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core                                                     P. van der Stok
Internet-Draft                                                consultant
Intended status: Informational                           B. Greevenbosch
Expires: April 20, 2014                              Huawei Technologies
                                                        October 17, 2013


                       CoAp Management Interfaces
                     draft-vanderstok-core-comi-01

Abstract

   The draft describes an interface based on CoAP to manage constrained
   devices via MIBs.  The proposed integration of CoAP with SNMP reduces
   the code- and application development complexity by accessing MIBs
   via a standard CoAP server.  The payload of the MIB request is JSON,
   CBOR or XML (EXI).  The mapping from SMI to XML, JSON and CBOR is
   specified.

Note

   Discussion and suggestions for improvement are requested, and should
   be sent to core@ietf.org.

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 April 20, 2014.

Copyright Notice

   Copyright (c) 2013 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



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   (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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  CoAP Interface  . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  MIB Function Set  . . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  SNMP/MIB architecture . . . . . . . . . . . . . . . . . .   6
       3.1.1.  SNMP functions  . . . . . . . . . . . . . . . . . . .   6
       3.1.2.  MIB structure . . . . . . . . . . . . . . . . . . . .   7
     3.2.  CoMI Function Set . . . . . . . . . . . . . . . . . . . .   8
       3.2.1.  Single MIB values . . . . . . . . . . . . . . . . . .   8
       3.2.2.  multi MIB values  . . . . . . . . . . . . . . . . . .  10
       3.2.3.  Table row . . . . . . . . . . . . . . . . . . . . . .  10
       3.2.4.  Error returns . . . . . . . . . . . . . . . . . . . .  11
   4.  Mapping SMI to CoMI payload . . . . . . . . . . . . . . . . .  11
     4.1.  Mapping SMI to JSON . . . . . . . . . . . . . . . . . . .  11
       4.1.1.  Tables in JSON  . . . . . . . . . . . . . . . . . . .  13
     4.2.  Mapping SMI to CBOR . . . . . . . . . . . . . . . . . . .  14
       4.2.1.  Tables in CBOR  . . . . . . . . . . . . . . . . . . .  15
     4.3.  Mapping SMI to XML  . . . . . . . . . . . . . . . . . . .  19
       4.3.1.  Tables in XML . . . . . . . . . . . . . . . . . . . .  20
   5.  MIB discovery . . . . . . . . . . . . . . . . . . . . . . . .  21
   6.  Trap functions  . . . . . . . . . . . . . . . . . . . . . . .  22
   7.  MIB access management . . . . . . . . . . . . . . . . . . . .  22
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  23
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  23
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  23
   11. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . .  23
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  24
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  24
     12.2.  Informative References . . . . . . . . . . . . . . . . .  24
   Appendix A.  XML Schema for MIB . . . . . . . . . . . . . . . . .  27
   Appendix B.  XML Schema for CoMI support  . . . . . . . . . . . .  29
     B.1.  Schema for CoAP binding . . . . . . . . . . . . . . . . .  29
     B.2.  Valid Schemas . . . . . . . . . . . . . . . . . . . . . .  30
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  30

1.  Introduction





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   The Constrained RESTful Environments (CoRE) working group aims at
   Machine to Machine (M2M) applications such as smart energy and
   building control.

   Small M2M devices need to be managed in an automatic fashion to
   handle the large quantities of devices that are expected to be
   installed in future installations.  The management protocol of choice
   for Internet is SNMP [RFC3410] as is testified by the large number of
   Management Information Base (MIB) [RFC3418]  specifications currently
   published [STD0001].  More recently, the NETCONF protocol [RFC6241]
   was developed with an extended set of messages using XML [XML] as
   data format.  The data syntax is specified with YANG [RFC6020] and a
   mapping from Yang to XML is specified.  In [RFC6643]  SMIv2 syntax is
   expressed in Yang.  Contrary to SNMP and also CoAP, NETCONF assumes
   persistent connections for example provided by SSH.  The NETCONF
   protocol provides operations to retrieve, configure, copy, and delete
   configuration data-stores.  Configuring data-stores distinguishes
   NETCONF from SNMP which operates on standardized MIBs.

   The CoRE Management Interface (CoMI) is intended to work on
   standardized data-sets in a stateless client-server fashion and is
   thus closer to SNMP than to NETCONF.  Standardized data sets are
   necessary when small devices from different manufacturers are managed
   by applications originating from another set of manufacturers.
   Stateless communication is encouraged to keep communications simple
   and the amount of state information small in line with the design
   objectives of 6lowpan [RFC4944] [RFC6775], RPL [RFC6650], and CoAP
   [I-D.ietf-core-coap].

   Currently, managed devices need to support two protocols: CoAP and
   SNMP.  When the MIB can be accessed with the CoAP protocol, the SNMP
   protocol can be replaced with the CoAP protocol.  This arrangement
   reduces the code complexity of the stack in the constrained device,
   and harmonizes applications development.

   The objective of CoMI is to provide a CoAP based Function Set that
   reads and sets values of MIB variables in devices to (1) initialize
   parameter values at start-up, (2) acquire statistics during
   operation, and (3) maintain nodes by adjusting parameter values
   during operation.

   The payload of CoMI is encoded in JSON [JSON], CBOR
   [I-D.bormann-cbor] or XML [XML].  CoMI is intended for small devices.
   The XML or JSON overhead can be prohibitive.  It is therefore
   recommended to transport CBOR or EXI [EXI] in the payload.  CBOR,
   like BER used for SNMP, transports the data type in the payload.  EXI
   uses a schema file that provides information about transported data
   types.



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   In [EXI-measurement] it is shown that EXI can be an order of
   magnitude smaller than the equivalent XML representation.  Actually,
   the EXI structure adds the overhead per data unit of an EXI event
   (indicates the type of the following XML element) with a size that
   depends on the number of EXI event types present in the schema and
   its frequency of occurrence.  In [JSON-XML] it is shown that memory
   and CPU usage for sending JSON encoded or XML encoded objects led on
   average to a 50% lower resource usage for JSON.  Consequently, from a
   resource utilization point of view EXI and CBOR seem the right
   choice.  CBOR does not need a schema, but EXI requires one for
   decoding.  Consequently, for EXI different schema versions must be
   handled by a versioning scheme.

   The end goal of CoMI is to provide information exchange over the CoAP
   transport protocol in a uniform manner to approach the full
   management functionality as specified in
   [I-D.ersue-constrained-mgmt].

1.1.  Terminology

   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].

   Readers of this specification are required to be familiar with all
   the terms and concepts discussed in [RFC3410], [RFC3416], and
   [RFC2578].

   Core Management Interface (CoMI) specifies the profile of Function
   Sets which access MIBs with the purpose of managing the operation of
   constrained devices in a network.

   The following list defines the terms used in this document:

   Managing Entity:  An entity that manages one or more managed devices.
      Within the CoMI framework, the managing entity acts as a CoAP
      client for CoMI.

   Managed Device:  An entity that is being managed.  The managed device
      acts as a CoAP server for CoMI.

   NOTE: It is assumed that the managed device is the most constrained
   entity.  The managing entity might be more capable, however this is
   not necessarily the case.

   The following list contains the abbreviations used in this document.





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   OID:  ASN.1 OBJECT-IDENTIFIER, which is used to uniquely identify MIB
      objects in the managed device

2.  CoAP Interface

   In CoRE a group of links can constitute a Function Set. The format of
   the links is specified in [I-D.ietf-core-interfaces].  This note
   specifies a Management Function Set. CoMI end-points that implement
   the CoMI management protocol support at least one discoverable
   management resource of resource type (rt): core.mg, with path: /mg,
   where mg is short-hand for management.  The mg resource has one sub-
   resource accessible with the path:

   o  MIB with path /mg/mib and an XML (EXI), JSON or CBOR content
      format.

   The mib resource provides access to the MIBs described in
   Section 3.2.  The mib resource is introduced as a sub resource to mg
   to permit later additions to CoMI mg resource.

   XML and JSON schemas describe the structure of the MIBs.  It is
   expected that given the verbosity of XML and JSON, CoMI messages will
   mostly use EXI or CBOR.  The profile of the management function set,
   with IF=core.mg.mib, is shown in the table below, following the
   guidelines of [I-D.ietf-core-interfaces]:

     +-----------------+----------+--------------+-------------------+
     | name            | path     | RT           | Data Type         |
     +-----------------+----------+--------------+-------------------+
     | Management      | /mg      | core.mg      | n/a               |
     |                 |          |              |                   |
     | MIB             | /mg/mib  | core.mg.mib  | application/json  |
     |                 |          |              |                   |
     | MIB             | /mg/mib  | core.mg.mib  | application/cbor  |
     |                 |          |              |                   |
     | MIB             | /mg/mib  | core.mg.mib  | application/xml   |
     |                 |          |              |                   |
     | MIB             | /mg/mib  | core.mg.mib  | application/exi   |
     +-----------------+----------+--------------+-------------------+


   The value of the EXI events have a different meaning dependent on the
   accompanying schema file.  Schemas are sent to the device at
   initialization such that it can prepare the parsing tables in
   advance.  Schema management is discussed in Section 7.  No such
   schema is needed for CBOR.





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3.  MIB Function Set

   The MIB Function Set provides a CoAP interface to perform equivalent
   functions to the ones provided by SNMP.  Section 3.1 explains the
   structure of SNMP PDUs and their transport.

3.1.  SNMP/MIB architecture

   The architecture of the Internet Standard management framework
   consists of:

   o  A data definition language that is referred to as Structure of
      Management Information (SMI)[RFC2578].

   o  The Management Information Base (MIB) which contains the
      information to be managed and is defined for each specific
      function to be managed [RFC3418].

   o  A protocol definition referred to as Simple Network Management
      Protocol (SNMP) [RFC3416].

   o  Security and administration that provides SNMP message based
      security on the basis of the user-based security model [RFC3414].

   Separation in modules was motivated by the wish to respond to the
   evolution of Internet.  The protocol part (SNMP) and data definition
   part (MIB) are independent of each other.  The separation has enabled
   the progressive passage from SNMPv1 via SNMPv2 to SNMPv3.  This draft
   leverages this separation to replace the SNMP protocol with a CoAP
   based protocol.

3.1.1.  SNMP functions

   The SNMP protocol supports seven types of access supported by as many
   Protocol Data Unit (PDU) types:

   o  Get Request, transmits a list of OBJECT-IDENTIFIERs to be paired
      with values.

   o  GetNext Request, transmits a list of OBJECT-IDENTIFIERs to which
      lexicographic successors are returned for table traversal.

   o  GetBulk Request, transmits a list of OBJECT-IDENTIFIERs and the
      maximum number of expected paired values.

   o  Response, returns an error or the (OBJECT-IDENTIFIER, value) pairs
      for the OBJECT-IDENTIFIERs specified in Get, GetNext, GetBulk,
      Set, or Inform Requests.



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   o  Set Request, transmits a list of (OBJECT-IDENTIFIERs, value) pairs
      to be set in the specified MIB object.

   o  Trap, sends an unconfirmed message with a list of (OBJECT-
      IDENTIFIERs, value) pairs to a notification requesting end-point.

   o  Inform Request, sends a confirmed message with a list of (OBJECT-
      IDENTIFIERs, value) pairs to a notification requesting end-point.

   The binding of the notification to a destination is discussed in
   Section 6.

3.1.2.  MIB structure

   A MIB module is composed of MIB objects.  MIB objects have a
   descriptor and an identifier: OBJECT-IDENTIFIER (OID).  The
   identifier, following the OSI hierarchy, is an ordered list of non-
   negative numbers [RFC2578].  OID values are unique.  Each number in
   the list is referred as a sub-identifier.  One descriptor can be
   related to several OIDs.

   A MIB object is usually a scalar object.  A MIB object may have a
   tabular form with rows and columns.  Such an object is composed of a
   sequence of rows, with each row composed of a sequence of typed
   values.  An index value identifies the row in the table.

   In SMI, a table is constructed as a SEQUENCE OF its entries.  For
   example, the IpAddrTable from [RFC4293] has the following definition:


   ipv6InterfaceTable OBJECT-TYPE
     SYNTAX                      SEQUENCE OF Ipv6InterfaceEntry
     MAX-ACCESS                  not-accessible
     STATUS                      current
     DESCRIPTION
       "The table containing per-interface IPv6-specific
       information."
   ::= { ip 30 }

   ipv6InterfaceEntry OBJECT-TYPE
     SYNTAX                      Ipv6InterfaceEntry
     MAX-ACCESS                  not-accessible
     STATUS current
     DESCRIPTION
       "An entry containing IPv6-specific information for a given
       interface."
     INDEX { ipv6InterfaceIfIndex }
   ::= { ipv6InterfaceTable 1 }



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   Ipv6InterfaceEntry ::= SEQUENCE {
     ipv6InterfaceIfIndex        InterfaceIndex,
     ipv6InterfaceReasmMaxSize   Unsigned32,
     ipv6InterfaceIdentifier     Ipv6AddressIfIdentifierTC,
     ipv6InterfaceEnableStatus   INTEGER,
     ipv6InterfaceReachableTime  Unsigned32,
     ipv6InterfaceRetransmitTime Unsigned32,
     ipv6InterfaceForwarding     INTEGER
   }



   The name of the MIB table is used for the name of the CoMI variable.
   However, there is no explicit mention of the names
   "ipv6InterfaceEntry" and "Ipv6InterfaceEntry".  Instead, the value of
   the main CoMI variable consists of an array, each element of which
   contains 7 CoMI variables: one element for "ipv6InterfaceIfIndex",
   one for "ipv6InterfaceReasmMaxSize" and so on until
   "ipv6InterfaceForwarding".

3.2.  CoMI Function Set

   Two types of interfaces are supported by CoMI:

   single value  Reading/Writing one MIB variable, specified in the URI
      with path /mg/mib/descriptor or with path /mg/mib/OID.

   multiple values  Reading writing arrays or multiple MIB variables,
      specified in the payload.

   A MIB object has a descriptor and an OID that identifies it uniquely
   within the device.  MIB objects are standardized by the IETF or by
   other relevant Standards Developing Organizations (SDO).

   The examples in this section use a payload with one or more entries
   describing the pair (descriptor, value), or (OID, value).  The syntax
   of the payloads is specified in Section 4.

3.2.1.  Single MIB values

   A request to read the value of a MIB variable is sent with a
   confirmable CoAP GET message.  The single MIB variable is specified
   in the URI path with the OID or descriptor suffixing the /mg/mib/
   path name.  A request to set a value is sent with a confirmable CoAP
   PUT message.  The Response is piggybacked to the CoAP ACK message
   corresponding with the Request.





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   Using for example the same MIB from [RFC1213] as used in [RFC3416], a
   request is sent to retrieve the value of sysUpTime.  The answer to
   the request returns a (descriptor, value) pair.  The syntax of the
   payload is specified in Section 4.


   REQ: GET example.com/mg/mib/sysUpTime

   RES: 2.05 Content (Content-Format: application/xxxx)
   (sysUpTime, "123456")


   The specified object can be a table.  The returned payload is
   composed of all the rows associated with the table.  Each row is
   returned as a set of (column name, value) pairs.  For example the a
   GET of the ipNetToMediaTable, sent by the managing entity, results in
   the following returned payload sent by the managed entity:


   REQ: GET example.com/mg/mib/ipNetToMediaTable

   RES: 2.05 Content (Content-Format: application/xxxx)
       ((ipNetToMediaIfIndex , 1)
       (ipNetToMediaPhysAddress , "00:00::10:01:23:45")
       (ipNetToMediaNetAddress, "10.0.0.51")
       (ipNetToMediaType , "static")
       )(
       (ipNetToMediaIfIndex , 1)
       (ipNetToMediaPhysAddress , "00:00::10:54:32:10")
       (ipNetToMediaNetAddress, "9.2.3.4")
       (ipNetToMediaType , "dynamic")
       )(
       (ipNetToMediaIfIndex , 2)
       (ipNetToMediaPhysAddress , "00:00::10:98:76:54")
       (ipNetToMediaNetAddress, "10.0.0.15")
       (ipNetToMediaType , "dynamic"))


   The used syntax is for demonstration purposes only.  Rows are
   encapsulated witin brackets, similar to the individual row elements.
   The syntax of the payload is specified in Section 4.

   It is possible that the size of the returned payload is too large to
   fit in a single message.  CoMI gives the possibility to send the
   contents of the objects in several fragments with a maximum size.
   The "sz" link-format attribute [RFC6690] can be used to specify the
   expected maximum size of the mib resource in (identifier, value)
   pairs.  The returned data MUST terminate with a complete (identifier,



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   value) pair.  The sequel can be asked by sending the same request but
   with a uri-query indicating the offset of the first of the next
   requested pairs.  This offset is equal to the already received number
   of pairs.  The uri-query has the form "of=" (without the quotes)
   followed by the offset as an integer in text format.

3.2.2.  multi MIB values

   A request to read multiple MIB variables is done by expressing the
   pairs (MIB descriptor, null) in the payload of the GET request
   message.  A request to set multiple MIB variables is done by
   expressing the pairs (MIB descriptor, null value) in the payload of
   the PUT request message.

3.2.3.  Table row

   The managing entity MAY be interested only in certain table entries.
   One way to specify a row is to specify its row number in the URI with
   the "row" uri-query attribute.  The specification of row=1 returns
   row 1 values of the ipNetToMediaTable in the example:


   REQ: GET example.com/mg/mib/ipNetToMediaTable?row=1

   RES: 2.05 Content (Content-Format: application/xxxx)
       (ipNetToMediaIfIndex , 1)
       (ipNetToMediaPhysAddress , "00:00::10:01:23:45")
       (ipNetToMediaNetAddress, "10.0.0.51")
       (ipNetToMediaType , "static")


   An alternative mode of selection is by specifying the value of the
   INDEX atttributes.  Towards this end, the managing entity can include
   the required entries in the payload of its "GET" request by
   specifying the values of the index attributes.

   For example, to obtain a table entry from ipNetToMediaTable, the rows
   are specified by specifying the index attributes: ipNetToMediaIfIndex
   and ipNetToMediaNetAddress.  The managing entity could have sent a
   GET with the following payload:


   REQ: GET example.com/mg/mib/ipNetToMediaTable
        (ipNetToMediaIfIndex , 1)
       (ipNetToMediaNetAddress, "9.2.3.4")

   RES: 2.05 Content (Content-Format: application/xxxx)
       (ipNetToMediaIfIndex , 1)



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       (ipNetToMediaPhysAddress , "00:00::10:54:32:10")
       (ipNetToMediaNetAddress, "9.2.3.4")
       (ipNetToMediaType , "dynamic")


   Constrained devices MAY support this kind of filtering.  However, if
   they don't support it, they MUST ignore the payload in the GET
   request and handle the message as if the payload was empty.

   It is advised to keep MIBs for constrained entities as simple as
   possible, and therefore it would be best to avoid extensive tables.

3.2.4.  Error returns

   When a variable with the specified name cannot be processed, CoAP
   Error code 5.01 is returned.  In addition, a MIB specific error can
   be returned in the payload.  Two types of error code can be returned:
   exception or error-status as specified in Appendix A, according to
   the rules of [RFC3416].  For example when MIB "variable" does not
   exist:

   REQ: GET example.com/mg/mib/variable

   RES: 5.01 Not Implemented (Content-Format: application/xxx)
   (exception, nosuchobject)


4.  Mapping SMI to CoMI payload

   The SMI syntax is mapped to XML, CBOR, and JSON syntax, necessary for
   the transport of MIB data in the CoAP payload.

4.1.  Mapping SMI to JSON

   MIB information can be stored in JSON through a JSON object
   containing a set of Name-Value pairs, where each pair has the
   following syntax:

   Name : Value

   "Name" is a string that either contains the variable descriptor from
   the SMI definition, or the OID of the associated variable.  In the
   latter case, the "Name" string has the following ABNF syntax, where
   we borrow some ABNF definitions from [I-D.ietf-json-rfc4627bis]:

   descriptor = quotation-mark oid-prefix int *(underscore int)
                quotation-mark




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   oid-prefix = %x6f %x69 %x64 underscore                      ; 'oid_'

   underscore = %x5f                                           ; '_'


   In other words, when "Name" contains an OID, it is represented as a
   JSON string in which the dots of the OID are replaced by underscores,
   and the OID is prefixed by "oid_".

   The "Value" field contains the variable value, using the JSON data
   type as indicated in Table 1.

   +-----------------------+----------------+--------------------------+
   | SMI type              | JSON type      | Specification            |
   +-----------------------+----------------+--------------------------+
   | OBJECT-IDENTIFIER     | array of       |                          |
   |                       | integers       |                          |
   |                       |                |                          |
   | Integer32             | integer        |                          |
   |                       |                |                          |
   | INTEGER               | integer        |                          |
   |                       |                |                          |
   | OCTET-STRING          | Base64 encoded |                          |
   |                       | string         |                          |
   |                       |                |                          |
   | BITS                  | array of       | The integers can only    |
   |                       | integers       | take the values 0 and 1. |
   |                       |                |                          |
   | IpAddress             | string         | [RFC4291]                |
   |                       |                |                          |
   | Counter32             | integer        |                          |
   |                       |                |                          |
   | Gauge32               | integer        |                          |
   |                       |                |                          |
   | TimeTicks             | integer        |                          |
   |                       |                |                          |
   | Counter64             | integer        |                          |
   |                       |                |                          |
   | Unsigned32            | integer        |                          |
   |                       |                |                          |
   | Table                 | array          | Section 4.1.1            |
   +-----------------------+----------------+--------------------------+

                 Table 1: Conversion of SMI types to JSON

   For example, the number of UDP datagrams received can be obtained
   through the udpInDatagrams variable as specified in [RFC4113].  It
   could have the following outcome:



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   {
     "udpInDatagrams" : 82174
   }


   Alternatively, when the response uses an OID instead of the variable
   identifier, the outcome would be as follows:

   {
     "oid_1_3_6_1_2_1_7_1" : 82174
   }


   Another example of a JSON encoding of two (fictional) MIB variables
   "aBitString" and "anObjectID", with types BITS and OBJECT-IDENTIFIER,
   is as follows:

   {
     "aBitString" : [ 0, 1, 0, 0, 1, 1 ],
     "anObjectID" : [ 1, 3, 6, 1, 10 ]
   }


4.1.1.  Tables in JSON

   If a MIB object is a table, it is represented as an array of rows,
   the elements of which contain tuples related to the rows.

   For example, an udpEndpointTable would be encoded as follows:


   {
     "udpEndpointTable" : [
       {
         "udpEndpointLocalAddressType" : 2,
         "udpEndpointLocalAddress" : "2001:D3B8::417A",
         "udpEndpointLocalPort" : 5683,
         "udpEndpointRemoteAddressType" : 2,
         "udpEndpointRemoteAddress" : "2001:5C3D::59C1",
         "udpEndpointRemotePort" : 8000,
         "udpEndpointInstance" : 14789215,
         "udpEndpointProcess" : 61572493
       },
       {
         "udpEndpointLocalAddressType" : 2,
         "udpEndpointLocalAddress" : "2001:D3B8::417A",
         "udpEndpointLocalPort" : 5683,
         "udpEndpointRemoteAddressType" : 2,



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         "udpEndpointRemoteAddress" : "4301:5338::DFC1",
         "udpEndpointRemotePort" : 6000,
         "udpEndpointInstance" : 14892714,
         "udpEndpointProcess" : 157491
       }
     ]
   }


4.2.  Mapping SMI to CBOR

   CBOR [I-D.bormann-cbor] is a binary format designated for the
   transmission of structured information.  This section discusses how
   CBOR can be used to exchange MIB data.

   The MIB variables are represented in a CBOR map of indefinite length.
   Such a map is a list of paired data fields.  The first data field of
   each pair contains either a string containing the name of the MIB
   variable, or an array of integers containing the MIB variable's OID.
   The second datafield contains the variable's value.

   Table 2 gives an overview of the conversion from SMI to CBOR.  If the
   first element of a pair in the map contains an OID, it uses the same
   CBOR format for the first element as defined in the table in the
   "OBJECT-IDENTIFIER" row.

   +-----------------------+----------------+--------------------------+
   | SMI type              | CBOR type      | Specification            |
   +-----------------------+----------------+--------------------------+
   | OBJECT-IDENTIFIER     | array of       | First element            |
   |                       | unsigned       | corresponds to the most  |
   |                       | integers       | left number in the OID.  |
   |                       |                |                          |
   | Integer32             | unsigned       |                          |
   |                       | integer or     |                          |
   |                       | negative       |                          |
   |                       | integer        |                          |
   |                       |                |                          |
   | INTEGER               | unsigned       |                          |
   |                       | integer or     |                          |
   |                       | negative       |                          |
   |                       | integer        |                          |
   |                       |                |                          |
   | OCTET-STRING          | byte string    |                          |
   |                       |                |                          |
   | BITS                  | array of       | The integers can only    |
   |                       | unsigned       | take the values 0 and 1. |
   |                       | integers       |                          |



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   |                       |                |                          |
   | IpAddress             | text string    | [RFC4291]                |
   |                       |                |                          |
   | Counter32             | unsigned       |                          |
   |                       | integer        |                          |
   |                       |                |                          |
   | Gauge32               | unsigned       |                          |
   |                       | integer        |                          |
   |                       |                |                          |
   | TimeTicks             | unsigned       |                          |
   |                       | integer        |                          |
   |                       |                |                          |
   | Counter64             | unsigned       |                          |
   |                       | integer        |                          |
   |                       |                |                          |
   | Unsigned32            | unsigned       |                          |
   |                       | integer        |                          |
   |                       |                |                          |
   | Table                 | array  of maps | Section 4.2.1            |
   +-----------------------+----------------+--------------------------+

                 Table 2: Conversion of SMI types to CBOR

   For example, the variable "udpInDatagrams" of SMI type "Counter32"
   and value "82174" is reflected in CBOR as follows:

   BF                                              # map (indefinite)
      6E 75 64 70 49 6E 44 61 74 61 67 72 61 6D 73 # "udpInDatagrams"
      1A 00 01 40 FE                               # 32-bit int 82174
   FF                                              # end of map


   Or alternatively, using the OID of "udpInDatagrams":

   BF                                              # map (indefinite)
      88 01 03 06 01 02 01 07 01                   # 1.3.6.1.2.1.7.1
      1A 00 01 40 FE                               # 32-bit int 82174
   FF                                              # end of map


4.2.1.  Tables in CBOR

   In case a MIB variable is a table, it is represented in CBOR with a
   indefinite length array of maps.

   The array corresponds to the rows in the MIB table, and its elements
   consist of maps corresponding to the elements of each row.  The
   encoding of the maps has the same syntax as the main map.



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   For example, the "udpEndpointTable" from Section 3.1.2 would be
   encoded in CBOR as follows:

   BF                                  # main map (indefinite)
      70 75 64 70 45 6E 64 70 6F 69 6E
      74 54 61 62 6C 65                # "udpEndpointTable"
      9F                               # array (indefinite)
         BF                            # map for first row
            78 1B 75 64 70 45 6E 64 70
            6F 69 6E 74 4C 6F 63 61 6C
            41 64 64 72 65 73 73 54 79
            70 65                      # "udpEndpointLocalAddressType"
            02                         # integer 2
            77 75 64 70 45 6E 64 70 6f
            69 6e 74 4C 6f 63 61 6C 41
            64 64 72 65 73 73          # "udpEndpointLocalAddress"
            6f 32 30 30 31 3A 44 33 42
            38 3A 3A 34 31 37 41       # "2001:D3B8::417A"
            74 75 64 70 45 6E 64 70 6F
            69 6E 74 4C 6f 63 61 6C 50
            6F 72 74                   # "udpEndpointLocalPort"
            19 16 33                   # 5683
            78 1C 75 64 70 45 6E 64 70
            6F 69 6E 74 52 65 6D 6F 74
            65 41 64 64 72 65 73 73 54
            79 70 65                   # "udpEndpointRemoteAddressType"
            02                         # 2
            78 18 75 64 70 45 6E 64 70
            6F 69 6E 74 52 65 6D 6F 74
            65 41 64 64 72 65 73 73    # "udpEndpointRemoteAddress"
            6F 32 30 30 31 3A 35 43 33
            44 3A 3A 35 39 43 31       # "2001:5C3D::59C1"
            75 75 64 70 45 6E 64 70 6F
            69 6E 74 52 65 6D 6F 74 65
            50 6F 72 74                # "udpEndpointRemotePort"
            19 1F 40                   # 8000
            73 75 64 70 45 6E 64 70 6F
            69 6E 74 49 6E 73 74 61 6E
            63 65                      # "udpEndpointInstance"
            1A 00 E1 AA 5F             # 14789215
            72 75 64 70 45 6E 64 70 6F
            69 6E 74 50 72 6F 63 65 73
            73                         # "udpEndpointProcess"
            1A 03 AB 85 8D             # 61572493
         FF                            # end of first row
         BF                            # map for second row
            78 1B 75 64 70 45 6E 64 70
            6F 69 6E 74 4C 6F 63 61 6C



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            41 64 64 72 65 73 73 54 79
            70 65                      # "udpEndpointLocalAddressType"
            02                         # integer 2
            77 75 64 70 45 6E 64 70 6F
            69 6E 74 4C 6F 63 61 6C 41
            64 64 72 65 73 73          # "udpEndpointLocalAddress"
            6F 32 30 30 31 3A 44 33 42
            38 3A 3A 34 31 37 41       # "2001:D3B8::417A"
            74 75 64 70 45 6E 64 70 6F
            69 6E 74 4C 6F 63 61 6C 50
            6F 72 74                   # "udpEndpointLocalPort"
            19 16 33                   # 5683
            78 1C 75 64 70 45 6E 64 70
            6F 69 6E 74 52 65 6D 6F 74
            65 41 64 64 72 65 73 73 54
            79 70 65                   # "udpEndpointRemoteAddressType"
            02                         # 2
            78 18 75 64 70 45 6E 64 70
            6F 69 6E 74 52 65 6D 6F 74
            65 41 64 64 72 65 73 73    # "udpEndpointRemoteAddress"
            6F 34 33 30 31 3A 35 33 33
            38 3A 3A 44 46 43 31       # "4301:5338::DFC1"
            75 75 64 70 45 6E 64 70 6F
            69 6E 74 52 65 6D 6F 74 65
            50 6F 72 74                # "udpEndpointRemotePort"
            19 17 70                   # 6000
            73 75 64 70 45 6E 64 70 6F
            69 6E 74 49 6E 73 74 61 6E
            63 65                      # "udpEndpointInstance"
            1A 00 E3 3E AA             # 14892714
            72 75 64 70 45 6E 64 70 6F
            69 6E 74 50 72 6F 63 65 73
            73                         # "udpEndpointProcess"
            1A 00 02 67 33             # 157491
         FF                            # end of second row
      FF                               # end of array
   FF                                  # end of main map


   TBD: we may consider splitting up the CBOR definition in two parts,
   the first part containing a translation table with ( integer,
   descriptor/oid ) pairs, the second as above but using instead of the
   descriptor/oid the integers defined in the translation table.  This
   would increase coding efficiency, but requires some extra work
   especially on the client (managing entity) side.  This suggestion
   would lead to the following CBOR data:

   82                                  # two element array



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      BF                               # translation map (indefinite)
         00                            # 0:
            70 75 64 70 45 6E 64 70 6F
            69 6E 74 54 61 62 6C 65    # "udpEndpointTable"
         01                            # 1:
            78 1B 75 64 70 45 6E 64 70
            6F 69 6E 74 4C 6F 63 61 6C
            41 64 64 72 65 73 73 54 79
            70 65                      # "udpEndpointLocalAddressType"
         02                            # 2:
            77 75 64 70 45 6E 64 70 6f
            69 6e 74 4C 6f 63 61 6C 41
            64 64 72 65 73 73          # "udpEndpointLocalAddress"
         03                            # 3:
            74 75 64 70 45 6E 64 70 6F
            69 6E 74 4C 6f 63 61 6C 50
            6F 72 74                   # "udpEndpointLocalPort"
         04                            # 4:
            78 1C 75 64 70 45 6E 64 70
            6F 69 6E 74 52 65 6D 6F 74
            65 41 64 64 72 65 73 73 54
            79 70 65                   # "udpEndpointRemoteAddressType"
         05                            # 5:
            78 18 75 64 70 45 6E 64 70
            6F 69 6E 74 52 65 6D 6F 74
            65 41 64 64 72 65 73 73    # "udpEndpointRemoteAddress"
         06                            # 6:
            75 75 64 70 45 6E 64 70 6F
            69 6E 74 52 65 6D 6F 74 65
            50 6F 72 74                # "udpEndpointRemotePort"
         07                            # 7:
            73 75 64 70 45 6E 64 70 6F
            69 6E 74 49 6E 73 74 61 6E
            63 65                      # "udpEndpointInstance"
         08                            # 8:
            72 75 64 70 45 6E 64 70 6F
            69 6E 74 50 72 6F 63 65 73
            73                         # "udpEndpointProcess"
      FF
      BF                               # variables map (indefinite)
         00                            # 0="udpEndpointTable"
         9F                            # array (indefinite)
            BF                         # map for first row
               01                      # 1="udpEndpointLocalAddressType"
               02                      # integer 2
               02                      # 2="udpEndpointLocalAddress"
               6f 32 30 30 31 3A 44 33
               42 38 3A 3A 34 31 37 41 # "2001:D3B8::417A"



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               03                      # 3="udpEndpointLocalPort"
               19 16 33                # 5683
               04                      # 4="udpEndpointRemoteAddressType"
               02                      # 2
               05                      # 5="udpEndpointRemoteAddress"
               6F 32 30 30 31 3A 35 43
               33 44 3A 3A 35 39 43 31 # "2001:5C3D::59C1"
               06                      # 6="udpEndpointRemotePort"
               19 1F 40                # 8000
               07                      # 7="udpEndpointInstance"
               1A 00 E1 AA 5F          # 14789215
               08                      # 8="udpEndpointProcess"
               1A 03 AB 85 8D          # 61572493
            FF                         # end of first row
            BF                         # map for second row
               01                      # 1="udpEndpointLocalAddressType"
               02                      # integer 2
               02                      # 2="udpEndpointLocalAddress"
               6F 32 30 30 31 3A 44 33
               42 38 3A 3A 34 31 37 41 # "2001:D3B8::417A"
               03                      # 3="udpEndpointLocalPort"
               19 16 33                # 5683
               04                      # 4="udpEndpointRemoteAddressType"
               02                      # 2
               05                      # 5="udpEndpointRemoteAddress"
               6F 34 33 30 31 3A 35 33
               33 38 3A 3A 44 46 43 31 # "4301:5338::DFC1"
               06                      # 6="udpEndpointRemotePort"
               19 17 70                # 6000
               07                      # 7="udpEndpointInstance"
               1A 00 E3 3E AA          # 14892714
               08                      # 8="udpEndpointProcess"
               1A 00 02 67 33          # 157491
            FF                         # end of second row
         FF                            # end of array
      FF                               # end of main map


   Obviously this leads to less bytes to transmit, but it needs to
   define an extra translation table.  The server can include the fixed
   mapping as a macro, so it does not need to calculate it for each
   request.  In this example the translation map is for the whole
   structure.  The map can be restricted to the entries that are used.

4.3.  Mapping SMI to XML






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   The types specified by SMI can be represented by a XML syntax
   according to the specification in this section.  The XML syntax is
   taken over from http://www.w3c.org/2001/XMLSchema-datatypes.

     +---------------------+------------------------+---------------+
     | SMI type            | XML type               | Specification |
     +---------------------+------------------------+---------------+
     | OBJECT-IDENTIFIER:  | array of int           |               |
     |                     |                        |               |
     | Integer32:          | int                    |               |
     |                     |                        |               |
     | INTEGER:            | int                    |               |
     |                     |                        |               |
     | OCTET-STRING:       | Base64 encoded string  |               |
     |                     |                        |               |
     | BITS:               | bits                   | Appendix A    |
     |                     |                        |               |
     | IPAddress:          | string                 | [RFC4291]     |
     |                     |                        |               |
     | Counter32:          | nonNegativeInteger     |               |
     |                     |                        |               |
     | Gauge32:            | nonNegativeInteger     |               |
     |                     |                        |               |
     | TimeTicks:          | time                   |               |
     |                     |                        |               |
     | Counter64:          | unsignedlong           |               |
     |                     |                        |               |
     | Unsigned32:         | unsignedInt            |               |
     |                     |                        |               |
     | Table               | MIBTable               | Appendix A    |
     +---------------------+------------------------+---------------+

                  Table 3: Conversion of SMI types to XML

4.3.1.  Tables in XML

   In case a MIB variable is a table, it is represented in XML with an
   indefinite length SEQUENCE of type entry.  Each element of entry has
   a name and a choice of XML types.  The associated schema is shown in
   Appendix A. For example the udpEndPointTable would look like:

   <MIBTable>
     <MIBidentifier>
        <descriptor>"udpEndpointTable"</descriptor>
     </MIBidentifier>
     <row>
        <entry name="udpEndpointLocalAddressType" value="2"/>
       <entry name="udpEndpointLocalAddress" value="2001:D3B8::417A"/>



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       <entry name="udpEndpointLocalPort" value="5683"/>
   <entry name="udpEndpointRemoteAddressType" value="2"/>
       <entry name="udpEndpointRemoteAddress" value="2001:5C3D::59C1"/>
       <entry name="udpEndpointRemotePort" value="8000"/>
       <entry name="udpEndpointInstance" value="14789215"/>
       <entry name="udpEndpointProcess" value="61572493"/>
     </row>
     <row>
       <entry name="udpEndpointLocalAddressType" value="2"/>
       <entry name="udpEndpointLocalAddress" value="2001:D3B8::417A"/>
       <entry name="udpEndpointLocalPort" value="5683"/>
       <entry name="udpEndpointRemoteAddressType" value="2"/>
       <entry name="udpEndpointRemoteAddress" value="4301:5338::DFC1"/>
       <entry name="udpEndpointRemotePort" value="6000"/>
       <entry name="udpEndpointInstance" value="147892714"/>
       <entry name="udpEndpointProcess" value="157491"/>
     </row>
   </MIBTable>


   When the MIBidentifier is an OID the syntax for MIB object
   1.3.6.1.2.1.1.3 looks like:

   <MIBObject>
     <MIBidentifier>
        <oid>
          <ident>1</ident>
          <ident>3</ident>
          <ident>6</ident>
          <ident>1</ident>
          <ident>2</ident>
          <ident>1</ident>
          <ident>1</ident>
          <ident>3</ident>
       </oid>
     </MIBidentifier>
     <MIBvalue value="324"/>
   </MIBObject>


5.  MIB discovery

   MIB objects are discovered like resources with the standard CoAP
   resource discovery.  Performing a GET on "/.well-known/core" with
   rt=core.mg.mib returns all MIB descriptors and all OIDs which are
   available on this device.  For table objects there is no further
   possibility to discover the row descriptors.  For example, consider
   there are two MIB objects with descriptors "sysUpTime" and



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   "ipNetToMediaTable" associated with OID 1.3.6.1.2.1.1.3 and
   1.3.6.1.2.1.4.22

   REQ: GET example.com/.well-known/core?rt=core.mg.mib

   RES: 2.05 Content (Content-Format: application/text)
   </mg/mib/sysUpTime>;rt="core.mg.mib";oid="1.3.6.1.2.1.1.3"
   </mg/mib/ipNetToMediaTable>;rt="core.mg.mib";oid="1.3.6.1.2.1.4.22"


   The link format attribute 'oid' is used to associate the name of the
   MIB resource with its OID.  The OID is written as a string in its
   conventional form.

   Notice that a MIB variable normally is associated with a descriptor
   and an OID.  The OID is unique, whereas the descriptor may not.

6.  Trap functions

   A trap can be set through the CoAP Observe [I-D.ietf-core-observe]
   function.  As regular with Observe, the managing entity subscribes to
   the variable by sending a GET request with an "Observe" option.

   In the registration request, the managing entity MAY include a
   "Response-To-Uri-Host" and optionally "Response-To-Uri-Port" option
   as defined in [I-D.becker-core-coap-sms-gprs].  In this case, the
   observations SHOULD be sent to the address and port indicated in
   these options.  This can be useful when the managing entity wants the
   managed device to send the trap information to a multicast address.

7.  MIB access management

   Setting up parameter values and establishing relations between
   devices during commissioning of a managed network is needed for the
   TRAP function.  Draft [I-D.ietf-core-interfaces] describes the
   binding of end-points to end-points on remote devices.  This is just
   a table that contains the destination addresses of the MIB variables.
   A list of objects describing different aspects of commissioning
   comprise:

   o  Binding table as described in [I-D.ietf-core-interfaces], schema
      presented in Appendix B.1.

   o  Notification sources as referred to in [RFC3416], schema presented
      in Appendix B.1.

   o  Names of files containing the schemas to be expected, schema
      presented in Appendix B.2.



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   The object with type "binding table" contains a sequence of bindings.
   The contents of bindings contains the methods, location, the interval
   specifications, and the step value as suggested in
   [I-D.ietf-core-interfaces].  The method "notify" has been added to
   the binding methods "poll", "obs" and "push", to cater for the
   binding of notification source to the receiver.

   The object of type "Schema-files" contains a sequence of schema files
   describing the data structure transportable in CoMI messages.

8.  Security Considerations

   TODO: follows CoAP security provisioning.

9.  IANA Considerations

   'rt="core.mg.mib"' needs registration with IANA.

   Content types to be registered:

   o  application/comi+xml

   o  application/comi+exi

   o  application/comi+json

   o  application/comi+cbor

10.  Acknowledgements

   Mehmet Ersue and Bert Wijnen explained the encoding aspects of PDUs
   transported under SNMP.  Carsten Bormann has given feedback on the
   use of CBOR.  The draft has benefited from comments by Dee Denteneer,
   Esko Dijk, and Michael van Hartskamp.

11.  Changelog

   Changes from version 00 to version 01

   o  Focus on MIB only

   o  Introduced CBOR, JSON, removed BER

   o  defined mappings from SMI to xx

   o  Introduced the concept of addressable table rows





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12.  References

12.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [I-D.bormann-cbor]
              Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", draft-bormann-cbor-09 (work in
              progress), September 2013.

   [I-D.becker-core-coap-sms-gprs]
              Becker, M., Li, K., Poetsch, T., and K. Kuladinithi,
              "Transport of CoAP over SMS", draft-becker-core-coap-sms-
              gprs-04 (work in progress), August 2013.

   [I-D.ietf-core-observe]
              Hartke, K., "Observing Resources in CoAP", draft-ietf-
              core-observe-10 (work in progress), September 2013.

   [I-D.ietf-json-rfc4627bis]
              Bray, T., "The JSON Data Interchange Format", draft-ietf-
              json-rfc4627bis-06 (work in progress), October 2013.

12.2.  Informative References

   [RFC1213]  McCloghrie, K. and M. Rose, "Management Information Base
              for Network Management of TCP/IP-based internets:MIB-II",
              STD 17, RFC 1213, March 1991.

   [RFC2578]  McCloghrie, K., Ed., Perkins, D., Ed., and J.
              Schoenwaelder, Ed., "Structure of Management Information
              Version 2 (SMIv2)", STD 58, RFC 2578, April 1999.

   [RFC3410]  Case, J., Mundy, R., Partain, D., and B. Stewart,
              "Introduction and Applicability Statements for Internet-
              Standard Management Framework", RFC 3410, December 2002.

   [RFC3414]  Blumenthal, U. and B. Wijnen, "User-based Security Model
              (USM) for version 3 of the Simple Network Management
              Protocol (SNMPv3)", STD 62, RFC 3414, December 2002.

   [RFC3416]  Presuhn, R., "Version 2 of the Protocol Operations for the
              Simple Network Management Protocol (SNMP)", STD 62, RFC
              3416, December 2002.





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   [RFC3418]  Presuhn, R., "Management Information Base (MIB) for the
              Simple Network Management Protocol (SNMP)", STD 62, RFC
              3418, December 2002.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66, RFC
              3986, January 2005.

   [RFC4113]  Fenner, B. and J. Flick, "Management Information Base for
              the User Datagram Protocol (UDP)", RFC 4113, June 2005.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.

   [RFC4293]  Routhier, S., "Management Information Base for the
              Internet Protocol (IP)", RFC 4293, April 2006.

   [RFC4944]  Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
              "Transmission of IPv6 Packets over IEEE 802.15.4
              Networks", RFC 4944, September 2007.

   [RFC6020]  Bjorklund, M., "YANG - A Data Modeling Language for the
              Network Configuration Protocol (NETCONF)", RFC 6020,
              October 2010.

   [RFC6241]  Enns, R., Bjorklund, M., Schoenwaelder, J., and A.
              Bierman, "Network Configuration Protocol (NETCONF)", RFC
              6241, June 2011.

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, January 2012.

   [RFC6643]  Schoenwaelder, J., "Translation of Structure of Management
              Information Version 2 (SMIv2) MIB Modules to YANG
              Modules", RFC 6643, July 2012.

   [RFC6650]  Falk, J. and M. Kucherawy, "Creation and Use of Email
              Feedback Reports: An Applicability Statement for the Abuse
              Reporting Format (ARF)", RFC 6650, June 2012.

   [RFC6690]  Shelby, Z., "Constrained RESTful Environments (CoRE) Link
              Format", RFC 6690, August 2012.

   [RFC6775]  Shelby, Z., Chakrabarti, S., Nordmark, E., and C. Bormann,
              "Neighbor Discovery Optimization for IPv6 over Low-Power
              Wireless Personal Area Networks (6LoWPANs)", RFC 6775,
              November 2012.




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   [I-D.ietf-core-coap]
              Shelby, Z., Hartke, K., and C. Bormann, "Constrained
              Application Protocol (CoAP)", draft-ietf-core-coap-18
              (work in progress), June 2013.

   [I-D.ietf-core-groupcomm]
              Rahman, A. and E. Dijk, "Group Communication for CoAP",
              draft-ietf-core-groupcomm-16 (work in progress), October
              2013.

   [I-D.ietf-core-interfaces]
              Shelby, Z. and M. Vial, "CoRE Interfaces", draft-ietf-
              core-interfaces-00 (work in progress), June 2013.

   [I-D.ersue-constrained-mgmt]
              Ersue, M., Romascanu, D., and J. Schoenwaelder,
              "Management of Networks with Constrained Devices: Problem
              Statement, Use Cases and Requirements", draft-ersue-
              constrained-mgmt-03 (work in progress), February 2013.

   [STD0001]  , "Official Internet Protocols Standard", Web
              http://www.rfc-editor.org/rfcxx00.html, .

   [EXI]      , "Efficient XML Interchange", Web
              http://www.w3.org/xml/exi, .

   [XML]      , "Extensible Markup Language (XML)", Web
              http://www.w3.org/xml, .

   [JSON]     , "JavaScript Object Notation (JSON)", Web
              http://www.json.org, .

   [EXI-primer]
              Peintner, D. and S. Pericas-Geertsen, "EXI primer", Web
              http://www.w3.org/TR/exi-primer, december 2009.

   [EXI-measurement]
              White, G., KangaSharju, J., Williams, S., and D. Brutzman,
              "Efficient XML Interchange Measurements Note", Web
              http://www.w3.org/TR/2007/WD-exi-measurements-20070725,
              July 2007.

   [JSON-XML]
              Nurseitov, N., Paulson, M., Reynolds, R., and C.
              Inzurieta, "Comparison of JSON and XML Data Interchange
              Formats: A Case Study", Web
              http://www.cs.montana.edu/izurieta/pubs/caine2009.pdf,
              2009.



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Appendix A.  XML Schema for MIB

   This appendix describes the XML schema that defines the payload
   contents for MIB requests via the CoMI Function Set.  It is assumed
   that MIB variables are referred by descriptor or by OID.

   TODO: The schema needs to be updated to define basic types and
   notifications.  Access may be more sophisticated than described here.

   <xsd:simpleType name="bits">
      <xsd:restriction base="xsd:string">
        <xsd:enumeration value="bit0"/>
     <xsd:enumeration value="bit1"/>
     <xsd:enumeration value="bit2"/>
     <xsd:enumeration value="bit3"/>
     <xsd:enumeration value="bit4"/>

     <xsd:enumeration value="bitn"/>
      </xsd:restriction>
   </xsd:simpleType>

   <xsd:simpleType name="exception">
      <xsd:restriction base="xsd:string">
        <xsd:enumeration value="noSuchObject"/>
        <xsd:enumeration value="noSuchInstance"/>
        <xsd:enumeration value="endOfMibView"/>
      </xsd:restriction>
   </xsd:simpleType>

   <xsd:simpleType name="error-status">
      <xsd:restriction base="xsd:string">
        <xsd:enumeration value="noError"/>
        <xsd:enumeration  value="tooBig"/>
        <xsd:enumeration  value="noSuchName"/>
        <xsd:enumeration  value="badValue"/>
        <xsd:enumeration  value="readOnly"/>
        <xsd:enumeration  value="genErr"/>
        <xsd:enumeration  value="noAccess"/>
        <xsd:enumeration  value="wrongType"/>
        <xsd:enumeration  value="wrongLength"/>
        <xsd:enumeration  value="wrongEncoding"/>
        <xsd:enumeration  value="wrongValue"/>
        <xsd:enumeration  value="noCreation"/>
        <xsd:enumeration  value="inconsistentValue"/>
        <xsd:enumeration  value="resourceUnavailable"/>
        <xsd:enumeration  value="commitFailed"/>
        <xsd:enumeration  value="undoFailed"/>
        <xsd:enumeration  value="authorizationError"/>



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        <xsd:enumeration  value="notWritable"/>
        <xsd:enumeration  value="inconsistentName"/>
      </xsd:restriction>
   </xsd:simpleType>

   <xsd:complexType name="MIBscalar">
      <xsd:attribute name="name" type="xsd:string"/>
      <xsd:choice>
       <xsd:attribute name="value" type="xsd:string"/>
       <xsd:attribute name="value" type="xsd:integer"/>
      </xsd:choice>
   </xsd:complexType>

   <xsd:complexType name="MIBvalue">
      <xsd:choice>
       <xsd:attribute name="value" type="xsd:string"/>
       <xsd:attribute name="value" type="xsd:integer"/>
      </xsd:choice>
   </xsd:complexType>


   <xsd:complexType name ="oid">
      <xsd:sequence>
       <xsd:element name="ident" type="xsd:integer"
        minOccurs="1" maxOccurs="unbounded"/>
      </xsd:sequence>
   </xsd:complexType>

   <xsd:complexType name ="MIBidentifier">
      <xsd:choice>
       <xsd:element name="descriptor" type="xsd:string"/>
        <xsd:element name="OID" type="oid"/>
      </xsd:choice>
   </xsd:complexType>


   <xsd:complexType name="row">
      <xsd:sequence>
        <xsd:element name="entry" type="MIBscalar"
           minOccurs="0" maxOccurs="unbounded"/>
      </xsd:sequence>
   </xsd:complexType>


   <xsd:complexType name="MIBTable">
      <xsd:element name="MIBname" type="MIBidentifier"/>
      <xsd:sequence>
         <xsd:element name="Row" type="row"



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           minOccurs="1" maxOccurs="unbounded"/>
      </xsd:sequence>
   </xsd:complexType>

   <xsd:complexType name="MIBObject">
       <xsd:element name="MIBname" type="MIBidentifier"/>
       <xsd:element name="value" type="MIBvalue"/>
   </xsd:complexType>


Appendix B.  XML Schema for CoMI support

   This appendix describes the XML schema that defines the payload
   contents for requests via the CoMI Function Set to the CoMI objects
   for multicast group, binding table, and SNMP notifications.  For the
   SNMP notifications the Binding Method table specification of
   [I-D.ietf-core-interfaces]  has been extended with "notify".

B.1.  Schema for CoAP binding

   Binding table contains several simple Bindings, composed of timing
   parameters and Function signature.

   <xs:complexType name="CoAPmethod">
       <xs:restriction base="xs:string">
          <xs:enumeration value="GET"/>
          <xs:enumeration value="PUT"/>
          <xs:enumeration value="POST"/>
       </xs:restriction>
   </xs:complexType>

   <xs:complexType name="bindingMethod">
       <xs:restriction base="xs:string">
     <xs:enumeration value="poll"/>
     <xs:enumeration value="obs"/>
     <xs:enumeration value="push"/>
     <xs:enumeration value="notify"/>
       </xs:restriction>
   </xs:complexType>


   <xs:complexType name="invocation">
     <xs:element name="hostname" type="xs:string"/>
     <xs:element name="pathname" type="xs:string"/>
     <xs:element name="IPaddress" type="xs:string"/>
     <xs:element name="bindingMethod" type="bindingMethod"/>
     <xs:element name="CoAPmethod" type="CoAPmethod"/>
   </xs:complexType>



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   <xs:complexType name="simpleBinding">
        <xs:element name="method" type="invocation"/>
        <xs:element name="minPeriod" type="xs:integer"/>
        <xs:element name="maxPeriod" type="xs:integer"/>
        <xs:element name="changeStep" type="xs:integer"/>
   </xs:complexType>

   <xs:complexType name="binding Table">
     <xs:sequence>
         <xs:element name="simpleBinding" type="simpleBinding"
             minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
   </xs:complexType>



B.2.  Valid Schemas

   File names are stored in Schema

   <xs:complexType name="Schema-files">
   <xs:sequence>
         <xs:element name="Schema" type="xs:string"
           minOccurs="0" maxOccurs="unbounded"/>
   </xs:sequence>
   </xs:complexType>


Authors' Addresses

   Peter van der Stok
   consultant

   Phone: +31-492474673 (Netherlands), +33-966015248 (France)
   Email: consultancy@vanderstok.org
   URI:   www.vanderstok.org


   Bert Greevenbosch
   Huawei Technologies Co., Ltd.
   Huawei Industrial Base
   Bantian, Longgang District
   Shenzhen  518129
   P.R. China

   Email: bert.greevenbosch@huawei.com





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