CoRE Resource Directory
draft-shelby-core-resource-directory-03
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
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|
|---|---|---|---|
| Authors | Zach Shelby , Srdjan Krco | ||
| Last updated | 2012-05-17 | ||
| Replaced by | draft-ietf-core-resource-directory, RFC 9176 | ||
| RFC stream | (None) | ||
| Formats | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
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draft-shelby-core-resource-directory-03
CoRE Z. Shelby
Internet-Draft Sensinode
Intended status: Standards Track S. Krco
Expires: November 18, 2012 Ericsson
May 17, 2012
CoRE Resource Directory
draft-shelby-core-resource-directory-03
Abstract
In many M2M applications, 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. This document specifies the web
interfaces that a Resource Directory supports in order for web
servers to discover the RD and to register, maintain, lookup and
remove resources descriptions. Furthermore, new link attributes
useful in conjunction with an RD are defined.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 18, 2012.
Copyright Notice
Copyright (c) 2012 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
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Architecture and Use Cases . . . . . . . . . . . . . . . . . . 4
3.1. Use Case: Cellular M2M . . . . . . . . . . . . . . . . . . 5
3.2. Use Case: Home and Building Automation . . . . . . . . . . 6
4. Resource Directory Function Set . . . . . . . . . . . . . . . 6
4.1. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 6
4.2. Registration . . . . . . . . . . . . . . . . . . . . . . . 8
4.3. Update . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.4. Validation . . . . . . . . . . . . . . . . . . . . . . . . 12
4.5. Removal . . . . . . . . . . . . . . . . . . . . . . . . . 13
5. RD Lookup Function Set . . . . . . . . . . . . . . . . . . . . 14
6. New Link-Format Attributes . . . . . . . . . . . . . . . . . . 16
6.1. Export 'exp' attribute . . . . . . . . . . . . . . . . . . 16
7. Security Considerations . . . . . . . . . . . . . . . . . . . 17
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
10. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 17
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
11.1. Normative References . . . . . . . . . . . . . . . . . . . 18
11.2. Informative References . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
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1. Introduction
The Constrained RESTful Environments (CoRE) working group aims at
realizing the REST architecture in a suitable form for the most
constrained nodes (e.g. 8-bit microcontrollers with limited RAM and
ROM) and networks (e.g. 6LoWPAN). CoRE is aimed at machine-to-
machine (M2M) applications such as smart energy and building
automation.
The discovery of resources offered by a constrained server is very
important in machine-to-machine applications where there are no
humans in the loop and static interfaces result in fragility. The
discovery of resources provided by an HTTP Web Server is typically
called Web Linking [RFC5988]. The use of Web Linking for the
description and discovery of resources hosted by constrained web
servers is specified by the CoRE Link Format
[I-D.ietf-core-link-format]. This specification however only
describes how to discover resources from the web server that hosts
them by requesting /.well-known/core. 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.
This document specifies the web interfaces that a Resource Directory
supports in order for web servers to discover the RD and to
registrer, maintain, lookup and remove resources descriptions.
Furthermore, new link attributes useful in conjunction with a
Resource Directory are defined. Although the examples in this
document show the use of these interfaces with CoAP
[I-D.ietf-core-coap], they may be applied in an equivalent manner to
HTTP [RFC2616].
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 in [RFC2119].
This specification requires readers to be familiar with all the terms
and concepts that are discussed in [RFC5988] and
[I-D.ietf-core-link-format]. Readers should also be familiar with
the terms and concepts discussed in [I-D.ietf-core-coap]. The URI
Template format is used to describe the REST interfaces defined in
this specification [RFC6570]. This specification makes use of the
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following additional terminology:
Resource Directory
An web entity that stores information about web resources and
implements the REST interfaces defined in this specification for
registration and lookup of those resources.
Domain
In the context of a Resource Directory, a domain is a logical
grouping of end-points. All end-point within a domain MUST be
unique. This specification assumes that the list of domains
supported by an RD is pre-configured by that RD.
End-point
An end-point (EP) is a term used to describe a web server or
client in [I-D.ietf-core-coap]. In the context of this
specificaiton an end-point is used to describe a web server that
registers resources to the Resource Directory. An end-point is
identified by its end-point name, which is included during
registration, and MUST be unique within the associated domain of
the registration.
3. Architecture and Use Cases
The resource directory architecture is shown in Figure 1. A Resource
Directory (RD) is used as a repository for Web Links [RFC5988] about
resources hosted on other web servers, which are called end-points
(EP). An end-point is a web server associated with a port, thus a
physical node may host one or more end-points. The RD implements a
set of REST interfaces for end-points to register and maintain sets
of Web Links (called resource directory entries), for the RD to
validate entries, and for clients to lookup resources from the RD.
End-points themselves can also act as clients. An RD can be
logically segmented by the use of Domains. The domain an end-point
is associated with can be defined by the RD or configured by an
outside entity.
End-points are assumed to proactively register and maintain resource
directory entries on the RD, which are soft state and need to be
periodially refreshed. An EP is provided with interfaces to
register, update and remove a resource directory entry. Furthermore,
a mechanism to discover a RD using the CoRE Link Format is defined.
It is also possible for an RD to proactively discover Web Links from
EPs and add them as resource directory entries, or to validate
existing resource directory entries. A lookup interface for
discovering any of the Web Links held in the RD is provided using the
CoRE Link Format.
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Registration Lookup
+----+ | |
| EP |---- | |
+----+ ---- | |
--|- +------+ |
+----+ | ----| | | +--------+
| EP | ---------|-----| RD |----|-----| Client |
+----+ | ----| | | +--------+
--|- +------+ |
+----+ ---- | |
| EP |---- | |
+----+
Figure 1: The resource directory architecture.
3.1. Use Case: Cellular M2M
Over the last few years, mobile operators around the world have
focused on development of M2M solutions in order to expand the
business to the new type of users, i.e. machines. The machines are
connected directly to a mobile network using appropriate embedded air
interface (GSM/GPRS, WCDMA, LTE) or via a gateway providing short and
wide range wireless interfaces. From the system design point of
view, the ambition is to design horizontal solutions that can enable
utilization of machines in different applications depending on their
current availability and capabilities as well as application
requirements, thus avoiding silo like solutions. One of the crucial
enablers of such design is the ability to discover resources
(machines - End Points) capable of providing required information at
a given time or acting on instructions from the end users.
In a typical scenario, during a boot-up procedure (and periodically
afterwards), the machines (EPs) register with a Resource Directory
(for example EPs installed on vehicles enabling tracking of their
position for the fleet management purposes and monitoring environment
parameters) hosted by the mobile operator or somewhere else in the
network, submiting a description of own capabilities. Due to the
usual network configuration of mobile networks, the EPs attached to
the mobile network do not have routable addresses. Therefore, a
remote server is usually used to provide proxy access to the EPs.
The address of each (proxy) EP on this server is included in the
resource description stored in the RD. The users, for example mobile
applications for environment monitoring, contact the RD, look-up the
EPs capable of providing information about the environment using
appropriate set of tags, obtain information on how to contact them
(URLs of the proxy server) and then initate interaction to obtain
information that is finally processed, displayed on the screen and
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usually stored in a database. Similarly, fleet management systems
provide a set of credentials along with the appropriate tags to the
RD to look-up for EPs deployed on the vehicles the application is
responsible for.
3.2. Use Case: Home and Building Automation
Home and commercial building automation systems can benefit from the
use of M2M web services. The use of CoRE in home automation across
multiple subnets is described in [I-D.brandt-coap-subnet-discovery]
and in commercial building automation in [I-D.vanderstok-core-bc].
The discovery requirements of these applications are demanding. Home
automation usually relies on run-time discovery to commision the
system, whereas in building automation a combination of professional
commissioning and run-time discovery is used. Both home and building
automation involve peer-to-peer interactions between end-points, and
involve battery-powered sleeping devices.
The exporting of resource information to other discovery systems is
also important in these automation applications. In home automation
there is a need to interact with other consumer electronics, which
may already support DNS-SD, and in building automation larger
resource directories or DNS-SD covering multiple buildings.
4. Resource Directory Function Set
This section defines the REST interfaces between an RD and end-point
servers, which is called the Resource Directory Function Set.
Although the examples throughout this section assume use of CoAP
[I-D.ietf-core-coap], these REST interfaces can also be realized
using HTTP [RFC2616]. An RD implementing this specification MUST
support the discovery, registration, update, and removal interfaces
defined in this section and MAY support the validation interface.
For the purpose of validation, an end-point implementing this
specification SHOULD support Etag validation on /.well-known/core.
4.1. Discovery
Before an end-point can make use of an RD, it must first know its IP
address, port and the path of its RD Function Set. There can be
several mechanisms for discovering the RD including assuming a
default location (e.g. on an Edge Router in a LoWPAN), by assigning
an anycast address to the RD, using DHCP, or by discovering the RD
using the CoRE Link Format. This section defines discovery of the RD
using the well-known interface of the CoRE Link Format
[I-D.ietf-core-link-format] as the required mechanism. It is however
expected that RDs will also be discoverable via other methods
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depending on the deployment.
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. Likewise, a Resource Type parameter value of "core.rd-
lookup" is used to discover the RD Lookup Function Set. 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.
When performing multicast discovery, the multicast IP address used
will depend on the scope required and the multicast capabilities of
the network.
An implementation of this specification MUST support query filtering
for the rt parameter as defined in [I-D.ietf-core-link-format].
The discovery interface is specified as follows:
Interaction: EP -> RD
Method: GET
URI Template: /.well-known/core{?rt}
URI Template Variables:
rt := Resource Type (optional). MAY contain the value
"core.rd", "core.rd-lookup" or "core.rd*"
Content-Type: application/link-format (if any)
Success: 2.05 "Content" with an application/link-format payload
containing a matching entry for the RD resource.
Failure: 4.04 "Not Found" is returned in case no matching entry is
found for a unicast request.
Failure: No error response to a multicast request.
Failure: 4.00 "Bad Request"
The following example shows an end-point discovering an RD using this
interface, thus learning that the base RD resource is at /rd. Note
that it is up to the RD to choose its base RD resource, although it
is recommended to use default locations where possible.
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End-point RD
| |
| ----- GET /.well-known/core?rt=core.rd* ------> |
| |
| |
| <---- 2.05 Content "</rd>; rt="core.rd" ------ |
| |
Req: GET coap://[ff02::1]/.well-known/core?rt=core.rd*
Res: 2.05 Content
</rd>;rt="core.rd",
</rd-lookup>;rt="core.rd-lookup"
4.2. Registration
After discovering the location of an RD Function Set, an end-point
MAY register its resources using the 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, its domain and the lifetime of the
registration. All parameters except the end-point name are optional.
The RD then creates a new resource or updates an existing resource in
the RD and returns its location. An end-point MUST use that location
when refreshing registrations using this interface. End-point
resources in the RD are kept active for the period indicated by the
lifetime parameter. The end-point is responsible for refreshing the
entry within this period using either the registration or update
interface. The registration interface MUST be implemented to be
idempotent, so that registering twice with the same end-point
parameter does not create multiple RD entries.
The registration interface is specified as follows:
Interaction: EP -> RD
Method: POST
URI Template: /{+rd}{?ep,d,rt,lt,con}
URI Template Variables:
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rd := RD Function Set path (mandatory). This is the path of the
RD Function Set. An RD SHOULD use the value "rd" for this
variable whenever possible.
ep := End-point (mandatory). The end-point identifier or name
of the registering node, unique within that domain. The
maximum length of this parameter is 63 octets.
d := Domain (optional). The domain to which this end-point
belongs. The maximum length of this parameter is 63 octets.
Optional. When this parameter is elided, the RD MAY associate
the end-point with a configured default domain.
rt := End-point Type (optional). The semantic type of the end-
point. The maximum length of this parameter is 63 octets.
Optional.
lt := Lifetime (optional). Lifetime of the registration in
seconds. Range of 60-4294967295. If no lifetime is included,
a default value of 86400 (24 hours) SHOULD be assumed.
con := Context (optional). This parameter sets the scheme,
address and port at which this server is available in the form
scheme://host:port. Optional. In the absence of this
parameter the scheme of the protocol, source IP address and
source port used to register are assumed.
Content-Type: application/link-format
Etag: The Etag option MAY be included to allow an RD to perform
validation in the future.
Success: 2.01 "Created". The Location header MUST be included with
the new resource entry for the end-point. This Location MUST be a
stable identifier generated by the RD as it is used for all
subsequent operations on this registration (update, delete).
Failure: 4.00 "Bad Request". Malformed request.
Failure: 5.03 "Service Unavailable". Service could not perform the
operation.
The following example shows an end-point with the name "node1"
registering two resources to an RD using this interface. The
resulting location /rd/4521 is just an example of an RD generated
location.
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End-point RD
| |
| --- POST /rd?ep=node1 "</sensors..." -------> |
| |
| |
| <-- 2.01 Created Location: /rd/4521 ---------- |
| |
Req: POST coap://rd.example.com/rd?ep=node1
Etag: 0x3f
Payload:
</sensors/temp>;ct=41;rt="TemperatureC";if="sensor",
</sensors/light>;ct=41;rt="LightLux";if="sensor"
Res: 2.01 Created
Location: /rd/4521
4.3. Update
The update interface is used by an end-point to refresh or update its
registration with an RD. To use the interface, the end-point sends a
PUT request to the resource returned in the Location option in the
response to the first registration. An update MAY contain
registration parameters or a payload in CoRE Link Format if there
have been changes since the last registration or update. Paremeters
that have not changed SHOULD NOT be included in an update.
The update interface is specified as follows:
Interaction: EP -> RD
Method: PUT
URI Template: /{+location}{?rt,lt,con}
URI Template Variables:
location := This is the Location path returned by the RD as a
result of a successful registration.
rt := End-point Type (optional). The semantic type of the end-
point. The maximum length of this parameter is 63 octets.
Optional.
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lt := Lifetime (optional). Lifetime of the registration in
seconds. Range of 60-4294967295. If no lifetime is included,
a default value of 86400 (24 hours) SHOULD be assumed.
con := Context (optional). This parameter sets the scheme,
address and port at which this server is available in the form
scheme://host:port. Optional. In the absence of this
parameter the scheme of the protocol, source IP address and
source port used to register are assumed.
Content-Type: application/link-format (if any)
Etag: The Etag option MAY be included to allow an RD to compare the
existing entry and perform validation in the future.
Success: 2.04 "Changed" in case the resource and/or lifetime was
successfully updated
Failure: 4.00 "Bad Request". Malformed request.
Failure: 5.03 "Service Unavailable". Service could not perform the
operation.
The following example shows an end-point updating a new set of
resources to an RD using this interface.
End-point RD
| |
| --- PUT /rd/4521 "</sensors..." ------------> |
| |
| |
| <-- 2.04 Changed ---------------------------- |
| |
Req: PUT /rd/4521
Etag: 0x40
Payload:
</sensors/temp/1>;ct=41;ins="Indoor";rt="TemperatureC";if="sensor",
</sensors/temp/2>;ct=41;ins="Outdoor";rt="TemperatureC";if="sensor",
</sensors/light>;ct=41;rt="LightLux";if="sensor"
Res: 2.04 Changed
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4.4. Validation
In some cases, an RD may want to validate that it has the latest
version of an end-point's resources. This can be performed with a
GET on the well-known interface of the CoRE Link Format including the
latest Etag stored for that end-point. For the purpose of
validation, an end-point implementing this specification SHOULD
support Etag validation on /.well-known/core.
The validation interface is specified as follows:
Interaction: RD -> EP
Method: GET
Path: /.well-known/core
Parameters: None
Content-Type: application/link-format (if any)
Etag: The Etag option MUST be included
Success: 2.03 "Valid" in case the Etag matches
Success: 2.05 "Content" in case the Etag does not match, the
response MUST include the most recent resource representation and
its corresponding Etag.
Failure: 4.00 "Bad Request". Malformed request.
The following examples shows a successful validation.
End-point RD
| |
| <--- GET /.well-known/core Etag: 0x40 -------- |
| |
| |
| --- 2.03 Valid -----------------------------> |
| |
Req: GET /.well-known/core
Etag: 0x40
Res: 2.03 Valid
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4.5. Removal
Although RD entries have soft state and will eventually timeout after
their lifetime, an end-point SHOULD explicitly remove its entry from
the RD if it knows it will no longer be available (for example on
shut-down). This is accomplished using a removal interface on the RD
by performing a DELETE on the end-point resource.
The removal interface is specified as follows:
Interaction: EP -> RD
Method: DELETE
URI Template: /{+location}
URI Template Variables:
location := This is the Location path returned by the RD as a
result of a successful registration.
Content-Type: None
Success: 2.02 "Deleted" upon successful deletion
Failure: 4.00 "Bad Request". Malformed request.
Failure: 5.03 "Service Unavailable". Service could not perform the
operation.
The following examples shows successful removal of the end-point from
the RD.
End-point RD
| |
| --- DELETE /rd/4521 ------------------------> |
| |
| |
| <-- 2.02 Deleted ---------------------------- |
| |
Req: DELETE /rd/4521
Res: 2.02 Deleted
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5. RD Lookup Function Set
In order for an RD to be used for discovering resources registered
with it, a lookup interface can be provided using this function set.
This lookup interface is defined as a default, and it is assumed that
RDs may also support lookups to return resource descriptions in
alternative formats (e.g. Atom or HTML Link) or using more advanced
interfaces (e.g. supporting context or semantic based lookup).
This function set allows lookups for domains, end-points and
resources using attributes defined in the RD Function Set and for use
with the CoRE Link Format. The result of a lookup request is the
list of links (if any) in CoRE Link Format corresponding to the type
of lookup. The target of these links SHOULD be the actual location
of the domain, end-point or resource, but MAY be an intermediate
proxy e.g. in the case of an HTTP lookup interface for CoAP end-
points.
The lookup interface is specified as follows:
Interaction: Client -> RD
Method: GET
URI Template: /{+rd-lookup-base}/{lookup-type}{?d,ep,resource-param}
Parameters:
rd-lookup-base := RD Lookup Function Set path (mandatory). This
is the path of the RD Lookup Function Set. An RD SHOULD use the
value "rd-lookup" for this variable whenever possible.
lookup-type := ("d", "ep", "res") (mandatory) This variable is
used to select the kind of lookup to perform (domain, end-point
or resource).
ep := End-point (optional). Used for end-point and resource
lookups.
d := Domain (optional). Used for domain, end-point and resource
lookups.
rt := End-point type (optional). Used for end-point lookups.
resource-param := Link attribute parameters (optional). Any
link attribute as defined in Section 4.1 of
[I-D.ietf-core-link-format], used for resource lookups.
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Content-Type: application/link-format (if any)
Success: 2.05 "Content" with an application/link-format payload
containing a matching entries for the lookup.
Failure: 4.04 "Not Found" in case no matching entry is found for a
unicast request.
Failure: No error response to a multicast request.
Failure: 4.00 "Bad Request". Malformed request.
Failure: 5.03 "Service Unavailable". Service could not perform the
operation.
The following example shows a client performing a resource lookup:
Client RD
| |
| ----- GET /rd-lookup/res?rt=Temperature -----------------> |
| |
| |
| <-- 2.05 Content "<coap://node1/temp>;rt="Temperature" ---- |
| |
Req: GET /rd-lookup/res?rt=Temperature
Res: 2.05 Content
<coap://{ip:port}/temp>;rt="Temperature"
The following example shows a client performing an end-point lookup:
Client RD
| |
| ----- GET /rd-lookup/ep?rt=PowerNode --------------------> |
| |
| |
| <-- 2.05 Content "<coap://{ip:port}>;ep="node5" ----------- |
| |
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Req: GET /rd-lookup/ep?rt=PowerNode
Res: 2.05 Content
<coap://{ip:port}>;ep="node5"
<coap://{ip:port}>;ep="node7"
The following example shows a client performing a domain lookup:
Client RD
| |
| ----- GET /rd-lookup/domain -----------------------------> |
| |
| |
| <-- 2.05 Content "</rd>;d=domain1,</rd>;d=domain2 --------- |
| |
Req: GET /rd-lookup/domain
Res: 2.05 Content
</rd>;d=domain1,
</rd>;d=domain2
6. New Link-Format Attributes
When using the CoRE Link Format to describe resources being
discovered by or posted to a resource directory service, additional
information about those resources is useful. This specification
defines the following new attributes for use in the CoRE Link Format
[I-D.ietf-core-link-format]:
link-extension = ( "exp" )
6.1. Export 'exp' attribute
The Export "exp" attribute is used as a flag to indicate that a link
description MAY be exported by a resource directory to external
directories.
The CoRE Link Format is used for many purposes between CoAP end-
points. Some are useful mainly locally, for example checking the
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observability of a resource before accessing it, determining the size
of a resource, or traversing dynamic resource structures. However,
other links are very useful to be exported to other directories, for
example the entry point resource to a functional service.
7. Security Considerations
This document needs the same security considerations as described in
Section 7 of [RFC5988] and Section 6 of [I-D.ietf-core-link-format].
The /.well-known/core resource may be protected e.g. using DTLS when
hosted on a CoAP server as described in [I-D.ietf-core-coap].
Access control SHOULD be performed separately for the RD Function Set
and the RD Lookup Function Set independently, as different end-points
may be authorized to register with an RD from those authorized to
lookup end-points from the RD. Such access control SHOULD be
performed in as fine-grained a level as possible. For example access
control for lookups could be performed either at the domain, end-
point or resource level.
8. IANA Considerations
"core.rd" and "core.rd-lookup" resource type needs to be registered
when the appropriate registry is created by
[I-D.ietf-core-link-format].
The "exp" attribute needs to be registered when a future Web Linking
attribute is created.
9. Acknowledgments
Szymon Sasin, Carsten Bormann, Kerry Lynn, Peter van der Stok, Anders
Brandt, Matthieu Vial, Sampo Ukkola and Linyi Tian have provided
helpful comments, discussions and ideas to improve and shape this
document. The authors would also like to thank their collagues from
the EU FP7 SENSEI project, where many of the resource directory
concepts were originally developed.
10. Changelog
Changes from -02 to -03:
o Changed the end-point name back to a single registration
parameter ep= and removed the h= and ins= parameters.
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o Updated REST interface descriptions to use RFC6570 URI Template
format.
o Introduced an improved RD Lookup design as its own function set.
o Improved the security considerations section.
o Made the POST registration interface idempotent by requiring the
ep= paramter to be present.
Changes from -01 to -02:
o Added a terminology section.
o Changed the inclusing of an Etag in registration or update to a
MAY.
o Added the concept of an RD domain and a registration parameter
for it.
o Recommended the Location returned from a registration to be
stable, allowing for end-point and domain information to be
changed during updates.
o Changed the lookup interface to accept end-point and domain as
query string parameters to control the scope of a lookup.
11. References
11.1. Normative References
[I-D.ietf-core-link-format]
Shelby, Z., "CoRE Link Format",
draft-ietf-core-link-format-06 (work in progress),
June 2011.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5988] Nottingham, M., "Web Linking", RFC 5988, October 2010.
[RFC6570] Gregorio, J., Fielding, R., Hadley, M., Nottingham, M.,
and D. Orchard, "URI Template", RFC 6570, March 2012.
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11.2. Informative References
[I-D.brandt-coap-subnet-discovery]
Brandt, A., "Discovery of CoAP servers across subnets",
draft-brandt-coap-subnet-discovery-00 (work in progress),
March 2011.
[I-D.ietf-core-coap]
Shelby, Z., Hartke, K., Bormann, C., and B. Frank,
"Constrained Application Protocol (CoAP)",
draft-ietf-core-coap-06 (work in progress), May 2011.
[I-D.vanderstok-core-bc]
Stok, P. and K. Lynn, "CoAP Utilization for Building
Control", draft-vanderstok-core-bc-03 (work in progress),
March 2011.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
Authors' Addresses
Zach Shelby
Sensinode
Kidekuja 2
Vuokatti 88600
FINLAND
Phone: +358407796297
Email: zach@sensinode.com
Srdjan Krco
Ericsson
Phone:
Email: srdjan.krco@ericsson.com
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