NETCONF A. Bierman Internet-Draft Netconf Central Intended status: Standards Track B. Lengyel Expires: February 6, 2010 Ericsson August 05, 2009 With-defaults capability for NETCONF draft-ietf-netconf-with-defaults-03 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and 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 February 6, 2010. Copyright Notice Copyright (c) 2009 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 in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract The NETCONF protocol defines ways to read configuration data from a NETCONF server. Part of this data is not set by the NETCONF client, Bierman & Lengyel Expires February 6, 2010 [Page 1] Internet-Draft with-defaults August 2009 but rather a default value is used. In many situations the NETCONF client has a priori knowledge about default data, so the NETCONF server does not need to send it to the client. In other situations the NETCONF manger will need this data as part of the NETCONF messages. This document defines a capability-based extension to the NETCONF protocol that allows the NETCONF client to control whether default values are part of NETCONF messages. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1.1. Requirements Notation . . . . . . . . . . . . . . . . 3 1.1.2. NETCONF Terms . . . . . . . . . . . . . . . . . . . . 4 1.2. Current handling of default data . . . . . . . . . . . . . 4 2. With-defaults Capability . . . . . . . . . . . . . . . . . . . 4 2.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2. Dependencies . . . . . . . . . . . . . . . . . . . . . . . 5 2.3. Capability Identifier . . . . . . . . . . . . . . . . . . 5 2.4. New Operations . . . . . . . . . . . . . . . . . . . . . . 5 2.5. Modifications to Existing Operations . . . . . . . . . . . 6 3. Interactions with Other Capabilities . . . . . . . . . . . . . 7 4. Data Model XSD . . . . . . . . . . . . . . . . . . . . . . . . 7 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 7. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 9 7.1. Other default handling modes in the real world? . . . . . 9 8. Appendix A - YANG Module for with-defaults (non-normative) . 9 9. Appendix B - Change Log . . . . . . . . . . . . . . . . . . 12 9.1. 02-03 . . . . . . . . . . . . . . . . . . . . . . . . . . 12 9.2. 01-02 . . . . . . . . . . . . . . . . . . . . . . . . . . 12 9.3. 00-01 . . . . . . . . . . . . . . . . . . . . . . . . . . 12 9.4. -00 . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 11.1. Normative References . . . . . . . . . . . . . . . . . . . 13 11.2. Informative References . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 Bierman & Lengyel Expires February 6, 2010 [Page 2] Internet-Draft with-defaults August 2009 1. Introduction The NETCONF protocol defines ways to read configuration data from a NETCONF server. Part of this data is not set by the NETCONF client, but rather a default value is used. In many situations the NETCONF client has a priori knowledge about default data, so the NETCONF server does not need to send it to the client. A priori knowledge can be e.g., a document formally describing the data models supported by the NETCONF server. A networking device may have a large number of default values. Often the default values are not interesting or specifically defined with a "reasonable" value, so that the management user does not have to handle them. For these reasons it is quite common for networking devices to suppress the output of parameters having the default value. However there are use-cases when a NETCONF client will need the default data from the node: o The management application often needs a single, definitive and complete set of configuration values that determine how the a networking device works. o Documentation about default values can be unreliable or unavailable. o Some management applications might not have the capabilities to correctly parse and interpret formal data models. o Human users might want to understand the received data without consultation of the documentation. In all theses cases the NETCONF client will need default data as part of the NETCONF messages. This document defines a capability-based extension to the NETCONF protocol that allows the NETCONF client to control whether default data is part of NETCONF messages. 1.1. Terminology 1.1.1. Requirements Notation 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]. Bierman & Lengyel Expires February 6, 2010 [Page 3] Internet-Draft with-defaults August 2009 1.1.2. NETCONF Terms o Default data: Data that is set or used by the NETCONF server whenever the NETCONF client does not provide a specific value for the relevant data item. Default values SHOULD be specified in documents describing the data models supported by the NETCONF server. o Explicitly set default data: Data that is explicitly set by the NETCONF client to its default value. Some servers MAY treat explicitly set default data as simple default data, as they may not be able to differentiate between them. In addition the following terms are defined in RFC 4741 and are not redefined here: o application o client o operation o RPC o RPC request o RPC response o server 1.2. Current handling of default data [NETCONF] does not define whether default data is part of the datastore/data model, or if it is meta-data that influences the behavior of the NETCONF server, but is not actually part of the datastore. This document is intended to support either type of implementation, without deciding which approach is better. As a consequence of this issue, NETCONF servers that do not implement the :with-defaults capability may or may not return default data in NETCONF messages. Different NETCONF servers report default data in different ways. This document specifies the following three basic modes: o report-all: All default data is always reported. o trim: Values are not reported if they match the default. o explicit: Report values if they are explicitly set. For state data this has the same effect as report-all 2. With-defaults Capability Bierman & Lengyel Expires February 6, 2010 [Page 4] Internet-Draft with-defaults August 2009 2.1. Overview The :with-defaults capability indicates that the NETCONF server makes it possible for the NETCONF client to control whether default data is part of NETCONF messages. The capability affects both configuration and state data (while acknowledging that the usage of default values for state data is less prevalent). Sending of default data is controlled for each individual operation separately. A NETCONF servers implementing the :with-defaults capability MUST indicate its basic behavior, whether it sends default data in the absence of any specific request from the NETCONF client; and MUST support the 'report-all' handling mode and MAY support other modes. 2.2. Dependencies None 2.3. Capability Identifier urn:ietf:params:netconf:capability:with-defaults:1.0 The identifier MUST have a parameter: "basic". This indicates how the server reports default data in messages, in the case the client does not specify the required behavior in the request. The allowed values of this parameter are report-all, trim, explicit as listed in Section 1.2. The identifier MAY have another parameter: "also-supported". This indicates what other default handling modes does the server support. The value of the parameter is a comma separated list of one or two modes that are supported beside the mode indicated in the basic parameter Possible modes are taken from the list in Section 1.2. Example: urn:ietf:params:netconf:capability:with-defaults:1.0?basic=report-all urn:ietf:params:netconf:capability:with-defaults:1.0?basic=report- all&also-supported=trim,explicit 2.4. New Operations None Bierman & Lengyel Expires February 6, 2010 [Page 5] Internet-Draft with-defaults August 2009 2.5. Modifications to Existing Operations A new XML child element is added to the method-name element. This is the element that indicates the type of the operation e.g. , or . If the element is present, it controls the reporting of default data. The server MUST return default data in the NETCONF messages according to the value of the element. Allowed values of the with-defaults element are taken from the list in Section 1.2. The allowed values are restricted to the values that the device indicates support for in the with-defaults capability in the basic and also-supported parameters. If the element is not present, the server follows its basic behavior as indicated by the capability identifier's parameter see Section 2.3. Affected operations: o o o is only affected if the target of the operation is a URL. If the target is a NETCONF datastore (running, candidate or startup) the capability has no effect. Other operations that return configuration data SHOULD also handle default data according to the rules set in this document, and explicitly state this in their documentation. If this is not specified in the document defining the respective operation, the default handling rules described herein do not affect these operations. The following example shows a operation which is using the 'with-defaults' element. The client is retrieving the 'interfaces' object, defined in the example.com data model. (In this simple example, the 'name' field is defined as the key, and the 'mtu' field is the only other data in the element). The default value of mtu is '1500'. The basic default handling for the server is "trim". As the 'with-defaults' element has the value 'report-all', the mtu is returned not just for eth0 but also for eth1. Bierman & Lengyel Expires February 6, 2010 [Page 6] Internet-Draft with-defaults August 2009 report-all eth0 8192 eth1 1500 Figure 1 3. Interactions with Other Capabilities None 4. Data Model XSD This section contains an XML Schema Definition [W3C.REC-xmlschema-2-20041028] which defines the XML syntax associated for the with-defaults XML element. Bierman & Lengyel Expires February 6, 2010 [Page 7] Internet-Draft with-defaults August 2009 Schema defining the with-defaults element. Organization: "IETF NETCONF Working Group" Contact Info: balazs.lengyel@ericsson.com 5. IANA Considerations This document registers one capability identifier URN from the "Network Configuration Protocol (NETCONF) Capability URNs" registry, and registers the same URN for the NETCONF XML namespace in the "IETF XML registry" [RFC3688]. Note that the capability URN is compliant to [NETCONF] section 10.3. +---------------+---------------------------------------------------+ | Index | Capability Identifier | +---------------+---------------------------------------------------+ | :with-default | urn:ietf:params:netconf:capability:with-defaults: | | s | 1.0 | +---------------+---------------------------------------------------+ Bierman & Lengyel Expires February 6, 2010 [Page 8] Internet-Draft with-defaults August 2009 6. Security Considerations This document defines a minor extension to existing NETCONF protocol operations. it does not introduce any new or increased security risks into the management system. The 'with-defaults' capability provides client controls over the retrieval of particular types of XML data from a configuration database. They only suppress data that can already be retrieved with the standard protocol operations, and do not add any data to the configuration database. 7. Open Issues 7.1. Other default handling modes in the real world? Are there any other basic default handling modes out there we need to include? 8. Appendix A - YANG Module for with-defaults (non-normative) The following YANG module defines the addition of the with-defaults element to the , and operations. The YANG language is defined in [I-D.ietf-netmod-yang]. The above operations are defined in YANG in [I-D.ietf-netconf-4741bis]. module ietf-netconf-with-defaults { namespace "urn:ietf:params:netconf:capability:with-defaults:1.0"; prefix nwd; // for the uri data type import ietf-netconf { prefix nc; } description "This module defines a capability-based extension to the NETCONF protocol that allows the NETCONF client to control whether default values are part of NETCONF messages. Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the Bierman & Lengyel Expires February 6, 2010 [Page 9] Internet-Draft with-defaults August 2009 following conditions are met: - Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. - Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. - Neither the name of Internet Society, IETF or IETF Trust, nor the names of specific contributors, may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 'AS IS' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. This version of this YANG module is part of RFC XXXX; see the RFC itself for full legal notices."; // RFC Ed.: replace XXXX with actual RFC number and remove this note reference "RFC XXXX"; // RFC Ed.: replace XXXX with actual RFC number and remove this note // reference "draft-ietf-netconf-with-defaults-03.txt"; // RFC Ed.: remove the reference statement above and this note. contact "Send comments to the NETCONF WG mailing list. "; Bierman & Lengyel Expires February 6, 2010 [Page 10] Internet-Draft with-defaults August 2009 revision 2009-07-01 { description "Initial version"; } // with-defaults capability defined as a feature feature with-defaults { description "NETCONF :with-defaults capability; If the agent advertises the :with-defaults capability for a session, then this feature MUST also be enabled for that session. Otherwise, this feature MUST NOT be enabled."; // RFC Ed.: replace XXXX with actual RFC number and // remove this note reference "RFC XXXX"; } typedef with-defaults-mode-type { description "Possible modes to report default data in rpc-reply messages."; type enumeration { enum report-all { description "All default data is always reported."; } enum trim { description "Values are not reported if they match the default."; } enum explicit { description "Report values if they are explicitly set. For state data this has the same effect as report-all"; } } } // extending the get-config operation augment /nc:get-config/nc:input { leaf with-defaults { type with-defaults-mode-type; } } // extending the get operation Bierman & Lengyel Expires February 6, 2010 [Page 11] Internet-Draft with-defaults August 2009 augment /nc:get/nc:input { leaf with-defaults { type with-defaults-mode-type; } } // extending the copy-congig operation augment /nc:copy-config/nc:input { leaf with-defaults { type with-defaults-mode-type; } } } 9. Appendix B - Change Log 9.1. 02-03 Clarifications YAM added Use the same URN for the capability and the XML namespace to accommodate YANG, and avoid two separate URN/URIs being advertised in the HELLO message, for such a small function. 9.2. 01-02 report-all made mandatory Placeholder for YAM added, XSD will be removed when 4741 provides the NETCONF YAM with-defaults is valid for state data as well (if state data has a defined default which might not be so frequent). The definition of explicit was modified for state data. 9.3. 00-01 Changed value set of with-default capability and element Added version to URI Bierman & Lengyel Expires February 6, 2010 [Page 12] Internet-Draft with-defaults August 2009 9.4. -00 Created from draft-bierman-netconf-with-defaults-01.txt It was decided by the NETCONF mailing list, that with-defaults should be a sub-element of each affected operation. While this violates the XSD of RFC4741 this is acceptable and follows the ideas behind NETCONF and YANG. Hopefully it will be clarified in the 4741bis RFC whether such extensions are allowed. 10. Acknowledgements Thanks to Martin Bjorklund, Sharon Chisholm, Phil Shafer, Juergen Schoenwaelder, Washam Fan and many other members of the NETCONF WG for providing important input to this document. 11. References 11.1. Normative References [W3C.REC-xmlschema-2-20041028] Biron, P. and A. Malhotra, "XML Schema Part 2: Datatypes Second Edition", World Wide Web Consortium Recommendation REC-xmlschema-2-20041028, October 2004, . [NETCONF] Enns, R., "NETCONF Configuration Protocol", RFC 4741, December 2006. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, January 2004. 11.2. Informative References [I-D.ietf-netmod-yang] Bjorklund, M., "YANG - A data modeling language for NETCONF", draft-ietf-netmod-yang-07 (work in progress), July 2009. [I-D.ietf-netconf-4741bis] Enns, R., Bjorklund, M., Schoenwaelder, J., and A. Bierman & Lengyel Expires February 6, 2010 [Page 13] Internet-Draft with-defaults August 2009 Bierman, "NETCONF Configuration Protocol", draft-ietf-netconf-4741bis-01 (work in progress), July 2009. Authors' Addresses Andy Bierman Netconf Central Simi Valley, CA USA Email: andy@netconfcentral.com Balazs Lengyel Ericsson Budapest, Hungary Email: balazs.lengyel@ericsson.com Bierman & Lengyel Expires February 6, 2010 [Page 14]