idnits 2.17.1
draft-mm-wg-effect-encrypt-24.txt:
Checking boilerplate required by RFC 5378 and the IETF Trust (see
https://trustee.ietf.org/license-info):
----------------------------------------------------------------------------
No issues found here.
Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt:
----------------------------------------------------------------------------
No issues found here.
Checking nits according to https://www.ietf.org/id-info/checklist :
----------------------------------------------------------------------------
No issues found here.
Miscellaneous warnings:
----------------------------------------------------------------------------
== The copyright year in the IETF Trust and authors Copyright Line does not
match the current year
-- The document date (March 2, 2018) is 2219 days in the past. Is this
intentional?
Checking references for intended status: Informational
----------------------------------------------------------------------------
== Missing Reference: 'Ben17a' is mentioned on line 1615, but not defined
== Missing Reference: 'Ben17b' is mentioned on line 1615, but not defined
== Missing Reference: 'Res17a' is mentioned on line 1615, but not defined
== Missing Reference: 'Res17b' is mentioned on line 1615, but not defined
== Unused Reference: 'TLS100Proceedings' is defined on line 2412, but no
explicit reference was found in the text
== Outdated reference: A later version (-25) exists of
draft-ietf-dots-use-cases-09
== Outdated reference: A later version (-09) exists of
draft-ietf-tls-sni-encryption-00
== Outdated reference: A later version (-06) exists of
draft-mglt-nvo3-geneve-security-requirements-03
-- Obsolete informational reference (is this intentional?): RFC 3315
(Obsoleted by RFC 8415)
-- Obsolete informational reference (is this intentional?): RFC 7230
(Obsoleted by RFC 9110, RFC 9112)
-- Obsolete informational reference (is this intentional?): RFC 7234
(Obsoleted by RFC 9111)
-- Obsolete informational reference (is this intentional?): RFC 7525
(Obsoleted by RFC 9325)
-- Obsolete informational reference (is this intentional?): RFC 7540
(Obsoleted by RFC 9113)
Summary: 0 errors (**), 0 flaws (~~), 9 warnings (==), 6 comments (--).
Run idnits with the --verbose option for more detailed information about
the items above.
--------------------------------------------------------------------------------
2 Network Working Group K. Moriarty, Ed.
3 Internet-Draft Dell EMC
4 Intended status: Informational A. Morton, Ed.
5 Expires: September 3, 2018 AT&T Labs
6 March 2, 2018
8 Effects of Pervasive Encryption on Operators
9 draft-mm-wg-effect-encrypt-24
11 Abstract
13 Pervasive Monitoring (PM) attacks on the privacy of Internet users
14 are of serious concern to both the user and the operator communities.
15 RFC7258 discussed the critical need to protect users' privacy when
16 developing IETF specifications and also recognized making networks
17 unmanageable to mitigate PM is not an acceptable outcome; an
18 appropriate balance is needed. This document discusses current
19 security and network operations and management practices that may be
20 impacted by the shift to increased use of encryption to help guide
21 protocol development in support of manageable and secure networks.
23 Status of This Memo
25 This Internet-Draft is submitted in full conformance with the
26 provisions of BCP 78 and BCP 79.
28 Internet-Drafts are working documents of the Internet Engineering
29 Task Force (IETF). Note that other groups may also distribute
30 working documents as Internet-Drafts. The list of current Internet-
31 Drafts is at https://datatracker.ietf.org/drafts/current/.
33 Internet-Drafts are draft documents valid for a maximum of six months
34 and may be updated, replaced, or obsoleted by other documents at any
35 time. It is inappropriate to use Internet-Drafts as reference
36 material or to cite them other than as "work in progress."
38 This Internet-Draft will expire on September 3, 2018.
40 Copyright Notice
42 Copyright (c) 2018 IETF Trust and the persons identified as the
43 document authors. All rights reserved.
45 This document is subject to BCP 78 and the IETF Trust's Legal
46 Provisions Relating to IETF Documents
47 (https://trustee.ietf.org/license-info) in effect on the date of
48 publication of this document. Please review these documents
49 carefully, as they describe your rights and restrictions with respect
50 to this document. Code Components extracted from this document must
51 include Simplified BSD License text as described in Section 4.e of
52 the Trust Legal Provisions and are provided without warranty as
53 described in the Simplified BSD License.
55 Table of Contents
57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
58 1.1. Additional Background on Encryption Changes . . . . . . . 4
59 1.2. Examples of Attempts to Preserve Functions . . . . . . . 6
60 2. Network Service Provider Monitoring . . . . . . . . . . . . . 7
61 2.1. Passive Monitoring . . . . . . . . . . . . . . . . . . . 8
62 2.1.1. Traffic Surveys . . . . . . . . . . . . . . . . . . . 8
63 2.1.2. Troubleshooting . . . . . . . . . . . . . . . . . . . 8
64 2.1.3. Traffic Analysis Fingerprinting . . . . . . . . . . . 11
65 2.2. Traffic Optimization and Management . . . . . . . . . . . 12
66 2.2.1. Load Balancers . . . . . . . . . . . . . . . . . . . 12
67 2.2.2. Differential Treatment based on Deep Packet
68 Inspection (DPI) . . . . . . . . . . . . . . . . . . 14
69 2.2.3. Network Congestion Management . . . . . . . . . . . . 15
70 2.2.4. Performance-enhancing Proxies . . . . . . . . . . . . 15
71 2.2.5. Caching and Content Replication Near the Network Edge 16
72 2.2.6. Content Compression . . . . . . . . . . . . . . . . . 17
73 2.2.7. Service Function Chaining . . . . . . . . . . . . . . 18
74 2.3. Content Filtering, Network Access, and Accounting . . . . 18
75 2.3.1. Content Filtering . . . . . . . . . . . . . . . . . . 19
76 2.3.2. Network Access and Data Usage . . . . . . . . . . . . 20
77 2.3.3. Application Layer Gateways . . . . . . . . . . . . . 21
78 2.3.4. HTTP Header Insertion . . . . . . . . . . . . . . . . 22
79 3. Encryption in Hosting and Application SP Environments . . . . 22
80 3.1. Management Access Security . . . . . . . . . . . . . . . 22
81 3.1.1. Customer Access Monitoring . . . . . . . . . . . . . 23
82 3.1.2. SP Content Monitoring of Applications . . . . . . . . 24
83 3.2. Hosted Applications . . . . . . . . . . . . . . . . . . . 26
84 3.2.1. Monitoring Managed Applications . . . . . . . . . . . 26
85 3.2.2. Mail Service Providers . . . . . . . . . . . . . . . 27
86 3.3. Data Storage . . . . . . . . . . . . . . . . . . . . . . 27
87 3.3.1. Object-level Encryption . . . . . . . . . . . . . . . 27
88 3.3.2. Disk Encryption, Data at Rest . . . . . . . . . . . . 28
89 3.3.3. Cross Data Center Replication Services . . . . . . . 29
90 4. Encryption for Enterprises . . . . . . . . . . . . . . . . . 29
91 4.1. Monitoring Practices of the Enterprise . . . . . . . . . 30
92 4.1.1. Security Monitoring in the Enterprise . . . . . . . . 30
93 4.1.2. Application Performance Monitoring in the Enterprise 31
94 4.1.3. Enterprise Network Diagnostics and Troubleshooting . 32
95 4.2. Techniques for Monitoring Internet Session Traffic . . . 34
96 5. Security Monitoring for Specific Attack Types . . . . . . . . 36
97 5.1. Mail Abuse and spam . . . . . . . . . . . . . . . . . . . 36
98 5.2. Denial of Service . . . . . . . . . . . . . . . . . . . . 37
99 5.3. Phishing . . . . . . . . . . . . . . . . . . . . . . . . 37
100 5.4. Botnets . . . . . . . . . . . . . . . . . . . . . . . . . 38
101 5.5. Malware . . . . . . . . . . . . . . . . . . . . . . . . . 38
102 5.6. Spoofed Source IP Address Protection . . . . . . . . . . 39
103 5.7. Further work . . . . . . . . . . . . . . . . . . . . . . 39
104 6. Application-based Flow Information Visible to a Network . . . 39
105 6.1. IP Flow Information Export . . . . . . . . . . . . . . . 39
106 6.2. TLS Server Name Indication . . . . . . . . . . . . . . . 40
107 6.3. Application Layer Protocol Negotiation (ALPN) . . . . . . 41
108 6.4. Content Length, BitRate and Pacing . . . . . . . . . . . 41
109 7. Effect of Encryption on Mobile Network Evolution . . . . . . 41
110 8. Response to Increased Encryption and Looking Forward . . . . 42
111 9. Security Considerations . . . . . . . . . . . . . . . . . . . 43
112 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 43
113 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 43
114 12. Informative References . . . . . . . . . . . . . . . . . . . 43
115 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 52
117 1. Introduction
119 In response to pervasive monitoring revelations and the IETF
120 consensus that Pervasive Monitoring is an Attack [RFC7258], efforts
121 are underway to increase encryption of Internet traffic. Pervasive
122 Monitoring (PM) is of serious concern to users, operators, and
123 application providers. RFC7258 discussed the critical need to
124 protect users' privacy when developing IETF specifications and also
125 recognized that making networks unmanageable to mitigate PM is not an
126 acceptable outcome, but rather that an appropriate balance would
127 emerge over time.
129 This document describes practices currently used by network operators
130 to manage, operate, and secure their networks and how those practices
131 may be impacted by a shift to increased use of encryption. It
132 provides network operators' perspectives about the motivations and
133 objectives of those practices as well as effects anticipated by
134 operators as use of encryption increases. It is a summary of
135 concerns of the operational community as they transition to managing
136 networks with less visibility. The document does not endorse the use
137 of the practices described herein. Nor does it aim to provide a
138 comprehensive treatment of the effects of current practices, some of
139 which have been considered controversial from a technical or business
140 perspective or contradictory to previous IETF statements (e.g.,
141 [RFC1958], [RFC1984], [RFC2804]). The informational documents
142 consider the end to end (e2e) architectural principle to be a guiding
143 principle for the development of Internet protocols [RFC2775]
144 [RFC3724] [RFC7754].
146 This document aims to help IETF participants understand network
147 operators' perspectives about the impact of pervasive encryption,
148 both opportunistic and strong end-to-end encryption, on operational
149 practices. The goal is to help inform future protocol development to
150 ensure that operational impact is part of the conversation. Perhaps,
151 new methods could be developed to accomplish some of the goals of
152 current practices despite changes in the extent to which cleartext
153 will be available to network operators (including methods that rely
154 on network endpoints where applicable). Discussion of current
155 practices and the potential future changes is provided as a
156 prerequisite to potential future cross-industry and cross-layer work
157 to support the ongoing evolution towards a functional Internet with
158 pervasive encryption.
160 Traditional network management, planning, security operations, and
161 performance optimization have been developed in an Internet where a
162 large majority of data traffic flows without encryption. While
163 unencrypted traffic has made information that aids operations and
164 troubleshooting at all layers accessible, it has also made pervasive
165 monitoring by unseen parties possible. With broad support and
166 increased awareness of the need to consider privacy in all aspects
167 across the Internet, it is important to catalog existing management,
168 operational, and security practices that have depended upon the
169 availability of cleartext to function and to explore if critical
170 operational practices can be met by less invasive means.
172 This document refers to several different forms of service providers,
173 distinguished with adjectives. For example, network service
174 providers (or network operators) provide IP-packet transport
175 primarily, though they may bundle other services with packet
176 transport. Alternatively, application service providers primarily
177 offer systems that participate as an end-point in communications with
178 the application user, and hosting service providers lease computing,
179 storage, and communications systems in datacenters. In practice,
180 many companies perform two or more service provider roles, but may be
181 historically associated with one.
183 This document includes a sampling of current practices and does not
184 attempt to describe every nuance. Some sections cover technologies
185 used over a broad spectrum of devices and use cases.
187 1.1. Additional Background on Encryption Changes
189 Pervasive encryption in this document refers to all types of session
190 encryption including Transport Layer Security (TLS), IP security
191 (IPsec), TCPcrypt [TCPcrypt], QUIC [QUIC] and others that are
192 increasing in deployment usage. It is well understood that session
193 encryption helps to prevent both passive and active attacks on
194 transport protocols; more on pervasive monitoring can be found in
195 Confidentiality in the Face of Pervasive Surveillance: A Threat Model
196 and Problem Statement [RFC7624]. Active attacks have long been a
197 motivation for increased encryption, and preventing pervasive
198 monitoring became a focus just a few years ago. As such, the
199 Internet Architecture Board (IAB) released a statement advocating for
200 increased use of encryption in November 2014. Perspectives on
201 encryption paradigms have shifted over time to incorporporate ease of
202 deployment as a high priority, and balance that against providing the
203 maximum possible level of security regardless of deployment
204 considerations.
206 One such shift is documented in "Opportunistic Security" (OS)
207 [RFC7435], which suggests that when use of authenticated encryption
208 is not possible, cleartext sessions should be upgraded to
209 unauthenticated session encryption, rather than no encryption. OS
210 encourages upgrading from cleartext, but cannot require or guarantee
211 such upgrades. Once OS is used, it allows for an evolution to
212 authenticated encryption. These efforts are necessary to improve end
213 user's expectation of privacy, making pervasive monitoring cost
214 prohibitive. With OS in use, active attacks are still possible on
215 unauthenticated sessions. OS has been implemented as NULL
216 Authentication with IPsec [RFC7619] and there are a number of
217 infrastructure use cases such as server to server encryption where
218 this mode is deployed. While OS is helpful in reducing pervasive
219 monitoring by increasing the cost to monitor, it is recognized that
220 risk profiles for some applications require authenticated and secure
221 session encryption as well to prevent active attacks. IPsec, and
222 other session encryption protocols, with authentication has many
223 useful applications and usage has increased for infrastructure
224 applications such as for virtual private networks between data
225 centers. OS as well as other protocol developments, like the
226 Automated Certificate Management Environment (ACME), have increased
227 the usage of session encryption on the Internet.
229 Risk profiles vary and so do the types of session encryption
230 deployed. To understand the scope of changes in visibility a few
231 examples are highlighted. Work continues to improve the
232 implementation, development and configuration of TLS and DTLS
233 sessions to prevent active attacks used to monitor or intercept
234 session data. The changes from TLS 1.2 to 1.3 enhance the security
235 of TLS, while hiding more of the session negotiation and providing
236 less visibility on the wire. The Using TLS in Applications (UTA)
237 working group has been publishing documentation to improve the
238 security of TLS and DTLS sessions. They have documented the known
239 attack vectors in [RFC7457] and have documented Best Practices for
240 TLS and DTLS in [RFC7525] and have other documents in the queue. The
241 recommendations from these documents were built upon for TLS 1.3 to
242 provide a more inherently secure end-to-end protocol.
244 In addition to encrypted web site access (HTTP over TLS), there are
245 other well-deployed application level transport encryption efforts
246 such as mail transfer agent (MTA)-to-MTA session encryption transport
247 for email (SMTP over TLS) and gateway-to-gateway for instant
248 messaging (Extensible Messaging and Presence Protocol (XMPP) over
249 TLS). Although this does provide protection from transport layer
250 attacks, the servers could be a point of vulnerability if user-to-
251 user encryption is not provided for these messaging protocols. User-
252 to-user content encryption schemes, such as S/MIME and PGP for email
253 and Off-the-Record (OTR) encryption for XMPP are used by those
254 interested to protect their data as it crosses intermediary servers,
255 preventing transport layer attacks by providing an end-to-end
256 solution. User-to-user schemes are under review and additional
257 options will emerge to ease the configuration requirements, making
258 this type of option more accessible to non-technical users interested
259 in protecting their privacy.
261 Increased use of encryption, either opportunistic or authenticated,
262 at the transport, network or application layer, impacts how networks
263 are operated, managed, and secured. In some cases, new methods to
264 operate, manage, and secure networks will evolve in response. In
265 other cases, currently available capabilities for monitoring or
266 troubleshooting networks could become unavailable. This document
267 lists a collection of functions currently employed by network
268 operators that may be impacted by the shift to increased use of
269 encryption. This draft does not attempt to specify responses or
270 solutions to these impacts, but rather documents the current state.
272 1.2. Examples of Attempts to Preserve Functions
274 Following the Snowden [Snowden] revelations, application service
275 providers responded by encrypting traffic between their data centers
276 (IPsec) to prevent passive monitoring from taking place unbeknownst
277 to them (Yahoo, Google, etc.). Infrastructure traffic carried over
278 the public Internet has been encrypted for some time, this change for
279 universal encryption was specific to their private backbones. Large
280 mail service providers also began to encrypt session transport (TLS)
281 to hosted mail services. This and other increases in the use of
282 encryption had the immediate effect of providing confidentiality and
283 integrity for protected data, but created a problem for some network
284 management functions. Operators could no longer gain access to some
285 session streams resulting in actions by several to regain their
286 operational practices that previously depended on cleartext data
287 sessions.
289 The EFF reported [EFF2014] several network service providers using a
290 downgrade attack to prevent the use of SMTP over TLS by breaking
291 STARTTLS (section 3.2 of [RFC7525]), essentially preventing the
292 negotiation process resulting in fallback to the use of clear text.
293 There has already been documented cases of service providers
294 preventing STARTTLS to prevent session encryption negotiation on some
295 session to inject a super cookie to enable tracking of users for
296 advertisers, also considered an attack. These serves as examples of
297 undesirable behavior that could be prevented through upfront
298 discussions in protocol work for operators and protocol designers to
299 understand the implications of such actions. In other cases, some
300 service providers and enterprises have relied on middleboxes having
301 access to clear text for the purposes of load balancing, monitoring
302 for attack traffic, meeting regulatory requirements, or for other
303 purposes. The implications for enterprises, who own the data on
304 their networks is very different from service providers who may be
305 accessing content that violates privacy considerations.
306 Additionally, service provider equipment is designed for accessing
307 only the headers exposed for the data-link, network, and transport
308 layers. Delving deeper into packets is possible, but there is
309 typically a high degree of accuracy from the header information and
310 packet sizes when limited to header information from these three
311 layers. Service providers also have the option of adding routing
312 overlay protocols to traffic. These middlebox implementations,
313 whether performing functions considered legitimate by the IETF or
314 not, have been impacted by increases in encrypted traffic. Only
315 methods keeping with the goal of balancing network management and PM
316 mitigation in [RFC7258] should be considered in solution work
317 resulting from this document.
319 It is well known that national surveillance programs monitor traffic
320 [JNSLP] [RFC2804] [RFC7258] monitor for criminal activities.
321 Governments vary on their balance between monitoring versus the
322 protection of user privacy, data, and assets. Those that favor
323 unencrypted access to data ignore the real need to protect users'
324 identity, financial transactions and intellectual property, which
325 requires security and encryption to prevent crime. A clear
326 understanding of technology, encryption, and monitoring goals will
327 aid in the development of solutions as work continues towards finding
328 an appropriate balance allowing for management while protecting users
329 privacy with strong encryption solutions.
331 2. Network Service Provider Monitoring
333 Network Service Providers (SP) for this definition include the
334 backbone Internet Service providers as well as those providing
335 infrastructure at scale for core Internet use (hosted infrastructure
336 and services such as email).
338 Network service providers use various techniques to operate, manage,
339 and secure their networks. The following subsections detail the
340 purpose of several techniques and which protocol fields are used to
341 accomplish each task. In response to increased encryption of these
342 fields, some network service providers may be tempted to undertake
343 undesirable security practices in order to gain access to the fields
344 in unencrypted data flows. To avoid this situation, new methods
345 could be developed to accomplish the same goals without service
346 providers having the ability to see session data.
348 2.1. Passive Monitoring
350 2.1.1. Traffic Surveys
352 Internet traffic surveys are useful in many pursuits, such as input
353 for Center for Applied Internet Data Analysis (CAIDA) studies
354 [CAIDA], network planning and optimization. Tracking the trends in
355 Internet traffic growth, from earlier peer-to-peer communication to
356 the extensive adoption of unicast video streaming applications, has
357 relied on a view of traffic composition with a particular level of
358 assumed accuracy, based on access to cleartext by those conducting
359 the surveys.
361 Passive monitoring makes inferences about observed traffic using the
362 maximal information available, and is subject to inaccuracies
363 stemming from incomplete sampling (of packets in a stream) or loss
364 due to monitoring system overload. When encryption conceals more
365 layers in each packet, reliance on pattern inferences and other
366 heuristics grows, and accuracy suffers. For example, the traffic
367 patterns between server and browser are dependent on browser supplier
368 and version, even when the sessions use the same server application
369 (e.g., web e-mail access). It remains to be seen whether more
370 complex inferences can be mastered to produce the same monitoring
371 accuracy.
373 2.1.2. Troubleshooting
375 Network operators use protocol-dissecting analyzers when responding
376 to customer problems, to identify the presence of attack traffic, and
377 to identify root causes of the problem such as misconfiguration. In
378 limited cases, packet captures may also be used when a customer
379 approves of access to their packets or provides packet captures close
380 to the endpoint. The protocol dissection is generally limited to
381 supporting protocols (e.g., DNS, DHCP), network and transport (e.g.,
382 IP, TCP), and some higher layer protocols (e.g., RTP, RTCP).
383 Troubleshooting will move closer to the endpoint with increased
384 encryption and adjustments in practices to effectively troubleshoot
385 using a 5-tuple may require education. Packet loss investigations,
386 and those where access is limited to a 2-tuple (IPsec tunnel mode),
387 rely on network and transport layer headers taken at the endpoint.
388 In this case, captures on intermediate nodes are not reliable as
389 there are far too many cases of aggregate interfaces and alternate
390 paths in service provider networks.
392 Network operators are often the first ones called upon to investigate
393 application problems (e.g., "my HD video is choppy"), to first rule
394 out network and network services as a cause for the underlying issue.
395 When diagnosing a customer problem, the starting point may be a
396 particular application that isn't working. The ability to identify
397 the problem application's traffic is important and packet capture
398 provided from the customer close to the edge may be used for this
399 purpose; IP address filtering is not useful for applications using
400 content delivery networks (CDNs) or cloud providers. After
401 identifying the traffic, an operator may analyze the traffic
402 characteristics and routing of the traffic. This diagnostic step is
403 important to help determine the root cause before exploring if the
404 issue is directly with the application.
406 For example, by investigating packet loss (from TCP sequence and
407 acknowledgement numbers), round-trip-time (from TCP timestamp options
408 or application-layer transactions, e.g., DNS or HTTP response time),
409 TCP receive-window size, packet corruption (from checksum
410 verification), inefficient fragmentation, or application-layer
411 problems, the operator can narrow the problem to a portion of the
412 network, server overload, client or server misconfiguration, etc.
413 Network operators may also be able to identify the presence of attack
414 traffic as not conforming to the application the user claims to be
415 using. In many instances, the exposed packet header is sufficient
416 for this type of troubleshooting.
418 One way of quickly excluding the network as the bottleneck during
419 troubleshooting is to check whether the speed is limited by the
420 endpoints. For example, the connection speed might instead be
421 limited by suboptimal TCP options, the sender's congestion window,
422 the sender temporarily running out of data to send, the sender
423 waiting for the receiver to send another request, or the receiver
424 closing the receive window. All this information can be derived from
425 the cleartext TCP header.
427 Packet captures and protocol-dissecting analyzers have been important
428 tools. Automated monitoring has also been used to proactively
429 identify poor network conditions, leading to maintenance and network
430 upgrades before user experience declines. For example, findings of
431 loss and jitter in VoIP traffic can be a predictor of future customer
432 dissatisfaction (supported by metadata from the RTP/RTCP protocol )
433 [RFC3550], or increases in DNS response time can generally make
434 interactive web browsing appear sluggish. But to detect such
435 problems, the application or service stream must first be
436 distinguished from others.
438 When increased encryption is used, operators lose a source of data
439 that may be used to debug user issues. For example, IPsec obscures
440 TCP and RTP header information, while TLS and SRTP do not. Because
441 of this, application server operators using increased encryption
442 might be called upon more frequently to assist with debugging and
443 troubleshooting, and thus may want to consider what tools can be put
444 in the hands of their clients or network operators.
446 Further, the performance of some services can be more efficiently
447 managed and repaired when information on user transactions is
448 available to the service provider. It may be possible to continue
449 transaction monitoring activities without clear text access to the
450 application layers of interest, but inaccuracy will increase and
451 efficiency of repair activities will decrease. For example, an
452 application protocol error or failure would be opaque to network
453 troubleshooters when transport encryption is applied, making root
454 cause location more difficult and therefore increasing the time-to-
455 repair. Repair time directly reduces the availability of the
456 service, and most network operators have made availability a key
457 metric in their Service Level Agreements and/or subscription rebates.
458 Also, there may be more cases of user communication failures when the
459 additional encryption processes are introduced (e.g., key management
460 at large scale), leading to more customer service contacts and (at
461 the same time) less information available to network operations
462 repair teams.
464 In mobile networks, knowledge about TCP's stream transfer progress
465 (by observing ACKs, retransmissions, packet drops, and the Sector
466 Utilization Level etc.) is further used to measure the performance of
467 Network Segments (Sector, eNodeB (eNB) etc.). This information is
468 used as key performance indicators (KPIs) and for the estimation of
469 user/service key quality indicators at network edges for circuit
470 emulation (CEM) as well as input for mitigation methods. If the
471 make-up of active services per user and per sector are not visible to
472 a server that provides Internet Access Point Names (APN), it cannot
473 perform mitigation functions based on network segment view.
475 It is important to note that the push for encryption by application
476 providers has been motivated by the application of the described
477 techniques. Although network operators have noted performance
478 improvements with network-based optimization or enhancement of user
479 traffic (otherwise, deployment would not have occurred), application
480 providers have likewise noted some degraded performance and/or user
481 experience, and such cases may result in additional operator
482 troubleshooting. Further, encrypted application streams might avoid
483 outdated optimization or enhancement techniques, where they exist.
485 A gap exists for vendors where built-in diagnostics and
486 serviceability is not adequate to provide detailed logging and
487 debugging capabilities that, when possible, can access cleartext
488 network parameters. In addition to traditional logging and debugging
489 methods, packet tracing and inspection along the service path
490 provides operators the visibility to continue to diagnose problems
491 reported both internally and by their customers. Logging of service
492 path upon exit for routing overlay protocols will assist with policy
493 management and troubleshooting capabilities for traffic flows on
494 encrypted networks. Protocol trace logging and protocol data unit
495 (PDU) logging should also be considered to improve visibility to
496 monitor and troubleshoot application level traffic. Additional work
497 on this gap would assist network operators to better troubleshoot and
498 manage networks with increasing amounts of encrypted traffic.
500 2.1.3. Traffic Analysis Fingerprinting
502 Fingerprinting is used in traffic analysis and monitoring to identify
503 traffic streams that match certain patterns. This technique can be
504 used with both clear text or encrypted sessions. Some Distributed
505 Denial of Service (DDoS) prevention techniques at the network
506 provider level rely on the ability to fingerprint traffic in order to
507 mitigate the effect of this type of attack. Thus, fingerprinting may
508 be an aspect of an attack or part of attack countermeasures.
510 A common, early trigger for DDoS mitigation includes observing
511 uncharacteristic traffic volumes or sources; congestion; or
512 degradation of a given network or service. One approach to mitigate
513 such an attack involves distinguishing attacker traffic from
514 legitimate user traffic. The ability to examine layers and payloads
515 above transport provides an increased range of filtering
516 opportunities at each layer in the clear. If fewer layers are in the
517 clear, this means that there are reduced filtering opportunities
518 available to mitigate attacks. However, fingerprinting is still
519 possible.
521 Passive monitoring of network traffic can lead to invasion of privacy
522 by external actors at the endpoints of the monitored traffic.
523 Encryption of traffic end-to-end is one method to obfuscate some of
524 the potentially identifying information. For example, browser
525 fingerprints are comprised of many characteristics, including User
526 Agent, HTTP Accept headers, browser plug-in details, screen size and
527 color details, system fonts and time zone. A monitoring system could
528 easily identify a specific browser, and by correlating other
529 information, identify a specific user.
531 2.2. Traffic Optimization and Management
533 2.2.1. Load Balancers
535 A standalone load balancer is a function one can take off the shelf,
536 place in front of a pool of servers, configure appropriately, and it
537 will balance the traffic load among servers in the pool. This is a
538 typical setup for load balancers. Standalone load balancers rely on
539 the plainly observable information in the packets they are forwarding
540 and rely on industry-accepted standards in interpreting the plainly
541 observable information. Typically, this is a 5-tuple of the
542 connection. This type of configuration terminates TLS sessions at
543 the load balancer, making it the end point instead of the server.
544 Standalone load balancers are considered middleboxes, but are an
545 integral part of server infrastructure that scales.
547 In contrast, an integrated load balancer is developed to be an
548 integral part of the service provided by the server pool behind that
549 load balancer. These load balancers can communicate state with their
550 pool of servers to better route flows to the appropriate servers.
551 They rely on non-standard system-specific information and operational
552 knowledge shared between the load balancer and its servers.
554 Both standalone and integrated load balancers can be deployed in
555 pools for redundancy and load sharing. For high availability, it is
556 important that when packets belonging to a flow start to arrive at a
557 different load balancer in the load balancer pool, the packets
558 continue to be forwarded to the original server in the server pool.
559 The importance of this requirement increases as the chances of such
560 load balancer change event increases.
562 Mobile operators deploy integrated load balancers to assist with
563 maintaining connection state as devices migrate. With the
564 proliferation of mobile connected devices, there is an acute need for
565 connection-oriented protocols that maintain connections after a
566 network migration by an endpoint. This connection persistence
567 provides an additional challenge for multi-homed anycast-based
568 services typically employed by large content owners and Content
569 Distribution Networks (CDNs). The challenge is that a migration to a
570 different network in the middle of the connection greatly increases
571 the chances of the packets routed to a different anycast point-of-
572 presence (POP) due to the new network's different connectivity and
573 Internet peering arrangements. The load balancer in the new POP,
574 potentially thousands of miles away, will not have information about
575 the new flow and would not be able to route it back to the original
576 POP.
578 To help with the endpoint network migration challenges, anycast
579 service operations are likely to employ integrated load balancers
580 that, in cooperation with their pool servers, are able to ensure that
581 client-to-server packets contain some additional identification in
582 plainly-observable parts of the packets (in addition to the 5-tuple).
583 As noted in Section 2 of [RFC7258], careful consideration in protocol
584 design to mitigate PM is important, while ensuring manageability of
585 the network.
587 An area for further research includes end-to-end solutions that would
588 provide a simpler architecture and may solve the issue with CDN
589 anycast. In this case, connections would be migrated to a CDN
590 unicast address.
592 Current protocols, such as TCP, allow the development of stateless
593 integrated load balancers by availing such load balancers of
594 additional plain text information in client-to-server packets. In
595 case of TCP, such information can be encoded by having server-
596 generated sequence numbers (that are ACK'd by the client), segment
597 values, lengths of the packet sent, etc. The use of some of these
598 mechanisms for load balancing negates some of the security
599 assumptions associated with those primitives (e.g., that an off-path
600 attacker guessing valid sequence numbers for a flow is hard).
601 Another possibility is a dedicated mechanism for storing load
602 balancer state, such as QUIC's proposed connection ID to provide
603 visibility to the load balancer. An identifier could be used for
604 tracking purposes, but this may provide an option that is an
605 improvement from bolting it on to an unrelated transport signal.
606 This method allows for tight control by one of the endpoints and can
607 be rotated to avoid roving client linkability: in other words, being
608 a specific, separate signal, it can be governed in a way that is
609 finely targeted at that specific use-case.
611 Some integrated load balancers have the ability to use additional
612 plainly observable information even for today's protocols that are
613 not network migration tolerant. This additional information allows
614 for improved availability and scalability of the load balancing
615 operation. For example, BGP reconvergence can cause a flow to switch
616 anycast POPs even without a network change by any endpoint.
617 Additionally, a system that is able to encode the identity of the
618 pool server in plain text information available in each incoming
619 packet is able to provide stateless load balancing. This ability
620 confers great reliability and scalability advantages even if the flow
621 remains in a single POP, because the load balancing system is not
622 required to keep state of each flow. Even more importantly, there's
623 no requirement to continuously synchronize such state among the pool
624 of load balancers. An integrated load balancer repurposing limited
625 existing bits in transport flow state must maintain and synchronize
626 per-flow state occasionally: using the sequence number as a cookie
627 only works for so long given that there aren't that many bits
628 available to divide across a pool of machines.
630 Mobile operators apply Self Organizing Networks (3GPP SON) for
631 intelligent workflows such as content-aware MLB (Mobility Load
632 Balancing). Where network load balancers have been configured to
633 route according to application-layer semantics, an encrypted payload
634 is effectively invisible. This has resulted in practices of
635 intercepting TLS in front of load balancers to regain that
636 visibility, but at a cost to security and privacy.
638 In future Network Function Virtualization (NFV) architectures, load
639 balancing functions are likely to be more prevalent (deployed at
640 locations throughout operators' networks). NFV environments will
641 require some type of identifier (IPv6 flow identifiers, the proposed
642 QUIC connection ID, etc.) for managing traffic using encrypted
643 tunnels. The shift to increased encryption will have an impact to
644 visibility of flow information and will require adjustments to
645 perform similar load balancing functions within an NFV.
647 2.2.2. Differential Treatment based on Deep Packet Inspection (DPI)
649 Data transfer capacity resources in cellular radio networks tend to
650 be more constrained than in fixed networks. This is a result of
651 variance in radio signal strength as a user moves around a cell, the
652 rapid ingress and egress of connections as users hand off between
653 adjacent cells, and temporary congestion at a cell. Mobile networks
654 alleviate this by queuing traffic according to its required bandwidth
655 and acceptable latency: for example, a user is unlikely to notice a
656 20ms delay when receiving a simple Web page or email, or an instant
657 message response, but will very likely notice a re-buffering pause in
658 a video playback or a VoIP call de-jitter buffer. Ideally, the
659 scheduler manages the queue so that each user has an acceptable
660 experience as conditions vary, but inferences of the traffic type
661 have been used to make bearer assignments and set scheduler priority.
663 Deep Packet Inspection (DPI) allows identification of applications
664 based on payload signatures, in contrast to trusting well-known port
665 numbers. Application and transport layer encryption make the traffic
666 type estimation more complex and less accurate, and therefore it may
667 not be effectual to use this information as input for queue
668 management. With the use of WebSockets [RFC6455], for example, many
669 forms of communications (from isochronous/real-time to bulk/elastic
670 file transfer) will take place over HTTP port 80 or port 443, so only
671 the messages and higher-layer data will make application
672 differentiation possible. If the monitoring system sees only "HTTP
673 port 443", it cannot distinguish application streams that would
674 benefit from priority queueing from others that would not.
676 Mobile networks especially rely on content/application based
677 prioritization of Over-the-Top (OTT) services - each application-type
678 or service has different delay/loss/throughput expectations, and each
679 type of stream will be unknown to an edge device if encrypted; this
680 impedes dynamic-QoS adaptation. An alternate way to achieve
681 encrypted application separation is possible when the User Equipment
682 (UE) requests a dedicated bearer for the specific application stream
683 (known by the UE), using a mechanism such as the one described in
684 Section 6.5 of 3GPP TS 24.301 [TS3GPP]. The UE's request includes
685 the Quality Class Indicator (QCI) appropriate for each application,
686 based on their different delay/loss/throughput expectations.
687 However, UE requests for dedicated bearers and QCI may not be
688 supported at the subscriber's service level, or in all mobile
689 networks.
691 These effects and potential alternative solutions have been discussed
692 at the accord BoF [ACCORD] at IETF95.
694 This section does not consider traffic discrimination by service
695 providers related to NetNeutrality, where traffic may be favored
696 according to the service provider preference as opposed to the user's
697 preference. These use cases are considered out-of-scope for this
698 document as controversial practices.
700 2.2.3. Network Congestion Management
702 For User Plane Congestion Management (3GPP UPCON) [UPCON], the
703 ability to understand content and manage networks during periods of
704 congestion is the focus of this 3GPP work item. Mitigating
705 techniques such as deferred download, off-peak acceleration, and
706 outbound roamers are a few examples of the areas explored in the
707 associated 3GPP documents. The documents describe the issues, the
708 data utilized in managing congestion, and make policy
709 recommendations.
711 2.2.4. Performance-enhancing Proxies
713 Performance-enhancing TCP proxies may perform local retransmission at
714 the network edge; this also applies to mobile networks. In TCP,
715 duplicated ACKs are detected and potentially concealed when the proxy
716 retransmits a segment that was lost on the mobile link without
717 involvement of the far end (see section 2.1.1 of [RFC3135] and
718 section 3.5 of [I-D.dolson-plus-middlebox-benefits]).
720 Operators report that this optimization at network edges improves
721 real-time transmission over long delay Internet paths or networks
722 with large capacity-variation (such as mobile/cellular networks).
723 However, such optimizations can also cause problems with performance,
724 for example if the characteristics of some packet streams begin to
725 vary significantly from those considered in the proxy design.
727 In general some operators have stated that performance-enhancing
728 proxies have a lower Round-Trip Time (RTT) to the client and
729 therefore determine the responsiveness of flow control. A lower RTT
730 makes the flow control loop more responsive to changes in the mobile
731 network conditions and enables faster adaptation in a delay and
732 capacity varying network due to user mobility.
734 Further, some use service-provider-operated proxies to reduce the
735 control delay between the sender and a receiver on a mobile network
736 where resources are limited. The RTT determines how quickly a user's
737 attempt to cancel a video is recognized and therefore how quickly the
738 traffic is stopped, thus keeping un-wanted video packets from
739 entering the radio scheduler queue. If impacted by encryption,
740 performance enhancing proxies could make use of routing overlay
741 protocols to accomplish the same task, but this results in additional
742 overhead.
744 An application-type-aware network edge (middlebox) can further
745 control pacing, limit simultaneous HD videos, or prioritize active
746 videos against new videos, etc. Services at this more granular level
747 are limited with the use of encryption.
749 Performance enhancing proxies are primarily used on long delay links
750 (satellite) with access to the TCP header to provide an early ACK and
751 make the long delay link of the path seem shorter. With some
752 specific forms of flow control, TCP can be more efficient than
753 alternatives such as proxies. The editors cannot cite research on
754 this point specific to the performance enhancing proxies described,
755 but agree this area could be explored to determine if flow-control
756 modifications could preserve the end-to-end performance on long delay
757 paths session where the TCP header is exposed.
759 2.2.5. Caching and Content Replication Near the Network Edge
761 The features and efficiency of some Internet services can be
762 augmented through analysis of user flows and the applications they
763 provide. For example, network caching of popular content at a
764 location close to the requesting user can improve delivery efficiency
765 (both in terms of lower request response times and reduced use of
766 International Internet links when content is remotely located), and
767 the service provider through an authorized agreement acting on their
768 behalf use DPI in combination with content distribution networks to
769 determine if they can intervene effectively. Encryption of packet
770 contents at a given protocol layer usually makes DPI processing of
771 that layer and higher layers impossible. That being said, it should
772 be noted that some content providers prevent caching to control
773 content delivery through the use of encrypted end-to-end sessions.
774 CDNs vary in their deployment options of end-to-end encryption. The
775 business risk of losing control of content is a motivation outside of
776 privacy and pervasive monitoring that are driving end-to-end
777 encryption for these content providers.
779 It should be noted that caching was first supported in [RFC1945] and
780 continued in the recent update of "Hypertext Transfer Protocol
781 (HTTP/1.1): Caching" in [RFC7234]. Some operators also operate
782 transparent caches which neither the user nor the origin opt-in. The
783 use of these caches is controversial within IETF and is generally
784 precluded by the use of HTTPS.
786 Content replication in caches (for example live video, Digital Rights
787 Management (DRM) protected content) is used to most efficiently
788 utilize the available limited bandwidth and thereby maximize the
789 user's Quality of Experience (QoE). Especially in mobile networks,
790 duplicating every stream through the transit network increases
791 backhaul cost for live TV. The Enhanced Multimedia Broadcast/
792 Multicast Services (3GPP eMBMS) utilizes trusted edge proxies to
793 facilitate delivering the same stream to different users, using
794 either unicast or multicast depending on channel conditions to the
795 user. There are on-going efforts to support multicast inside carrier
796 networks while preserving end-to-end security: Automatic Multicast
797 Tunneling (AMT), for instance, allows CDNs to deliver a single
798 (potentially encrypted) copy of a live stream to a carrier network
799 over the public internet and for the carrier to then distribute that
800 live stream as efficiently as possible within its own network using
801 multicast.
803 Alternate approaches are in the early phase of being explored to
804 allow caching of encrypted content. These solutions require
805 cooperation from content owners and fall outside the scope of what is
806 covered in this document. Content delegation allows for replication
807 with possible benefits, but any form of delegation has the potential
808 to affect the expectation of client-server confidentiality.
810 2.2.6. Content Compression
812 In addition to caching, various applications exist to provide data
813 compression in order to conserve the life of the user's mobile data
814 plan or make delivery over the mobile link more efficient. The
815 compression proxy access can be built into a specific user level
816 application, such as a browser, or it can be available to all
817 applications using a system level application. The primary method is
818 for the mobile application to connect to a centralized server as a
819 transparent proxy (user does not opt-in), with the data channel
820 between the client application and the server using compression to
821 minimize bandwidth utilization. The effectiveness of such systems
822 depends on the server having access to unencrypted data flows.
824 Aggregated data stream content compression that spans objects and
825 data sources that can be treated as part of a unified compression
826 scheme (e.g., through the use of a shared segment store) is often
827 effective at providing data offload when there is a network element
828 close to the receiver that has access to see all the content.
830 2.2.7. Service Function Chaining
832 Service Function Chaining (SFC) has been defined in RFC7665 [RFC7665]
833 and RFC8300 [RFC8300]. As discussed in RFC7498 [RFC7498], common SFC
834 deployments may use classifiers to direct traffic into VLANs instead
835 of using NSH, as defined in RFC8300 [RFC8300]. As described in
836 RFC7665 [RFC7665], the ordered steering of traffic to support
837 specific optimizations depends upon the ability of a Classifier to
838 determine the microflows. RFC2474 [RFC2474] defines "Microflow: a
839 single instance of an application-to-application flow of packets
840 which is identified by source address, destination address, protocol
841 id, and source port, destination port (where applicable)." SFC
842 currently depends upon a classifier to at least identify the
843 microflow. As the classifier's visibility is reduced from a 5-tuple
844 to a 2-tuple, or if information above the transport layer becomes
845 inaccessible, then the SFC Classifier is not able to perform its job
846 and the service functions of the path may be adversely affected.
848 There are also mechanisms provided to protect security and privacy.
849 In the SFC case, the layer below a network service header can be
850 protected with session encryption. A goal is protecting end-user
851 data, while retaining the intended functions of RFC7665 [RFC7665] at
852 the same time.
854 2.3. Content Filtering, Network Access, and Accounting
856 Mobile Networks and many ISPs operate under the regulations of their
857 licensing government authority. These regulations include Lawful
858 Intercept, adherence to Codes of Practice on content filtering, and
859 application of court order filters. Such regulations assume network
860 access to provide content filtering and accounting, as discussed
861 below. As previously stated, the intent of this document is to
862 document existing practices; the development of IETF protocols
863 follows the guiding principles of [RFC1984] and [RFC2804] and
864 explicitly do not support tools and methods that could be used for
865 wiretapping and censorship.
867 2.3.1. Content Filtering
869 There are numerous reasons why service providers might block content:
870 to comply with requests from law enforcement or regulatory
871 authorities, to effectuate parental controls, to enforce content-
872 based billing, or for other reasons, possibly considered
873 inappropriate by some. See RFC7754 [RFC7754] for a survey of
874 Internet filtering techniques and motivations and the IAB consensus
875 on those mechanisms. This section is intended to document a
876 selection of current content blocking practices by operators and the
877 effects of encryption on those practices. Content blocking may also
878 happen at endpoints or at the edge of enterprise networks, but those
879 are not addressed in this section.
881 In a mobile network content filtering usually occurs in the core
882 network. With other networks, content filtering could occur in the
883 core network or at the edge. A proxy is installed which analyses the
884 transport metadata of the content users are viewing and either
885 filters content based on a blacklist of sites or based on the user's
886 pre-defined profile (e.g. for age sensitive content). Although
887 filtering can be done by many methods, one commonly used method
888 involves a trigger based on the proxy identifying a DNS lookup of a
889 host name in a URL which appears on a blacklist being used by the
890 operator. The subsequent requests to that domain will be re-routed
891 to a proxy which checks whether the full URL matches a blocked URL on
892 the list, and will return a 404 if a match is found. All other
893 requests should complete. This technique does not work in situations
894 where DNS traffic is encrypted (e.g., by employing [RFC7858] ). This
895 method is also used by other types of network providers enabling
896 traffic inspection, but not modification.
898 Content filtering via a proxy can also utilize an intercepting
899 certificate where the client's session is terminated at the proxy
900 enabling for cleartext inspection of the traffic. A new session is
901 created from the intercepting device to the client's destination;
902 this is an opt-in strategy for the client, where the endpoint is
903 configured to trust the intercepting certificate. Changes to TLSv1.3
904 do not impact this more invasive method of interception, that has the
905 potential to expose every HTTPS session to an active man in the
906 middle (MitM).
908 Another form of content filtering is called parental control, where
909 some users are deliberately denied access to age-sensitive content as
910 a feature to the service subscriber. Some sites involve a mixture of
911 universal and age-sensitive content and filtering software. In these
912 cases, more granular (application layer) metadata may be used to
913 analyze and block traffic. Methods that accessed cleartext
914 application-layer metadata no longer work when sessions are
915 encrypted. This type of granular filtering could occur at the
916 endpoint or as a proxy service. However, the lack of ability to
917 efficiently manage endpoints as a service reduces network service
918 providers' ability to offer parental control.
920 2.3.2. Network Access and Data Usage
922 Approved access to a network is a prerequisite to requests for
923 Internet traffic.
925 However, there are cases (beyond parental control) when a network
926 service provider currently redirects customer requests for content
927 (affecting content accessibility):
929 1. The network service provider is performing the accounting and
930 billing for the content provider, and the customer has not (yet)
931 purchased the requested content.
933 2. Further content may not be allowed as the customer has reached
934 their usage limit and needs to purchase additional data service,
935 which is the usual billing approach in mobile networks.
937 Currently, some network service providers redirect the customer using
938 HTTP redirect to a captive portal page that explains to those
939 customers the reason for the blockage and the steps to proceed.
940 [RFC6108] describes one viable web notification system. When the
941 HTTP headers and content are encrypted, this appropriately prevents
942 mobile carriers from intercepting the traffic and performing an HTTP
943 redirect. As a result, some mobile carriers block customer's
944 encrypted requests, which impacts customer experience because the
945 blocking reason must be conveyed by some other means. The customer
946 may need to call customer care to find out the reason and/or resolve
947 the issue, possibly extending the time needed to restore their
948 network access. While there are well deployed alternate SMS-based
949 solutions that do not involve out of specification protocol
950 interception, this is still an unsolved problem for non-SMS users.
952 Further, when the requested service is about to consume the remainder
953 of the user's plan limits, the transmission could be terminated and
954 advance notifications may be sent to the user by their service
955 provider to warn the user ahead of the exhausted plan. If web
956 content is encrypted, the network provider cannot know the data
957 transfer size at request time. Lacking this visibility of the
958 application type and content size, the network would continue the
959 transmission and stop the transfer when the limit was reached. A
960 partial transfer may not be usable by the client wasting both network
961 and user resources, possibly leading to customer complaints. The
962 content provider does not know user's service plans or current usage,
963 and cannot warn the user of plan exhaustion.
965 In addition, some mobile network operators sell tariffs that allow
966 free-data access to certain sites, known as 'zero rating'. A session
967 to visit such a site incurs no additional cost or data usage to the
968 user. For some implementations, zero rating is impacted if
969 encryption hides the details of the content domain from the network.
971 2.3.3. Application Layer Gateways
973 Application Layer Gateways (ALG) assist applications to set
974 connectivity across Network Address Translators (NAT), Firewalls,
975 and/or Load Balancers for specific applications running across mobile
976 networks. Section 2.9 of [RFC2663] describes the role of ALGs and
977 their interaction with NAT and/or application payloads. ALG are
978 deployed with an aim to improve connectivity. However, it is an IETF
979 Best Common Practice recommendation that ALGs for UDP-based protocols
980 should be turned off [RFC4787].
982 One example of an ALG in current use is aimed at video applications
983 that use the Real Time Session Protocol (RTSP) [RFC7826] primary
984 stream as a means to identify related Real Time Protocol/Real Time
985 Control Protocol (RTP/RTCP) [RFC3550] flows at set-up. The ALG in
986 this case relies on the 5-tuple flow information derived from RTSP to
987 provision NAT or other middleboxes and provide connectivity.
988 Implementations vary, and two examples follow:
990 1. Parse the content of the RTSP stream and identify the 5-tuple of
991 the supporting streams as they are being negotiated.
993 2. Intercept and modify the 5-tuple information of the supporting
994 media streams as they are being negotiated on the RTSP stream,
995 which is more intrusive to the media streams.
997 When RTSP stream content is encrypted, the 5-tuple information within
998 the payload is not visible to these ALG implementations, and
999 therefore they cannot provision their associated middleboxes with
1000 that information.
1002 The deployment of IPv6 may well reduce the need for NAT, and the
1003 corresponding requirement for Application Layer Gateways.
1005 2.3.4. HTTP Header Insertion
1007 Some mobile carriers use HTTP header insertion (see section 3.2.1 of
1008 [RFC7230]) to provide information about their customers to third
1009 parties or to their own internal systems [Enrich]. Third parties use
1010 the inserted information for analytics, customization, advertising,
1011 cross-site tracking of users, to bill the customer, or to selectively
1012 allow or block content. HTTP header insertion is also used to pass
1013 information internally between a mobile service provider's sub-
1014 systems, thus keeping the internal systems loosely coupled. When
1015 HTTP connections are encrypted to protect users privacy, mobile
1016 network service providers cannot insert headers to accomplish the,
1017 sometimes considered controversial, functions above.
1019 Guidance from the Internet Architecture Board has been provided in
1020 RFC8165 [RFC8165] on Design Considerations for Metadata Insertion.
1021 The guidance asserts that designs that share metadata only by
1022 explicit actions at the host are preferable to designs in which
1023 middleboxes insert metadata. Alternate notification methods that
1024 follow this and other guidance would be helpful to mobile carriers.
1026 3. Encryption in Hosting and Application SP Environments
1028 Hosted environments have had varied requirements in the past for
1029 encryption, with many businesses choosing to use these services
1030 primarily for data and applications that are not business or privacy
1031 sensitive. A shift prior to the revelations on surveillance/passive
1032 monitoring began where businesses were asking for hosted environments
1033 to provide higher levels of security so that additional applications
1034 and service could be hosted externally. Businesses understanding the
1035 threats of monitoring in hosted environments increased that pressure
1036 to provide more secure access and session encryption to protect the
1037 management of hosted environments as well as for the data and
1038 applications.
1040 3.1. Management Access Security
1042 Hosted environments may have multiple levels of management access,
1043 where some may be strictly for the Hosting SP (infrastructure that
1044 may be shared among customers) and some may be accessed by a specific
1045 customer for application management. In some cases, there are
1046 multiple levels of hosting service providers, further complicating
1047 the security of management infrastructure and the associated
1048 requirements.
1050 Hosting service provider management access is typically segregated
1051 from other traffic with a control channel and may or may not be
1052 encrypted depending upon the isolation characteristics of the
1053 management session. Customer access may be through a dedicated
1054 connection, but discussion for that connection method is out-of-scope
1055 for this document.
1057 In overlay networks (e.g. VXLAN, Geneve, etc.) that are used to
1058 provide hosted services, management access for a customer to support
1059 application management may depend upon the security mechanisms
1060 available as part of that overlay network. While overlay network
1061 data encapsulations may be used to indicate the desired isolation,
1062 this is not sufficient to prevent deliberate attacks that are aware
1063 of the use of the overlay network.
1064 [I-D.mglt-nvo3-geneve-security-requirements] describes requirements
1065 to handle attacks. It is possible to use an overlay header in
1066 combination with IPsec or other encrypted traffic sessions, but this
1067 adds the requirement for authentication infrastructure and may reduce
1068 packet transfer performance. The use of an overlay header may also
1069 be deployed as a mechanism to manage encrypted traffic streams on the
1070 network by network service providers. Additional extension
1071 mechanisms to provide integrity and/or privacy protections are being
1072 investigated for overlay encapsulations. Section 7 of [RFC7348]
1073 describes some of the security issues possible when deploying VXLAN
1074 on Layer 2 networks. Rogue endpoints can join the multicast groups
1075 that carry broadcast traffic, for example.
1077 3.1.1. Customer Access Monitoring
1079 Hosted applications that allow some level of customer management
1080 access may also require monitoring by the hosting service provider.
1081 Monitoring could include access control restrictions such as
1082 authentication, authorization, and accounting for filtering and
1083 firewall rules to ensure they are continuously met. Customer access
1084 may occur on multiple levels, including user-level and administrative
1085 access. The hosting service provider may need to monitor access
1086 either through session monitoring or log evaluation to ensure
1087 security service level agreements (SLA) for access management are
1088 met. The use of session encryption to access hosted environments
1089 limits access restrictions to the metadata described below.
1090 Monitoring and filtering may occur at an:
1092 2-tuple IP-level with source and destination IP addresses alone, or
1094 5-tuple IP and protocol-level with source IP address, destination IP
1095 address, protocol number, source port number, and destination port
1096 number.
1098 Session encryption at the application level, TLS for example,
1099 currently allows access to the 5-tuple. IP-level encryption, such as
1100 IPsec in tunnel mode prevents access to the original 5-tuple and may
1101 limit the ability to restrict traffic via filtering techniques. This
1102 shift may not impact all hosting service provider solutions as
1103 alternate controls may be used to authenticate sessions or access may
1104 require that clients access such services by first connecting to the
1105 organization before accessing the hosted application. Shifts in
1106 access may be required to maintain equivalent access control
1107 management. Logs may also be used for monitoring that access control
1108 restrictions are met, but would be limited to the data that could be
1109 observed due to encryption at the point of log generation. Log
1110 analysis is out of scope for this document.
1112 3.1.2. SP Content Monitoring of Applications
1114 The following observations apply to any IT organization that is
1115 responsible for delivering services, whether to third-parties, for
1116 example as a web based service, or to internal customers in an
1117 enterprise, e.g. a data processing system that forms a part of the
1118 enterprise's business.
1120 Organizations responsible for the operation of a data center have
1121 many processes which access the contents of IP packets (passive
1122 methods of measurement, as defined in [RFC7799]). These processes
1123 are typically for service assurance or security purposes as part of
1124 their data center operations.
1126 Examples include:
1128 - Network Performance Monitoring/Application Performance
1129 Monitoring
1131 - Intrusion defense/prevention systems
1133 - Malware detection
1135 - Fraud Monitoring
1137 - Application DDOS protection
1139 - Cyber-attack investigation
1141 - Proof of regulatory compliance
1143 - Data Leakage Prevention
1145 Many application service providers simply terminate sessions to/from
1146 the Internet at the edge of the data center in the form of SSL/TLS
1147 offload in the load balancer. Not only does this reduce the load on
1148 application servers, it simplifies the processes to enable monitoring
1149 of the session content.
1151 However, in some situations, encryption deeper in the data center may
1152 be necessary to protect personal information or in order to meet
1153 industry regulations, e.g. those set out by the Payment Card Industry
1154 (PCI). In such situations, various methods have been used to allow
1155 service assurance and security processes to access unencrypted data.
1156 These include SSL/TLS decryption in dedicated units, which then
1157 forward packets to SP-controlled tools, or by real-time or post-
1158 capture decryption in the tools themselves. The use of passive tools
1159 that perform SSL/TLS decryption are impacted by the increased use of
1160 encryption that prevents monitoring via interception, while providing
1161 forward secrecy.
1163 Data center operators may also maintain packet recordings in order to
1164 be able to investigate attacks, breach of internal processes, etc.
1165 In some industries, organizations may be legally required to maintain
1166 such information for compliance purposes. Investigations of this
1167 nature have used access to the unencrypted contents of the packet.
1168 Alternate methods to investigate attacks or breach of process will
1169 rely on endpoint information, such as logs. As previously noted,
1170 logs often lack complete information, and this is seen as a concern
1171 resulting in some relying on session access for additional
1172 information.
1174 Application Service Providers may offer content-level monitoring
1175 options to detect intellectual property leakage, or other attacks.
1176 In service provider environments where Data Loss Prevention (DLP) has
1177 been implemented on the basis of the service provider having
1178 cleartext access to session streams, the use of encrypted streams
1179 prevents these implementations from conducting content searches for
1180 the keywords or phrases configured in the DLP system. DLP is often
1181 used to prevent the leakage of Personally Identifiable Information
1182 (PII) as well as financial account information, Personal Health
1183 Information (PHI), and Payment Card Information (PCI). If session
1184 encryption is terminated at a gateway prior to accessing these
1185 services, DLP on session data can still be performed. The decision
1186 of where to terminate encryption to hosted environments will be a
1187 risk decision made between the application service provider and
1188 customer organization according to their priorities. DLP can be
1189 performed at the server for the hosted application and on an end
1190 user's system in an organization as alternate or additional
1191 monitoring points of content; however, this is not frequently done in
1192 a service provider environment.
1194 Application service providers, by their very nature, control the
1195 application endpoint. As such, much of the information gleaned from
1196 sessions are still available on that endpoint. However, when a gap
1197 exists in the application's logging and debugging capabilities, this
1198 has led the application service provider to access data-in-transport
1199 for monitoring and debugging.
1201 3.2. Hosted Applications
1203 Organizations are increasingly using hosted applications rather than
1204 in-house solutions that require maintenance of equipment and
1205 software. Examples include Enterprise Resource Planning (ERP)
1206 solutions, payroll service, time and attendance, travel and expense
1207 reporting among others. Organizations may require some level of
1208 management access to these hosted applications and will typically
1209 require session encryption or a dedicated channel for this activity.
1211 In other cases, hosted applications may be fully managed by a hosting
1212 service provider with service level agreement expectations for
1213 availability and performance as well as for security functions
1214 including malware detection. Due to the sensitive nature of these
1215 hosted environments, the use of encryption is already prevalent. Any
1216 impact may be similar to an enterprise with tools being used inside
1217 of the hosted environment to monitor traffic. Additional concerns
1218 were not reported in the call for contributions.
1220 3.2.1. Monitoring Managed Applications
1222 Performance, availability, and other aspects of a SLA are often
1223 collected through passive monitoring. For example:
1225 o Availability: ability to establish connections with hosts to
1226 access applications, and discern the difference between network or
1227 host-related causes of unavailability.
1229 o Performance: ability to complete transactions within a target
1230 response time, and discern the difference between network or host-
1231 related causes of excess response time.
1233 Here, as with all passive monitoring, the accuracy of inferences are
1234 dependent on the cleartext information available, and encryption
1235 would tend to reduce the information and therefore, the accuracy of
1236 each inference. Passive measurement of some metrics will be
1237 impossible with encryption that prevents inferring packet
1238 correspondence across multiple observation points, such as for packet
1239 loss metrics.
1241 Application logging currently lacks detail sufficient to make
1242 accurate inferences in an environment with increased encryption, and
1243 so this constitutes a gap for passive performance monitoring (which
1244 could be closed if log details are enhanced in the future).
1246 3.2.2. Mail Service Providers
1248 Mail (application) service providers vary in what services they
1249 offer. Options may include a fully hosted solution where mail is
1250 stored external to an organization's environment on mail service
1251 provider equipment or the service offering may be limited to monitor
1252 incoming mail to remove spam [Section 5.1], malware [Section 5.6],
1253 and phishing attacks [Section 5.3] before mail is directed to the
1254 organization's equipment. In both of these cases, content of the
1255 messages and headers is monitored to detect spam, malware, phishing,
1256 and other messages that may be considered an attack.
1258 STARTTLS should have zero effect on anti-spam efforts for SMTP
1259 traffic. Anti-spam services could easily be performed on an SMTP
1260 gateway, eliminating the need for TLS decryption services. The
1261 impact to anti-spam service providers should be limited to a change
1262 in tools, where middleboxes were deployed to perform these functions.
1264 Many efforts are emerging to improve user-to-user encryption,
1265 including promotion of PGP and newer efforts such as Dark Mail
1266 [DarkMail]. Of course, content-based spam filtering will not be
1267 possible on encrypted content.
1269 3.3. Data Storage
1271 Numerous service offerings exist that provide hosted storage
1272 solutions. This section describes the various offerings and details
1273 the monitoring for each type of service and how encryption may impact
1274 the operational and security monitoring performed.
1276 Trends in data storage encryption for hosted environments include a
1277 range of options. The following list is intentionally high-level to
1278 describe the types of encryption used in coordination with data
1279 storage that may be hosted remotely, meaning the storage is
1280 physically located in an external data center requiring transport
1281 over the Internet. Options for monitoring will vary with each
1282 encryption approach described below. In most cases, solutions have
1283 been identified to provide encryption while ensuring management
1284 capabilities were maintained through logging or other means.
1286 3.3.1. Object-level Encryption
1288 For higher security and/or privacy of data and applications, options
1289 that provide end-to-end encryption of the data from the user's
1290 desktop or server to the storage platform may be preferred. This
1291 description includes any solution that encrypts data at the object
1292 level, not transport level. Encryption of data may be performed with
1293 libraries on the system or at the application level, which includes
1294 file encryption services via a file manager. Object-level encryption
1295 is useful when data storage is hosted, or scenarios when the storage
1296 location is determined based on capacity or based on a set of
1297 parameters to automate decisions. This could mean that large data
1298 sets accessed infrequently could be sent to an off-site storage
1299 platform at an external hosting service, data accessed frequently may
1300 be stored locally, or the decision could be based on the transaction
1301 type. Object-level encryption is grouped separately for the purpose
1302 of this document since data may be stored in multiple locations
1303 including off-site remote storage platforms. If session encryption
1304 is also used, the protocol is likely to be TLS.
1306 Impacts to monitoring may include access to content inspection for
1307 data leakage prevention and similar technologies, depending on their
1308 placement in the network.
1310 3.3.1.1. Monitoring for Hosted Storage
1312 Monitoring of hosted storage solutions that use host-level (object)
1313 encryption is described in this subsection. Host-level encryption
1314 can be employed for backup services, and occasionally for external
1315 storage services (operated by a third party) when internal storage
1316 limits are exceeded.
1318 Monitoring of data flows to hosted storage solutions is performed for
1319 security and operational purposes. The security monitoring may be to
1320 detect anomalies in the data flows that could include changes to
1321 destination, the amount of data transferred, or alterations in the
1322 size and frequency of flows. Operational considerations include
1323 capacity and availability monitoring.
1325 3.3.2. Disk Encryption, Data at Rest
1327 There are multiple ways to achieve full disk encryption for stored
1328 data. Encryption may be performed on data to be stored while in
1329 transit close to the storage media with solutions like Controller
1330 Based Encryption (CBE) or in the drive system with Self-Encrypting
1331 Drives (SED). Session encryption is typically coupled with
1332 encryption of these data at rest (DAR) solutions to also protect data
1333 in transit. Transport encryption is likely via TLS.
1335 3.3.2.1. Monitoring Session Flows for Data at Rest (DAR) Solutions
1337 Monitoring for transport of data to storage platforms, where object
1338 level encryption is performed close to or on the storage platform are
1339 similar to those described in the section on Monitoring for Hosted
1340 Storage. The primary difference for these solutions is the possible
1341 exposure of sensitive information, which could include privacy
1342 related data, financial information, or intellectual property if
1343 session encryption via TLS is not deployed. Session encryption is
1344 typically used with these solutions, but that decision would be based
1345 on a risk assessment. There are use cases where DAR or disk-level
1346 encryption is required. Examples include preventing exposure of data
1347 if physical disks are stolen or lost. In the case where TLS is in
1348 use, monitoring and the exposure of data is limited to a 5-tuple.
1350 3.3.3. Cross Data Center Replication Services
1352 Storage services also include data replication which may occur
1353 between data centers and may leverage Internet connections to tunnel
1354 traffic. The traffic may use iSCSI [RFC7143] or FC/IP [RFC7146]
1355 encapsulated in IPsec. Either transport or tunnel mode may be used
1356 for IPsec depending upon the termination points of the IPsec session,
1357 if it is from the storage platform itself or from a gateway device at
1358 the edge of the data center respectively.
1360 3.3.3.1. Monitoring Of IPsec for Data Replication Services
1362 Monitoring of data flows between data centers (for data replication)
1363 may be performed for security and operational purposes and would
1364 typically concentrate more on operational aspects since these flows
1365 are essentially virtual private networks (VPN) between data centers.
1366 Operational considerations include capacity and availability
1367 monitoring. The security monitoring may be to detect anomalies in
1368 the data flows, similar to what was described in the "Monitoring for
1369 Hosted Storage Section". If IPsec tunnel mode is in use, monitoring
1370 is limited to a 2-tuple, or with transport mode, a 5-tuple.
1372 4. Encryption for Enterprises
1374 Encryption of network traffic within the private enterprise is a
1375 growing trend, particularly in industries with audit and regulatory
1376 requirements. Some enterprise internal networks are almost
1377 completely TLS and/or IPsec encrypted.
1379 For each type of monitoring, different techniques and access to parts
1380 of the data stream are part of current practice. As we transition to
1381 an increased use of encryption, alternate methods of monitoring for
1382 operational purposes may be necessary to reduce the practice of
1383 breaking encryption (other policies may apply in some enterprise
1384 settings).
1386 4.1. Monitoring Practices of the Enterprise
1388 Large corporate enterprises are the owners of the platforms, data,
1389 and network infrastructure that provide critical business services to
1390 their user communities. As such, these enterprises are responsible
1391 for all aspects of the performance, availability, security, and
1392 quality of experience for all user sessions. In many such
1393 enterprises, users are required to consent to the enterprise
1394 monitoring all their activities as a condition of employment.
1395 Subsections of 4. Encryption for Enterprises may discuss techniques
1396 that access data beyond the data-link, network, and transport level
1397 headers typically used in SP networks since the corporate enterprise
1398 owns the data. These responsibilities break down into three basic
1399 areas:
1401 1. Security Monitoring and Control
1403 2. Application Performance Monitoring and Reporting
1405 3. Network Diagnostics and Troubleshooting
1407 In each of the above areas, technical support teams utilize
1408 collection, monitoring, and diagnostic systems. Some organizations
1409 currently use attack methods such as replicated TLS server RSA
1410 private keys to decrypt passively monitored copies of encrypted TLS
1411 packet streams.
1413 For an enterprise to avoid costly application down time and deliver
1414 expected levels of performance, protection, and availability, some
1415 forms of traffic analysis, sometimes including examination of packet
1416 payloads, are currently used.
1418 4.1.1. Security Monitoring in the Enterprise
1420 Enterprise users are subject to the policies of their organization
1421 and the jurisdictions in which the enterprise operates. As such,
1422 proxies may be in use to:
1424 1. intercept outbound session traffic to monitor for intellectual
1425 property leakage (by users, malware, and trojans),
1427 2. detect viruses/malware entering the network via email or web
1428 traffic,
1430 3. detect malware/Trojans in action, possibly connecting to remote
1431 hosts,
1433 4. detect attacks (Cross site scripting and other common web related
1434 attacks),
1436 5. track misuse and abuse by employees,
1438 6. restrict the types of protocols permitted to/from the entire
1439 corporate environment,
1441 7. detect and defend against Internet DDoS attacks, including both
1442 volumetric and layer 7 attacks.
1444 A significant portion of malware hides its activity within TLS or
1445 other encryption protocols. This includes lateral movement, Command
1446 and Control, and Data Exfiltration.
1448 The impact to a fully encrypted internal network would include cost
1449 and possible loss of detection capabilities associated with the
1450 transformation of the network architecture and tools for monitoring.
1451 The capabilities of detection through traffic fingerprinting, logs,
1452 host-level transaction monitoring, and flow analysis would vary
1453 depending on access to a 2-tuple or 5-tuple in the network as well.
1455 Security monitoring in the enterprise may also be performed at the
1456 endpoint with numerous current solutions that mitigate the same
1457 problems as some of the above mentioned solutions. Since the
1458 software agents operate on the device, they are able to monitor
1459 traffic before it is encrypted, monitor for behavior changes, and
1460 lock down devices to use only the expected set of applications.
1461 Session encryption does not affect these solutions. Some might argue
1462 that scaling is an issue in the enterprise, but some large
1463 enterprises have used these tools effectively.
1465 Use of Bring-your-own-device (BYOD) policies within organizations may
1466 limit the scope of monitoring permitted with these alternate
1467 solutions. Network endpoint assessment (NEA) or the use of virtual
1468 hosts could help to bridge the monitoring gap.
1470 4.1.2. Application Performance Monitoring in the Enterprise
1472 There are two main goals of monitoring:
1474 1. Assess traffic volume on a per-application basis, for billing,
1475 capacity planning, optimization of geographical location for
1476 servers or proxies, and other goals.
1478 2. Assess performance in terms of application response time and user
1479 perceived response time.
1481 Network-based Application Performance Monitoring tracks application
1482 response time by user and by URL, which is the information that the
1483 application owners and the lines of business request. Content
1484 Delivery Networks (CDNs) add complexity in determining the ultimate
1485 endpoint destination. By their very nature, such information is
1486 obscured by CDNs and encrypted protocols -- adding a new challenge
1487 for troubleshooting network and application problems. URL
1488 identification allows the application support team to do granular,
1489 code level troubleshooting at multiple tiers of an application.
1491 New methodologies to monitor user perceived response time and to
1492 separate network from server time are evolving. For example, the
1493 IPv6 Destination Option Header (DOH) implementation of Performance
1494 and Diagnostic Metrics (PDM) will provide this [RFC8250]. Using PDM
1495 with IPsec Encapsulating Security Payload (ESP) Transport Mode
1496 requires placement of the PDM DOH within the ESP encrypted payload to
1497 avoid leaking timing and sequence number information that could be
1498 useful to an attacker. Use of PDM DOH also may introduce some
1499 security weaknesses, including a timing attack, as described in
1500 Section 7 of [RFC8250]. For these and other reasons, [RFC8250]
1501 requires that the PDM DOH option be explicitly turned on by
1502 administrative action in each host where this measurement feature
1503 will be used.
1505 4.1.3. Enterprise Network Diagnostics and Troubleshooting
1507 One primary key to network troubleshooting is the ability to follow a
1508 transaction through the various tiers of an application in order to
1509 isolate the fault domain. A variety of factors relating to the
1510 structure of the modern data center and multi-tiered application have
1511 made it difficult to follow a transaction in network traces without
1512 the ability to examine some of the packet payload. Alternate
1513 methods, such as log analysis need improvement to fill this gap.
1515 4.1.3.1. Address Sharing (NAT)
1517 Content Delivery Networks (CDNs) and NATs and Network Address and
1518 Port Translators (NAPT) obscure the ultimate endpoint designation
1519 (See [RFC6269] for types of address sharing and a list of issues).
1520 Troubleshooting a problem for a specific end user requires finding
1521 information such as the IP address and other identifying information
1522 so that their problem can be resolved in a timely manner.
1524 NAT is also frequently used by lower layers of the data center
1525 infrastructure. Firewalls, Load Balancers, Web Servers, App Servers,
1526 and Middleware servers all regularly NAT the source IP of packets.
1527 Combine this with the fact that users are often allocated randomly by
1528 load balancers to all these devices, the network troubleshooter is
1529 often left with very few options in today's environment due to poor
1530 logging implementations in applications. As such, network
1531 troubleshooting is used to trace packets at a particular layer,
1532 decrypt them, and look at the payload to find a user session.
1534 This kind of bulk packet capture and bulk decryption is frequently
1535 used when troubleshooting a large and complex application. Endpoints
1536 typically don't have the capacity to handle this level of network
1537 packet capture, so out-of-band networks of robust packet brokers and
1538 network sniffers that use techniques such as copies of TLS RSA
1539 private keys accomplish this task today.
1541 4.1.3.2. TCP Pipelining/Session Multiplexing
1543 TCP pipelining/session multiplexing used mainly by middleboxes today
1544 allows for multiple end user sessions to share the same TCP
1545 connection. This raises several points of interest with an increased
1546 use of encryption. TCP session multiplexing should still be possible
1547 when TLS or TCPcrypt is in use since the TCP header information is
1548 exposed leaving the 5-tuple accessible. The use of TCP session
1549 multiplexing of an IP layer encryption, e.g. IPsec, that only
1550 exposes a 2-tuple would not be possible. Troubleshooting
1551 capabilities with encrypted sessions from the middlebox may limit
1552 troubleshooting to the use of logs from the end points performing the
1553 TCP multiplexing or from the middleboxes prior to any additional
1554 encryption that may be added to tunnel the TCP multiplexed traffic.
1556 Increased use of HTTP/2 will likely further increase the prevalence
1557 of session multiplexing, both on the Internet and in the private data
1558 center. HTTP pipelining requires both the client and server to
1559 participate; visibility of packets once encrypted will hide the use
1560 of HTTP pipelining for any monitoring that takes place outside of the
1561 endpoint or proxy solution. Since HTTP pipelining is between a
1562 client and server, logging capabilities may require improvement in
1563 some servers and clients for debugging purposes if this is not
1564 already possible. Visibility for middleboxes includes anything
1565 exposed by TLS and the 5-tuple.
1567 4.1.3.3. HTTP Service Calls
1569 When an application server makes an HTTP service call to back end
1570 services on behalf of a user session, it uses a completely different
1571 URL and a completely different TCP connection. Troubleshooting via
1572 network trace involves matching up the user request with the HTTP
1573 service call. Some organizations do this today by decrypting the TLS
1574 packet and inspecting the payload. Logging has not been adequate for
1575 their purposes.
1577 4.1.3.4. Application Layer Data
1579 Many applications use text formats such as XML to transport data or
1580 application level information. When transaction failures occur and
1581 the logs are inadequate to determine the cause, network and
1582 application teams work together, each having a different view of the
1583 transaction failure. Using this troubleshooting method, the network
1584 packet is correlated with the actual problem experienced by an
1585 application to find a root cause. The inability to access the
1586 payload prevents this method of troubleshooting.
1588 4.2. Techniques for Monitoring Internet Session Traffic
1590 Corporate networks commonly monitor outbound session traffic to
1591 detect or prevent attacks as well as to guarantee service level
1592 expectations. In some cases, alternate options are available when
1593 encryption is in use through a proxy or a shift to monitoring at the
1594 endpoint. In both cases, scaling is a concern and advancements to
1595 support this shift in monitoring practices will assist the deployment
1596 of end-to-end encryption.
1598 Some DLP tools intercept traffic at the Internet gateway or proxy
1599 services with the ability to man-in-the-middle (MiTM) encrypted
1600 session traffic (HTTP/TLS). These tools may monitor for key words
1601 important to the enterprise including business sensitive information
1602 such as trade secrets, financial data, personally identifiable
1603 information (PII), or personal health information (PHI). Various
1604 techniques are used to intercept HTTP/TLS sessions for DLP and other
1605 purposes, and can be misused as described in "Summarizing Known
1606 Attacks on TLS and DTLS" [RFC7457] Section 2.8. Note: many corporate
1607 policies allow access to personal financial and other sites for users
1608 without interception. Another option is to terminate a TLS session
1609 prior to the point where monitoring is performed. Aside from
1610 exposing user information to the enterprise MITM devices often are
1611 subject to severe security defects which can lead to exposure of user
1612 data to attackers outside the enterprise UserData [UserData]. In
1613 addition, implementation errors in middleboxes have led to major
1614 difficulties in deploying new versions of security protocols such as
1615 TLS [Ben17a][Ben17b][Res17a][Res17b]
1617 Monitoring traffic patterns for anomalous behavior such as increased
1618 flows of traffic that could be bursty at odd times or flows to
1619 unusual destinations (small or large amounts of traffic) is common.
1620 This traffic may or may not be encrypted and various methods of
1621 encryption or just obfuscation may be used.
1623 Web filtering devices are sometimes used to allow only access to
1624 well-known sites found to be legitimate and free of malware on last
1625 check by a web filtering service company. One common example of web
1626 filtering in a corporate environment is blocking access to sites that
1627 are not well-known to these tools for the purpose of blocking
1628 malware; this may be noticeable to those in research who are unable
1629 to access colleague's individual sites or new web sites that have not
1630 yet been screened. In situations where new sites are required for
1631 access, they can typically be added after notification by the user or
1632 log alerts and review. Home mail account access may be blocked in
1633 corporate settings to prevent another vector for malware to enter as
1634 well as for intellectual property to leak out of the network. This
1635 method remains functional with increased use of encryption and may be
1636 more effective at preventing malware from entering the network. Some
1637 enterprises may be more aggessive in their filtering and monitoring
1638 policy, causing undesirable outcomes. Web filtering solutions
1639 monitor and potentially restrict access based on the destination URL
1640 when available, server name, IP address, or the DNS name. A complete
1641 URL may be used in cases where access restrictions vary for content
1642 on a particular site or for the sites hosted on a particular server.
1643 In some cases, the enterprise may use a proxy to access this
1644 additional information based on their policy. This type of
1645 restriction is intended to be transparent to users in a corporate
1646 setting as the typical corporate user does not access sites which are
1647 not well-known to these tools. However, the mechanisms which these
1648 web filters use to do monitoring and enforcement have the potential
1649 to cause access issues or other user-visible failures.
1651 Desktop DLP tools are used in some corporate environments as well.
1652 Since these tools reside on the desktop, they can intercept traffic
1653 before it is encrypted and may provide a continued method of
1654 monitoring intellectual property leakage from the desktop to the
1655 Internet or attached devices.
1657 DLP tools can also be deployed by Network Service providers, as they
1658 have the vantage point of monitoring all traffic paired with
1659 destinations off the enterprise network. This makes an effective
1660 solution for enterprises that allow "bring-your-own" devices when the
1661 traffic is not encrypted, and for devices outside the desktop
1662 category (such as mobile phones) that are used on corporate networks
1663 nonetheless.
1665 Enterprises may wish to reduce the traffic on their Internet access
1666 facilities by monitoring requests for within-policy content and
1667 caching it. In this case, repeated requests for Internet content
1668 spawned by URLs in e-mail trade newsletters or other sources can be
1669 served within the enterprise network. Gradual deployment of end to
1670 end encryption would tend to reduce the cacheable content over time,
1671 owing to concealment of critical headers and payloads. Many forms of
1672 enterprise performance management may be similarly affected. It
1673 should be noted that transparent caching is considered an anti-
1674 pattern.
1676 5. Security Monitoring for Specific Attack Types
1678 Effective incident response today requires collaboration at Internet
1679 scale. This section will only focus on efforts of collaboration at
1680 Internet scale that are dedicated to specific attack types. They may
1681 require new monitoring and detection techniques in an increasingly
1682 encrypted Internet. As mentioned previously, some service providers
1683 have been interfering with STARTTLS to prevent session encryption to
1684 be able to perform functions they are used to (injecting ads,
1685 monitoring, etc.). By detailing the current monitoring methods used
1686 for attack detection and response, this information can be used to
1687 devise new monitoring methods that will be effective in the changed
1688 Internet via collaboration and innovation.
1690 Changes to improve encryption or to deploy OS methods have little
1691 impact on the detection of malicious actors. Malicious actors have
1692 had access to strong encryption for quite some time. Incident
1693 responders, in many cases, have developed techniques to locate
1694 malicious traffic within encrypted sessions. The following section
1695 will note some examples where detection and mitigation of such
1696 traffic has been successful.
1698 5.1. Mail Abuse and spam
1700 The largest operational effort to prevent mail abuse is through the
1701 Messaging, Malware, Mobile Anti-Abuse Working Group (M3AAWG)[M3AAWG].
1702 Mail abuse is combatted directly with mail administrators who can
1703 shut down or stop continued mail abuse originating from large scale
1704 providers that participate in using the Abuse Reporting Format (ARF)
1705 agents standardized in the IETF [RFC5965], [RFC6430], [RFC6590],
1706 [RFC6591], [RFC6650], [RFC6651], and [RFC6652]. The ARF agent
1707 directly reports abuse messages to the appropriate service provider
1708 who can take action to stop or mitigate the abuse. Since this
1709 technique uses the actual message, the use of SMTP over TLS between
1710 mail gateways will not affect its usefulness. As mentioned
1711 previously, SMTP over TLS only protects data while in transit and the
1712 messages may be exposed on mail servers or mail gateways if a user-
1713 to-user encryption method is not used. Current user-to-user message
1714 encryption methods on email (S/MIME and PGP) do not encrypt the email
1715 header information used by ARF and the service provider operators in
1716 their abuse mitigation efforts.
1718 Another effort, Domain-based Message Authentication, Reporting, and
1719 Conformance (DMARC) [RFC7489] is a mechanism for policy distribution
1720 that enables increasingly strict handling of messages that fail
1721 authentication checks, ranging from no action, through altered
1722 delivery, up to message rejection. DMARC is also not affected by the
1723 use of STARTTLS.
1725 5.2. Denial of Service
1727 Response to Denial of Service (DoS) attacks are typically coordinated
1728 by the SP community with a few key vendors who have tools to assist
1729 in the mitigation efforts. Traffic patterns are determined from each
1730 DoS attack to stop or rate limit the traffic flows with patterns
1731 unique to that DoS attack.
1733 Data types used in monitoring traffic for DDoS are described in the
1734 DDoS Open Threat Signaling (DOTS) [DOTS] working group documents in
1735 development. The impact of encryption can be understood from their
1736 documented use cases[I-D.ietf-dots-use-cases].
1738 Data types used in DDoS attacks have been detailed in the IODEF
1739 Guidance draft [RFC8274], Appendix A.2, with the help of several
1740 members of the service provider community. The examples provided are
1741 intended to help identify the useful data in detecting and mitigating
1742 these attacks independent of the transport and protocol descriptions
1743 in the drafts.
1745 5.3. Phishing
1747 Investigations and response to phishing attacks follow well-known
1748 patterns, requiring access to specific fields in email headers as
1749 well as content from the body of the message. When reporting
1750 phishing attacks, the recipient has access to each field as well as
1751 the body to make content reporting possible, even when end-to-end
1752 encryption is used. The email header information is useful to
1753 identify the mail servers and accounts used to generate or relay the
1754 attack messages in order to take the appropriate actions. The
1755 content of the message often contains an embedded attack that may be
1756 in an infected file or may be a link that results in the download of
1757 malware to the user's system.
1759 Administrators often find it helpful to use header information to
1760 track down similar message in their mail queue or users inboxes to
1761 prevent further infection. Combinations of To:, From:, Subject:,
1762 Received: from header information might be used for this purpose.
1763 Administrators may also search for document attachments of the same
1764 name, size, or containing a file with a matching hash to a known
1765 phishing attack. Administrators might also add URLs contained in
1766 messages to block lists locally or this may also be done by browser
1767 vendors through larger scales efforts like that of the Anti-Phishing
1768 Working Group (APWG). See the Coordinating Attack Response at
1769 Internet Scale (CARIS) workshop Report [RFC8073] for additional
1770 information and pointers to the APWG's efforts on anti- phishing.
1772 A full list of the fields used in phishing attack incident response
1773 can be found in RFC5901. Future plans to increase privacy
1774 protections may limit some of these capabilities if some email header
1775 fields are encrypted, such as To:, From:, and Subject: header fields.
1776 This does not mean that those fields should not be encrypted, only
1777 that we should be aware of how they are currently used.
1779 Some products protect users from phishing by maintaining lists of
1780 known phishing domains (such as misspelled bank names) and blocking
1781 access. This can be done by observing DNS, clear-text HTTP, or
1782 server name indication (SNI) in TLS, in addition to analyzing email.
1783 Alternate options to detect and prevent phishing attacks may be
1784 needed. More recent examples of data exchanged in spear phishing
1785 attacks has been detailed in the IODEF Guidance draft [RFC8274],
1786 Appendix A.3.
1788 5.4. Botnets
1790 Botnet detection and mitigation is complex as botnets may involve
1791 hundreds or thousands of hosts with numerous Command and Control
1792 (C&C) servers. The techniques and data used to monitor and detect
1793 each may vary. Connections to C&C servers are typically encrypted,
1794 therefore a move to an increasingly encrypted Internet may not affect
1795 the detection and sharing methods used.
1797 5.5. Malware
1799 Malware monitoring and detection techniques vary. As mentioned in
1800 the enterprise section, malware monitoring may occur at gateways to
1801 the organization analyzing email and web traffic. These services can
1802 also be provided by service providers, changing the scale and
1803 location of this type of monitoring. Additionally, incident
1804 responders may identify attributes unique to types of malware to help
1805 track down instances by their communication patterns on the Internet
1806 or by alterations to hosts and servers.
1808 Data types used in malware investigations have been summarized in an
1809 example of the IODEF Guidance draft [RFC8274], Appendix A.1.
1811 5.6. Spoofed Source IP Address Protection
1813 The IETF has reacted to spoofed source IP address-based attacks,
1814 recommending the use of network ingress filtering BCP 38 [RFC2827]
1815 and the unicast Reverse Path Forwarding (uRPF) mechanism [RFC2504].
1816 But uRPF suffers from limitations regarding its granularity: a
1817 malicious node can still use a spoofed IP address included inside the
1818 prefix assigned to its link. The Source Address Validation
1819 Improvements (SAVI) mechanisms try to solve this issue. Basically, a
1820 SAVI mechanism is based on the monitoring of a specific address
1821 assignment/management protocol (e.g., SLAAC [RFC4862], SEND
1822 [RFC3971], DHCPv4/v6 [RFC2131][RFC3315]) and, according to this
1823 monitoring, set-up a filtering policy allowing only the IP flows with
1824 a correct source IP address (i.e., any packet with a source IP
1825 address, from a node not owning it, is dropped). The encryption of
1826 parts of the address assignment/management protocols, critical for
1827 SAVI mechanisms, can result in a dysfunction of the SAVI mechanisms.
1829 5.7. Further work
1831 Although incident response work will continue, new methods to prevent
1832 system compromise through security automation and continuous
1833 monitoring [SACM] may provide alternate approaches where system
1834 security is maintained as a preventative measure.
1836 6. Application-based Flow Information Visible to a Network
1838 This section describes specific techniques used in monitoring
1839 applications that is visible to the network if a 5-tuple is exposed
1840 and as such can potentially be used an input future network
1841 management approaches. It also includes an overview of IPFIX, a
1842 flow-based protocol used to export information about network flows.
1844 6.1. IP Flow Information Export
1846 Many of the accounting, monitoring and measurement tasks described in
1847 this document, especially Section 2.3.2, Section 3.1.1,
1848 Section 4.1.3, Section 4.2, and Section 5.2 use the IPFIX protocol
1849 [RFC7011] for export and storage of the monitored information. IPFIX
1850 evolved from the widely-deployed NetFlow protocol [RFC3954], which
1851 exports information about flows identified by 5-tuple. While NetFlow
1852 was largely concerned with exporting per-flow byte and packet counts
1853 for accounting purposes, IPFIX's extensible information model
1854 [RFC7012] provides a variety of Information Elements (IEs)
1855 [IPFIX-IANA] for representing information above and below the
1856 traditional network layer flow information. Enterprise-specific IEs
1857 allow exporter vendors to define their own non-standard IEs, as well,
1858 and many of these are driven by header and payload inspection at the
1859 metering process.
1861 While the deployment of encryption has no direct effect on the use of
1862 IPFIX, certain defined IEs may become unavailable when the metering
1863 process observing the traffic cannot decrypt formerly cleartext
1864 information. For example, HTTPS renders HTTP header analysis
1865 impossible, so IEs derived from the header (e.g. httpContentType,
1866 httpUserAgent) cannot be exported.
1868 The collection of IPFIX data itself, of course, provides a point of
1869 centralization for potentially business- and privacy-critical
1870 information. The IPFIX File Format specification [RFC5655]
1871 recommends encryption for this data at rest, and the IP Flow
1872 Anonymization specification [RFC6235] defines a metadata format for
1873 describing the anonymization functions applied to an IPFIX dataset,
1874 if anonymization is employed for data sharing of IPFIX information
1875 between enterprises or network operators.
1877 6.2. TLS Server Name Indication
1879 When initiating the TLS handshake, the Client may provide an
1880 extension field (server_name) which indicates the server to which it
1881 is attempting a secure connection. TLS SNI was standardized in 2003
1882 to enable servers to present the "correct TLS certificate" to clients
1883 in a deployment of multiple virtual servers hosted by the same server
1884 infrastructure and IP-address. Although this is an optional
1885 extension, it is today supported by all modern browsers, web servers
1886 and developer libraries. Akamai [Nygren] reports that many of their
1887 customer see client TLS SNI usage over 99%. It should be noted that
1888 HTTP/2 introduces the Alt-SVC method for upgrading the connection
1889 from HTTP/1 to either unencrypted or encrypted HTTP/2. If the
1890 initial HTTP/1 request is unencrypted, the destination alternate
1891 service name can be identified before the communication is
1892 potentially upgraded to encrypted HTTP/2 transport. HTTP/2 requires
1893 the TLS implementation to support the Server Name Indication (SNI)
1894 extension (see section 9.2 of [RFC7540]). It is also worth noting
1895 that [RFC7838] "allows an origin server to nominate additional means
1896 of interacting with it on the network", while [RFC8164] allows for a
1897 URI to be accessed with HTTP/2 and TLS using Opportunistic Security
1898 (on an experimental basis).
1900 This information is only available if the client populates the Server
1901 Name Indication extension. Doing so is an optional part of the TLS
1902 standard and as stated above this has been implemented by all major
1903 browsers. Due to its optional nature, though, existing network
1904 filters that examine a TLS ClientHello for a SNI extension cannot
1905 expect to always find one. The SNI Encryption in TLS Through
1906 Tunneling [I-D.ietf-tls-sni-encryption] draft has been adopted by the
1907 TLS working group, which provides solutions to encrypt SNI. As such,
1908 there will be an option to encrypt SNI in future versions of TLS.
1909 The per-domain nature of SNI may not reveal the specific service or
1910 media type being accessed, especially where the domain is of a
1911 provider offering a range of email, video, Web pages etc. For
1912 example, certain blog or social network feeds may be deemed 'adult
1913 content', but the Server Name Indication will only indicate the
1914 server domain rather than a URL path.
1916 There are additional issues for identification of content using SNI:
1917 [RFC7540] includes connection coalescing,
1918 [I-D.ietf-httpbis-origin-frame] defines the ORIGIN frame, and the
1919 [I-D.bishop-httpbis-http2-additional-certs] proposal will increase
1920 the difficulty of passive monitoring.
1922 6.3. Application Layer Protocol Negotiation (ALPN)
1924 ALPN is a TLS extension which may be used to indicate the application
1925 protocol within the TLS session. This is likely to be of more value
1926 to the network where it indicates a protocol dedicated to a
1927 particular traffic type (such as video streaming) rather than a
1928 multi-use protocol. ALPN is used as part of HTTP/2 'h2', but will
1929 not indicate the traffic types which may make up streams within an
1930 HTTP/2 multiplex. ALPN is sent clear text in the ClientHello and the
1931 server returns it in Encrypted Extensions in TLS 1.3.
1933 6.4. Content Length, BitRate and Pacing
1935 The content length of encrypted traffic is effectively the same as
1936 that of the cleartext. Although block ciphers utilize padding, this
1937 makes a negligible difference. Bitrate and pacing are generally
1938 application specific, and do not change much when the content is
1939 encrypted. Multiplexed formats (such as HTTP/2 and QUIC) may however incorporate several application
1941 streams over one connection, which makes the bitrate/pacing no longer
1942 application-specific. Also, packet padding is available in HTTP/2,
1943 TLS 1.3, and many other protocols. Traffic analysis is made more
1944 difficult by such countermeasures.
1946 7. Effect of Encryption on Mobile Network Evolution
1948 Transport header encryption prevents the use of transit proxies in
1949 center of the network and the use of some edge proxies by preventing
1950 the proxies from taking action on the stream. It may be that the
1951 claimed benefits of such proxies could be achieved by end-to-end
1952 client and server optimizations, distribution using CDNs, plus the
1953 ability to continue connections across different access technologies
1954 (across dynamic user IP addresses). The following aspects should be
1955 considered in this approach:
1957 1. In a wireless mobile network, the delay and channel capacity per
1958 user and sector varies due to coverage, contention, user
1959 mobility, scheduling balances fairness, capacity, and service
1960 QoE. If most users are at the cell edge, the controller cannot
1961 use more complex QAM, thus reducing total cell capacity;
1962 similarly if a UMTS edge is serving some number of CS-Voice
1963 Calls, the remaining capacity for packet services is reduced.
1965 2. Mobile wireless networks service in-bound roamers (Users of
1966 Operator A in a foreign operator Network B) by backhauling their
1967 traffic though Operator B's network to Operator A's Network and
1968 then serving through the P-Gateway (PGW), General GPRS Support
1969 Node (GGSN), Content Distribution Network (CDN) etc., of Operator
1970 A (User's Home Operator). Increasing window sizes to compensate
1971 for the path RTT will have the limitations outlined earlier for
1972 TCP. The outbound roamer scenario has a similar TCP performance
1973 impact.
1975 3. Issues in deploying CDNs in Radio Access Networks (RAN) include
1976 decreasing client-server control loop that requires deploying
1977 CDNs/Cloud functions that terminate encryption closer to the
1978 edge. In Cellular RAN, the user IP traffic is encapsulated into
1979 General Packet Radio Service (GPRS) Tunneling Protocol-User Plane
1980 (GTP-U in UMTS and LTE) tunnels to handle user mobility; the
1981 tunnels terminate in APN/GGSN/PGW that are in central locations.
1982 One user's traffic may flow through one or more APN's (for
1983 example Internet APN, Roaming APN for Operator X, Video-Service
1984 APN, OnDeckAPN etc.). The scope of operator private IP addresses
1985 may be limited to specific APNs. Since CDNs generally operate on
1986 user IP flows, deploying them would require enhancing them with
1987 tunnel translation, tunnel management functions etc..
1989 4. While CDNs that de-encrypt flows or split-connection proxy
1990 (similar to split-tcp) could be deployed closer to the edges to
1991 reduce control loop RTT, with transport header encryption, such
1992 CDNs perform optimization functions only for partner client
1993 flows. Therefore, content from some Small-Medium Businesses
1994 (SMBs) would not get such CDN benefits.
1996 8. Response to Increased Encryption and Looking Forward
1998 As stated in [RFC7258], "an appropriate balance (between network
1999 management and PM mitigations) will emerge over time as real
2000 instances of this tension are considered." Numerous operators made
2001 it clear in their response to this document that they fully support
2002 strong encryption and providing privacy for end users, this is a
2003 common goal. Operators recognize not all the practices documented
2004 need to be supported going forward, either because of the risk to end
2005 user privacy or alternate technologies and tools have already
2006 emerged. This document is intended to support network engineers and
2007 other innovators to work toward solving network and security
2008 management problems with protocol designers and application
2009 developers in new ways that facilitate adoption of strong encryption
2010 rather than preventing the use of encryption. By having the
2011 discussions on network and security management practices with
2012 application developers and protocol designers, each side of the
2013 debate can understand each others goals, work toward alternate
2014 solutions, and disband with practices that should no longer be
2015 supported. A goal of this document is to assist the IETF to
2016 understand some of the current practices so as to identify new work
2017 items for IETF-related use cases which can help facilitate the
2018 adoption of strong session encryption and support network and
2019 security management.
2021 9. Security Considerations
2023 There are no additional security considerations as this is a summary
2024 and does not include a new protocol or functionality.
2026 10. IANA Considerations
2028 This memo makes no requests of IANA.
2030 11. Acknowledgements
2032 Thanks to our reviewers, Natasha Rooney, Kevin Smith, Ashutosh Dutta,
2033 Brandon Williams, Jean-Michel Combes, Nalini Elkins, Paul Barrett,
2034 Badri Subramanyan, Igor Lubashev, Suresh Krishnan, Dave Dolson,
2035 Mohamed Boucadair, Stephen Farrell, Warren Kumari, Alia Atlas, Roman
2036 Danyliw, Mirja Kuhlewind, Ines Robles, Joe Clarke, Kyle Rose,
2037 Christian Huitema, and Chris Morrow for their editorial and content
2038 suggestions. Surya K. Kovvali provided material for section 7.
2039 Chris Morrow and Nik Teague provided reviews and updates specific to
2040 the DoS fingerprinting text. Brian Trammell provided the IPFIX text.
2042 12. Informative References
2044 [ACCORD] "Acord BoF IETF95
2045 https://www.ietf.org/proceedings/95/accord.html".
2047 [CAIDA] "CAIDA *Anonymized Internet Traces*
2048 [http://www.caida.org/data/overview/ and
2049 http://www.caida.org/data/passive/
2050 passive_2016_dataset.xml]".
2052 [DarkMail]
2053 "The Dark Mail Technical Aliance https://darkmail.info/".
2055 [DOTS] https://datatracker.ietf.org/wg/dots/charter/, "DDoS Open
2056 Threat Signaling IETF Working Group".
2058 [EFF2014] "EFF Report on STARTTLS Downgrade Attacks
2059 https://www.eff.org/deeplinks/2014/11/
2060 starttls-downgrade-attacks".
2062 [Enrich] Narseo Vallina-Rodriguez, et al., "Header Enrichment or
2063 ISP Enrichment, Emerging Privacy Threats in Mobile
2064 Networks, Hot Middlebox, August 17-21 2015, London, United
2065 Kingdom", 2015.
2067 [I-D.bishop-httpbis-http2-additional-certs]
2068 Bishop, M., Sullivan, N., and M. Thomson, "Secondary
2069 Certificate Authentication in HTTP/2", draft-bishop-
2070 httpbis-http2-additional-certs-05 (work in progress),
2071 October 2017.
2073 [I-D.dolson-plus-middlebox-benefits]
2074 Dolson, D., Snellman, J., Boucadair, M., and C. Jacquenet,
2075 "Beneficial Functions of Middleboxes", draft-dolson-plus-
2076 middlebox-benefits-03 (work in progress), March 2017.
2078 [I-D.ietf-dots-use-cases]
2079 Dobbins, R., Migault, D., Fouant, S., Moskowitz, R.,
2080 Teague, N., Xia, L., and K. Nishizuka, "Use cases for DDoS
2081 Open Threat Signaling", draft-ietf-dots-use-cases-09 (work
2082 in progress), November 2017.
2084 [I-D.ietf-httpbis-origin-frame]
2085 Nottingham, M. and E. Nygren, "The ORIGIN HTTP/2 Frame",
2086 draft-ietf-httpbis-origin-frame-06 (work in progress),
2087 January 2018.
2089 [I-D.ietf-tls-sni-encryption]
2090 Huitema, C. and E. Rescorla, "SNI Encryption in TLS
2091 Through Tunneling", draft-ietf-tls-sni-encryption-00 (work
2092 in progress), August 2017.
2094 [I-D.mglt-nvo3-geneve-security-requirements]
2095 Migault, D., Boutros, S., Wing, D., and S. Krishnan,
2096 "Geneve Protocol Security Requirements", draft-mglt-nvo3-
2097 geneve-security-requirements-03 (work in progress),
2098 February 2018.
2100 [IPFIX-IANA]
2101 "IP Flow Information Export (IPFIX) Entities
2102 https://www.iana.org/assignments/ipfix/".
2104 [JNSLP] Surveillance, Vol. 8 No. 3, "10 Standards for Oversight
2105 and Transparency of National Intelligence Services
2106 http://jnslp.com/".
2108 [M3AAWG] "Messaging, Malware, Mobile Anti-Abuse Working Group
2109 (M3AAWG) https://www.maawg.org/".
2111 [Nygren] https://blogs.akamai.com/2017/03/ reaching-toward-
2112 universal-tls-sni.html, "Erik Nygren, personal reference".
2114 [QUIC] https://datatracker.ietf.org/wg/quic/charter/, "QUIC
2115 (quic)".
2117 [RFC1945] Berners-Lee, T., Fielding, R., and H. Frystyk, "Hypertext
2118 Transfer Protocol -- HTTP/1.0", RFC 1945,
2119 DOI 10.17487/RFC1945, May 1996,
2120 .
2122 [RFC1958] Carpenter, B., Ed., "Architectural Principles of the
2123 Internet", RFC 1958, DOI 10.17487/RFC1958, June 1996,
2124 .
2126 [RFC1984] IAB and IESG, "IAB and IESG Statement on Cryptographic
2127 Technology and the Internet", BCP 200, RFC 1984,
2128 DOI 10.17487/RFC1984, August 1996,
2129 .
2131 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
2132 RFC 2131, DOI 10.17487/RFC2131, March 1997,
2133 .
2135 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
2136 "Definition of the Differentiated Services Field (DS
2137 Field) in the IPv4 and IPv6 Headers", RFC 2474,
2138 DOI 10.17487/RFC2474, December 1998,
2139 .
2141 [RFC2504] Guttman, E., Leong, L., and G. Malkin, "Users' Security
2142 Handbook", FYI 34, RFC 2504, DOI 10.17487/RFC2504,
2143 February 1999, .
2145 [RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address
2146 Translator (NAT) Terminology and Considerations",
2147 RFC 2663, DOI 10.17487/RFC2663, August 1999,
2148 .
2150 [RFC2775] Carpenter, B., "Internet Transparency", RFC 2775,
2151 DOI 10.17487/RFC2775, February 2000,
2152 .
2154 [RFC2804] IAB and IESG, "IETF Policy on Wiretapping", RFC 2804,
2155 DOI 10.17487/RFC2804, May 2000,
2156 .
2158 [RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering:
2159 Defeating Denial of Service Attacks which employ IP Source
2160 Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827,
2161 May 2000, .
2163 [RFC3135] Border, J., Kojo, M., Griner, J., Montenegro, G., and Z.
2164 Shelby, "Performance Enhancing Proxies Intended to
2165 Mitigate Link-Related Degradations", RFC 3135,
2166 DOI 10.17487/RFC3135, June 2001,
2167 .
2169 [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
2170 C., and M. Carney, "Dynamic Host Configuration Protocol
2171 for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
2172 2003, .
2174 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
2175 Jacobson, "RTP: A Transport Protocol for Real-Time
2176 Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
2177 July 2003, .
2179 [RFC3724] Kempf, J., Ed., Austein, R., Ed., and IAB, "The Rise of
2180 the Middle and the Future of End-to-End: Reflections on
2181 the Evolution of the Internet Architecture", RFC 3724,
2182 DOI 10.17487/RFC3724, March 2004,
2183 .
2185 [RFC3954] Claise, B., Ed., "Cisco Systems NetFlow Services Export
2186 Version 9", RFC 3954, DOI 10.17487/RFC3954, October 2004,
2187 .
2189 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
2190 "SEcure Neighbor Discovery (SEND)", RFC 3971,
2191 DOI 10.17487/RFC3971, March 2005,
2192 .
2194 [RFC4787] Audet, F., Ed. and C. Jennings, "Network Address
2195 Translation (NAT) Behavioral Requirements for Unicast
2196 UDP", BCP 127, RFC 4787, DOI 10.17487/RFC4787, January
2197 2007, .
2199 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
2200 Address Autoconfiguration", RFC 4862,
2201 DOI 10.17487/RFC4862, September 2007,
2202 .
2204 [RFC5655] Trammell, B., Boschi, E., Mark, L., Zseby, T., and A.
2205 Wagner, "Specification of the IP Flow Information Export
2206 (IPFIX) File Format", RFC 5655, DOI 10.17487/RFC5655,
2207 October 2009, .
2209 [RFC5965] Shafranovich, Y., Levine, J., and M. Kucherawy, "An
2210 Extensible Format for Email Feedback Reports", RFC 5965,
2211 DOI 10.17487/RFC5965, August 2010,
2212 .
2214 [RFC6108] Chung, C., Kasyanov, A., Livingood, J., Mody, N., and B.
2215 Van Lieu, "Comcast's Web Notification System Design",
2216 RFC 6108, DOI 10.17487/RFC6108, February 2011,
2217 .
2219 [RFC6235] Boschi, E. and B. Trammell, "IP Flow Anonymization
2220 Support", RFC 6235, DOI 10.17487/RFC6235, May 2011,
2221 .
2223 [RFC6269] Ford, M., Ed., Boucadair, M., Durand, A., Levis, P., and
2224 P. Roberts, "Issues with IP Address Sharing", RFC 6269,
2225 DOI 10.17487/RFC6269, June 2011,
2226 .
2228 [RFC6430] Li, K. and B. Leiba, "Email Feedback Report Type Value:
2229 not-spam", RFC 6430, DOI 10.17487/RFC6430, November 2011,
2230 .
2232 [RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol",
2233 RFC 6455, DOI 10.17487/RFC6455, December 2011,
2234 .
2236 [RFC6590] Falk, J., Ed. and M. Kucherawy, Ed., "Redaction of
2237 Potentially Sensitive Data from Mail Abuse Reports",
2238 RFC 6590, DOI 10.17487/RFC6590, April 2012,
2239 .
2241 [RFC6591] Fontana, H., "Authentication Failure Reporting Using the
2242 Abuse Reporting Format", RFC 6591, DOI 10.17487/RFC6591,
2243 April 2012, .
2245 [RFC6650] Falk, J. and M. Kucherawy, Ed., "Creation and Use of Email
2246 Feedback Reports: An Applicability Statement for the Abuse
2247 Reporting Format (ARF)", RFC 6650, DOI 10.17487/RFC6650,
2248 June 2012, .
2250 [RFC6651] Kucherawy, M., "Extensions to DomainKeys Identified Mail
2251 (DKIM) for Failure Reporting", RFC 6651,
2252 DOI 10.17487/RFC6651, June 2012,
2253 .
2255 [RFC6652] Kitterman, S., "Sender Policy Framework (SPF)
2256 Authentication Failure Reporting Using the Abuse Reporting
2257 Format", RFC 6652, DOI 10.17487/RFC6652, June 2012,
2258 .
2260 [RFC7011] Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
2261 "Specification of the IP Flow Information Export (IPFIX)
2262 Protocol for the Exchange of Flow Information", STD 77,
2263 RFC 7011, DOI 10.17487/RFC7011, September 2013,
2264 .
2266 [RFC7012] Claise, B., Ed. and B. Trammell, Ed., "Information Model
2267 for IP Flow Information Export (IPFIX)", RFC 7012,
2268 DOI 10.17487/RFC7012, September 2013,
2269 .
2271 [RFC7143] Chadalapaka, M., Satran, J., Meth, K., and D. Black,
2272 "Internet Small Computer System Interface (iSCSI) Protocol
2273 (Consolidated)", RFC 7143, DOI 10.17487/RFC7143, April
2274 2014, .
2276 [RFC7146] Black, D. and P. Koning, "Securing Block Storage Protocols
2277 over IP: RFC 3723 Requirements Update for IPsec v3",
2278 RFC 7146, DOI 10.17487/RFC7146, April 2014,
2279 .
2281 [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
2282 Protocol (HTTP/1.1): Message Syntax and Routing",
2283 RFC 7230, DOI 10.17487/RFC7230, June 2014,
2284 .
2286 [RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
2287 Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
2288 RFC 7234, DOI 10.17487/RFC7234, June 2014,
2289 .
2291 [RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
2292 Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
2293 2014, .
2295 [RFC7348] Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
2296 L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
2297 eXtensible Local Area Network (VXLAN): A Framework for
2298 Overlaying Virtualized Layer 2 Networks over Layer 3
2299 Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,
2300 .
2302 [RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection
2303 Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
2304 December 2014, .
2306 [RFC7457] Sheffer, Y., Holz, R., and P. Saint-Andre, "Summarizing
2307 Known Attacks on Transport Layer Security (TLS) and
2308 Datagram TLS (DTLS)", RFC 7457, DOI 10.17487/RFC7457,
2309 February 2015, .
2311 [RFC7489] Kucherawy, M., Ed. and E. Zwicky, Ed., "Domain-based
2312 Message Authentication, Reporting, and Conformance
2313 (DMARC)", RFC 7489, DOI 10.17487/RFC7489, March 2015,
2314 .
2316 [RFC7498] Quinn, P., Ed. and T. Nadeau, Ed., "Problem Statement for
2317 Service Function Chaining", RFC 7498,
2318 DOI 10.17487/RFC7498, April 2015,
2319 .
2321 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
2322 "Recommendations for Secure Use of Transport Layer
2323 Security (TLS) and Datagram Transport Layer Security
2324 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2325 2015, .
2327 [RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
2328 Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
2329 DOI 10.17487/RFC7540, May 2015,
2330 .
2332 [RFC7619] Smyslov, V. and P. Wouters, "The NULL Authentication
2333 Method in the Internet Key Exchange Protocol Version 2
2334 (IKEv2)", RFC 7619, DOI 10.17487/RFC7619, August 2015,
2335 .
2337 [RFC7624] Barnes, R., Schneier, B., Jennings, C., Hardie, T.,
2338 Trammell, B., Huitema, C., and D. Borkmann,
2339 "Confidentiality in the Face of Pervasive Surveillance: A
2340 Threat Model and Problem Statement", RFC 7624,
2341 DOI 10.17487/RFC7624, August 2015,
2342 .
2344 [RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
2345 Chaining (SFC) Architecture", RFC 7665,
2346 DOI 10.17487/RFC7665, October 2015,
2347 .
2349 [RFC7754] Barnes, R., Cooper, A., Kolkman, O., Thaler, D., and E.
2350 Nordmark, "Technical Considerations for Internet Service
2351 Blocking and Filtering", RFC 7754, DOI 10.17487/RFC7754,
2352 March 2016, .
2354 [RFC7799] Morton, A., "Active and Passive Metrics and Methods (with
2355 Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
2356 May 2016, .
2358 [RFC7826] Schulzrinne, H., Rao, A., Lanphier, R., Westerlund, M.,
2359 and M. Stiemerling, Ed., "Real-Time Streaming Protocol
2360 Version 2.0", RFC 7826, DOI 10.17487/RFC7826, December
2361 2016, .
2363 [RFC7838] Nottingham, M., McManus, P., and J. Reschke, "HTTP
2364 Alternative Services", RFC 7838, DOI 10.17487/RFC7838,
2365 April 2016, .
2367 [RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
2368 and P. Hoffman, "Specification for DNS over Transport
2369 Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
2370 2016, .
2372 [RFC8073] Moriarty, K. and M. Ford, "Coordinating Attack Response at
2373 Internet Scale (CARIS) Workshop Report", RFC 8073,
2374 DOI 10.17487/RFC8073, March 2017,
2375 .
2377 [RFC8164] Nottingham, M. and M. Thomson, "Opportunistic Security for
2378 HTTP/2", RFC 8164, DOI 10.17487/RFC8164, May 2017,
2379 .
2381 [RFC8165] Hardie, T., "Design Considerations for Metadata
2382 Insertion", RFC 8165, DOI 10.17487/RFC8165, May 2017,
2383 .
2385 [RFC8250] Elkins, N., Hamilton, R., and M. Ackermann, "IPv6
2386 Performance and Diagnostic Metrics (PDM) Destination
2387 Option", RFC 8250, DOI 10.17487/RFC8250, September 2017,
2388 .
2390 [RFC8274] Kampanakis, P. and M. Suzuki, "Incident Object Description
2391 Exchange Format Usage Guidance", RFC 8274,
2392 DOI 10.17487/RFC8274, November 2017,
2393 .
2395 [RFC8300] Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed.,
2396 "Network Service Header (NSH)", RFC 8300,
2397 DOI 10.17487/RFC8300, January 2018,
2398 .
2400 [SACM] https://datatracker.ietf.org/wg/sacm/charter/, "Security
2401 Automation and Continuous Monitoring (sacm) IETF Working
2402 Group".
2404 [Snowden] http://www.jjsylvia.com/bigdatacourse/wp-
2405 content/uploads/2016/04/p14-verble-1.pdf, "The NSA and
2406 Edward Snowden: Surveillance In The 21st Century", 2014.
2408 [TCPcrypt]
2409 https://datatracker.ietf.org/wg/tcpinc/charter/,
2410 "TCPcrypt".
2412 [TLS100Proceedings]
2413 IETF 100, TLS Working Group Session, "Presentation before
2414 the TLS WG at IETF
2415 https://datatracker.ietf.org/meeting/100/materials/
2416 slides-100-tls-sessa-tls13/", 2017.
2418 [TS3GPP] "3GPP TS 24.301, "Non-Access-Stratum (NAS) protocol for
2419 Evolved Packet System (EPS); Stage 3"", 2017.
2421 [UPCON] 3GPP, "User Plane Congestion Management
2422 http://www.3gpp.org/DynaReport/
2423 FeatureOrStudyItemFile-570029.htm", 2014.
2425 [UserData]
2426 Network and Distributed Systems Symposium, The Internet
2427 Society, "The Security Impact of HTTPS Interception",
2428 2017.
2430 Authors' Addresses
2432 Kathleen Moriarty (editor)
2433 Dell EMC
2434 176 South St
2435 Hopkinton, MA
2436 USA
2438 Phone: +1
2439 Email: Kathleen.Moriarty@dell.com
2441 Al Morton (editor)
2442 AT&T Labs
2443 200 Laurel Avenue South
2444 Middletown,, NJ 07748
2445 USA
2447 Phone: +1 732 420 1571
2448 Fax: +1 732 368 1192
2449 Email: acmorton@att.com