Network Working Group                  Internet Architecture Board (IAB)
Request for Comments: 3238                                      S. Floyd
Category: Informational                                        L. Daigle
                                                           January 2002


           IAB Architectural and Policy Considerations for
                     Open Pluggable Edge Services

Status of this Memo

  This memo provides information for the Internet community.  It does
  not specify an Internet standard of any kind.  Distribution of this
  memo is unlimited.

Copyright Notice

  Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

  This document includes comments and recommendations by the IAB on
  some architectural and policy issues related to the chartering of
  Open Pluggable Edge Services (OPES) in the IETF.  OPES are services
  that would be deployed at application-level intermediaries in the
  network, for example, at a web proxy cache between the origin server
  and the client.  These intermediaries would transform or filter
  content, with the explicit consent of either the content provider or
  the end user.

1.  Introduction

  Open Pluggable Edge Services (OPES) are services that would be
  deployed in the network, for example, at a web proxy cache between
  the origin server and the client, that would transform or filter
  content.  Examples of proposed OPES services include assembling
  personalized web pages, adding user-specific regional information to
  web pages, virus scanning, content adaptation for clients with
  limited bandwidth, language translation, and the like [OPES].

  The question of chartering OPES in the IETF ([OPESBOF1], [OPESBOF2],
  [OPESBOF3]) and the related controversy in the IETF community
  ([Carr01], [CDT01], [Morris01], [Orman01], [Routson01]) have raised
  to the fore several architectural and policy issues about robustness
  and the end-to-end integrity of data (in terms of the disparities
  between what the "origin server" makes available and what the client
  receives).  In particular, questions have been raised about the
  possible requirements, for a protocol to be developed and



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  standardized in the IETF, for that protocol to protect the end-to-end
  privacy and integrity of data.  This document attempts to address
  some of the architectural and policy issues that have been unresolved
  in the chartering of OPES, and to come to some common recommendations
  from the IAB regarding these issues.

  The purpose of this document is not to recommend specific solutions
  for OPES, or even to mandate specific functional requirements.  This
  is also not a recommendation to the IESG about whether or not OPES
  should be chartered.  Instead, these are recommendations on issues
  that any OPES solutions standardized in the IETF should be required
  to address, similar to the "Security Considerations" currently
  required in IETF documents [RFC2316].  As an example, one way to
  address security issues is to show that appropriate security
  mechanisms have been provided in the protocol, and another way to
  address security issues is to demonstrate that no security issues
  apply to this particular protocol.  (Note however that a blanket
  sentence that "no security issues are involved" is never considered
  sufficient to address security concerns in a protocol with known
  security issues.)

  This document will try to make our concerns underlying integrity,
  privacy, and security as clear as possible.  We recommend that the
  IESG require that OPES documents address integrity, privacy, and
  security concerns in one way or another, either directly by
  demonstrating appropriate mechanisms, or by making a convincing case
  that there are no integrity or privacy concerns relevant to a
  particular document.

  In particular, it seems unavoidable that at some point in the future
  some OPES service will perform inappropriately (e.g., a virus scanner
  rejecting content that does not include a virus), and some OPES
  intermediary will be compromised either inadvertently or with
  malicious intent.  Given this, it seems necessary for the overall
  architecture to help protect end-to-end data integrity by addressing,
  from the beginning of the design process, the requirement of helping
  end hosts to detect and respond to inappropriate behavior by OPES
  intermediaries.

  One of the goals of the OPES architecture must be to maintain the
  robustness long cited as one of the overriding goals of the Internet
  architecture [Clark88].  Given this, we recommend that the IESG
  require that the OPES architecture protect end-to-end data integrity
  by supporting end-host detection and response to inappropriate
  behavior by OPES intermediaries.  We note that in this case by
  "supporting end-host detection", we are referring to supporting
  detection by the humans responsible for the end hosts at the content
  provider and client.  We would note that many of these concerns about



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  the ability of end hosts to detect and respond to the inappropriate
  behavior of intermediaries could be applied to the architectures for
  web caches and content distribution infrastructures even without the
  additional complication of OPES.

  Each section of the document contains a set of IAB Considerations
  that we would recommend be addressed by the OPES architecture.
  Section 6 summarizes by listing all of these considerations in one
  place.

  In this document we try to use terminology consistent with RFC 3040
  [RFC 3040] and with OPES works in progress.

2.  Some history of the controversy about chartering OPES

  One view on OPES has been that "OPES is deeply evil and the IETF
  should stay far, far away from this hideous abomination" [ODell01].
  Others have suggested that "OPES would reduce both the integrity, and
  the perception of integrity, of communications over the Internet, and
  would significantly increase uncertainly about what might have been
  done to content as it moved through the network", and that therefore
  the risks of OPES outweigh the benefits [CDT01].  This view of the
  risks of OPES was revised in later email, based on the proposals from
  [Carr01], "assuming that certain privacy and integrity protections
  can be incorporated into the goals of the working group" [Morris01].

  One issue concerns the one-party consent model.  In the one-party
  consent model, one of the end-nodes (that is, either the content
  provider or the end user) is required to explicitly authorize the
  OPES service, but authorization is not required from both parties.
  [CDT01] comments that relying only on a one-party consent model in
  the OPES charter "could facilitate third-party or state-sponsored
  censorship of Internet content without the knowledge or consent of
  end users", among other undesirable scenarios.

  A natural first question is whether there is any architectural
  benefit to putting specific services inside the network (e.g., at the
  application-level web cache) instead of positioning all services
  either at the content provider or the end user.  (Note that we are
  asking here whether there is architectural benefit, which is not the
  same as asking if there is a business model.)  Client-centric
  services suggested for OPES include virus scanning, language
  translation, limited client bandwidth adaptation, request filtering,
  and adaptation of streaming media, and suggested server-centric
  services include location-based services and personalized web pages.






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  It seems clear that there can indeed be significant architectural
  benefit in providing some OPES services inside the network at the
  application-level OPES intermediary.  For example, if some content is
  already available from a local or regional web cache, and the end
  user requires some transformation (such as adaptation to a limited-
  bandwidth path) applied to that data, providing that service at the
  web cache itself can prevent the wasted bandwidth of having to
  retrieve more data from the content provider, and at the same time
  avoid unnecessary delays in providing the service to the end user.

  A second question is whether the architectural benefits of providing
  services in the middle of the network outweigh the architectural
  costs, such as the potential costs concerning data integrity.  This
  is similar to the issues considered in RFC 3135 [RFC 3135] of the
  relative costs and benefits of placing performance-enhancing proxies
  (PEPs) in the middle of a network to address link-related
  degradations.  In the case of PEPs, the potential costs include
  disabling the end-to-end use of IP layer security mechanisms;
  introducing a new possible point of failure that is not under the
  control of the end systems; adding increased difficulty in diagnosing
  and dealing with failures; and introducing possible complications
  with asymmetric routing or mobile hosts.  RFC 3135 carefully
  considers these possible costs, the mitigations that can be
  introduced, and the cases when the benefits of performance-enhancing
  proxies to the user are likely to outweigh the costs.  A similar
  approach could be applied to OPES services (though we do not attempt
  that here).

  A third question is whether an OPES service, designed primarily for a
  single retrieval action, has an impact on the application layer
  addressing architecture.  This is related to the integrity issue
  above, but is independent of whether these services are applied in
  the middle of the network or at either end.

  Most of this document deals with the specific issue of data integrity
  with OPES services, including the goal of enabling end hosts to
  detect and respond to inappropriate behavior from broken or
  compromised OPES intermediaries.

  We agree that one-party consent, with one of the end-hosts explicitly
  authorizing the OPES service, must be a requirement for OPES to be
  standardized in the IETF.

  However, as we discuss in the next section of this document, we agree
  with [CDT01] that the one-party consent model by itself (e.g., with
  one of the end-hosts authorizing the OPES service, and the other
  end-host perhaps being unaware of the OPES service) is insufficient
  for protecting data integrity in the network.  We also agree with



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  [CDT01] that, regardless of the security and authorization mechanisms
  standardized for OPES in the IETF, OPES implementations could
  probably be modified to circumvent these mechanisms, resulting in the
  unauthorized modification of content.  Many of the protocols in the
  IETF could be modified for anti-social purposes - transport protocols
  could be modified to evade end-to-end congestion control, routing
  protocols could be modified to inject invalid routes, web proxy
  caches could be used for the unauthorized modification of content
  even without OPES, and so on.  None of these seem like compelling
  reasons not to standardize transport protocols, routing protocols,
  web caching protocols, or OPES itself.  In our view, it means instead
  that the infrastructure needs, as much as possible, to be designed to
  detect and defend itself against compromised implementations, and
  misuses of protocols need to be addressed directly, each in the
  appropriate venue.

  Mechanisms such as digital signatures, which help users to verify for
  themselves that content has not been altered, are a first step
  towards the detection of the unauthorized modification of content in
  the network.  However, in the case of OPES, additional protection to
  ensure the end-to-end integrity of data is desirable as well, for
  example, to help end-users to detect cases where OPES intermediaries
  were authorized to modify content, but perform inappropriate
  modifications.  We would note that mechanisms can *help* end-users to
  detect compromised OPES intermediaries in some cases even if they do
  not *guarantee* that end-users will be able to detect compromised
  OPES intermediaries in all cases.

  If OPES is chartered, the OPES working group will also have to
  explicitly decide and document whether the OPES architecture must be
  compatible with the use of end-to-end encryption by one or more ends
  of an OPES-involved session.  If OPES was compatible with end-to-end
  encryption, this would effectively ensure that OPES boxes would be
  restricted to ones that are known, trusted, explicitly addressed at
  the IP layer, and authorized (by the provision of decryption keys) by
  at least one of the ends.  Compatibility with end-to-end encryption
  would also help to prevent the widespread deployment of yet another
  set of services that, to benefit from, require one to keep one's
  packet contents in the clear for all to snoop.

  IAB Considerations:

  (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).





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  (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.

  We note that (2.2) is not intended to preclude a chain of
  intermediaries, with the first intermediary in the chain explicitly
  addressed at the IP layer by the end user.

3.  End-to-end Integrity

  The proposed OPES services have several possible forms, including
  server-centric services, such as the dynamic assembling of web pages,
  explicitly authorized by the content provider; client-centric
  services such as virus scanning or language translation explicitly
  authorized by the end user to act on the response from the content
  provider; and client-centric services such as privacy-based services
  or content-filtering explicitly authorized by the end user to act on
  the request from the end user to the content provider.  We consider
  the issue of the end-to-end integrity of data separately for these
  different classes of services.

  For each specific service, the question arises of whether it is
  necessary for both the content provider and the end user to be able
  to detect and respond to inappropriate behavior by OPES
  intermediaries, or if it is sufficient for just one of the two end-
  hosts to have this ability.  We don't attempt a general answer, but
  we do discuss the issues further in the sections below.

3.1.  Data integrity with client-centric OPES services on responses

  Why is there any concern about the end-to-end integrity of data in a
  client-centric OPES service acting on a response from a content
  provider?  If the client requests a service such as virus scanning or
  language translation, why is that of any concern to the content
  provider one way or another?  One answer is that one of the proper
  concerns of the IETF is to design architectures that enable end-hosts
  to detect and respond to inappropriate actions in the network.  This
  seems of particular importance for powerful devices in the network
  such as OPES intermediaries, which are authorized by one of the end-
  nodes to act on or transform data in the network, but other than that
  are not under the direct control of that end-node.

  Consider as an example the services of virus scanning or language
  translation.  The end user has reasonable power in detecting and
  dealing with imperfect or corrupted virus scanners or language
  translators that are under her direct control (e.g., on her own
  machine).  The end user knows exactly what program is installed, and
  has direct access to the content before and after the service is



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  applied.  The end user would have less control over similar services
  offered by OPES in the network itself, where the end user's only
  control might be the binary one of authorizing or not authorizing the
  service.  (We also note that services deployed on the end host in a
  self-contained fashion, such as a local virus scanning program, are
  not a service in the network, and therefore are not in the province
  of the IETF one way or another.)

  For a OPES service such as virus scanning or language translation,
  the end user could detect a corrupted intermediary, but only through
  a "black-box" approach of comparing the input with the output.  This
  is also imprecise and requires some effort, compared to the effort
  required to detect a corrupted virus scanner installed on one's own
  machine.  For example, the user could retrieve the "non-OPES" version
  of the content directly from the content provider, if there is a
  "non-OPES" version, and compare this with the "OPES" version of the
  content available from the OPES intermediary.  However, in the case
  of dynamic content, the "non-OPES" version of the content retrieved
  by the user directly from the content provider might not necessarily
  be the same as the "non-OPES" version of the content considered by
  the OPES intermediary.  This limited control by the end user of the
  OPES service, and the limited ability of the end user to detect
  imperfect or corrupted intermediaries, argues for an architecture
  that helps the content provider to detect and respond to imperfect or
  corrupted OPES intermediaries as well.

  We consider the specific example of virus scanning, authorized by the
  end user as an OPES service.  One could imagine virus scanning as a
  widely deployed OPES service, augmenting the virus scanning done on
  the end host itself.  If I ask for, say, a paper by Steve Bellovin on
  security and viruses in the network, and am informed by my authorized
  OPES virus-scanning service that this content does not pass the
  virus-scan, there are a number of possibilities:

  (1) Unknown to Steve, the content (that is, Steve's paper) contains a
      harmful virus.

  (2) Steve inserted a harmful virus in the content on purpose, with
      playful or malicious intent.

  (3) The OPES virus scanner can't distinguish between a true harmful
      virus, and Steve's paper about harmful viruses.

  (4) My local OPES virus scanner has been hacked, with malicious
      intent, to reject all content from Steve Bellovin.






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  At some point, for some content, some widely-deployed implementation
  of some OPES virus scanner is likely to result in problem (3), and
  some OPES implementation is likely to be corrupted to result in
  problem (4).  Because the end user has limited control over the OPES
  virus scanner, the end user also is limited in its ability to detect
  problems (3) or (4) in the OPES virus scanner.  In addition, the
  content provider is probably the one with the strongest incentive to
  detect problems (3) or (4) in the OPES virus scanner.  (The content
  provider generally has a strong incentive to detect problem (1) as
  well.)  In this case, it seems prudent that the overall OPES
  architecture should be carefully designed to prevent the OPES service
  of virus scanning, as authorized by the client, from unnecessarily
  preventing the distribution of content that in fact does not have
  viruses.

  Obviously, it is not viable to propose that content providers simply
  indicate that some content should be passed to the end user without
  virus scanning - the point of virus scanning is for the end user to
  exercise control in this regard.  However, if some form of end-system
  notification allows the content provider to find out that the content
  is being rejected by a virus scanning service instead of being
  delivered to the end user, then the content provider (Steve, in this
  case) might want to inform end users that this content is known by
  the content provider not to pass some OPES virus scanning services.
  End users could then make their own decisions about whether or not to
  retrieve that content bypassing the OPES virus scanning service,
  relying on their own virus scanner or an alternate virus scanning
  service for this particular content.  Such end-system notification to
  the content provider, if requested, cannot be enforced, and cannot be
  relied upon from corrupted intermediaries, but it seems important
  nevertheless.

  Of course, malicious users can also use their awareness of the virus
  scanning service to perfect their ability to construct malicious
  viruses that can evade the virus scanning service.  This will be done
  anyway, with any virus scanning service, and seems like an acceptable
  cost to allow content providers some protection against the vagaries
  of imperfect or corrupted OPES services in the network.

  Thus, for client-requested services such as virus scanning and
  language translation, it is clearly desirable for the origin server
  to have notification, if it requests it, that these services are
  being performed on its content before the content is sent to the
  client.  Any such end-system notification might be accompanied by
  reduced performance (in terms of overhead, delays, etc.) for the OPES
  service applied to that content.  But some form of end-system





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  notification is clearly necessary if content providers are to be able
  to detect and respond to actions by OPES intermediaries that are
  deemed inappropriate by the content provider.

  Similarly for a client-based OPES service of language translation, it
  is clearly desirable for content providers to be able to inform end
  users when some content is deemed by the content provider to be
  incompatible with language translation.  In this case, the important
  issue is not to prevent the OPES language translation from being
  performed on the content, but instead to give the content provider
  some mechanism to discover the language translation, and to inform
  the end user (or more precisely, to inform the end user's host
  computer) if the content provider believes that this language
  translation is incompatible with this particular content.

  IAB Considerations:

  (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.

3.2.  Data integrity with server-centric OPES services

  What are the concerns, if any, with the end-to-end integrity of data
  in a server-centric OPES service such as location-based services?
  For example, CNN could authorize a location-based OPES service, where
  the OPES intermediary inserts the weather report or news headline of
  regional interest into the requested web page.  The same issue of the
  detection and response to broken or modified OPES intermediaries
  occurs with server-centric OPES as with client-centric OPES services.
  We only consider server-centric services on responses, as we are not
  aware of any proposals for server-centric OPES services on requests
  from the client to the content provider.

  How are the end-nodes to detect inappropriate actions from OPES
  services authorized by the content provider?  The OPES service is
  being performed at an OPES intermediary in the network itself, and
  not under the direct control of the content provider; in particular,
  the content provider might not have the ability to monitor directly
  the output of the OPES intermediary.  One could argue that the
  content provider and server-centric OPES intermediary are part of a
  single distributed application, and can be responsible on their own
  for detecting and dealing with broken or modified OPES
  intermediaries, without involving the end user.  But this is
  unconvincing, basically arguing that standardizing protocols for
  performing OPES services is a network issue properly in the domain of
  the IETF, but the ensuring the overall integrity of the service is a



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  distributed application matter, and not in the province of the IETF
  at all.  It would seem to us that you can't have it both ways.
  Simply labeling the content provider and the OPES intermediary as
  part of the same distributed application does not give the content
  provider the ability to monitor the actions of the OPES intermediary.

  However, if the end user receives some form of notification that
  these OPES services have been provided, and has some mechanism for
  receiving the "non-OPES" content from the content provider without
  the OPES intermediary's modifications (if there is such a thing as a
  non-OPES version of the content), then the end user is in a better
  position to detect and react to inappropriate actions from
  compromised or poorly-designed OPES intermediaries.  Thus, it is
  clear that some form of end-system notification is required to allow
  the end user to detect and respond to broken or modified OPES
  intermediaries.  If the end user has notification of action by OPES
  intermediaries, it could "veto" an OPES service simply by throwing
  the OPES-modified content away.  And if the client wants to talk
  directly to the origin server to receive the "non-OPES" version, and
  the origin server is configured to allow this, then the OPES
  intermediary must be designed to permit this end-to-end
  communication.

  In addition to concerns about detecting and responding to faulty or
  compromised OPES intermediaries, there are purely policy-based
  concerns about the integrity of data.  If the content provider looks
  at the source IP address from the HTTP request, or tosses a coin, in
  order to decide what content to provide, then that is the content
  provider's business.  But if there exists a "non-OPES" version of
  some content available from the content provider, and also modified
  versions available from OPES intermediaries, then it is important
  that end users would be able to discover that they are receiving a
  modified version from the network, and not the "non-OPES" version
  that is also available from the content provider directly.

  IAB Considerations:

  (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.

  (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.






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3.3.  Data integrity with client-centric OPES services on requests

  There have also been proposals for OPES services authorized by the
  client on requests from the client to the content provider.  Examples
  include services that remove fields from the HTTP header for added
  privacy, and content-filtering services that filter requests based on
  the requested URL.  For such services, there is still a need for end
  hosts to be assisted in detecting and responding to imperfect or
  corrupted intermediaries, but it seems less clear to what extent this
  applies to the content provider, and to what extent it applies to the
  end user that authorized the service.  The requirements will probably
  have to be determined by the OPES and wider IETF communities on a
  case-by-case basis for each specific service.

4.  Application Layer Addresses

  Most application layer addressing revolves around URIs, which, for
  the most part, give a structured method to refer to a single data
  entity on a remote server.  URIs are universal in that, in principle,
  the same result is obtained irrespective of the location of the
  client performing the resolution.

  Practice often differs from this theory -- ad-strippers remove data
  from pages at the client end; web server farms redirect clients to
  one of several potential target machines for load-balancing or to
  give the user "localized" content.

  However, from an architectural standpoint, it is important to be
  clear about what is being done here.  In all cases, URI resolution
  standards (as defined for individual URI schemes, such as HTTP) apply
  unchanged between the client and the OPES intermediary.  What the
  intermediary does to fulfill the request is not material to the
  discussion, and must produce a result that is compliant with the
  applicable URI scheme definition.  In this sense, the OPES
  intermediary is the "endpoint" of URI resolution.

  In client-centric OPES, the intermediary is resolving the URI on
  behalf of the client, and then applying client-requested services to
  provide a data response to the client.  The client gets the data it
  wanted, but it did not carry out the URI resolution.

  In server-centric OPES, the "origin server" cedes its authority to
  the intermediary to determine what is the "appropriate" content to
  supply for a given URI.   The client may well perform standard URI
  resolution, but that reaches no further than the intermediary.

  With those distinctions firmly in mind, there are two particular
  areas of concern for OPES-like services.



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  The first is the consideration of the effect of a series of
  interactions, over time and location (i.e., not just one document
  retrieval).   Potential problems include inconsistencies in intra-
  and inter-document references -- depending on what content is
  changed, references from one version of a document might not exist in
  a modified target, etc.

  The other concern is whether this leads to the creation of content
  that is exclusively accessible through the use of an intermediary.
  That is, there is no "non-OPES" version.  Either this should not be
  allowed, or this would argue for an extension to the Internet
  application layer addressing architecture.

  IAB Considerations:

  (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.

  (4.2) Reference validity: All proposed services must define their
  impact on inter- and intra-document reference validity.

  (4.3) 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.

5.  Privacy

  Intermediaries in the middle of the network increase the number of
  locations where the privacy of an end-to-end transaction could be
  compromised.  Some of these privacy concerns apply to web caches and
  CDNs in general as well as specifically to OPES intermediaries.  It
  seems a reasonable requirement, for OPES to be chartered in the IETF,
  that the issue of providing mechanisms for end users to determine the
  privacy policies of OPES intermediaries should be addressed.  These
  mechanisms could be quite different for client-centric and server-
  centric OPES services.

  For a complex issue such as an OPES architecture, which interacts
  with protocols from other standards bodies as well as from other IETF
  working groups, it seems necessary to keep in mind the overall
  picture while, at the same time, breaking out specific parts of the
  problem to be standardized in particular working groups.  Thus, a
  requirement that the overall OPES architecture address privacy
  concerns does not necessarily mean that the mechanisms for this need
  to be developed in the IETF, or in the OPES working group (if it is
  chartered).



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  IAB Considerations:

  (5.1) Privacy: The overall OPES framework must provide for mechanisms
  for end users to determine the privacy policies of OPES
  intermediaries.

6.  Summary of IAB Considerations

  (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).

  (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.

  (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.

  (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.

  (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.

  (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.

  (4.2) Reference validity: All proposed services must define their
  impact on inter- and intra-document reference validity.

  (4.3) 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.

  (5.1) Privacy: The overall OPES framework must provide for mechanisms
  for end users to determine the privacy policies of OPES
  intermediaries.





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7.  Conclusions

  This document includes comments and recommendations by the IAB on
  some architectural and policy issues related to the chartering of
  OPES in the IETF.

8.  Acknowledgements

  This document has benefited from discussions with members of the IAB
  and the IESG, contributors to OPES, John Wroclawski, and others.
  However, this is a document of the IAB, and we do not claim that the
  other people listed above agree with the contents.

9.  References

  [Carr01]    Wayne Carr, "Suggested OPES Requirements for Integrity,
              Privacy and Security", email to [email protected],
              August 16, 2001.  URL "http://www.imc.org/ietf-
              openproxy/mail-archive/msg00869.html".

  [CDT01]     Policy Concerns Raised by Proposed OPES Working Group
              Efforts, email to the IESG, from the Center for Democracy
              & Technology, August 3, 2001.  URL
              "http://www.imc.org/ietf-openproxy/mail-
              archive/msg00828.html".

  [Clark88]   David D. Clark, The Design Philosophy of the DARPA
              Internet Protocols, SIGCOMM 1988.

  [Morris01]  John Morris, "Re: corrected -  Suggested OPES
              Requirements for Integrity, Privacy and Security",
              September 28, 2001.  Email to [email protected], URL
              "http://www.imc.org/ietf-openproxy/mail-
              archive/msg00935.html".

  [ODell01]   Mike O'Dell, "OPES continuing froth...", Message-Id:
              <[email protected]>, July 10, 2001, email to
              [email protected].  URL "http://www1.ietf.org/mail-
              archive/ietf/Current/msg12650.html".

  [OPES]      Open Pluggable Edge Services (OPES) Web Page,
              "http://www.ietf-opes.org/".

  [OPESBOF1]  OPES BOF, 49th IETF, December 12, 2000.  Agenda:
              "http://www.ietf.org/ietf/00dec/opes-agenda.txt".
              Minutes:  "http://www.ietf.cnri.reston.va.us/
              proceedings/00dec/toc.htm#P25_256".




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RFC 3238              IAB Considerations for OPES           January 2002


  [OPESBOF2]  OPES BOF, 50th IETF, March 9, 2001.  Minutes:
              "http://www.ietf.org/proceedings/01mar/ietf50-40.htm".

  [OPESBOF3]  OPES BOF, 51st IETF, August 2001.  Agenda:
              "http://www.ietf.org/ietf/01aug/opes.txt".  Minutes:
              "http://www.ietf.org/proceedings/01aug/minutes/OPES.HTM".

  [Orman01]   Hilarie Orman, "Data Integrity for Open Pluggable
              Services", email to [email protected], August 15,
              2001.  URL "http://www.imc.org/ietf-openproxy/mail-
              archive/msg00865.html".

  [RFC 2316]  Bellovin, S., "Report of the IAB Security Architecture
              Workshop", RFC 2316, April 1998.

  [RFC2401]   Kent, S. and R. Atkinson, "Security Architecture for the
              Internet Protocol", RFC 2401, November 1998.

  [RFC 3040]  Cooper, I., Melve, I. and G. Tomlinson, "Internet Web
              Replication and Caching Taxonomy", RFC 3040, January
              2001.

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

  [Routson01] Joyce Routson, IETF's Edge Standards Controversy, July
              11, 2001, Stardust CDN Week.  URL
              "http://www.stardust.com/cdnweek/articles/2001/07/09/
              opes.htm".

10.  Security Considerations

  This document does not propose any new protocols, and therefore does
  not involve any security considerations in that sense.  However,
  throughout this document there are discussions of the privacy and
  integrity issues of OPES services and the architectural requirements
  created by those issues.

11.  IANA Considerations

  There are no IANA considerations regarding this document.









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Authors' Addresses

  Internet Architecture Board
  EMail:  [email protected]

  Membership at time this document was completed:

  Harald Alvestrand
  Ran Atkinson
  Rob Austein
  Fred Baker
  Steve Bellovin
  Brian Carpenter
  Jon Crowcroft
  Leslie Daigle
  Steve Deering
  Sally Floyd
  Geoff Huston
  John Klensin
  Henning Schulzrinne































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12.  Full Copyright Statement

  Copyright (C) The Internet Society (2002).  All Rights Reserved.

  This document and translations of it may be copied and furnished to
  others, and derivative works that comment on or otherwise explain it
  or assist in its implementation may be prepared, copied, published
  and distributed, in whole or in part, without restriction of any
  kind, provided that the above copyright notice and this paragraph are
  included on all such copies and derivative works.  However, this
  document itself may not be modified in any way, such as by removing
  the copyright notice or references to the Internet Society or other
  Internet organizations, except as needed for the purpose of
  developing Internet standards in which case the procedures for
  copyrights defined in the Internet Standards process must be
  followed, or as required to translate it into languages other than
  English.

  The limited permissions granted above are perpetual and will not be
  revoked by the Internet Society or its successors or assigns.

  This document and the information contained herein is provided on an
  "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
  TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
  BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
  HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
  MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

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



















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