Network Working Group M. Douglass Internet-Draft Spherical Cow Group Intended status: Standards Track August 26, 2015 Expires: February 27, 2016 DAV Server Information Object draft-douglass-server-info-01 Abstract This specification describes a new XML object that can be retrieved from hosts to discover services, features and limits for that host or domain. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on February 27, 2016. Copyright Notice Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Douglass Expires February 27, 2016 [Page 1] Internet-Draft Dav Server Information Object August 2015 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions Used in This Document . . . . . . . . . . . . . . 3 2.1. Service . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2. Feature . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Server Information Document Use . . . . . . . . . . . . . . . 4 3.1. Server Information Location and Retrieval . . . . . . . . 4 3.1.1. DAV:server-info-href property . . . . . . . . . . . . 4 3.1.2. Server Information Retrieval . . . . . . . . . . . . 5 3.1.3. Server Information Synchronization . . . . . . . . . 5 3.1.3.1. Header: server-info-token . . . . . . . . . . . . 5 3.1.3.2. Header: if-not-server-info-token . . . . . . . . 6 4. Server Information Document Structure . . . . . . . . . . . . 6 4.1. Server Information server-info element . . . . . . . . . 6 4.2. Server Information services element . . . . . . . . . . . 6 4.2.1. Server Information service element . . . . . . . . . 6 4.3. Server Information features element . . . . . . . . . . . 7 4.3.1. Server Information feature element . . . . . . . . . 7 5. XML Element Definitions . . . . . . . . . . . . . . . . . . . 8 5.1. server-info XML element . . . . . . . . . . . . . . . . . 8 5.2. token XML element . . . . . . . . . . . . . . . . . . . . 8 5.3. services XML element . . . . . . . . . . . . . . . . . . 8 5.4. service XML element . . . . . . . . . . . . . . . . . . . 9 5.5. name XML element . . . . . . . . . . . . . . . . . . . . 9 5.6. href XML element . . . . . . . . . . . . . . . . . . . . 9 5.7. features XML element . . . . . . . . . . . . . . . . . . 9 6. WebDAV Features . . . . . . . . . . . . . . . . . . . . . . . 9 6.1. DAV class-1 feature XML element . . . . . . . . . . . . . 10 6.2. DAV class-2 feature XML element . . . . . . . . . . . . . 10 6.3. DAV class-3 feature XML element . . . . . . . . . . . . . 11 6.4. DAV access control feature XML element . . . . . . . . . 11 6.5. DAV version control feature XML element . . . . . . . . . 11 6.6. DAV Extended mkcol feature XML element . . . . . . . . . 12 6.7. DAV bind feature XML element . . . . . . . . . . . . . . 12 6.8. DAV search feature XML element . . . . . . . . . . . . . 12 6.9. DAV quota feature XML element . . . . . . . . . . . . . . 13 6.10. DAV Sync Collection feature XML element . . . . . . . . . 13 6.11. DAV Add Member feature XML element . . . . . . . . . . . 13 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 14 7.1. WebDAV server information . . . . . . . . . . . . . . . . 14 8. Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 9. Security Considerations . . . . . . . . . . . . . . . . . . . 14 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14 12. Normative References . . . . . . . . . . . . . . . . . . . . 14 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 16 Douglass Expires February 27, 2016 [Page 2] Internet-Draft Dav Server Information Object August 2015 1. Introduction Any given host on a network may support a number of services. Each of those services will have limits or optional features. The advertising and discovery of services, features and limits is often through the use of properties and headers. As the number of services and features grows the amount of data and complexity of the requests grows. Additionally, headers and properties don't allow for caching mechanisms based on etags. A client has to fetch all the information and compare with its stored copies to determine if a service change has taken place. This specification defines a new XML document type which can be retrieved from a host and is easily extended to allow the description of complex services. The schema as described here only handles basic DAV services. Other specifications will extend this specification to define elements for other DAV based services. 2. Conventions Used in This Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 2.1. Service By service we mean an application running on one or more hosts at the network application layer and above. The service may provide data storage, manipulation, presentation, communication or other capabilities. The service may use a well defined protocol and is often implemented with a client-server relationship. A service will usually implement one or more features which may be defined by standard specifications. Services and features may also be constrained by various limits. Examples of services are o caldav o email o File servers Douglass Expires February 27, 2016 [Page 3] Internet-Draft Dav Server Information Object August 2015 2.2. Feature A feature is some functionality provided by a service. For example, a DAV based service may provide the versioning feature. Services need not support all features that are defined as an optional part of that service. Some features may depend on the authenticated state and/or the authorization of the authenticated principal. Examples of features are o DAV versioning. o DAV access control. o CalDAV scheduling. 3. Server Information Document Use A host will make the document available through one or more methods. Depending upon the endpoint and method of retrieval the retrieved document may describe one or more services. If a document provides information for more than one service it SHOULD contain information allowing clients to obtain information about each individual service only. This allows a client to determine what the actual limits and features are for the specific service. 3.1. Server Information Location and Retrieval 3.1.1. DAV:server-info-href property Name: server-info-href Namespace: DAV Purpose: To define the location of the server-info document. Protected: This property MAY be protected. PROPFIND behavior: This property SHOULD NOT be returned by a PROPFIND DAV:allprop request (as defined in Section 14.2 of [RFC4918]). COPY/MOVE behavior: This property value SHOULD be preserved in COPY and MOVE operations. Douglass Expires February 27, 2016 [Page 4] Internet-Draft Dav Server Information Object August 2015 Description: This property is needed for a client to determine where the server information document is located. If not present, then no document is available for the server. Definition: 3.1.2. Server Information Retrieval The document may be retrieved from the server by doing a PROPFIND on the .well_known (or any location on the service) for the D:server- info-href property defined above. Clients SHOULD retrieve the document in the context of a session and services SHOULD ensure the context is appropriate. Values in the returned document may differ depending on who is authenticated so a server SHOULD require authentication before returning server information for an authenticated service. 3.1.3. Server Information Synchronization While server features may not change frequently it may be important for clients to react rapidly when server features or limits change. Polling for changes is undesirable so this specification allows for informing clients when the server information has changed. The returned server-info document contains an opaque token which the client can use to determine if the server copy is different. This token is used in a number of places to aid client synchronization. 3.1.3.1. Header: server-info-token The server-info-token header takes as a value the current value of the token element in the server-info document. This header may be returned with a response at any time a server feels appropriate. It MAY be returned in response to a request containing an if-not-server-info-token header. The server-info-token header MUST be returned for an OPTIONS request. It SHOULD be returned if a client attempts to use an unsupported feature or misuse a feature or exceed a limit. Douglass Expires February 27, 2016 [Page 5] Internet-Draft Dav Server Information Object August 2015 3.1.3.2. Header: if-not-server-info-token The if-not-server-info-token header takes as a value the current token stored by the client. If that value matches the value stored by the server it SHOULD NOT return a server-info-token header. If they do not match the server MUST return a server-info-token header with the current value. If a new value is returned by the server the client should refetch a copy of the server info document. 4. Server Information Document Structure This specification defines a new XML document type "server-info". All XML elements in this specification are in the DAV name space. 4.1. Server Information server-info element At the top level of the document is a "server-info" element which encloses a change token, an optional "features" element and a "services" element ... ... ... If a "features" element appears inside the "server-info" element then the features apply to all services. 4.2. Server Information services element The "services" element appears once and contains 0 or more "service" elements each of which provides information about a service. NOTE: do the service have to be on the same host? I think not. 4.2.1. Server Information service element The "service" element contains the name and information about the location of that service and how to obtain a service specific server- info document. Douglass Expires February 27, 2016 [Page 6] Internet-Draft Dav Server Information Object August 2015 It may also contain a "features" element which lists features implemented by that service. For example: caldav https:cal.example.org//.well-known/caldav 4.3. Server Information features element The "features" element contains 0 or more elements each specifying a feature supported by that service. The "features" element may appear within the "server-info" element - in which case it applies to all services or it may appear inside a "service" element in which case it only applies to that service. When a single service is specified the features named SHOULD be accessible for the same authentication and authorization level. 4.3.1. Server Information feature element A feature is specified by an element defined in this document or by an element defined in the specification for that feature. WebDAV feature elements correspond to, but are not exactly the same as, the elements returned in the DAV header. Some features have no corresponding DAV header element. This may be because the feature is not available on all resources. The occurrence of a such a feature simple advertises the availability of that feature on some resources. Douglass Expires February 27, 2016 [Page 7] Internet-Draft Dav Server Information Object August 2015 For a service supporting this specification, the absence of a feature means that feature is NOT supported on any resource. For example, a calendar service may return the following which specifies a global set of features: 5. XML Element Definitions All elements defined here are in the "DAV:" namespace. 5.1. server-info XML element Name: server-info Purpose: Contains information about a single service. Definition: 5.2. token XML element Name: token Purpose: Contains an opaque token which changes when the document changes.. Definition: 5.3. services XML element Name: services Purpose: Contains information about all services on a host. Definition: Douglass Expires February 27, 2016 [Page 8] Internet-Draft Dav Server Information Object August 2015 5.4. service XML element Name: service Purpose: Contains information about a specific service on a host. Definition: 5.5. name XML element Name: name Purpose: Within a service or feature element provides the registered name of that service or feature. Definition: 5.6. href XML element Name: href Purpose: Contains location of a specific service. Definition: 5.7. features XML element Name: features Purpose: Contains information about all service features on a host. Definition: 6. WebDAV Features Here we define the feature elements for features defined in the various DAV related specifications. Douglass Expires February 27, 2016 [Page 9] Internet-Draft Dav Server Information Object August 2015 Specifications which extend this specification should define additions to this table. In addition, they may define the XML specification for that element. +------------+-----------------+-------------------------+ | Namespace | Name | Reference | +------------+-----------------+-------------------------+ | DAV | class-1 | [RFC4918]: section 18.1 | | DAV | class-2 | [RFC4918]: section 18.2 | | DAV | class-3 | [RFC4918]: section 18.3 | | DAV | access-control | [RFC3744]: section 7.2 | | DAV | version-control | [RFC3253]: section 3 | | DAV | extended-mkcol | [RFC5689]: section 3.1 | | DAV | quota | [RFC4331] | | DAV | bind | [RFC5842] | | DAV | search | [RFC5323] | | DAV | sync-collection | [RFC6578] | | DAV | add-member | [RFC5995] | +------------+-----------------+-------------------------+ 6.1. DAV class-1 feature XML element Namespace: DAV Name: class-1 DAV Header Name: 1 Reference: [RFC4918]: section 18.1 Description: Class 1 compliant resource Definition: 6.2. DAV class-2 feature XML element Namespace: DAV Name: class-2 DAV Header Name: 2 Reference: [RFC4918]: section 18.2 Description: Class 2 compliant resource Douglass Expires February 27, 2016 [Page 10] Internet-Draft Dav Server Information Object August 2015 Definition: 6.3. DAV class-3 feature XML element Namespace: DAV Name: class-3 DAV Header Name: 3 Reference: [RFC4918]: section 18.3 Description: Class 3 compliant resource Definition: 6.4. DAV access control feature XML element Namespace: DAV Name: access-control DAV Header Name: access-control Reference: [RFC3744]: section 7.2 Description: WebDAV ACL Definition: 6.5. DAV version control feature XML element Namespace: DAV Name: version-control DAV Header Name: version-control Reference: [RFC3253]: section 3 Description: WebDAV DeltaV Douglass Expires February 27, 2016 [Page 11] Internet-Draft Dav Server Information Object August 2015 Definition: 6.6. DAV Extended mkcol feature XML element Namespace: DAV Name: extended-mkcol DAV Header Name: extended-mkcol Reference: [RFC5689]: section 3.1 Description: Extended mkcol Definition: 6.7. DAV bind feature XML element Namespace: DAV Name: bind DAV Header Name: bind Reference: [RFC5842] Description: Binding extensions Definition: 6.8. DAV search feature XML element Namespace: DAV Name: search Reference: [RFC5323] Description: Search extensions Definition: Douglass Expires February 27, 2016 [Page 12] Internet-Draft Dav Server Information Object August 2015 6.9. DAV quota feature XML element Namespace: DAV Name: quota Reference: [RFC4331] Description: DAV quotas. May not apply to all resources. Absence of this feature implies no support on any resource. Definition: 6.10. DAV Sync Collection feature XML element Namespace: DAV Name: sync-collection Reference: [RFC6578] Description: Collection synchronization report. May not apply to all resources. Absence of this feature implies no support on any resource. Definition: 6.11. DAV Add Member feature XML element Namespace: DAV Name: add-member Reference: [RFC6578] Description: Using POST to add a member to a collection. May not apply to all resources. Absence of this feature implies no support on any resource. Definition: Douglass Expires February 27, 2016 [Page 13] Internet-Draft Dav Server Information Object August 2015 7. Examples 7.1. WebDAV server information TBD. 8. Notes Tag enabling synchronization Document location (section 3) server- info token in DAV header returned as part of OPTIONS response Clients that see that and do not have a server-info document for that service should do a propfind to discover document href. Authenticated v unauth Clients may fetch the si doc in an unauth mode. When they auth they must recheck their token and refetch if appropriate. Caching by intermediaries might be an issue Server info may vary by user-agent. 9. Security Considerations TBD. 10. IANA Considerations TBD. 11. Acknowledgments This specification is a result of discussions that took place within the Calendaring and Scheduling Consortium's CalDAV Technical Committee. The author thanks the participants of that group. 12. Normative References [ISO.8601.2004] International Organization for Standardization, "Data elements and interchange formats -- Information interchange -- Representation of dates and times", 2004. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2518] Goland, Y., Whitehead, E., Faizi, A., Carter, S., and D. Jensen, "HTTP Extensions for Distributed Authoring -- WEBDAV", RFC 2518, DOI 10.17487/RFC2518, February 1999, . Douglass Expires February 27, 2016 [Page 14] Internet-Draft Dav Server Information Object August 2015 [RFC3253] Clemm, G., Amsden, J., Ellison, T., Kaler, C., and J. Whitehead, "Versioning Extensions to WebDAV (Web Distributed Authoring and Versioning)", RFC 3253, DOI 10.17487/RFC3253, March 2002, . [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, . [RFC3744] Clemm, G., Reschke, J., Sedlar, E., and J. Whitehead, "Web Distributed Authoring and Versioning (WebDAV) Access Control Protocol", RFC 3744, DOI 10.17487/RFC3744, May 2004, . [RFC4331] Korver, B. and L. Dusseault, "Quota and Size Properties for Distributed Authoring and Versioning (DAV) Collections", RFC 4331, DOI 10.17487/RFC4331, February 2006, . [RFC4918] Dusseault, L., Ed., "HTTP Extensions for Web Distributed Authoring and Versioning (WebDAV)", RFC 4918, DOI 10.17487/RFC4918, June 2007, . [RFC5323] Reschke, J., Ed., Reddy, S., Davis, J., and A. Babich, "Web Distributed Authoring and Versioning (WebDAV) SEARCH", RFC 5323, DOI 10.17487/RFC5323, November 2008, . [RFC5689] Daboo, C., "Extended MKCOL for Web Distributed Authoring and Versioning (WebDAV)", RFC 5689, DOI 10.17487/RFC5689, September 2009, . [RFC5842] Clemm, G., Crawford, J., Reschke, J., Ed., and J. Whitehead, "Binding Extensions to Web Distributed Authoring and Versioning (WebDAV)", RFC 5842, DOI 10.17487/RFC5842, April 2010, . [RFC5995] Reschke, J., "Using POST to Add Members to Web Distributed Authoring and Versioning (WebDAV) Collections", RFC 5995, DOI 10.17487/RFC5995, September 2010, . Douglass Expires February 27, 2016 [Page 15] Internet-Draft Dav Server Information Object August 2015 [RFC6578] Daboo, C. and A. Quillaud, "Collection Synchronization for Web Distributed Authoring and Versioning (WebDAV)", RFC 6578, DOI 10.17487/RFC6578, March 2012, . Author's Address Michael Douglass Spherical Cow Group 226 3rd Street Troy, NY 12180 USA EMail: mdouglass@sphericalcowgroup.com URI: http://sphericalcowgroup.com Douglass Expires February 27, 2016 [Page 16]