Network Working Group Abbie. Barbir Internet-Draft Nortel Networks Expires: December 10, 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 June 11, 2002 An Architecture for Open Pluggable Edge Services (OPES) draft-ietf-opes-architecture-01 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 groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http:// www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on December 10, 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 Barbir , et al. Expires December 10, 2002 [Page 1] Internet-Draft OPES Architecture June 2002 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 . . . . . . . . . . . . . . . . . . . . . . . 9 3. Security and Privacy Considerations . . . . . . . . . . . . . 11 3.1 Trust Domains . . . . . . . . . . . . . . . . . . . . . . . . 11 3.2 Callout protocol . . . . . . . . . . . . . . . . . . . . . . . 12 3.3 Privacy . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.4 Establishing trust . . . . . . . . . . . . . . . . . . . . . . 12 3.5 End-to-end Integrity . . . . . . . . . . . . . . . . . . . . . 13 4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 15 A. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17 Full Copyright Statement . . . . . . . . . . . . . . . . . . . 18 Barbir , et al. Expires December 10, 2002 [Page 2] Internet-Draft OPES Architecture June 2002 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 in may be beneficial to provide a customization service at network location instead of deploying it at either the provider or the consumer host. For certain services performed on end-user behalf this may be the only option of service deployment. 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. Barbir , et al. Expires December 10, 2002 [Page 3] Internet-Draft OPES Architecture June 2002 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 OPES ruleset 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. In the current work, the data provider and data consumer applications are not considered as OPES entities. 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 logical implementation stack of an OPES entity is summarized in Figure 1. Barbir , et al. Expires December 10, 2002 [Page 4] Internet-Draft OPES Architecture June 2002 --------------------------------------------------------------------- +-------------+ |OPES service | | Application | | | +-------------+ | Data | | Dispatcher | | | +-------------+ | | | HTTP | | | +-------------+ | TCP/IP | +-------------+ | ... | +-------------+ Figure 1: OPES Logical Implementation --------------------------------------------------------------------- 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, zero or more OPES service applications, and zero or more data dispatchers. In order to understand the trust relationships between OPES entities, each is labeled as residing in an administrative domain. 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. Barbir , et al. Expires December 10, 2002 [Page 5] Internet-Draft OPES Architecture June 2002 --------------------------------------------------------------------- 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 OPES policy regarding services and the data provided to them is determined by a ruleset consisting of OPES rules. The rules consist of a set of conditions and related actions. The ruleset is the superset of all OPES rules on the processor. The OPES ruleset determines which service applications will operate on a data stream. The communication of data stream elements to an application is performed by data dispatchers. In this model, all data filters are invoked for all data. In order to ensure predictable behavior the OPES architecture Barbir , et al. Expires December 10, 2002 [Page 6] Internet-Draft OPES Architecture June 2002 requires the use of a standardized schema for the purpose of defining and interpreting the ruleset. The OPES architecture does not require 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 evaluation of OPES ruleset determines which service applications will operate on a data stream. How the ruleset is evaluated is not the subject of the architecture, except to note that it must result in the same unambiguous result in all implementations. In some cases it may be useful for the OPES processor to distribute the responsibility of service evaluation 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 Barbir , et al. Expires December 10, 2002 [Page 7] Internet-Draft OPES Architecture June 2002 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 can be local or remote. In this model, OPES applications may be executed either on the same processor (or even in the same application environment) with the dispatcher or on a different OPES processor through OCP. The general interaction situation is depicted in Figure 4, which illustrates the positions and interaction of different components of OPES architecture. --------------------------------------------------------------------- +--------------------------+ | +----------+ | | | OPES | | | | service | | +----------------+ | | appl | | | Callout Server | | +----------+ | | | | || | | +--------+ | | +----------------------+ | | | OPES | | | | data dispatcher | | | | Service| | | +----------------------+ | | | App2 | | | | HTTP | OCP | | | +--------+ | | +------------| |==========| OCP | | | | |---------+ | | +--------+ | | | TCP/IP | | +----------------+ =========| |=============== OPES Data Flow ==== | +------------+ | +--------------------------+ Figure 4: Interaction of OPES Entities --------------------------------------------------------------------- 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 determain which service applications to invoke for which data flow. Accordingly, the data Barbir , et al. Expires December 10, 2002 [Page 8] Internet-Draft OPES Architecture June 2002 dispatcher constitutes an enhanced Policy Enforcement Point (PEP), where policy rules are evaluated, service-specific data handlers and state information are maintained, as depicted in Figure 5. --------------------------------------------------------------------- +----------+ | callout | | server | +----------+ || || || || +---------------------------+ | +----------+ || | | | OPES | || | | | service | || | | | appl | || | | +----------+ || | | +----------------------+ | OPES flow <---->| | data dispatcher/PEP | | <----> OPES flow | +----------------------+ | | OPES | | processor | +--------------------------+ Figure 5: 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 (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. One of those annotations could be a URL with more detailed information on the transformation that occurred to the data on the OPES flow. Barbir , et al. Expires December 10, 2002 [Page 9] Internet-Draft OPES Architecture June 2002 Future revisions of the architecture may provide for a tracing facility to be used for subsequent out-of-band analysis. Providing the ability for in-band annotation MAY require header extensions on the application protocol that is used (e.g., HTTP). However, the presence of an OPES processor in the data request/ response flow SHALL NOT interfere with the operations of non-OPES aware clients and servers. OPES processors, content server and content consumer MAY use OPES extensions to the base protocol (HTTP), but support of these extensions SHALL NOT be required. OPES processors must obey tracing, reporting and notification requirements set by the center of authority in the trust domain to which OPES processor belongs. As part of these requirements OPES processor may be instructed to reject or ignore such requirements that originate from other trust domains. Barbir , et al. Expires December 10, 2002 [Page 10] Internet-Draft OPES Architecture June 2002 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 forth. 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 the data "provider" and the data "consumer". Delegation of authority (coloring) propagates from the content producer start of authority or from the content consumer start of authority, that may be different from the end points in the data flow. 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 Barbir , et al. Expires December 10, 2002 [Page 11] Internet-Draft OPES Architecture June 2002 privilege to it. 3.2 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. 3.3 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 data, and they must be prepared to announce their own capabilities and to enforce the policy required by the primary parties. 3.4 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. Barbir , et al. Expires December 10, 2002 [Page 12] Internet-Draft OPES Architecture June 2002 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. 3.5 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". Barbir , et al. Expires December 10, 2002 [Page 13] Internet-Draft OPES Architecture June 2002 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. Barbir , et al. Expires December 10, 2002 [Page 14] Internet-Draft OPES Architecture June 2002 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 Barbir , et al. Expires December 10, 2002 [Page 15] Internet-Draft OPES Architecture June 2002 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 Barbir , et al. Expires December 10, 2002 [Page 16] Internet-Draft OPES Architecture June 2002 Appendix A. Acknowledgements The authors gratefully acknowledge the contributions of: Marshall T. Rose, John Morris, Oskar Batuner, Mark Baker and Ian Cooper. Barbir , et al. Expires December 10, 2002 [Page 17] Internet-Draft OPES Architecture June 2002 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. Barbir , et al. Expires December 10, 2002 [Page 18]