Internet DRAFT - draft-kuehlewind-quic-manageability
draft-kuehlewind-quic-manageability
Network Working Group M. Kuehlewind
Internet-Draft B. Trammell
Intended status: Informational ETH Zurich
Expires: September 10, 2017 D. Druta
AT&T
March 09, 2017
Manageability of the QUIC Transport Protocol
draft-kuehlewind-quic-manageability-00
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
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the Trust Legal Provisions and are provided without warranty as
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3
2. Features of the QUIC Wire Image . . . . . . . . . . . . . . . 3
2.1. QUIC Packet Header Structure . . . . . . . . . . . . . . 3
2.2. Integrity Protection of the Wire Image . . . . . . . . . 4
2.3. Connection ID and Rebinding . . . . . . . . . . . . . . . 4
2.4. Packet Numbers . . . . . . . . . . . . . . . . . . . . . 5
2.5. Greasing . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Specific Network Management Tasks . . . . . . . . . . . . . . 5
3.1. Stateful Treatment of QUIC Traffic . . . . . . . . . . . 5
3.2. Measurement of QUIC Traffic . . . . . . . . . . . . . . . 6
3.3. DDoS Detection and Mitigation . . . . . . . . . . . . . . 6
3.4. QoS support and ECMP . . . . . . . . . . . . . . . . . . 7
3.5. Load balancing . . . . . . . . . . . . . . . . . . . . . 8
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. Normative References . . . . . . . . . . . . . . . . . . 9
7.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
QUIC [I-D.ietf-quic-transport] is a new transport protocol currently
under development in the IETF quic working group, focusing on support
of semantics as needed for HTTP/2 [I-D.ietf-quic-http]. Based on
current deployment practices, QUIC is encapsulated in UDP and
encrypted by default. The current version of QUIC integrates TLS
[I-D.ietf-quic-tls] to encrypt all payload data and most header
information. Given QUIC is an end-to-end transport protocol, all
information in the protocol header, even that which can be inspected,
is is not meant to be mutable by the network, and will therefore be
integrity-protected to the extent possible.
This document provides guidance for network operation on the
management of QUIC traffic. This includes guidance on how to
interpret and utilize information that is exposed by QUIC to the
network as well as explaining requirement and assumptions that the
QUIC protocol design takes toward the expected network treatment. It
also discusses how common network management practices will be
impacted by QUIC.
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Of course, 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.
QUIC is at the moment very much a moving target. This document
refers the state of the QUIC working group drafs as well as to
changes under discussion, via issues and pull requests in GitHub
current as of the time of writing.
1.1. Notational Conventions
The words "MUST", "MUST NOT", "SHOULD", and "MAY" are used in this
document. It's not shouting; when these words are capitalized, they
have a special meaning as defined in [RFC2119].
2. Features of the QUIC Wire Image
In this section, we discusses 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
QUIC's unencrypted 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, everything
about the header format can change except the mechanism by which a
receiver can determine whether and where a version number is present,
and the meaning of the fields used in the version negotiation
process. This document is focused on the protocol as presently
defined in [I-D.ietf-quic-transport] and [I-D.ietf-quic-tls], and
will change to track those documents.
2.1. QUIC Packet Header Structure
The QUIC packet header is under active development; see section 5 of
[I-D.ietf-quic-transport] for the present header structure, and
https://github.com/quicwg/base-drafts/pull/361 for one current
proposed redesign.
Currently the first bit of the QUIC header indicates the present of a
long header that exposed more information than the short. The long
header is typically used during connection start or for other control
processes while the short header will be used on mostly packets to
limited unnecessary header overhead. The following information may
be exposed in the packet header:
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o version number: The version number is present during version
negotiation.
o connection ID: The connection ID identifies the connection
associated with a QUIC packet, for load-balancing and NAT
rebinding purposes; see Section 2.3.
o packet number: Every packet has an associated packet number; this
packet number increases with each packet, and the least-
significant bits of the packet number are present on each packet;
see Section 2.4.
o public reset indication: Public reset packets expose the fact that
a connection is being torn down to devices along the path. The
applicability of public reset is currently under discussion; see
https://github.com/quicwg/base-drafts/issues/353 and
https://github.com/quicwg/base-drafts/pull/20.
o key phase: To support 0-RTT session establishment, QUIC uses two
key phases; the key phase of each packet must be exposed to
support efficient reception.
o additional flags: Additional flags for diagnostic use are also
under consideration; see https://github.com/quicwg/base-drafts/
issues/279.
[Editor's note: also further discuss which bits cannot change with
versioning]
2.2. Integrity Protection of the Wire Image
As soon as the cryptograhic context is established, all information
in the QUIC header, including that exposed in the packet header, is
integrity protected. Therefore, devices on path MUST NOT change QUIC
packet headers, as alteration of header information would cause
packet drop due to a failed integrity check at the receiver.
2.3. Connection ID and Rebinding
The connection ID in the QUIC packer header is used to allow 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, in the case of
the HTTP binding. The connection ID is proposed by the server during
connection establishment. A flow might change one of its IP
addresses but keep the same connection ID, as noted in Section 2.1,
and the connection ID may change during a connection as well; see
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section 6.3 of [I-D.ietf-quic-transport]. See also
https://github.com/quicwg/base-drafts/issues/349 for ongoing
discussion of the Connection ID.
2.4. Packet Numbers
The packet number field is always present in the QUIC packet header.
The packet number exposes the least significant 32, 16, or 8 bits of
an internal packet counter per flow direction that increments with
each packet sent. This packet counter is initialized with a random
31-bit initial value at the start of a connection.
Unlike TCP sequence numbers, this packet number increases with every
packet, including those containing only acknowledgment or other
control information. Indeed, whether a packet contains user data or
only control information is intentionally left unexposed to the
network.
While loss detection in QUIC is based on packet numbers, congestion
control by default provides richer information than vanilla TCP does.
Especially, QUIC does not rely on duplicated ACKs, making it more
tolerant of packet re-ordering.
2.5. Greasing
[Editor's note: say something about greasing if added to the
transport draft]
3. Specific Network Management Tasks
In this section, we address specific network management and
measurement techniques and how QUIC's design impacts them.
3.1. Stateful Treatment of QUIC Traffic
Stateful network devices such as firewalls use exposed header
information to support state setup and tear-down.
[I-D.trammell-plus-statefulness] provides a general model for in-
network state management on these devices, independent of transport
protocol. Features already present in QUIC may be used for state
maintenance in this model. Here, there are two important goals:
distinguishing valid QUIC connection establishment from other
traffic, in order to establish state; and determining the end of a
QUIC connection, in order to tear that state down.
1-RTT connection establishment, using a TLS handshake on stream 0, is
detectable using heuristics similar to those used to detect TLS over
TCP. 0-RTT connection establishment, however, provides no particular
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heuristic for differentiation from random background traffic at this
time.
Exposure of connection shutdown is currently under discussion; see
https://github.com/quicwg/base-drafts/issues/353 and
https://github.com/quicwg/base-drafts/pull/20.
3.2. Measurement of QUIC Traffic
Passive measurement of TCP performance parameters is commonly
deployed in access and enterprise networks to aid troubleshooting and
performance monitoring without requiring the generation of active
measurement traffic.
The presence of packet numbers on most QUIC packets allows the
trivial one-sided estimation of packet loss and reordering between
the sender and a given observation point. However, since
retransmissions are not identifiable as such, loss between an
observation point and the receiver cannot be reliably estimated.
The lack of any acknowledgement information or timestamping
information in the QUIC packet header makes running passive
estimation of latency via round trip time (RTT) impossible. RTT can
only be measured at connection establishment time, and only when
1-RTT establishment is used.
Note that adding packet number echo (as in https://github.com/quicwg/
base-drafts/pull/367 or https://github.com/quicwg/base-drafts/
pull/368) to the public header would allow passive RTT measurement at
on-path observation points. For efficiency purposes, this packet
number echo need not be carried on every packet, and could be made
optional, allowing endpoints to make a measurability/efficiency
tradeoff; see section 4 of [IPIM]. Note further that this facility
would have significantly better measurability characteristics than
sequence-acknowledgement-based RTT measurement currently available in
TCP on typical asymmetric flows, as adequate samples will be
available in both directions, and packet number echo would be
decoupled from the underlying acknowledgment machinery; see e.g.
[Ding2015]
Note in-network devices can inspect and correlate connection IDs for
partial tracking of mobility events.
3.3. DDoS Detection and Mitigation
For enterprises and network operators one of the biggest management
challenges is dealing with Distributed Denial of Service (DDoS)
attacks. Some network operators offer Security as a Service (SaaS)
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solutions that detect attacks by monitoring, analyzing and filtering
traffic. These approaches generally utilize network flow data
[RFC7011]. If any flows pose a threat, usually they are routed to a
"scrubbing environment" where the traffic is filtered, allowing the
remaining "good" traffic to continue to the customer environment.
This type of DDoS mitigation is fundamentally based on tracking state
for flows (see Section 3.1) that have receiver confirmation and a
proof of return-routability, and classifying flows as legitimate or
DoS traffic. The QUIC packet header currently does not support an
explicit mechanism to easily distinguish legitimate QUIC traffic from
other UDP traffic. However, the first packet in a QUIC connection
will usually be a client cleartext packet with a version field and a
connection ID. This can be used to identify the first packet of the
connection (also see https://github.com/quicwg/base-drafts/
issues/185).
If the QUIC handshake was not observed by the defense system, the
connection ID can be used as a confirmation signal as per
[I-D.trammell-plus-statefulness]. In this case, similar as for all
in-network functions that rely on the connection ID, a defense system
can only rely on this signal for known QUIC's versions and if the
connection ID is present (also see https://github.com/quicwg/base-
drafts/issues/293).
Further, 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. However, it is
questionable if connection migrations needs to be supported in a DDOS
attack or if a defense system might simply rely on the fast
resumption mechanism provided by QUIC. This problem is also related
to these issues under discussion: https://github.com/quicwg/base-
drafts/issues/203 and https://github.com/quicwg/base-drafts/
issues/349
3.4. QoS support and ECMP
QUIC does not provide any additional information on requirements on
Quality of Service (QoS) provided from the network. QUIC assumes
that all packets with the same 5-tuple {dest addr, source addr,
protocol, dest port, source port} will receive similar network
treatment. That means all stream that are multiplexed over the same
QUIC connection require the same network treatment and are handled by
the same congestion controller. If differential network treatment is
desired, multiple QUIC connection to the same server might be used,
given that establishing a new connection using 0-RTT support is cheap
and fast.
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QoS mechanisms in the network MAY also use the connection ID for
service differentiation as usually a change of connection ID is bind
to a change of address which anyway is likely to lead to a re-route
on a different path with different network characteristics.
Given that QUIC is more tolerant of packet re-ordering than TCP (see
Section 2.4), Equal-cost multi-path routing (ECMP) does not
necessarily need to be flow based. However, 5-tuple (plus eventually
connection ID if present) matching is still beneficial for QoS given
all packets are handled by the same congestion controller.
3.5. Load balancing
[Editor's note: explain how this works as soon as we have decided who
chooses the connection ID and when to set it. Related to
https://github.com/quicwg/base-drafts/issues/349]
4. IANA Considerations
This document has no actions for IANA.
5. Security Considerations
Supporting manageability of QUIC traffic inherently involves
tradeoffs with the confidentiality of QUIC's control information;
this entire document is therefore security-relevant.
Some of the properties of the QUIC header used in network management
are irrelevant to application-layer protocol operation and/or user
privacy. For example, packet number exposure (and echo, as proposed
in this document), as well as connection establishment exposure for
1-RTT establishment, make no additional information about user
traffic available to devices on path.
At the other extreme, supporting current traffic classification
methods that operate through the deep packet inspection (DPI) of
application-layer headers are directly antithetical to QUIC's goal to
provide confidentiality to its application-layer protocol(s); in
these cases, alternatives must be found.
6. Acknowledgments
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.
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7. References
7.1. Normative References
[I-D.ietf-quic-tls]
Thomson, M. and S. Turner, "Using Transport Layer Security
(TLS) to Secure QUIC", draft-ietf-quic-tls-01 (work in
progress), January 2017.
[I-D.ietf-quic-transport]
Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed
and Secure Transport", draft-ietf-quic-transport-01 (work
in progress), January 2017.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
7.2. Informative References
[Ding2015]
Ding, H. and M. Rabinovich, "TCP Stretch Acknowledgments
and Timestamps - Findings and Impliciations for Passive
RTT Measurement (ACM Computer Communication Review)", July
2015.
[draft-kuehlewind-quic-applicability]
Kuehlewind, M. and B. Trammell, "Applicability of the QUIC
Transport Protocol", March 2017.
[I-D.ietf-quic-http]
Bishop, M., "Hypertext Transfer Protocol (HTTP) over
QUIC", draft-ietf-quic-http-01 (work in progress), January
2017.
[I-D.trammell-plus-statefulness]
Kuehlewind, M., Trammell, B., and J. Hildebrand,
"Transport-Independent Path Layer State Management",
draft-trammell-plus-statefulness-02 (work in progress),
December 2016.
[IPIM] Allman, M., Beverly, R., and B. Trammell, "In-Protocol
Internet Measurement (arXiv preprint 1612.02902)",
December 2016.
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[RFC7011] Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
"Specification of the IP Flow Information Export (IPFIX)
Protocol for the Exchange of Flow Information", STD 77,
RFC 7011, DOI 10.17487/RFC7011, September 2013,
<http://www.rfc-editor.org/info/rfc7011>.
Authors' Addresses
Mirja Kuehlewind
ETH Zurich
Gloriastrasse 35
8092 Zurich
Switzerland
Email: mirja.kuehlewind@tik.ee.ethz.ch
Brian Trammell
ETH Zurich
Gloriastrasse 35
8092 Zurich
Switzerland
Email: ietf@trammell.ch
Dan Druta
AT&T
Email: dd5826@att.com
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