Network Working Group X. He Internet-Draft YC.Ma Intended status: Informational Hitachi (China) Research and Expires: April 24, 2012 Development Corporation Z.Cao China Mobile October 22, 2011 Energy Aware Proxy Discovery for CoAP draft-he-core-energy-aware-pd-00.txt Abstract CoRE defines a mechanism for resource discovery based on Web linking with discovery, registration,modification, and other procedures. But energy efficiency is very important for resource constrained devices. This specification shows an efficient method for CoAP proxy finding the resource from end-points by reducing multicast messages. The current version -00 of this document is just an initial draft that is intended to spark discussion. Status of This Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on April 11, 2012. Copyright Notice He, et al. Expires April 11, 2012 [Page 1] Internet-Draft Proxy Discovery for CoAP Oct 2011 Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents 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 BSD License. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Resource discovery analysis. . . . . . . . . . . . . . . . . . 4 3. Energy aware proxy discovery . . . . . . . . . . . . . . . . . 5 3.1. Reduced Protocol Operations . . . . . . . . . . . . . . . 5 3.2. Example . . . . . . . . . . . . . . . . . . 6 4. IANA Consideration . . . . . . . . . . . . . . . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 6. Normative References . . . . . . . . . . . . . . . . . . . . . .7 He, et al. Expires April 11, 2012 [Page 2] Internet-Draft Proxy Discovery for CoAP Oct 2011 1. Introduction The Constrained RESTful Environments (CoRE) working group aims at realizing the REST architecture in a suitable form for the most constrained nodes and networks. CoRE is aimed at machine-to-machine (M2M) applications such as smart energy and building automation [I-D.shelby-core-coap-req]. As being the main work of CORE,CoAP defined a proxy mechanism for CoAP end-point, that proxy can be tasked by CoAP clients to perform requests on their behalf [I-D.ietf-core-coap]. Since in many M2M scenarios, direct discovery of resources is not practical due to sleeping nodes, disperse networks, or networks where multicast traffic is inefficient. These problems can be solved by employing an entity called a Resource Directory (RD), which hosts descriptions of resources held on other servers, allowing lookups to be performed for those resources[I-D.shelby-core-resource-directory]. The proxy mechanism should support this RD function in resource constrained environments. There are several methods to discovery proxy by a CoAP end-point, including assuming a default location (e.g. on an Edge Router in a LoWPAN), by assigning an anycast address to the proxy, using DHCP, or using the CoRE Link Format. While reducing energy consumption is essential for battery operated nodes in some devices, which is one of the most important work in M2M communication. Node's energy usage depends on network messages it has to receive and or respond. Thus the discovery procedure should be optimized with energy aware consideration. 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 RFC 2119 [RFC2119]. He, et al. Expires April 11, 2012 [Page 3] Internet-Draft Proxy Discovery for CoAP Oct 2011 2. Resource discovery analysis As mentioned in other drafts, resource discovery is performed by sending either a multicast or unicast GET request to /.well-known/core and including a Resource Type (rt) parameter [I-D.ietf-core-link-format] with the value "core-rd" in the query string. Upon success, the response will contain a payload with a link format entry for each RD discovered, with the URL indicating the root resource of the RD. After discovering the location of an RD, an end-point MAY register its resources to the RD's registration interface. This interface accepts a POST from an end-point containing the list of resources to be added to the directory as the message payload in the CoRE Link Format along with query string parameters indicating the name of the end-point, an optional node identifier and the lifetime of the registration. Upon success, the response will be 2.01 "Created" [I-D.shelby-core-resource-directory]. That means once resource discovery needs twice communication process between end-point and proxy. For energy saving point of view, this procedure should be optimized. Another draft indicates more efficient method.A CoAP server that wants to make itself discoverable sends a POST request to the default discovery URI of any Candidate CoAP Server Discovery Server [I-D.bormann-core-simple-server-discovery]. This draft shows more details about energy aware proxy discovery mechanism for CoAP. He, et al. Expires April 11, 2012 [Page 4] Internet-Draft Proxy Discovery for CoAP Oct 2011 3. Energy aware proxy discovery 3.1. Reduced Protocol Operations The Energy aware proxy reduces discovery and registration processes into one. The end-point acting as a server will use server IP address, the CoAP default port[I-D.ietf-core-coap], and the absolute path "/.well-known/core"[I-D.ietf-core-link-format] to build its POST request. And this request will be send to its Neighbor by unicast (as using 6LOWPAN or IPv6) or to a multicast address. The POST request is a link-format message, which indicates the service list that requesting server wants to make known to the proxy. End-point resources in the proxy are kept active for the period also indicated by the lifetime parameter. But unless the end-point needs to refreshing the data with update message, the data will be kept in this lifetime. Then the data will be delete automatically as expired. The discovery interface is specified as follows: Interaction: EP -> Proxy Path: /.well-known/core Method: POST Content-Type: application/link-format Parameters: Lifetime (lt): Lifetime of the registration in seconds. Range of 60-4294967295. If no lifetime is included, the response will be Failure: 4.00 "Bad Request" . Host (h): The host identifier or name of the registering node. The maximum length of this parameter is 63 octets. This parameter is combined with the Instance parameter (if any) to form the end-point name. If not included, the proxy MUST generate a unique Host name on behalf of the node. Instance (ins): The instance of the end-point on this host, if there are multiple. The maximum length of this parameter is 63 octets. Type (rt): The semantic type of end-point. The maximum length of this parameter is 63 octets. He, et al. Expires April 11, 2012 [Page 5] Internet-Draft Proxy Discovery for CoAP Oct 2011 Success: 2.01 "Created". The Location header of the new resource entry for the end-point could be e.g. in the form /{rd-base}/ {end-point name} Failure: 4.00 "Bad Request". Malformed request. Failure: 5.03 "Service Unavailable". Service could not perform the operation. 3.2 Example The following example shows an end-point with the name "node1" POST temperature resource to a proxy using this interface. End-point Neighbor | (as a proxy) | --- POST /.well-known/core?rt=core-rd-------> | | | | | | <-- 2.01 Created Location: /rd/node1 --------- | | | Req: POST coap://[ff02::1]/.well-known/core?rt=core-rd Payload: ;ct=41;rt="TemperatureC";if="sensor", Res: 2.01 Created Location: /rd/node1 4. Security Considerations TBD. 5. IANA Considerations This document does not require any IANA actions. He, et al. Expires April 11, 2012 [Page 6] Internet-Draft Proxy Discovery for CoAP Oct 2011 6. Normative References [I-D.shelby-core-coap-req] Shelby, Z., Stuber, M., Sturek, D., Frank, B., and R. Kelsey, "CoAP Requirements and Features", draft-shelby-core-coap-req-01 (work in progress), April 2010. [I-D.ietf-core-coap] Shelby, Z., Hartke, K., Bormann, C., and B. Frank, "Constrained Application Protocol (CoAP)", draft-ietf-core-coap-06 , May 2011. [I-D.ietf-core-link-format] Shelby, Z., "CoRE Link Format", draft-ietf-core-link-format-07,July 2011. [I-D.bormann-core-simple-server-discovery] Bormann, C.,"CoRE Simple Server Discovery" draft-bormann-core-simple-server-discovery-00, June, 2011 [I-D.shelby-core-resource-directory] Shelby, Z.,Krco, S., "CoRE Resource Directory" draft-shelby-core-resource-directory-01, September, 2011 Authors' Addresses Xuan He Yuanchen Ma Hitachi R&D China 301 of North Tower C, Raycom @ Kexuyuan Nanlu, Haidian District Beijing 100190 China Email: xhe@hitachi.cn ycma@hitachi.cn Zhen Cao China Mobile Unit2, 28 Xuanwumenxi Ave,Xuanwu District Beijing 100053 China Email: zehn.cao@gmail.com He, et al. Expires April 11, 2012 [Page 7]