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Internet Engineering Task Force (IETF)                        J. JimenezRequest for Comments: 7650                                      EricssonCategory: Standards Track                                  J. Lopez-VegaISSN: 2070-1721                                    University of Granada                                                              J. Maenpaa                                                            G. Camarillo                                                                Ericsson                                                          September 2015A Constrained Application Protocol (CoAP) Usagefor REsource LOcation And Discovery (RELOAD)Abstract   This document defines a Constrained Application Protocol (CoAP) Usage   for REsource LOcation And Discovery (RELOAD).  The CoAP Usage   provides the functionality to federate Wireless Sensor Networks   (WSNs) in a peer-to-peer fashion.  The CoAP Usage for RELOAD allows   CoAP nodes to store resources in a RELOAD peer-to-peer overlay,   provides a lookup service, and enables the use of RELOAD overlay as a   cache for sensor data.  This functionality is implemented in the   RELOAD overlay itself, without the use of centralized servers.  The   RELOAD AppAttach method is used to establish a direct connection   between nodes through which CoAP messages are exchanged.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc7650.Jimenez, et al.              Standards Track                    [Page 1]

RFC 7650                 A CoAP Usage for RELOAD          September 2015Copyright Notice   Copyright (c) 2015 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   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 Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .32.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .53.  Architecture  . . . . . . . . . . . . . . . . . . . . . . . .54.  Registering CoAP URIs . . . . . . . . . . . . . . . . . . . .75.  Lookup  . . . . . . . . . . . . . . . . . . . . . . . . . . .86.  Forming a Direct Connection and Reading Data  . . . . . . . .97.  Caching Mechanisms  . . . . . . . . . . . . . . . . . . . . .117.1.  ProxyCache  . . . . . . . . . . . . . . . . . . . . . . .117.2.  SensorCache . . . . . . . . . . . . . . . . . . . . . . .138.  CoAP Usage Kinds Definition . . . . . . . . . . . . . . . . .148.1.  CoAP-REGISTRATION Kind  . . . . . . . . . . . . . . . . .148.2.  CoAP-CACHING Kind . . . . . . . . . . . . . . . . . . . .159.  Access Control Rules  . . . . . . . . . . . . . . . . . . . .1510. Security Considerations . . . . . . . . . . . . . . . . . . .1611. IANA Considerations . . . . . . . . . . . . . . . . . . . . .1711.1.  CoAP-REGISTRATION Kind-ID  . . . . . . . . . . . . . . .1711.2.  CoAP-CACHING Kind-ID . . . . . . . . . . . . . . . . . .1711.3.  Access Control Policies  . . . . . . . . . . . . . . . .1712. References  . . . . . . . . . . . . . . . . . . . . . . . . .1812.1.  Normative References . . . . . . . . . . . . . . . . . .1812.2.  Informative References . . . . . . . . . . . . . . . . .18   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .19Jimenez, et al.              Standards Track                    [Page 2]

RFC 7650                 A CoAP Usage for RELOAD          September 20151.  Introduction   The Constrained Application Protocol (CoAP) Usage for REsource   LOcation And Discovery (RELOAD) allows CoAP nodes to store resources   in a RELOAD peer-to-peer overlay, provides a lookup service, and   enables the use of RELOAD overlay as a cache for sensor data.  This   functionality is implemented in the RELOAD overlay itself, without   the use of centralized servers.   This usage is intended for interconnected devices over a wide-area   geographical coverage, such as in cases where multiple Wireless   Sensor Networks (WSNs) need to be federated over some wider-area   network.  These WSNs would interconnect by means of nodes that are   equipped with long range modules (e.g., 2G, 3G, 4G) as well as short   range ones (e.g., XBee, ZigBee, Bluetooth LE).   Constrained devices are likely to be heterogeneous when it comes to   their radio layer; however, we expect them to use a common   application-layer protocol -- CoAP, which is a specialized web   transfer protocol [RFC7252].  It realizes the Representational State   Transfer (REST) architecture for the most constrained nodes, such as   sensors and actuators.  CoAP can be used not only between nodes on   the same constrained network but also between constrained nodes and   nodes on the Internet.  The latter is possible since CoAP can be   translated to Hypertext Transfer Protocol (HTTP) for integration with   the web.  Application areas of CoAP include different forms of   machine-to-machine (M2M) communication, such as home automation,   construction, health care or transportation.  Areas with heavy use of   sensor and actuator devices that monitor and interact with the   surrounding environment.   As specified in [RFC6940], RELOAD is fundamentally an overlay   network.  It provides a layered architecture with pluggable   application layers that can use the underlaying forwarding, storage,   and lookup functionalities.  Figure 1 illustrates where the CoAP   Usage is placed within the RELOAD architecture.Jimenez, et al.              Standards Track                    [Page 3]

RFC 7650                 A CoAP Usage for RELOAD          September 2015       Application           +-------+           | CoAP  |   ...           | Usage |           +-------+       ------------------------------------ Messaging Service       +------------------+     +---------+       |     Message      |<--->| Storage |       |    Transport     |     +---------+       +------------------+           ^              ^       ^               |              |       v               v              |     +-------------------+              |     |    Topology       |              |     |    Plug-in        |              |     +-------------------+              |         ^              v         v           +------------------+           |  Forwarding &    |           | Link Management  |           +------------------+       ------------------------------------ Overlay Link Service            +-------+  +-------+            |TLS    |  |DTLS   |  ...            |Overlay|  |Overlay|            |Link   |  |Link   |            +-------+  +-------+                          Figure 1: Architecture   The CoAP Usage involves three basic functions:   Registration: CoAP nodes that can use the RELOAD data storage   functionality, can store a mapping from their CoAP URI to their Node-   ID in the overlay.  They can also retrieve the Node-IDs of other   nodes.  Nodes that are not RELOAD aware can use other mechanisms, for   example [CORERESDIR] in their local network.   Lookup: Once a CoAP node has identified the Node-ID for an URI it   wishes to retrieve, it can use the RELOAD message routing system to   set up a connection that can be used to exchange CoAP messages.   Similarly as with the registration, nodes that are not RELOAD aware   can use CoAP messages with a RELOAD Node (RN) that will in turn   perform the lookup in the overlay.Jimenez, et al.              Standards Track                    [Page 4]

RFC 7650                 A CoAP Usage for RELOAD          September 2015   Caching: Nodes can use the RELOAD overlay as a caching mechanism for   information about what CoAP resources are available on the node.   This is especially useful for power-constrained nodes that can make   their data available in the cache provided by the overlay while in   sleep mode.   For instance, a CoAP proxy (SeeSection 3) could register its Node-ID   (e.g. "9996172") and a list of sensors (e.g. "/sensors/temp-1;   /sensors/temp-2; /sensors/light, /sensors/humidity") under its URI   (e.g. "coap://overlay-1.com/proxy-1/").   When a node wants to discover the values associated with that URI, it   queries the overlay for "coap://overlay-1.com/proxy-1/" and gets back   the Node-ID of the proxy and the list of its associated sensors.  The   requesting node can then use the RELOAD overlay to establish a direct   connection with the proxy and to read sensor values.   Moreover, the CoAP proxy can store the sensor information in the   overlay.  In this way, information can be retrieved directly from the   overlay without performing a direct connection to the storing proxy.2.  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 inRFC 2119 [RFC2119].   We use the terminology and definitions from the RELOAD Base Protocol   [RFC6940] extensively in this document.  Some of those concepts are   further described in the "Concepts and Terminology for Peer to Peer   SIP" [P2PSIP] document.3.  Architecture   In our architecture we extend the different nodes present in RELOAD   (Peer, Client) and add support for sensor devices or other   constrained devices.  Figure 2 illustrates the overlay topology.  The   different nodes, according to their functionality, are:   Client      As specified in [RFC6940], clients are nodes that do not have      routing or storage responsibilities in the Overlay.   Peer      As specified in [RFC6940], peers are nodes in the overlay that can      route messages for nodes other than those to which it is directly      connected.Jimenez, et al.              Standards Track                    [Page 5]

RFC 7650                 A CoAP Usage for RELOAD          September 2015   Sensor      Devices capable of measuring a physical quantity.  Sensors usually      acquire quantifiable information about their surrounding      environment such as: temperature, humidity, electric current,      moisture, radiation, and so on.   Actuator      Devices capable of interacting and affecting their environment      such as: electrical motors, pneumatic actuators, electric      switches, and so on.   Proxy Node      Devices having sufficient resources to run RELOAD either as client      or peer.  These devices are located at the edge of the sensor      network and, in case of Wireless Sensor Networks (WSN), act as      coordinators of the network.   Physical devices can have one or several of the previous functional   roles.  According to the functionalities that are present in each of   the nodes, they can be:   Constrained Node      A Constrained Node (CN) is a node with limited computational      capabilities.  CN devices belong to classes of at least C1 and C2      devices as defined in [RFC7228], their main constraint being the      implementation of the CoAP protocol.  If the CN is wireless, then      it will be part of a Low-Rate Wireless Personal Area Network      (LR-WPAN), also termed Low-Power and Lossy Network (LLN).  Lastly,      devices will usually be in sleep mode in order to prevent battery      drain, and will not communicate during those periods.  A CN is NOT      part of the RELOAD overlay, therefore it cannot act as a client,      peer, nor proxy.  A CN is always either a Sensor or an Actuator.      In the latter case, the node is often connected to a continuous      energy power supply.   RELOAD Node      A RELOAD Node (RN) MUST implement the client functionality in the      Overlay.  Additionally, the node will often be a full RELOAD peer.      An RN may also be sensor or actuator since it can have those      devices connected to it.   Proxy Node      A Proxy Node (PN) MUST implement the RN functionality and act as a      sink for the LR-WPAN network.  The PN connects the short range      Wireless Network to the Wide Area Network or the Internet.  A      Proxy Node fulfills the "Proxy Node" role as described previously      in the Architecture.Jimenez, et al.              Standards Track                    [Page 6]

RFC 7650                 A CoAP Usage for RELOAD          September 2015                  +------+                  |      |         +--------+  RN  +---------+         |        |      |         |     +---+--+     +------+      +--+---+     |      |                   |      |     |  RN  |                   |  RN  |     |      |                   |      |   +------------+     +---+--+                   +--+---+   |        WSN |         |         RELOAD          |       |     +----+ |         |         OVERLAY         |       | +---+ CN | |     +---+--+                   +--+---+   | |   +----+ |     |      |                   |      +-----+          |     |  RN  |                   |  PN  |   |            |     |      |                   |      +-----+          |     +---+--+     +------+      +--+---+   | |   +----+ |         |        |      |         |       | +---+ CN | |         +--------+  PN  +---------+       |     +----+ |                  |      |                 +------------+                  +-+--+-+                    |  |           +--------|--|--------+           |     +--+  +--+     |           |     |        |     |           |  +--+-+    +-+--+  |           |  | CN |    | CN |  |           |  +----+    +----+  |           |                WSN |           +--------------------+                        Figure 2: Overlay Topology4.  Registering CoAP URIs   CoAP URIs are typically resolved using a DNS.  When CoAP is needed in   a RELOAD environment, URI resolution is provided by the overlay as a   whole.  Instead of registering a URI, a peer stores a   CoAPRegistration structure under a hash of its own URI.  This uses   the CoAP REGISTRATION Kind-ID, which is formally defined inSection 8.1 and uses a DICTIONARY data model.   In this example, a CoAP proxy that is located in an overlay   overlay-1.com using a Node-ID "9996172" wants to register four   different sensors to the URI "coap://overlay-1.com/proxy-1/.well-   known/".  We will be using the link format specified in [RFC6690] to   store the following mapping in the overlay:Jimenez, et al.              Standards Track                    [Page 7]

RFC 7650                 A CoAP Usage for RELOAD          September 2015    Resource-ID = h(coap://overlay-1.com/proxy-1/.well-known/)    KEY =  9996172,    VALUE = [     </sensors/temp-1>;rt="temperature-c";if="sensor",     </sensors/temp-2>;rt="temperature-c";if="sensor",     </sensors/light>;rt="light-lux";if="sensor",     </sensors/humidity>;rt="humidity-p";if="sensor"        ]   Note that the Resource-ID stored in the overlay is calculated as hash   over the URI, that is -- h(URI), which in RELOAD is usually SHA-1.   This would inform any other node performing a lookup for the previous   URI "coap://overlay-1.com/proxy-1/.well-known" that the Node-ID value   for proxy-1 is "9996172".  In addition, this mapping provides   relevant information as to the number of sensors (CNs) and the URI   path to connect to them using CoAP.5.  Lookup   The RELOAD overlay supports a rendezvous system that can be used for   the lookup of other CoAP nodes.  This is done by fetching mapping   information between CoAP URIs and Node-IDs.   As an example, if a node RN located in the overlay overlay-1.com   wishes to read which resources are served at an RN with URI   coap://overlay-1.com/proxy-1/, it performs a fetch in the overlay.   The Resource-ID used in this fetch is a SHA-1 hash over the URI   "coap://overlay-1.com/proxy-1/.well-known/".   After this fetch request, the overlay will return the following   result:    Resource-ID = h(coap://overlay-1.com/proxy-1/.well-known/)    KEY =  9996172,    VALUE = [     </sensors/temp-1>;rt="temperature-c";if="sensor",     </sensors/temp-2>;rt="temperature-c";if="sensor",     </sensors/light>;rt="light-lux";if="sensor",     </sensors/humidity>;rt="humidity-p";if="sensor"     ]   The obtained KEY is the Node-ID of the RN responsible of this KEY/   VALUE pair.  The VALUE is the set of URIs necessary to read data from   the CNs associated with the RN.Jimenez, et al.              Standards Track                    [Page 8]

RFC 7650                 A CoAP Usage for RELOAD          September 2015   Using the RELOAD DICTIONARY model allows for multiple nodes to   perform a store to the same Resource-ID.  This can be used, for   example, to perform a store of resources of the same type or with   similar characteristics.  After performing a lookup, this feature   allows the fetching of those multiple RNs that host CNs of the same   class.   As an example, provided that the previous peer (9996172) and another   peer (9996173) have stored the links to their respective temperature   resources in this same Resource-ID (temperature), an RN (e.g.,   node-A) can do a fetch to the URI "coap://overlay-1.com/   temperature/.well-known/", obtaining the following results:    Resource-ID = h(coap://overlay-1.com/temperature/.well-known/)    KEY =  9996172,    VALUE = [     </sensors/temp-1>;rt="temperature-c";if="sensor",     </sensors/temp-2>;rt="temperature-c";if="sensor",      ]    KEY = 9996173,    VALUE = [     </sensors/temp-a>;rt="temperature-c";if="sensor",           </sensors/temp-b>;rt="temperature-c";if="sensor"      ]6.  Forming a Direct Connection and Reading Data   Once an RN (e.g., node-A) has obtained the lookup information for a   node in the overlay (e.g., proxy-1), it can directly connect to that   node.  This is performed by sending an AppAttach request to the   Node-ID obtained during the lookup process.   After the AppAttach negotiation, node-A can access the values of the   CNs at proxy-1 using the information obtained during the lookup.   Following the example inSection 5, and according to [RFC6690], the   requests for accessing the CNs at proxy-1 would be:    REQ: GET /sensors/temp-1    REQ: GET /sensors/temp-2Jimenez, et al.              Standards Track                    [Page 9]

RFC 7650                 A CoAP Usage for RELOAD          September 2015   Figure 3 shows a sample of a node reading temperature data.   +-----+     +---------+    +-----+          +---+   | PNA |     | OVERLAY |    | PNB |          |CNB|   +-----+     +---------+    +-----+          +---+      |             |            |                |      |             |            |                |      | 1.RELOAD    |            |                |      | FetchReq    |            |                |      |+----------->|            |                |      |             |            |                |      | 2.RELOAD    |            |                |      | FetchAns    |            |                |      |<-----------+|            |                |      |             |            |                |      | 3.RELOAD    |            |                |      |  AppAttach  |            |                |      |+----------->|            |                |      |             | 4.RELOAD   |                |      |             | AppAttach  |                |      |             |+---------->|                |      |             |            |                |      |             | 5.RELOAD   |                |      | 6.RELOAD    |AppAttachAns|                |      |AppAttachAns |<----------+|                |      |<-----------+|            |                |      |             |            |                |      |                          |                |      |   ---------------------  |                |      | /        7.ICE          \|                |      | \   connectivity checks /|                |      |   ---------------------  |                |      |                          |                |      |      8.CoAP CON          |                |      |    GET /sensors/temp-1   |                |      |+------------------------>|                |      |                          |  9.CoAP  GET   |      |                          |/sensors/temp-1 |      |                          |+-------------->|      |                          | 10.CoAP        |      |     11.CoAP              |    ACK 200     |      |        ACK 200           |<--------------+|      |<------------------------+|                |      |                          |                |                Figure 3: An Example of a Message SequenceJimenez, et al.              Standards Track                   [Page 10]

RFC 7650                 A CoAP Usage for RELOAD          September 20157.  Caching Mechanisms   The CoAP protocol itself supports the caching of sensor information   in order to reduce the response time and network bandwidth   consumption of future, equivalent requests.  CoAP caching is   specified inSection 5 of [RFC7252].  It consists of reusing stored   responses when new requests arrive.  This type of storage is done in   CoAP proxies.   This CoAP usage for RELOAD proposes an additional caching mechanism   for storing sensor information directly in the overlay.  In order to   do so, it is necessary to define how the data should be stored.  Such   caching mechanism is primarily intended for CNs with sensor   capabilities, not for RN sensors.  This is due to the battery   constraints of CNs, forcing them to stay in sleep mode for long   periods of time.   Whenever a CN wakes up, it sends the most recent data from its   sensors to its proxy (PN), which stores the data in the overlay using   a RELOAD StoredData structure defined inSection 6 of [RFC6940].  We   use the StoredDataValue structure defined inSection 6.2 of   [RFC6940], in particular we use the SingleValue format type to store   the cached values in the overlay.  From that structure length,   storage_time, lifetime and Signature are used in the same way.  The   only difference is DataValue, which in our case can be either a   ProxyCache or a SensorCache:   enum { reserved (0), proxy_cache(1), sensor_cache(2), (255) }                CoAPCachingType;   struct {    CoAPCachingType coap_caching_type;    select(coap_caching_type) {     case proxy_cache: ProxyCache proxy_cache_entry;     case sensor_cache: SensorCache sensor_cache_entry;     /* extensions */    }   } CoAPCaching;7.1.  ProxyCache   ProxyCache is meant to store values and sensor information (e.g.,   inactivity time) for all the sensors associated with a certain proxy,   as well as their CoAP URIs.  SensorCache, on the other hand, is used   for storing the information and cached value of only one sensor (CoAP   URI is not necessary, as it is the same as the one used for   generating the Resource-ID associated to that SensorCache entry).Jimenez, et al.              Standards Track                   [Page 11]

RFC 7650                 A CoAP Usage for RELOAD          September 2015   ProxyCache contains the Node-ID, length, and a series of SensorEntry   types.   struct {    Node-ID  Node_ID;    uint32   length;    SensorEntry sensors[count];   } ProxyCache;   Node-ID      The Node-ID of the Proxy Node (PN) responsible for different      sensor devices;   length      The length of the rest of the structure;   Sensor-Entry      List of sensors in the form of SensorEntry types;   SensorEntry contains the coap_uri, sensor_info, and a series of   SensorValue types.   struct {    opaque  coap_uri;    SensorInfo  sensor_info;    uint32  length;    SensorValue sensor_value[count];   } SensorEntry;   coap_uri      CoAP name of the sensor device in question;   sensor_info      contains relevant sensor information;   length      The length of the rest of the structure;   sensor_value      contains a list of values stored by the sensor;Jimenez, et al.              Standards Track                   [Page 12]

RFC 7650                 A CoAP Usage for RELOAD          September 20157.2.  SensorCache   SensorCache: contains the information related to one sensor.   struct {    Node-ID  Node_ID;    SensorInfo sensor_info;    uint32  length;    SensorValue sensor_value[count];   } SensorCache;   Node_ID      identifies the Node-ID of the Proxy Node responsible for the      sensor;   sensor_info      contains relevant sensor information;   length      The length of the rest of the structure;   sensor_value      contains a list of values stored by the sensor;   SensorInfo contains relevant sensor information that is dependent on   the use case.  As an example, we use the sensor manufacturer as   relevant information.   struct {    opaque  dev_info;    /* extensions */   } SensorInfo;   dev_info      Contains specific device information as defined in [RFC6690] --      for example, temperature, luminosity, etc.  It can also represent      other semantic information about the device.   SensorValue contains the measurement_time, lifetime, and value of the   measurement.Jimenez, et al.              Standards Track                   [Page 13]

RFC 7650                 A CoAP Usage for RELOAD          September 2015   struct {    uint32  measurement_time;    uint32  lifetime;    opaque  value;    /* extensions */   } SensorValue;   measurement_time      indicates the moment when the measure was taken, represented as      the number of milliseconds elapsed since midnight Jan 1, 1970 UTC      not counting leap seconds.   lifetime      indicates the validity time of that measured value in milliseconds      since measurement_time.   value      indicates the actual value measured.  It can be of different types      (integer, long, string); therefore, opaque has been used.8.  CoAP Usage Kinds Definition   This section defines the CoAP-REGISTRATION and CoAP-CACHING Kinds.8.1.  CoAP-REGISTRATION Kind   Kind-IDs      The Resource Name for the CoAP-REGISTRATION Kind-ID is the CoAP      URI.  The data stored is a CoAPRegistration, which contains a set      of CoAP URIs.   Data Model      The data model for the CoAP-REGISTRATION Kind-ID is dictionary.      The dictionary key is the Node-ID of the storing RN.  This allows      each RN to store a single mapping.   Access Control      URI-NODE-MATCH.  The "coap:" prefix needs to be removed from the      COAP URI before matching.Jimenez, et al.              Standards Track                   [Page 14]

RFC 7650                 A CoAP Usage for RELOAD          September 2015   Data stored under the COAP-REGISTRATION Kind is of type   CoAPRegistration, defined below.   struct {    Node-ID Node_ID;    uint16 coap_uris_length;    opaque coap_uris (0..2^16-1);   } CoAPRegistration;8.2.  CoAP-CACHING Kind   Kind-IDs      The Resource Name for the CoAP-CACHING Kind-ID is the CoAP URI.      The data stored is a CoAPCaching, which contains a cached value.   Data Model      The data model for the CoAP-CACHING Kind-ID is single value.   Access Control      URI-MATCH.  The "coap:" prefix needs to be removed from the COAP      URI before matching.   Data stored under the CoAP-CACHING Kind is of type CoAPCaching,   defined inSection 7.9.  Access Control Rules   As specified in RELOAD Base [RFC6940], every Kind that is storable in   an overlay must be associated with an access control policy.  This   policy defines whether a request from a given node to operate on a   given value should succeed or fail.  Usages can define any access   control rules they choose, including publicly writable values.   CoAP Usage for RELOAD requires an access control policy that allows   multiple nodes in the overlay read and write access.  This access is   for registering and caching information using CoAP URIs as   identifiers.  Therefore, none of the access control policies   specified in RELOAD Base [RFC6940] are sufficient.   This document defines two access control policies, called URI-MATCH   and URI-NODE-MATCH.  In the URI-MATCH policy, a given value MUST be   written and overwritten if and only if the signer's certificate   contains an uniformResourceIdentifier entry in the subjectAltName   Extension [RFC5280] that in canonicalized form hashes to the   Resource-ID for the resource.  As explained inSection 6.3 of   [RFC7252] the "coap" and "coaps" schemes conform to the generic URI,   thus they are normalized in the generic form as explained inJimenez, et al.              Standards Track                   [Page 15]

RFC 7650                 A CoAP Usage for RELOAD          September 2015Section 6 of [RFC3986].  The hash function used is specified inSection 10.2 of [RFC6940].  The certificate can be generated as   specified inSection 9 of [RFC7252], using Certificate mode.   In the URI-NODE-MATCH policy, a given value MUST be written and   overwritten if and only if the condition for URI-MATCH is met and, in   addition, the dictionary key is equal to the Node-ID in the   certificate and that Node-ID is the one indicated in the   SignerIdentity value cert_hash.   These Access Control Policies are specified for IANA inSection 11.3.10.  Security Considerations   The security considerations of RELOAD [RFC6940] and CoAP [RFC7252]   apply to this specification.  RELOAD's security model is based on   public key certificates, which are used for signing messages and   stored objects.  At the connection level, RELOAD can use either TLS   or DTLS.  In the case of CoAP, several security modes have been   defined.  Implementations of this specification MUST follow all the   security-related rules specified in the RELOAD [RFC6940] and CoAP   [RFC7252] specifications.   Additionally, in RELOAD every Kind that is storable in an overlay   must be associated with an access control policy.  This document   specifies two new access control policies, which are specified inSection 9.  These policies cover the most typical deployment   scenarios.   During the phase of registration and lookup, security considerations   relevant to RELOAD apply.  A CoAP node that advertises its existence   via this mechanism, is more likely to be attacked, compared to a node   (especially a sleepy node) that does not advertise its existence.Section 11 of [RFC7252] andSection 13 of [RFC6940] have more   information about the kinds of attack and mitigation possible.   The caching mechanism specified in this document is additional to the   caching already done in CoAP.  Access control is handled by the   RELOAD overlay, where the peer storing the data is responsible for   validating the signature on the data being stored.Jimenez, et al.              Standards Track                   [Page 16]

RFC 7650                 A CoAP Usage for RELOAD          September 201511.  IANA Considerations11.1.  CoAP-REGISTRATION Kind-ID   This document introduces a data Kind-ID to the "RELOAD Data Kind-ID"   registry:       +-------------------+------------+----------+       | Kind              |    Kind-ID |      RFC |       +-------------------+------------+----------+       | CoAP-REGISTRATION |      0x105 |RFC 7650 |       +-------------------+------------+----------+   This Kind-ID was defined inSection 8.1.11.2.  CoAP-CACHING Kind-ID   This document introduces another data Kind-ID to the "RELOAD Data   Kind-ID" registry:       +--------------+------------+----------+       | Kind         |    Kind-ID |      RFC |       +--------------+------------+----------+       | CoAP-CACHING |      0x106 |RFC 7650 |       +--------------+------------+----------+   This Kind-ID was defined inSection 8.2.11.3.  Access Control Policies   IANA has created a "CoAP Usage for RELOAD Access Control Policy"   registry.  This registry has been added to the existing RELOAD   registry.  Entries in this registry are strings denoting access   control policies, as described inSection 9.  New entries in this   registry are to be registered per the Specification Required policy   in [RFC5226].  The initial contents of this registry are:       +-----------------+----------+       | Access Policy   |      RFC |       +-----------------+----------+       | URI-NODE-MATCH  |RFC 7650 |       | URI-MATCH       |RFC 7650 |       +-----------------+----------+   This access control policy was described inSection 9.Jimenez, et al.              Standards Track                   [Page 17]

RFC 7650                 A CoAP Usage for RELOAD          September 201512.  References12.1.  Normative References   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119,              DOI 10.17487/RFC2119, March 1997,              <http://www.rfc-editor.org/info/rfc2119>.   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform              Resource Identifier (URI): Generic Syntax", STD 66,RFC 3986, DOI 10.17487/RFC3986, January 2005,              <http://www.rfc-editor.org/info/rfc3986>.   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,              Housley, R., and W. Polk, "Internet X.509 Public Key              Infrastructure Certificate and Certificate Revocation List              (CRL) Profile",RFC 5280, DOI 10.17487/RFC5280, May 2008,              <http://www.rfc-editor.org/info/rfc5280>.   [RFC6690]  Shelby, Z., "Constrained RESTful Environments (CoRE) Link              Format",RFC 6690, DOI 10.17487/RFC6690, August 2012,              <http://www.rfc-editor.org/info/rfc6690>.   [RFC6940]  Jennings, C., Lowekamp, B., Ed., Rescorla, E., Baset, S.,              and H. Schulzrinne, "REsource LOcation And Discovery              (RELOAD) Base Protocol",RFC 6940, DOI 10.17487/RFC6940,              January 2014, <http://www.rfc-editor.org/info/rfc6940>.   [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained              Application Protocol (CoAP)",RFC 7252,              DOI 10.17487/RFC7252, June 2014,              <http://www.rfc-editor.org/info/rfc7252>.12.2.  Informative References   [CORERESDIR]              Shelby, Z., Koster, M., Bormann, C., and P. Stok, "CoRE              Resource Directory", Work in Progress,draft-ietf-core-resource-directory-04, July 2015.   [P2PSIP]   Bryan, D., Matthews, P., Shim, E., Willis, D., and S.              Dawkins, "Concepts and Terminology for Peer to Peer SIP",              Work in Progress,draft-ietf-p2psip-concepts-07, May 2015.Jimenez, et al.              Standards Track                   [Page 18]

RFC 7650                 A CoAP Usage for RELOAD          September 2015   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an              IANA Considerations Section in RFCs",BCP 26,RFC 5226,              DOI 10.17487/RFC5226, May 2008,              <http://www.rfc-editor.org/info/rfc5226>.   [RFC7228]  Bormann, C., Ersue, M., and A. Keranen, "Terminology for              Constrained-Node Networks",RFC 7228,              DOI 10.17487/RFC7228, May 2014,              <http://www.rfc-editor.org/info/rfc7228>.Authors' Addresses   Jaime Jimenez   Ericsson   Hirsalantie 11   Jorvas  02420   Finland   Email: jaime.jimenez@ericsson.com   Jose M. Lopez-Vega   University of Granada   CITIC UGR Periodista Rafael Gomez Montero 2   Granada  18071   Spain   Email: jmlvega@ugr.es   Jouni Maenpaa   Ericsson   Hirsalantie 11   Jorvas  02420   Finland   Email: jouni.maenpaa@ericsson.com   Gonzalo Camarillo   Ericsson   Hirsalantie 11   Jorvas  02420   Finland   Email: gonzalo.camarillo@ericsson.comJimenez, et al.              Standards Track                   [Page 19]

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