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Versions: 00 01 02 03 04 RFC 3835

Network Working Group                                     Abbie. Barbir
Internet-Draft                                           Nortel Networks
Expires: November 1, 2002                                        R. Chen
                                                               AT&T Labs
                                                              M. Hofmann
                                           Bell Labs/Lucent Technologies
                                                                H. Orman
                                           The Purple Streak Development
                                                                R. Penno
                                                         Nortel Networks
                                                            G. Tomlinson
                                                               Cacheflow
                                                             May 3, 2002


        An Architecture for Open Pluggable Edge Services (OPES)
                    draft-ietf-opes-architecture-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
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   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
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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 November 1, 2002.

Copyright Notice

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

Abstract

   This memo defines an architecture for a cooperative application
   service in which a data provider, a data consumer, and zero or more



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   application entities cooperatively realize a data stream service.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  The Architecture . . . . . . . . . . . . . . . . . . . . . . .  4
   2.1 OPES Entities  . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.2 OPES Flows . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.3 OPES Rules . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   2.4 Callout Servers  . . . . . . . . . . . . . . . . . . . . . . .  7
   2.5 Policy Enforcement . . . . . . . . . . . . . . . . . . . . . .  8
   2.6 Tracing Facility . . . . . . . . . . . . . . . . . . . . . . .  8
   3.  Security and Privacy Considerations  . . . . . . . . . . . . . 10
   3.1 Trust Domains  . . . . . . . . . . . . . . . . . . . . . . . . 10
   3.2 Primary data flow  . . . . . . . . . . . . . . . . . . . . . . 11
   3.3 Callout protocol . . . . . . . . . . . . . . . . . . . . . . . 11
   3.4 Privacy  . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
   3.5 Establishing trust . . . . . . . . . . . . . . . . . . . . . . 12
   3.6 End-to-end Integrity . . . . . . . . . . . . . . . . . . . . . 12
   4.  Summary  . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
       References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 14
   A.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
       Full Copyright Statement . . . . . . . . . . . . . . . . . . . 17



























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1. Introduction

   When realizing a data stream service between a provider and a
   consumer, the need may arise to provision the use of other
   application entities, in addition to the provider and consumer.  For
   example, some party may wish to customize a data stream as a service
   to a consumer, e.g., a service might customize the data based on the
   customer's geographical locality (e.g., language) or resource
   availability (e.g., display capabilities).

   In some cases it may be impossible to offer the customization service
   at either the provider or the consumer applications.  In this case,
   one or more additional application entities may participate in the
   data stream service.  There are many possible provisioning scenarios
   which make a data stream service attractive.  The reader is referred
   to [1] for a  description of several scenarios.

   The document presents the architectural components of Open Pluggable
   Edge Services (OPES) that are needed in order to perform a data
   stream service.  The architecture addresses the IAB considerations
   described in [2].  These considerations are covered in the various
   parts of the document, specifically with respect to tracing (Section
   2.6) and security considerations (Section 3).

   The document is organized as follows: Section 2 introduces the OPES
   architecture.  Section 3 discusses security considerations.  Section
   4 provides a summary of the architecture and the requirements for
   interoperability.























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2. The Architecture

   The architecture of Open Pluggable Edge Services (OPES) can be
   described in terms of three interrelated concepts, mainly:

   o  OPES entities: processes operating in the network;

   o  OPES flows:  data flows that are cooperatively realized by the
      OPES entities; and,

   o  OPES rules: these determine how a given data flow is modified by
      an OPES entity.


2.1 OPES Entities

   An OPES entity is an application that operates on a data flow between
   a data provider application and a data consumer application.  OPES
   entities can be one of the following:

   o  an OPES service application, which analyzes and possibly
      transforms messages exchanged between the data provider
      application and the data consumer application; or,

   o  a data dispatcher, which invokes an OPES service application based
      on filtering rules and application-specific knowledge.

   In the network, OPES entities reside inside OPES processors.  The
   cooperative behavior of OPES entities introduces additional
   functionality for each data flow provided that it matches the OPES
   rules.

   The OPES architecture is largely independent of the protocol that is
   used by the OPES entities to exchange data.  However, this document
   selects HTTP [4] as the example protocol to be used for realizing a
   data flow.  In this regard, the "protocol" stack of an OPES entity is
   summarized in Figure 1.














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   ---------------------------------------------------------------------



                               OPES entity
                             +-------------+
                             |             |
                             |    HTTP     |
                             |             |
                             +-------------+
                             |   TCP/IP    |
                             +-------------+
                             |     ...     |
                             +-------------+

                    Figure 1: An OPES protocol stack

   ---------------------------------------------------------------------

   Figure 1  depicts a "minimal" stack for OPES.  However, other
   protocols may be present, depending on the functions that are
   performed by the application.

2.2 OPES Flows

   An OPES flow is a cooperative undertaking between a data provider
   application, a data consumer application, one or more OPES service
   applications, and one or more data dispatchers.

   In order to understand the trust relationships between OPES entities,
   each is labeled as residing in an administrative domain.  However,
   depending on provisioning decisions, the entities associated with a
   given OPES flow may reside in one or more administrative domains.

   For example, Figure 2 depicts a data flow (also known as an "OPES
   flow"), that spans two administrative domains.















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   ---------------------------------------------------------------------



    consumer administrative domain       provider administrative domain
   +------------------------------+     +------------------------------+
   |                              |     |                              |
   |       data          OPES     |     |     OPES          data       |
   |     consumer      processor  |     |   processor     provider     |
   |                              |     |                              |
   |   +----------+   +--------+  |     |  +--------+   +----------+   |
   |   |   data   |   |  OPES  |  |     |  |  OPES  |   |   data   |   |
   |   | consumer |   |service |  |     |  |service |   | provider |   |
   |   |   appl   |   |  appl  |  |     |  |  appl  |   |   appl   |   |
   |   +----------+   +--------+  |     |  +--------+   +----------+   |
   |   |          |   |        |  |     |  |        |   |          |   |
   |   |   HTTP   |   |  HTTP  |  |     |  |  HTTP  |   |   HTTP   |   |
   |   |          |   |        |  |     |  |        |   |          |   |
   |   +----------+   +--------+  |     |  +--------+   +----------+   |
   |   |  TCP/IP  |   | TCP/IP |  |     |  | TCP/IP |   |  TCP/IP  |   |
   |   +----------+   +--------+  |     |  +--------+   +----------+   |
   |        ||         ||    ||   |     |   ||    ||         ||        |
   |        =============    =================    =============        |
   |                              |     |                              |
   +------------------------------+     +------------------------------+
            | <----------------- OPES flow -----------------> |


                         Figure 2: An OPES flow

   ---------------------------------------------------------------------

   Figure 2 depicts two data dispatchers that are present in the OPES
   flow.  However, the architecture allows for zero or more data
   dispatchers to be present in any flow.

2.3 OPES Rules

   The behavior of data dispatchers  is governed by a set of filtering
   rules, consisting of a set of conditions and related actions.  The
   ruleset is the superset of all OPES rules on the processor.  Data
   dispatchers invoke OPES service applications that may perform
   modifications on an OPES flow.  In this model, all data filters are
   invoked for all data.

   In order to ensure predictable behavior  the OPES architecture
   requires the use of a standardized schema for the purpose of defining
   and interpreting the ruleset.  The OPES architecture does not require



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   a mechanism for configuring a ruleset into a data dispatcher.  This
   is treated as a local matter for each implementation (e.g., through
   the use of a text editor, secure upload protocol, and so on).  Future
   revisions of the architecture may introduce such a requirement.

2.4 Callout Servers

   The OPES ruleset is executed within a data dispatcher, which triggers
   the execution of local OPES service applications.  How the ruleset is
   executed is not the subject of the architecture.  However, in some
   cases it may be useful for the OPES processor to distribute  the
   responsibility of service execution by communicating with one or more
   callout servers (cf., [7]).  The situation is illustrated in Figure
   3, which shows a data dispatcher communicating with multiple callout
   servers as it processes an OPES flow.

   ---------------------------------------------------------------------


        +----------+  +---------+   +---------+     +---------+
        |   data   |  | callout |   | callout |     | callout |
        |dispatcher|  | server  |   | server  |     | server  |
        +----------+  +---------+   +---------+     +---------+
        |          |  |         |   |         |     |         |
        |   OCP    |  |   OCP   |   |   OCP   | ... |   OCP   |
        |          |  |         |   |         |     |         |
        +----------+  +---------+   +---------+     +---------+
        |  TCP/IP  |  |  TCP/IP |   |  TCP/IP |     |  TCP/IP |
        +----------+  +---------+   +---------+     +---------+
           ||              ||            ||              ||
           ||================            ||     ...      ||
           ||                            ||              ||
           ||==============================              ||
           ||                                            ||
           ================================================


              Figure 3: An OPES flow with Callout servers

   ---------------------------------------------------------------------

   In Figure 3, a data dispatcher invokes the services of a callout
   server by using the OPES callout protocol (OCP).  The requirements
   for the OCP are given in [7].  The OCP is application-agnostic, being
   unaware of the semantics of the encapsulated  application protocol
   (e.g., HTTP).  However, the OCP must  incorporate a service aware
   vectoring capability that parses the data flow according to the
   ruleset and delivers the data to the OPES service application that



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   can be local or remote.

2.5 Policy Enforcement

   Data dispatchers include a ruleset that can be compiled from several
   sources and must resolve into an unambiguous result.  The compiled
   ruleset enables an OPES processor to detremine which service
   applications to invoke for which data flow.          Accordingly, the data
   dispatcher consitutes an enhanced Policy Enforcement Point (PEP),
   where policy rules are executed, data vectoring and connection
   management is performed, and service-specific data handlers and state
   information are maintained, as depicted in Figure 4.

   ---------------------------------------------------------------------


                                    +----------+
                                    |  callout |
                                    |  server  |
                                    +----------+
                                         ||
                                         ||
                                         ||
                                         ||
                     +---------------------------+
                     | +----------+      ||     |
                     | |   OPES   |      ||     |
                     | |  service |      ||     |
                     | |   appl   |      ||     |
                     | +----------+      ||     |
                     | +----------------------+ |
     OPES flow <---->| | data dispatcher/PEP  | | <----> OPES flow
                     | +----------------------+ |
                     |           OPES           |
                     |         processor        |
                     +--------------------------+

        Figure 4: Data Dispatchers and Policy Enforcement Point

   ---------------------------------------------------------------------

   The architecture allows more than one PEP to be present on an OPES
   flow.

2.6 Tracing Facility

   The architecture makes no requirements as to how an OPES flow is
   negotiated, provided that it is consistent with the security policy



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   (Section 3) of each administrative domain that hosts the OPES
   entities that are associated with the flow.

   The OPES architecture requires that each data dispatcher provides
   tracing facilities that allow the appropriate verification of its
   operation.  The OPES architecture requires that tracing be feasible
   on the OPES flow per OPES processor using  in-band annotation through
   header extensions on the application protocol that is used (e.g.,
   HTTP).  One of those annotations could be a URL with more detailed
   information on the transformation that occurred to the data on the
   OPES flow.  Future revisions of the architecture may provide for a
   tracing facility to be used for subsequent out-of-band analysis.







































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3. Security and Privacy Considerations

   Each data flow must be secured in accordance with several policies.
   The primary stakeholders are the data consumer and the data provider.
   The secondary stakeholders are the entities to which they may have
   delegated their trust.  The other stakeholders are the owners of the
   callout servers.  Any of these parties may be participants in the
   OPES architecture.

   These parties must have a model, explicit or implicit, describing
   their trust policy; which of the other parties are trusted to operate
   on data, and what security enhancements are required for
   communication.  The trust might be delegated for all data, or it
   might be restricted to granularity as small as an application data
   unit.

   All parties that are involved in enforcing policies must communicate
   the policies to the parties that are involved.  These parties are
   trusted to adhere to the communicated policies.

   In order to delegate fine-grained trust, the parties must convey
   policy information by implicit contract, by a setup protocol, by a
   dynamic negotiation protocol, or in-line with application data
   headers.

3.1 Trust Domains

   The delegation of authority starts at either a data consumer or data
   provider and moves to more distant entities in a "stepwise" fashion.
   Stepwise means A delegates to B and B delegates to C and so force.
   The entities thus "colored" by the delegation are said to form a
   trust domain with respect to the original delegating party.  Here,
   "Colored" means that if the first step in the chain is the data
   provider, then the stepwise delegation "colors" the chain with that
   data "provider" color.  The only colors that are defined are data the
   "provider" and the data "consumer".  An OPES processor may be in
   several trust domains at any time.  There is no restriction on
   whether the OPES processors are authorized by data consumers and/or
   data providers.  The original party has the option of forbidding or
   limiting redelegation.

   An OPES processor must have a representation of its trust domain
   memberships that it can report in whole or in part for tracing
   purposes.  It must include the name of the party which delegated each
   privilege to it.






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3.2 Primary data flow

   The primary data flow occurs between the data provider and the data
   consumer.  OPES must not interfere with the capability of these
   parties to use end-to-end authentication and confidentiality.

   If the primary parties want the assurance that their data does not
   appear in plaintext on network links, but they will permit use of
   plaintext on OPES processors and/or callout servers, then the OPES
   processors must use authentication and encryption between "hops".

   A separate security association must be used for each channel
   established between two OPES processors.

3.3 Callout protocol

   The determination of whether or not OPES processors will use the
   measures that are described in the previous section during their
   communication with callout servers depends on the details of how the
   primary parties delegated trust to the OPES processors and the trust
   relationship between the OPES processors and the callout server.  If
   the OPES processors are in a single administrative domain with strong
   confidentiality guarantees, then encryption may be optional.  In
   other cases, encryption and strong authentication would be at least
   strongly recommended.

   If the delegation mechanism names the trusted parties and their
   privileges in some way that permits authentication, then the OPES
   processors will be responsible for enforcing the policy and for using
   authentication as part of that enforcement.

   The callout servers must be aware of the policy governing the
   communication path.  They must not, for example, communicate
   confidential information to auxiliary servers outside the trust
   domain.

   A separate security association must be used for each channel
   established between an OPES processor and a callout server.  The
   channels must be separate for different primary parties.

3.4 Privacy

   Some data from data consumers is considered "private" or "sensitive",
   and OPES processors must both advise the primary parties of the their
   privacy policy and respect the policies of the primary parties.  The
   privacy information must be conveyed on a per-flow basis.

   The callout servers must also participate in handling of private



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   data, and they must be prepared to announce their own capabilities
   and to enforce the policy required by the primary parties.

3.5 Establishing trust

   The OPES processor will have configuration policy specifying what
   privileges the callout servers have and how they are to be
   identified.  This is especially critical for third-party (fourth-
   party, etc.) callout servers.  OPES uses standard protocols for
   authenticating and otherwise security communication with callout
   servers.

   An OPES processor will have a trusted method for receiving
   configuration information such as rules for the data dispatcher,
   trusted callout servers, primary parties that opt-in or opt-out of
   individual services, etc.

3.6 End-to-end Integrity

   Digital signature techniques can be used to mark data changes in such
   a way that a third-party can verify that the changes are or are not
   consistent with the originating party's policy.  This requires an
   inline manner of specifying policy and its binding to data, a trace
   of changes and the party making the changes, and strong identities
   and authentication methods.

   Strong end-to-end integrity can fulfill some of the functions
   required by "tracing".























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4. Summary

   Although the architecture supports a wide range of cooperative
   transformation services, it has few requirements for
   interoperability.

   The necessary and sufficient elements are specified in the following
   documents:

   o  the OPES ruleset schema [6] which defines the syntax and semantics
      of the rules interpreted by a data dispatcher; and,

   o  the OPES callout protocol (OCP) [7] which defines the protocol
      between a data dispatcher and a callout server.





































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References

   [1]  McHenry, S., et. al, "OPES Scenarios and Use Cases", Internet-
        Draft TBD, May 2002.

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

   [3]  Westerinen, A., Schnizlein, J., Strassner, J., Scherling, M.,
        Quinn, B., Herzog, S., Huynh, A., Carlson, M., Perry, J. and S.
        Waldbusser, "Terminology for Policy-Based Management", RFC 3198,
        November 2001.

   [4]  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.

   [5]  OPES working group, "OPES Service Authorization and Enforcement
        Requirements", Internet-Draft TBD, May 2002.

   [6]  OPES working group, "OPES Ruleset Schema", Internet-Draft TBD,
        May 2002.

   [7]  OPES working group, "OPES Callout Protocol and Tracing Protocol
        Requirements", Internet-Draft TBD, May 2002.


Authors' Addresses

   Abbie Barbir
   Nortel Networks
   3500 Carling Avenue
   Nepean, Ontario  K2H 8E9
   Canada

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


   Robin Chen
   AT&T Labs
   Room E219,  180 Park Avenue
   Florham Park, NJ  07932
   US

   Phone: +1 973 360 8653
   EMail: chen@research.att.com



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   Markus Hofmann
   Bell Labs/Lucent Technologies
   Room 4F-513
   101 Crawfords Corner Road
   Holmdel, NJ  07733
   US

   Phone: +1 732 332 5983
   EMail: hofmann@bell-labs.com


   Hilarie Orman
   The Purple Streak Development

   EMail: ho@alum.mit.edu


   Reinaldo Penno
   Nortel Networks
   2305 Mission College Boulevard
   San Jose, CA  95134
   US

   EMail: rpenno@nortelnetworks.com


   Gary Tomlinson
   Cacheflow

   EMail: gary@tomlinsongroup.net





















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Appendix A. Acknowledgements

   The authors gratefully acknowledge the contributions of: Marshall T.
   Rose.  (more to come, soon...)















































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Full Copyright Statement

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

   This document and translations of it may be copied and furnished to
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Acknowledgement

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



















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