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INFORMATIONAL

Internet Architecture Board (IAB)                             M. Thomson
Request for Comments: 8752
Category: Informational                                    M. Nottingham
ISSN: 2070-1721                                               March 2020


   Report from the IAB Workshop on Exploring Synergy between Content
            Aggregation and the Publisher Ecosystem (ESCAPE)

Abstract

   The Exploring Synergy between Content Aggregation and the Publisher
   Ecosystem (ESCAPE) Workshop was convened by the Internet Architecture
   Board (IAB) in July 2019.  This report summarizes its significant
   points of discussion and identifies topics that may warrant further
   consideration.

   Note that this document is a report on the proceedings of the
   workshop.  The views and positions documented in this report are
   those of the workshop participants and do not necessarily reflect IAB
   views and positions.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Architecture Board (IAB)
   and represents information that the IAB has deemed valuable to
   provide for permanent record.  It represents the consensus of the
   Internet Architecture Board (IAB).  Documents approved for
   publication by the IAB are not candidates for any level of Internet
   Standard; see Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8752.

Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.

Table of Contents

   1.  Introduction
     1.1.  Mention of Specific Entities
   2.  Use Cases
     2.1.  Instant Navigation
     2.2.  Offline Content Sharing
     2.3.  Other Use Cases
       2.3.1.  Book Publishing
       2.3.2.  Web Archiving
   3.  Interactions between Web Publishers and Aggregators
     3.1.  Incentives for Web Packages
     3.2.  Operational Costs
     3.3.  Content Regulation
     3.4.  Web Performance
   4.  Systemic Effects
     4.1.  Consolidation
       4.1.1.  Consolidation of Power in Linking Sites
       4.1.2.  Consolidation of Power in Publishers
       4.1.3.  Consolidation of User Preferences
     4.2.  Effect on Web Security
     4.3.  Privacy of Content
   5.  AMP Issues Unrelated to Web Packaging
     5.1.  AMP Governance
     5.2.  Constraints on the AMP Format
     5.3.  Performance
     5.4.  Implementation of Paywalls
   6.  Venues for Future Discussion
   7.  Security Considerations
   8.  Informative References
   Appendix A.  About the Workshop
     A.1.  Agenda
       A.1.1.  Thursday 2019-07-18
       A.1.2.  Friday 2019-07-19
     A.2.  Workshop Attendees
   Appendix B.  Web Packaging Overview
     B.1.  Authority in HTTPS
     B.2.  Authority in Web Packaging
     B.3.  Applicability
     B.4.  The AMP Format, Google Search Results, and Web Packaging
   IAB Members at the Time of Approval
   Authors' Addresses

1.  Introduction

   The Internet Architecture Board (IAB) holds occasional workshops
   designed to consider long-term issues and strategies for the
   Internet, and to suggest future directions for the Internet
   architecture.  This long-term planning function of the IAB is
   complementary to the ongoing engineering efforts performed by working
   groups of the Internet Engineering Task Force (IETF).

   The IAB convened the ESCAPE Workshop to examine some proposed changes
   to the Internet and the Web, and their potential effects on the
   Internet publishing landscape.  Of particular interest was the Web
   Packaging proposal from Google, under consideration in the IETF, the
   W3C's Web Incubator Community Group (WICG), and the Web Hypertext
   Application Technology Working Group (WHATWG).

   In considering these proposals, we heard about both positive effects
   of Web Packaging and concerns that it could have significant effects
   on the relationship between publishers (e.g., news web sites) and
   content aggregators (e.g., search engines and social networks).  As
   such, our focus was primarily on this relationship, rather than
   technical discussion.

   Online publishers do not regularly participate in standards
   activities directly.  A workshop format was used to solicit input
   from them.  The workshop had 27 participants from a diverse set of
   backgrounds, including a small number of attendees from publishers,
   one aggregator (Google), plus representatives from browsers, the
   Accelerated Mobile Pages (AMP) community, Content Distribution
   Networks (CDNs), network operators, academia, and standards bodies.
   See the workshop call for papers [CFP] for more information and a
   complete listing of submissions.

   As intended, the workshop was primarily a forum for discussion, so it
   did not reach definite conclusions.  Instead, this report is the
   primary output of the workshop, as a record of that discussion.

   This report documents the use cases discussed in Section 2 and
   explains the interactions between publishers and aggregators that
   might be affected by it in Section 3.  Appendix A includes more
   details about the workshop itself.  For those unfamiliar with Web
   Packaging, Appendix B provides a summary as background material.

1.1.  Mention of Specific Entities

   Participants agreed to conduct the workshop under the Chatham House
   Rule [CHATHAM-HOUSE], so this report does not attribute statements to
   individuals or organizations without express permission.  Submissions
   to the workshop were public and thus attributable; they are used here
   to provide substance and context.

2.  Use Cases

   Much of the workshop concentrated on discussion of the validity and
   relative merits of the use cases that might be enabled by Web
   Packaging.  See Appendix B for an overview of Web Packaging.

2.1.  Instant Navigation

   The largest use of Web Packaging so far is in Google Search, where
   packages are intended to improve the perceived performance of
   navigation to pages that are linked from search results when
   "clicked".

   To enable this, when a linking (or referring) web page includes links
   to pages on another site, it also provides the browser with a
   packaged copy of the target content, signed by the origin of the
   target content.  In effect, the referring page provides a cache for
   the target page's content.  If navigation to one of those links
   occurs, having the Web Package gives a browser the assurance that the
   cache didn't change the content, so it can treat that content as if
   it were acquired directly from the server for the target page -- even
   though it came from a different server.  In many cases, this results
   in significantly lower perceived delay in displaying the target page.

   A vital characteristic of this technique is that the browser does not
   contact the target site before navigation.  The browser does not make
   any requests to sites until after navigation occurs, and only then if
   the site requires additional content or makes a request directly.

   Similar improvements could also be realized by downloading content
   (packaged or otherwise) directly from the target site through a
   technique called "prefetching".  However, doing so would reveal
   information about the user's activity on the linking page to those
   sites -- even when the user never actually navigates to it.

      |  Note: This technique that uses Web Packaging is also referred
      |  to as "privacy-preserving prefetch".  This document avoids that
      |  term as there was some contention at the workshop about which
      |  aspects of privacy might be preserved by the technique.

   Sites bundled with Web Packaging can additionally be constructed in a
   way that ensures that they render without needing any additional
   network access.  This makes it possible to provide near-instantaneous
   navigation.  The proposed changes to web navigation in support of
   loading Web Packages is designed to support this use case.

   Workshop participants recognized the value of web performance for
   usability, as well as for business metrics like retention and bounce
   rates.  Such improvements were seen as a valuable goal, but
   publishers raised questions about whether they justified the cost of
   supporting an additional format, while others raised concerns about
   different aspects of the Web Packaging proposal.

2.2.  Offline Content Sharing

   Another primary use case discussed was the ability to share web
   content between devices where neither has an active connection to the
   Internet.  One of the stated goals of Web Packaging is to enable
   sharing of content offline.

   Several participants reported that in areas where Internet access is
   expensive, slow, or intermittent, the use of direct peer-to-peer file
   exchange (e.g., "saving a website and sharing it on a USB stick") is
   commonplace.  Most web browsers already have some affordances for
   this, but these are recognized as in need of improvements.

   In the discussion, several rejected an assumed requirement of this
   use case -- that there be no difference between the treatment of a
   "normal" web page and that of one loaded from an offline Web Package.

   The ability for a Web Package to provide clear attribution for
   content was seen as valuable by some participants for a range of
   reasons.  However, reservations were expressed about the subtleties
   of the properties that signatures provide and the effect of this on
   web security; see also Sections 4.2 and 2.3.2.

   Many participants pointed out that using "unsigned bundles" -- that
   is, Web Packages without signed exchanges -- could be adequate for
   this use case, since most users don't need cryptographic proof of the
   site's identity.  However, some expressed concerns that this might
   worsen the propagation of falsehood.

   Some suggested that the value of signed exchanges was not realized in
   small-scale interpersonal exchange of information but in the building
   of systems for content delivery that might include capabilities like
   discovery and automated distribution.  The contention here was that
   effective use of digital signatures in offline distribution of
   content implied considerably more infrastructure than was described
   in current proposals.

   No definite conclusions about offline sharing were reached during the
   workshop.

2.3.  Other Use Cases

   A session on the second morning concentrated on two other significant
   potential use cases for Web Packages: book publishing and Web
   archiving.  These were not seen as "primary" by the proponents of Web
   Packaging; the original intent was not to spend significant time on
   these subjects, but there was considerable interest from attendees.

2.3.1.  Book Publishing

   The potential application of a packaging format to book publishing
   was discussed, with particular reference to ways that books differ
   from web content.  Specialists from that industry pointed out that
   book delivery can vary greatly from typical web content delivery.

   Workshop participants briefly explored existing solutions.  PDF was
   seen as particularly challenging for this use case, due to its
   limitations, and EPUB has constraints that also make it challenging
   for publishers.

   Although Web Packaging might help to address this use case, the
   question of how to identify book content was not resolved.  The use
   of signed exchanges in this context might offer means of tying
   content in books to a website, but several limitations inherent in
   doing that were identified.

   In particular, book publication specialists represented that books
   don't have the same requirements for timeliness or currency as web
   pages.  For instance, Dave Cramer's submission [CRAMER] observed that
   Moby Dick was published over 61,000 days ago, which is considerably
   longer than the proposed limit of 7 days for signed exchanges.  The
   limited length of time that a Web Package can be considered valid was
   discussed at some length.

   Additionally, the risk of a publisher going out of business during
   the lifetime of a book is significant, because books -- at least
   successful ones -- often span generations in their applicability.  To
   that end, having a means of attributing content to a publisher was
   considered less practical and potentially undesirable (much like the
   discussion above regarding "unsigned bundles").

   There were other aspects of book publication that participants saw as
   challenging for packaging.  For example, it is currently not
   understood what it means to refer to distinct parts of a book.
   Participants saw this as an area where providing stable references
   for bundles of content might offer possibilities, but nothing
   concrete came from that discussion.

   The potential for active content in a bundle to use web APIs to
   enrich content or enable new features was considered valuable.
   Models for enabling paywalls were discussed at some length (see
   Section 5.4).

2.3.2.  Web Archiving

   Web archiving is a complicated discipline that is made more difficult
   by the complex nature of the Web itself.

   From an archival standpoint, the potential for web content to be
   provided in a self-contained form was viewed positively.  Several
   improvements to the structure of Web Packaging were considered, such
   as providing complete sets of content and the use of Memento
   [MEMENTO].

   Though there were potential applications of a packaging scheme, many
   challenges were recognized as requiring additional work on the part
   of content producers to be fully effective.  For example, JavaScript
   is needed to render some archived content faithfully, but attributing
   that content to an origin in all scenarios is challenging.

   If packaging were to be widely deployed, it might improve the
   situation for archival replay.  In particular, the speculation is
   that there would be less "live leakage" as packaged content might be
   less likely to refer to live resources that currently tend to "leak"
   into views of archives.  It was also noted that subresources might
   also be more likely to be packaged, especially those that are needed
   for deferred representations (i.e., after JavaScript execution on the
   page or some user interactions).  Other potential applications and
   enhancements are discussed in [ALAM].

   Participants discussed the use of a signature for non-repudiation at
   some length.  In one case related to the Internet Archive, a public
   figure disputed the accuracy of archived content, asserting that the
   original content was modified either at the source or in the archive.

   Some participants initially saw digital signatures as a way to
   address such issues of provenance.  As similar problems exist in
   other areas, such as in book publication, medical research, and news,
   a solution to this problem was considered to have broad
   applicability.

   However, the discussion ultimately concluded that providing non-
   repudiation in retrospect is challenging.  Signing keys are not
   expected to remain secure for long periods.  If keys are leaked
   afterwards, an attacker could retroactively generate fraudulent
   signatures.  Alternative solutions were discussed, such as providing
   independent archives for the same data, using consensus protocols, or
   using an append-only construct like a Haber-Stornetta log [AOLOG],
   all of which can be used to increase the difficulty of altering or
   misrepresenting established archives.

3.  Interactions between Web Publishers and Aggregators

   A significant motivation for holding the workshop was to provide a
   forum where publishers could discuss the impact of Web Packaging on
   the online publishing ecosystem.  Of primary interest was whether Web
   Packages might effectively enable a transfer of power from publishers
   to aggregators.

   Both publishers and aggregators at the workshop expressed the
   importance of maintaining a positive relationship.  Publishers in
   particular expressed the need to be able to trust that aggregators
   won't misrepresent their work or de-emphasize it for reasons
   unrelated to quality and perceived value to the user.

   One key question from [BERJON] was discussed:

   |  Web Packaging has other uses, but it is primarily seen by a large
   |  proportion of its stakeholders as a solution to problems that AMP
   |  created.  Before we agree to solve those issues, should we not ask
   |  if AMP was a useful approach in the first place -- and useful to
   |  whom?

   In examining this issue, discussion focused on the current incentive
   model offered by aggregators.  The costs that publishers incur for
   participation in that system were considered.  Considerable time was
   spent on AMP; a summary of that discussion can be found in Section 5.

   We also considered the question of whether standardizing Web
   Packaging confers credibility to aggregators exercising unwelcome
   control over publisher content or whether the technical safeguards
   Web Packaging provides could allow aggregators to relax their
   restrictions on the kinds of content they're willing to cache and
   serve.  No conclusions were drawn.

3.1.  Incentives for Web Packages

   Submissions to the workshop indicated that the use of inducements
   involving better placement and formatting of links to publisher
   content had a significant effect on the uptake of related technology.
   For example, in [DEPUYDT-NELSON]:

   |  [...] The Washington Post has always placed a great deal of trust
   |  in Google to represent its content--and their reward for doing so
   |  is more traffic, which positively impacts the business.

   During the workshop, several online publishers indicated that if it
   weren't for the privileged position in the Google Search carousel
   given to AMP content, they would not publish in that format.

   Publishers that do produce AMP said they see a non-trivial increase
   in traffic as a result of deploying AMP content.  For example, Yahoo
   Japan reported a 60% increase in traffic as a result of deploying AMP
   on Yahoo Travel [OTSU].  There was no data presented as to whether
   this increase was due to better placement in Google Search results,
   the inherent benefits of the AMP Cache, or the use of the AMP format.

   Anecdotal evidence was offered by another large publisher that saw a
   10% drop in traffic as a result of accidentally disabling AMP
   content.  However, increases in traffic might not result in similarly
   proportioned increases in revenue, as observed in [BREWSTER].

3.2.  Operational Costs

   Several participants pointed out that introducing a new, parallel
   format for Web content incurs operational costs.  In particular,
   supporting any new format -- such as Web Packaging, Apple News, or
   Facebook Instant Articles -- requires not only initial development of
   tooling (some generic and some specific to a site's requirements) but
   also an ongoing investment in maintaining its operability.  Some
   participants expressed concern about the impact upon small publishers
   with limited technical and financial resources, especially in the
   current publishing climate.

   Increased exposure from new formats might not always justify the
   added expense of providing articles in that format [BREWSTER].
   However, a standardized format might help publishers reduce the cost
   of maintaining multiple formats.

3.3.  Content Regulation

   The use of Web Packaging as a tool for avoiding censorship was not a
   significant topic of discussion, except to note that publishers often
   have regulatory requirements regarding removal or correction of
   content.

   Reference was made to the desire to remove videos of a recent
   shooting [CHRISTCHURCH] and the potential difficulty in doing so if
   content were available as Web Packages.  Legal requirements to remove
   content come from multiple angles: copyright violations, illegal
   content, editorial corrections or errors, and right to erasure
   provisions in the European Union General Data Protection Regulation
   [GDPR] were mentioned.  One participant speculated that making it
   more difficult to remove material in this way might discourage
   regulators from censoring content.

   In this context, participants observed that it would be difficult to
   create mechanisms to track and control content served as a Web
   Package without compromising the stated goal of censorship
   resistance.

3.4.  Web Performance

   Understanding the effect that Web Packaging might have on web
   performance was a matter of some contention.

   Some informal analysis from the Google Search deployment was
   presented (later published in [AMP-PERF]) that showed significant
   performance improvements in metrics related to navigation time
   resulting from the combination of prefetch, prerendering, and the AMP
   format.  These results are suggestive of a possibility that Web
   Packaging could provide some of that improvement on its own, but no
   data was presented that apportioned the improvement among the three
   components.

   Though data was presented to demonstrate potential rather than be a
   definitive result, discussions raised a number of questions that
   suggest the need for further study.  Attendees suggested that future
   measurements consider the effect of signed bundles distinct from the
   enhancements derived from the AMP format.  Future research in this
   area might also consider the effectiveness of different strategies on
   devices with varying capabilities, bandwidth, power consumption
   requirements, or network conditions.

   Of particular interest is the additional work required to fetch and
   render multiple web pages in preparation for navigation.  This might
   ultimately use fewer connections but comes with an increased network
   and CPU cost for clients.  Some participants pointed out that
   different clients or applications might require different tuning --
   for example, when users have limited (or expensive) bandwidth or for
   sites with less clear knowledge about the use of outbound links.

   Workshop participants also expressed interest in learning about the
   effect of Web Packages on subsequent navigations within the target
   site.

   In discussion, some participants suggested that their experience
   supported a theory that operating a cache at the linking site was
   most effective and the additional work done prior to navigation in
   terms of fetching and preparing content was what provided the most
   gains; others suggested that the benefits inherent in the AMP format
   was a dominant factor.

   Understanding the complete effect of Web Packaging on web performance
   will require further work.

4.  Systemic Effects

   It is not straightforward to estimate how a proposed technology
   change might affect all of the parts of a system -- including not
   only other components, but also things like end-user rights and the
   balance of power between parties -- ahead of time.  To date, when
   evaluating proposals, the IETF has generally focused on more
   immediate concerns, such as interoperability and security.

   Moreover, people often find new uses for successful standards
   [SUCCESS] after they are deployed.  It is rarely possible to
   accurately predict all applications of a protocol or format, whether
   they are harmful or beneficial.  Refusing standardization only
   impedes both outcomes.

   With the understanding that predictions are difficult to make, there
   was considerable speculation at the workshop about the possible
   effect of Web Packaging on the Web. Some of that speculation is
   informed by experience, but that experience is necessarily limited in
   scope.  This section attempts to capture that discussion.

4.1.  Consolidation

   Concerns about the consolidation of power on the Internet have
   significantly increased lately, as a result of several factors.
   While the IAB, the Internet Society, and others are examining this
   phenomenon to understand it better, it is nevertheless prudent to
   consider whether proposals for changes to how the Internet works
   favors or counters consolidation.  Favoring entities with existing
   advantages -- like resources, size, or market share -- is not
   necessarily a factor that disqualifies a new proposal, but it needs
   to be considered as a cost of enabling that technology.

   Although the outcomes of adopting Web Packaging are unclear, the
   workshop revealed several concerns for consolidation risks for all
   involved parties: users, publisher sites, linking sites, and services
   they each rely on.

4.1.1.  Consolidation of Power in Linking Sites

   Several participants noted that Web Packaging's enabling of instant
   navigation (Section 2.1) might advantage larger linking sites -- such
   as social networks or search engines -- over smaller ones in the same
   industry because doing so requires careful selections of which links
   to optimize, so as not to create unneeded traffic.

   For example, a news article often has many links, but not all of them
   are equally likely to be followed.  Deciding which ones to prefetch
   requires considerable data collection and engineering, so this
   technique might not be feasible for smaller entities.  Additionally,
   some participants noted that this technique favors sites that have a
   linear set of ranked links, like search results; it is more difficult
   to apply to a page of news (for example) because predicting what link
   a user will follow is less obvious.

   This technique also requires access to a cache with terms of use
   compatible with the requirements of the site.  It was pointed out
   that the Google AMP Cache has policies that might be acceptable to
   many, and there are other caches.  Sites operated by entities other
   than Google already use this cache, though it was observed that a
   site that does not host its own cache suffers a minor performance
   degradation.

4.1.2.  Consolidation of Power in Publishers

   Participants seemed to agree that if performance is a strong enough
   differentiator, the effective use of Web Packaging might turn out to
   be a condition for success for online publishers.  Google Search's
   choice to privilege content that is served using HTTPS was pointed
   out as showing that this sort of influence can be effective.
   Equally, it is not necessarily the case that standardization of new
   capabilities will affect such policies materially, as noted in
   [YASSKIN]:

   |  It seems unlikely that any decisions we make in a packaging or
   |  distribution system will affect the considerations aggregators use
   |  when deciding how to rank recommendations or the power this gives
   |  them over publishers.

   The most common concern raised in the discussion was the effect of
   this technology on smaller publishers who might be less able to
   optimize the packages they produce, where their primary
   differentiation in the market has previously been the quality of
   their content.

4.1.3.  Consolidation of User Preferences

   In typical operation of the Web, servers have an opportunity to
   tailor content to the needs of their users.  In contrast, a static
   Web Package has few options for individualization, as the content is
   generated once and used by many.

   As a result, publishers noted that AMP provides less opportunity to
   customize content for their customers.  Their concerns included not
   only personalizing content based on what they know about the user but
   also optimizing the package for specific browsers.  Other
   participants observed in relation to this that Web Packaging might
   also have a consolidating effect in the browser market.

   Some participants brought up the possibility of customization by
   providing multiple packages, including multiple variants of resources
   in a single package, or performing customization after the package
   was loaded.  However, other participants pointed out that all of
   these options have negative side effects, either in complexity or
   reduced performance arising from larger bundles or delayed
   customization.

4.2.  Effect on Web Security

   One session explored the impact of introducing a new security model
   for the Web. Currently, sites rely on connection-oriented security
   (provided by TLS [TLS]), but Web Packaging adds a limited form of
   object security.  That is, the package protects the integrity of a
   message, rather than providing integrity and confidentiality for its
   delivery.  Object security is not a new concept in the context of the
   Web; designs like SHTTP [SHTTP] are as old as HTTPS.  Though the
   intent is for Web Packaging to have a far more narrow applicability,
   it provides fewer security guarantees than HTTPS, since it provides
   only authentication, no confidentiality with respect to the cache,
   and no assurance of liveness.

   Object-based security -- such as proposed in Web Packaging -- allows
   the use of content regardless of how it is obtained; some
   participants noted that third parties gain greater control over the
   distribution of content, reducing the ability of publishers to
   retract or alter content over the validity period of signed content.

   Another topic of discussion was composition attacks.  In its proposed
   form, Web Packaging only provides authentication of independent
   resources, not a web page as a single unit, allowing an attacker to
   control the composition of resources.  This weakness was acknowledged
   as a known shortcoming of the current proposal that would be
   addressed.

   The issue of managing the trade-off between control and performance
   in caches arose.  While participants recognized that problems with
   resource composition already occur by accident -- for example, when a
   cache stores different versions of resources -- Web Packaging allows
   an attacker more direct control over what resources are available to
   clients.

   For example, an attacker might be able to cause content with a
   security flaw to be used up to a week past the time that the defect
   was fixed.

   As an example of how Web Packaging might change the risk profile for
   sites, participants discussed recovery from cross-site scripting
   attacks.  It is already the case that a brief exposure to this class
   of attack can result in an attacker gaining persistent access, but
   mechanisms exist that can be used to avoid or correct issues, like
   cache validation and Clear Site Data [CLEAR-DATA].  These measures
   are not available to clients unless they connect to the site.

   The discussion pointed out that these concerns are not new or
   uniquely enabled by Web Packaging.  However, it was pointed out that
   new features are routinely subject to higher security and privacy
   expectations.  In an example unrelated to Web Packaging but with
   similar trade-offs, shared compression of multiple resources has
   significant performance benefits.  The risk with shared compression
   is the potential for exposing encrypted information through side
   channels.  Though sites can use shared compression without this
   exposure, shared compression will likely only be enabled once it is
   clear that measures to prevent accidental information exposure are
   understood to be effective in a broad set of deployments.

   The discussion also addressed the question of whether concerns might
   equally apply to the typical use of a CDN as a third-party provider
   of the content.  Some participants concluded that CDNs are typically
   in a contractual relationship with the sites they serve and so are
   more likely to have their interests aligned.

4.3.  Privacy of Content

   Discussion and submissions raised concerns regarding how serving
   content using Web Packages might adversely affect privacy of
   individuals.  There are challenges here, but the very narrow
   applicability of Web Packaging to what is effectively static content
   limits the privacy risk.  The conclusion was that, provided
   sufficient care is taken in implementation, the use of Web Packages
   does not substantially increase the information that an aggregator
   gains about what content is consumed.

   Concretely, an aggregator knows what content it serves in
   anticipation of navigation.  This is -- at least in theory --
   substantially the same as the content that the aggregator might
   receive if it performed the navigation itself.  Assuming that content
   is stripped of personalization, the aggregator gains no new
   information.

5.  AMP Issues Unrelated to Web Packaging

   On multiple occasions, discussion at the workshop concentrated on
   problems that arise as a result of constraints on the AMP format or
   details of its inclusion in Google Search.  For instance, the
   requirement to make pages expose their metadata is unlikely to be
   affected by any standardization of a packaging format as that
   requirement is independent of the process of delivering content.

   This section provides some detail on aspects of the discussion that
   touched on AMP more generally in this way.  Some treatment of these
   points is considered relevant as some of the discussion at the
   workshop, even under the remit of discussing Web Packaging,
   concentrated on the effect of AMP on the ecosystem.

      |  Note: Of the four formats mentioned in the workshop call for
      |  papers [CFP], only AMP sent representatives to the workshop.
      |  The discussion was therefore concentrated around AMP; this
      |  section should not be read to imply anything about other
      |  formats.

   Discussion and submissions referred to a commitment [AMP-LESSONS] to
   allow publishers to use content that met specific criteria to access
   privileged positions in search results, regardless of their adoption
   of AMP.  Participants felt that this approach might address some of
   these concerns if it were adopted and durable.  For instance, the use
   of Web Packaging might be sufficient to remove some constraints on
   active content on the basis that the active content would be
   attributed to the publisher and not the AMP Cache.

5.1.  AMP Governance

   There was interest from workshop participants in the governance model
   used for AMP.  In particular, the question of how independent the AMP
   project would be of Google and Google Search arose.

   Three of the seven members of the AMP Technical Steering Committee,
   the body that governs AMP, are Google employees, which gives Google
   considerable influence over the project.  It was asserted that the
   governance structure was intended to be more independent of Google
   over time.  The understanding was that any consumer of the format,
   such as Google Search, would make an independent assessment about
   whether to use or require different aspects of the AMP project
   products.

5.2.  Constraints on the AMP Format

   Sites often implement AMP by creating a separate set of content in
   parallel to their regular HTML content.  Publishers noted this as a
   high cost, particularly for smaller sites.  It was pointed out that
   websites can serve AMP-compliant content exclusively.  However,
   several publishers referred to limitations in the format that made it
   unsuitable for their needs.

   Many cited reasons for this duplication were related to the necessity
   of running arbitrary active content (typically, JavaScript).  For
   example:

   *  AMP provides a framework for supporting user authentication, but
      publishers asserted that using this framework was not considered
      practical.

   *  AMP content does not support rendering of certain content, which
      can affect the ability of publishers to innovate content
      production.

   *  The AMP model for the implementation of paywalls (Section 5.4) was
      claimed to be inimical to some publisher business models.

   More broadly, they considered AMP's constraints on the use of active
   content as problematic, since they prevent the use of capabilities
   that are provided on equivalent non-AMP pages.  Reference was made to
   a proposed <amp-script> element -- which has since been made fully
   available -- that seeks to provide limited access to some dynamic
   content.

5.3.  Performance

   Publishers observed that using the AMP format does not provide any
   guarantee of performance gains and, in some cases, could contribute
   to performance degradation.  It was suggested that this was most
   problematic for sites that are already well-tuned for performance.

5.4.  Implementation of Paywalls

   The use of paywalls by web publishers to control access to content in
   return for payment is increasingly common.  One popular approach is
   to offer a limited number of articles without payment while insisting
   on a paid subscription to access further articles.

   On several occasions, participants expressed dissatisfaction with the
   difficulty of integrating paywall authorization when using AMP.  In
   particular, they said AMP encourages publishers to include an
   article's full content, hidden by default but easily accessible to
   motivated users.  The discussion extended to workarounds like cookie
   syncing [COOKIE-SYNC], which is used as part of authorization and is
   a consequence of having cached content hosted on the linking site
   rather than the target site.

   The same topic came up concerning book publication, where publishers
   indicated that having a means of enabling different methods of
   distribution without also facilitating unconstrained copying of book
   content was necessary.

   This conflation of AMP issues with those addressed by Web Packaging
   was recurrent in the discussion.  As observed in [DAS], these
   concerns might be addressed by linking to a signed bundle.

6.  Venues for Future Discussion

   Web Packaging work continues in multiple forums.  Questions about the
   core format and signatures are being discussed on the wpack@ietf.org
   mailing list (https://www.ietf.org/mailman/listinfo/wpack).  Changes
   to web browsers as proposed in [LOADING] will be discussed on the
   Fetch specification repository (https://github.com/whatwg/fetch/
   issues/784).

7.  Security Considerations

   Proposals discussed at the workshop might have a significant security
   impact, and these topics were discussed in some depth; see
   Section 4.2.

8.  Informative References

   [ALAM]     Alam, S., Weigle, M., Nelson, M., Klein, M., and H. Van de
              Sompel, "Supporting Web Archiving via Web Packaging", 6
              June 2019, <https://www.iab.org/wp-content/IAB-
              uploads/2019/06/sawood-alam-2.pdf>.

   [AMP-LESSONS]
              Ubl, M., "Standardizing lessons learned from AMP", 8 March
              2018, <https://blog.amp.dev/2018/03/08/standardizing-
              lessons-learned-from-amp/>.

   [AMP-PERF] Steinlauf, E., "The Speed Benefit of AMP Prerendering", 14
              August 2019, <https://developers.googleblog.com/2019/08/
              the-speed-benefit-of-amp-prerendering.html>.

   [AOLOG]    Haber, S. and W. Stornetta, "How to time-stamp a digital
              document", Journal of Cryptology, Vol. 3, Issue 2, pp.
              99-111, DOI 10.1007/bf00196791, 1991,
              <https://doi.org/10.1007/bf00196791>.

   [BERJON]   Berjon, R., "ESCAPE: The New York Times Position", 9 July
              2019, <https://www.iab.org/wp-content/IAB-uploads/2019/07/
              NYT-ESCAPE.pdf>.

   [BREWSTER] Brewster, A., "ESCAPE Position / Patch.com", 6 June 2019,
              <https://www.iab.org/wp-content/IAB-uploads/2019/06/
              patch.pdf>.

   [BUNDLE]   Yasskin, J., "Bundled HTTP Exchanges", Work in Progress,
              Internet-Draft, draft-yasskin-wpack-bundled-exchanges-02,
              26 September 2019, <https://tools.ietf.org/html/draft-
              yasskin-wpack-bundled-exchanges-02>.

   [CFP]      Internet Architecture Board, "Exploring Synergy between
              Content Aggregation and the Publisher Ecosystem Workshop
              2019", 3 May 2019,
              <https://www.iab.org/activities/workshops/escape-
              workshop/>.

   [CHATHAM-HOUSE]
              Chatham House, "Chatham House Rule",
              <https://www.chathamhouse.org/chatham-house-rule>.

   [CHRISTCHURCH]
              Stevenson, R. and J. Anthony, "'Thousands' of Christchurch
              shootings videos removed from YouTube, Google says", 16
              March 2019, <https://www.stuff.co.nz/business/111330323/
              facebook-working-around-the-clock-to-block-christchurch-
              shootings-video>.

   [CLEAR-DATA]
              West, M., "Clear Site Data", W3C Working Draft, 30
              November 2017, <https://www.w3.org/TR/clear-site-data/>.

   [COOKIE-SYNC]
              Acar, G., Eubank, C., Englehardt, S., Juarez, M.,
              Narayanan, A., and C. Diaz, "The Web Never Forgets", CSS
              '14: Proceedings of the 2014 ACM SIGSAC Conference on
              Computer and Communications Security, pp. 674-689,
              DOI 10.1145/2660267.2660347, 2014,
              <https://doi.org/10.1145/2660267.2660347>.

   [CRAMER]   Cramer, D., "Packaging Books", 2 June 2019,
              <https://www.iab.org/wp-content/IAB-uploads/2019/06/
              cramer-position-paper.pdf>.

   [DAS]      Das, S., "The Implication of Signed Exchanges on
              E-Commerce", 7 June 2019, <https://www.iab.org/wp-content/
              IAB-uploads/2019/06/IAB-Position-Paper_-Signed-
              Exchanges.pdf>.

   [DEPUYDT-NELSON]
              DePuydt, M. and M. Nelson, "Signed Exchanges and The
              Importance of Trust in Aggregator/Publisher
              relationships", 4 June 2019, <https://www.iab.org/wp-
              content/IAB-uploads/2019/06/washpost.pdf>.

   [GDPR]     European Union, "General Data Protection Regulation", EU
              Regulation 2016/679, 27 April 2016, <https://eur-
              lex.europa.eu/legal-content/EN/TXT/
              HTML/?uri=CELEX:32016R0679&from=EN#d1e2606-1-1>.

   [HTTP]     Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,
              <https://www.rfc-editor.org/info/rfc7230>.

   [LOADING]  Yasskin, J., "Loading Signed Exchanges", 4 September 2019,
              <https://wicg.github.io/webpackage/loading.html>.

   [MEMENTO]  Van de Sompel, H., Nelson, M., and R. Sanderson, "HTTP
              Framework for Time-Based Access to Resource States --
              Memento", RFC 7089, DOI 10.17487/RFC7089, December 2013,
              <https://www.rfc-editor.org/info/rfc7089>.

   [ORIGIN]   Barth, A., "The Web Origin Concept", RFC 6454,
              DOI 10.17487/RFC6454, December 2011,
              <https://www.rfc-editor.org/info/rfc6454>.

   [OTSU]     Ohtsu, S., "Deployment Experience of Signed HTTP Exchanges
              with AMP as a Publisher", 4 June 2019,
              <https://www.iab.org/wp-content/IAB-uploads/2019/06/
              shigeki-ohtsu.pdf>.

   [SHTTP]    Rescorla, E. and A. Schiffman, "The Secure HyperText
              Transfer Protocol", RFC 2660, DOI 10.17487/RFC2660, August
              1999, <https://www.rfc-editor.org/info/rfc2660>.

   [SUCCESS]  Thaler, D. and B. Aboba, "What Makes for a Successful
              Protocol?", RFC 5218, DOI 10.17487/RFC5218, July 2008,
              <https://www.rfc-editor.org/info/rfc5218>.

   [SXG]      Yasskin, J., "Signed HTTP Exchanges", Work in Progress,
              Internet-Draft, draft-yasskin-http-origin-signed-
              responses-08, 4 November 2019,
              <https://tools.ietf.org/html/draft-yasskin-http-origin-
              signed-responses-08>.

   [TAG-DC]   Betts, A., Ed., "Distributed and syndicated content", W3C
              TAG Finding, 27 July 2017,
              <https://www.w3.org/2001/tag/doc/distributed-content/>.

   [TLS]      Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [YASSKIN]  Yasskin, J., "Chrome's position on the ESCAPE workshop", 6
              June 2019, <https://www.iab.org/wp-content/IAB-
              uploads/2019/06/chrome.html>.

Appendix A.  About the Workshop

   The ESCAPE Workshop was held on 2019-07-18 and the morning of
   2019-07-19 at Cisco's facility in Herndon, Virginia, USA.

   Workshop attendees were asked to submit position papers.  These
   papers are published on the IAB website [CFP].

   The workshop was conducted under the Chatham House Rule
   [CHATHAM-HOUSE], meaning that statements cannot be attributed to
   individuals or organizations without explicit authorization.

A.1.  Agenda

   This section outlines the broad areas of discussion on each day.

A.1.1.  Thursday 2019-07-18

   Web Packaging Overview:  A technical summary of Web Packaging was
      provided, plus a longer discussion of a range of use cases.

   Web Packaging and Aggregators:  The use of Web Packaging from the
      perspective of a content aggregator was given.

   Web Packaging and Publishers:  After a break, presentations from web
      publishers talked about the benefits and costs of Web Packaging.
      This included some discussion of the effect of developing AMP-
      conformant versions of content from a publisher perspective.

   Web Packaging and Security:  This session concentrated on how the Web
      Packaging proposal might affect the web security model.

   Alternatives to Web Packaging:  This session looked at alternative
      technologies, including those that were attempted in the past and
      some more recent ideas for addressing the use case of making web
      navigations more performant.

A.1.2.  Friday 2019-07-19

   Web Archival:  This session talked about the potential application of
      a technology like Web Packaging in addressing some of the myriad
      problems faced by web archival systems.

   Book Publishing:  The effect of technologies for bundling and
      distribution of books was discussed.

   Conclusions:  A wrap-up session attempted to capture key takeaways
      from the workshop.

A.2.  Workshop Attendees

   Attendees of the workshop are listed with their primary affiliation
   as it appeared in submissions.  Attendees from the program committee
   (PC), the Internet Architecture Board (IAB), and the Internet
   Engineering Steering Group (IESG) are also marked.

   *  Sawood Alam, Old Dominion University
   *  Jari Arkko, Ericsson (IAB)
   *  Richard Barnes, Cisco
   *  Robin Berjon, New York Times (PC)
   *  Zack Bloom, Cloudflare
   *  Abraham Brewster, Patch.com
   *  Alissa Cooper, Cisco (IESG, IAB)
   *  Dave Cramer, Hachette Book Group
   *  Melissa DePuydt, Washington Post
   *  Levi Durfee, AMP Advisory Committee
   *  Rudy Galfi, Google
   *  Joseph Lorenzo Hall, Center for Democracy & Technology (PC)
   *  Matthew Nelson, Washington Post
   *  Michael Nelson, Old Dominion University
   *  Mark Nottingham, Fastly (IAB, PC)
   *  Shigeki Ohtsu, Yahoo
   *  Eric Rescorla, Mozilla
   *  Adam Roach, Mozilla (IESG)
   *  Rich Salz, Akamai Technologies
   *  Wendy Seltzer, W3C
   *  David Strauss, Pantheon (PC)
   *  Chi-Jiun Su, Hughes
   *  Ralph Swick, W3C
   *  Martin Thomson, Mozilla (IAB, PC)
   *  Jeffrey Yasskin, Google
   *  Dan York, Internet Society
   *  Benjamin Young, John Wiley & Sons

Appendix B.  Web Packaging Overview

   Web Packaging is comprised of two separate technologies: resource
   bundling [BUNDLE] and signed exchanges [SXG].

   In both the submissions and workshop discussion, the most
   controversial aspect of the technology is the use of signed exchanges
   as an alternative means of providing authority over a particular
   resource, for a few different reasons.

   This appendix explains how authority works on the Web and how Web
   Packaging proposes to change that.

B.1.  Authority in HTTPS

   The Web currently uses HTTPS [HTTP] to establish a server's authority
   -- that is, to give an assurance that the content came from where the
   URL implies.  The combination of URI scheme (https), domain name (or
   host), and port number are formed into a single identifier, the
   origin [ORIGIN] to which content is attributed.

   Web browsers use the certificate offered as part of a TLS connection
   [TLS] to servers in determining whether a server is authoritative for
   that origin; see [ORIGIN] and Section 9.1 of [HTTP].  Content is
   attributed to a given URL only if it is received from a connection to
   a server that is authoritative for the associated origin.

   As an example, a web browser seeking to load "https://example.com/
   index.html" makes a TLS connection to a server.  As part of the TLS
   connection establishment, the server offers a certificate for the
   name "example.com".  If the browser accepts the certificate, it will
   then make requests for URLs on the "https://example.com" origin on
   that connection and consider any answers from the server to be
   authoritative.

   This notion of authority is a crucial property of web security: only
   content that is attributed to the same web origin can access all
   information in that origin, including the content of most resources
   as well as state associated with the origin, such as cookies.  This
   separation ensures that sites can keep secrets from each other, even
   when they are both loaded in the same browser.

B.2.  Authority in Web Packaging

   Web Packaging, through the use of signed exchanges, aims to provide
   an alternative means of establishing authority.  A signed exchange is
   an expression of an HTTP request and response (an exchange) with
   certain information stripped and a digital signature applied.

   The signature is made with a similar certificate to the one a server
   might offer in HTTPS -- that certificate can also be used for HTTPS
   -- but it includes a special attribute that denotes its suitability
   for signed exchanges.

   A web browser that has been provided with a signed exchange can
   verify the signature and, if the signature is valid and the
   certificate is acceptable, use the content from the signed exchange.
   Critically, the web browser does not make an HTTPS connection to a
   server to get the content or to verify the signature.

   In effect, Web Packaging moves from a model where authority is
   derived from the delivery method (i.e., TLS) to an object security
   model, where authority is derived from a signature on objects.  In
   doing so, it aims to render the means of delivery irrelevant to
   determinations of security.

B.3.  Applicability

   Web Packaging does not claim to supplant the authority model of the
   Web completely, but it does provide an alternative that might be used
   under certain narrow conditions.  In particular, Web Packaging is
   intended for use with content that is not secret from an entity that
   is aware of the existence of that content.

   In aid of this goal, Web Packaging does not include information from
   exchanges that is related to the process of acquiring content nor
   does it include any information that is related to individual
   requests.  For instance, use of the Set-Cookie header field is
   expressly forbidden, as it often contains information that is related
   to a particular user.

B.4.  The AMP Format, Google Search Results, and Web Packaging

   The relationship between the AMP Project <https://amp.dev/> and Web
   Packaging is complicated.  The AMP Project, sponsored by Google,
   establishes a profile of HTML with a stated goal of providing support
   for the best practices for the format, with a strong emphasis on
   performance.  The format tightly constrains the use of HTML features
   but also offers a library of components that provide sanitized
   implementations of many commonly used capabilities.

   The connection to Web Packaging is bound up in the way that Google
   Search treats AMP content specially.  AMP content provides two
   properties that Google Search exploits: metadata exposure and static
   analysis of active content.

   AMP content provides metadata in a form that can be reliably
   extracted, using the microformats defined by the Schema.org project
   <https://schema.org/>.  This aspect of AMP has no effect on the
   discussion, except to the extent that this relates to Google Search
   and their use of this metadata in populating the carousel.

   Constrained use of active content -- such as JavaScript -- in AMP
   makes it possible to analyze content to verify that actions taken are
   narrowly limited.  This static analysis assures that AMP content can
   be served without affecting other content on the same site.  For
   Google Search, this is what enables the loading of AMP content
   alongside search content and other AMP resources.

   To provide preloading, Google operates the Google AMP Cache
   <https://developers.google.com/amp/cache/>, from which AMP content is
   served.  As a consequence, browsers attribute the content to the
   origin [ORIGIN] of the AMP Cache and not the publisher, creating some
   confusion about how content is attributed, as discussed in the W3C
   finding on distributed content [TAG-DC].

   An important goal of Web Packaging is to attribute content loaded
   from a cache, such as the Google AMP Cache, to the publisher that
   created that content.  For more on this, see Section 2.1.

IAB Members at the Time of Approval

   Internet Architecture Board members at the time this document was
   approved for publication were:

      Jari Arkko
      Alissa Cooper
      Stephen Farrell
      Wes Hardaker
      Ted Hardie
      Christian Huitema
      Zhenbin Li
      Erik Nordmark
      Mark Nottingham
      Melinda Shore
      Jeff Tantsura
      Martin Thomson
      Brian Trammell

Authors' Addresses

   Martin Thomson

   Email: mt@lowentropy.net


   Mark Nottingham

   Email: mnot@mnot.net


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