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QUIC WG                                                     E. Stephan
Internet Draft                                                M. Cayla
Intended status: Informational                                A. Braud
Expires: January 2018                                         F. Fieau
                                                          July 3, 2017

                     QUIC Interdomain Troubleshooting

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on January 3, 2018.

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   On-path network performance measurements methods currently deployed
   contribute to the ossification of the Internet because they are
   expensive to deploy and to maintain. This draft motivates the
   exposure of QUIC header fields for on-path network measurements and
   their specification in the QUIC core protocol as a solution to avoid
   on-path network performance measurements to ossify the IP stack in
   the future.

Table of Contents

   1. Introduction ................................................ 2
   2. Conventions used in this document............................ 3
   3. Interdomain UX troubleshooting............................... 3
   4. Reference of Network Performance............................. 4
   5. QUIC Fallback ............................................... 5
   5.1. Flapping .................................................. 6
   6. Versioning and Implementations............................... 6
   7. Security Considerations...................................... 6
   8. IANA Considerations ......................................... 7
   9. Discussions ................................................. 7
   9.1. Fallback .................................................. 7
   9.2. On-path Measurement........................................ 7
   10. References ................................................. 8
   10.1. Normative References...................................... 8
   10.2. Informative References.................................... 8
   11. Acknowledgments ............................................ 8

1. Introduction

   The IP layer does not include the material for measuring the delay
   and packets losses of segments of a path. The network performance is
   currently measured by points of presence of the path [SPATIAL],
   [COMPO] using transport fields of the upper layers: TCP transport
   layer, RTP application layer...

   The evolution of the Internet stack toward end-to-end integrity
   protection is unavoidable [IABSEC]. This document presents the
   benefits of preserving the same on-path network performance
   measurement capabilities in the evolution of TCP (TCP/TLS, TCPinc...)
   and UDP (QUIC/UDP...) currently specified at the IETF.

   On-path network performance measurements methods currently deployed
   contribute to the ossification of the Internet because they are

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   expensive to deploy and complex to maintain. This is due to the use
   of protocols' fields not primarily designed for this purpose. This
   draft motivates the exposure of the fields for on-path network
   performance measurements in the QUIC core protocol to avoid network
   performance measurements to ossify the IP stack in the future.

   The memo recalls the UX interdomain troubleshooting complexity
   [Issue166] introduced by QUIC deployment. Then it describes
   operational concerns QUIC fallbacks and discusses the potential
   impacts on the security. Finally it discusses the benefits of
   exposing durably the fields needed for measuring packet delay and

2. Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

3. Interdomain UX troubleshooting

   Fast troubleshooting of networks performance is mandatory to maintain
   end-users high Quality of Experience.

   Troubleshooting is the act of identifying the origin of a problem. A
   major case is the localization of troubles impacting a large number
   of customers. This case becomes critical when it appears suddenly and
   represents a noticeable part of the traffic between the entity that
   connects customers (ISP) and the entity that provides the data (APP).

   It becomes critical because network operation center (NOC) teams of
   the two entities are expected to immediately identify the causes in
   order to restore UX as quickly as possible. Each team checks that the
   point of failure is either in their entity or outside. When they
   located the point of failure in their entity they investigate their
   own chains of components (network, routers, reverse proxies,...) and
   quickly fix the issue.

   It becomes extremely critical when an entity locates the point of
   failure outside of their entity. In this case the time needed to fix
   the problem is much longer and unpredictable because it expects other
   entities on the path to perform the same actions on their segments.

   There are many cases of troubleshooting. A typical example starts by
   signaling to the ISP that its end-users are experiencing a
   significant decrease of QoE when using an Internet application.

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   Typical point of failures can be line cards memory errors or
   overloaded routers located somewhere on the path, either in the ISP
   domain or outside.

   The ISP NOC has to localize asap the point of failure. Currently it
   proceeds by dichotomy (is the point of failure inside ISP domain or
   outside?) using passive monitoring of packet loss and congestion.

   Following is the description of the parameters in use:

   Packet lost downstream (vice versa for upstream):

   o Measure of packet loss before the point of measure needs TCP
      sequence number;

   o Measure of loss located after the point of measure needs TCP ACK +


   o Detects that the congestion is located either before or after the
      point of measure;

   o The analysis is based on TCP ACK+SACK observation.

4. Reference of Network Performance

   A reference of the real performance of the network is not always
   provided by counters of network equipment. Counters may not be
   implemented, values are not always stable, their values could be
   compromised in case of software bugs or equipment congestion... In
   addition, to face the increasing network architecture complexity
   involved by the evolution of access networks, security and hosting
   infrastructures, NOCs need reliable network performance measurement
   in near real time.

   In practice, these measurement tools shall be able to monitor
   numerous points and interfaces within the network to provide near
   real time network performances indicators taking into account the
   global network state.

   These measurements systems can also allow detecting issues or
   unexplained behaviors on equipment, links, peers: for instance, in
   mobile networks, operators shall be able to identify in real time
   bottleneck links responsible for customer experience degradation and
   take necessary actions to avoid further snowball effect.

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   Charging of data usage is another key feature for Mobile Network
   Operators where per flow accurate information is collected. It is
   important to reconcile values between amount of charged data and
   amount of data seen by the network (cf discussion on goodput in
   section 6)). This could allow detecting fraud attempts or
   dysfunctions within the network. In case of significant gap,
   operators must be able to react quickly to isolate this traffic.
   Additionally, charging may require the differentiation of the goodput
   from the throughput.

   Continuous network performance monitoring requires packet losses and
   delay measurements to allow operators to manage properly their
   networks and to provides them with a reference of performance of
   their network for interdomain troubleshooting.

5. QUIC Fallback

   Fallback is necessary to address cases where a QUIC connection
   establishment fails [QUICAPP] (A device of the path blocks UDP, the
   stack blocks 0-RTT...).

   Fallback may occur additionally when an active QUIC connection drops
   and tries to reconnect. As an example, the steps of the fallback
   could be:

   o The QUIC connection drops accidently;

   o The UA fallback and connects in TCP/TLS to the origin server;

   o The UA receives from the origin server an indication for an
      alternate service [ALTSVC] supporting QUIC;

   o The UA ends gracefully the TCP connection;

   o The UA tries to establish a QUIC connection to the server and port
      described in the alternate service indication;

   o The QUIC 1-RTT connection is established;

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5.1. Flapping

   A fallback may suddenly occur when one or more elements (links,
   nodes, reverse proxy, switch, server ...) of the path fail or are

   There are cases where the fallback loops and triggers flapping
   between the origin server and the alternate server. As an example,
   this might happen when an alternate service indication is outdated
   and points to a server which does not support QUIC anymore.

   This becomes critical for UX when numerous fallbacks occur suddenly
   on the same path between a set of customers of an ISP and another
   entity which provides the application data. The time to troubleshoot
   can be very long. The origin server and the alternate servers can be
   hosted by different entities.

6. Versioning and Implementations

   Versioning is an important part of the QUIC protocol framework
   [QUICCORE]. Multiple versions of the protocol are expected to be
   deployed and used concurrently. In order to encourage networks to
   rapidly support the QUIC protocol and to support any versions of QUIC
   in the future, the exposure of the fields for on-path network
   performance measurement must not depend on the version.

   There might be numerous implementations of the QUIC protocol in the
   future. An important part of them will implement the congestion
   control at application level. There will be unfair behaviors like
   abnormal retransmission rate which will impact the fairness of the
   repartition of the bandwidth amongst the customers of the network. By
   consequence the network needs to be able to detect connections which
   have abnormal throughput/goodput.

7. Security Considerations

   The integrity of the transport parameters exposed for measuring on-
   path delay and losses can be end-to-end protected to increase the
   security of the connection. Additionally it helps end-points and on-
   path points of presence to compute metrics based on the same raw

   Flapping from QUIC to a fallback protocol might overload on-path
   devices and end-points and by consequence affect the stability of the
   connections and introduces weaknesses.

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   The fallback from encrypted headers to clear headers transport
   protocols might open the door to new types of active attacks.

   It is not clear yet whether a network can distinguish numerous QUIC
   fallback flappings from an active attack:

   o What is the expected behavior from the network?

   o Will networks detect QUIC flapping as an active attack?

8. IANA Considerations

   This draft does not request any IANA actions.

9. Discussions

9.1. Fallback

   Troubleshooting QUIC traffic and its fallbacks requires measuring
   similar metrics. One suggestion is to use the integrity mechanism of
   the TCPinc WG [TCPINC] to protect and keep visible the fields used
   for on-path measurement.

   Fallback must be precisely specified in the core specification of

   To avoid unnecessary flapping [QUICCORE] might clarify the usage of
   the advertisement of QUIC support in HTTP protocols [ALTSVC].

   [QUICMAN] should propose guidance for the management of QUIC fallback
   flapping situations.

   QUIC packets numbering should be continuous to allow packet loss
   monitoring. Flows control fields (ACK, SACK) are available in QUIC
   but encrypted.

9.2. On-path Measurement

   QUIC is designed to carry other traffic than HTTP such as DNS and
   Web. End-to-end encryption of the transport headers prevents the use
   of models [E-MODEL] and heuristics to estimate UX on a path segment.
   To maintain a high level of UX, QUIC capabilities should support the
   measurement of the delay and the losses of a segment of a source to
   destination path.

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   On-path measurement techniques are currently ad hoc. Adding the
   exposure of the fields for on-path packet delay and losses in the
   core specification of the QUIC protocol creates a stable network
   performance measurement framework. It will be a real incentive for
   networks to support QUIC rapidly and to support the numerous QUIC
   versions in the future. This will reduce network impacts on the
   ossification of the IP stack in the future.

10. References

10.1. Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.

    [ALTSVC] https://tools.ietf.org/html/rfc7838

   [QUICCORE] https://tools.ietf.org/html/draft-ietf-quic-transport

   [QUICAPP] https://tools.ietf.org/wg/quic/draft-kuehlewind-quic-

   [QUICMAN] https://tools.ietf.org/wg/quic/draft-kuehlewind-quic-

   [TCPINC]  https://tools.ietf.org/wg/tcpinc/

   [Issue166]  https://github.com/quicwg/base-drafts/issues/166

   [IABSEC] https://www.iab.org/2014/11/14/iab-statement-on-internet-

10.2. Informative References

   [E-MODEL]  https://www.itu.int/rec/T-REC-G.107-199812-S/en

   [SPATIAL]  https://tools.ietf.org/html/rfc5644

   [COMPO]  https://tools.ietf.org/html/rfc6049

11. Acknowledgments

   This document was prepared using 2-Word-v2.0.template.dot.

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Authors' Addresses

   Emile Stephan
   2, avenue Pierre Marzin
   Lannion 22300

   Email: emile.stephan@orange.com

   Mathilde Cayla
   6, avenue Albert Durand
   Blagnac 31700

   Email: mathilde.cayla@orange.com

   Arnaud Braud
   2, avenue Pierre Marzin
   Lannion 22300

   Email: arnaud.braud@orange.com

   Fred Fieau
   40-48, avenue de la Republique
   Chatillon 92320

   Email: frederic.fieau@orange.com

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