< draft-ietf-core-resource-directory-01.txt   draft-ietf-core-resource-directory-02.txt >
CoRE Z. Shelby CoRE Z. Shelby
Internet-Draft ARM Internet-Draft ARM
Intended status: Standards Track C. Bormann Intended status: Standards Track C. Bormann
Expires: June 14, 2014 Universitaet Bremen TZI Expires: May 13, 2015 Universitaet Bremen TZI
S. Krco November 9, 2014
Ericsson
December 11, 2013
CoRE Resource Directory CoRE Resource Directory
draft-ietf-core-resource-directory-01 draft-ietf-core-resource-directory-02
Abstract Abstract
In many M2M applications, direct discovery of resources is not In many M2M applications, direct discovery of resources is not
practical due to sleeping nodes, disperse networks, or networks where practical due to sleeping nodes, disperse networks, or networks where
multicast traffic is inefficient. These problems can be solved by multicast traffic is inefficient. These problems can be solved by
employing an entity called a Resource Directory (RD), which hosts employing an entity called a Resource Directory (RD), which hosts
descriptions of resources held on other servers, allowing lookups to descriptions of resources held on other servers, allowing lookups to
be performed for those resources. This document specifies the web be performed for those resources. This document specifies the web
interfaces that a Resource Directory supports in order for web interfaces that a Resource Directory supports in order for web
skipping to change at page 1, line 42 skipping to change at page 1, line 40
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This Internet-Draft will expire on June 14, 2014. This Internet-Draft will expire on May 13, 2015.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Architecture and Use Cases . . . . . . . . . . . . . . . . . . 4 3. Architecture and Use Cases . . . . . . . . . . . . . . . . . . 5
3.1. Use Case: Cellular M2M . . . . . . . . . . . . . . . . . . 5 3.1. Use Case: Cellular M2M . . . . . . . . . . . . . . . . . . 7
3.2. Use Case: Home and Building Automation . . . . . . . . . . 6 3.2. Use Case: Home and Building Automation . . . . . . . . . . 7
4. Simple Directory Discovery . . . . . . . . . . . . . . . . . . 6 3.3. Use Case: Link Catalogues . . . . . . . . . . . . . . . . 8
4.1. Finding a Directory Server . . . . . . . . . . . . . . . . 7 4. Simple Directory Discovery . . . . . . . . . . . . . . . . . . 8
5. Resource Directory Function Set . . . . . . . . . . . . . . . 8 4.1. Finding a Directory Server . . . . . . . . . . . . . . . . 10
5.1. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 8 4.2. Third-party registration . . . . . . . . . . . . . . . . . 10
5.2. Registration . . . . . . . . . . . . . . . . . . . . . . . 10 5. Resource Directory Function Set . . . . . . . . . . . . . . . 10
5.3. Update . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.1. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 11
5.4. Removal . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.2. Registration . . . . . . . . . . . . . . . . . . . . . . . 13
6. Group Function Set . . . . . . . . . . . . . . . . . . . . . . 15 5.3. Update . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.1. Register a Group . . . . . . . . . . . . . . . . . . . . . 15 5.4. Removal . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.2. Group Removal . . . . . . . . . . . . . . . . . . . . . . 17 6. Group Function Set . . . . . . . . . . . . . . . . . . . . . . 18
7. RD Lookup Function Set . . . . . . . . . . . . . . . . . . . . 18 6.1. Register a Group . . . . . . . . . . . . . . . . . . . . . 18
8. New Link-Format Attributes . . . . . . . . . . . . . . . . . . 22 6.2. Group Removal . . . . . . . . . . . . . . . . . . . . . . 20
8.1. Resource Instance 'ins' attribute . . . . . . . . . . . . 22 7. RD Lookup Function Set . . . . . . . . . . . . . . . . . . . . 21
8.2. Export 'exp' attribute . . . . . . . . . . . . . . . . . . 23 8. New Link-Format Attributes . . . . . . . . . . . . . . . . . . 25
9. DNS-SD Mapping . . . . . . . . . . . . . . . . . . . . . . . . 23 8.1. Resource Instance attribute 'ins' . . . . . . . . . . . . 25
10. Security Considerations . . . . . . . . . . . . . . . . . . . 23 8.2. Export attribute 'exp' . . . . . . . . . . . . . . . . . . 26
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 9. DNS-SD Mapping . . . . . . . . . . . . . . . . . . . . . . . . 26
11.1. Resource Types . . . . . . . . . . . . . . . . . . . . . . 23 9.1. DNS-based Service discovery . . . . . . . . . . . . . . . 26
11.2. Link Extension . . . . . . . . . . . . . . . . . . . . . . 24 9.2. mapping ins to <Instance> . . . . . . . . . . . . . . . . 27
11.3. RD Parameter Registry . . . . . . . . . . . . . . . . . . 24 9.3. Mapping rt to <ServiceType> . . . . . . . . . . . . . . . 28
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 25 9.4. Domain mapping . . . . . . . . . . . . . . . . . . . . . . 28
13. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 25 9.5. TXT Record key=value strings . . . . . . . . . . . . . . . 28
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26 9.6. Importing resource links into DNS-SD . . . . . . . . . . . 29
14.1. Normative References . . . . . . . . . . . . . . . . . . . 26 10. Security Considerations . . . . . . . . . . . . . . . . . . . 30
14.2. Informative References . . . . . . . . . . . . . . . . . . 27 10.1. Endpoint Identification and Authentication . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 28 10.2. Access Control . . . . . . . . . . . . . . . . . . . . . . 30
10.3. Denial of Service Attacks . . . . . . . . . . . . . . . . 31
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31
11.1. Resource Types . . . . . . . . . . . . . . . . . . . . . . 31
11.2. Link Extension . . . . . . . . . . . . . . . . . . . . . . 31
11.3. RD Parameter Registry . . . . . . . . . . . . . . . . . . 32
12. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 33
14. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 33
15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 35
15.1. Normative References . . . . . . . . . . . . . . . . . . . 35
15.2. Informative References . . . . . . . . . . . . . . . . . . 36
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 36
1. Introduction 1. Introduction
The Constrained RESTful Environments (CoRE) work aims at realizing The work on Constrained RESTful Environments (CoRE) aims at realizing
the REST architecture in a suitable form for the most constrained the REST architecture in a suitable form for the most constrained
nodes (e.g. 8-bit microcontrollers with limited RAM and ROM) and nodes (e.g. 8-bit microcontrollers with limited RAM and ROM) and
networks (e.g. 6LoWPAN). CoRE is aimed at machine-to-machine (M2M) networks (e.g. 6LoWPAN). CoRE is aimed at machine-to-machine (M2M)
applications such as smart energy and building automation. applications such as smart energy and building automation.
The discovery of resources offered by a constrained server is very The discovery of resources offered by a constrained server is very
important in machine-to-machine applications where there are no important in machine-to-machine applications where there are no
humans in the loop and static interfaces result in fragility. The humans in the loop and static interfaces result in fragility. The
discovery of resources provided by an HTTP Web Server is typically discovery of resources provided by an HTTP Web Server is typically
called Web Linking [RFC5988]. The use of Web Linking for the called Web Linking [RFC5988]. The use of Web Linking for the
description and discovery of resources hosted by constrained web description and discovery of resources hosted by constrained web
servers is specified by the CoRE Link Format [RFC6690]. This servers is specified by the CoRE Link Format [RFC6690]. This
specification however only describes how to discover resources from specification however only describes how to discover resources from
the web server that hosts them by requesting /.well-known/core. In the web server that hosts them by requesting "/.well-known/core". In
many M2M scenarios, direct discovery of resources is not practical many M2M scenarios, direct discovery of resources is not practical
due to sleeping nodes, disperse networks, or networks where multicast due to sleeping nodes, disperse networks, or networks where multicast
traffic is inefficient. These problems can be solved by employing an traffic is inefficient. These problems can be solved by employing an
entity called a Resource Directory (RD), which hosts descriptions of entity called a Resource Directory (RD), which hosts descriptions of
resources held on other servers, allowing lookups to be performed for resources held on other servers, allowing lookups to be performed for
those resources. those resources.
This document specifies the web interfaces that a Resource Directory This document specifies the web interfaces that a Resource Directory
supports in order for web servers to discover the RD and to register, supports in order for web servers to discover the RD and to register,
maintain, lookup and remove resource descriptions. Furthermore, new maintain, lookup and remove resource descriptions. Furthermore, new
link attributes useful in conjunction with a Resource Directory are link attributes useful in conjunction with a Resource Directory are
defined. Although the examples in this document show the use of defined. Although the examples in this document show the use of
these interfaces with CoAP [I-D.ietf-core-coap], they can be applied these interfaces with CoAP [RFC7252], they can be applied in an
in an equivalent manner to HTTP [RFC2616]. equivalent manner to HTTP [RFC7230].
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in [RFC2119]. The term "OPTIONAL" in this document are to be interpreted as described in
"byte" is used in its now customary sense as a synonym for "octet". [RFC2119]. The term "byte" is used in its now customary sense as a
synonym for "octet".
This specification requires readers to be familiar with all the terms This specification requires readers to be familiar with all the terms
and concepts that are discussed in [RFC5988] and [RFC6690]. Readers and concepts that are discussed in [RFC5988] and [RFC6690]. Readers
should also be familiar with the terms and concepts discussed in should also be familiar with the terms and concepts discussed in
[I-D.ietf-core-coap]. The URI Template format is used to describe [RFC7252]. To describe the REST interfaces defined in this
the REST interfaces defined in this specification [RFC6570]. This specification, the URI Template format is used [RFC6570].
specification makes use of the following additional terminology:
This specification makes use of the following additional terminology:
Resource Directory Resource Directory
An web entity that stores information about web resources and A web entity that stores information about web resources and
implements the REST interfaces defined in this specification for implements the REST interfaces defined in this specification for
registration and lookup of those resources. registration and lookup of those resources.
Domain Domain
In the context of a Resource Directory, a domain is a logical In the context of a Resource Directory, a domain is a logical
grouping of endpoints. This specification assumes that the list grouping of endpoints. This specification assumes that the list
of Domains supported by an RD is pre-configured by that RD. of Domains supported by an RD is pre-configured by that RD. When
a domain is exported to DNS, the domain value equates to the DNS
domain name.
Group Group
In the context of a Resource Directory, a group is a logical In the context of a Resource Directory, a group is a logical
grouping of endpoints for the purpose of group communications. grouping of endpoints for the purpose of group communications.
All groups within a domain are unique. All groups within a domain are unique.
Endpoint Endpoint
An endpoint (EP) is a term used to describe a web server or client Endpoint (EP) is a term used to describe a web server or client in
in [I-D.ietf-core-coap]. In the context of this specification an [RFC7252]. In the context of this specification an endpoint is
endpoint is used to describe a web server that registers resources used to describe a web server that registers resources to the
to the Resource Directory. An endpoint is identified by its Resource Directory. An endpoint is identified by its endpoint
endpoint name, which is included during registration, and is name, which is included during registration, and is unique within
unique within the associated domain of the registration. the associated domain of the registration.
3. Architecture and Use Cases 3. Architecture and Use Cases
The resource directory architecture is shown in Figure 1. A Resource The resource directory architecture is illustrated in Figure 1. A
Directory (RD) is used as a repository for Web Links [RFC5988] about Resource Directory (RD) is used as a repository for Web Links
resources hosted on other web servers, which are called endpoints [RFC5988] about resources hosted on other web servers, which are
(EP). An endpoint is a web server associated with an IP address and called endpoints (EP). An endpoint is a web server associated with a
port, thus a physical node may host one or more endpoints. The RD scheme, IP address and port (called Context), thus a physical node
implements a set of REST interfaces for endpoints to register and may host one or more endpoints. The RD implements a set of REST
maintain sets of Web Links (called resource directory entries), for interfaces for endpoints to register and maintain sets of Web Links
the RD to validate entries, and for clients to lookup resources from (called resource directory entries), and for clients to lookup
the RD. Endpoints themselves can also act as clients. An RD can be resources from the RD or maintain groups. Endpoints themselves can
logically segmented by the use of Domains. The domain an endpoint is also act as clients. An RD can be logically segmented by the use of
associated with can be defined by the RD or configured by an outside Domains. The domain an endpoint is associated with can be defined by
entity. the RD or configured by an outside entity. This information
hierarchy is shown in Figure 2.
Endpoints are assumed to proactively register and maintain resource Endpoints are assumed to proactively register and maintain resource
directory entries on the RD, which are soft state and need to be directory entries on the RD, which are soft state and need to be
periodically refreshed. An endpoint is provided with interfaces to periodically refreshed. An endpoint is provided with interfaces to
register, update and remove a resource directory entry. Furthermore, register, update and remove a resource directory entry. Furthermore,
a mechanism to discover a RD using the CoRE Link Format is defined. a mechanism to discover an RD using the CoRE Link Format is defined.
It is also possible for an RD to proactively discover Web Links from It is also possible for an RD to proactively discover Web Links from
endpoints and add them as resource directory entries, or to validate endpoints and add them as resource directory entries. A lookup
existing resource directory entries. A lookup interface for interface for discovering any of the Web Links held in the RD is
discovering any of the Web Links held in the RD is provided using the provided using the CoRE Link Format.
CoRE Link Format.
Registration Lookup Registration Lookup, Group
+----+ | | +----+ | |
| EP |---- | | | EP |---- | |
+----+ ---- | | +----+ ---- | |
--|- +------+ | --|- +------+ |
+----+ | ----| | | +--------+ +----+ | ----| | | +--------+
| EP | ---------|-----| RD |----|-----| Client | | EP | ---------|-----| RD |----|-----| Client |
+----+ | ----| | | +--------+ +----+ | ----| | | +--------+
--|- +------+ | --|- +------+ |
+----+ ---- | | +----+ ---- | |
| EP |---- | | | EP |---- | |
+----+ +----+
Figure 1: The resource directory architecture. Figure 1: The resource directory architecture.
+------------+
| Domain | <-- Name
+------------+
| |
| +------------+
| | Group | <-- Name, IP
| +------------+
| |
+------------+
| Endpoint | <-- Name, Scheme, IP, Port
+------------+
|
|
+------------+
| Resource | <-- Target, Parameters
+------------+
Figure 2: The resource directory information hierarchy.
3.1. Use Case: Cellular M2M 3.1. Use Case: Cellular M2M
Over the last few years, mobile operators around the world have Over the last few years, mobile operators around the world have
focused on development of M2M solutions in order to expand the focused on development of M2M solutions in order to expand the
business to the new type of users, i.e. machines. The machines are business to the new type of users: machines. The machines are
connected directly to a mobile network using appropriate embedded air connected directly to a mobile network using an appropriate embedded
interface (GSM/GPRS, WCDMA, LTE) or via a gateway providing short and air interface (GSM/GPRS, WCDMA, LTE) or via a gateway providing short
wide range wireless interfaces. From the system design point of and wide range wireless interfaces. From the system design point of
view, the ambition is to design horizontal solutions that can enable view, the ambition is to design horizontal solutions that can enable
utilization of machines in different applications depending on their utilization of machines in different applications depending on their
current availability and capabilities as well as application current availability and capabilities as well as application
requirements, thus avoiding silo like solutions. One of the crucial requirements, thus avoiding silo like solutions. One of the crucial
enablers of such design is the ability to discover resources enablers of such design is the ability to discover resources
(machines - endpoints) capable of providing required information at a (machines -- endpoints) capable of providing required information at
given time or acting on instructions from the end users. a given time or acting on instructions from the end users.
In a typical scenario, during a boot-up procedure (and periodically In a typical scenario, during a boot-up procedure (and periodically
afterwards), the machines (endpoints) register with a Resource afterwards), the machines (endpoints) register with a Resource
Directory (for example EPs installed on vehicles enabling tracking of Directory (for example EPs installed on vehicles enabling tracking of
their position for the fleet management purposes and monitoring their position for fleet management purposes and monitoring
environment parameters) hosted by the mobile operator or somewhere environment parameters) hosted by the mobile operator or somewhere
else in the network, periodically a description of its own else in the network, periodically a description of its own
capabilities. Due to the usual network configuration of mobile capabilities. Due to the usual network configuration of mobile
networks, the EPs attached to the mobile network do not have routable networks, the EPs attached to the mobile network do not have routable
addresses. Therefore, a remote server is usually used to provide addresses. Therefore, a remote server is usually used to provide
proxy access to the EPs. The address of each (proxy) endpoint on proxy access to the EPs. The address of each (proxy) endpoint on
this server is included in the resource description stored in the RD. this server is included in the resource description stored in the RD.
The users, for example mobile applications for environment The users, for example mobile applications for environment
monitoring, contact the RD, look-up the endpoints capable of monitoring, contact the RD, look-up the endpoints capable of
providing information about the environment using appropriate set of providing information about the environment using appropriate set of
link parameters, obtain information on how to contact them (URLs of link parameters, obtain information on how to contact them (URLs of
the proxy server) and then initiate interaction to obtain information the proxy server) and then initiate interaction to obtain information
that is finally processed, displayed on the screen and usually stored that is finally processed, displayed on the screen and usually stored
in a database. Similarly, fleet management systems provide the in a database. Similarly, fleet management systems provide the
appropriate link parameters to the RD to look-up for EPs deployed on appropriate link parameters to the RD to look-up for EPs deployed on
the vehicles the application is responsible for. the vehicles the application is responsible for.
3.2. Use Case: Home and Building Automation 3.2. Use Case: Home and Building Automation
Home and commercial building automation systems can benefit from the Home and commercial building automation systems can benefit from the
use of M2M web services. The use of CoRE in home automation across use of M2M web services. The discovery requirements of these
multiple subnets is described in [I-D.brandt-coap-subnet-discovery] applications are demanding. Home automation usually relies on run-
and in commercial building automation in [I-D.vanderstok-core-bc]. time discovery to commission the system, whereas in building
The discovery requirements of these applications are demanding. Home automation a combination of professional commissioning and run-time
automation usually relies on run-time discovery to commission the discovery is used. Both home and building automation involve peer-
system, whereas in building automation a combination of professional to-peer interactions between endpoints, and involve battery-powered
commissioning and run-time discovery is used. Both home and building sleeping devices.
automation involve peer-to-peer interactions between endpoints, and
involve battery-powered sleeping devices.
The exporting of resource information to other discovery systems is The exporting of resource information to other discovery systems is
also important in these automation applications. In home automation also important in these automation applications. In home automation
there is a need to interact with other consumer electronics, which there is a need to interact with other consumer electronics, which
may already support DNS-SD, and in building automation larger may already support DNS-SD, and in building automation larger
resource directories or DNS-SD covering multiple buildings. resource directories or DNS-SD covering multiple buildings.
3.3. Use Case: Link Catalogues
Resources may be shared through data brokers that have no knowledge
beforehand of who is going to consume the data. Resource Directory
can be used to hold links about resources and services hosted
anywhere to make them discoverable by a general class of
applications.
For example, environmental and weather sensors that generate data for
public consumption may provide the data to an intermediary server, or
broker. Sensor data are published to the intermediary upon changes
or at regular intervals. Descriptions of the sensors that resolve to
links to sensor data may be published to a Resource Directory.
Applications wishing to consume the data can use the Resource
Directory lookup function set to discover and resolve links to the
desired resources and endpoints. The Resource Directory service need
not be coupled with the data intermediary service. Mapping of
Resource Directories to data intermediaries may be many-to-many.
Metadata in link-format or link-format+json representations are
supplied by Resource Directories, which may be internally stored as
triples, or relation/attribute pairs providing metadata about
resource links. External catalogs that are represented in other
formats may be converted to link-format or link-format+json for
storage and access by Resource Directories. Since it is common
practice for these to be URN encoded, simple and lossless structural
transforms will generally be sufficient to store external metadata in
Resource Directories.
The additional features of Resource Directory allow domains to be
defined to enable access to a particular set of resources from
particular applications. this provides isolation and protection of
sensitive data when needed. Resource groups may defined to allow
batched reads from multiple resources.
4. Simple Directory Discovery 4. Simple Directory Discovery
Not all endpoints hosting resources are expected to know how to Not all endpoints hosting resources are expected to know how to
implement the Resource Directory Function Set and thus explicitly implement the Resource Directory Function Set (see Section 5) and
register with a Resource Directory (or other such directory server). thus explicitly register with a Resource Directory (or other such
Instead, simple endpoints can implement the generic Simple Directory directory server). Instead, simple endpoints can implement the
Discovery approach described in this section. An RD implementing generic Simple Directory Discovery approach described in this
this specification MUST implement Simple Directory Discovery. section. An RD implementing this specification MUST implement Simple
However, there may be security reasons why this form of directory Directory Discovery. However, there may be security reasons why this
discovery would be disabled. form of directory discovery would be disabled.
This approach requires that the endpoint makes available the hosted This approach requires that the endpoint makes available the hosted
resources that it wants to be discovered, as links on its /.well- resources that it wants to be discovered, as links on its
known/core interface as specified in [RFC6690]. "/.well-known/core" interface as specified in [RFC6690].
The endpoint then finds one or more IP addresses of the directory The endpoint then finds one or more IP addresses of the directory
server it wants to know about its resources as described in server it wants to know about its resources as described in
Section 4.1. Section 4.1.
An endpoint that wants to make itself discoverable occasionally sends An endpoint that wants to make itself discoverable occasionally sends
a POST request to the /.well-known/core URI of any candidate a POST request to the "/.well-known/core" URI of any candidate
directory server that it finds. The body of the POST request is directory server that it finds. The body of the POST request is
either either
o empty, in which case the directory server is encouraged by this o empty, in which case the directory server is encouraged by this
POST request to perform GET requests at the requesting server's POST request to perform GET requests at the requesting server's
default discovery URI. default discovery URI.
or or
o a non-empty link-format document, which indicates the specific o a non-empty link-format document, which indicates the specific
skipping to change at page 8, line 4 skipping to change at page 10, line 15
4.1. Finding a Directory Server 4.1. Finding a Directory Server
Endpoints that want to contact a directory server can obtain Endpoints that want to contact a directory server can obtain
candidate IP addresses for such servers in a number of ways. candidate IP addresses for such servers in a number of ways.
In a 6LoWPAN, good candidates can be taken from: In a 6LoWPAN, good candidates can be taken from:
o specific static configuration (e.g., anycast addresses), if any, o specific static configuration (e.g., anycast addresses), if any,
o the ABRO option of 6LoWPAN-ND [RFC6775], o the ABRO option of 6LoWPAN-ND [RFC6775],
o other ND options that happen to point to servers (such as RDNSS), o other ND options that happen to point to servers (such as RDNSS),
o DHCPv6 options that might be defined later. o DHCPv6 options that might be defined later.
In networks with more inexpensive use of multicast, the candidate IP In networks with more inexpensive use of multicast, the candidate IP
address may be a well-known multicast address, i.e. directory servers address may be a well-known multicast address, i.e. directory servers
are found by simply sending POST requests to that well-known are found by simply sending POST requests to that well-known
multicast address (details TBD). multicast address (details TBD).
As some of these sources are just (more or less educated) guesses, As some of these sources are just (more or less educated) guesses,
endpoints MUST make use of any error messages to very strictly rate- endpoints MUST make use of any error messages to very strictly rate-
limit requests to candidate IP addresses that don't work out. E.g., limit requests to candidate IP addresses that don't work out. For
an ICMP Destination Unreachable message (and, in particular, the port example, an ICMP Destination Unreachable message (and, in particular,
unreachable code for this message) may indicate the lack of a CoAP the port unreachable code for this message) may indicate the lack of
server on the candidate host, or a CoAP error response code such as a CoAP server on the candidate host, or a CoAP error response code
4.05 "Method Not Allowed" may indicate unwillingness of a CoAP server such as 4.05 "Method Not Allowed" may indicate unwillingness of a
to act as a directory server. CoAP server to act as a directory server.
4.2. Third-party registration
For some applications, even Simple Directory Discovery may be too
taxing for certain very constrained devices, in particular if the
security requirements become too onerous.
In a controlled environment (e.g. building control), the Resource
Directory can be filled by a third device, called an installation
tool. The installation tool can fill the Resource Directory from a
database or other means. For that purpose the scheme, IP address and
port of the registered device is indicated in the Context parameter
of the registration as well.
5. Resource Directory Function Set 5. Resource Directory Function Set
This section defines the REST interfaces between an RD and endpoint This section defines the REST interfaces between an RD and endpoints,
servers, which is called the Resource Directory Function Set. which is called the Resource Directory Function Set. Although the
Although the examples throughout this section assume use of CoAP examples throughout this section assume the use of CoAP [RFC7252],
[I-D.ietf-core-coap], these REST interfaces can also be realized these REST interfaces can also be realized using HTTP [RFC7230]. An
using HTTP [RFC2616]. An RD implementing this specification MUST RD implementing this specification MUST support the discovery,
support the discovery, registration, update, and removal interfaces registration, update, lookup, and removal interfaces defined in this
defined in this section. section.
Resource directory entries are designed to be easily exported to Resource directory entries are designed to be easily exported to
other discovery mechanisms such as DNS-SD. For that reason, other discovery mechanisms such as DNS-SD. For that reason,
parameters that would meaningfully be mapped to DNS are limited to a parameters that would meaningfully be mapped to DNS SHOULD be limited
maximum length of 63 bytes. to a maximum length of 63 bytes.
5.1. Discovery 5.1. Discovery
Before an endpoint can make use of an RD, it must first know the RD's Before an endpoint can make use of an RD, it must first know the RD's
IP address, port and the path of its RD Function Set. There can be IP address, port and the path of its RD Function Set. There can be
several mechanisms for discovering the RD including assuming a several mechanisms for discovering the RD including assuming a
default location (e.g. on an Edge Router in a LoWPAN), by assigning 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 an anycast address to the RD, using DHCP, or by discovering the RD
using the CoRE Link Format (also see Section 4.1). This section using the CoRE Link Format (see also Section 4.1). This section
defines discovery of the RD using the well-known interface of the defines discovery of the RD using the well-known interface of the
CoRE Link Format [RFC6690] as the required mechanism. It is however CoRE Link Format [RFC6690] as the required mechanism. It is however
expected that RDs will also be discoverable via other methods expected that RDs will also be discoverable via other methods
depending on the deployment. depending on the deployment.
Discovery is performed by sending either a multicast or unicast GET Discovery is performed by sending either a multicast or unicast GET
request to /.well-known/core and including a Resource Type (rt) request to "/.well-known/core" and including a Resource Type (rt)
parameter [RFC6690] with the value "core.rd" in the query string. parameter [RFC6690] with the value "core.rd" in the query string.
Likewise, a Resource Type parameter value of "core.rd-lookup" is used Likewise, a Resource Type parameter value of "core.rd-lookup" is used
to discover the RD Lookup Function Set. Upon success, the response to discover the RD Lookup Function Set. Upon success, the response
will contain a payload with a link format entry for each RD will contain a payload with a link format entry for each RD
discovered, with the URL indicating the root resource of the RD. discovered, with the URL indicating the root resource of the RD.
When performing multicast discovery, the multicast IP address used When performing multicast discovery, the multicast IP address used
will depend on the scope required and the multicast capabilities of will depend on the scope required and the multicast capabilities of
the network. the network.
An RD implementation of this specification MUST support query An RD implementation of this specification MUST support query
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An RD implementation of this specification MUST support query An RD implementation of this specification MUST support query
filtering for the rt parameter as defined in [RFC6690]. filtering for the rt parameter as defined in [RFC6690].
The discovery request interface is specified as follows: The discovery request interface is specified as follows:
Interaction: EP -> RD Interaction: EP -> RD
Method: GET Method: GET
URI Template: /.well-known/core{?rt} URI Template: /.well-known/core{?rt}
URI Template Variables: URI Template Variables:
rt := Resource Type (optional). MAY contain the value rt := Resource Type (optional). MAY contain the value
"core.rd", "core.rd-lookup", "core.rd-group" or "core.rd*" "core.rd", "core.rd-lookup", "core.rd-group" or "core.rd*"
Content-Type: application/link-format (if any) Content-Type: application/link-format (if any)
The following response codes are defined for this interface: The following response codes are defined for this interface:
Success: 2.05 "Content" with an application/link-format payload Success: 2.05 "Content" with an application/link-format payload
containing a matching entry for the RD resource. containing one or more matching entries for the RD resource.
Failure: 4.04 "Not Found" is returned in case no matching entry is Failure: 4.04 "Not Found" is returned in case no matching entry is
found for a unicast request. found for a unicast request.
Failure: 4.00 "Bad Request" is returned in case of a malformed Failure: 4.00 "Bad Request" is returned in case of a malformed
request for a unicast request. request for a unicast request.
Failure: No error response to a multicast request. Failure: No error response to a multicast request.
The following example shows an endpoint discovering an RD using this The following example shows an endpoint discovering an RD using this
interface, thus learning that the base RD resource is at /rd. Note interface, thus learning that the base RD resource is, in this
that it is up to the RD to choose its base RD resource, although it example, at /rd. Note that it is up to the RD to choose its base RD
is recommended to use the base paths specified here where possible. resource, although diagnostics and debugging is facilitated by using
the base paths specified here where possible.
EP RD EP RD
| | | |
| ----- GET /.well-known/core?rt=core.rd* ------> | | ----- GET /.well-known/core?rt=core.rd* ------> |
| | | |
| | | |
| <---- 2.05 Content "</rd>; rt="core.rd" ------ | | <---- 2.05 Content "</rd>; rt="core.rd" ------ |
| | | |
Req: GET coap://[ff02::1]/.well-known/core?rt=core.rd* Req: GET coap://[ff02::1]/.well-known/core?rt=core.rd*
skipping to change at page 10, line 30 skipping to change at page 13, line 15
5.2. Registration 5.2. Registration
After discovering the location of an RD Function Set, an endpoint MAY After discovering the location of an RD Function Set, an endpoint MAY
register its resources using the registration interface. This register its resources using the registration interface. This
interface accepts a POST from an endpoint containing the list of interface accepts a POST from an endpoint containing the list of
resources to be added to the directory as the message payload in the resources to be added to the directory as the message payload in the
CoRE Link Format [RFC6690] or JSON Link Format CoRE Link Format [RFC6690] or JSON Link Format
[I-D.ietf-core-links-json] along with query string parameters [I-D.ietf-core-links-json] along with query string parameters
indicating the name of the endpoint, its domain and the lifetime of indicating the name of the endpoint, its domain and the lifetime of
the registration. All parameters except the endpoint name are the registration. All parameters except the endpoint name are
optional. It is expected that other specifications MAY define optional. It is expected that other specifications will define
further parameters (it is to be determined if a registry of further parameters (see Section 11.3). The RD then creates a new
parameters is needed for this purpose). The RD then creates a new
resource or updates an existing resource in the RD and returns its resource or updates an existing resource in the RD and returns its
location. An endpoint MUST use that location when refreshing location. An endpoint MUST use that location when refreshing
registrations using this interface. Endpoint resources in the RD are registrations using this interface. Endpoint resources in the RD are
kept active for the period indicated by the lifetime parameter. The kept active for the period indicated by the lifetime parameter. The
endpoint is responsible for refreshing the entry within this period endpoint is responsible for refreshing the entry within this period
using either the registration or update interface. The registration using either the registration or update interface. The registration
interface MUST be implemented to be idempotent, so that registering interface MUST be implemented to be idempotent, so that registering
twice with the same endpoint parameter does not create multiple RD twice with the same endpoint parameter does not create multiple RD
entries. entries.
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kept active for the period indicated by the lifetime parameter. The kept active for the period indicated by the lifetime parameter. The
endpoint is responsible for refreshing the entry within this period endpoint is responsible for refreshing the entry within this period
using either the registration or update interface. The registration using either the registration or update interface. The registration
interface MUST be implemented to be idempotent, so that registering interface MUST be implemented to be idempotent, so that registering
twice with the same endpoint parameter does not create multiple RD twice with the same endpoint parameter does not create multiple RD
entries. entries.
The registration request interface is specified as follows: The registration request interface is specified as follows:
Interaction: EP -> RD Interaction: EP -> RD
Method: POST Method: POST
URI Template: /{+rd}{?ep,d,et,lt,con} URI Template: /{+rd}{?ep,d,et,lt,con}
URI Template Variables: URI Template Variables:
rd := RD Function Set path (mandatory). This is the path of the rd := RD Function Set path (mandatory). This is the path of the
RD Function Set. An RD SHOULD use the value "rd" for this RD Function Set, as obtained from discovery. An RD SHOULD use
variable whenever possible. the value "rd" for this variable whenever possible.
ep := Endpoint (mandatory). The endpoint identifier or name of ep := Endpoint (mandatory). The endpoint identifier or name of
the registering node, unique within that domain. The maximum the registering node, unique within that domain. The maximum
length of this parameter is 63 bytes. length of this parameter is 63 bytes.
d := Domain (optional). The domain to which this endpoint d := Domain (optional). The domain to which this endpoint
belongs. The maximum length of this parameter is 63 bytes. belongs. This parameter SHOULD be less than 63 bytes.
Optional. When this parameter is elided, the RD MAY associate Optional. When this parameter is elided, the RD MAY associate
the endpoint with a configured default domain. the endpoint with a configured default domain. The domain
value is needed to export the endpoint to DNS-SD (see
Section 9).
et := Endpoint Type (optional). The semantic type of the et := Endpoint Type (optional). The semantic type of the
endpoint. The maximum length of this parameter is 63 bytes. endpoint. This parameter SHOULD be less than 63 bytes.
Optional. Optional.
lt := Lifetime (optional). Lifetime of the registration in lt := Lifetime (optional). Lifetime of the registration in
seconds. Range of 60-4294967295. If no lifetime is included, seconds. Range of 60-4294967295. If no lifetime is included,
a default value of 86400 (24 hours) SHOULD be assumed. a default value of 86400 (24 hours) SHOULD be assumed.
con := Context (optional). This parameter sets the scheme, con := Context (optional). This parameter sets the scheme,
address and port at which this server is available in the form address and port at which this server is available in the form
scheme://host:port. Optional. In the absence of this scheme://host:port. Optional. In the absence of this
parameter the scheme of the protocol, source IP address and parameter the scheme of the protocol, source IP address and
source port of the register request are assumed. source port of the register request are assumed. This
parameter is mandatory when the directory is filled by a third
party such as an installation tool.
Content-Type: application/link-format Content-Type: application/link-format
Content-Type: application/link-format+json Content-Type: application/link-format+json
The following response codes are defined for this interface: The following response codes are defined for this interface:
Success: 2.01 "Created". The Location header MUST be included with Success: 2.01 "Created". The Location header MUST be included with
the new resource entry for the endpoint. This Location MUST be a the new resource entry for the endpoint. This Location MUST be a
stable identifier generated by the RD as it is used for all stable identifier generated by the RD as it is used for all
subsequent operations on this registration. The resource returned subsequent operations on this registration. The resource returned
in the Location is only for the purpose of the Update (PUT) and in the Location is only for the purpose of the Update (POST) and
Removal (DELETE), and MUST NOT implement GET or POST methods. Removal (DELETE), and MUST NOT implement GET or PUT methods.
Failure: 4.00 "Bad Request". Malformed request. Failure: 4.00 "Bad Request". Malformed request.
Failure: 5.03 "Service Unavailable". Service could not perform the Failure: 5.03 "Service Unavailable". Service could not perform the
operation. operation.
The following example shows an endpoint with the name "node1" The following example shows an endpoint with the name "node1"
registering two resources to an RD using this interface. The registering two resources to an RD using this interface. The
resulting location /rd/4521 is just an example of an RD generated resulting location /rd/4521 is just an example of an RD generated
location. location.
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</sensors/temp>;ct=41;rt="temperature-c";if="sensor", </sensors/temp>;ct=41;rt="temperature-c";if="sensor",
</sensors/light>;ct=41;rt="light-lux";if="sensor" </sensors/light>;ct=41;rt="light-lux";if="sensor"
Res: 2.01 Created Res: 2.01 Created
Location: /rd/4521 Location: /rd/4521
5.3. Update 5.3. Update
The update interface is used by an endpoint to refresh or update its The update interface is used by an endpoint to refresh or update its
registration with an RD. To use the interface, the endpoint sends a registration with an RD. To use the interface, the endpoint sends a
PUT request to the resource returned in the Location option in the POST request to the resource returned in the Location option in the
response to the first registration. An update MAY contain response to the first registration. An update MAY update the
registration parameters if there have been changes since the last lifetime or context parameters if they have changed since the last
registration or update. Parameters that have not changed SHOULD NOT registration or update. Parameters that have not changed SHOULD NOT
be included in an update. Upon receiving an update request, the RD be included in an update. Upon receiving an update request, the RD
resets the timeout for that endpoint and stores the values of the resets the timeout for that endpoint and updates the scheme, IP
parameters included in the update (if any). address and port of the endpoint (using the source address of the
update, or the context parameter if present).
An update MAY optionally add or replace links for the endpoint by
including those links in the payload of the update as a CoRE Link
Format document. Including links in an update message greatly
increases the load on an RD and SHOULD be done infrequently. A link
is replaced only if both the target URI and relation type match (see
Section 10.1).
The update request interface is specified as follows: The update request interface is specified as follows:
Interaction: EP -> RD Interaction: EP -> RD
Method: PUT
URI Template: /{+location}{?et,lt,con} Method: POST
URI Template: /{+location}{?lt,con}
URI Template Variables: URI Template Variables:
location := This is the Location path returned by the RD as a location := This is the Location path returned by the RD as a
result of a successful registration. result of a successful earlier registration.
et := Endpoint Type (optional). The semantic type of the
endpoint. The maximum length of this parameter is 63 btyes.
Optional.
lt := Lifetime (optional). Lifetime of the registration in lt := Lifetime (optional). Lifetime of the registration in
seconds. Range of 60-4294967295. If no lifetime is included, seconds. Range of 60-4294967295. If no lifetime is included,
a default value of 86400 (24 hours) SHOULD be assumed. a default value of 86400 (24 hours) SHOULD be assumed.
con := Context (optional). This parameter sets the scheme, con := Context (optional). This parameter sets the scheme,
address and port at which this server is available in the form address and port at which this server is available in the form
scheme://host:port. Optional. In the absence of this scheme://host:port. Optional. In the absence of this
parameter the scheme of the protocol, source IP address and parameter the scheme of the protocol, source IP address and
source port used to register are assumed. source port used to register are assumed. This parameter is
compulsory when the directory is filled by a third party such
as an installation tool.
Content-Type: None Content-Type: application/link-format (optional)
Content-Type: application/link-format+json (optional)
The following response codes are defined for this interface: The following response codes are defined for this interface:
Success: 2.04 "Changed" in the update was successfully processed. Success: 2.04 "Changed" in the update was successfully processed.
Failure: 4.00 "Bad Request". Malformed request. Failure: 4.00 "Bad Request". Malformed request.
Failure: 4.04 "Not Found". Registration does not exist (e.g. may
have expired).
Failure: 5.03 "Service Unavailable". Service could not perform the Failure: 5.03 "Service Unavailable". Service could not perform the
operation. operation.
The following example shows an endpoint updating a new set of The following example shows an endpoint updating a new set of
resources to an RD using this interface. resources to an RD using this interface.
EP RD EP RD
| | | |
| --- PUT /rd/4521 --------------------------> | | --- POST /rd/4521 --------------------------> |
| | | |
| | | |
| <-- 2.04 Changed ---------------------------- | | <-- 2.04 Changed ---------------------------- |
| | | |
Req: PUT /rd/4521 Req: POST /rd/4521
Res: 2.04 Changed Res: 2.04 Changed
5.4. Removal 5.4. Removal
Although RD entries have soft state and will eventually timeout after Although RD entries have soft state and will eventually timeout after
their lifetime, an endpoint SHOULD explicitly remove its entry from their lifetime, an endpoint SHOULD explicitly remove its entry from
the RD if it knows it will no longer be available (for example on 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 shut-down). This is accomplished using a removal interface on the RD
by performing a DELETE on the endpoint resource. by performing a DELETE on the endpoint resource.
skipping to change at page 14, line 28 skipping to change at page 17, line 17
Interaction: EP -> RD Interaction: EP -> RD
Method: DELETE Method: DELETE
URI Template: /{+location} URI Template: /{+location}
URI Template Variables: URI Template Variables:
location := This is the Location path returned by the RD as a location := This is the Location path returned by the RD as a
result of a successful registration. result of a successful earlier registration.
The following responses codes are defined for this interface: The following responses codes are defined for this interface:
Success: 2.02 "Deleted" upon successful deletion Success: 2.02 "Deleted" upon successful deletion
Failure: 4.00 "Bad Request". Malformed request. Failure: 4.00 "Bad Request". Malformed request.
Failure: 4.04 "Not Found". Registration does not exist (e.g. may
have expired).
Failure: 5.03 "Service Unavailable". Service could not perform the Failure: 5.03 "Service Unavailable". Service could not perform the
operation. operation.
The following examples shows successful removal of the endpoint from The following examples shows successful removal of the endpoint from
the RD. the RD.
EP RD EP RD
| | | |
| --- DELETE /rd/4521 ------------------------> | | --- DELETE /rd/4521 ------------------------> |
| | | |
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directory function set, in that a group may be created or removed. directory function set, in that a group may be created or removed.
However unlike an endpoint entry, a group entry consists of a list of However unlike an endpoint entry, a group entry consists of a list of
endpoints and does not have a lifetime associated with it. In order endpoints and does not have a lifetime associated with it. In order
to make use of multicast requests with CoAP, a group MAY have a to make use of multicast requests with CoAP, a group MAY have a
multicast address associated with it. multicast address associated with it.
6.1. Register a Group 6.1. Register a Group
In order to create a group, a management entity used to configure In order to create a group, a management entity used to configure
groups, makes a request to the RD indicating the name of the group to groups, makes a request to the RD indicating the name of the group to
create (or update), the optional domain the group belongs to, and the create (or update), optionally the domain the group belongs to, and
optional multicast address of the group. The registration message optionally the multicast address of the group. The registration
includes the list of endpoints that belong to that group. If an message includes the list of endpoints that belong to that group. If
endpoint has already registered with the RD, the RD attempts to use an endpoint has already registered with the RD, the RD attempts to
the context of the endpoint from its RD endpoint entry. If the use the context of the endpoint from its RD endpoint entry. If the
client registering the group knows the endpoint has already client registering the group knows the endpoint has already
registered, then it MAY send a blank target URI for that endpoint registered, then it MAY send a blank target URI for that endpoint
link when registering the group. Configuration of the endpoints link when registering the group. Configuration of the endpoints
themselves is out of scope of this specification. Such an interface themselves is out of scope of this specification. Such an interface
for managing the group membership of an endpoint has been defined in for managing the group membership of an endpoint has been defined in
[I-D.ietf-core-groupcomm]. [I-D.ietf-core-groupcomm].
The registration request interface is specified as follows: The registration request interface is specified as follows:
Interaction: Manager -> RD Interaction: Manager -> RD
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path of the RD Group Function Set. An RD SHOULD use the value path of the RD Group Function Set. An RD SHOULD use the value
"rd-group" for this variable whenever possible. "rd-group" for this variable whenever possible.
gp := Group Name (mandatory). The name of the group to be gp := Group Name (mandatory). The name of the group to be
created or replaced, unique within that domain. The maximum created or replaced, unique within that domain. The maximum
length of this parameter is 63 bytes. length of this parameter is 63 bytes.
d := Domain (optional). The domain to which this group belongs. d := Domain (optional). The domain to which this group belongs.
The maximum length of this parameter is 63 bytes. Optional. The maximum length of this parameter is 63 bytes. Optional.
When this parameter is elided, the RD MAY associate the When this parameter is elided, the RD MAY associate the
endpoint with a configured default domain. endpoint with a configured default domain. The domain value is
needed to export the endpoint to DNS-SD (see Section 9)
con := Context (optional). This parameter is used to set the IP con := Context (optional). This parameter is used to set the IP
multicast address at which this server is available in the form multicast address at which this server is available in the form
scheme://multicast-address:port. Optional. In the absence of scheme://multicast-address:port. Optional. In the absence of
this parameter no multicast address is configured. this parameter no multicast address is configured. This
parameter is compulsory when the directory is filled by an
installation tool.
Content-Type: application/link-format Content-Type: application/link-format
Content-Type: application/link-format+json Content-Type: application/link-format+json
The following response codes are defined for this interface: The following response codes are defined for this interface:
Success: 2.01 "Created". The Location header MUST be included with Success: 2.01 "Created". The Location header MUST be included with
the new group entry. This Location MUST be a stable identifier the new group entry. This Location MUST be a stable identifier
generated by the RD as it is used for delete operations on this generated by the RD as it is used for delete operations on this
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location := This is the Location path returned by the RD as a location := This is the Location path returned by the RD as a
result of a successful group registration. result of a successful group registration.
The following responses codes are defined for this interface: The following responses codes are defined for this interface:
Success: 2.02 "Deleted" upon successful deletion Success: 2.02 "Deleted" upon successful deletion
Failure: 4.00 "Bad Request". Malformed request. Failure: 4.00 "Bad Request". Malformed request.
Failure: 4.04 "Not Found". Group does not exist.
Failure: 5.03 "Service Unavailable". Service could not perform the Failure: 5.03 "Service Unavailable". Service could not perform the
operation. operation.
The following examples shows successful removal of the group from the The following examples shows successful removal of the group from the
RD. RD.
EP RD EP RD
| | | |
| --- DELETE /rd-group/412 -------------------> | | --- DELETE /rd-group/412 -------------------> |
| | | |
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In order for an RD to be used for discovering resources registered In order for an RD to be used for discovering resources registered
with it, a lookup interface can be provided using this function set. 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 This lookup interface is defined as a default, and it is assumed that
RDs may also support lookups to return resource descriptions in RDs may also support lookups to return resource descriptions in
alternative formats (e.g. Atom or HTML Link) or using more advanced alternative formats (e.g. Atom or HTML Link) or using more advanced
interfaces (e.g. supporting context or semantic based lookup). interfaces (e.g. supporting context or semantic based lookup).
This function set allows lookups for domains, groups, endpoints and This function set allows lookups for domains, groups, endpoints and
resources using attributes defined in the RD Function Set and for use 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 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 list of links (if any) corresponding to the type of lookup. Using
of lookup. The target of these links SHOULD be the actual location the Accept Option, the requester can control whether this list is
of the domain, endpoint or resource, but MAY be an intermediate proxy returned in CoRE Link Format ("application/link-format", default) or
e.g. in the case of an HTTP lookup interface for CoAP endpoints. its JSON form ("application/link-format+json"). The target of these
Multiple query parameters MAY be included in a lookup, all included links SHOULD be the actual location of the domain, endpoint or
parameters MUST match for a resource to be returned. The character resource, but MAY be an intermediate proxy e.g. in the case of an
'*' MAY be included at the end of a parameter value as a wildcard HTTP lookup interface for CoAP endpoints. Multiple query parameters
operator. MAY be included in a lookup, all included parameters MUST match for a
resource to be returned. The character '*' MAY be included at the
end of a parameter value as a wildcard operator.
The lookup interface is specified as follows: The lookup interface is specified as follows:
Interaction: Client -> RD Interaction: Client -> RD
Method: GET Method: GET
URI Template: /{+rd-lookup-base}/ URI Template: /{+rd-lookup-base}/
{lookup-type}{?d,ep,gp,et,rt,page,count,resource-param} {lookup-type}{?d,ep,gp,et,rt,page,count,resource-param}
Parameters: Parameters:
rd-lookup-base := RD Lookup Function Set path (mandatory). This rd-lookup-base := RD Lookup Function Set path (mandatory). This
is the path of the RD Lookup Function Set. An RD SHOULD use the is the path of the RD Lookup Function Set. An RD SHOULD use the
value "rd-lookup" for this variable whenever possible. value "rd-lookup" for this variable whenever possible.
lookup-type := ("d", "ep", "res", "gp") (mandatory) This lookup-type := ("d", "ep", "res", "gp") (mandatory) This
variable is used to select the kind of lookup to perform variable is used to select the kind of lookup to perform
(domain, endpoint or resource). (domain, endpoint, resource, or group).
ep := Endpoint (optional). Used for endpoint, group and ep := Endpoint (optional). Used for endpoint, group and
resource lookups. resource lookups.
d := Domain (optional). Used for domain, group, endpoint and d := Domain (optional). Used for domain, group, endpoint and
resource lookups. resource lookups.
page := Page (optional). Parameter can not be used without the page := Page (optional). Parameter can not be used without the
count parameter. Results are returned from result set in pages count parameter. Results are returned from result set in pages
that contains 'count' results starting from index (page * that contains 'count' results starting from index (page *
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et := Endpoint type (optional). Used for group, endpoint and et := Endpoint type (optional). Used for group, endpoint and
resource lookups. resource lookups.
resource-param := Link attribute parameters (optional). Any resource-param := Link attribute parameters (optional). Any
link attribute as defined in Section 4.1 of [RFC6690], used for link attribute as defined in Section 4.1 of [RFC6690], used for
resource lookups. resource lookups.
The following responses codes are defined for this interface: The following responses codes are defined for this interface:
Success: 2.05 "Content" with an application/link-format or Success: 2.05 "Content" with an "application/link-format" or
application/link-format+json payload containing a matching entries "application/link-format+json" payload containing a matching
for the lookup. entries for the lookup.
Failure: 4.04 "Not Found" in case no matching entry is found for a Failure: 4.04 "Not Found" in case no matching entry is found for a
unicast request. unicast request.
Failure: No error response to a multicast request. Failure: No error response to a multicast request.
Failure: 4.00 "Bad Request". Malformed request. Failure: 4.00 "Bad Request". Malformed request.
Failure: 5.03 "Service Unavailable". Service could not perform the Failure: 5.03 "Service Unavailable". Service could not perform the
operation. operation.
The following example shows a client performing a resource lookup: The following example shows a client performing a resource lookup:
Client RD Client RD
| | | |
| ----- GET /rd-lookup/res?rt=temperature -----------------> | | ----- GET /rd-lookup/res?rt=temperature -----------------> |
| | | |
| | | |
| <-- 2.05 Content "<coap://node1/temp>;rt="temperature" ---- | | <-- 2.05 Content <coap://{host:port}/temp>;rt="temperature" |
| | | |
Req: GET /rd-lookup/res?rt=temperature Req: GET /rd-lookup/res?rt=temperature
Res: 2.05 Content Res: 2.05 Content
<coap://{ip:port}/temp> <coap://{host:port}/temp>;rt="temperature"
The following example shows a client performing an endpoint lookup: The following example shows a client performing an endpoint lookup:
Client RD Client RD
| | | |
| ----- GET /rd-lookup/ep?et=power-node --------------------> | | ----- GET /rd-lookup/ep?et=power-node --------------------> |
| | | |
| | | |
| <-- 2.05 Content "<coap://{ip:port}>;ep="node5" ----------- | | <-- 2.05 Content <coap://{ip:port}>;ep="node5" ------------ |
| | | |
Req: GET /rd-lookup/ep?et=power-node Req: GET /rd-lookup/ep?et=power-node
Res: 2.05 Content Res: 2.05 Content
<coap://{ip:port}>;ep="node5", <coap://{ip:port}>;ep="node5",
<coap://{ip:port}>;ep="node7" <coap://{ip:port}>;ep="node7"
The following example shows a client performing a domain lookup: The following example shows a client performing a domain lookup:
Client RD Client RD
| | | |
| ----- GET /rd-lookup/d ----------------------------------> | | ----- GET /rd-lookup/d ----------------------------------> |
| | | |
| | | |
| <-- 2.05 Content "</rd>;d=domain1,</rd>;d=domain2 --------- | | <-- 2.05 Content </rd>;d=domain1,</rd>;d=domain2 ---------- |
| | | |
Req: GET /rd-lookup/d Req: GET /rd-lookup/d
Res: 2.05 Content Res: 2.05 Content
</rd>;d="domain1", </rd>;d="domain1",
</rd>;d="domain2" </rd>;d="domain2"
The following example shows a client performing a group lookup for The following example shows a client performing a group lookup for
all groups: all groups:
Client RD Client RD
| | | |
| ----- GET /rd-lookup/gp ---------------------------------> | | ----- GET /rd-lookup/gp ---------------------------------> |
| | | |
| | | |
| <-- 2.05 Content </rd-group/12>;gp="lights1";d="domain1" -- | | <-- 2.05 Content </rd-group/12>;gp="lights1"; ------------- |
| d="example.com" ------------- |
| | | |
Req: GET /rd-lookup/gp Req: GET /rd-lookup/gp
Res: 2.05 Content Res: 2.05 Content
</rd-group/12>;gp="lights1";d="domain1" </rd-group/12>;gp="lights1";d="example.com"
The following example shows a client performing a lookup for all The following example shows a client performing a lookup for all
endpoints in a particular group: endpoints in a particular group:
Client RD Client RD
| | | |
| ----- GET GET /rd-lookup/ep?gp=lights1-------------------> | | ----- GET /rd-lookup/ep?gp=lights1-----------------------> |
| | | |
| | | |
| <-- 2.05 Content "</rd>;d=domain1,</rd>;d=domain2 --------- | | <-- 2.05 Content <coap://{host:port}>;ep="node1" ---------- |
| | | |
Req: GET /rd-lookup/ep?gp=lights1 Req: GET /rd-lookup/ep?gp=lights1
Res: 2.05 Content Res: 2.05 Content
<coap://host:port>;ep="node1", <coap://{host:port}>;ep="node1",
<coap://host:port>;ep="node2", <coap://{host:port}>;ep="node2",
The following example shows a client performing a lookup for all The following example shows a client performing a lookup for all
groups an endpoint belongs to: groups an endpoint belongs to:
Client RD Client RD
| | | |
| ----- GET /rd-lookup/gp?ep=node1 ------------------------> | | ----- GET /rd-lookup/gp?ep=node1 ------------------------> |
| | | |
| | | |
| <-- 2.05 Content "</rd>;d=domain1,</rd>;d=domain2 --------- | | <-- 2.05 Content <coap://{ip:port}>;gp="lights1";ep="node1" |
| | | |
Req: GET /rd-lookup/gp?ep=node1 Req: GET /rd-lookup/gp?ep=node1
Res: 2.05 Content Res: 2.05 Content
<coap://host:port>;gp="lights1";ep="node1", <coap://{ip:port}>;gp="lights1";ep="node1",
8. New Link-Format Attributes 8. New Link-Format Attributes
When using the CoRE Link Format to describe resources being When using the CoRE Link Format to describe resources being
discovered by or posted to a resource directory service, additional discovered by or posted to a resource directory service, additional
information about those resources is useful. This specification information about those resources is useful. This specification
defines the following new attributes for use in the CoRE Link Format defines the following new attributes for use in the CoRE Link Format
[RFC6690]: [RFC6690]:
link-extension = ( "ins" "=" quoted-string ) ; Max 63 bytes link-extension = ( "ins" "=" quoted-string ) ; Max 63 bytes
link-extension = ( "exp" ) link-extension = ( "exp" )
8.1. Resource Instance 'ins' attribute 8.1. Resource Instance attribute 'ins'
The Resource Instance "ins" attribute is an identifier for this The Resource Instance "ins" attribute is an identifier for this
resource, which makes it possible to distinguish from other similar resource, which makes it possible to distinguish it from other
resources. This attribute is similar in use to the "Instance" similar resources. This attribute is similar in use to the
portion of a DNS-SD record, and SHOULD be unique across resources <Instance> portion of a DNS-SD record (see Section 9.1, and SHOULD be
with the same Resource Type attribute in the domain it is used. A unique across resources with the same Resource Type attribute in the
Resource Instance might be a descriptive string like "Ceiling Light, domain it is used. A Resource Instance might be a descriptive string
Room 3", a short ID like "AF39" or a unique UUID or iNumber. This like "Ceiling Light, Room 3", a short ID like "AF39" or a unique UUID
attribute is used by a Resource Directory to distinguish between or iNumber. This attribute is used by a Resource Directory to
multiple instances of the same resource type within a system. distinguish between multiple instances of the same resource type
within the directory.
This attribute MUST be no more than 63 bytes in length. The resource This attribute MUST be no more than 63 bytes in length. The resource
identifier attribute MUST NOT appear more than once in a link identifier attribute MUST NOT appear more than once in a link
description. description.
8.2. Export 'exp' attribute 8.2. Export attribute 'exp'
The Export "exp" attribute is used as a flag to indicate that a link The Export "exp" attribute is used as a flag to indicate that a link
description MAY be exported by a resource directory to external description MAY be exported by a resource directory to external
directories. directories.
The CoRE Link Format is used for many purposes between CoAP The CoRE Link Format is used for many purposes between CoAP
endpoints. Some are useful mainly locally, for example checking the endpoints. Some are useful mainly locally, for example checking the
observability of a resource before accessing it, determining the size observability of a resource before accessing it, determining the size
of a resource, or traversing dynamic resource structures. However, of a resource, or traversing dynamic resource structures. However,
other links are very useful to be exported to other directories, for other links are very useful to be exported to other directories, for
example the entry point resource to a functional service. example the entry point resource to a functional service.
9. DNS-SD Mapping 9. DNS-SD Mapping
TODO CoRE Resource Discovery is intended to support fine-grained discovery
of hosted resources, their attributes, and possibly other resource
relations [RFC6690]. In contrast, service discovery generally refers
to a coarse-grained resolution of an endpoint's IP address, port
number, and protocol.
Resource and service discovery are complementary in the case of large
networks, where the latter can facilitate scaling. This document
defines a mapping between CoRE Link Format attributes and DNS-Based
Service Discovery [RFC6763] fields that permits discovery of CoAP
services by either means.
9.1. DNS-based Service discovery
DNS-Based Service Discovery (DNS-SD) defines a conventional method of
configuring DNS PTR, SRV, and TXT resource records to facilitate
discovery of services (such as CoAP servers in a subdomain) using the
existing DNS infrastructure. This section gives a brief overview of
DNS-SD; see [RFC6763] for a detailed specification.
DNS-SD service names are limited to 255 octets and are of the form:
Service Name = <Instance>.<ServiceType>.<Domain>.
The service name is the label of SRV/TXT resource records. The SRV
RR specifies the host and the port of the endpoint. The TXT RR
provides additional information.
The <Domain> part of the service name is identical to the global (DNS
subdomain) part of the authority in URIs that identify servers or
groups of servers.
The <ServiceType> part is composed of at least two labels. The first
label of the pair is the application protocol name [RFC6335] preceded
by an underscore character. The second label indicates the transport
and is always "_udp" for UDP-based CoAP services. In cases where
narrowing the scope of the search may be useful, these labels may be
optionally preceded by a subtype name followed by the "_sub" label.
An example of this more specific <ServiceType> is
"lamp._sub._dali._udp".
The default <Instance> part of the service name may be set at the
factory or during the commissioning process. It SHOULD uniquely
identify an instance of <ServiceType> within a <Domain>. Taken
together, these three elements comprise a unique name for an SRV/ TXT
record pair within the DNS subdomain.
The granularity of a service name MAY be that of a host or group, or
it could represent a particular resource within a CoAP server. The
SRV record contains the host name (AAAA record name) and port of the
service while protocol is part of the service name. In the case
where a service name identifies a particular resource, the path part
of the URI must be carried in a corresponding TXT record.
A DNS TXT record is in practice limited to a few hundred octets in
length, which is indicated in the resource record header in the DNS
response message. The data consists of one or more strings
comprising a key=value pair. By convention, the first pair is
txtver=<number> (to support different versions of a service
description).
9.2. mapping ins to <Instance>
The Resource Instance "ins" attribute maps to the <Instance> part of
a DNS-SD service name. It is stored directly in the DNS as a single
DNS label of canonical precomposed UTF-8 [RFC3629] "Net-Unicode"
(Unicode Normalization Form C) [RFC5198] text. However, to the
extent that the "ins" attribute may be chosen to match the DNS host
name of a service, it SHOULD use the syntax defined in Section 3.5 of
[RFC1034] and Section 2.1 of [RFC1123].
The <Instance> part of the name of a service being offered on the
network SHOULD be configurable by the user setting up the service, so
that he or she may give it an informative name. However, the device
or service SHOULD NOT require the user to configure a name before it
can be used. A sensible choice of default name can allow the device
or service to be accessed in many cases without any manual
configuration at all. The default name should be short and
descriptive, and MAY include a collision-resistant substring such as
the lower bits of the device's MAC address, serial number,
fingerprint, or other identifier in an attempt to make the name
relatively unique.
DNS labels are currently limited to 63 octets in length and the
entire service name may not exceed 255 octets.
9.3. Mapping rt to <ServiceType>
The resource type "rt" attribute is mapped into the <ServiceType>
part of a DNS-SD service name and SHOULD conform to the reg-rel-type
production of the Link Format defined in Section 2 of [RFC6690]. The
"rt" attribute MUST be composed of at least a single Net-Unicode text
string, without underscore '_' or period '.' and limited to 15 octets
in length, which represents the application protocol name. This
string is mapped to the DNS-SD <ServiceType> by prepending an
underscore and appending a period followed by the "_udp" label. For
example, rt="dali" is mapped into "_dali._udp".
The application protocol name may be optionally followed by a period
and a service subtype name consisting of a Net-Unicode text string,
without underscore or period and limited to 63 octets. This string
is mapped to the DNS-SD <ServiceType> by appending a period followed
by the "_sub" label and then appending a period followed by the
service type label pair derived as in the previous paragraph. For
example, rt="dali.light" is mapped into "light._sub._dali._udp".
The resulting string is used to form labels for DNS-SD records which
are stored directly in the DNS.
9.4. Domain mapping
DNS domains are defined from the "d" attribute.The domain attribute
is suffixed to the host name and should be consistent with the domain
name attributed to the hosting network segment.
9.5. TXT Record key=value strings
A number of [RFC6763] key/value pairs are derived from link-format
information, to be exported in the DNS-SD as key=value strings in a
TXT record ([RFC6763], Section 6.3).
The resource <URI> is exported as key/value pair "path=<URI>".
The Interface Description "if" attribute is exported as key/value
pair "if=<Interface Description>".
The DNS TXT record can be further populated by importing any other
resource description attributes as they share the same key=value
format specified in Section 6 of [RFC6763].
9.6. Importing resource links into DNS-SD
Assuming the ability to query a Resource Directory or multicast a GET
(?exp) over the local link, CoAP resource discovery may be used to
populate the DNS-SD database in an automated fashion. CoAP resource
descriptions (links) can be exported to DNS-SD for exposure to
service discovery by using the Resource Instance attribute as the
basis for a unique service name, composed with the Resource Type as
the <ServiceType>, and registered in the correct <Domain>. The agent
responsible for exporting records to the DNS zone file SHOULD be
authenticated to the DNS server. The following example shows an
agent discovering a resource to be exported:
Agent RD
| |
| --- GET /rd-lookup/res?exp ------------------------------> |
| |
| |
| <-- 2.05 Content "<coap://node1/light/1>;exp; ------------ |
| rt="dali.light";ins="FrontSpot" |
| d="example.com" |
| |
Req: GET /rd-lookup/res?exp
Res: 2.05 Content
<coap://[FDFD::1234]:61616/light/1>;
exp;ct=41;rt="dali.light";ins="FrontSpot";
d="example.com"
The agent subsequently registers the following DNS-SD RRs:
node1.example.com. IN AAAA
FDFD::1234
_dali._udp.example.com IN PTR
FrontSpot._dali._udp.example.com
light._sub._dali._udp.example.com IN PTR
FrontSpot._dali._udp.example.com
FrontSpot._dali._udp.example.com IN SRV 0 0 5678
node1.example.com.
FrontSpot._dali._udp.example.com IN TXT
txtver=1;path=/light/1
In the above figure the Service Name is chosen as
FrontSpot._dali._udp.example.com without the light._sub service
prefix. An alternative Service Name would be:
FrontSpot.light._sub._dali._udp.example.com.
10. Security Considerations 10. Security Considerations
This document needs the same security considerations as described in The security considerations as described in Section 7 of [RFC5988]
Section 7 of [RFC5988] and Section 6 of [RFC6690]. The /.well-known/ and Section 6 of [RFC6690] apply. The "/.well-known/core" resource
core resource may be protected e.g. using DTLS when hosted on a CoAP may be protected e.g. using DTLS when hosted on a CoAP server as
server as described in [I-D.ietf-core-coap]. described in [RFC7252]. DTLS or TLS based security SHOULD be used on
all resource directory interfaces defined in this document (TODO:
Improve the exact DTLS or TLS security requirements and references).
10.1. Endpoint Identification and Authentication
An Endpoint is determined to be unique by an RD by the Endpoint
identifier parameter included during Registration, and any associated
TLS or DTLS security bindings. An Endpoint MUST NOT be identified by
its protocol, port or IP address as these may change over the
lifetime of an Endpoint.
Every operation performed by an Endpoint or Client on a resource
directory SHOULD be mutually authenticated using Pre-Shared Key, Raw
Public Key or Certificate based security. Endpoints using a
Certificate MUST include the Endpoint identifier as the Subject of
the Certificate, and this identifier MUST be checked by a resource
directory to match the Endpoint identifier included in the
Registration message.
10.2. Access Control
Access control SHOULD be performed separately for the RD Function Set Access control SHOULD be performed separately for the RD Function Set
and the RD Lookup Function Set, as different endpoints may be and the RD Lookup Function Set, as different endpoints may be
authorized to register with an RD from those authorized to lookup authorized to register with an RD from those authorized to lookup
endpoints from the RD. Such access control SHOULD be performed in as endpoints from the RD. Such access control SHOULD be performed in as
fine-grained a level as possible. For example access control for fine-grained a level as possible. For example access control for
lookups could be performed either at the domain, endpoint or resource lookups could be performed either at the domain, endpoint or resource
level. level.
10.3. Denial of Service Attacks
Services that run over UDP unprotected are vulnerable to unknowingly
become part of a DDoS attack as UDP does not require return
routability check. Therefore, an attacker can easily spoof the
source IP of the target entity and send requests to such a service
which would then respond to the target entity. This can be used for
large-scale DDoS attacks on the target. Especially, if the service
returns a response that is order of magnitudes larger than the
request, the situation becomes even worse as now the attack can be
amplified. DNS servers have been widely used for DDoS amplification
attacks. Recently, it has been observed that NTP Servers, that also
run on unprotected UDP have been used for DDoS attacks (http://
tools.cisco.com/security/center/content/CiscoSecurityNotice/
CVE-2013-5211) [TODO: Ref, and cut down the verbiage, as this is
already discussed in RFC 7252] since there is no return routability
check and can have a large amplification factor. The responses from
the NTP server were found to be 19 times larger than the request. A
Resource Directory (RD) which responds to wild-card lookups is
potentially vulnerable if run with CoAP over UDP. Since there is no
return routability check and the responses can be significantly
larger than requests, RDs can unknowingly become part of a DDoS
amplification attack. Therefore, it is RECOMMENDED that
implementations ensure return routability. This can be done, for
example by responding to wild card lookups only over DTLS or TLS or
TCP.
11. IANA Considerations 11. IANA Considerations
11.1. Resource Types 11.1. Resource Types
"core.rd", "core.rd-group" and "core.rd-lookup" resource types need "core.rd", "core.rd-group" and "core.rd-lookup" resource types need
to be registered with the resource type registry defined by to be registered with the resource type registry defined by
[RFC6690]. [RFC6690].
11.2. Link Extension 11.2. Link Extension
skipping to change at page 24, line 28 skipping to change at page 32, line 23
Each entry in the registry must include the human readable name of Each entry in the registry must include the human readable name of
the parameter, the query parameter, validity requirements if any and the parameter, the query parameter, validity requirements if any and
a description. The query parameter MUST be a valid URI query key a description. The query parameter MUST be a valid URI query key
[RFC3986]. [RFC3986].
Initial entries in this sub-registry are as follows: Initial entries in this sub-registry are as follows:
+----------+-------+---------------+--------------------------------+ +----------+-------+---------------+--------------------------------+
| Name | Query | Validity | Description | | Name | Query | Validity | Description |
+----------+-------+---------------+--------------------------------+ +----------+-------+---------------+--------------------------------+
| Endpoint | ep | < 63 bytes | Name of the endpoint | | Endpoint | ep | | Name of the endpoint |
| Name | | | | | Name | | | |
| Lifetime | lt | 60-4294967295 | Lifetime of the registration | | Lifetime | lt | 60-4294967295 | Lifetime of the registration |
| | | | in seconds | | | | | in seconds |
| Domain | d | < 63 bytes | Domain to which this endpoint | | Domain | d | | Domain to which this endpoint |
| | | | belongs | | | | | belongs |
| Endpoint | et | | Semantic name of the endpoint | | Endpoint | et | | Semantic name of the endpoint |
| Type | | | | | Type | | | |
| Context | con | URI | The scheme, address and port | | Context | con | URI | The scheme, address and port |
| | | | at which this server is | | | | | at which this server is |
| | | | available | | | | | available |
| Endpoint | ep | | Name of the endpoint, max 63 | | Endpoint | ep | | Name of the endpoint, max 63 |
| Name | | | bytes | | Name | | | bytes |
| Group | gp | | Name of a group in the RD | | Group | gp | | Name of a group in the RD |
| Name | | | | | Name | | | |
| Page | page | Integer | Used for pagination | | Page | page | Integer | Used for pagination |
| Count | count | Integer | Used for pagination | | Count | count | Integer | Used for pagination |
+----------+-------+---------------+--------------------------------+ +----------+-------+---------------+--------------------------------+
Table 1: RD Parameters Table 1: RD Parameters
The IANA policy for future additions to the sub-registry is "Expert The IANA policy for future additions to the sub-registry is "Expert
Review" as described in [RFC5226] Review" as described in [RFC5226].
12. Acknowledgments 12. Examples
13. Acknowledgments
Szymon Sasin, Kerry Lynn, Esko Dijk, Peter van der Stok, Anders Srdjan Krco, Szymon Sasin, Kerry Lynn, Esko Dijk, Peter van der Stok,
Brandt, Matthieu Vial, Sampo Ukkola and Linyi Tian have provided Anders Brandt, Matthieu Vial, Michael Koster, Mohit Sethi, Sampo
helpful comments, discussions and ideas to improve and shape this Ukkola and Linyi Tian have provided helpful comments, discussions and
document. The authors would also like to thank their collagues from ideas to improve and shape this document. Zach would also like to
the EU FP7 SENSEI project, where many of the resource directory thank his collagues from the EU FP7 SENSEI project, where many of the
concepts were originally developed. resource directory concepts were originally developed.
13. Changelog 14. Changelog
Changes from -01 to -02:
o Added a catalogue use case.
o Changed the registration update to a POST with optional link
format payload. Removed the endpoint type update from the update.
o Additional examples section added for more complex use cases.
o New DNS-SD mapping section.
o Added text on endpoint identification and authentication.
o Error code 4.04 added to Registration Update and Delete
requests.
o Made 63 bytes a SHOULD rather than a MUST for endpoint name and
resource type parameters.
Changes from -00 to -01: Changes from -00 to -01:
o Removed the ETag validation feature. o Removed the ETag validation feature.
o Place holder for the DNS-SD mapping section. o Place holder for the DNS-SD mapping section.
o Explicitly disabled GET or POST on returned Location. o Explicitly disabled GET or POST on returned Location.
o New registry for RD parameters. o New registry for RD parameters.
skipping to change at page 26, line 22 skipping to change at page 34, line 42
parameter ep= and removed the h= and ins= parameters. parameter ep= and removed the h= and ins= parameters.
o Updated REST interface descriptions to use RFC6570 URI Template o Updated REST interface descriptions to use RFC6570 URI Template
format. format.
o Introduced an improved RD Lookup design as its own function set. o Introduced an improved RD Lookup design as its own function set.
o Improved the security considerations section. o Improved the security considerations section.
o Made the POST registration interface idempotent by requiring the o Made the POST registration interface idempotent by requiring the
ep= paramter to be present. ep= parameter to be present.
Changes from -01 to -02: Changes from -01 to -02:
o Added a terminology section. o Added a terminology section.
o Changed the inclusing of an ETag in registration or update to a o Changed the inclusion of an ETag in registration or update to a
MAY. MAY.
o Added the concept of an RD Domain and a registration parameter o Added the concept of an RD Domain and a registration parameter
for it. for it.
o Recommended the Location returned from a registration to be o Recommended the Location returned from a registration to be
stable, allowing for endpoint and Domain information to be changed stable, allowing for endpoint and Domain information to be changed
during updates. during updates.
o Changed the lookup interface to accept endpoint and Domain as o Changed the lookup interface to accept endpoint and Domain as
query string parameters to control the scope of a lookup. query string parameters to control the scope of a lookup.
14. References 15. References
14.1. Normative References 15.1. Normative References
[I-D.ietf-core-links-json] [I-D.ietf-core-links-json]
Bormann, C., "Representing CoRE Link Collections in JSON", Bormann, C., "Representing CoRE Link Collections in JSON",
draft-ietf-core-links-json-00 (work in progress), draft-ietf-core-links-json-02 (work in progress),
June 2013. July 2014.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005. RFC 3986, January 2005.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008. May 2008.
[RFC5988] Nottingham, M., "Web Linking", RFC 5988, October 2010. [RFC5988] Nottingham, M., "Web Linking", RFC 5988, October 2010.
[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165,
RFC 6335, August 2011.
[RFC6570] Gregorio, J., Fielding, R., Hadley, M., Nottingham, M., [RFC6570] Gregorio, J., Fielding, R., Hadley, M., Nottingham, M.,
and D. Orchard, "URI Template", RFC 6570, March 2012. and D. Orchard, "URI Template", RFC 6570, March 2012.
[RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link [RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link
Format", RFC 6690, August 2012. Format", RFC 6690, August 2012.
14.2. Informative References [RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service
Discovery", RFC 6763, February 2013.
[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] 15.2. Informative References
Shelby, Z., Hartke, K., and C. Bormann, "Constrained
Application Protocol (CoAP)", draft-ietf-core-coap-18
(work in progress), June 2013.
[I-D.ietf-core-groupcomm] [I-D.ietf-core-groupcomm]
Rahman, A. and E. Dijk, "Group Communication for CoAP", Rahman, A. and E. Dijk, "Group Communication for CoAP",
draft-ietf-core-groupcomm-16 (work in progress), draft-ietf-core-groupcomm-25 (work in progress),
October 2013. September 2014.
[I-D.vanderstok-core-bc] [RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
Stok, P. and K. Lynn, "CoAP Utilization for Building STD 13, RFC 1034, November 1987.
Control", draft-vanderstok-core-bc-05 (work in progress),
October 2011.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., [RFC1123] Braden, R., "Requirements for Internet Hosts - Application
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext and Support", STD 3, RFC 1123, October 1989.
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[RFC5198] Klensin, J. and M. Padlipsky, "Unicode Format for Network
Interchange", RFC 5198, March 2008.
[RFC6775] Shelby, Z., Chakrabarti, S., Nordmark, E., and C. Bormann, [RFC6775] Shelby, Z., Chakrabarti, S., Nordmark, E., and C. Bormann,
"Neighbor Discovery Optimization for IPv6 over Low-Power "Neighbor Discovery Optimization for IPv6 over Low-Power
Wireless Personal Area Networks (6LoWPANs)", RFC 6775, Wireless Personal Area Networks (6LoWPANs)", RFC 6775,
November 2012. November 2012.
[RFC7230] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
(HTTP/1.1): Message Syntax and Routing", RFC 7230,
June 2014.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252, June 2014.
Authors' Addresses Authors' Addresses
Zach Shelby Zach Shelby
ARM ARM
150 Rose Orchard 150 Rose Orchard
San Jose 95134 San Jose 95134
FINLAND FINLAND
Phone: +1-408-203-9434 Phone: +1-408-203-9434
Email: zach.shelby@arm.com Email: zach.shelby@arm.com
skipping to change at page 28, line 15 skipping to change at page 37, line 4
Authors' Addresses Authors' Addresses
Zach Shelby Zach Shelby
ARM ARM
150 Rose Orchard 150 Rose Orchard
San Jose 95134 San Jose 95134
FINLAND FINLAND
Phone: +1-408-203-9434 Phone: +1-408-203-9434
Email: zach.shelby@arm.com Email: zach.shelby@arm.com
Carsten Bormann Carsten Bormann
Universitaet Bremen TZI Universitaet Bremen TZI
Postfach 330440 Postfach 330440
Bremen D-28359 Bremen D-28359
Germany Germany
Phone: +49-421-218-63921 Phone: +49-421-218-63921
Email: cabo@tzi.org Email: cabo@tzi.org
Srdjan Krco
Ericsson
Phone:
Email: srdjan.krco@ericsson.com
 End of changes. 99 change blocks. 
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