NETCONF A. Bierman Internet-Draft netconfcentral.org Intended status: Standards Track B. Lengyel Expires: February 28, 2009 Ericsson August 27, 2008 With-defaults capability for NETCONF draft-bierman-netconf-with-defaults-00 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 February 28, 2009. Copyright Notice Copyright (C) The IETF Trust (2008). Abstract The NETCONF protocol defines ways to read configuration data from a NETCONF agent. Part of this data is not set by the NETCONF manager, but rather set to a default value by the NETCONF agent. In many situations the NETCONF manager has a priori knowledge about this data, so the NETCONF agent does not need to send it to the manager. In other situations the NETCONF manger will need this data as part of the NETCONF rpc reply messages. This document defines a capability- Bierman & Lengyel Expires February 28, 2009 [Page 1] Internet-Draft with-defaults August 2008 based extension to the NETCONF protocol that allows the NETCONF manager to control whether default values are part of NETCONF rpc reply messages. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1.1. Requirements Notation . . . . . . . . . . . . . . . . 3 1.1.2. NETCONF Terms . . . . . . . . . . . . . . . . . . . . 3 2. With-defaults Capability . . . . . . . . . . . . . . . . . . . 4 2.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1.1. Basic handling of default data . . . . . . . . . . . . 4 2.2. Dependencies . . . . . . . . . . . . . . . . . . . . . . . 5 2.3. Capability Identifier . . . . . . . . . . . . . . . . . . 5 2.4. New Operations . . . . . . . . . . . . . . . . . . . . . . 5 2.5. Modifications to Existing Operations . . . . . . . . . . . 5 3. Interactions with Other Capabilities . . . . . . . . . . . . . 7 4. Data Model XSD . . . . . . . . . . . . . . . . . . . . . . . . 7 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 7. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 10 7.1. Augmenting the base RPCs . . . . . . . . . . . . . . . . . 10 7.2. Third option: Trim . . . . . . . . . . . . . . . . . . . . 10 7.3. List affected operations or generalize . . . . . . . . . . 10 8. Normative References . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12 Intellectual Property and Copyright Statements . . . . . . . . . . 13 Bierman & Lengyel Expires February 28, 2009 [Page 2] Internet-Draft with-defaults August 2008 1. Introduction The NETCONF protocol defines ways to read configuration data from a NETCONF agent. Part of this data is not set by the NETCONF manager, but rather set to a default value by the NETCONF agent. In many situations the NETCONF manager has a priori knowledge about this data, so the NETCONF agent does not need to send it to the manager. A priori knowledge can be e.g. a document formally describing the data models supported by the NETCONF agent. It is quite common for networking devices to suppress the output of parameters set to the default value. This is done to save CPU time and non-volatile memory. In addition, there are likely to be a large number of such parameters. Is is often not useful for network operators to view all these default values. It is usually more interesting to view just the parameters which have been explicitly set by the network operator. However there are perfectly valid use-cases when a NETCONF manager will need the default data from the node. Documentation about default values is often unreliable or unavailable. Some management applications might not have the capabilities to correctly parse and interpret formal data models. Human users might want to understand the received data without extensive consultation of the documentation. In all theses cases the NETCONF manager will need default data as part of the NETCONF rpc reply messages. This document defines a capability-based extension to the NETCONF protocol that allows the NETCONF manager to control whether default data is part of NETCONF rpc reply 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]. 1.1.2. NETCONF Terms o Default data: Data that is set by the NETCONF agent whenever the NETCONF manager does not provide a specific value for the relevant data item. In the context of this document only configuration data is considered, state data is excluded. o Explicitly set default data: Data that is explicitly set by the NETCONF manager to it's default value. Some agents MIGHT treat explicitly set default data as default data, as they might not be Bierman & Lengyel Expires February 28, 2009 [Page 3] Internet-Draft with-defaults August 2008 able to differentiate between them. In addition the following terms are defined in RFC 4741 and are not redefined here: o agent o application o manager o operation o RPC o RPC request o RPC response 2. With-defaults Capability 2.1. Overview The :with-defaults capability indicates that the NETCONF agent makes it possible for the NETCONF manager to control whether default data is part of NETCONF rpc reply messages. The capability only effects configuration data not state data. Sending of default data is controlled for each individual operation separately. The NETCONF agent MUST also indicate it's default behavior, whether it sends default data in the absence of any specific request from the NETCONF manager. This capability effects the , and operations. Other operations that might return configuration data are not effected unless this is specified in the document defining the respective operation. TODO: what about model defined RPCs? Will they be effected? How can it be stated in YANG whether yes or no? 2.1.1. Basic handling of default data It is not defined in [RFC4741] whether default data is part of the datastore/data model, or if it meta data that influences the behavior of the NETCONF server device but is not actually part of the datastore. This document intentionally avoids deciding this question. The described functionality should work in both cases. As a consequence of this issue basic NETCONF servers that do not implement the :with-defaults capability may or may not return default data in NETCONF rpc reply messages. Bierman & Lengyel Expires February 28, 2009 [Page 4] Internet-Draft with-defaults August 2008 2.2. Dependencies None 2.3. Capability Identifier urn:ietf:params:netconf:capability:with-defaults The identifier MUST have an additional parameter indicating the default value of with-defaults for the NETCONF agent. The allowed values of with-defaults attribute can be used as a default value see Section 2.5. urn:ietf:params:netconf:capability:with-defaults?default=false The identifier MAY have a second parameter indicating how it treats explicitly set default data. If the explicit-default parameter is set to "unrecognized" the agent MUST treat explicitly set default data as normal default data. If the parameter is set to recognized this means that such data is not treated as default data. All other values for the parameter or a missing parameter is handled as the value unrecognized. urn:ietf:params:netconf:capability:with-defaults?default=false& explicit-default=recognized 2.4. New Operations None 2.5. Modifications to Existing Operations A new 'with-defaults' XML attribute is used to control the generation of default data. If the 'with-defaults' attribute is present in the element, of the affected operations, the agent will use it's value to control whether default data is returned in the NETCONF rpc reply messages. Allowed values of the with-defaults attribute are: o true: indicates that all default data MUST be returned. o false: indicates that default data MUST NOT be returned. The 'with-defaults' attribute is defined in the namespace specified as the 'targetNamespace' in Section 4. However, an agent should accept it even if no namespace is used. If the 'with-defaults' attribute is not present it's default value as specified in the capability string Section 2.3 will be used. Bierman & Lengyel Expires February 28, 2009 [Page 5] Internet-Draft with-defaults August 2008 Affected operations: o o o Index clause components are not subject to default suppression. If an element within the configuration database is considered to be part of a key, and represents one of the naming components for a conceptual data structure which allows multiple named instances of an ancestor node, then this element is never suppressed, regardless of the value of the 'with-defaults' attribute. The following example shows a operation which is using the 'with-defaults' attribute. The manager is retrieving the 'interfaces' object, defined in the example.com Interfaces 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 MTU value of '1500' is not returned for the interface named 'Eth1' because it is set to the default value, and the 'with-defaults' attribute is set to 'false'. Bierman & Lengyel Expires February 28, 2009 [Page 6] Internet-Draft with-defaults August 2008 Eth0 8192 Eth1 loopback 8192 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 attribute.. Bierman & Lengyel Expires February 28, 2009 [Page 7] Internet-Draft with-defaults August 2008 BEGIN Schema defining the partial-lock and unlock operations. organization "IETF NETCONF Working Group" Version: 1.0 Contact Info: ietf@andybierman.com balazs.lengyel@ericsson.com END Figure 2 5. IANA Considerations This document registers two URIs for the NETCONF XML namespace in the IETF XML registry [RFC3688]. Note that the capability URN is compliant to [RFC4741] section 10.3. +---------------+---------------------------------------------------+ | Index | Capability Identifier | +---------------+---------------------------------------------------+ | :with-default | urn:ietf:params:netconf:capability:with-defaults: | | s | 1.0 | +---------------+---------------------------------------------------+ URI: urn:ietf:params:xml:ns:netconf:with-defaults:1.0 Registrant Contact: The IESG. XML: N/A, the requested URI is an XML namespace. Bierman & Lengyel Expires February 28, 2009 [Page 8] Internet-Draft with-defaults August 2008 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 manager 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. Bierman & Lengyel Expires February 28, 2009 [Page 9] Internet-Draft with-defaults August 2008 7. Open Issues 7.1. Augmenting the base RPCs Instead of using an attribute on the RPC element we could "augment" the relevant NETCONF operations with an extra XML element with a similar meaning. Pro: parameters on RPC are for vendor extensions. We should not put standard stuff there. Contra: Some people might consider this a violation of [RFC4741] as the XSD does not allow adding new elements. As there is no NETCONF YAM (at least not yet), what do we actually augment? Also there are multiple ways of defining RFC4741 in YANG. The description will be perfectly clear, but it can never be fed into YANG tools. Conclusion: While augmenting has a certain elegance, we should stick to the attribute based solution. 7.2. Third option: Trim This is another can o' worms. I preserve user specified values even when the value matches the default. This allows users complete control over what appears in their config. Values to not disappear simply because the match the default. If you want this behavior, I'd suggest making your "with-defaults" a tri-state value: "all" -- report all default values "trim" -- do not report values if they match the default "explicit" -- report any values explicitly set Do we need the trim option ? 7.3. List affected operations or generalize Should we list affected operations , , or should we just say "any of the protocol operations which return the contents of a configuration database", or should we do both? Bierman & Lengyel Expires February 28, 2009 [Page 10] Internet-Draft with-defaults August 2008 8. 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, . [RFC4741] 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. Bierman & Lengyel Expires February 28, 2009 [Page 11] Internet-Draft with-defaults August 2008 Authors' Addresses Andy Bierman netconfcentral.org Simi Valley, CA USA Email: ietf@andybierman.com Balazs Lengyel Ericsson Hungary Email: balazs.lengyel@ericsson.com Bierman & Lengyel Expires February 28, 2009 [Page 12] Internet-Draft with-defaults August 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). 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). Bierman & Lengyel Expires February 28, 2009 [Page 13]