Network Working Group                                         L. Colitti
Internet-Draft                                                    Google
Intended status: Informational                                  T. Pauly
Expires: 19 May 2021                                          Apple Inc.
                                                        15 November 2020

               Per-Application Networking Considerations


   This document describes considerations for and implications of using
   application identifiers as a method of differentiating traffic on
   networks.  Specifically, it discusses privacy considerations,
   possible mitigations, and considerations for user experience and API

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Source for this draft and an issue tracker can be found at

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   This Internet-Draft will expire on 19 May 2021.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   Please review these documents carefully, as they describe your rights
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions and Definitions . . . . . . . . . . . . . . .   3
   2.  Requesting differential treatment . . . . . . . . . . . . . .   3
   3.  Open Internet implications  . . . . . . . . . . . . . . . . .   4
   4.  Privacy implications  . . . . . . . . . . . . . . . . . . . .   4
   5.  Mitigating implications via traffic categories  . . . . . . .   5
   6.  User experience considerations  . . . . . . . . . . . . . . .   6
   7.  API considerations  . . . . . . . . . . . . . . . . . . . . .   6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   There are a number of use cases where network operators, or
   applications, might desire for application traffic to be treated
   differently by the network.  Some examples are:

   *  Network-specific services.  Applications might want to access
      local resources on a network that does not otherwise provide
      Internet access (for example, an entertainment system on an

   *  Per-application private networks.  Certain applications, such as
      enterprise applications, might want to connect directly to the
      enterprise network in a secure fashion without using a device-wide

   *  Mobile network services.  In mobile networks, applications like
      voice over LTE, IMS and RCS often use a different virtual network
      than general Internet traffic.

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   *  Applications with specific performance requirements.  Certain
      applications would benefit from particular scheduling or QoS
      policies - for example applications requiring low latency such as
      voice might be scheduled and queued differently from latency-
      insensitive traffic.

   *  Local breakout.  In a mobile networks, applications might want to
      access resources through a different network interface (e.g., one
      that uses IPv6 addresses that are local to a specific area, and do
      not have a wide mobility).

   *  Zero-rating traffic.  As allowed by regulators, certain classes of
      traffic (e.g., messaging or streaming video) might be exempt from
      metering on networks that are otherwise metered.

   In existing networks, this is sometimes implemented by the network
   using deep packet inspection (e.g., flow tracking coupled with
   inspection of the SNI handshake).  This is complex, implicates public
   policy concerns, and generally conflicts with the recommendations in
   [RFC7258].  The move towards encrypted protocols such as [RFC8484]
   and [I-D.ietf-tls-esni] will make this more difficult for some
   operators.  Thus, if an application is to receive different
   treatment, the host or the application itself should be involved in
   requesting specific network treatment.  This document explores the

   In this document, the term "application" refers to an application as
   understood by the user of the device.

1.1.  Conventions and Definitions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Requesting differential treatment

   There are already mechanisms for applications to request and obtain
   particular treatment by the network, or to communicate application
   identity to the network in order to obtain particular treatment.
   These include:

   *  Diffserv

   *  APN6

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   *  Network tokens

   *  Slicing in 3GPP 5G networks

   *  Explicit application selection of a given Provisioning Domain
      (PvD) [RFC8801]

3.  Open Internet implications

   In certain regulatory regions, networks that provide general Internet
   access may not be permitted to discriminate between traffic sent to
   or from different lawful applications or websites, or such
   discrimination may be prohibited if commercially based.  In a
   situation where the network operator has influence on the
   implementation of the user host (e.g., mobile networks where the
   handset is sold by the carrier), the device may be able to implement
   network policies directly, and thus may be impacted by neutrality

   Neutrality concerns can be addressed by providing user control over
   assignment of particular applications to the particular network
   resources available to that user.  Further, network neutrality
   implications may be reduced or avoided in some jurisdictions if the
   differential treatment occurs between different classes of traffic
   with different network requirements (e.g., bandwidth-intensive
   traffic vs. low-latency traffic) as opposed to between different
   applications with similar network requirements, and thus, by ensuring
   that the mechanism used to communicate requests to the network only
   specifies traffic classes and not individual applications.

4.  Privacy implications

   IETF guidance to avoid pervasive monitoring [RFC7258] is for network
   protocols to expose as little information as possible.  Some of the
   proposed technologies for application signalling rely on the
   application exposing its identity to the network so that the network
   can then implement appropriate policies.  This may provide the
   network with much more information than is needed to implement the
   desired behaviour.  Information about which users are using specific
   applications, or visiting certain destinations, and when, can be
   highly privacy-sensitive.

   Note that application identity can be exposed to the network even in
   the absence of explicit signalling.  For example, if the host were to
   implement a network-set policy that requires that traffic from
   application X be sent on a different network path than all other
   traffic, the identity of application X would be exposed to the
   network as soon as it sends traffic.

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   Privacy concerns may also be reduced or avoided if the mechanism to
   request a different class of service only specifies the class of
   service (e.g., "low latency" or "streaming video") instead of the
   application originating the traffic.

   In a situation where the network operator has influence over the
   implementation of the user host, the operator can still impose
   policies on what requests are possible - for example, the operator
   might choose to limit access to specialized services such as carrier
   messaging only to carrier applications.  It is possible for such
   policies to preserve privacy if the policies specify general
   categories of traffic as opposed to specifying applications.

5.  Mitigating implications via traffic categories

   Many of these implications can be mitigated if the mechanism does not
   request different treatment of a service for a particular
   application, but instead specifies a general category of traffic,
   especially one that is defined based on traffic properties rather
   than commercial agreements.

   Categories of traffic need to be sufficiently broad to not identify
   individual applications, and should be general enough that details
   about a user cannot be inferred merely by use of the category.

   Consider the example a network that wants to provide differentiated
   service for a role-playing game application that can take advantage
   of a low-latency path.  Several levels of categories could be
   defined.  The following list shows some examples, in order of
   decreasing specificity:

   1.  Role-playing game

   2.  Game

   3.  Real-time/low-latency

   The first category would not be an appropriate choice due to the
   privacy implications of identifying what kind of game a user plays.
   The second category is preferable, but the third is best since it
   defines a way to manage the network traffic without identifying
   anything about the content of the application.

   Some use cases for traffic differentiation might need other kinds of
   categories.  For example, operators might wish to zero-rate
   applications using categories based on payment tiers and rate-

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6.  User experience considerations

   Privacy and neutrality concerns can be mitigated if the host's user
   is informed that particular applications are seeking or designated
   for particular treatment and consents to it.  In order for consent to
   be meaningful, the user should be presented with a message that they
   understand.  It may be difficult to balance the goal of providing
   complete and accurate information with the goal of ensuring that the
   user understands the implications.

7.  API considerations

   It is desirable to provide an API layer that is not tied to specific
   network technologies (e.g., URSP, VPN, etc.).  Having applications
   select a specific Provisioning Domain (PvD) could provide a useful
   layer of abstraction, as described in [I-D.ietf-taps-interface].

   Any API should not involve revealing an application or user identity
   to the network via metadata without network authentication.  Instead,
   the API should allow a given setting to be conditional on the
   identity of the network.  For example, an application should express
   "use the zero-rated service for my app when on a particular carrier
   network", instead of blindly saying "this is my application

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.

8.2.  Informative References

              Trammell, B., Welzl, M., Enghardt, T., Fairhurst, G.,
              Kuehlewind, M., Perkins, C., Tiesel, P., Wood, C., and T.
              Pauly, "An Abstract Application Layer Interface to
              Transport Services", Work in Progress, Internet-Draft,
              draft-ietf-taps-interface-10, 2 November 2020,

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              Rescorla, E., Oku, K., Sullivan, N., and C. Wood, "TLS
              Encrypted Client Hello", Work in Progress, Internet-Draft,
              draft-ietf-tls-esni-08, 16 October 2020,

   [RFC7258]  Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
              Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
              2014, <>.

   [RFC8484]  Hoffman, P. and P. McManus, "DNS Queries over HTTPS
              (DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,

   [RFC8801]  Pfister, P., Vyncke, É., Pauly, T., Schinazi, D., and W.
              Shao, "Discovering Provisioning Domain Names and Data",
              RFC 8801, DOI 10.17487/RFC8801, July 2020,


   Thanks to Adi Masputra and Elliot Briggs for their inputs to this

Authors' Addresses

   Lorenzo Colitti
   Shibuya 3-21-3,


   Tommy Pauly
   Apple Inc.
   One Apple Park Way
   Cupertino, California 95014,
   United States of America


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