Network Working Group                                      M. Kuehlewind
Internet-Draft                                               B. Trammell
Intended status: Informational                                ETH Zurich
Expires: September 10, 2017                                     D. Druta
                                                          March 09, 2017

              Manageability of the QUIC Transport Protocol


   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.

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   This Internet-Draft will expire on September 10, 2017.

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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 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

   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 and

   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

   [Editor's note: also further discuss which bits cannot change with

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 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

   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

   Exposure of connection shutdown is currently under discussion; see and

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
   base-drafts/pull/367 or
   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.

   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

   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

   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:
   drafts/issues/203 and

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]

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

              Thomson, M. and S. Turner, "Using Transport Layer Security
              (TLS) to Secure QUIC", draft-ietf-quic-tls-01 (work in
              progress), January 2017.

              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,

7.2.  Informative References

              Ding, H. and M. Rabinovich, "TCP Stretch Acknowledgments
              and Timestamps - Findings and Impliciations for Passive
              RTT Measurement (ACM Computer Communication Review)", July

              Kuehlewind, M. and B. Trammell, "Applicability of the QUIC
              Transport Protocol", March 2017.

              Bishop, M., "Hypertext Transfer Protocol (HTTP) over
              QUIC", draft-ietf-quic-http-01 (work in progress), January

              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,

Authors' Addresses

   Mirja Kuehlewind
   ETH Zurich
   Gloriastrasse 35
   8092 Zurich


   Brian Trammell
   ETH Zurich
   Gloriastrasse 35
   8092 Zurich


   Dan Druta


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