Constrained Objects LanguageTrilliant Networks Inc.610 Rue du LuxembourgGranbyQuebecJ2J 2V2Canada+14503750556michel.veillette@trilliantinc.comAcklio2bis rue de la ChataigneraieCesson-SevigneBretagne35510Francea@ackl.ioTridonic GmbH & Co KGFarbergasse 15DornbirnVorarlberg6850Austria+43664808926169abhinav.somaraju@tridonic.comLandis+Gyr30000 Mill Creek AveSuite 100AlpharettaGA30022US++16782581292randy.turner@landisgyr.comhttp://www.landisgyr.com/Acklio2bis rue de la châtaigneraieCesson-SévignéBretagne35510Franceana@ackl.io
Applications and Real-Time Area (art)
Internet Engineering Task ForceCBORThis document describes a management function set adapted to constrained devices and constrained networks (e.g., low-power, lossy). CoOL objects (datastores, RPCs, actions and notifications) are defined using the YANG modelling language . Interactions with these objects are performed using the CoAP web transfer protocol . Payloads are encoded using the CBOR data format . The mapping between YANG data models and the CBOR data format is defined in .This document defines a CoAP function set for accessing YANG defined resources. YANG data models are encoded in CBOR based on the mapping rules defined in . YANG items are identified using a compact identifier called Structured Identifiers (SIDs) as defined in .The resulting protocol based on CoAP, CBOR encoded data and structured identifiers (SID) has a low implementation footprint and low network bandwidth requirements and is suitable for both constrained devices and constrained networks as defined by . This protocol is applicable to the different management topology options described by ; centralized, distributed and hierarchical.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 .The following terms are defined in :actiondata nodedata treemodulenotificationRPCschema nodeschema treesubmoduleThis specification also makes use of the following terminology:candidate configuration datastore: A configuration datastore that can be manipulated without impacting the device’s current configuration and that can be committed to the running configuration datastore. Not all devices support a candidate configuration datastore.CoOL client: The originating endpoint of a request, and the destination endpoint of a response.CoOL server: The destination endpoint of a request, and the originating endpoint of a response.delta: Within a list, a delta represents the different between the current SID and the SID of the previous entry within this list. Within a collection, a delta represents the difference between the SID assigned to the current schema node and the SID assigned to the parent. When no previous entry or parent exist, the delta is set to the absolute SID value.child: A schema node defined within a collection such as a container, a list, a case, a notification, a RPC input, a RPC output, an action input, an action output.datastore: Resource used to store and access information.endpoint: An entity participating in the CoOL protocol. Multiple CoOL endpoints may be accessible using a single CoAP endpoint. In this case, each CoOL endpoint is accessed using a distinct URI.event stream: Resource used to access notifications generated by a CoOL server. Events are defined using the YANG notification statement.function set: A group of well-known resources that provides a particular service.object: Within CoOL, an object is a data node, an RPC or an action within a datastore resource or a notification within an event stream resource.parent: The collection in which a schema node is defined.resource: Content identified by a URI.running configuration datastore: A configuration datastore holding the complete configuration currently active on the device. The running configuration datastore always exists.Structured IDentifier (SID). Unsigned integer used to identify different YANG items.The CoOL protocol is based on the client-server model. The CoOL server is the provider of the datastore resource(s) and the event stream resource(s). The CoOL client is the requester of these resources.CoOL objects are defined using the YANG modeling language . Interactions with these objects are performed using the Constrained Application Protocol (CoAP) . Payloads are encoded using the Concise Binary Object Representation (CBOR) .This specification is applicable to any transport and security protocols supported by CoAP. Implementers are free to select the most appropriate transport for the targeted applications. | CoAP Server |
+--------------+ +----------------------------------+
| | | |
| Lower layers | | Lower layers |
| | | |
+--------------+ +----------------------------------+
]]>This section lists the URIs recommended for the different CoOL resources. A CoOL server MAY implement a different set of URIs. See the Resource discovery section (Section 7.15) for more details on how a CoOL client can discover the list of URIs supported by a CoOL server using the “/.well-known/core” resource./c – The default datastore resource/c/c – The candidate configuration datastore resource/c/r - The running configuration datastore resource/c/b – The backup configuration datastore (use to implement rollbacks)/c/e - URI used to access the default event stream for this device./c/e0, /c/e1, … - URI used to access alternate event streams./c/0, /c/1, … - URI used to access a specific endpoint. Each end point represents a virtual device which can support any of the resources listed above.For example:/c/1 is the default datastore resource for endpoint 1/c/1/c is the candidate datastore resource for endpoint 1/c/1/r is the running configuration datastore resource for endpoint 1/c/1/b is the backup configuration datastore resource for endpoint 1/c/1/e is the default event stream resource for endpoint 1/c/1/e0 is an alternate event stream resource for endpoint 1All these resources are optional at the exception of the default datastore resource. The CoAP response code 4.04 (Not Found) MUST be returned when a CoOL client tries to access a resource that is unavailable.RPCs commit and cancel-commit defined in ietf-cool YANG module are available to perform the following operations on datastores:Immediate or differed commit of a candidate or backup datastore.Confirmed commitCancel of a different or confirmed commit.This section defines the different interactions supported between a CoOL client and a CoOL server.The GET method is used by CoOL clients to retrieve the entire contents of a datastore. Implementation of this function is optional and dependent of the capability of the CoOL server to transfer a relatively large response.To retrieve all instantiated data nodes of a datastore resource, a CoOL client sends a CoAP GET request to the URI of the targeted datastore. If the request is accepted by the CoOL server, a 2.05 (Content) response code is returned. The payload of the GET response MUST carry a CBOR array containing the contents of the targeted datastore. The CBOR array MUST contain a list of pairs of delta and associated value. A delta represents the difference between the current SID and the SID of the previous pair within the CBOR array. Each value is encoded using the rules defined by .The normal behaviour of a CoOL server is to exclude from the GET response, any data node currently set to its default value. When this behaviour is not appropriate for the CoOL client, this client can force the retrieval of all data nodes by using the ‘a’ Uri-Query parameter, see for more details.If the request is rejected by the CoOL server, a 5.01 Not implemented or 4.13 Request Entity Too Large response code is returned.Example:In this example, the CoOL server returns a datastore containing the following data nodes defined in the YANG module “ietf-system” and YANG module ‘ietf-interfaces’ :“/interfaces/interface” (SID 1533)“/interfaces/interface/description” (SID 1534)“/interfaces/interface/enabled” (SID 1535)“/interfaces/interface/name” (SID 1537)“/interfaces/interface/1538” (SID 1534)“/system-state/clock” (SID 1717)“/system-state/clock/boot-datetime” (SID 1718)“/system-state/clock/current-datetime” (SID 1719)“/system/clock/timezone/timezone-utc-offset/timezone-utc-offset” (SID 1736)CoAP Request:CoAP response:The FETCH method is used by the CoOL client of retrieve a subset of the data node instances within a datastore.To retrieve a list of data node instances, the CoOL client sends a CoAP FETCH request to the URI of the targeted datastore. The payload of the FETCH request contains the list of data node(s) instance to be retrieved. This list is encoded using a CBOR array, each entry containing an ‘instance-identifier’ as defined by . Within each ‘instance-identifier’, data nodes are identified using SIDs as defined by .SIDs within the list of ‘instance-identifier’ are encoded using delta. A delta represents the different between the current SID and the SID of the previous entry within this list. The delta of the first entry within the list is set to the absolute SID value.On successful processing of the CoAP request, the CoOL server MUST return a CoAP response with a response code 2.05 (Content).When a single data node is requested, the payload of the FETCH response carries the value of the data node instance requested. When multiple data nodes are requested, the payload of the FETCH response carries a CBOR array containing the value of each data node instance(s) requested. The number of entries in this CBOR array MUST match the number of “instance-identifier” requested to allow a proper interpretation of this information. The following values can be returned for each ‘instance-identifier’ requested:If the data node requested is not implemented or not instantiated, the CBOR simple value ‘undefined’ is returned.If the URI-Query parameter ‘a’ is not present in the FETCH request and the value of the data node instance is equal to the default value for this data node, the CBOR simple value ‘default’ is returned.Otherwise, the data node instance is encoded using the rules defined in .The normal behaviour of a CoOL server is to exclude from containers and list instances of a FETCH response, any data node currently set to its default value. When this behaviour is not appropriate for the CoOL client, this client can force the retrieval of all data nodes by using the ‘a’ Uri-Query parameter, see for more details.In this example, a CoOL client retrieves the leaf “/system-state/clock/current-datetime” (SID 1719) and the container “/system/clock” (SID 1734) containing the leaf “/system/clock/timezone/timezone-utc-offset/timezone-utc-offset” (SID 1736). These data nodes are defined in the YANG module “ietf-system” .CoAP request:CoAP response:CoAP requests and responses MUST be encoded in accordance with or . An encoding example is shown below:CoAP request:CoAP response:The data type ‘instance-identifier’ allows the selection of an instance of a specific data node within a list. In this example, a CoOL client retrieves the “/interfaces/interface/description” (SID 1534) leaf from the “/interfaces/interface” list. The “/interfaces/interface/name” associated to this interface is equal to “eth0”. This example is based on the YANG module “ietf-interfaces” .CoAP request:CoAP response:This “instance-identifier” extension allows the retrieval of all instances of a YANG list. To perform this operation, the CoOL client excludes from the ‘instance-identifier’ the key(s) of the targeted list. The list returned is encoded using the rules defined in section 4.4.In this example, a CoOL client retrieves the list “/interfaces/interface” (SID 1533). The response returned contain two instances, one for an Ethernet adaptor and one for a WIFI interface.CoAP request:CoAP response:To retrieve a list instance, the CoOL client MUST use an ‘instance-identifier’ with a SID set to the targeted list and the key(s) set to the value(s) associated to the targeted instance.In this example, the CoOL client requests the instance of the list “/interfaces/interface” (SID 1533) associated to the name “eth0”. The response returned by the CoOL server contains the targeted list instance formatted as YANG container.CoAP request:CoAP response:This ‘instance-identifier’ extension allows the selection of a subset of data nodes within a list. This is accomplished by adding an extra element to the ‘instance-identifier’. This element contains the subset of data nodes to be returned encoded as CBOR array. Each entry within this CBOR array is set to the delta between the current SID and the SID of targeted container as specified in the first entry of the ‘instance-identifier’.CoOL servers SHOULD implement this ‘instance-identifier’ extension. When this extension is not supported, the CoOL server MUST ignore the third element of the ‘instance-identifier’ and return the list instance as specified by the first two elements of the ‘instance-identifier’.In this example, a CoOL client retrieves from within the “/interfaces/interface” list (SID 1533) the leafs “/interfaces/interface/type” (SID 1538) and “/interfaces/interface/enabled” (SID 1535). The CoOL client also includes in this request the selection of the leaf “/system/hostname” (SID 1748) defined in “ietf-system” .For example:CoAP request:CoAP response:This ‘instance-identifier’ extension allows the efficient transfer of all instances of a data node within a YANG list. To retrieve all instances, the CoOL client excludes form the ‘instance-identifier’ the key(s) of the list containing the targeted data node.The response MUST be encoded as a CBOR ARRAY containing the available instances of the requested data node. This special encoding minimizes significantly this commonly used type of request.In this example, a CoOL client retrieves all instances of data node “/interfaces/interface/name” (SID 1537).Example:CoAP request:CoAP response:The CoAP PUT method is used by CoOL clients to update the content of a datastore.The URI of the PUT request MUST be set to the URI of the targeted datastore.The payload of the PUT request MUST carry a CBOR array containing the new content of the datastore. The CBOR array MUST contain a list of pairs of delta and associated value. A delta represents the different between the current SID and the SID of the previous pair within the CBOR array. Each value is encoded using the rules defined by .On successful processing of the CoAP request, the CoOL server MUST return a CoAP response with a response code 2.04 (Changed).A PUT request MUST be processed as an atomic transaction, if any of the data node transferred is rejected for any reason, the entire PUT request MUST be rejected and the CoOL server MUST return an appropriate error response as defined in section 6.Example:In this example, a CoOL client sets the default runtime datastore with these data nodes:“/system/clock/timezone/timezone-utc-offset/timezone-utc-offset” (SID 1736)“/system/ntp/enabled” (SID 1751)“/system/ntp/server” (SID 1752)“/system/ntp/server/name” (SID 1755)“/system/ntp/server/prefer” (SID 1756)“/system/ntp/server/transport/udp/udp” (SID 1757)“/system/ntp/server/transport/udp/udp/address” (SID 1758)“/system/ntp/server/transport/udp/udp/port” (SID 1759)CoAP request:CoAP response:The iPATCH method is used by CoOL clients to modify a subset of a datastore.To modify a datastore, the CoOL client sends a CoAP PATH request to the URI of the targeted datastore. The payload of the FETCH request contains the list of data node instance(s) to be updated, inserted or deleted. This list is encoded using a CBOR array and contains a sequence of pairs of ‘instance-identifier’ and associated values.Within each ‘instance-identifier’, data nodes are identified using SIDs as defined by . SIDs within the list are encoded as delta.On reception, the list is processed by the CoOL server as follows:If the targeted data instance already exists, this instance is replaced by the associated value (not merged). To update only some children of a collection, each child data node MUST be provided individually.If the targeted data instance doesn’t exist, this instance is created.If the targeted data instance already exists but is associated with the value ‘null’, this instance is deleted.On successful processing of the CoAP request, the CoOL server MUST return a CoAP response with a response code 2.05 (Content).A iPATCH request MUST be processed as an atomic transaction, if any of the data nodes transferred is rejected for any reasons, the entire iPATCH request MUST be rejected and the CoOL server MUST return an appropriate error response as defined in section 6.Example:In this example, a CoOL client performs the following operations:Set “/system/ntp/enabled” (SID 1751) to true.Remove the server “tac.nrc.ca” from the”/system/ntp/server” (SID 1752) list.Add the server “NTP Pool server 2” to the list “/system/ntp/server” (SID 1752).Set “/system/ntp/server/prefer” (SID 1756) to false for the server “tic.nrc.ca”.CoAP request:CoAP response:Protocol operations are defined using the YANG ‘rpc’ or YANG ‘action’ statements.To execute a protocol operation, the CoOL client sents a CoAP POST request to the URI of the targeted datastore.The payload of the POST request carries a CBOR array with up to two entries. The first entry carries the instance-identifier identifying the targeted protocol operation. The second entry carries the protocol operation input(s). Input(s) are present only if defined for the invoked protocol operation and used by the CoOL client. Input(s) are encoded using the rules defined for a YANG container, deltas are relative to the SID assigned to the protocol operation.On successful completion on the protocol operation, the CoOL server returns a CoAP response with the response code set to 2.05 (Content). When output parameters are returned by the CoOL server, these parameter(s) are carried in the CoAP response payload. Output(s) are encoded using the rules defined for a YANG container, deltas are relative to the SID assigned to the protocol operation.This example is based on the ‘activate-software-image’ RPC defined in , assuming that this RPC is assigned to SID 1932, leaf image-name to SID 1933 and leaf status to SID 1934. These SIDs are defined strictly for the purpose of this example.rpc activate-software-image {
input {
leaf image-name {
type string;
}
}
output {
leaf status {
type string;
}
}
}CoAP request:CoAP response:This example is based on the ‘reset’ action defined in assuming that this action is assigned to SID 1902, leaf reset-at to SID 1903 and leaf reset-finished-at to SID 1904. These SIDs are defined strictly for the purpose of this example.list server {
key name;
leaf name {
type string;
}
action reset {
input {
leaf reset-at {
type yang:date-and-time;
mandatory true;
}
}
output {
leaf reset-finished-at {
type yang:date-and-time;
mandatory true;
}
}
}
}CoAP request:CoAP response:Notifications are defined using the YANG ‘notification’ statement. Subscriptions to an event stream and notification reporting are performed using an event stream resource. When multiple event stream resources are supported, the list of notifications associated with each stream is either pre-defined or configured in the CoOL server. CoOL clients MAY subscribe to one or more event stream resources.To subscribe to an event stream resource, a CoOL client MUST send a CoAP GET with the Observe CoAP option set to 0. To unsubscribe, a CoOL client MAY send a CoAP reset or a CoAP GET with the Observe option set to 1. For more information on the observe mechanism, see .Each notification transferred by a CoOL server to each of the registered CoOL clients is carried in a CoAP response with a response code set to 2.05 (Content). Each CoAP response MUST carry in its payload at least one notification but MAY carry multiple. Each notification is carried in a notification-payload defined in ietf-cool, see . The notification-payload supports different meta-data associated to this notification, such as the notification identifier, event timestamp, sequence number, severity level and facility. All of these meta information are optional with the exception of the notification identifier.The CoAP response payload is encoded using the rules defined for the PUT request. When multiple notifications are reported, the CoAP response payload carries a CBOR array, with each entry containing a notification.This example is based on the ‘link-failure’ and ‘interface-enabled’ notifications defined in assuming the following SID assignment:“/link-failure” (SID 1942)“/link-failure/if-name” (SID 1943)“/link-failure/admin-status” (SID 1944)“/interfaces/interface/interface-enabled” (SID 1538)“/interfaces/interface/interface-enabled/by-user” (SID 1539)These SIDs are defined strictly for the purpose of this example.In this example, a CoOL client starts by registering to the default event stream resource “/c/e”.CoAP request:The CoOL server confirms this registration by returning a first CoAP response. The payload of this CoAP response may be empty or may carry the last notification reported by this server.CoAP response:After detecting an event, the CoOL server sends its first notification to the registered CoOL client.CoAP response:To optimize communications or because of other constraints, the CoOL server might transfer multiple notifications in a single CoAP response.CoAP response:When performing a GET, the normal behaviour of a CoOL server is to exclude from the GET response, data nodes currently set to their default values as defined by the YANG ‘default’ statement. This behaviour called ‘trim’ is defined in section 3.2.This rule also applies to the FETCH for containers and list instances but not for the root data nodes. To minimize the payload size of the FETCH responses, root data nodes are returned in a CBOR array without associated SID. To keep the symmetry between the FETCH request and the FETCH response, a CBOR content must be returned for each data node requested as follows:a CBOR simple type ‘default’ is returned for each data node currently set to its default valuea CBOR simple type ‘undefined value’ is returned for each data node not instantiated or not supportedotherwise, the value is encoded based on the rules defined in There are use-cases when a CoOL client will need the default data from the server, for example:The management application often needs a single, definitive, and complete set of configuration values that determine how the networking device works.Documentation about default values can be 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 consultation of the documentation.In all these cases, the CoOL client will need a mechanism to retrieve default data from a CoOL server.This is accomplished by including the ‘a’ Uri-Query parameter in the GET or FETCH request. This behaviour called ‘report-all’ is defined in section 3.1.Supported Uri-Query parameters are defined in . Uri-Host, Uri-Port and Uri-Path MUST be used as specified by to target the CoOL resources as defined by section 3.This version of CoOL doesn’t support the creation of resources (datastore or event stream). For this reason, the use of Location-Path and Location-Query is not required.This option is not required since this protocol don’t support multiple choices of Content-Format.This option MUST be supported as specified by .This option MUST be supported as specified by .This option MUST be supported as specified by . Each ETag is associated to all schema nodes within a datastore.When the UDP transport is used and a large payload need to be transferred, support of the CoAP block transfer as defined by is recommended.A CoOL server MAY support state change notifications to some or all its leaf data nodes. When supported the CoOL server MUST implement the Server-Side requirements defined in section 3 and the CoOL client MUST implement the Client-Side requirements defined in section 4.To start observing a leaf data node, a CoOL client MUST send a CoAP FETCH with the Observe CoAP option set to 0.The payload of the FETCH request carries a CBOR array of instance-identifier.
The first entry MUST be set to the ‘instance-identifier’ of the data node instance observed. The following entries are optional and allow the selection of coincidental values, data nodes reported at the same time as the observed data node. Coincidental values are included in each notification reported, but changes to these extra data nodes MUST not trigger notification messages.A subscription can be terminated by the CoOL client by returning a CoAP Reset message or by sending a GET request with an Observe CoAP option set to deregister (1). More details are available in .Example:In this example, a CoOL client subscribes to state changes of the data node “/system/ntp/enabled” (SID = 1751) and requests that data node “/system/hostname” (SID 1748) is reported as coincidental value.A first response is immediately returned by the CoOL server to confirm the subscription and to report the current values of the requested data nodes.Subsequent responses are returned by the CoOL server each time the state of data node “/system/ntp/enabled” changes.CoAP request:CoAP response:CoAP response:The “/.well-known/core” resource is used by CoOL clients to discover resources implemented by CoOL servers. Each CoOL server MUST have an entry in the “/.well-known/core” resource for each datastore resource and event stream resource supported.Resource discovery can be performed using a CoAP GET request. If successful, the CoAP response MUST have a response code set to 2.05 (Content), a Content-Format set to “application/link-format”, and a payload containing a list of web links.To enable discovery of specific resource types, the CoAP server MUST support the query string “rt”.Link format and the “/.well-known/core” resource are defined in .Example:CoAP request:CoAP response:;rt="cool.datastore",
;rt="cool.datastore",
;rt="cool.datastore",
;rt="cool.event-stream",
]]>In this example, a CoOL client retrieves the list of all resources available on a CoOL server.Alternatively, the CoOL client may query for a specific resource type. In this example, the CoOL client queries for resource type (rt) “cool.datastore”.CoAP request:CoAP response:;rt="cool.datastore",
]]>All CoAP response codes defined by MUST be accepted and processed accordingly by CoOL clients. Optionally, client errors (CoAP response codes 4.xx) or server errors (CoAP response codes 5.xx) MAY have a payload providing further information about the cause of the error. This payload contains the “error-payload” container (SID 1007) defined in the “ietf-cool” YANG module, see .Example:CoAP response:This application protocol relies on the lower layers to provide confidentiality, integrity, and availability. A typical approach to archive these requirements is to implement CoAP using the DTLS binding as defined in section 9. Other approaches are possible to fulfill these requirements, such as the use of a network layer security mechanism as discussed in or a link layer security mechanism for exchanges done within a single sub-network.In some applications, different access rights to objects (data nodes, protocol operations and notifications) need to be granted to different CoOL clients. Different solutions are possible, such as the implementation of Access Control Lists (ACL) using YANG module(s) or the use of an authorization certificate as defined in . These access control mechanisms need to be addressed in complementary specifications.The Security Considerations section of CoAP is especially relevant to this application protocol and should be reviewed carefully by implementers.This draft introduces the following CoAP Content-Formats. These entries need to be registered in the CoAP Content-Formats Registry as defined in section 12.3.First entry:Media type = application/cool-instance-id-listEncoding = CBORID = 61Reference = RFC XXXXSecond entry:Media type = application/cool-valueEncoding = CBORID = 62Reference = RFC XXXXThird entry:Media type = application/cool-value-listEncoding = CBORID = 63Reference = RFC XXXXFourth entry:Media type = application/cool-value-pairs+cborEncoding = CBORID = 64Reference = RFC XXXXRFC Ed.: update XXXX to the RFC number assigned to this draft, update the ID if different than the one allocated, remove this note.TO DO If this set of Content-Formats is accepted, requirements and description need to be added where appropriate.This draft introduces the following CBOR simple value. This entry needs to be registered in the Simple Values Registry as defined in section 7.1.Value = 19Semantics = Default valueReference = RFC XXXXRFC Ed.: update XXXX to the RFC number assigned to this draft, update the value if different than the one allocated, remove this note.This document have been largely inspired by the extensive works done by Andy Bierman and Peter van der Stok on . have also been a critical input to this work. The authors would like to thank the authors and contributors to these two drafts.The authors would also like to thank Carsten Bormann for his help during the development of this document and his useful comments during the review process.Block-wise transfers in CoAPCoAP is a RESTful transfer protocol for constrained nodes and networks. Basic CoAP messages work well for the small payloads we expect from temperature sensors, light switches, and similar building-automation devices. Occasionally, however, applications will need to transfer larger payloads -- for instance, for firmware updates. With HTTP, TCP does the grunt work of slicing large payloads up into multiple packets and ensuring that they all arrive and are handled in the right order. CoAP is based on datagram transports such as UDP or DTLS, which limits the maximum size of resource representations that can be transferred without too much fragmentation. Although UDP supports larger payloads through IP fragmentation, it is limited to 64 KiB and, more importantly, doesn't really work well for constrained applications and networks. Instead of relying on IP fragmentation, this specification extends basic CoAP with a pair of "Block" options, for transferring multiple blocks of information from a resource representation in multiple request-response pairs. In many important cases, the Block options enable a server to be truly stateless: the server can handle each block transfer separately, with no need for a connection setup or other server-side memory of previous block transfers. In summary, the Block options provide a minimal way to transfer larger representations in a block-wise fashion. A CoAP implementation that does not support these options generally is limited in the size of the representations that can be exchanged. There is therefore an expectation that the Block options are very widely implemented in CoAP implementations, which is why this specification is listed as "updating" RFC 7252.Patch and Fetch Methods for Constrained Application Protocol (CoAP)The existing Constrained Application Protocol (CoAP) methods only allow access to a complete resource. This does not permit applications to access parts of a resource. In case of resources with larger or complex data, or in situations where a resource continuity is required, replacing or requesting the whole resource is undesirable. Several applications using CoAP will need to perform partial resource accesses. Similar to HTTP, the existing Constrained Application Protocol (CoAP) GET method only allows the specification of a URI and request parameters in CoAP options, not the transfer of a request payload detailing the request. This leads to some applications to using POST where actually a cacheable, idempotent, safe request is desired. Again similar to HTTP, the existing Constrained Application Protocol (CoAP) PUT method only allows to replace a complete resource. This also leads applications to use POST where actually a cacheable, possibly idempotent request is desired. This specification adds new CoAP methods, FETCH, to perform the equivalent of a GET with a request body; and the twin methods PATCH and iPATCH, to modify parts of an existing CoAP resource.The YANG 1.1 Data Modeling LanguageYANG is a data modeling language used to model configuration data, state data, remote procedure calls, and notifications for network management protocols. This document describes the syntax and semantics of version 1.1 of the YANG language. YANG version 1.1 is a maintenance release of the YANG language, addressing ambiguities and defects in the original specification. There are a small number of backward incompatibilities from YANG version 1. This document also specifies the YANG mappings to the Network Configuration Protocol (NETCONF).Key words for use in RFCs to Indicate Requirement LevelsIn many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.With-defaults Capability for NETCONFThe Network Configuration Protocol (NETCONF) defines ways to read and edit configuration data from a NETCONF server. In some cases, part of this data may not be set by the NETCONF client, but rather a default value known to the server is used instead. In many situations the NETCONF client has a priori knowledge about default data, so the NETCONF server does not need to save it in a NETCONF configuration datastore or send it to the client in a retrieval operation reply. In other situations the NETCONF client will need this data from the server. Not all server implementations treat this default data the same way. This document defines a capability-based extension to the NETCONF protocol that allows the NETCONF client to identify how defaults are processed by the server, and also defines new mechanisms for client control of server processing of default data. [STANDARDS-TRACK]YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)YANG is a data modeling language used to model configuration and state data manipulated by the Network Configuration Protocol (NETCONF), NETCONF remote procedure calls, and NETCONF notifications. [STANDARDS-TRACK]Constrained RESTful Environments (CoRE) Link FormatThis specification defines Web Linking using a link format for use by constrained web servers to describe hosted resources, their attributes, and other relationships between links. Based on the HTTP Link Header field defined in RFC 5988, the Constrained RESTful Environments (CoRE) Link Format is carried as a payload and is assigned an Internet media type. "RESTful" refers to the Representational State Transfer (REST) architecture. A well-known URI is defined as a default entry point for requesting the links hosted by a server. [STANDARDS-TRACK]Concise Binary Object Representation (CBOR)The Concise Binary Object Representation (CBOR) is a data format whose design goals include the possibility of extremely small code size, fairly small message size, and extensibility without the need for version negotiation. These design goals make it different from earlier binary serializations such as ASN.1 and MessagePack.The Constrained Application Protocol (CoAP)The Constrained Application Protocol (CoAP) is a specialized web transfer protocol for use with constrained nodes and constrained (e.g., low-power, lossy) networks. The nodes often have 8-bit microcontrollers with small amounts of ROM and RAM, while constrained networks such as IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs) often have high packet error rates and a typical throughput of 10s of kbit/s. The protocol is designed for machine- to-machine (M2M) applications such as smart energy and building automation.CoAP provides a request/response interaction model between application endpoints, supports built-in discovery of services and resources, and includes key concepts of the Web such as URIs and Internet media types. CoAP is designed to easily interface with HTTP for integration with the Web while meeting specialized requirements such as multicast support, very low overhead, and simplicity for constrained environments.A YANG Data Model for System ManagementThis document defines a YANG data model for the configuration and identification of some common system properties within a device containing a Network Configuration Protocol (NETCONF) server. This document also includes data node definitions for system identification, time-of-day management, user management, DNS resolver configuration, and some protocol operations for system management.Observing Resources in the Constrained Application Protocol (CoAP)The Constrained Application Protocol (CoAP) is a RESTful application protocol for constrained nodes and networks. The state of a resource on a CoAP server can change over time. This document specifies a simple protocol extension for CoAP that enables CoAP clients to "observe" resources, i.e., to retrieve a representation of a resource and keep this representation updated by the server over a period of time. The protocol follows a best-effort approach for sending new representations to clients and provides eventual consistency between the state observed by each client and the actual resource state at the server.Structure Identifier (SID)Structured IDentifiers (SID) are used to identify different YANG items when encoded in CBOR. This document defines the registration and assignment processes of SIDs. To enable the implementation of these processes, this document also defines a file format used to persist and publish assigned SIDs.CBOR Encoding of Data Modeled with YANGThis document defines encoding rules for serializing configuration data, state data, RPC input and RPC output, Action input, Action output and notifications defined within YANG modules using the Concise Binary Object Representation (CBOR) [RFC7049].RESTCONF ProtocolThis document describes an HTTP-based protocol that provides a programmatic interface for accessing data defined in YANG, using the datastore concepts defined in NETCONF.Management of Networks with Constrained Devices: Problem Statement, Use Cases and RequirementsThis document provides a problem statement and discusses the use cases and requirements for the management of networks with constrained devices.CoAP (Constrained Application Protocol) over TCP, TLS, and WebSocketsThe Constrained Application Protocol (CoAP), although inspired by HTTP, was designed to use UDP instead of TCP. The message layer of the CoAP over UDP protocol includes support for reliable delivery, simple congestion control, and flow control. Some environments benefit from the availability of CoAP carried over reliable transports such as TCP or TLS. This document outlines the changes required to use CoAP over TCP, TLS, and WebSockets transports.Using CoAP with IPsecCoAP is a RESTful transfer protocol for constrained nodes and networks. Security for the protocol can be supplied in a number of ways. The mandatory-to-implement security mode for CoAP makes use of DTLS. Other applications may want to use IPsec. This document will discuss considerations for the use of IPsec with CoAP. It will be advanced on a timescale separate from the main CoAP specification, as most experience in securing CoAP so far has been made with DTLS. The current version of this specification is a placeholder, built out of text extracted from draft-ietf-core-coap-12. It is meant to pick up http://trac.tools.ietf.org/wg/core/trac/ticket/262 and provide a home for its considerations. It might be merged with other documents later.CoAP Management InterfaceThis document describes a network management interface for constrained devices, called CoMI. CoMI is an adaptation of the RESTCONF protocol for use in constrained devices and networks. The Constrained Application Protocol (CoAP) is used to access management data resources specified in YANG, or SMIv2 converted to YANG. CoMI use the YANG to CBOR mapping and encodes YANG names to reduce payload size. Note Discussion and suggestions for improvement are requested, and should be sent to core@ietf.org.An Internet Attribute Certificate Profile for AuthorizationThis specification defines a profile for the use of X.509 Attribute Certificates in Internet Protocols. Attribute certificates may be used in a wide range of applications and environments covering a broad spectrum of interoperability goals and a broader spectrum of operational and assurance requirements. The goal of this document is to establish a common baseline for generic applications requiring broad interoperability as well as limited special purpose requirements. The profile places emphasis on attribute certificate support for Internet electronic mail, IPsec, and WWW security applications. This document obsoletes RFC 3281. [STANDARDS-TRACK]A YANG Data Model for Interface ManagementThis document defines a YANG data model for the management of network interfaces. It is expected that interface-type-specific data models augment the generic interfaces data model defined in this document. The data model includes configuration data and state data (status information and counters for the collection of statistics).Terminology for Constrained-Node NetworksThe Internet Protocol Suite is increasingly used on small devices with severe constraints on power, memory, and processing resources, creating constrained-node networks. This document provides a number of basic terms that have been useful in the standardization work for constrained-node networks.Module containing the different definitions required by the CoOL protocol. file "ietf-cool@2016-01-01.yang"
module ietf-cool {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-cool";
prefix cool;
organization
"IETF Core Working Group";
contact
"Ana Minaburo
Abhinav Somaraju
Alexander Pelov
Michel Veillette
Randy Turner
";
description
"This module contains the different definitions required
by the CoOL protocol.";
revision 2016-01-01 {
description
"Initial revision.";
reference
"draft-veillette-core-cool";
}
// List of useful derived YANG data types for constrained devices
typedef sid {
type uint32;
description
"Structure Identifier value (SID).";
}
typedef utc-time {
type uint32;
description
"Unsigned 32-bit value representing the number of seconds
since 0 hours, 0 minutes, 0 seconds, on the 1st of January,
2000 UTC (Universal Coordinated Time).";
}
// Error payload
container error-payload {
presence "Defines the format of an error paylaod.";
description
"Optional payload of a client error (CoAP response 4.xx)
or server error (CoAP response 5.xx).";
leaf error-code {
type enumeration {
enum error {
value 1;
description "Unspecified error.";
}
enum malformed {
value 2;
description "Malformed CBOR payload.";
}
enum invalid {
value 3;
description "The value specified in the request can't be
apply to the target data node.";
}
enum doesNotExist {
value 4;
description "The target data node instance specified in
the request doesn't exist.";
}
enum alreadyExist {
value 5;
description "The target data node instance specified in
the request already exists.";
}
enum readOnly {
value 6;
description "Attempt to update a read-only data node.";
}
}
mandatory true;
description
"Error code.";
}
leaf error-text {
type string;
description "Textual descriptions of the error.";
}
}
// Notification payload
identity facility-type {
description
"A facility code is used to specify the type of process that
is logging the message. Notifications from different facilities
may be handled differently. Other YANG module may add new
facility type as needed.";
}
identity os {
base facility-type;
description
"Notification generated by the operating system.";
}
identity protocol-stack {
base facility-type;
description
"Notification generated by one of the layers of the IP protocol stack.";
}
identity security {
base facility-type;
description
"Security related notification.";
}
identity hardware-monitoring {
base facility-type;
description
"Hardware related notification.";
}
identity application {
base facility-type;
description
"Notification generated by an application process.";
}
container notification-payload {
presence "Defines the format of a notification paylaod.";
description
"Definition of the payload of a notification transfered using CoOL.";
leaf _id {
type instance-identifier;
mandatory true;
description
"Identifier associated to the notification reported.";
}
leaf timestamp {
type utc-time;
description
"Event timestamp. Support of this field is optional
since its not expected that all implementations have
implement a real time clock and if so, this clock is
available at all time.";
}
leaf sequence-number {
type uint32;
description
"Sequence number associated to each event created by CoOL
server within a specific event stream.";
}
leaf severity-level {
type enumeration {
enum emergency {
value 0;
description
"System is unusable.";
}
enum alert {
value 1;
description
"Should be corrected immediately.";
}
enum critical {
value 2;
description
"Critical conditions.";
}
enum error {
value 3;
description
"Error conditions.";
}
enum warning {
value 4;
description
"May indicate that an error will occur if action is
not taken.";
}
enum notice {
value 5;
description
"Events that are unusual, but not error conditions.";
}
enum informational {
value 6;
description
"Normal operational messages that require no action.";
}
enum debug {
value 7;
description
"Information useful to developers for debugging the
application.";
}
}
description
"Severity associated with this event.";
reference "RFC 5424";
}
leaf facility {
type identityref {
base facility-type;
}
description
"Type of process that is logging the message.";
reference "RFC 5424";
}
anydata content {
description
"Notification container as defined by the notification YANG
statement.";
}
}
rpc commit {
description
"Used to commit the changes present in a candidate datastore on
the runtime datastore specify by the URI used to execute this
operation.";
input {
leaf datastore {
type string;
description
"Path of the datastore resource used as the source of the
commit operation. When not present, the default candidate
datastore resource is used.";
}
leaf commit-date-time {
type utc-time;
description
"When specified, the commit operation is postponed at the
specified date and time. When not present, the commit is
performed on reception of this RPC. Supports of this feature
is optional.";
}
leaf confirm-timeout {
type string;
description
"When present, a confirming commit MUST be received within
this period after the start of the commit process.
A confirming commit is a commit RPC without the
confirm-timeout field presents. Supports of this feature
is optional.";
}
}
}
rpc cancel-commit {
description
"Cancels an ongoing scheduled or confirmed commit.";
}
}
]]>Following is the “.sid” file generated for the “ietf-cool” YANG module. See for more details on SID and “.sid” file.