Internet Architecture Board                                    N. Rooney
Internet-Draft                                                      GSMA
Intended status: Informational                           S. Dawkins, Ed.
Expires: November 26, 2018                                Wonder Hamster
                                                            May 25, 2018

 IAB Workshop on Managing Radio Networks in an Encrypted World (MaRNEW)


   The Internet Architecture Board (IAB) and GSM Association (GSMA) held
   a joint workshop on "Managing Radio Networks in an Encrypted World"
   (MaRNEW), on September 24-25, 2015.  This workshop aimed to discuss
   solutions for bandwidth optimisation on mobile networks for encrypted
   content, as current solutions rely on unencrypted content which is
   not indicative of the security needs of today's Internet users.  The
   workshop gathered IETF attendees, IAB members and participants from
   various organisations involved in the telecommunications industry
   including original equipment manufacturers, content providers, and
   mobile network operators.

   The group discussed the current Internet encryption trends and
   deployment issues identified within the IETF, and the privacy needs
   of users which should be adhered.  Solutions designed around sharing
   data from the network to the endpoints and vice versa were then
   discussed as well as analysing whether issues experienced when using
   current transport layer protocols are also playing a role here.
   Content providers and CDNs gave their own views of their experiences
   delivering their content with mobile network operators.  Finally,
   technical responses to regulation was discussed to help the regulated
   industries relay the issues of impossible-to-implement or bad-for-
   privacy technologies back to regulators.

   A group of suggested solutions were devised which will be discussed
   in various IETF groups moving forward.

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
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   Drafts is at

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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on November 26, 2018.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Understanding "Bandwidth Optimization"  . . . . . . . . .   3
     1.2.  Topics  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.3.  Organization of this report . . . . . . . . . . . . . . .   5
     1.4.  Use of Note Well and Chatham House Rule . . . . . . . . .   5
     1.5.  IETF and GSMA . . . . . . . . . . . . . . . . . . . . . .   5
   2.  Scene Setting Sessions  . . . . . . . . . . . . . . . . . . .   6
     2.1.  Scene Setting . . . . . . . . . . . . . . . . . . . . . .   6
       2.1.1.  Scope . . . . . . . . . . . . . . . . . . . . . . . .   6
       2.1.2.  Encryption Statistics and Radio Access Network
               Differences . . . . . . . . . . . . . . . . . . . . .   7
     2.2.  Encryption Deployment Considerations  . . . . . . . . . .   8
     2.3.  Awareness of User Choice (Privacy)  . . . . . . . . . . .   8
   3.  Network or Transport Solution Sessions  . . . . . . . . . . .   9
     3.1.  Sending Data Up / Down for Network Management Benefits  .  10
       3.1.1.  Competition, Cooperation, and Mobile Network
               Complexities  . . . . . . . . . . . . . . . . . . . .  11
   4.  Transport Layer: Issues, Optimisation and Solutions . . . . .  11
   5.  Application Layer Optimisation, Caching and CDNs  . . . . . .  12
   6.  Technical Analysis and Response to Potential Regulatory
       Reaction  . . . . . . . . . . . . . . . . . . . . . . . . . .  13
   7.  Suggested Principles and Solutions  . . . . . . . . . . . . .  14
     7.1.  Better Collaboration  . . . . . . . . . . . . . . . . . .  17
   8.  Since MaRNEW  . . . . . . . . . . . . . . . . . . . . . . . .  17
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  18
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  19
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  19

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   12. Informative References  . . . . . . . . . . . . . . . . . . .  19
   Appendix A.  Workshop Attendees . . . . . . . . . . . . . . . . .  22
   Appendix B.  Workshop Position Papers . . . . . . . . . . . . . .  24
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  26

1.  Introduction

   The Internet Architecture Board (IAB) and GSM Association (GSMA) held
   a joint workshop on "Managing Radio Networks in an Encrypted World"
   (MaRNEW), on September 24-25, 2015.  This workshop aimed to discuss
   solutions for bandwidth optimisation on mobile networks for encrypted
   content, as current solutions rely on unencrypted content which is
   not indicative of the security needs of today's Internet users.

   Mobile networks have a set of properties which places a large
   emphasis on sophisticated bandwidth optimization.  Encryption is
   increasing on the Internet which is positive for consumer and
   business privacy and security.  Many existing mobile bandwidth
   optimization solutions primarily operate on non-encrypted
   communications; this can lead to performance issues being amplified
   on mobile networks.  The use of encryption on networks will continue
   to increase, and with this understanding the workshop aimed to
   understand how we can solve the issues of bandwidth optimization and
   performance on radio networks in this encrypted world.

1.1.  Understanding "Bandwidth Optimization"

   For the purposes of this workshop, bandwidth optimization encompasses
   a variety of technical topics related to traffic engineering,
   prioritisation, optimisation and efficiency enhancements.  It also
   encompasses user-related topics such as specific subscription or
   billing models, and may touch upon regulatory aspects or other issues
   relating to government-initiated regulatory concerns.

   The first category of bandwidth optimization includes:

   o  Caching

   o  Prioritisation of interactive traffic over background traffic

   o  Per-user bandwidth limit

   The second category of bandwidth optimization may depend on one or
   more of the first category optimization strategies, but may, in
   particular, also encompass business-related topics such as content
   delivery arrangements with content providers.

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   Finally, while not strictly speaking traffic management, some
   networks employ policy-based filtering (e.g., requested parental
   controls) and many networks support some form of legal interception
   functionality per applicable laws.

   Many of these functions can continue as they are performed today,
   even with encreased use of encryption.  Others are using methods
   which inspect parts of the communication that will be encrypted, and
   these functions will have to be done differently in an increasingly
   encrypted Internet.

1.2.  Topics

   The workshop aimed to answer questions including:

   o  Understanding the bandwidth optimization use cases particular to
      radio networks

   o  Understanding existing approaches and how these do not work with
      encrypted traffic

   o  Understanding reasons why the Internet has not standardised
      support for lawful intercept and why mobile networks have

   o  Determining how to match traffic types with bandwidth optimization

   o  Discussing minimal information to be shared to manage networks but
      ensure user security and privacy

   o  Developing new bandwidth optimization techniques and protocols
      within these new constraints

   o  Discussing the appropriate network layer(s) for each management

   o  Cooperative methods of bandwidth optimization and issues
      associated with these

   The further aim was to gather architectural and engineering guidance
   on future work in the bandwidth optimisation area based on the
   discussions around the proposed approaches.  The workshop also
   explored possible areas for standardization, e.g. new protocols that
   can aid bandwidth optimization whilst ensuring user security inline
   with new work in transport layer protocols.

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1.3.  Organization of this report

   This workshop report summarizes the contributions to and discussions
   at the workshop, organized by topic.  The workshop began with scene
   setting topics which covered the issues around deploying encryption,
   the increased need for privacy on the Internet and setting a clear
   understanding that ciphertext should remain unbroken.  Later sessions
   focused on key solution areas; these included evolution on the
   transport layer and sending data up or down the path.  A session on
   application layers and CDNs aimed to highlight both issues and
   solutions experienced on the application layer.  The workshop ended
   with a session dedicated to technical response to regulation with
   regards to encryption.  The contributing documents were split between
   identifying the issues experienced with encryption on radio networks
   and suggested solutions.  Of the solutions suggested some focused on
   transport evolution, some on trusted middleboxes and others on
   collaborative data exchange.  Solutions were discussed within the
   sessions.  All accepted position papers and detailed transcripts of
   discussion are available at [MARNEW].

   The outcomes of the workshop are discussed in Section 7 and 8, and
   discuss progress after the workshop toward each of the identified
   work items as of the time of publication of this report.

   Report readers should be reminded that this workshop did not aim to
   discuss regulation or legislation, although policy topics were
   mentioned in discussions from time to time.

1.4.  Use of Note Well and Chatham House Rule

   The workshop was conducted under the IETF [NOTE_WELL] with the
   exception of the "Technical Analysis and Response to Potential
   Regulatory Reaction" session which was conducted under

1.5.  IETF and GSMA

   The IETF and GSMA [GSMA] have different working practices, standards
   and processes.  IETF is an open organisation with community driven
   standards, with the key aim of functionality and security for the
   Internet's users, while the GSMA is membership based and serves the
   needs of its membership base, most of whom are mobile network

   Unlike IETF, GSMA makes few standards.  Within the telecommunications
   industry standards are set in various divergent groups depending on
   their purpose.  Perhaps of most relevance to the bandwidth
   optimisation topic here is the work of the 3rd Generation Partnership

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   Project (3GPP) [SDO_3GPP] which works on radio network and core
   network standards. 3GPP members include mobile operators and original
   equipment manufacturers.

   One of the 3GPP standards relevant to this workshop is PCC-QoS
   [PCC-QOS].  Traditionally mobile networks have managed different
   applications and services based on the resources available and
   priorities given; for instance, emergency services have a top
   priority, data has a lower priority and voice services are somewhere
   in-between. 3GPP defined the PCC-QoS mechanism to support this
   functionality, and this depends on unencrypted communications

2.  Scene Setting Sessions

   Scene setting sessions aimed to bring all attendees up to a basic
   understanding of the problem and the scope of the workshop.  There
   were three scene setting sessions: Scene Setting (defining scope),
   Encryption Deployment Considerations and Trust Models and User Choice

2.1.  Scene Setting

   The telecommunications industry and Internet standards community are
   extremely different in terms of ethos and practices.  Both groups
   drive technical standards in their domain and build technical
   solutions with some policy-driven use cases.  These technologies, use
   cases and technical implementations are different, and the motivators
   between the two industries are also diverse.

   To ensure all attendees were aligned with contributing to discussions
   and driving solutions this "Scene Setting" session worked on
   generating a clear scope with all attendees involved.  In short: it
   was agreed that ciphertext encrypted by one party and intended to be
   decrypted by a second party should not be decrypted by a third party
   in any solution, that the radio access network (RAN) does experience
   issues with increased encrypted traffic, that we need to understand
   what those problems are precisely and that our goal is to improve
   user experience on the Internet.  Proposing new technical solutions
   based on presumed future regulation was not in scope.  The full scope
   is given below.

2.1.1.  Scope

   The attendees identified and agreed the following scope:

   o  In discussion we should assume: No broken crypto, Ciphertext
      increasingly common, congestion does need to be controlled as do

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      other transport issues and Network management including efficient
      use of resources, in RAN and elsewhere, has to work

   o  How/why is RAN different for transport; help us understand the
      complexities of the RAN and how hard it is to manage and why those

   o  What are the precise problems caused by more ciphertext

   o  Identify players, in addition to end users, the resulting tensions
      and how ciphertext changes those

   o  Some solutions will be radically changed by ciphertext, it's ok to
      talk about that

   o  The best possible quality of experience for the end user is a goal

   o  Our aim for the next two days is to analyse the situation and
      identify specific achievable tasks that could be tackled in the
      IETF or GSMA (or elsewhere?) and that improve the Internet given
      the assumptions above

   o  We should not delve into:

      *  Ways of doing interception (legal or not), for the reasons
         described in [RFC2804]

      *  Unpredictable political actions.

2.1.2.  Encryption Statistics and Radio Access Network Differences

   Attendees were shown that encrypted content is reaching around 50%
   according to then-current statistics [STATE_BROWSER] and
   [STATE_SERVER].  The IAB is encouraging all IETF working groups to
   consider the effect encryption being "on by default" will have on new
   protocol work, and the IETF is also working on encryption at lower
   layers.  One recent example of this work is opportunistic TCP
   encryption within the [TCPINC] Working Group.  The aims of these work
   items are greater security and privacy for end users and their data.

   Telecommunications networks often contain middleboxes that operators
   have previously considered to be trusted, but qualifying trust is
   difficult and should not be assumed.  Some interesting use cases
   exist with these middleboxes, such as anti-spam and malware
   detection, but these need to be balanced against their ability to
   open up cracks in the network for attacks such as pervasive

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   When operators increase the number of radio access network cells
   ("Base Stations"), this can improve the radio access network quality
   of service , but also adds to radio pollution.  This is one example
   of the balancing act required when devising radio access network

2.2.  Encryption Deployment Considerations

   Encryption across the Internet is on the rise.  However, some
   organisations and individuals come across a common set of operational
   issues when deploying encryption, mainly driven by commercial
   perspectives.  The [UBIQUITOUS] draft explains these network
   management function impacts, detailing areas around incident
   monitoring, access control management, and regulation on mobile
   networks.  The data was collected from various Internet players,
   including system and network administrators across enterprise,
   governmental organisations and personal use.  The aim of the document
   is to gain an understanding of what is needed for technical solutions
   to these issues, maintaining security and privacy for users.
   Attendees commented that worthwhile additions would be: different
   business environments (e.g. cloud environments) and service chaining.
   Incident monitoring in particular was noted as a difficult issue to
   solve given the use of URL in today's incident monitoring middleware.

   Some of these impacts to mobile networks can be resolved using
   difference methods and the [NETWORK_MANAGEMENT] draft details these
   methods.  The draft focuses heavily on methods to manage network
   traffic without breaching user privacy and security.

   By reviewing encryption depoyment issues and the alternative methods
   of network management MaRNEW attendees were made aware of the issues
   which affect radio networks, the deployment issues which are solvable
   and require no further action, and those which aren't currently
   solveable and which should be addressed within the workshop.

2.3.  Awareness of User Choice (Privacy)

   Some solutions intended to improve delivery of encrypted content
   could affect some or all of the privacy benefits that encryption
   provides.  Understanding user needs and desires for privacy is
   therefore important when designing these solutions.

   From a then-current study [Pew2014] 64% of users said concerns over
   privacy have increased, 67% of mobile Internet users would like to do
   more to protect their privacy.  The World Wide Web Consortium (W3C)
   and IETF have both responded to user desires for better privacy by
   recommending encryption for new protocols and web technologies.
   Within the W3C new security standards are emerging and the design

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   principles for HTML hold that users are the stakeholders with most
   priority, followed by implementors and other stakeholders, further
   enforcing the "user first" principle.  Users also have certain
   security expectations from particular contexts, and sometimes use new
   technologies to further protect their privacy even if those
   technologies weren't initially developed for that purpose.

   Operators may deploy technologies which can impact user privacy
   without being aware of those privacy implications or incorrectly
   assume that the benefits users gain from the new technology outweigh
   the loss of privacy.  If these technologies are necessary they should
   be opt-in.

   Internet stakeholders should understand the priority of other
   stakeholders.  Users should be considered the first priority.  Other
   stakeholders include implementors, developers, advertisers, operators
   and other ISPs.  Some technologies such as cookie use and JavaScript
   injection have been abused by these parties.  This has caused some
   developers to encrypt content to circumvent these technologies which
   are seen as intrusive or bad for user privacy.

   If users and content providers are to opt-in to network management
   services with negative privacy impacts, they should see clear value
   from using these services, and understand the impacts of using these
   services.  Users should also have easy abilities to opt-out.  Some
   users will always automatically click through consent requests, so
   any model relying on explicit consent is flawed for these users.
   Understanding the extent of "auto click through" may improve
   decisions about the use of consent requests in the future.  One model
   (Cooperative Traffic Management) works as an agent of the user; by
   opting-in metadata can be shared.  Issues with this involve trust
   only being applied at endpoints.

3.  Network or Transport Solution Sessions

   Network or Transport Solution Sessions aimed to discuss proposed
   solutions for managing encrypted traffic on radio access networks.
   Most solutions focus on metadata sharing, whether this sharing takes
   place from the endpoint to the network, from the network to the
   endpoint, or cooperatively in both directions.  Transport layer
   protocol evolution could be another approach to solve some of the
   issues radio access networks erience which cause them to rely on
   network management middleboxes.  By removing problems at the
   transport layer, reliance on expensive and complex middleboxes could

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3.1.  Sending Data Up / Down for Network Management Benefits

   Collaboration between network elements and endpoints could bring
   about better content distribution.  A number of suggestions were
   given; these included:

   o  Mobile Throughput Guidance [MTG]: exchanges metadata between
      network elements and endpoints via TCP Options.  It also allows
      for better understanding of how the transport protocol behaves and
      improving user experience further, although additional work on MTG
      is still required.

   o  SPUD [SPUD]: a UDP-based encapsulation protocol to allow explicit
      cooperation with middleboxes while using new, encrypted transport

   o  Network Status API: An API for operators to share congestion
      status or the state of a cell before an application starts sending
      data could allow applications to change their behaviour.

   o  Traffic classification: classifying traffic and adding these
      classifications as metadata for analysis throughout the network.
      This idea has trust and privacy implications.

   o  ConEx [CONEX]: a mechanism where senders inform the network about
      the congestion encountered by previous packets on the same flow,
      in-band at the IP layer.

   o  Latency versus Bandwidth: allowing the content provider to
      indicate whether higher bandwidth or lower latency is of greater
      priority and allowing the network to react based on that
      indication.  Where this bit resides in the protocol stack and how
      it is authenticated would need to be decided.

   o  No network management tools: disabling all network management
      tools from the network and rely only on end-to-end protocols to
      manage congestion.

   o  Fairness-aware Delay-controlled Controlled Delay (FD-CoDel)
      [FLOWQUEUE]: a hybrid packet scheduler/Active Queue Management
      (AQM, [RFC7567]) algorithm, aiming to reduce bufferbloat and
      latency.  FQ-CoDel manages packets from multiple flows and reduces
      the impact of head-of-line blocking from bursty traffic.

   Some of these suggestions rely on signaling from network elements to
   endpoint.  Others aim to create "hop-to-hop" solutions, which could
   be more aligned with how congestion is managed today, but with
   greater privacy implications.

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   Still others rely on signaling from endpoints to network elements.
   Some of these rely on implicit signaling, and others on explicit
   signaling.  Some workshop attendees agreed that relying on
   applications to explicitly declare the quality of service they
   require was not a good path forward, given the lack of success with
   this model in the past.

3.1.1.  Competition, Cooperation, and Mobile Network Complexities

   One of the larger issues in the sharing of data about the problems
   encountered with encrypted traffic in wireless networks is the matter
   of competition; network operators are reluctant to relinquish data
   about their own networks because it contains information that is
   valuable to competitors, and application providers wish to protect
   their users and reveal as little information as possible to the
   network.  Some people think that if middleboxes were authenticated
   and invoked explicitly, this would be an improvement over current
   transparent middleboxes that intercept traffic without endpoint
   consent.  Some workshop attendees suggested any exchange of
   information should be bidirectional, in an effort to improve
   cooperation between the elements.  A robust incentive framework could
   provide a solution to these issues, or at least help mitigate them.

   The radio access network is complex because it must deal with a
   number of conflicting demands.  Base stations reflect this
   environment, and information within these base stations can be of
   value to other entities on the path.  Some workshop participants
   thought solutions for managing congestion on radio networks should
   involve the base station if possible.  For instance, understanding
   how the Radio Resource Controller and AQM [RFC7567] interact (or
   don't interact) could provide valuable information for solving
   issues.  Although many workshop attendees agreed that even though
   there is a need to understand the base station, not all agreed that
   the base station should be part of a future solution.

   Some suggested solutions were based on network categorisation and on
   providing this information to the protocols or endpoints.  Completely
   categorising radio networks could be impossible due to their
   complexity, but categorising essential network properties could be
   possible and valuable.

4.  Transport Layer: Issues, Optimisation and Solutions

   TCP has been the dominant transport protocol since TCP/IP replaced
   the NCP Network Control Protocol on the Arpanet in March 1983.  TCP
   was originally devised to work on a specific network model that did
   not anticipate the high error rates and highly variable available
   bandwidth scenarios experienced on modern radio access networks.

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   Furthermore new network elements have been introduced (NATs and
   network devices with large buffers creating bufferbloat), and
   considerable peer-to-peer traffic is competing with traditional
   client-server traffic.  Consequently the transport layer today has
   requirements beyond what TCP was designed to meet.  TCP has other
   issues as well; too many services rely on TCP and only TCP, blocking
   deployment of new transport protocols like SCTP and DCCP.  This means
   that true innovation on the transport layer becomes difficult because
   deployment issues are more complicated than just building a new

   The IETF is trying to solve these issues through the IAB's "Stack
   Evolution" programme, and the first step in this programme is to
   collect data.  Network and content providers can provide data
   including: the cost of encryption, the advantages of network
   management tools, the deployment of protocols, and the effects when
   network management tools are disabled.  Network operators do not tend
   to reveal network information mostly for competitive reasons and so
   are unlikely to donate this information freely to IETF.  The GSMA is
   in a position to try to collect this data and anonymise it before
   bringing it to IETF which should alleviate the network operator
   worries but still provide IETF with some usable data.

   A considerable amount of work has already been done on TCP,
   especially innovation in bandwidth management and congestion control;
   although congestion is only detected when packet loss is encountered,
   and better methods based on detecting congestion would be beneficial.

   Furthermore, although the deficiencies of TCP are often considered as
   key issues in the evolution of the Internet protocol stack, the main
   route to resolve these issues may not be a new TCP, but an evolved
   stack.  Some workshop participants thought SPUD [SPUD] and ICN
   [RFC7476] are two suggestions which may help here.  QUIC [QUIC]
   engineers stated that the problems solved by QUIC are general
   problems, rather than TCP issues.  This view was not shared by all
   attendees of the workshop.  Moreover, TCP has had some improvements
   in the last few years which may mean some of the network lower layers
   should be investigated to see whether improvements can be made here.

5.  Application Layer Optimisation, Caching and CDNs

   Many discussions on the effects of encrypted traffic on radio access
   networks happen between implementers and the network operators; this
   session aimed to gather the opinions of the content and caching
   providers including their experiences running over mobile networks,
   the quality of experience their users expect, and what content and
   caching providers would like to achieve by working with or using the
   mobile network.

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   Content providers explained how even though this workshop cited
   encrypted data over radio access networks as the main issue, the real
   issue is network management generally, and all actors (applications
   providers, networks and devices) need to work together to overcome
   these general network management issues.  Content providers explained
   how they assume the mobile networks are standard compliant.  When the
   network is not standards compliant (e.g. using non-standards-
   compliant intermediaries) content providers can experience real costs
   as users contact their support centres to report issues which are
   difficult to test for and resolve.

   Content providers cited other common issues concerning data traffic
   over mobile networks.  Data subscription limits ("caps") cause issues
   for users; users are confused about how data caps work or are unsure
   how expensive media is and how much data it consumes.  Developers
   build products on networks not indicative of the networks their
   customers are using and not every organisation has the finances to
   build a caching infrastructure.

   Strongly related to content providers, content owners consider CDNs
   to be trusted deliverers of content and CDNs have shown great success
   in fixed networks.  Now that more traffic is moving to mobile
   networks there is a need to place caches at the edge of the mobile
   network, near the users.  Placing caches at the edge of the mobile
   network is a solution, but requires standards developed by content
   providers and mobile network operators.  The CNDi Working Group
   [CDNI] at IETF aims to allow global CDNs to interoperate with mobile
   CDNs; but this causes huge issues for the caching of encrypted data
   between these CDNs.  Some CDNs are experimenting with approaches like
   "Keyless SSL" [KeylessSSL] to enable safer storage of content without
   passing private keys to the CDN.  Blind Caching [BLIND_CACHING] is
   another proposal aimed at caching encrypted content closer to the
   user and managing the authentication at the original content provider

   At the end of the session each panelist was asked to identify one key
   collaborative work item.  Work items named were: evolving to cache
   encrypted content, using one-bit for latency / bandwidth trade-off
   (explained below), better collaboration between the network and
   application, better metrics to aid troubleshooting and innovation,
   and indications from the network to allow the application to adapt.

6.  Technical Analysis and Response to Potential Regulatory Reaction

   This session was conducted under Chatham House Rule.  The session
   aimed to discuss regulatory and political issues, but not their worth
   or need; rather to understand the laws that exist and how
   technologists can properly respond to these.

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   Mobile networks are regulated, compliance is mandatory (and non-
   compliance can result in service license revocation in some nations)
   and can incur costs on the mobile network operator.  Regulation does
   vary geographically.  Some regulations are court orders, others are
   self-imposed regulations, for example, "block lists" of websites such
   as the Internet Watch Foundation list [IWF].  Operators are not
   expected to decrypt sites, so those encrypted sites will not be
   blocked because of content.

   Parental control-type filters also exist on the network and are
   easily bypassed today, vastly limiting their effectiveness.  Better
   solutions would allow for users to easily set these restrictions
   themselves.  Other regulations are also hard to meet, such as user
   data patterns, or will become harder to collect - such as "Internet
   of Things" (IoT) cases.  Most attendees agreed that if a government
   cannot get information it needs and is legally entitled to have from
   network operators they will approach content providers.  Some
   governments are aware of the impact of encryption and are working
   with, or trying to work with, content providers.  The IAB has
   concluded blocking and filtering can be done at the endpoints of the

   Not all of these regulations apply to the Internet, and the Internet
   community is not always aware of their existence.  Collectively the
   Internet community can work with GSMA and 3GPP and act collectively
   to alleviate the risk imposed by encrypted traffic.  Some
   participants expressed concern that governments might require
   operators to provide information that they no longer have the ability
   to provide, because previously-unencrypted traffic is now being
   encrypted, and this might expose operators to new liability, but no
   specific examples were given during the workshop.  A suggestion from
   some attendees was that if any new technical solutions are necessary,
   they should easily be "switched off".

   Some mobile network operators are producing transparency reports
   covering regulations including lawful intercept.  Operators who have
   done this already are encouraging others to do the same.

7.  Suggested Principles and Solutions

   Based on the talks and discussions throughout the workshop a set of
   suggested principles and solutions has been collected.  This is not
   an exhaustive list, and no attempt was made to come to consensus
   during the workshop, so there are likely at least some participants
   who would not agree with any particular principle listed below.  The
   list is a union of participant thinking, not an intersection.

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   o  Encrypted Traffic: any solution should encourage and support
      encrypted traffic.

   o  Flexibility: radio access network qualities vary vastly and the
      network needs of content can differ significantly, so any new
      solution should be flexible across either the network type,
      content type, or both.

   o  Privacy: new solutions should not introduce new ways where
      information can be discovered and attributed to individual users.

   o  Minimum data only for collaborative work: user data, application
      data, and network data all needs protection, so new solutions
      should use the minimum information to make a working solution.

   A collection of solutions suggested by various participants during
   the workshop is given below.  Inclusion in this list does not imply
   that other workshop participants agreed.  Again, the list is a union
   of proposed solutions, not an intersection.

   o  Evolving TCP or evolution on the transport layer: this could take
      a number of forms and some of this work is already underway within
      the IETF.

   o  Congestion Control: many attendees cited congestion control as a
      key issue.  Further analysis, investigation and work could be done
      in this space.

   o  SPROUT: research at MIT which is a transport protocol for
      applications that desire high throughput and low delay.  [SPROUT]

   o  PCC: Performance-oriented Congestion Control: is a new
      architecture that aims for consistent high performance even in
      challenging scenarios.  PCC endpoints observe the connection
      between their actions and their known performance, which allows
      them to adapt their actions.  [PCC]

   o  CDNs and Caches: placing caches closer to the edge of the radio
      network, as close as possible to the mobile user, or making more
      intelligent CDNs would result in faster content delivery and less
      strain on the network.

   o  Blind Caching: a proposal for caching of encrypted content

   o  CDN improvements: including keyless SSL and better CDN placement.

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   o  Mobile Throughput Guidance: a mechanism and protocol elements that
      allow the cellular network to provide near real-time information
      on capacity available to the TCP server.  [MTG]

   o  One bit for latency / bandwidth trade-off: determining whether
      using a single bit in an unencrypted transport header to
      distinguish between traffic that the sender prefers to be queued
      and traffic that the sender would prefer to drop rather than delay
      provides additional benefits beyond what can be achieved without
      this signaling.

   o  Base Station: some suggestions involved "using the Base Station",
      but this was not defined in detail.  The Base Station holds the
      Radio Resource Controller and scheduler which could provide a
      place to host solutions, or data from the Base Station could help
      in devising new solutions.

   o  Identify traffic types via 5-tuple: information from the 5-tuple
      could provide understanding of the traffic type, and network
      management appropriate for that traffic type could then be

   o  Heuristics: Networks can sometimes identify traffic types by
      observing characteristics such as data flow rate and then apply
      network management to these identified flows.  This is not
      recommended as categorisations can be incorrect.

   o  APIs: An API for operators to share congestion status or the state
      of a cell before an application starts sending data could allow
      applications to change their behaviour.  Alternatively an API
      could provide the network with information on the data type,
      allowing appropriate network management for that data type,
      although this method exposes privacy issues.

   o  Standard approach for operator to offer services to Content
      Providers: mobile network operators could provide caching services
      or other services for content providers to use for faster and
      smoother content delivery.

   o  AQM [RFC7567] and ECN [RFC3168] deployments: queuing and
      congestion management methods have existed for some time in the
      form of AQM, ECN and others which can help the transport and
      Internet protocol layers adapt to congestion faster.

   o  Trust Model or Trust Framework: some solutions in this area (e.g.
      SPUD) have a reliance on trust when content providers or the
      network are being asked to add classifiers to their traffic.

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   o  Keyless SSL [KeylessSSL]: allows content providers to maintain
      their private keys on a "key server" and host the content
      elsewhere (e.g. on a CDN).  This could become standardised in
      IETF.  [LURK]

   o  Meaningful capacity sharing: including the ConEx [CONEX] work
      which exposes information about congestion to the network nodes.

   o  Hop-by-hop: some suggestions offer hop-by-hop methods allowing
      nodes to adapt flow given the qualities of the networks around
      them and the congestion they are experiencing.

   o  Metrics and metric standards: in order to evolve current protocols
      to be best suited to today's networks, data is needed about
      current network conditions, protocol deployments, packet traces
      and middlebox behaviour.  Beyond this, proper testing and
      debugging on networks could provide great insight for stack

   o  5G: Mobile operator standards bodies are in the process of setting
      the requirements for 5G.  Requirements for network management
      could be added.

   In the workshop, attendees identified other areas where greater
   understanding could help the standards process.  These were
   identified as:

   o  Greater understanding of the RAN at IETF.

   o  Reviews and comments on 3GPP perspective.

   o  How to do congestion control in the RAN.

7.1.  Better Collaboration

   Throughout the workshop attendees placed emphasis on the need for
   better collaboration between the IETF and telecommunications bodies
   and organisations.  The workshop was one such way to achieve this,
   but the good work and relationships built in the workshop should
   continue so the two groups can work on solutions which are better for
   both technologies and users.

8.  Since MaRNEW

   Since MaRNEW a number of activities have taken place in various IETF
   working groups, and in groups external to IETF.  The ACCORD BoF was
   held at IETF 95 in November 2015, which brought the workshop
   discussion to the wider IETF audiences by providing an account of the

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   discussions that had taken place within the workshop and highlighting
   key areas to progress on.  Key areas to progress and an update on
   their current status follows:

   o  The collection of useable metrics and data were requested by a
      number of MaRNEW attendees, especially for use within the IRTF
      Measurement and Analysis for Protocols (MAP) Research Group; this
      data has been difficult to collect due to the closed nature of
      mobile network operators.

   o  Understanding impediments to protocol stack evolution has
      continued within the IAB's Stack Evolution programme and
      throughout transport-related IETF working groups such as the
      Transport Area Working Group (TSVWG).

   o  The Mobile Throughput Guidance draft has entered into a testing
      and data collection phase; although further advancements in
      transport technologies (among others, QUIC) may have stalled
      efforts in TCP-related proposals.

   o  Work on proposals for caching encrypted content continue, albeit
      with some security flaws which proponents are working on further
      proposals to fix.  Most often these are discussed within the IETF
      HTTPbis working group.

   o  The PLUS BOF at IETF 96 in July 2016 did not result in the
      formation of a working group, with attendees expressing concern on
      the privacy issues associated with the data sharing possibilities
      of the shim layer proposed.

   o  The LURK BOF at IETF 96 in July 2016 did not result in the
      formation of a working group, because the BOF identified more
      problems with the presumed approach than anticipated.

   The most rewarding output of MaRNEW is perhaps the most intangible.
   MaRNEW gave two rather divergent industry groups the opportunity to
   connect and discuss common technologies and issues affecting users
   and operations.  Mobile Network providers and key Internet engineers
   and experts have developed a greater collaborative relationship to
   aid development of further standards which work across networks in a
   secure manner.

9.  Security Considerations

   This document is an IAB report from a workshop on interactions
   between network security, especially privacy, and network

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   It does not affect the security of the Internet, taken on its own.

10.  IANA Considerations

   This document makes no requests of IANA.

11.  Acknowledgements

   Stephen Farrell reviewed this report in draft form and provided
   copious comments and suggestions.

   Barry Leiba provided some clarifications on specific discussions
   about Lawful Intercept that took place during the workshop.

   Bob Hinden and Warren Kumari provided comments and suggestions during
   the IAB Call for Comments.

   Amelia Andersdotter and Shivan Kaul Sahib provided comments from the
   Human Rights Review Team during the IAB Call for Comments.

12.  Informative References

              Holmberg, M., "Caching Secure HTTP Content using Blind
              Caches", October 2016, <

   [CDNI]     "Content Delivery Networks Interconnection Working Group",
              n.d., <>.

              "Chatham House Rule", n.d.,

   [CONEX]    "Congestion Exposure Working Group", n.d.,

              Patel, C., "The effect of encrypted traffic on the QoS
              mechanisms in cellular networks", August 2015,

              Dumazet, P., "FlowQueue-Codel", March 2014,

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   [GSMA]     "GSMA Homepage", n.d., <>.

   [IWF]      "Internet Watch Foundation", n.d.,

              Sullivan, N., "Keyless SSL: The Nitty Gritty Technical
              Details", September 2014, <

   [LURK]     Ma, D., "TLS/DTLS Content Provider Edge Server Split Use
              Case", January 2016, <

   [MARNEW]   "MaRNEW Workshop IAB Homepage", n.d.,

   [MTG]      Smith, A., "Mobile Throughput Guidance Inband Signaling
              Protocol", September 2015,

              Smith, K., "Network management of encrypted traffic", May
              2015, <

              "IETF Note Well", n.d., <

   [PCC]      Schapira, M., "PCC, Re-architecting Congestion Control for
              Consistent High Performance", May 2015,

   [PCC-QOS]  "Policy and charging control signalling flows and Quality
              of Service (QoS) parameter mapping", March 2016,

   [Pew2014]  "Public Perceptions of Privacy and Security in the Post-
              Snowden Era", November 2014,

   [QUIC]     Swett, J., "QUIC, A UDP-Based Secure and Reliable
              Transport for HTTP/2", June 2015,

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   [RFC2804]  IAB and IESG, "IETF Policy on Wiretapping", RFC 2804,
              DOI 10.17487/RFC2804, May 2000, <https://www.rfc-

   [RFC3168]  Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
              of Explicit Congestion Notification (ECN) to IP",
              RFC 3168, DOI 10.17487/RFC3168, September 2001,

   [RFC7476]  Pentikousis, K., Ed., Ohlman, B., Corujo, D., Boggia, G.,
              Tyson, G., Davies, E., Molinaro, A., and S. Eum,
              "Information-Centric Networking: Baseline Scenarios",
              RFC 7476, DOI 10.17487/RFC7476, March 2015,

   [RFC7567]  Baker, F., Ed. and G. Fairhurst, Ed., "IETF
              Recommendations Regarding Active Queue Management",
              BCP 197, RFC 7567, DOI 10.17487/RFC7567, July 2015,

              "3GPP Homepage", n.d., <>.

   [SPROUT]   Balakrishnan, K., "Stochastic Forecasts Achieve High
              Throughput and Low Delay over Cellular Networks", April

   [SPUD]     "Session Protocol for User Datagrams", n.d.,

              Barnes, R., "Some observations of TLS in the web", July
              2015, <

              Salz, R., "Some observations of TLS in the web", July
              2015, <

   [TCPINC]   "TCP Increased Security Working Group", n.d.,

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              Morton, K., "Effect of Ubiquitous Encryption", March 2015,

Appendix A.  Workshop Attendees

   o  Rich Salz, Akamai

   o  Aaron Falk, Akamai

   o  Vinay Kanitkar, Akamai

   o  Julien Maisonneuve, Alcatel Lucent

   o  Dan Druta, AT&T

   o  Humberto La Roche, Cisco

   o  Thomas Anderson, Cisco

   o  Paul Polakos, Cisco

   o  Marcus Ihlar, Ericsson

   o  Szilveszter Nadas, Ericsson

   o  John Mattsson, Ericsson

   o  Salvatore Loreto, Ericsson

   o  Blake Matheny, Facebook

   o  Andreas Terzis, Google

   o  Jana Iyengar, Google

   o  Natasha Rooney, GSMA

   o  Istvan Lajtos, GSMA

   o  Emma Wood, GSMA

   o  Jianjie You, Huawei

   o  Chunshan Xiong, Huawei

   o  Russ Housley, IAB

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   o  Mary Barnes, IAB

   o  Joe Hildebrand, IAB / Cisco

   o  Ted Hardie, IAB / Google

   o  Robert Sparks, IAB / Oracle

   o  Spencer Dawkins, IETF AD

   o  Benoit Claise, IETF AD / Cisco

   o  Kathleen Moriarty, IETF AD / EMC

   o  Barry Leiba, IETF AD / Huawei

   o  Ben Campbell, IETF AD / Oracle

   o  Stephen Farrell, IETF AD / Trinity College Dublin

   o  Jari Arkko, IETF Chair / Ericsson

   o  Karen O'Donoghue, ISOC

   o  Phil Roberts, ISOC

   o  Olaf Kolkman, ISOC

   o  Christian Huitema, Microsoft

   o  Patrick McManus, Mozilla

   o  Dirk Kutscher, NEC Europe Network Laboratories

   o  Mark Watson, Netflix

   o  Martin Peylo, Nokia

   o  Mohammed Dadas, Orange

   o  Diego Lopez, Telefonica

   o  Matteo Varvello, Telefonica

   o  Zubair Shafiq, The University of Iowa

   o  Vijay Devarapalli, Vasona Networks

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   o  Sanjay Mishra, Verizon

   o  Gianpaolo Scassellati, Vimplecom

   o  Kevin Smith, Vodafone

   o  Wendy Seltzer, W3C

Appendix B.  Workshop Position Papers

   o  Mohammed Dadas, Emile Stephan, Mathilde Cayla, Iuniana Oprescu,
      "Cooperation Framework between Application layer and Lower Layers"

   o  Julien Maisonneuve, Thomas Fossati and Vijay Gurbani, "The
      security pendulum and the network" at

   o  Martin Peylo, "Enabling Secure QoE Measures for Internet
      Applications over Radio Networks is a MUST" at

   o  Vijay Devarapalli, "The bandwidth balancing act: Managing QoE as
      encrypted services change the traffic optimization game" at

   o  Humberto La Roche, "Use Cases for Communicating End-Points in
      Mobile Network Middle-Boxes" at

   o  Richard Barnes and Patrick McManus, "User Consent and Security as
      a Public Good" at

   o  Iuniana Oprescu, Jon Peterson and Natasha Rooney, "A Framework for
      Consent and Permissions in Mediating TLS" at

   o  Jari Arkko and Goeran Eriksson, "Characteristics of Traffic Type
      Changes and Their Architectural Implications" at

   o  Szilveszter Nadas and Attila Mihaly, "Traffic Management for
      Encrypted Traffic focusing on Cellular Networks" at

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   o  Gianpaolo Scassellati, "Vimpelcom Position Paper for MaRNEW
      Meeting" at

   o  Mirja Kuehlewind, Dirk Kutscher and Brian Trammell, "Enabling
      Traffic Management without DPI" at

   o  Andreas Terzis and Chris Bentzel, "Sharing network state with
      application endpoints" at

   o  Marcus Ihlar, Robert Skog and Salvatore Loreto, "The needed
      existence of Performance Enhancing Proxies in an Encrypted World"

   o  John Mattsson, "Network Operation in an All-Encrypted World" at

   o  Dirk Kutscher, Giovanna Carofiglio, Luca Muscariello and Paul
      Polakos, "Maintaining Efficiency and Privacy in Mobile Networks
      through Information-Centric Networking" at

   o  Chunshan Xiong and Milan Patel, "The effect of encrypted traffic
      on the QoS mechanisms in cellular networks" at

   o  Thomas Anderson, Peter Bosch and Alessandro Duminuco, "Bandwidth
      Control and Regulation in Mobile Networks via SDN/NFV-Based
      Platforms" at

   o  Karen O'Donoghue and Phil Roberts, Barriers to Deployment:
      "Probing the Potential Differences in Developed and Developing
      Infrastructure" at

   o  Wendy Seltzer, "Performance, Security, and Privacy Considerations
      for the Mobile Web" at

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   o  Jianjie You, Hanyu Wei and Huaru Yang, "Use Case Analysis and
      Potential Bandwidth Optimization Methods for Encrypted Traffic" at

   o  Mangesh Kasbekar and Vinay Kanitkar, "CDNs, Network Services and
      Encrypted Traffic" at

   o  Claude Rocray, Mark Santelli and Yves Hupe, "Providing
      Optimization of Encrypted HTTP Traffic" at

   o  Zubair Shafiq, "Tracking Mobile Video QoE in the Encrypted
      Internet" at

   o  Kevin Smith, "Encryption and government regulation: what happens
      now?" at

Authors' Addresses

   Natasha Rooney


   Spencer Dawkins (editor)
   Wonder Hamster


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