularly unwise
behavior is to admit a handful of UDP packets and then make a
decision as to whether or not to filter it. QUIC applications are
encouraged to fail over to TCP if early packets do not arrive at
their destination. Admitting a few packets allows the QUIC endpoint
to determine that the path accepts QUIC. Sudden drops afterwards
will result in slow and costly timeouts before abandoning the
connection.
5. IANA Considerations
This document has no actions for IANA.
6. Security Considerations
QUIC is an encrypted and authenticated transport. That means, once
the cryptographic handshake is complete, QUIC endpoints discard most
packets that are not authenticated, greatly limiting the ability of
an attacker to interfere with existing connections.
However, some information is still observerable, as supporting
manageability of QUIC traffic inherently involves tradeoffs with the
confidentiality of QUIC's control information; this entire document
is therefore security-relevant.
More security considerations for QUIC are discussed in
[QUIC-TRANSPORT] and [QUIC-TLS], generally considering active or
passive attackers in the network as well as attacks on specific QUIC
mechanism.
Version Negotiation packets do not contain any mechanism to prevent
version downgrade attacks. However, future versions of QUIC that use
Version Negotiation packets are require to define a mechanism that is
robust against version downgrade attacks. Therefore a network node
should not attempt to impact version selection, as version downgrade
may result in connection failure.
7. Contributors
The following people have contributed text to sections of this
document:
* Dan Druta
* Martin Duke
Kuehlewind & Trammell Expires 26 August 2021 [Page 26]
Internet-Draft QUIC Manageability February 2021
* Marcus Ilhar
* Igor Lubashev
* David Schinazi
8. Acknowledgments
Special thanks to Martin Thomson and Martin Duke for the detailed
reviews and feedback.
This work is partially supported by the European Commission under
Horizon 2020 grant agreement no. 688421 Measurement and Architecture
for a Middleboxed Internet (MAMI), and by the Swiss State Secretariat
for Education, Research, and Innovation under contract no. 15.0268.
This support does not imply endorsement.
9. References
9.1. Normative References
[QUIC-TLS] Thomson, M. and S. Turner, "Using TLS to Secure QUIC",
Work in Progress, Internet-Draft, draft-ietf-quic-tls-34,
14 January 2021,
<https://tools.ietf.org/html/draft-ietf-quic-tls-34>.
[QUIC-TRANSPORT]
Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed
and Secure Transport", Work in Progress, Internet-Draft,
draft-ietf-quic-transport-34, 14 January 2021,
<https://tools.ietf.org/html/draft-ietf-quic-transport-
34>.
9.2. Informative References
[DOTS-ARCH]
Mortensen, A., Reddy, T., Andreasen, F., Teague, N., and
R. Compton, "DDoS Open Threat Signaling (DOTS)
Architecture", Work in Progress, Internet-Draft, draft-
ietf-dots-architecture-18, 6 March 2020,
<https://tools.ietf.org/html/draft-ietf-dots-architecture-
18>.
[IPIM] Allman, M., Beverly, R., and B. Trammell, "In-Protocol
Internet Measurement (arXiv preprint 1612.02902)", 9
December 2016, <https://arxiv.org/abs/1612.02902>.
Kuehlewind & Trammell Expires 26 August 2021 [Page 27]
Internet-Draft QUIC Manageability February 2021
[QUIC-APPLICABILITY]
Kuehlewind, M. and B. Trammell, "Applicability of the QUIC
Transport Protocol", Work in Progress, Internet-Draft,
draft-ietf-quic-applicability-09, 22 January 2021,
<https://tools.ietf.org/html/draft-ietf-quic-
applicability-09>.
[QUIC-HTTP]
Bishop, M., "Hypertext Transfer Protocol Version 3
(HTTP/3)", Work in Progress, Internet-Draft, draft-ietf-
quic-http-34, 2 February 2021,
<https://tools.ietf.org/html/draft-ietf-quic-http-34>.
[QUIC-INVARIANTS]
Thomson, M., "Version-Independent Properties of QUIC",
Work in Progress, Internet-Draft, draft-ietf-quic-
invariants-13, 14 January 2021,
<https://tools.ietf.org/html/draft-ietf-quic-invariants-
13>.
[QUIC-RECOVERY]
Iyengar, J. and I. Swett, "QUIC Loss Detection and
Congestion Control", Work in Progress, Internet-Draft,
draft-ietf-quic-recovery-34, 14 January 2021,
<https://tools.ietf.org/html/draft-ietf-quic-recovery-34>.
[QUIC_LB] Duke, M. and N. Banks, "QUIC-LB: Generating Routable QUIC
Connection IDs", Work in Progress, Internet-Draft, draft-
ietf-quic-load-balancers-06, 4 February 2021,
<https://tools.ietf.org/html/draft-ietf-quic-load-
balancers-06>.
[RFC1812] Baker, F., Ed., "Requirements for IP Version 4 Routers",
RFC 1812, DOI 10.17487/RFC1812, June 1995,
<https://www.rfc-editor.org/rfc/rfc1812>.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
<https://www.rfc-editor.org/rfc/rfc2475>.
[RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022,
DOI 10.17487/RFC3022, January 2001,
<https://www.rfc-editor.org/rfc/rfc3022>.
Kuehlewind & Trammell Expires 26 August 2021 [Page 28]
Internet-Draft QUIC Manageability February 2021
[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", STD 89,
RFC 4443, DOI 10.17487/RFC4443, March 2006,
<https://www.rfc-editor.org/rfc/rfc4443>.
[RFC4787] Audet, F., Ed. and C. Jennings, "Network Address
Translation (NAT) Behavioral Requirements for Unicast
UDP", BCP 127, RFC 4787, DOI 10.17487/RFC4787, January
2007, <https://www.rfc-editor.org/rfc/rfc4787>.
[RFC4937] Arberg, P. and V. Mammoliti, "IANA Considerations for PPP
over Ethernet (PPPoE)", RFC 4937, DOI 10.17487/RFC4937,
June 2007, <https://www.rfc-editor.org/rfc/rfc4937>.
[RFC5382] Guha, S., Ed., Biswas, K., Ford, B., Sivakumar, S., and P.
Srisuresh, "NAT Behavioral Requirements for TCP", BCP 142,
RFC 5382, DOI 10.17487/RFC5382, October 2008,
<https://www.rfc-editor.org/rfc/rfc5382>.
[RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS)
Extensions: Extension Definitions", RFC 6066,
DOI 10.17487/RFC6066, January 2011,
<https://www.rfc-editor.org/rfc/rfc6066>.
[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <https://www.rfc-editor.org/rfc/rfc7301>.
[RFC7605] Touch, J., "Recommendations on Using Assigned Transport
Port Numbers", BCP 165, RFC 7605, DOI 10.17487/RFC7605,
August 2015, <https://www.rfc-editor.org/rfc/rfc7605>.
[TLS-ESNI] Rescorla, E., Oku, K., Sullivan, N., and C. A. Wood, "TLS
Encrypted Client Hello", Work in Progress, Internet-Draft,
draft-ietf-tls-esni-09, 16 December 2020,
<https://tools.ietf.org/html/draft-ietf-tls-esni-09>.
[TMA-QOF] Trammell, B., Gugelmann, D., and N. Brownlee, "Inline Data
Integrity Signals for Passive Measurement (in Proc. TMA
2014)", April 2014.
[WIRE-IMAGE]
Trammell, B. and M. Kuehlewind, "The Wire Image of a
Network Protocol", RFC 8546, DOI 10.17487/RFC8546, April
2019, <https://www.rfc-editor.org/rfc/rfc8546>.
Kuehlewind & Trammell Expires 26 August 2021 [Page 29]
Internet-Draft QUIC Manageability February 2021
Appendix A. Appendix
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
A.1. 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.
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.
Kuehlewind & Trammell Expires 26 August 2021 [Page 30]
Internet-Draft QUIC Manageability February 2021
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.2. Extracting the CRYPTO frame
Kuehlewind & Trammell Expires 26 August 2021 [Page 31]
Internet-Draft QUIC Manageability February 2021
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
Mirja Kuehlewind
Ericsson
Email: mirja.kuehlewind@ericsson.com
Brian Trammell
Google
Gustav-Gull-Platz 1
CH- 8004 Zurich
Switzerland
Email: ietf@trammell.ch
Kuehlewind & Trammell Expires 26 August 2021 [Page 32]