--- 1/draft-ietf-netmod-yang-json-01.txt 2014-11-27 05:15:07.761571631 -0800 +++ 2/draft-ietf-netmod-yang-json-02.txt 2014-11-27 05:15:07.793572431 -0800 @@ -1,18 +1,18 @@ NETMOD Working Group L. Lhotka Internet-Draft CZ.NIC -Intended status: Standards Track October 13, 2014 -Expires: April 16, 2015 +Intended status: Standards Track November 27, 2014 +Expires: May 31, 2015 JSON Encoding of Data Modeled with YANG - draft-ietf-netmod-yang-json-01 + draft-ietf-netmod-yang-json-02 Abstract This document defines encoding rules for representing configuration, state data, RPC input and output parameters, and notifications defined using YANG as JavaScript Object Notation (JSON) text. Status of This Memo This Internet-Draft is submitted in full conformance with the @@ -21,21 +21,21 @@ 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 April 16, 2015. + This Internet-Draft will expire on May 31, 2015. Copyright Notice Copyright (c) 2014 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 @@ -51,42 +51,43 @@ 2. Terminology and Notation . . . . . . . . . . . . . . . . . . 3 3. Validation of JSON-encoded Instance Data . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Names and Namespaces . . . . . . . . . . . . . . . . . . . . 4 5. Encoding of YANG Data Node Instances . . . . . . . . . . . . 6 5.1. The "leaf" Data Node . . . . . . . . . . . . . . . . . . 6 5.2. The "container" Data Node . . . . . . . . . . . . . . . . 7 5.3. The "leaf-list" Data Node . . . . . . . . . . . . . . . . 7 5.4. The "list" Data Node . . . . . . . . . . . . . . . . . . 7 5.5. The "anyxml" Data Node . . . . . . . . . . . . . . . . . 8 - 6. The Mapping of YANG Datatypes to JSON Values . . . . . . . . 8 - 6.1. Numeric Datatypes . . . . . . . . . . . . . . . . . . . . 9 + 6. The Mapping of YANG Data Types to JSON Values . . . . . . . . 9 + 6.1. Numeric Types . . . . . . . . . . . . . . . . . . . . . . 9 6.2. The "string" Type . . . . . . . . . . . . . . . . . . . . 9 6.3. The "boolean" Type . . . . . . . . . . . . . . . . . . . 9 6.4. The "enumeration" Type . . . . . . . . . . . . . . . . . 9 6.5. The "bits" Type . . . . . . . . . . . . . . . . . . . . . 9 - 6.6. The "binary" Type . . . . . . . . . . . . . . . . . . . . 9 + 6.6. The "binary" Type . . . . . . . . . . . . . . . . . . . . 10 6.7. The "leafref" Type . . . . . . . . . . . . . . . . . . . 10 6.8. The "identityref" Type . . . . . . . . . . . . . . . . . 10 - 6.9. The "empty" Type . . . . . . . . . . . . . . . . . . . . 10 + 6.9. The "empty" Type . . . . . . . . . . . . . . . . . . . . 11 6.10. The "union" Type . . . . . . . . . . . . . . . . . . . . 11 - 6.11. The "instance-identifier" Type . . . . . . . . . . . . . 11 + 6.11. The "instance-identifier" Type . . . . . . . . . . . . . 12 7. I-JSON Compliance . . . . . . . . . . . . . . . . . . . . . . 12 8. Security Considerations . . . . . . . . . . . . . . . . . . . 13 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 - 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 - 10.1. Normative References . . . . . . . . . . . . . . . . . . 13 + 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 + 10.1. Normative References . . . . . . . . . . . . . . . . . . 14 10.2. Informative References . . . . . . . . . . . . . . . . . 14 - Appendix A. A Complete Example . . . . . . . . . . . . . . . . . 14 - Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 16 - B.1. Changes Between Revisions -00 and -01 . . . . . . . . . . 16 - Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 17 + Appendix A. A Complete Example . . . . . . . . . . . . . . . . . 15 + Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 17 + B.1. Changes Between Revisions -01 and -02 . . . . . . . . . . 17 + B.2. Changes Between Revisions -00 and -01 . . . . . . . . . . 17 + Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 18 1. Introduction The NETCONF protocol [RFC6241] uses XML [W3C.REC-xml-20081126] for encoding data in its Content Layer. Other management protocols might want to use other encodings while still benefiting from using YANG [RFC6020] as the data modeling language. For example, the RESTCONF protocol [I-D.ietf-netconf-restconf] supports two encodings: XML (media type "application/yang.data+xml") @@ -260,22 +261,22 @@ Character encoding MUST be UTF-8. Any data node instance is encoded as a name/value pair where the name is formed from the data node identifier using the rules of Section 4. The value depends on the category of the data node as explained in the following subsections. 5.1. The "leaf" Data Node A leaf instance is encoded as a name/value pair where the value can - be a string, number, literal 'true' or 'false' or the special array - '[null]', depending on the type of the leaf (see Section 6 for the + be a string, number, literal "true" or "false", or the special array + "[null]", depending on the type of the leaf (see Section 6 for the type encoding rules). Example: For the leaf node definition leaf foo { type uint8; } the following is a valid JSON-encoded instance: @@ -296,45 +297,53 @@ the following is a valid instance: "bar": { "foo": 123 } 5.3. The "leaf-list" Data Node A leaf-list is encoded as a name/array pair, and the array elements - are values whose type depends on the datatype of the leaf-list (see - Section 6). + are values of the same type, which can be a string, number, literal + "true" or "false", or the special array "[null]", depending on the + type of the leaf-list (see Section 6 for the type encoding rules). + + The order of array elements MUST be the same as the order of XML + elements representing leaf-list entries in the XML encoding. Example: For the leaf-list definition leaf-list foo { type uint8; } the following is a valid instance: "foo": [123, 0] 5.4. The "list" Data Node A list instance is encoded as a name/array pair, and the array elements are JSON objects. + The order of array elements MUST be the same as the order of XML + elements representing list entries in the XML encoding. + Unlike the XML encoding, where list keys are required to precede any other siblings, and to appear in the order specified by the data model, the order of members within a JSON-encoded list entry is arbitrary because JSON objects are fundamentally unordered collections of members. Example: For the list definition + list bar { key foo; leaf foo { type uint8; } leaf baz { type string; } } @@ -339,77 +348,78 @@ } the following is a valid instance: "bar": [ { "foo": 123, "baz": "zig" }, { - "baz": "zag", - "foo": 0 + "foo": 0, + "baz": "zag" } ] 5.5. The "anyxml" Data Node - An anyxml instance is translated to a name/value pair. The value can - be of any valid JSON type, i.e. an object, array, number, string or - any of the literals 'true', 'false' and 'null'. + An anyxml instance is encoded as a name/value pair. The value can be + of any valid JSON type, i.e. an object, array, number, string or one + of the literals "true", "false" and "null". This document defines no mapping between the contents of JSON- and - XML-encoded anyxml instances. It is not necessary because anyxml - contents are not subject to YANG-based validation (see sec. 7.10 in + XML-encoded anyxml instances. Note that the mapping is not needed + for the purposes of validation (Section 3) because anyxml contents + are not subject to YANG-based validation (see sec. 7.10 in [RFC6020]). Example: For the anyxml definition anyxml bar; the following is a valid instance: "bar": [true, null, true] -6. The Mapping of YANG Datatypes to JSON Values +6. The Mapping of YANG Data Types to JSON Values The type of the JSON value in an instance of the leaf or leaf-list - data node depends on the datatype of that data node as specified in - the following subsections. + data node depends on the type of that data node as specified in the + following subsections. -6.1. Numeric Datatypes +6.1. Numeric Types - A value of the "int8", "int16", "int32", "uint8", "uint16" is - represented as a JSON number. + A value of the "int8", "int16", "int32", "uint8", "uint16" and + "uint32" is represented as a JSON number. A value of the "int64", "uint64" or "decimal64" type is encoded as a JSON string whose contents is the lexical representation of that numeric value as specified in sections 9.2.1 and 9.3.1 of [RFC6020]. For example, if the type of the leaf "foo" in Section 5.1 was - "unit64" instead of "uint8", the instance would have to be encoded as + "uint64" instead of "uint8", the instance would have to be encoded as "foo": "123" The special handling of 64-bit numbers follows from I-JSON recommendation to encode numbers exceeding the IEEE 754-2000 double precision range as strings, see sec. 2.2 in [I-D.ietf-json-i-json]. 6.2. The "string" Type A "string" value encoded as a JSON string, subject to JSON encoding rules. 6.3. The "boolean" Type A "boolean" value is mapped to the corresponding JSON literal name - 'true' or 'false'. + "true" or "false". 6.4. The "enumeration" Type An "enumeration" value is mapped in the same way as a string except that the permitted values are defined by "enum" statements in YANG. See sec. 9.6 in [RFC6020]. 6.5. The "bits" Type A "bits" value is mapped to a JSON string identical to the lexical @@ -456,26 +466,26 @@ A valid instance of the "type" leaf is then encoded as follows: "type": "iana-if-type:ethernetCsmacd" The namespace identifier "iana-if-type" must be present in this case because the "ethernetCsmacd" identity is not defined in the same module as the "type" leaf. 6.9. The "empty" Type - An "empty" value is mapped to '[null]', i.e., an array with the - 'null' literal being its only element. + An "empty" value is mapped to "[null]", i.e., an array with the + "null" literal being its only element. - This encoding was chosen instead of using simply 'null' in order to + This encoding was chosen instead of using simply "null" in order to facilitate the use of empty leafs in common programming languages. - When used in a boolean context, the '[null]' value, unlike 'null', + When used in a boolean context, the "[null]" value, unlike "null", evaluates to true. Example: For the leaf definition leaf foo { type empty; } a valid instance is @@ -511,39 +521,50 @@ "bar": 13.5 In this case, the JSON encoding indicates the value is supposed to be a number rather than string. 6.11. The "instance-identifier" Type An "instance-identifier" value is encoded as a string that is analogical to the lexical representation in XML encoding, see - sec. 9.13.3 in [RFC6020]. The only difference is that XML namespace - prefixes used for qualifying node names in the instance-identifier - value are replaced by the corresponding module names according to the - rules of Section 4. + sec. 9.13.3 in [RFC6020]. However, the encoding of namespaces in + instance-identifier values follows the rules stated in Section 4, + namely: - Conversely, when translating such a value from JSON to XML, the - namespace identifier (YANG module name) in each component of the - instance-identifier MUST be replaced by the XML namespace prefix that - is associated with the namespace URI reference of the module. + o The namespace identifier is the module name where each data node + is defined. - For example, assume "ex" is the prefix associated with the namespace - URI that is defined in the "example" module. Then the XML-encoded - instance-identifier + o The encoding of a node name with an explicit namespace is as shown + in Figure 1. - /ex:system/ex:user[ex:name='fred'] + o The leftmost (top-level) node name is always prefixed with the + namespace identifier. - corresponds to the following JSON-encoded instance-identifier: + o Any subsequent node name has the namespace identifier if and only + if its parent node has a different namespace. This also holds for + node names appearing in predicates. - /example:system/example:user[example:name='fred'] + For example, + + /ietf-interfaces:interfaces/interface[name='eth0']/ietf-ip:ipv4/ip + + is a valid instance-identifer value because the data nodes + "interfaces", "interface" and "name" are defined in the module "ietf- + interfaces", whereas "ipv4" and "ip" are defined in "ietf-ip". + + When translating an instance-identifier value from JSON to XML, the + namespace identifier (YANG module name) in each component of the + instance-identifier MUST be replaced by an XML namespace prefix that + is associated with the namespace URI reference of the module in the + scope of the element containing the instance-identifier value. 7. I-JSON Compliance I-JSON [I-D.ietf-json-i-json] is a restricted profile of JSON that guarantees maximum interoperability for protocols that use JSON in their messages, no matter what JSON encoders/decoders are used in protocol implementations. The encoding defined in this document therefore observes the I-JSON requirements and recommendations as closely as possible. @@ -558,48 +579,50 @@ o Numbers of any type supported by YANG can be exchanged reliably. See Section 6.1 for details. The only two cases where a JSON instance document encoded according to this document may deviate from I-JSON were dictated by the need to be able to encode the same instance data in both JSON and XML. These two exceptions are: o Leaf values encoded as strings may contain code points identifying Noncharacters that belong to the XML character set (see sec. 2.2 - in [W3C.REC-xml-20081126]). + in [W3C.REC-xml-20081126]). This issue is likely to be solved in + YANG 1.1 because noncharacters will not be allowed in string + values, see sec. 9.4 in [I-D.ietf-netmod-rfc6020bis]. o Values of the "binary" type are encoded with the base64 encoding - scheme (see sec. 9.8.2 in [RFC6020]) whereas I-JSON recommends - base64url instead. However, the use of base64 should not cause - any interoperability problems because these values never appear in - an URL. + scheme (Section 6.6), whereas I-JSON recommends base64url instead. + Theoretically, values of the "binary" type might appear in URI + references, such as Request-URI in RESTCONF, although in practice + the cases where it is really needed should be extremely rare. 8. Security Considerations This document defines an alternative encoding for data modeled in the YANG data modeling language. As such, it doesn't contribute any new security issues beyond those discussed in sec. 15 of [RFC6020]. JSON is rather different from XML, and JSON parsers may thus suffer from other types of vulnerabilities than their XML counterparts. To minimize these security risks, it is important that client and server software supporting JSON encoding behaves as required in sec. 3 of [I-D.ietf-json-i-json]. That is, any received JSON data that violate any of I-JSON strict constraints MUST NOT be trusted nor acted upon. Violations due to the presence of Unicode Noncharacters in the data - exceptions (see Section 7) SHOULD be carefully examined. + (see Section 7) SHOULD be carefully examined. 9. Acknowledgments - The author wishes to thank Andy Bierman, Martin Bjorklund, Juergen - Schoenwaelder and Phil Shafer for their helpful comments and - suggestions. + The author wishes to thank Andy Bierman, Martin Bjorklund, Balazs + Lengyel, Juergen Schoenwaelder and Phil Shafer for their helpful + comments and suggestions. 10. References 10.1. Normative References [I-D.ietf-json-i-json] Bray, T., "The I-JSON Message Format", draft-ietf-json- i-json-03 (work in progress), August 2014. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate @@ -620,23 +643,28 @@ Bray, T., Paoli, J., Sperberg-McQueen, M., Maler, E., and F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fifth Edition)", World Wide Web Consortium Recommendation REC- xml-20081126, November 2008, . 10.2. Informative References [I-D.ietf-netconf-restconf] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF - Protocol", draft-ietf-netconf-restconf-02 (work in + Protocol", draft-ietf-netconf-restconf-03 (work in progress), October 2014. + [I-D.ietf-netmod-rfc6020bis] + Bjorklund, M., "YANG - A Data Modeling Language for the + Network Configuration Protocol (NETCONF)", draft-ietf- + netmod-rfc6020bis-02 (work in progress), November 2014. + [RFC7223] Bjorklund, M., "A YANG Data Model for Interface Management", RFC 7223, May 2014. [W3C.REC-xpath-19991116] Clark, J. and S. DeRose, "XML Path Language (XPath) Version 1.0", World Wide Web Consortium Recommendation REC-xpath-19991116, November 1999, . Appendix A. A Complete Example @@ -738,21 +766,28 @@ } } ] } } Appendix B. Change Log RFC Editor: Remove this section upon publication as an RFC. -B.1. Changes Between Revisions -00 and -01 +B.1. Changes Between Revisions -01 and -02 + + o Encoding of namespaces in instance-identifiers was changed. + + o Text specifying the order of array elements in leaf-list and list + instances was added. + +B.2. Changes Between Revisions -00 and -01 o Metadata encoding was moved to a separate I-D, draft-lhotka- netmod-yang-metadata. o JSON encoding is now defined directly rather than via XML-JSON mapping. o The rules for namespace encoding has changed. This affect both node instance names and instance-identifiers.