XCON Working Group M. Barnes Internet-Draft Nortel Intended status: Standards Track C. Boulton Expires: May 22, 2008 Avaya H. Schulzrinne Columbia University November 19, 2007 Centralized Conferencing Manipulation Protocol draft-barnes-xcon-ccmp-03 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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 May 22, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract The Centralized Conferencing Manipulation Protocol (CCMP) defined in this document provides the mechanisms to create, change and delete objects related to centralized conferences, including participants, their media and their roles. The protocol relies on web services and SIP event notification as its infrastructure, but can control Barnes, et al. Expires May 22, 2008 [Page 1] Internet-Draft CCMP November 2007 conferences that use any signaling protocol to invite users. CCMP is based on the Simple Object Access Protocol (SOAP), with the data necessary for the interactions specified via Web Services Description Language (WSDL). Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5. System Architecture . . . . . . . . . . . . . . . . . . . . . 5 6. Conference Object, Users and Identifiers . . . . . . . . . . . 7 6.1. Conference Object . . . . . . . . . . . . . . . . . . . . 7 6.2. Conference Users and Participants . . . . . . . . . . . . 7 7. Protocol Operations . . . . . . . . . . . . . . . . . . . . . 8 7.1. Options . . . . . . . . . . . . . . . . . . . . . . . . . 9 7.2. Retrieve . . . . . . . . . . . . . . . . . . . . . . . . . 9 7.3. Create . . . . . . . . . . . . . . . . . . . . . . . . . . 9 7.4. Change . . . . . . . . . . . . . . . . . . . . . . . . . . 10 7.5. Delete . . . . . . . . . . . . . . . . . . . . . . . . . . 11 8. Protocol Operations on Conference Objects . . . . . . . . . . 11 8.1. Identifying a Conference Instance . . . . . . . . . . . . 11 8.2. Constructing a CCMP request . . . . . . . . . . . . . . . 11 8.3. Handling Responses and Error Conditions . . . . . . . . . 12 9. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 10. Transaction Model . . . . . . . . . . . . . . . . . . . . . . 15 11. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 15 12. WSDL Definition . . . . . . . . . . . . . . . . . . . . . . . 17 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 14. Security Considerations . . . . . . . . . . . . . . . . . . . 19 15. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19 16. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19 16.1. Normative References . . . . . . . . . . . . . . . . . . . 19 16.2. Informative References . . . . . . . . . . . . . . . . . . 20 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20 Intellectual Property and Copyright Statements . . . . . . . . . . 22 Barnes, et al. Expires May 22, 2008 [Page 2] Internet-Draft CCMP November 2007 1. Introduction The Framework for Centralized Conferencing defines a signaling- agnostic framework, naming conventions and logical entities required for constructing advanced conferencing systems. A primary concept introduced in the framework and for centralized conferencing is the existence of a conference object. The conference object is a logical representation of a conference instance, which represents the current state and capabilities of a conference. The Centralized Conferencing Manipulation Protocol (CCMP) defined in this document allows the creation, manipulation and deletion of a conference object by authenticated and authorized clients. This includes adding and removing participants, changing their roles, as well as adding and removing media streams and associated end points. CCMP is based on the three fundamental components of a centralized conference: the conference as a whole, users and media. CCMP implements a client-server model. The server is the Conference Control Server defined in the XCON framework , while clients can either be signaling end points, such as Session Initiation Protocol (SIP) user agents, or control-only agents that do not contribute media to the conference. CCMP manipulates conferences based on their semantic properties and is based on a client-server Remote Procedure Call (RPC) mechanism, with the Simple Object Access Protocol (SOAP) [4] and [5] used to carry out the appropriate client-server protocol transactions. The common information contained in conference objects is defined using an XML representation such as the one introduced in the Conference Package [10] and the XCON data model. These data structures are used as the basis for the Web Services Description Language (WSDL) [3] definition and XML schema. This document first provides some background on the motivations associated with the design of CCMP in Section 4 followed by a brief discussion of the system architecture in Section 5. The protocol operations are then detailed in Section 7, with a discussion of the key elements in the conference object in Section 6. The practical sequence of protocol operations is discussed in Section 8, with examples provided in Section 9. An XML schema is provided in Section 11. WSDL information is detailed in Section 12. Barnes, et al. Expires May 22, 2008 [Page 3] Internet-Draft CCMP November 2007 2. Conventions In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119 [1] and indicate requirement levels for compliant implementations. 3. Terminology This document reuses the terminology defined in the Framework for Centralized Conferencing and High-Level Requirements for Tightly Coupled SIP Conferencing [8]. In addition, the following acronyms and terms are used in this document: SOAP: Simple Object Access Protocol.[4][5] WSDL: Web Services Description Language.[3] WSDL is an XML format for describing network services as a set of endpoints operating on messages containing either document-oriented or procedure-oriented information. W3C: World Wide Web Consortium. The organization that developed the SOAP and WSDL specifications referenced within this document. 4. Motivation SOAP is chosen as the RPC mechanism due to its compatibility with the requirements for the conference control protocol as introduced in the framework and data model for centralized conferencing. SOAP is a lightweight protocol for exchange of information in a decentralized, distributed environment. It is an XML based protocol that consists of three parts: an envelope that defines a framework for describing what is in a message to process it, a set of encoding rules for expressing instances of application-defined datatypes, and a convention for representing remote procedure calls and responses. SOAP allows the re-use of libraries, servers and other infrastructure and provides a convenient mechanism for the formal definition of protocol syntax using Web Services Description Language (WSDL). WSDL is an XML format for describing network services as a set of endpoints operating on messages containing either document-oriented or procedure-oriented information. The operations and messages are described abstractly, and then bound to a concrete network protocol and message format to define an endpoint. Related concrete endpoints are combined into abstract endpoints (services). WSDL is extensible to allow description of endpoints and their messages regardless of what message formats or network protocols are used to communicate, Barnes, et al. Expires May 22, 2008 [Page 4] Internet-Draft CCMP November 2007 however, the only bindings described in this document describe how to use WSDL in conjunction with SOAP. It is likely that implementations and future standardization work will add more conference attributes and parameters. There are three types of extensions. The first, simplest type of extension adds elements to the overall conference, media descriptions or descriptions of users. The XML namespace mechanism makes such extensions relatively easy, although implementations still have to deal with implementations that may not understand the new namespaces. The Options operation (Section 7.1) allows clients to determine the capabilities of a specific server, reflected by the specific blueprints supported by that server. A second type of extension replaces the conference, user or media objects with completely new schema definitions, i.e., the namespaces for these objects themselves differ from the basic one defined in this document. As long as the Options request remains available and keeps to a mutually-understood definition, a compatible client and server will be able to bootstrap themselves into using these new objects. Finally, it is conceivable that new object types are needed beyond the core conference, user and media objects and their children. These would also be introduced by namespaces. 5. System Architecture CCMP supports the framework for centralized conferencing . Figure 1 depicts a subset of the 'Conferencing System Logical Decomposition' architecture from the framework and data model for centralized conferencing document. It illustrates the role that CCMP assumes within the overall centralized architecture. Barnes, et al. Expires May 22, 2008 [Page 5] Internet-Draft CCMP November 2007 ........................................................ . Conferencing System . . . . +---------------------------------------+ . . | C O N F E R E N C E O B J E C T | . . +-+-------------------------------------+ | . . | C O N F E R E N C E O B J E C T | | . . +-+-------------------------------------+ | | . . | C O N F E R E N C E O B J E C T | | | . . | | | | . . | | |-+ . . | |-+ . . +---------------------------------------+ . . ^ . . | . . v . . +-------------------+ . . | Conference Control| . . | Server | . . +-------------------+ . . ^ . .........................|.............................. | |Conference |Control |Protocol | | .........................|.............................. . V . . +----------------+ . . | Conference | . . | Control | . . | Client | . . +----------------+ . . . . Conferencing Client . ........................................................ Figure 1: Conference Client Interaction CCMP serves as the Conference Control Protocol, allowing the conference control client to interface with the conference object maintained by the conference control server, as represented in Figure 1. Conference Control is one set of functionality for advancing conferencing supported by a conferencing client. Other functions are discussed in the framework and data model for Barnes, et al. Expires May 22, 2008 [Page 6] Internet-Draft CCMP November 2007 centralized conferencing document and related documents. 6. Conference Object, Users and Identifiers This section provides an overview of the conference object and conference users in relation to the CCMP protocol. The identifiers used in CCMP for the conference object (XCON_URI) and conference user (XCON_USERID) are introduced in the XCON framework and defined in the XCON data model. 6.1. Conference Object Conference objects feature a simple dynamic inheritance-and-override mechanism. Conference objects are linked into a tree, where each tree node inherits attributes from its parent node. The roots of these inheritance trees are also known as "blueprints". Nodes in the inheritance tree can be active conferences or simply descriptions that do not currently have any resources associated with them. An object can mark certain of its properties as unalterable, so that they cannot be overridden. The schema for the conference object is defined in the XCON data model. Conference objects are uniquely identified by the XCON_URI. A client MAY add a parent element that indicates the parent from which the conference is to inherit values. When creating conferences, the XCON_URI included by the client is only a suggestion. To avoid identifier collisions and to conform to local server policy, the conference control server MAY choose a different identifier. 6.2. Conference Users and Participants Each conference can have zero or more users. All conference participants are users, but some users may have only administrative functions and do not contribute or receive media. Users are added one user at a time to simplify error reporting. Users are inherited as well, so that it is easy to set up a conference that has the same set of participants or a common administrator. The Conference Control Server creates individual users, assigning them a unique Conference User Identifier (XCON_URI). A variety of elements defined in the common conference information as specified in the XCON data model. are used to determine how a specific user expects and is allowed to join a conference as participants, or users with specific privileges (e.g., observer). For example, the attribute in the defines how the caller joins the conference, with a set of defined XML elements, namely Barnes, et al. Expires May 22, 2008 [Page 7] Internet-Draft CCMP November 2007 for users that are allowed to dial in and for users that the conference focus will be trying to reach, etc. is the default. If the conference is currently active, dial-out users are contacted immediately; otherwise, they are contacted at the start of the conference. The conference control server assigns a unique Conference User Identifier (XCON_USERID) to each user. The conference control server uses the XCON_USERID to change or delete elements. Depending upon policies and privileges, specific users MAY also manipulate elements. In many conferences, users dial in if they know the XCON_URI and an access code shared by all conference participants. This user is initially represented in the data by a element without an entity attribute. Only the (default) type of is permitted for this type of user. The users are identified, in the entity attribute, by their call signaling URL, such as their SIP URL, tel URI [7] , etc. In cases where there is no such URI ( e.g., because a PSTN caller has blocked caller-ID delivery) the server assigns a locally-unique URI, such as a locally-scoped tel URI. The conference control server assigns a unique Conference User Identifier (XCON_USERID) to these users when they dial in to join the conference. If the user supports the notification event package [11], they can receive their XCON_USERID, thus allowing them to also manipulate the attribute in the conference object. 7. Protocol Operations The primary function of the protocol defined within this document is to provide a conference control client with the ability to carry out specific operations on a conference object. This section describes the generic behavior of the core protocol operations on conference objects. Each object has four basic operations: retrieve, create, change and delete. The XCON_URI as discussed in Section 6.1 is the target for each of these operations. To simplify operations, a conference control server treats certain parameters as suggestions, as noted in the object description. If the conference control server cannot set the parameter to the values desired, it picks the next best value, according to local policy and returns the values selected in the response. If the client is not satisfied with these values, it simply deletes the object. There is also a querying mechanism ("options") to ascertain the namespaces understood by the server, thus any elements with namespaces not understood by the server are to be ignored by the Barnes, et al. Expires May 22, 2008 [Page 8] Internet-Draft CCMP November 2007 server. This allows a client to include optional elements in requests without having to tailor its request to the capabilities of each server. A conference control client and conference control server MUST provide the ability to action all of the protocol operations in this section and MUST fully implement the SOAP WSDL schema defined in Section 12 which uses HTTP operations as the transport mechanism. 7.1. Options The "options" operation is used by a client to query a system for its capabilities and doesn't pertain to a particular conference object. In this document, the response returns the XML namespaces that the server understands and the namespaces to be used in responses that it requires the client to understand. Future work may add more global capabilities rather than conferencing system specific. Within the conferencing system, the namespaces correlate with blueprints, as specified in the XCON framework. The blueprints are comprised of common conference information initialized to specific values and ranges. 7.2. Retrieve The "retrieve" operation returns the full XML document describing the conference object in its current state including all inherited values. Elements may be marked by attributes, in particular, whether they are specific to this instance or have been inherited from the parent node. The "retrieve" operation is used by a client to query a system for a specific template in the form of a blueprint prior to the creation of a conference. The "retrieve" operation is also used to get the current representation of a specific conference object for a conference reservation or an active conference. In this case, the operation requires the unique conference identifier (XCON_URI) be provided by the client. To simplify operations HTTP GET can also be used directly on these URLs, so that simple systems that need to only obtain data about conference objects do not need a full SOAP implementation. 7.3. Create The "create" operation is used by a client to create and reserve a conference object. The creation of the conference object can be explicit by requesing it to be created based upon a specific blueprint. When the creation of a conference object is implicit, with no specific blueprint specified, the creation and reservation of the conference instance is based on the default conference object. Barnes, et al. Expires May 22, 2008 [Page 9] Internet-Draft CCMP November 2007 The default conference object is specific to a conferencing system and its specification is outside the scope of this document. When creating conferences, any XCON_URI included by the client is considered as input. To avoid identifier collisions and to conform to local server policy, the conference control server MAY choose a different identifier. The identifier is returned in the response. In addition, the conference description MAY contain a calendar element, in the iCal format in XML rendition defined in CPL [6] or (preferable, if available as stable reference) xCal [12]. This description indicates when the conference is active. The conference server may only offer a subset of the dates, indicated by the 203 response. The "create" operation may also be used to create a new conference user. The response to this operation includes the XCON_USERID. To simplify operations HTTP PUT can also be used to create a new objects. 7.4. Change The "change" operation updates the conference object as referenced by the XCON_URI included in the. A request which attempts to change a non-existing object is an error, as is a request which attempts to change a parameter that is inherited from a protected element. During the lifetime of a conference, this conference control operation is used by a conference control client to manipulate a conference object. This includes the ability to pass relevant fragments of the conference object, to manipulate specific elements in the conference object, along with relevant operation types (add, delete, modify, etc.). Upon receipt of a "change" operation, the conference control serve updates the specific elements in the referenced conference object. Object properties that are not explicitly changed, remain as-is. This approach allows a conference control client to manipulate objects created by another application even if the manipulating application does not understand all object properties. [Editor's note: the mechanism for manipulation of specific elements in the conference object requires further detail.] To simplify operations HTTP POST can also be used to change objects. Barnes, et al. Expires May 22, 2008 [Page 10] Internet-Draft CCMP November 2007 7.5. Delete This conference control operation is used to delete the current representation of a conference object and requires the unique conference identifier (XCON_URI) be provided by the client. A request which attempts to delete a conference object that is being referenced by a child object is an error. 8. Protocol Operations on Conference Objects The primary function of the conference control protocol is to provide a conference control client with the ability to carry out specific operations on a conference object. As mentioned previously, SOAP is used as the the XML RPC mechanism to fulfill such operations. A conference control client wishing to perform an operation(s) on a particular conference object follows a series of steps as detailed in the following sections. 8.1. Identifying a Conference Instance Typically, for any operation that is to be carried out on a conference object, the XCON_URI is required. Operations can be initiated from a conference control client for the purpose of creating a conference object. To achieve this, an operation is executed without specifying a unique conference object identifier. If the operation is successful, the unique conference object identifier is included in the SOAP response transaction. 8.2. Constructing a CCMP request The construction of the SOAP envelope associated with a conference control request message complies fully with the WSDL, as defined in Section 12. Construction of a valid conference control protocol message is based upon the operations defined in Section 7, depending upon the function and associated information desired by the conference control client. [Editors Note: It is fully expected that the Operations will involve asynchronous transactions. This section will be expanded at a later date to allow asynchronous transactions. ]. Barnes, et al. Expires May 22, 2008 [Page 11] Internet-Draft CCMP November 2007 8.3. Handling Responses and Error Conditions Error conditions specific to individual operations are described below, but there are several general conditions that can occur for any object and operation. Errors are described by a combination of a status code and a reason phrase. As in SIP and HTTP, responses contain a three-digit numeric status code and a textual response, possibly in different languages. The numeric status codes are described below. For easy recognition, they correspond to SIP response codes where this makes sense, but the name spaces are otherwise distinct. [Editor's Note: Alternatively, should we define XML tokens for errors rather than following this SIP/HTTP model? ] Barnes, et al. Expires May 22, 2008 [Page 12] Internet-Draft CCMP November 2007 +----------------------+----------------------+---------------------+ | Code | Reason phrase | Explanation | +----------------------+----------------------+---------------------+ | 200 | OK | successful | | 202 | Pending | notification to | | | | follow | | 203 | Modified | The object was | | | | created, but may | | | | differ from the | | | | request. | | 302 | Moved temporarily | An object should be | | | | referenced by a | | | | different | | | | identifier. | | 400 | Bad request | | | 401 | Unauthorized | | | 403 | Forbidden | | | 404 | Object not found | | | 405 | Method not allowed | user is not allowed | | | | to perform this | | | | method, such as | | | | 'create', on the | | | | object | | 408 | Request timeout | | | 409 | Cannot delete since | | | | it is a parent for | | | | another node | | | 410 | Cannot change since | | | | it is marked as | | | | protected | | | 500 | Server internal | | | | error | | | 501 | Not implemented | The function or | | | | object has not been | | | | implemented. | +----------------------+----------------------+---------------------+ Figure 2: Response Codes 9. Examples The examples below omits the standard SOAP header and wrappers, i.e., the part below is simply the of the response. The first example creates a new conference. The conference URIs are proposals by the client to the server; the server makes the final Barnes, et al. Expires May 22, 2008 [Page 13] Internet-Draft CCMP November 2007 decision as to whether it will honor those requests. create http://example.com/conf200 Agenda: This month's goals sips:conf223@example.com participation http://sharep/salesgroup/ web-page http://example.com/conf233 control Figure 3: Create Request Example The response to this request is shown below; it returns the object identifier as a URL and the final conference description, which may modify the description offered by the user. 200 OK [... modified conference description ...] Figure 4: Create Response Example Barnes, et al. Expires May 22, 2008 [Page 14] Internet-Draft CCMP November 2007 The request below adds a user to the conference identified by the conference URI. create receiving Figure 5: Add User Example 10. Transaction Model The transaction model for CCMP complies fully with SOAP version 1.2 as defined by W3C in [4] and [5]. 11. XML Schema [Editor's note: This current version is currently bare bones. It will be enhanced and updated and also needs to align with the fundamental XCON data model that is agreed.] Barnes, et al. Expires May 22, 2008 [Page 15] Internet-Draft CCMP November 2007 Barnes, et al. Expires May 22, 2008 [Page 16] Internet-Draft CCMP November 2007 Figure 6 12. WSDL Definition The following provides the WSDL definition for conference control and manipulation, using the the XML schema defined in Section 11 as a basis. Barnes, et al. Expires May 22, 2008 [Page 18] Internet-Draft CCMP November 2007 Figure 7 13. IANA Considerations TODO 14. Security Considerations Access to conference control functionality needs to be tightly controlled to keep attackers from disrupting conferences, adding themselves to conferences or engaging in theft of services. Implementors need to deploy standard HTTP and SOAP authentication and authorization mechanisms. Since conference information may contain secrets such as participant lists and dial-in codes, all conference control information SHOULD be carried over TLS (HTTPS). 15. Acknowledgments The authors appreciate the feedback provided by Simon Pietro Romano and Dave Morgan. 16. References 16.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. [3] Chinnici, R., Moreau, J., Ryman, A., and S. Weerawarana, "Web Services Description Language (WSDL) Version 2.0 Part 1: Core Language", W3C CR CR-wsdl20-20051215, December 2005. [4] Gudgin, M., Moreau, J., Mendelsohn, N., Hadley, M., and H. Nielsen, "SOAP Version 1.2 Part 1: Messaging Framework", World Wide Web Consortium FirstEdition REC-soap12-part1-20030624, June 2003, . Barnes, et al. Expires May 22, 2008 [Page 19] Internet-Draft CCMP November 2007 [5] Mendelsohn, N., Gudgin, M., Hadley, M., Nielsen, H., and J. Moreau, "SOAP Version 1.2 Part 2: Adjuncts", World Wide Web Consortium FirstEdition REC-soap12-part2-20030624, June 2003, . 16.2. Informative References [6] Lennox, J., Wu, X., and H. Schulzrinne, "Call Processing Language (CPL): A Language for User Control of Internet Telephony Services", RFC 3880, October 2004. [7] Schulzrinne, H., "The tel URI for Telephone Numbers", RFC 3966, December 2004. [8] Levin, O. and R. Even, "High-Level Requirements for Tightly Coupled SIP Conferencing", RFC 4245, November 2005. [9] Levin, O. and G. Camarillo, "The Session Description Protocol (SDP) Label Attribute", RFC 4574, August 2006. [10] Rosenberg, J., Schulzrinne, H., and O. Levin, "A Session Initiation Protocol (SIP) Event Package for Conference State", RFC 4575, August 2006. [11] Srinivasan, S. and R. Even, "Conference event package data format extension for centralized conferencing", draft-srinivasan-xcon-eventpkg-extensions-02 (work in progress), August 2007. [12] Royer, D., "iCalendar in XML Format (xCal-Basic)", draft-royer-calsch-xcal-03 (work in progress), October 2005. Authors' Addresses Mary Barnes Nortel 2201 Lakeside Blvd Richardson, TX Email: mary.barnes@nortel.com Barnes, et al. Expires May 22, 2008 [Page 20] Internet-Draft CCMP November 2007 Chris Boulton Avaya Building 3 Wern Fawr Lane St Mellons Cardiff, South Wales CF3 5EA Email: cboulton@avaya.com Henning Schulzrinne Columbia University Department of Computer Science 450 Computer Science Building New York, NY 10027 Email: hgs+xcon@cs.columbia.edu Barnes, et al. Expires May 22, 2008 [Page 21] Internet-Draft CCMP November 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Barnes, et al. Expires May 22, 2008 [Page 22]