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Effect of Pervasive Encryption on Operators

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 8404.
Authors Kathleen Moriarty , Al Morton
Last updated 2017-06-07 (Latest revision 2017-04-13)
RFC stream Internet Engineering Task Force (IETF)
Stream WG state (None)
Document shepherd Paul E. Hoffman
Shepherd write-up Show Last changed 2017-02-15
IESG IESG state Became RFC 8404 (Informational)
Consensus boilerplate Yes
Telechat date (None)
Responsible AD Warren "Ace" Kumari
Send notices to "Paul Hoffman" <>,
IANA IANA review state IANA OK - No Actions Needed
Network Working Group                                        K. Moriarty
Internet-Draft                                                  Dell EMC
Intended status: Informational                                 A. Morton
Expires: October 15, 2017                                      AT&T Labs
                                                          April 13, 2017

              Effect of Pervasive Encryption on Operators


   Pervasive Monitoring (PM) attacks on the privacy of Internet users is
   of serious concern to both the user and operator community.  RFC7258
   discussed the critical need to protect users' privacy when developing
   IETF specifications and also recognized making networks unmanageable
   to mitigate PM is not an acceptable outcome, an appropriate balance
   is needed.  This document discusses current security and network
   management practices that may be impacted by the shift to increased
   use of encryption to help guide protocol development in support of
   manageable, secure networks.

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at

   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 15, 2017.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   ( in effect on the date of
   publication of this document.  Please review these documents

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   carefully, as they describe your rights and restrictions with respect
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Additional Background on Encryption Changes . . . . . . .   4
   2.  Network Service Provider Monitoring . . . . . . . . . . . . .   6
     2.1.  Load Balancers  . . . . . . . . . . . . . . . . . . . . .   7
     2.2.  Traffic Surveys/Monitoring  . . . . . . . . . . . . . . .   9
     2.3.  Monitoring Approaches Used by Middleboxes . . . . . . . .   9
       2.3.1.  Traffic Analysis Fingerprinting . . . . . . . . . . .   9
       2.3.2.  Deep Packet Inspection (DPI)  . . . . . . . . . . . .  10
     2.4.  Connection to Proxy for Compression . . . . . . . . . . .  11
     2.5.  Content Filtering . . . . . . . . . . . . . . . . . . . .  11
       2.5.1.  Mobility Middlebox Content Filtering  . . . . . . . .  11
       2.5.2.  Parental Controls . . . . . . . . . . . . . . . . . .  12
       2.5.3.  HTTP Redirection  . . . . . . . . . . . . . . . . . .  12
     2.6.  Access and Policy Enforcement . . . . . . . . . . . . . .  13
       2.6.1.  Server load balancing . . . . . . . . . . . . . . . .  13
       2.6.2.  Network Access  . . . . . . . . . . . . . . . . . . .  13
       2.6.3.  Regulation and policy enforcement . . . . . . . . . .  13
       2.6.4.  Application Layer Gateways  . . . . . . . . . . . . .  14
       2.6.5.  HTTP Header Insertion . . . . . . . . . . . . . . . .  14
     2.7.  Network Monitoring for Performance Management and
           Troubleshooting . . . . . . . . . . . . . . . . . . . . .  14
   3.  Encryption in Hosting SP Environments . . . . . . . . . . . .  16
     3.1.  Management Access Security  . . . . . . . . . . . . . . .  16
       3.1.1.  Customer Access Monitoring  . . . . . . . . . . . . .  17
       3.1.2.  SP Content Monitoring of Applications . . . . . . . .  18
     3.2.  Hosted Applications . . . . . . . . . . . . . . . . . . .  19
       3.2.1.  Monitoring Managed Applications . . . . . . . . . . .  20
       3.2.2.  Mail Service Providers  . . . . . . . . . . . . . . .  20
     3.3.  Data Storage  . . . . . . . . . . . . . . . . . . . . . .  21
       3.3.1.  Host-level Encryption . . . . . . . . . . . . . . . .  21
       3.3.2.  Disk Encryption, Data at Rest . . . . . . . . . . . .  22
       3.3.3.  Cross Data Center Replication Services  . . . . . . .  22
   4.  Encryption for Enterprises  . . . . . . . . . . . . . . . . .  23
     4.1.  Monitoring Practices of the Enterprise  . . . . . . . . .  23
       4.1.1.  Security Monitoring in the Enterprise . . . . . . . .  23
       4.1.2.  Application Performance Monitoring in the Enterprise   24
       4.1.3.  Enterprise Network Diagnostics and Troubleshooting  .  25
     4.2.  Techniques for Monitoring Internet Session Traffic  . . .  27
   5.  Security Monitoring for Specific Attack Types . . . . . . . .  28
     5.1.  Mail Abuse and SPAM . . . . . . . . . . . . . . . . . . .  28

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     5.2.  Denial of Service . . . . . . . . . . . . . . . . . . . .  29
     5.3.  Phishing  . . . . . . . . . . . . . . . . . . . . . . . .  29
     5.4.  Botnets . . . . . . . . . . . . . . . . . . . . . . . . .  30
     5.5.  Malware . . . . . . . . . . . . . . . . . . . . . . . . .  30
     5.6.  Spoofed Source IP Address Protection  . . . . . . . . . .  31
     5.7.  Further work  . . . . . . . . . . . . . . . . . . . . . .  31
   6.  Application-based Flow Information Visible to a Network . . .  31
     6.1.  TLS Server Name Indication  . . . . . . . . . . . . . . .  31
     6.2.  Application Layer Protocol Negotiation (ALPN) . . . . . .  32
     6.3.  Content Length, BitRate and Pacing  . . . . . . . . . . .  32
   7.  Impact on Mobility Network Optimizations and New Services . .  32
     7.1.  Effect of Encypted ACKs . . . . . . . . . . . . . . . . .  33
     7.2.  Effect of Encrypted Transport Headers . . . . . . . . . .  34
     7.3.  Effect of Encryption on New or Emerging Services  . . . .  34
     7.4.  Effect of Encryption on Mobile Network Evolution  . . . .  35
   8.  Response to Increased Encryption and Looking Forward  . . . .  36
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  37
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  37
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  37
   12. Informative References  . . . . . . . . . . . . . . . . . . .  37
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  43

1.  Introduction

   In response to pervasive monitoring revelations and the IETF
   consensus that Pervasive Monitoring is an Attack [RFC7258], efforts
   are underway to improve and increase encryption of Internet traffic.
   Pervasive Monitoring (PM) attacks on the privacy of Internet users is
   of serious concern to both the user and operator community.  RFC7258
   discussed the critical need to protect users' privacy when developing
   IETF specifications and also recognized making networks unmanageable
   to mitigate PM is not an acceptable outcome, an appropriate balance
   is needed.  This document discusses current security and network
   management practices that may be impacted by the shift to increased
   use of encryption to help guide protocol development in support of
   manageable, secure networks.

   Traditional network management, planning, security operations, and
   performance optimization have been developed in an Internet where
   data traffic flows without encryption.  While this has provided
   information which aids operations and support troubleshooting at all
   layers, it has also made pervasive monitoring by unseen parties
   possible.  With broad support and increased awareness of the need to
   consider privacy in all aspects across the Internet, it is important
   to catalog existing standard functions around network management,
   security and troubleshooting that have depended upon the availability
   of open information to function.

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   The important transformation to an Internet with pervasive
   encryption, while necessary and beneficial to the end user, will
   result in new challenges to adequately meet the goals of network
   management, planning, security operations, and performance
   optimization.  This document describes existing practices and
   potential impact from pervasive encryption with the expectation that
   this will motivate the technical innovation and necessary changes.
   Understanding of the goals of current practices and the potential
   impact is provided to encourage the cross-industry and cross-layer
   work needed to support the ongoing evolution towards a functional
   Internet with pervasive encryption.

   The IETF reiterates its view that pervasive monitoring is an attack
   and that the world is moving towards ubiquitous encryption [RFC7258].
   The document aims to help IETF participants understand the impact of
   pervasive encryption, both opportunistic and strong end-to-end
   encryption, on operational practices.  This will help inform future
   protocol development to ensure that operator impact is part of the
   conversation.  This document does not endorse such current practices.
   It opens the door to conversation to develop new methods when
   possible to achieve the same goals (better performance and
   reliability for customers, or monitoring services that have been
   requested such as web content and DLP).  The document includes a
   sampling of contributions and does not attempt to describe every
   nuance as some sections cover technologies used that include a broad
   spectrum of devices and use cases.

   Adapting to an Internet with more and/or stronger session encryption
   likely results in alternate solutions being employed at the endpoint
   and working within the bounds provided by encrypted streams.
   Operators are often at the front line for user complaints on problems
   such as performance due to occasional network problems or events such
   as Distributed Denial of Service (DDoS) attacks and congestion.
   Operators are also concerned with both their need for privacy and the
   needs of privacy for their customers.  As such, the impact to
   operators is described to understand their challenges and determine
   if other measures appropriate for IETF protocols can be employed,
   e.g.  increased logging capabilities.  This shift in operational
   practices is considered an impact, which is important to understand
   when reading that term within this document.

1.1.  Additional Background on Encryption Changes

   Session encryption helps to prevent both passive and active attacks
   on transport protocols; more on pervasive monitoring can be found in
   the Confidentiality in the Face of Pervasive Surveillance: A Threat
   Model and Problem Statement [RFC7624].  The Internet Architecture
   Board (IAB) released a statement advocating for increased use of

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   encryption in November 2014.  Views on acceptable encryption have
   also shifted and are documented in "Opportunistic Security" (OS)
   [RFC7435], where cleartext sessions should be upgraded to
   unauthenticated session encryption, rather than no encryption.  OS
   encourages upgrading from cleartext, but cannot require or guarantee
   such upgrades.  Once OS is used, it allows for an evolution to
   authenticated encryption.  These efforts are necessary to improve end
   user's expectation of privacy, making pervasive monitoring cost
   prohibitive.  Active attacks are still possible on sessions where
   unauthenticated sessions are in use.  The push for ubiquitous
   encryption via OS is specific to improving privacy for everyday users
   of the Internet.

   Although there is a push for OS, there is also work being done to
   improve implementation development and configuration flaws of TLS and
   DTLS sessions to prevent active attacks used to monitor or intercept
   session data.  The (UTA) working group is in process of publishing
   documentation to improve the security of TLS and DTLS sessions.  They
   have documented the known attack vectors in [RFC7457] and have
   documented Best Practices for TLS and DTLS in [RFC7525] and have
   other documents in the queue.

   Estimates for session encryption from spring 2015 approximate that
   about 30% of web sites have session encryption enabled, according to
   the Electronic Frontier Foundation [EFF].  Mozilla maintains
   statistics on TLS usage and as of March 2017, 54% of HTTP base page
   loads are encrypted.  The statistic from Mozilla varies when filters
   are applied for platform and browser versions.  Enterprise networks
   such as EMC, now Dell EMC, observed that about 78% of outbound
   employee traffic was encrypted in June 2014.  Although the actual
   number of sites may only be around 30%, they include some of the most
   visited sites on the Internet for corporate users.

   In addition to encrypted web site access (HTTP over TLS), there are
   other well-deployed application level transport encryption efforts
   such as mail transfer agent (MTA)-to-MTA session encryption transport
   for email (SMTP over TLS) and gateway-to-gateway for instant
   messaging (XMPP over TLS).  Although this does provide protection
   from transport layer attacks, the servers could be a point of
   vulnerability if user-to-user encryption is not provided for these
   messaging protocols.  User-to-user content encryption schemes, such
   as S/MIME and PGP for email and encryption (e.g.  Off-the-Record
   (OTR)) for Extensible Messaging and Presence Protocol (XMPP) are used
   by those interested to protect their data as it crosses intermediary
   servers, preventing the vulnerability described by providing an end-
   to-end solution.  User-to-user schemes are under review and
   additional options will emerge to ease the configuration

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   requirements, making this type of option more accessible to non-
   technical users interested in protecting their privacy.

   Increased use of encryption (either opportunistic or authenticated)
   will impact operations for security and network management, causing a
   shift in how these functions are performed.  In some cases new
   methods to monitor and protect data will evolve, for other cases the
   capability may be eliminated.  This draft includes a collection of
   current security and network management functions that may be
   impacted by this shift to increased use of encryption.  This draft
   does not attempt to solve these problems, but rather document the
   current state to assist in the development of alternate options to
   achieve the intended purpose of the documented practices.

   In this document we consider several different forms of service
   providers, so we distinguish between them with adjectives.  For
   example, network service providers (or network operators) provide IP-
   packet transport primarily, though they may bundle other services
   with packet transport.  Alternatively, application service providers
   primarily offer systems that participate as an end-point in
   communications with the application user, and hosting service
   providers lease computing, storage, and communications systems in
   datacenters.  In practice, many companies perform two or more service
   provider roles, but may be historically associated with one.

2.  Network Service Provider Monitoring

   Network Service Providers (SP) are responding to encryption on the
   Internet, some helping to increase the use of encryption and others
   preventing its use.  Network SPs for this definition include the
   backbone Internet Service providers as well as those providing
   infrastructure at scale for core Internet use (hosted infrastructure
   and services such as email).

   Following the Snowden revelations, application service providers
   responded by encrypting traffic between their data centers to prevent
   passive monitoring from taking place unbeknownst to them (Yahoo,
   Google, etc.).  Large mail service providers also began to encrypt
   session transport to hosted mail services.  This had an immediate
   impact to help protect the privacy of users' data, but created a
   problem for some network operators.  They could no longer gain access
   to session streams resulting in actions by several to regain their
   operational practices that previously depended on cleartext data

   The EFF reported [EFF2014] several network service providers taking
   steps to prevent the use of SMTP over TLS by breaking STARTTLS
   (section 3.2 of [RFC7525]), essentially preventing the negotiation

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   process resulting in fallback to the use of clear text.  Some
   methods, used by service providers are impacted by the use of
   encryption where middle boxes were in use to perform functions that
   range from load balancing techniques to monitoring for attacks or
   enabling "lawful intercept", such that described in [ETSI101331] in
   the US.  Only methods keeping with the goal of balancing network
   management and PM mitigation in [RFC7258] should be considered in
   solution work resulting from this document.

   Network service providers use various monitoring techniques for
   security and operational purposes.  The following subsections detail
   the purpose of each type of monitoring and what protocol fields are
   used to accomplish the task.  The loss of access to these fields, has
   in some cases, prompted undesirable security practices in order to
   gain access to the fields in unencrypted data flows.  Ideally,
   through discussions resulting from documenting these practices, new
   methods could be developed to accomplish network management goals
   without the ability to see session data.

2.1.  Load Balancers

   A standalone load balancer is something one can take off the shelf,
   place in front of a pool of servers, and with an appropriate
   configuration, it will load balance the traffic.  This is a typical
   setup that one thinks of when they think of load balancer
   middleboxes.  Standalone load balancers can only rely on the plainly
   observable information in the packets they are forwarding and can
   only rely on the industry-accepted standards in interpreting the
   plainly observable information.  Typically, this is a 5-tuple of the

   An integrated load balancer is developed to be an integral part of
   the service provided by the server pool behind that load balancer.
   These load balancers can communicate state with their pool of servers
   to better route flows to the appropriate servers.  They can rely on
   non-standard system-specific information and operational knowledge
   shared between the load balancer and its servers.

   Both standalone and integrated load balancers can be deployed in
   pools for redundancy and load sharing.  For high availability, it is
   important that when packets belonging to a flow start to arrive at a
   different load balancer in the load balancer pool, the packets
   continue to be forwarded to the original server in the server pool.
   The importance of this requirement increases as the chances of such
   load balancer change event increases.

   With the proliferation of mobile connected devices, there is an acute
   need for connection-oriented protocols that maintain connections

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   after a network migration by an endpoint.  This connection
   persistence provides an additional challenge for multi-homed anycast-
   based services typically employed by large content owners and Content
   Distribution Networks (CDNs).  The challenge is that a migration to a
   different network in the middle of the connection greatly increases
   the chances of the packets routed to a different anycast pop due to
   the new network's different connectivity and Internet peering
   arrangements.  The load balancer in the new pop, potentially
   thousands of miles away, will not have information about the new flow
   and would not be able to route it back to the original pop.

   To help with the endpoint network migration challenges, anycast
   service operations are likely to employ integrated load balancers
   that, in cooperation with their pool servers, are able to ensure that
   client-to-server packets contain some additional identification in
   plainly-observable parts of the packets (in addition to the 5-tuple).
   As noted in Section 2 of [RFC7258], careful consideration in protocol
   design to mitigate PM is important, while ensuring manageability of
   the network.

   Some integrated load balancers utilize the ability to have additional
   plainly observable information even for today's protocols that are
   not network migration tolerant.  This additional information bestows
   the advantage in additional availability and scalability to such load
   balancers.  For example, BGP reconvergence can cause a flow to switch
   anycast pops even without a network change by any endpoint.
   Additionally, a system that is able to encode the identity of the
   pool server in plain text information available in each incoming
   packet is able to provide stateless load balancing.  This ability
   confers great reliability and scalability advantages even if the flow
   remains in a single pop.  Indeed, a stateless load balancing system
   is not required to keep state of each flow.  Even more importantly,
   it is not required to continuously sync such state among the pool of
   load balancers.

   Current protocols, such as TCP, allow the development of stateless
   integrated load balancers by availing such load balancers of
   additional plain text information in client-to-server packets.  (In
   case of TCP, such information can be encoded by having server-
   generated sequence numbers, mss values, lengths of the packet sent,

   In future Network Function Virtualization (NFV) architectures, load
   balancing functions are likely to be more prevalent (deployed at
   locations throughout operators' networks), so they would be handling
   traffic using encrypted tunnels whenever it is present.

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2.2.  Traffic Surveys/Monitoring

   Internet traffic surveys are useful in many pursuits, such as CAIDA
   data [CAIDA] and SP network design and optimization.  Tracking the
   trends in Internet traffic growth, from earlier peer-to-peer
   communication to the extensive adoption of unicast video streaming
   applications, has required a view of traffic composition and reports
   with acceptable accuracy.  As application designers and network
   operators both continue to seek optimizations, the role of traffic
   survey (e.g. passive monitoring) retains its importance.

   Passive monitoring makes inferences about observed traffic using the
   maximal information available, and is subject to inaccuracies
   stemming from incomplete sampling (of packets in a stream) or loss
   due to monitoring system overload.  When encryption conceals more
   layers in each packet, reliance on pattern inferences and other
   heuristics grows, and accuracy suffers.  For example, the traffic
   patterns between server and browser are dependent on browser supplier
   and version, even when the sessions use the same server application
   (e.g., web e-mail access).  It remains to be seen whether more
   complex inferences can be mastered to produce the same monitoring

2.3.  Monitoring Approaches Used by Middleboxes

2.3.1.  Traffic Analysis Fingerprinting

   Fingerprinting is used in traffic analysis and monitoring to identify
   traffic streams that match certain patterns.  This technique may be
   used with clear text or encrypted sessions.  Some Distributed Denial
   of Service (DDoS) prevention techniques at the Network SP level rely
   on the ability to fingerprint traffic in order to mitigate the effect
   of this type of attack.  Thus, fingerprinting may be an aspect of an
   attack or part of attack countermeasures.

   A common, early trigger for DDoS mitigation includes observing
   uncharacteristic traffic volumes or sources; congestion; or
   degradation of a given network or service.  One approach to mitigate
   such an attack involves distinguishing attacker traffic from
   legitimate user traffic.  The ability to examine layers and payloads
   above transport provides a new range of filtering opportunities at
   each layer in the clear.  If fewer layers are in the clear, this
   means that there are reduced filtering opportunities available to
   mitigate attacks.  However, fingerprinting is still possible.

   Passive monitoring of network traffic can lead to invasion of privacy
   by external actors at the endpoints of the monitored traffic.
   Encryption of traffic end-to-end is one method to obfuscate some of

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   the potentially identifying information.  Many DoS mitigation systems
   perform this manner of passive monitoring.

   For example, browser fingerprints are comprised of many
   characteristics, including User Agent, HTTP Accept headers, browser
   plug-in details, screen size and color details, system fonts and time
   zone.  A monitoring system could easily identify a specific browser,
   and by correlating other information, identify a specific user.

2.3.2.  Deep Packet Inspection (DPI)

   Two applications of DPI are covered below, where DPI means inspection
   deeper than the 5-tuple for the purpose of this document.  These
   applications include caching and differential treatment.  Caching

   The features and efficiency of some Internet services can be
   augmented through analysis of user flows and the applications they
   provide.  For example, network caching of popular content at a
   location close to the requesting user can improve delivery efficiency
   (both in terms of lower request response times and reduced use of
   International Internet links when content is remotely located), and
   authorized parties use DPI in combination with content distribution
   networks to determine if they can intervene effectively.  Web proxies
   are widely used [WebCache], and caching is supported by the recent
   update of "Hypertext Transfer Protocol (HTTP/1.1): Caching" in
   [RFC7234].  Encryption of packet contents at a given protocol layer
   usually makes DPI processing of that layer and higher layers
   impossible.  It should be noted that some content providers prevent
   caching to control content delivery through the use of encrypted end-
   to-end sessions.  The business risk is a motivation outside of
   privacy and pervasive monitoring that are driving end-to-end
   encryption for these content providers.  Using DPI as Input for Differential Treatment

   Data transfer capacity resources in cellular radio networks tend to
   be more constrained than in fixed networks.  This is a result of
   variance in radio signal strength as a user moves around a cell, the
   rapid ingress and egress of connections as users hand-off between
   adjacent cells, and temporary congestion at a cell.  Mobile networks
   alleviate this by queuing traffic according to its required bandwidth
   and acceptable latency: for example, a user is unlikely to notice a
   20ms delay when receiving a simple Web page or email, or an instant
   message response, but will very likely notice a re-buffering pause in
   a video playback or a VoIP call de-jitter buffer.  Ideally, the
   scheduler manages the queue so that each user has an acceptable

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   experience as conditions vary, but knowledge of the traffic type has
   been used to make bearer assignments and set scheduler priority.
   Application and transport layer encryption make the traffic type
   estimation more complex and less accurate, and therefore it may not
   be effectual anymore to use this information as input for queue
   management.  These effects and potential alternative solutions have
   been discussed at the accord BoF [ACCORD] at IETF95.

   DPI allows identification of applications based on payload
   signatures, in contrast to trusting well-known port numbers.
   Operators plan network infrastructure based on demographic shifts in
   application usage.  Past shifts have included the growth of peer-to-
   peer file sharing during all hours of the day and more recently
   growth in streaming video at prime time, both of which have impacted
   network design.

   When called upon to diagnose customer complaints, the starting point
   may be a particular application that isn't working.  Being able to
   identify that application's traffic using DPI is important; IP
   address filtering is not useful for applications using CDNs or cloud
   providers.  After identifying the traffic, an operator may analyze
   the traffic characteristics and routing of the traffic.

2.4.  Connection to Proxy for Compression

   In contrast to DPI, various applications exist to provide data
   compression in order to conserve the life of the user's mobile data
   plan and optimize delivery over the mobile link.  The compression
   proxy access can be built into a specific user level application,
   such as a browser, or it can be available to all applications using a
   system level application.  The primary method is for the mobile
   application to connect to a centralized server as a proxy, with the
   data channel between the client application and the server using
   compression to minimize bandwidth utilization.  The effectiveness of
   such systems depends on the server having access to unencrypted data
   flows.  As the percentage of connections using encryption increases,
   these data compression services will be rendered less effective, or
   worse, they will adopt undesirable security practices in order to
   gain access to the unencrypted data flows.

2.5.  Content Filtering

2.5.1.  Mobility Middlebox Content Filtering

   There are numerous motivations for service proividers to block
   content.  See RFC7754 [RFC7754] for a survey of internet filtering
   techniques and motivations, not specific to content filtering.  For
   content filtering, a couple of use cases were contributed.  Service

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   Providers may, from time to time, be requested by law enforcement
   agencies to block access to particular sites such as online betting
   and gambling, or access to dating sites.  Content Filtering may also
   happen at the endpoints or at the edge of enterprise networks.  This
   section is intended to merely document this current practice by
   operators and the effects of encryption on the practice.

   Content filtering motivations vary and in the mobile network usually
   occurs in the core network.  A proxy is installed which analyses the
   transport metadata of the content users are viewing and either
   filters content based on a blacklist of sites or based on the user's
   pre-defined profile (e.g. for age sensitive content).  Although
   filtering can be done by many methods one common method occurs when a
   DNS lookup of a hostname in a URL which appears on a government or
   recognized block-list( [RFC7858] aims to address this).  The
   subsequent requests to that domain will be re-routed to a proxy which
   checks whether the full URL matches a blocked URL on the list, and
   will return a 404 if a match is found.  All other requests should

   See Section 7 for more information on "Encryption Impact on Mobility
   Network Optimizations and New Services".

2.5.2.  Parental Controls

   Another form of content filtering is called parental control, where
   some users are deliberately denied access to age-sensitive content as
   a feature to the service subscriber.  Some sites involve a mixture of
   universal and age-sensitive content and filtering software.  In these
   cases, more granular (application layer) metadata may be used to
   analyze and block traffic.  Methods that accessed cleartext
   application-layer metadata no longer work when sessions are
   encrypted.  This type of granular filtering could occur at the
   endpoint; however, the ability to efficiently provide this as a
   service without new efficient management solutions for end point
   solutions impacts providers.

2.5.3.  HTTP Redirection

   There are cases (beyond parental control) when a mobile network
   service provider redirects customer requests for content:

   1.  The mobile network service provider is performing the accounting
       and billing for the content provider, and the customer has not
       (yet) purchased the requested content.

   2.  Further content may not be allowed as the customer has reached
       their usage limit and needs to purchase additional data service.

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   Currently, the mobile network service provider redirects the customer
   using HTTP redirect to a page which educates the customer on the
   reason for the blockage and provide steps to proceed.  Once the HTTP
   header and content are encrypted, the mobile carrier loses the option
   to intercept the traffic and perform an HTTP redirect.  With current
   solution options, this leaves only the option to block the customer's
   request and cause a bad customer experience until the blocking reason
   can be conveyed by some other means.  The customer may need to call
   customer care to find out the reason, both an inconvenience to the
   customer and additional overhead to the mobile network service
   provider.  Collaboration with Applications and Real-time area is
   requested to assist in developing alternate solutions adapted for TLS
   1.3 and future protocols that ensure session integrity.

2.6.  Access and Policy Enforcement

2.6.1.  Server load balancing

   Where network load balancers have been configured to route according
   to application-layer semantics, an encrypted payload is effectively
   invisible.  This has resulted in practices of intercepting TLS in
   front of load balancers to regain that visibility, but at a cost to
   security and privacy.

2.6.2.  Network Access

   Approved access to a network is a prerequisite to requests for
   Internet traffic - hence network access, including any authentication
   and authorization, is not impacted by encryption.

   Cellular networks often sell tariffs that allow free-data access to
   certain sites, known as 'zero rating'.  A session to visit such a
   site incurs no additional cost or data usage to the user.  This
   feature may be impacted if encryption hides the details of the
   content domain from the network.  This topic and related material are
   described further in the Section 7.

2.6.3.  Regulation and policy enforcement

   Mobile networks (and usually ISPs) operate under the regulations of
   their licensing government authority.  These regulations include
   Lawful Intercept, adherence to Codes of Practice on content
   filtering, and application of court order filters.

   These functions are impacted by encryption, typically by allowing a
   less granular means of implementation.  The enforcement of any Net
   Neutrality regulations is unlikely to be affected by content being

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   encrypted.  The IETF's Policy on Wiretapping can be found in
   [RFC2804], which does not support wiretapping in standards.

2.6.4.  Application Layer Gateways

   The policy of some mobile network service providers to deploy
   Application Layer Gateways (ALG).  Section 2.9 of [RFC2663] describes
   the role of ALG and their interaction with NAT and/or the application
   payload.  ALG are deployed to provide connectivity across Network
   Address Translators (NAT), Firewalls, and/or Load Balancers for
   specific applications the mobile network providers choose to support.
   One example is a video application that uses the Real Time Session
   Protocol (RTSP) [RFC7826] primary stream as a means to identify
   related Real Time Protocol/Real Time Control Protocol (RTP/RTCP)
   [RFC3550] flows at set-up.  The ALG relies on the 5-tuple flow
   information derived from RTSP to provision NAT or other middle boxes
   and provide connectivity.  Implementations vary, and two examples

   1.  Parse the content of the RTSP stream and identify the 5-tuple of
       the supporting streams as they are being negotiated.

   2.  Intercept and modify the 5-tuple information of the supporting
       media streams as they are being negotiated on the RTSP stream,
       which is more intrusive to the media streams.

2.6.5.  HTTP Header Insertion

   HTTP header insertion (see section 3.2.1 of [RFC7230]) has been a
   mechanism for the mobile carrier to provide "allowed" (Non-Customer
   Proprietary Network Information) subscriber information to third
   parties or other internal systems [Enrich].  Third parties can in
   turn provide customized service, or use it to bill the customer or
   allow/block selective content.  This 'header-enrichment' method is
   also used within the mobile network service provider to pass
   information internally between sub-systems, thus keeping the internal
   systems loosely-coupled.  With encryption, the mobile network service
   provider loses the capability to include any information in the
   header itself, but this is one motivation for encryption.

2.7.  Network Monitoring for Performance Management and Troubleshooting

   Network operators are often the first ones called upon to investigate
   any application problems (e.g., "my HD video is choppy").  By
   investigating packet loss (from sequence and acknowledgement
   numbers), round-trip-time (from TCP timestamp options or application-
   layer transactions, e.g., DNS or HTTP response time), receive-window
   size, packet corruption (from checksum verification), inefficient

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   fragmentation, or application-layer problems, the operator can narrow
   the problem to a portion of the network, server overload, client or
   server misconfiguration, etc.  Network operators may also be able to
   identify the presence of attack traffic as not conforming to the
   application the user claims to be using.

   One way of quickly excluding the network as the bottleneck during
   troubleshooting is to check whether the speed is limited by the
   endpoints.  For example, the connection speed might instead be
   limited by suboptimal TCP options, the sender's congestion window,
   the sender temporarily running out of data to send, the sender
   waiting for the receiver to send another request, or the receiver
   closing the receive window.

   Packet captures and protocol-dissecting analyzers have been important
   tools.  Automated monitoring has also been used to proactively
   identify poor network conditions, leading to maintenance and network
   upgrades before user experience declines.  For example, findings of
   loss and jitter in VoIP traffic can be a predictor of future customer
   dissatisfaction, or increases in DNS response time can generally make
   interactive web browsing appear sluggish.

   When utilizing increased encryption, application server operators
   should expect to be called upon more frequently to diagnose problems,
   and should consider what tools they can put in the hands of their
   clients or network operators.

   Similar to DPI, the performance of some services can be more
   efficiently managed and repaired when information on user
   transactions is available to the service provider.  It may be
   possible to continue such monitoring activities without clear text
   access to the application layers of interest, but inaccuracy will
   increase and efficiency of repair activities will decrease.  For
   example, an application protocol error or failure would be opaque to
   network troubleshooters when transport encryption is applied, making
   root cause location more difficult and therefore increasing the time-
   to-repair.  Repair time directly reduces the availability of the
   service, and availability is a key metric for Service Level
   Agreements and subscription rebates.  Also, there may be more cases
   of user communication failures when the additional encryption
   processes are introduced, leading to more customer service contacts
   and (at the same time) less information available to network
   operations repair teams.

   It is important to note that the push for encryption by application
   providers has been motivated by the application of the described
   techniques.  Some application providers have noted degraded
   performance and/or user experience when network-based optimization or

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   enhancement of their traffic has occurred, and such cases may result
   in additional operator troubleshooting, as well.

   With the use of WebSockets [RFC6455], many forms of communications
   (from isochronous/real-time to bulk/elastic file transfer) will take
   place over HTTP port 80 or port 443, so only the messages and higher-
   layer data will make application differentiation possible.  If the
   monitoring systems sees only "HTTP port 443", it cannot distinguish
   application streams that would benefit from priority queueing from
   others that would not.

3.  Encryption in Hosting SP Environments

   Hosted environments have had varied requirements in the past for
   encryption, with many businesses choosing to use these services
   primarily for data and applications that are not business or privacy
   sensitive.  A shift prior to the revelations on surveillance/passive
   monitoring began where businesses were asking for hosted environments
   to provide higher levels of security so that additional applications
   and service could be hosted externally.  Businesses understanding the
   threats of monitoring in hosted environments only increased that
   pressure to provide more secure access and session encryption to
   protect the management of hosted environments as well as for the data
   and applications.

3.1.  Management Access Security

   Hosted environments may have multiple levels of management access,
   where some may be strictly for the Hosting SP (infrastructure that
   may be shared among customers) and some may be accessed by a specific
   customer for application management.  In some cases, there are
   multiple levels of hosting service providers, further complicating
   the security of management infrastructure and the associated

   Hosting service provider management access is typically segregated
   from other traffic with a control channel and may or may not be
   encrypted depending upon the isolation characteristics of the
   management session.  Customer access may be through a dedicated
   connection, but discussion for that connection method is out-of-

   Application Service Providers may offer content-level monitoring
   options to detect intellectual property leakage, or other attacks.
   The use of session encryption will prevent Data Leakage Protection
   (DLP) used on the session streams from accessing content to search on
   keywords or phases to detect such leakage.  DLP is often used to
   prevent the leakage of Personally Identifiable Information (PII) as

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   well as financial account information, Personal Health Information
   (PHI), and Payment Card Information (PCI).  If session encryption is
   terminated at a gateway prior to accessing these services, DLP on
   session data can still be performed.  The decision of where to
   terminate encryption to hosted environments will be a risk decision
   made between the application service provider and customer
   organization according to their priorities.  DLP can be performed at
   the server for the hosted application and on an end users system in
   an organization as alternate or additional monitoring points of
   content, however this is not frequently done in a service provider

   Application service providers, by their very nature, control the
   application endpoint.  As such, much of the information gleaned from
   sessions are still available on that endpoint.  Additionally, a gap
   may exist in the logging and debugging capabilities of the
   applications that led to the use of accessing data in transport for
   some of the monitoring applications.

   Overlay networks (e.g.  VXLAN, Geneve, etc.) may be used to indicate
   desired isolation, but this is not sufficient to prevent deliberate
   attacks that are aware of the use of the overlay network.  It is
   possible to use an overlay header in combination with IPsec, but this
   adds the requirement for authentication infrastructure and may reduce
   packet transfer performance.  Additional extension mechanisms to
   provide integrity and/or privacy protections are being investigated
   for overlay encapsulations.  Section 7 of [RFC7348] describes some of
   the security issues possible when deploying VXLAN on Layer 2
   networks.  Rogue endpoints can join the multicast groups that carry
   broadcast traffic, for example.

3.1.1.  Customer Access Monitoring

   Hosted applications that allow some level of customer management
   access may also require monitoring by the hosting service provider.
   Monitoring could include access control restrictions such as
   authentication, authorization, and accounting for filtering and
   firewall rules to ensure they are continuously met.  Customer access
   may occur on multiple levels, including user-level and administrative
   access.  The hosting service provider may need to monitor access
   either through session monitoring or log evaluation to ensure
   security service level agreements (SLA) for access management are
   met.  The use of session encryption to access hosted environments
   limits access restrictions to the metadata described below.
   Monitoring and filtering may occur at an:

   2-tuple  IP-level with source and destination IP addresses alone, or

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   5-tuple  IP and protocol-level with source IP address, destination IP
      address, protocol number, source port number, and destination port

   Session encryption at the application level, TLS for example,
   currently allows access to the 5-tuple.  IP-level encryption, such as
   IPsec in tunnel mode prevents access to the original 5-tuple and may
   limit the ability to restrict traffic via filtering techniques.  This
   shift may not impact all hosting service provider solutions as
   alternate controls may be used to authenticate sessions or access may
   require that clients access such services by first connecting to the
   organization before accessing the hosted application.  Shifts in
   access may be required to maintain equivalent access control
   management.  Logs may also be used for monitoring that access control
   restrictions are met, but would be limited to the data that could be
   observed due to encryption at the point of log generation.  Log
   analysis is out of scope for this document.

3.1.2.  SP Content Monitoring of Applications

   The following observations apply to any IT organization that is
   responsible for delivering services, whether to third-parties, for
   example as a web based service, or to internal customers in an
   enterprise, e.g. a data processing system that forms a part of the
   enterprise's business.

   Organizations responsible for the operation of a data center have
   many processes which access the contents of IP packets (passive
   methods of measurement, as defined in [RFC7799]).  These processes
   are typically for service assurance or security purposes as part of
   their data center operations.

   Examples include:

      - Network Performance Monitoring/Application Performance

      - Intrusion defense/prevention systems

      - Malware detection

      - Fraud Monitoring

      - Application DDOS protection

      - Cyber-attack investigation

      - Proof of regulatory compliance

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   Many application service providers simply terminate sessions to/from
   the Internet at the edge of the data center in the form of SSL/TLS
   offload in the load balancer.  Not only does this reduce the load on
   application servers, it simplifies the processes to enable monitoring
   of the session content.

   However, in some situations, encryption deeper in the data center may
   be necessary to protect personal information or in order to meet
   industry regulations, e.g. those set out by the Payment Card Industry
   (PCI).  In such situations, various methods have been used to allow
   service assurance and security processes to access unencrypted data.
   These include SSL/TLS decryption in dedicated units, which then
   forward packets to SP-controlled tools, or by real-time or post-
   capture decryption in the tools themselves.  The use of tools that
   perform SSL/TLS decryption are impacted by the increased use of
   encryption that prevents interception.  Alternate methods to acheive
   the goals of these functions may be necessary and in some cases, the
   functions may no longer persist in a pervasively encrypted Internet.

   Data center operators may also maintain packet recordings in order to
   be able to investigate attacks, breach of internal processes, etc.
   In some industries, organizations may be legally required to maintain
   such information for compliance purposes.  Investigations of this
   nature have used access to the unencrypted contents of the packet.
   Alternate methods to investigate attacks or breach of process will
   rely on endpoint information, such as logs.  As noted previously,
   logs are often lacking in the information provided and is seen as a
   current gap hence the problem for those relying on session access.

3.2.  Hosted Applications

   Organizations are increasingly using hosted applications rather than
   in house solutions that require maintenance of equipment and
   software.  Examples include Enterprise Resource Planning (ERP)
   solutions, payroll service, time and attendance, travel and expense
   reporting among others.  Organizations may require some level of
   management access to these hosted applications and will typically
   require session encryption or a dedicated channel for this activity.

   In other cases, hosted applications may be fully managed by a hosting
   service provider with service level agreement expectations for
   availability and performance as well as for security functions
   including malware detection.  Due to the sensitive nature of these
   hosted environments, the use of encryption is already prevalent.  Any
   impact may be similar to an enterprise with tools being used inside
   of the hosted environment to monitor traffic.  Additional concerns
   were not reported in the call for contributions.

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3.2.1.  Monitoring Managed Applications

   Performance, availability, and other aspects of a SLA are often
   collected through passive monitoring.  For example:

   o  Availability: ability to establish connections with hosts to
      access applications, and discern the difference between network or
      host-related causes of unavailability.

   o  Performance: ability to complete transactions within a target
      response time, and discern the difference between network or host-
      related causes of excess response time.

   Here, as with all passive monitoring, the accuracy of inferences are
   dependent on the cleartext information available, and encryption
   would tend to reduce the information and therefore, the accuracy of
   each inference.  Passive measurement of some metrics will be
   impossible with encryption that prevents inferring packet
   correspondence across multiple observation points, such as for packet
   loss metrics.

   Until application logging is sufficient, the ability to make accurate
   inferences in an environment with increased encryption will remain a

3.2.2.  Mail Service Providers

   Mail (application) service providers vary in what services they
   offer.  Options may include a fully hosted solution where mail is
   stored external to an organization's environment on mail service
   provider equipment or the service offering may be limited to monitor
   incoming mail to remove SPAM [Section 5.1], malware [Section 5.6],
   and phishing attacks [Section 5.3] before mail is directed to the
   organization's equipment.  In both of these cases, content of the
   messages and headers is monitored to detect SPAM, malware, phishing,
   and other messages that may be considered an attack.

   STARTTLS ought have zero effect on anti-SPAM efforts for SMTP
   traffic.  Anti-SPAM services could easily be performed on an SMTP
   gateway, eliminating the need for TLS decryption services.  The
   impact to Anti-SPAM service providers should be limited to a change
   in tools, where middle boxes were deployed to perform these

   Many efforts are emerging to improve user-to-user encryption to
   protect end user's privacy.  PGP may be a front runner, and there are
   other efforts ranging from proprietary to open source ones like "Dark

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3.3.  Data Storage

   Numerous service offerings exist that provide hosted storage
   solutions.  This section describes the various offerings and details
   the monitoring for each type of service and how encryption may impact
   the operational and security monitoring performed.

   Trends in data storage encryption for hosted environments include a
   range of options.  The following list is intentionally high-level to
   describe the types of encryption used in coordination with data
   storage that may be hosted remotely, meaning the storage is
   physically located in an external data center requiring transport
   over the Internet.  Options for monitoring will vary with both
   approaches from what may be done today.

3.3.1.  Host-level Encryption

   For higher security and/or privacy of data and applications, options
   that provide end-to-end encryption of the data from the users desktop
   or server to the storage platform may be preferred.  With this
   description, host level encryption includes any solution that
   encrypts data at the object level, not transport level.  Encryption
   of data may be performed with libraries on the system or at the
   application level, which includes file encryption services via a file
   manager.  Host-level encryption is useful when data storage is
   hosted, or scenarios when storage location is determined based on
   capacity or based on a set of parameters to automate decisions.  This
   could mean that large data sets accessed infrequently could be sent
   to an off-site storage platform at an external hosting service, data
   accessed frequently may be stored locally, or the decision could be
   based on the transaction type.  Host-level encryption is grouped
   separately for the purpose of this document as data may be stored in
   multiple locations including off-site remote storage platforms.  If
   session encryption is used, the protocol is likely to be TLS.  Monitoring for Hosted Storage

   Monitoring of hosted storage solutions that use host-level (object)
   encryption is described in this subsection.  Solutions might include
   backup services and external storage services, such as those that
   burst data that exceeds internal limits on occasion to external
   storage platforms operated by a third party.

   Monitoring of data flows to hosted storage solutions is performed for
   security and operational purposes.  The security monitoring may be to
   detect anomalies in the data flows that could include changes to
   destination, the amount of data transferred, or alterations in the

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   size and frequency of flows.  Operational considerations include
   capacity and availability monitoring.

3.3.2.  Disk Encryption, Data at Rest

   There are multiple ways to achieve full disk encryption for stored
   data.  Encryption may be performed on data to be stored while in
   transit close to the storage media with solutions like Controller
   Based Encryption (CBE) or in the drive system with Self-Encrypting
   Drives (SED).  Session encryption is typically coupled with
   encryption of these data at rest (DAR) solutions to also protect data
   in transit.  Transport encryption is likely via TLS.  Monitoring Session Flows for DAR Solutions

   Monitoring for transport of data to storage platforms, where object
   level encryption is performed close to or on the storage platform are
   similar to those described in the section on Monitoring for Hosted
   Storage.  The primary difference for these solutions is the possible
   exposure of sensitive information, which could include privacy
   related data, financial information, or intellectual property if
   session encryption via TLS is not deployed.  Session encryption is
   typically used with these solutions, but that decision would be based
   on a risk assessment.  There are use cases where DAR or disk-level
   encryption is required.  Examples include preventing exposure of data
   if physical disks are stolen or lost.

3.3.3.  Cross Data Center Replication Services

   Storage services also include data replication which may occur
   between data centers and may leverage Internet connections to tunnel
   traffic.  The traffic may use iSCSI [RFC7143] or FC/IP [RFC7146]
   encapsulated in IPsec.  Either transport or tunnel mode may be used
   for IPsec depending upon the termination points of the IPsec session,
   if it is from the storage platform itself or from a gateway device at
   the edge of the data center respectively.  Monitoring Of IPSec for Data Replication Services

   Monitoring for data replication services are described in this

   Monitoring of data flows between data centers may be performed for
   security and operational purposes and would typically concentrate
   more on operational aspects since these flows are essentially virtual
   private networks (VPN) between data centers.  Operational
   considerations include capacity and availability monitoring.  The
   security monitoring may be to detect anomalies in the data flows,

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   similar to what was described in the "Monitoring for Hosted Storage

4.  Encryption for Enterprises

   Encryption of network traffic within the private enterprise is a
   growing trend, particularly in industries with audit and regulatory
   requirements.  Some enterprise internal networks are almost
   completely TLS and/or IPsec encrypted.

   For each type of monitoring, different techniques and access to parts
   of the data stream are part of current practice.  As we transition to
   an increased use of encryption, alternate methods of monitoring for
   operational purposes may be necessary to reduce the practice of
   breaking encryption and thus privacy of users (other policies may
   apply in some enterprise settings).

4.1.  Monitoring Practices of the Enterprise

   Large corporate enterprises are the owners of the platforms, data,
   and network infrastructure that provide critical business services to
   their user communities.  As such, these enterprises are responsible
   for all aspects of the performance, availability, security, and
   quality of experience for all user sessions.  These responsibilities
   break down into three basic areas:

   1.  Security Monitoring and Control

   2.  Application Performance Monitoring and Reporting

   3.  Network Diagnostics and Troubleshooting

   In each of the above areas, technical support teams utilize
   collection, monitoring, and diagnostic systems.  Some organizations
   currently use attack methods such as replicated TLS server RSA
   private keys to decrypt passively monitored copies of encrypted TLS
   packet streams.

   For an enterprise to avoid costly application down time and deliver
   expected levels of performance, protection, and availability, some
   forms of traffic analysis sometimes including examination of packet
   payloads are currently used.

4.1.1.  Security Monitoring in the Enterprise

   Enterprise users are subject to the policies of their organization
   and the jurisdictions in which the enterprise operates.  As such,
   proxies may be in use to:

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   1.  intercept outbound session traffic to monitor for intellectual
       property leakage (by users or more likely these days through
       malware and trojans),

   2.  detect viruses/malware entering the network via email or web

   3.  detect malware/Trojans in action, possibly connecting to remote

   4.  detect attacks (Cross site scripting and other common web related

   5.  track misuse and abuse by employees,

   6.  restrict the types of protocols permitted to/from the entire
       corporate environment,

   7.  detect and defend against Internet DDoS attacks, including both
       volumetric and layer 7 attacks.

   A significant portion of malware hides its activity within TLS or
   other encrypted protocols.  This includes lateral movement, Command
   and Control, and Data Exfiltration.  Detecting these functions are
   important to effective monitoring and mitigation of malicious
   traffic, not limited to malware.

   Security monitoring in the enterprise may also be performed at the
   endpoint with numerous current solutions that mitigate the same
   problems as some of the above mentioned solutions.  Since the
   software agents operate on the device, they are able to monitor
   traffic before it is encrypted, monitor for behavior changes, and
   lock down devices to use only the expected set of applications.
   Session encryption does not affect these solutions.  Some might argue
   that scaling is an issue in the enterprise, but some large
   enterprises have used these tools effectively.

4.1.2.  Application Performance Monitoring in the Enterprise

   There are two main goals of monitoring:

   1.  Assess traffic volume on a per-application basis, for billing,
       capacity planning, optimization of geographical location for
       servers or proxies, and other goals.

   2.  Assess performance in terms of application response time and user
       perceived response time.

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   Network-based Application Performance Monitoring tracks application
   response time by user and by URL, which is the information that the
   application owners and the lines of business request.  Content
   Delivery Networks (CDNs) add complexity in determining the ultimate
   endpoint destination.  By their very nature, such information is
   obscured by CDNs and encrypted protocols -- adding a new challenge
   for troubleshooting network and application problems.  URL
   identification allows the application support team to do granular,
   code level troubleshooting at multiple tiers of an application.

   New methodologies to monitor user perceived response time and to
   separate network from server time are evolving.  For example, the
   IPv6 Destination Option Header (DOH) implementation of Performance
   and Diagnostic Metrics (PDM) will provide this
   [I-D.ietf-ippm-6man-pdm-option].  Using PDM with IPSec Encapsulating
   Security Payload (ESP) Transport Mode requires placement of the PDM
   DOH within the ESP encrypted payload to avoid leaking timing and
   sequence number information that could be useful to an attacker.  Use
   of PDM DOH also may introduce some security weaknesses, including a
   timing attack, as described in Section 7 of
   [I-D.ietf-ippm-6man-pdm-option].  For these and other reasons,
   [I-D.ietf-ippm-6man-pdm-option] requires that the PDM DOH option be
   explicitly turned on by administrative action in each host where this
   measurement feature will be used.

4.1.3.  Enterprise Network Diagnostics and Troubleshooting

   One primary key to network troubleshooting is the ability to follow a
   transaction through the various tiers of an application in order to
   isolate the fault domain.  A variety of factors relating to the
   structure of the modern data center and the modern multi-tiered
   application have made it difficult to follow a transaction in network
   traces without the ability to examine some of the packet payload.
   Alternate methods, such as log analysis need improvement to fill this
   gap.  Address Sharing (NAT)

   Content Delivery Networks (CDNs) and NATs and Network Address and
   Port Translators (NAPT) obscure the ultimate endpoint designation
   (See [RFC6269] for types of address sharing and a list of issues).
   Troubleshooting a problem for a specific end user requires finding
   information such as the IP address and other identifying information
   so that their problem can be resolved in a timely manner.

   NAT is also frequently used by lower layers of the data center
   infrastructure.  Firewalls, Load Balancers, Web Servers, App Servers,
   and Middleware servers all regularly NAT the source IP of packets.

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   Combine this with the fact that users are often allocated randomly by
   load balancers to all these devices, the network troubleshooter is
   often left with very few options in today's environment due to poor
   logging implementations in applications.  As such, network
   troubleshooting is used to trace packets at a particular layer,
   decrypt them, and look at the payload to find a user session.

   This kind of bulk packet capture and bulk decryption is frequently
   used when troubleshooting a large and complex application.  Endpoints
   typically don't have the capacity to handle this level of network
   packet capture, so out-of-band networks of robust packet brokers and
   network sniffers that use techniques such as copies of TLS RSA
   private keys accomplish this task today.  TCP Pipelining/Session Multiplexing

   TCP Pipelining/Session Multiplexing used mainly by middle boxes today
   allow for multiple end user sessions to share the same TCP
   connection.  Today's network troubleshooter often relies upon session
   decryption to tell which packet belongs to which end user as the logs
   are currently inadequate for the analysis performed.

   With the advent of HTTP/2, session multiplexing will be used
   ubiquitously, both on the Internet and in the private data center.  HTTP Service Calls

   When an application server makes an HTTP service call to back end
   services on behalf of a user session, it uses a completely different
   URL and a completely different TCP connection.  Troubleshooting via
   network trace involves matching up the user request with the HTTP
   service call.  Some organizations do this today by decrypting the TLS
   packet and inspecting the payload.  Logging has not been adequate for
   their purposes.  Application Layer Data

   Many applications use text formats such as XML to transport data or
   application level information.  When transaction failures occur and
   the logs are inadequate to determine the cause, network and
   application teams work together, each having a different view of the
   transaction failure.  Using this troubleshooting method, the network
   packet is correlated with the actual problem experienced by an
   application to find a root cause.  The inability to access the
   payload prevents this method of troubleshooting.

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4.2.  Techniques for Monitoring Internet Session Traffic

   Corporate networks commonly monitor outbound session traffic to
   detect or prevent attacks as well as to guarantee service level
   expectations.  In some cases, alternate options are available when
   encryption is in use, but techniques like that of data leakage
   prevention tools at a proxy would not be possible if encrypted
   traffic can not be intercepted, encouraging alternate options such as
   performing these functions at the edge.

   DLP tools intercept traffic at the Internet gateway or proxy services
   with the ability to man-in-the-middle (MiTM) encrypted session
   traffic (HTTP/TLS).  These tools may use key words important to the
   enterprise including business sensitive information such as trade
   secrets, financial data, personally identifiable information (PII),
   or personal health information (PHI).  Various techniques are used to
   intercept HTTP/TLS sessions for DLP and other purposes, and are
   described in "Summarizing Known Attacks on TLS and DTLS" [RFC7457].
   Note: many corporate policies allow access to personal financial and
   other sites for users without interception.

   Monitoring traffic patterns for anomalous behavior such as increased
   flows of traffic that could be bursty at odd times or flows to
   unusual destinations (small or large amounts of traffic) is common.
   This traffic may or may not be encrypted and various methods of
   encryption or just obfuscation may be used.

   Restrictions on traffic to approved sites: Web proxies are sometimes
   used to filter traffic, allowing only access to well-known sites
   found to be legitimate and free of malware on last check by a proxy
   service company.  This type of restriction is usually not noticeable
   in a corporate setting as the typical corporate user does not access
   sites that are not well-known to these tools, but may be to those in
   research who are unable to access colleague's individual sites or new
   web sites that have not yet been screened.  In situations where new
   sites are required for access, they can typically be added after
   notification by the user or proxy log alerts and review.  Home mail
   account access may be blocked in corporate settings to prevent
   another vector for malware to enter as well as for intellectual
   property to leak out of the network.  This method remains functional
   with increased use of encryption and may be more effective at
   preventing malware from entering the network.  Web proxy solutions
   monitor and potentially restrict access based on the destination URL
   or the DNS name.  A complete URL may be used in cases where access
   restrictions vary for content on a particular site or for the sites
   hosted on a particular server.

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   Desktop DLP tools are used in some corporate environments as well.
   Since these tools reside on the desktop, they can intercept traffic
   before it is encrypted and may provide a continued method of
   monitoring intellectual property leakage from the desktop to the
   Internet or attached devices.

   DLP tools can also be deployed by Network Service providers, as they
   have the vantage point of monitoring all traffic paired with
   destinations off the enterprise network.  This makes an effective
   solution for enterprises that allow "bring-your-own" devices when the
   traffic is not encrypted and devices that do not fit the desktop
   category, but are used on corporate networks nonetheless.

   Enterprises may wish to reduce the traffic on their Internet access
   facilities by monitoring requests for within-policy content and
   caching it.  In this case, repeated requests for Internet content
   spawned by URLs in e-mail trade newsletters or other sources can be
   served within the enterprise network.  Gradual deployment of end to
   end encryption would tend to reduce the cacheable content over time,
   owing to concealment of critical headers and payloads.  Many forms of
   enterprise performance management and optimization based on
   monitoring (DPI) would suffer the same fate.

5.  Security Monitoring for Specific Attack Types

   Effective incident response today requires collaboration at Internet
   scale.  This section will only focus on efforts of collaboration at
   Internet scale that are dedicated to specific attack types.  They may
   require new monitoring and detection techniques in an increasingly
   encrypted Internet.  As mentioned previously, some service providers
   have been interfering with STARTTLS to prevent session encryption to
   be able to perform functions they are used to (injecting ads,
   monitoring, etc.).  By detailing the current monitoring methods used
   for attack detection and response, this information can be used to
   devise new monitoring methods that will be effective in the changed
   Internet via collaboration and innovation.

5.1.  Mail Abuse and SPAM

   The largest operational effort to prevent mail abuse is through the
   Messaging, Malware, Mobile Anti-Abuse Working Group (M3AAWG)[M3AAWG].
   Mail abuse is combated directly with mail administrators who can shut
   down or stop continued mail abuse originating from large scale
   providers that participate in using the Abuse Reporting Format (ARF)
   agents standardized in the IETF [RFC5965], [RFC6430], [RFC6590],
   [RFC6591], [RFC6650], [RFC6651], and [RFC6652].  The ARF agent
   directly reports abuse messages to the appropriate service provider
   who can take action to stop or mitigate the abuse.  Since this

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   technique uses the actual message, the use of SMTP over TLS between
   mail gateways will not affect its usefulness.  As mentioned
   previously, SMTP over TLS only protects data while in transit and the
   messages may be exposed on mail servers or mail gateways if a user-
   to-user encryption method is not used.  Current user-to-user message
   encryption methods on email (S/MIME and PGP) do not encrypt the email
   header information used by ARF and the service provider operators in
   their abuse mitigation efforts.

5.2.  Denial of Service

   Response to Denial of Service (DoS) attacks are typically coordinated
   by the SP community with a few key vendors who have tools to assist
   in the mitigation efforts.  Traffic patterns are determined from each
   DoS attack to stop or rate limit the traffic flows with patterns
   unique to that DoS attack.

   Data types used in monitoring traffic for DDoS are described in the
   DDoS Open Threat Signaling (DOTS) [DOTS] working group documents in

   Data types used in DDoS attacks have been detailed in the IODEF
   Guidance draft [I-D.ietf-mile-iodef-guidance], Appendix A.2, with the
   help of several members of the service provider community.  The
   examples provided are intended to help identify the useful data in
   detecting and mitigating these attacks independent of the transport
   and protocol descriptions in the drafts.

5.3.  Phishing

   Investigations and response to phishing attacks follow well-known
   patterns, requiring access to specific fields in email headers as
   well as content from the body of the message.  When reporting
   phishing attacks, the recipient has access to each field as well as
   the body to make content reporting possible, even when end-to-end
   encryption is used.  The email header information is useful to
   identify the mail servers and accounts used to generate or relay the
   attack messages in order to take the appropriate actions.  The
   content of the message often contains an embedded attack that may be
   in an infected file or may be a link that results in the download of
   malware to the users system.

   Administrators often find it helpful to use header information to
   track down similar message in their mail queue or users inboxes to
   prevent further infection.  Combinations of To:, From:, Subject:,
   Received: from header information might be used for this purpose.
   Administrators may also search for document attachments of the same
   name, size, or containing a file with a matching hash to a known

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   phishing attack.  Administrators might also add URLs contained in
   messages to block lists locally or this may also be done by browser
   vendors through larger scales efforts like that of the Anti-Phishing
   Working Group (APWG).  See the Coordinating Attack Response at
   Internet Scale (CARIS) workshop Report [RFC8073] for addiiotnal
   information and pointers to the APWG's efforts on anti- phishing.

   A full list of the fields used in phishing attack incident response
   can be found in RFC5901.  Future plans to increase privacy
   protections may limit some of these capabilities if some email header
   fields are encrypted, such as To:, From:, and Subject: header fields.
   This does not mean that those fields should not be encrypted, only
   that we should be aware of how they are currently used.

   Some products protect users from phishing by maintaining lists of
   known phishing domains (such as misspelled bank names) and blocking
   access.  This can be done by observing DNS, clear-text HTTP, or SNI
   in TLS, in addition to analyzing email.  Alternate options to detect
   and prevent phishing attacks may be needed.  More recent examples of
   data exchanged in spear phishing attacks has been detailed in the
   IODEF Guidance draft [I-D.ietf-mile-iodef-guidance], Appendix A.3.

5.4.  Botnets

   Botnet detection and mitigation is complex and may involve hundreds
   or thousands of hosts with numerous Command and Control (C&C)
   servers.  The techniques and data used to monitor and detect each may
   vary.  Connections to C&C servers are typically encrypted, therefore
   a move to an increasingly encrypted Internet may not affect the
   detection and sharing methods used.

5.5.  Malware

   Malware monitoring and detection techniques vary.  As mentioned in
   the enterprise section, malware monitoring may occur at gateways to
   the organization analyzing email and web traffic.  These services can
   also be provided by service providers, changing the scale and
   location of this type of monitoring.  Additionally, incident
   responders may identify attributes unique to types of malware to help
   track down instances by their communication patterns on the Internet
   or by alterations to hosts and servers.

   Data types used in malware investigations have been summarized in an
   example of the IODEF Guidance draft [I-D.ietf-mile-iodef-guidance],
   Appendix A.1.

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5.6.  Spoofed Source IP Address Protection

   The IETF has reacted to spoofed source IP address-based attacks,
   recommending the use of network ingress filtering [RFC2827] and the
   unicast Reverse Path Forwarding (uRPF) mechanism [RFC2504].  But uRPF
   suffers from limitations regarding its granularity: a malicious node
   can still use a spoofed IP address included inside the prefix
   assigned to its link.  The Source Address Validation Improvements
   (SAVI) mechanisms try to solve this issue.  Basically, a SAVI
   mechanism is based on the monitoring of a specific address
   assignment/management protocol (e.g., SLAAC [RFC4862], SEND
   [RFC3971], DHCPv4/v6 [RFC2131][RFC3315]) and, according to this
   monitoring, set-up a filtering policy allowing only the IP flows with
   a correct source IP address (i.e., any packet with a source IP
   address, from a node not owning it, is dropped).  The encryption of
   parts of the address assignment/management protocols, critical for
   SAVI mechanisms, can result in a dysfunction of the SAVI mechanisms.

5.7.  Further work

   Although incident response work will continue, new methods to prevent
   system compromise through security automation and continuous
   monitoring [SACM] may provide alternate approaches where system
   security is maintained as a preventative measure.

6.  Application-based Flow Information Visible to a Network

   This section describes specific techniques used in monitoring
   applications that may apply to various network types.

6.1.  TLS Server Name Indication

   When initiating the TLS handshake, the Client may provide an
   extension field (server_name) which indicates the server to which it
   is attempting a secure connection.  TLS SNI was standardized in 2003
   to enable servers to present the "correct TLS certificate" to clients
   in a deployment of multiple virtual servers hosted by the same server
   infrastructure and IP-address.  Although this is an optional
   extension, it is today supported by all modern browsers, web servers
   and developer libraries.  Akamai [Nygren] reports that many of their
   customer see client TLS SNI usage over 99%.  It should be noted that
   HTTP/2 introduces the Alt-SVC method for upgrading the connection
   from HTTP/1 to either unencrypted or encrypted HTTP/2.  If the
   initial HTTP/1 request is unencrypted, the destination alternate
   service name can be identified before the communication is
   potentially upgraded to encrypted HTTP/2 transport.  HTTP/2 requires
   the TLS implementation to support the Server Name Indication (SNI)
   extension (see section 9.2 of [RFC7540]).

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   This information is only visible if the client is populating the
   Server Name Indication extension.  This need not be done, but may be
   done as per TLS standard and as stated above this has been
   implemented by all major browsers.  Therefore, even if existing
   network filters look out for seeing a Server Name Indication
   extension, they may not find one.  The per-domain nature of SNI may
   not reveal the specific service or media type being accessed,
   especially where the domain is of a provider offering a range of
   email, video, Web pages etc.  For example, certain blog or social
   network feeds may be deemed 'adult content', but the Server Name
   Indication will only indicate the server domain rather than a URL

6.2.  Application Layer Protocol Negotiation (ALPN)

   ALPN is a TLS extension which may be used to indicate the application
   protocol within the TLS session.  This is likely to be of more value
   to the network where it indicates a protocol dedicated to a
   particular traffic type (such as video streaming) rather than a
   multi-use protocol.  ALPN is used as part of HTTP/2 'h2', but will
   not indicate the traffic types which may make up streams within an
   HTTP/2 multiplex.  ALPN will be encrypted in TLS 1.3.

6.3.  Content Length, BitRate and Pacing

   The content length of encrypted traffic is effectively the same as
   the cleartext.  Although block ciphers utilise padding this makes a
   negligible difference.  Bitrate and pacing are generally application
   specific, and do not change much when the content is encrypted.
   Multiplexed formats (such as HTTP/2 and QUIC) may however incorporate
   several application streams over one connection, which makes the
   bitrate/pacing no longer application-specific.

7.  Impact on Mobility Network Optimizations and New Services

   This section considers the effects of transport level encryption on
   existing forms of mobile network optimization techniques, as well as
   potential new services.  The material in this section assumes
   familiarity with mobile network concepts, specifications, and
   architectures.  Readers who need additional background should start
   with the 3GPP's web pages on various topics of interest[Web3GPP],
   especially the article on LTE. 3GPP provides a mapping between their
   expanding technologies and the different series of technical
   specifications [Map3GPP]. 3GPP also has a canonical specification of
   their vocabulary, definitions, and acronyms [Vocab], as does the RFC
   Editor for abbreviations [RFCEdit].

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7.1.  Effect of Encypted ACKs

   The stream of TCP ACKs that flow from a receiver of a byte stream
   using TCP for reliability, flow-control, and NAT/firewall transversal
   is called an ACK stream.  The ACKs contain segment numbers that
   confirm successful transmission and their RTT, or indicate packet
   loss (duplicate ACKs).  If this view of progress of stream transfer
   is lost, then the mobile network has greatly reduced ability to
   monitor transport layer performance.  When the ACK stream is
   encrypted, it prevents the following mobile network functions from

   a.  Measurement of Network Segment (Sector, eNodeB (eNB) etc.)
       characterization KPIs (Retransmissions, packet drops, Sector
       Utilization Level etc.), estimation of User/Service KQIs at
       network edges for circuit emulation (CEM), and mitigation
       methods.  The active services per user and per sector are not
       visible to a server that only services Internet Access Point
       Names (APN), and thus could not perform mitigation functions
       based on network segment view.

   b.  Retransmissions by performance-enhancing proxies (see section
       2.1.1 of [RFC3135] and section 3.5 of
       [I-D.dolson-plus-middlebox-benefits])at network edges that
       improve live transmission over long delay, capacity-varying

   c.  Content replication near the network edge (for example live
       video, DRM protected content) to maximize QOE.  Replicating every
       stream through the transit network increases backhaul cost for
       live TV.  There are alternate approaches such as blind caches
       [I-D.thomson-http-bc] being explored to allow caching of
       encrypted content.

   d.  Ability to deploy SP-operated proxies that reduce control round-
       trip time (RTT) between the TCP transmitter and receiver.  The
       RTT determines how quickly a user's attempt to cancel a video is
       recognized (how quickly the traffic is stopped, thus keeping un-
       wanted video packets from entering the radio scheduler queue).

   e.  Performance-enhancing proxy with low RTT determines the
       responsiveness of TCP flow control, and enables faster adaptation
       in a delay & capacity varying network due to user mobility.  Low
       RTT permits use of a smaller send window, which makes the flow
       control loop more responsive to changing mobile network

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7.2.  Effect of Encrypted Transport Headers

   When the Transport Header is encrypted, it prevents the following
   mobile network features from operating:

   a.  Application-type-aware network edge (middlebox) that could
       control pacing, limit simultaneous HD videos, prioritize active
       videos against new videos, etc.

   b.  For Self Organizing Networks (3GPP SON) - intelligent SON
       workflows such as content-ware MLB (Mobility Load Balancing)

   c.  For User Plane Congestion Management (3GPP UPCON) - ability to
       understand content and manage network during congestion.
       Mitigating techniques such as deferred download, off-peak
       acceleration, and outbound roamers.

   d.  Reduces the benefits IP/DSCP-based transit network delivery
       optimizations; since the multiple applications are multiplexed
       within the same 5-tuple transport connection; a reasonable
       assumption is that the DSCP markings would be withheld from the
       outer IP header to further obscure which packets belong to each
       application flow.

   e.  Advance notification for dense data usages - If the application
       types are visible, transit network element could warn (ahead of
       usage) that the requested service consumes user plan limits, and
       transmission could be terminated.  Without such visibility the
       network might have to continue the operation and stop the
       operation after the limit, because partially loaded content
       wastes resources and may not be usable by the client thus
       increasing customer complaints.  Content publisher will not know
       user-service plans, and Network Edge would not know data transfer
       lengths before large object is requested.

7.3.  Effect of Encryption on New or Emerging Services

   This section describes some new/emerging mobile services and how they
   might be affected with transport encryption:

   1.  Content/Application based Prioritization of Over-the-Top (OTT)
       services - each application-type or service has different
       delay/loss/throughput expectations, and each type of stream will
       be unknown to an edge device if encrypted; this impedes dynamic-
       QoS adaptation.

   2.  Rich Communication Services (3GPP-RCS) using different Quality
       Class Indicators (QCIs in LTE) - Operators offer different QoS

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       classes for value-added services.  The QCI type is visible in RAN
       control plane and invisible in user plane, thus the QCI cannot be
       set properly when the application -type is unknown.

   3.  Enhanced Multimedia Broadcast/Multicast Services (3GPP eMBMS) -
       trusted edge proxies facilitate delivering same stream to
       different users, using either unicast or multicast depending on
       channel conditions to the user.

7.4.  Effect of Encryption on Mobile Network Evolution

   The transport header encryption prevents trusted transit proxies.  It
   may be that the benefits of such proxies could be achieved by end to
   end client & server optimizations and distribution using CDNs, plus
   the ability to continue connections across different access
   technologies (across dynamic user IP addresses).  The following
   aspects need to be considered in this approach:

   1.  In a wireless mobile network, the delay and channel capacity per
       user and sector varies due to coverage, contention, user
       mobility, and scheduling balances fairness, capacity and service
       QoE.  If most users are at the cell edge, the controller cannot
       use more complex QAM, thus reducing total cell capacity;
       similarly if a UMTS edge is serving some number of CS-Voice
       Calls, the remaining capacity for packet services is reduced.

   2.  Roamers: Mobile wireless networks service in-bound roamers (Users
       of Operator A in a foreign operator Network B) by backhauling
       their traffic though Operator B's network to Operator A's Network
       and then serving through the P-Gateway (PGW), General GPRS
       Support Node (GGSN), Content Distribution Network (CDN) etc., of
       Operator A (User's Home Operator).  Increasing window sizes to
       compensate for the path RTT will have the limitations outlined
       earlier for TCP.  The outbound roamer scenario has a similar TCP
       performance impact.

   3.  Issues in deploying CDNs in RAN: Decreasing Client-Server control
       loop requires deploying CDNs/Cloud functions that terminate
       encryption closer to the edge.  In Cellular RAN, the user IP
       traffic is encapsulated into General Packet Radio Service (GPRS)
       Tunneling Protocol-User Plane (GTP-U in UMTS and LTE) tunnels to
       handle user mobility; the tunnels terminate in APN/GGSN/PGW that
       are in central locations.  One user's traffic may flow through
       one or more APN's (for example Internet APN, Roaming APN for
       Operator X, Video-Service APN, OnDeckAPN etc.).  The scope of
       operator private IP addresses may be limited to specific APN.
       Since CDNs generally operate on user IP flows, deploying them

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       would require enhancing them with tunnel translation, etc.,
       tunnel management functions.

   4.  While CDNs that de-encrypt flows or split-connection proxy
       (similar to split-tcp) could be deployed closer to the edges to
       reduce control loop RTT, with transport header encryption, such
       CDNs perform optimization functions only for partner client
       flows; thus content from some Small-Medium Businesses (SMBs)
       would not get such CDN benefits.

8.  Response to Increased Encryption and Looking Forward

   In the best case scenario, engineers and other innovators would work
   to solve the problems at hand in new ways rather than prevent the use
   of encryption.  As stated in [RFC7258], "an appropriate balance
   (between network management and PM mitigations) will emerge over time
   as real instances of this tension are considered."

   There has already been documented cases of service providers
   preventing STARTTLS [NoEncrypt] to prevent session encryption
   negotiation on some session to inject a super cookie.

   It is well known that national surveillance programs monitor traffic
   [JNSLP] as Internet security practitioners monitor for criminal
   activities.  Governments vary on their balance between monitoring
   versus the protection of user privacy, data, and assets.  Those that
   favor unencrypted access to data ignore the real need to protect
   users identity, financial transactions and intellectual property,
   which requires security and encryption to prevent crime.  A clear
   understanding of technology, encryption, and monitoring goals will
   aid in the development of solutions to appropriately balance these
   with privacy.  As this understanding increases, hopefully the
   discussions will improve and this draft is meant to help further the

   Terrorists and criminals have been using encryption for many years.
   Changes to improve encryption or to deploy OS methods have little
   impact on the detection of such activities as they already have
   access to strong encryption.  The current push to increase encryption
   is aimed at increasing users privacy.  There is already protection in
   place for purchases, financial transactions, systems management
   infrastructure, and intellectual property although this too can be
   improved.  The Opportunistic Security (OS) [RFC7435] efforts aim to
   increase the costs of monitoring through the use of encryption that
   can be subject to active attacks, but make passive monitoring broadly
   cost prohibitive.  This is meant to restrict monitoring to sessions
   where there is reason to have suspicion.

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9.  Security Considerations

   There are no additional security considerations as this is a summary
   and does not include a new protocol or functionality.

10.  IANA Considerations

   This memo makes no requests of IANA.

11.  Acknowledgements

   Thanks to our reviewers, Natasha Rooney, Kevin Smith, Ashutosh Dutta,
   Brandon Williams, Jean-Michel Combes, Nalini Elkins, Paul Barrett,
   Badri Subramanyan, Igor Lubashev, Suresh Krishnan, Dave Dolson,
   Mohamed Boucadair, Stephen Farrell, Warren Kumari, Alia Atlas, Roman
   Danyliw, and Mirja Kuhlewind for their editorial and content
   suggestions.  Surya K.  Kovvali provided material for section 7.
   Chris Morrow and Nik Teague provided reviews and updates specific to
   the DoS fingerprinting text.

12.  Informative References

   [ACCORD]   "Acord BoF IETF95

   [CAIDA]    "CAIDA []".

   [DOTS], , "DDoS
              Open Threat Signaling IETF Working Group".

   [EFF]      "Electronic Frontier Foundation".

   [EFF2014]  "EFF Report on STARTTLS Downgrade Attacks

   [Enrich]   Narseo Vallina-Rodriguez, et al., , "Header Enrichment or
              ISP Enrichment? Emerging Privacy Threats in Mobile
              Networks, Hot Middlebox'15, August 17-21 2015, London,
              United Kingdom", 2015.

              ETSI TS 101 331 V1.1.1 (2001-08), "Telecommunications
              security; Lawful Interception (LI); Requirements of Law
              Enforcement Agencies", August 2001.

Moriarty & Morton       Expires October 15, 2017               [Page 37]
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              Dolson, D., Snellman, J., Boucadair, M., and C. Jacquenet,
              "Beneficial Functions of Middleboxes", draft-dolson-plus-
              middlebox-benefits-03 (work in progress), March 2017.

              Elkins, N., Hamilton, R., and m.,
              "IPv6 Performance and Diagnostic Metrics (PDM) Destination
              Option", draft-ietf-ippm-6man-pdm-option-09 (work in
              progress), March 2017.

              Kampanakis, P. and M. Suzuki, "IODEF Usage Guidance",
              draft-ietf-mile-iodef-guidance-09 (work in progress),
              March 2017.

              Thomson, M., Eriksson, G., and C. Holmberg, "Caching
              Secure HTTP Content using Blind Caches", draft-thomson-
              http-bc-01 (work in progress), October 2016.

   [JNSLP]    Surveillance, Vol. 8 No. 3, "10 Standards for Oversight
              and Transparency of National Intelligence Services

   [M3AAWG]   "Messaging, Malware, Mobile Anti-Abuse Working Group

   [Map3GPP], "Mapping between
              technologies and specifications".

              "ISPs Removing their Customers EMail Encryption

   [Nygren] reaching-toward-
              universal-tls-sni.html, , "Erik Nygren, personal

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
              RFC 2131, DOI 10.17487/RFC2131, March 1997,

   [RFC2504]  Guttman, E., Leong, L., and G. Malkin, "Users' Security
              Handbook", FYI 34, RFC 2504, DOI 10.17487/RFC2504,
              February 1999, <>.

Moriarty & Morton       Expires October 15, 2017               [Page 38]
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   [RFC2663]  Srisuresh, P. and M. Holdrege, "IP Network Address
              Translator (NAT) Terminology and Considerations",
              RFC 2663, DOI 10.17487/RFC2663, August 1999,

   [RFC2804]  IAB and IESG, "IETF Policy on Wiretapping", RFC 2804,
              DOI 10.17487/RFC2804, May 2000,

   [RFC2827]  Ferguson, P. and D. Senie, "Network Ingress Filtering:
              Defeating Denial of Service Attacks which employ IP Source
              Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827,
              May 2000, <>.

   [RFC3135]  Border, J., Kojo, M., Griner, J., Montenegro, G., and Z.
              Shelby, "Performance Enhancing Proxies Intended to
              Mitigate Link-Related Degradations", RFC 3135,
              DOI 10.17487/RFC3135, June 2001,

   [RFC3315]  Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
              C., and M. Carney, "Dynamic Host Configuration Protocol
              for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
              2003, <>.

   [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
              Jacobson, "RTP: A Transport Protocol for Real-Time
              Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
              July 2003, <>.

   [RFC3971]  Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
              "SEcure Neighbor Discovery (SEND)", RFC 3971,
              DOI 10.17487/RFC3971, March 2005,

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862,
              DOI 10.17487/RFC4862, September 2007,

   [RFC5965]  Shafranovich, Y., Levine, J., and M. Kucherawy, "An
              Extensible Format for Email Feedback Reports", RFC 5965,
              DOI 10.17487/RFC5965, August 2010,

Moriarty & Morton       Expires October 15, 2017               [Page 39]
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   [RFC6269]  Ford, M., Ed., Boucadair, M., Durand, A., Levis, P., and
              P. Roberts, "Issues with IP Address Sharing", RFC 6269,
              DOI 10.17487/RFC6269, June 2011,

   [RFC6430]  Li, K. and B. Leiba, "Email Feedback Report Type Value:
              not-spam", RFC 6430, DOI 10.17487/RFC6430, November 2011,

   [RFC6455]  Fette, I. and A. Melnikov, "The WebSocket Protocol",
              RFC 6455, DOI 10.17487/RFC6455, December 2011,

   [RFC6590]  Falk, J., Ed. and M. Kucherawy, Ed., "Redaction of
              Potentially Sensitive Data from Mail Abuse Reports",
              RFC 6590, DOI 10.17487/RFC6590, April 2012,

   [RFC6591]  Fontana, H., "Authentication Failure Reporting Using the
              Abuse Reporting Format", RFC 6591, DOI 10.17487/RFC6591,
              April 2012, <>.

   [RFC6650]  Falk, J. and M. Kucherawy, Ed., "Creation and Use of Email
              Feedback Reports: An Applicability Statement for the Abuse
              Reporting Format (ARF)", RFC 6650, DOI 10.17487/RFC6650,
              June 2012, <>.

   [RFC6651]  Kucherawy, M., "Extensions to DomainKeys Identified Mail
              (DKIM) for Failure Reporting", RFC 6651,
              DOI 10.17487/RFC6651, June 2012,

   [RFC6652]  Kitterman, S., "Sender Policy Framework (SPF)
              Authentication Failure Reporting Using the Abuse Reporting
              Format", RFC 6652, DOI 10.17487/RFC6652, June 2012,

   [RFC7143]  Chadalapaka, M., Satran, J., Meth, K., and D. Black,
              "Internet Small Computer System Interface (iSCSI) Protocol
              (Consolidated)", RFC 7143, DOI 10.17487/RFC7143, April
              2014, <>.

   [RFC7146]  Black, D. and P. Koning, "Securing Block Storage Protocols
              over IP: RFC 3723 Requirements Update for IPsec v3",
              RFC 7146, DOI 10.17487/RFC7146, April 2014,

Moriarty & Morton       Expires October 15, 2017               [Page 40]
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   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,

   [RFC7234]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
              RFC 7234, DOI 10.17487/RFC7234, June 2014,

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

   [RFC7348]  Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
              L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
              eXtensible Local Area Network (VXLAN): A Framework for
              Overlaying Virtualized Layer 2 Networks over Layer 3
              Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,

   [RFC7435]  Dukhovni, V., "Opportunistic Security: Some Protection
              Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
              December 2014, <>.

   [RFC7457]  Sheffer, Y., Holz, R., and P. Saint-Andre, "Summarizing
              Known Attacks on Transport Layer Security (TLS) and
              Datagram TLS (DTLS)", RFC 7457, DOI 10.17487/RFC7457,
              February 2015, <>.

   [RFC7525]  Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
              2015, <>.

   [RFC7540]  Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
              Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
              DOI 10.17487/RFC7540, May 2015,

   [RFC7624]  Barnes, R., Schneier, B., Jennings, C., Hardie, T.,
              Trammell, B., Huitema, C., and D. Borkmann,
              "Confidentiality in the Face of Pervasive Surveillance: A
              Threat Model and Problem Statement", RFC 7624,
              DOI 10.17487/RFC7624, August 2015,

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   [RFC7754]  Barnes, R., Cooper, A., Kolkman, O., Thaler, D., and E.
              Nordmark, "Technical Considerations for Internet Service
              Blocking and Filtering", RFC 7754, DOI 10.17487/RFC7754,
              March 2016, <>.

   [RFC7799]  Morton, A., "Active and Passive Metrics and Methods (with
              Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
              May 2016, <>.

   [RFC7826]  Schulzrinne, H., Rao, A., Lanphier, R., Westerlund, M.,
              and M. Stiemerling, Ed., "Real-Time Streaming Protocol
              Version 2.0", RFC 7826, DOI 10.17487/RFC7826, December
              2016, <>.

   [RFC7858]  Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
              and P. Hoffman, "Specification for DNS over Transport
              Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
              2016, <>.

   [RFC8073]  Moriarty, K. and M. Ford, "Coordinating Attack Response at
              Internet Scale (CARIS) Workshop Report", RFC 8073,
              DOI 10.17487/RFC8073, March 2017,

              "RFC Editor Abbreviation List".

   [SACM], , "Security
              Automation and Continuous Monitoring (sacm) IETF Working

              SpecificationDetails.aspx?specificationId=558, "3GPP TR
              21.905 V13.1.0 (2016-06) Vocabulary for 3GPP

              "3GPP Web pages on specific topics of interest".

              Xing Xu, et al., , "Investigating Transparent Web Proxies
              in Cellular Networks, Passive and Active Measurement
              Conference (PAM)", 2015.

Moriarty & Morton       Expires October 15, 2017               [Page 42]
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Authors' Addresses

   Kathleen Moriarty
   Dell EMC
   176 South St
   Hopkinton, MA

   Phone: +1

   Al Morton
   AT&T Labs
   200 Laurel Avenue South
   Middletown,, NJ  07748

   Phone: +1 732 420 1571
   Fax:   +1 732 368 1192

Moriarty & Morton       Expires October 15, 2017               [Page 43]