\
Open Pluggable Edge Services                                   A. Barbir
Internet-Draft                                           Nortel Networks
Expires: December 11, 2003                                   A. Rousskov
                                                 The Measurement Factory
                                                           June 12, 2003


                  OPES Treatment of IAB Considerations
                         draft-ietf-opes-iab-00

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
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   The list of current Internet-Drafts can be accessed at http://
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   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on December 11, 2003.

Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.

Abstract

   IETF Internet Architecture Board (IAB) expressed nine
   architecture-level considerations when Open Pluggable Edge Services
   (OPES) working group was being chartered at the IETF.  The working
   group was chartered under the condition that IAB considerations were
   addressed by the group. This document describes how OPES addresses
   those considerations.








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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Consideration (2.1) One-party consent  . . . . . . . . . . . .  5
   4.  Consideration (2.2) IP-layer communications  . . . . . . . . .  6
   5.  Notification Considerations  . . . . . . . . . . . . . . . . .  8
   5.1 Consideration (3.1) Notification . . . . . . . . . . . . . . .  9
   5.2 Consideration (3.2) Notification . . . . . . . . . . . . . . . 10
   5.3 Consideration (3.3) Non-blocking . . . . . . . . . . . . . . . 11
   6.  Consideration (4.1) URI resolution . . . . . . . . . . . . . . 12
   7.  Consideration (4.2) Reference validity . . . . . . . . . . . . 13
   8.  Consideration (4.3) Addressing extensions  . . . . . . . . . . 14
   9.  Consideration (5.1) Privacy  . . . . . . . . . . . . . . . . . 15
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   11. Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . 17
   12. To-do  . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
   A.  Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 19
       Normative References . . . . . . . . . . . . . . . . . . . . . 20
       Informative References . . . . . . . . . . . . . . . . . . . . 21
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 21
       Intellectual Property and Copyright Statements . . . . . . . . 22





























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1. Introduction

   The Open Pluggable Edge Services (OPES) architecture
   [I-D.ietf-opes-architecture], enables cooperative application
   services (OPES services) between a data provider, a data consumer,
   and zero or more OPES processors.  The application services under
   consideration analyze and possibly transform application-level
   messages exchanged between the data provider and the data consumer.

   Following controversy related to chartering OPES, IAB made
   recommendations on issues that OPES solutions should be required to
   address. These recommendations were formulated in the form of
   specific IAB considerations [RFC3238].  IAB emphasized that its
   considerations did not recommend specific solutions and did not
   mandate specific functional requirements. Addressing an IAB
   consideration may involve showing appropriate protocol mechanisms or
   demonstrating that the issue does not apply.

   The primary goal of this document is to show that all IAB
   considerations are addressed by OPES, to the extent those
   considerations can be addressed by an IETF working group.  We also
   explicitly document limitations of our abilities to address certain
   aspects of IAB considerations.

   There are nine IAB considerations [RFC3238] that OPES has to address.
   In the core of this document are the corresponding nine
   "Consideration" sections. For each IAB consideration, its section
   contains general discussion as well as references to specific OPES
   mechanisms relevant to the consideration.






















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2. Terminology

   This document does not introduce any new terminology but uses
   terminology from other OPES documents it quotes.















































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3. Consideration (2.1) One-party consent

   "An OPES framework standardized in the IETF must require that the use
   of any OPES service be explicitly authorized by one of the
   application-layer end-hosts (that is, either the content provider or
   the client)."[RFC3238]

   OPES architecture requires that "OPES processors MUST be consented to
   by either the data consumer or data provider application"
   [I-D.ietf-opes-architecture]. The requirement alone cannot prevent
   consent-less introduction of OPES processors, of course.  OPES
   enables concerned parties to detect unwanted OPES processors by
   examining OPES traces and by checking content signatures.

   Tracing is a weak but cheap mechanism that is unable to detect
   processors incompliant with OPES specifications on tracing and
   operating in stealth mode. Content signatures is a strong but
   expensive mechanism that can detect any modifications of signed
   content provided the content provider is willing to sign the data and
   the client is willing to either check the signature or relay received
   content to content provider for signature verification.

   OPES adaptations include copying and other forms of non-modifying
   access to content. These kinds of adaptations cannot be detected by
   the above mentioned mechanisms. Thus, "passive" unwanted OPES
   processors cannot be detected. If presence of such processors is a
   concern, content encryption can be used. See privacy consideration
   for more details.























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4. Consideration (2.2) IP-layer communications

   "For an OPES framework standardized in the IETF, the OPES
   intermediary must be explicitly addressed at the IP layer by the end
   user."[RFC3238]

   OPES architecture requires that "OPES processors MUST be addressable
   at the IP layer by the end user (data consumer application)"
   [I-D.ietf-opes-architecture]. Two caveats are related to this
   requirement. First, addressing the first OPES processor in a chain of
   processors is sufficient. That is, a chain of OPES processors is
   viewed as a single OPES processor at the address of the first chain
   element.  (XXX: should we move these caveats into a separate section?
   they seem to affect many considerations; one the other hand, it is
   probably the job of the architecture draft to define these things so
   that we can refer to them from here.)

   The second caveat is more controversial. Only a very limited subset
   of OPES intermediaries are subject to the above requirements. The
   situation is examined below, by considering content provider and end
   user sides of the architecture.

   OPES processors that operate under content provider consent may not
   be subject to the above consideration and requirement (XXX the
   architecture draft does not reflect this). It is irrational to expect
   a content provider to provide access to internal hosts participating
   in content generation, whether OPES processors are involved or not.
   Moreover, providing such access would serve little practical purpose
   because internal OPES processors are not likely to be able to answer
   any end user queries, being completely our of content generation
   context. For example, an OPES processor adding customer-specific
   information to XML pages may not understand or be aware of any final
   HTML content that the end user receives and may not be able to map
   end user request to any internal user identification.

   OPES processors that operate under end user consent may not be
   subject to the above consideration and requirement (XXX the
   architecture draft does not reflect this). It is irrational to expect
   a client-side ISP to provide access to internal hosts participating
   in content processing, whether OPES processors are involved or not.
   Moreover providing such access would serve little practical purpose
   because internal OPES processors are not likely to be able to answer
   any end user queries, being completely our of content processing
   context. For example, an OPES processor making a client-authorized
   XML content translation may not understand or be aware of any final
   HTML content that the end user receives and may not be able to map
   end user request to any internal user identification.




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   IAB consideration 2.2 apparently was not meant to apply to "internal"
   OPES intermediaries. It may be better interpreted as "If the first
   intermediary on end user's message processing path is an OPES
   intermediary, that intermediary must be explicitly addressed at the
   IP layer by the end user". In other words, the end user is assured
   that the first intermediary that touches her request is explicitly
   addressed if it is an OPES intermediary.

   (XXX: should we add a picture showing internal and external OPES
   intermediaries?)









































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5. Notification Considerations

   This section discusses how OPES framework addresses IAB Notification
   concerns 3.1 and 3.2. OPES framework concentrates on tracing rather
   than notification. The tracing specification [XXX] defines "OPES
   trace" as "application message information about OPES entities that
   adapted that message" and "OPES tracing" as "the process of
   including, manipulating, and interpreting an OPES trace" (XXX: keep
   these in sync). Thus, OPES trace follows the application message it
   traces. It notifies the recipient of the message of what has happened
   to that message. Traces are implemented as extensions of application
   protocols being adapted and traced.

   As opposed to an OPES trace, provider notification (as implied by
   IAB) notifies the sender of the message of what had happened to the
   message after the message left the sender. Thus, notifications
   propagate in the opposite direction of traces. Supporting
   notifications directly would require a new protocol. Figure XXX
   illustrates the differences between a trace and notification from a
   single application message point of view.

   sender --[message A]---> OPES --[message A' + trace]--> recipient
      ^                       V
      |                       |
      +-<-- [notification] ---+

                                Figure 1

   Since notifications cannot be piggy-backed to application messages,
   they create new messages and may at least double the number of
   messages the sender has to process (more if several intermediaries on
   the message path emit notifications). Moreover, a notification
   message may refer to some sender state that has to be kept around
   until notification is received, increasing performance overhead of
   notifications. These concerns call for optional notification, with a
   special protocol to enable notifications when needed.

   The level of available details in notifications versus provider
   interest in supporting notification is another concern.  Experience
   shows that content providers often require very detailed information
   about user actions to be interested in notifications at all. For
   example, Hit Metering protocol [XXX] has been designed to supply
   content providers with proxy cache hit counts, in an effort to reduce
   cache busting behavior which was caused by content providers desire
   to get accurate site "access counts". However, the Hit Metering
   protocol is currently not widely deployed because the protocol does
   not supply content providers with information such as client IP
   addresses, browser versions, or cookies.



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   The Hit Metering experience is relevant because Hit Metering protocol
   was designed to do for HTTP caching intermediaries what OPES
   notifications are meant to do for OPES intermediaries. Performance
   requirements call for state reduction via aggregation of
   notifications while provider preferences call for state preservation
   or duplication. Achieving the right balance when two sides belong to
   different organizations and have different optimization priorities is
   probably impossible in general.

   Thus, instead of explicitly supporting notifications on a protocol
   level, OPES concentrates on tracing facilities and supports
   notifications indirectly, using those tracing facilities. In other
   words, the IAB choice of "Notification" label is interpreted as
   "Notification assistance" (i.e. making notifications meaningful) and
   is not interpreted as a "Notification protocol".

5.1 Consideration (3.1) Notification

   "The overall OPES framework needs to assist content providers in
   detecting and responding to client-centric actions by OPES
   intermediaries that are deemed inappropriate by the content
   provider."[RFC3238]

   OPES tracing mechanisms assist content providers in detecting
   client-centric actions by OPES intermediaries. Specifically, a
   compliant OPES intermediary or system notifies a content provider of
   its presence by including its tracing information in the application
   protocol requests. An OPES intermediary MUST leave its trace (XXX
   quote tracing draft). Detection assistance has its limitations. Some
   OPES intermediaries may work exclusively on responses and may not
   have a chance to trace the request. Moreover, some application
   protocols may not have explicit requests (e.g., a content push
   service).

   OPES tracing mechanisms assist content providers in responding to
   client-centric actions by OPES intermediaries. Specifically, OPES
   traces MUST include identification of OPES systems and SHOULD include
   a list of adaptation actions performed on provider's content. This
   tracing information may be included in the application request.
   Usually, however, this information will be included in the
   application response, an adapted version of which does not reach the
   content provider. If OPES end points cooperate, then notification can
   be assisted with traces. Content providers that suspect or experience
   difficulties can do any of the following:

      Check whether requests they receive pass through OPES
      intermediaries. Presence of OPES tracing info will determine that.
      This check is only possible for request/response protocols. For



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      other protocols (e.g., broadcast or push), the provider would have
      to assume that OPES intermediaries are involved until proven
      otherwise.

      If OPES intermediaries are suspected, request OPES traces from
      potentially affected user(s). The trace will be a part of the
      application message received by the user software. If users
      cooperate, the provider(s) have all the information they need. If
      users do not cooperate, the provider(s) cannot do much about it
      (they might be able to deny service to uncooperative users in some
      cases).

      Some traces may indicate that more information is available by
      accessing certain resources on the specified OPES intermediary or
      elsewhere. Content providers may query for more information in
      that case.

      If everything else fails, providers can enforce no-adaptation
      policy using appropriate OPES bypass mechanisms and/or end-to-end
      encryption mechanisms.

   OPES detection and response assistance is limited to application
   protocols with support for tracing extensions. For example, HTTP
   [RFC2616] has such support while DNS over UDP does not.

   (XXX: should we prohibit adaptation of application protocols that do
   not allow for tracing?)

5.2 Consideration (3.2) Notification

   "The overall OPES framework should assist end users in detecting the
   behavior of OPES intermediaries, potentially allowing them to
   identify imperfect or compromised intermediaries."[RFC3238]

   OPES tracing mechanisms assist end users in detecting OPES
   intermediaries. Specifically, a compliant OPES intermediary or system
   notifies an end user of its presence by including its tracing
   information in the application protocol messages sent to the client.
   An OPES intermediary MUST leave its trace (XXX quote tracing draft).
   Detection assistance has its limitations. Some OPES intermediaries
   may work exclusively on requests and may not have a chance to trace
   the response. Moreover, some application protocols may not have
   explicit responses (e.g., event logging service).

   OPES detection assistance is limited to application protocols with
   support for tracing extensions. For example, HTTP [RFC2616] has such
   support while DNS over UDP does not.




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   (XXX: should we prohibit adaptation of application protocols that do
   not allow for tracing?)

5.3 Consideration (3.3) Non-blocking

   "If there exists a "non-OPES" version of content available from the
   content provider, the OPES architecture must not prevent users from
   retrieving this "non-OPES" version from the content
   provider."[RFC3238]

   OPES intermediaries MUST support a bypass feature (XXX quote bypass
   draft). If an application message includes bypass instructions, the
   matching OPES intermediary will not process the message. Bypass may
   generate content errors since some OPES services may be essential.
   (Should there be a way to bypass non-essential services only?)

   Bypass support has limitations similar to the two
   notification-related considerations above.

































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6. Consideration (4.1) URI resolution

   "OPES documentation must be clear in describing these services as
   being applied to the result of URI resolution, not as URI resolution
   itself."[RFC3238]

   "OPES Scenarios and Use Cases" specification
   [I-D.ietf-opes-scenarios] documents content adaptations that are in
   scope of the OPES framework (XXX provide a quote). These adaptations
   do not include URI resolution (XXX check). In some environments, it
   is technically possible to adapt URIs (and other kinds of identifiers
   or addresses) using documented OPES mechanisms.







































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7. Consideration (4.2) Reference validity

   "All proposed services must define their impact on inter- and
   intra-document reference validity."[RFC3238]

   OPES working group does not propose adaptation services. However,
   OPES tracing requirements include identification of OPES
   intermediaries and services (for details, see "Notification"
   consideration sections in this document). It is required that
   provided identification can be used to locate information about the
   OPES intermediaries, including the description of impact on reference
   validity (XXX quote tracing draft).







































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8. Consideration (4.3) Addressing extensions

   "Any services that cannot be achieved while respecting the above two
   considerations may be reviewed as potential requirements for Internet
   application addressing architecture extensions, but must not be
   undertaken as ad hoc fixes."[RFC3238]

   OPES framework does not contain ad hoc services. This and other OPES
   documents should be sufficient to inform service creators of IAB
   considerations. If a service does URI resolution or silently affects
   document reference validity, the authors are requested to review
   service impact on Internet application addressing architecture and
   work within IETF on potential extension requirements.






































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9. Consideration (5.1) Privacy

   "The overall OPES framework must provide for mechanisms for end users
   to determine the privacy policies of OPES intermediaries."[RFC3238]

   OPES tracing mechanisms allow end users to identify OPES
   intermediaries (for details, see "Notification" consideration
   sections in this document). It is required that provided
   identification can be used to locate information about the OPES
   intermediaries, including their privacy policies.

   The terms "privacy" and "privacy policy" are not defined in this
   context (by IAB or OPES working group). OPES tracing mechanisms allow
   end users and content providers to identify OPES intermediaries. It
   is believed that once an intermediary is identified, it would be
   possible to locate relevant information about that intermediary,
   including information relevant to requesters perception of privacy
   policy or reference validity. (XXX: should we move this paragraph
   into a separate section and expand it? one the other hand, it is
   probably the job of the architecture draft to define these things so
   that we can refer to them from here.)






























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10. Security Considerations

   XXX.
















































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11. Compliance

   This document may be perceived as a proof of OPES compliance with IAB
   implied recommendations. However, this document does not introduce
   any compliance subjects. Compliance of OPES implementations is
   defined in other OPES documents discussed above.













































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12. To-do

   security section: Does this document have any original security
      matters worth documenting?

   normative IDs: To be normative, OPES Internet-Drafts must be replaced
      with corresponding RFCs when the latter are published.

   architecture draft: Should architecture draft talk about external/
      internal OPES intermediaries and about privacy policies? Should
      this document be limited to a compilation of references from other
      OPES drafts, or should we introduce/discuss new concepts here?







































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Appendix A. Change Log

   Internal WG revision control ID: $Id: iab-cons.xml,v 1.13 2003/06/12
   15:38:48 rousskov Exp $

   head-sid9

      *  Polished to meet new xml2rfc sctrict requirements.

   head-sid8

      *  Added unpolished meat for all nine considerations.

      *  Added Abbie Barbir as an author.

   head-sid7

      *  Initial revision

































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Normative References

   [I-D.ietf-opes-architecture]
              Barbir, A., "An Architecture for Open Pluggable Edge
              Services (OPES)", draft-ietf-opes-architecture-04 (work in
              progress), December 2002.

   [I-D.ietf-opes-scenarios]
              Barbir, A., "OPES Use Cases and Deployment Scenarios",
              draft-ietf-opes-scenarios-01 (work in progress), August
              2002.

   [RFC3238]  Floyd, S. and L. Daigle, "IAB Architectural and Policy
              Considerations for Open Pluggable Edge Services", RFC
              3238, January 2002.




































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Informative References

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Nielsen, H.,
              Masinter, L., Leach, P. and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.


Authors' Addresses

   Abbie Barbir
   Nortel Networks
   3500 Carling Avenue
   Nepean, Ontario
   CA

   Phone: +1 613 763 5229
   EMail: abbieb@nortelnetworks.com


   Alex Rousskov
   The Measurement Factory

   EMail: rousskov@measurement-factory.com
   URI:   http://www.measurement-factory.com/



























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   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.











































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