CoRE Z. Shelby
Internet-Draft Sensinode
Intended status: Informational M. Garrison Stuber
Expires: August 22, 2010 Itron
D. Sturek
Pacific Gas & Electric
B. Frank
Tridium, Inc
R. Kelsey
Ember
February 18, 2010
CoAP Requirements and Features
draft-shelby-core-coap-req-00
Abstract
This document considers the requirements and resulting features
needed for the design of the Constrained Application Protocol (CoAP).
Starting from requirements for energy and building automation
applications, the basic features are identified along with an
analysis of possible realizations. The goal of the document is to
provide a basis for protocol design and related discussion.
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This Internet-Draft will expire on August 22, 2010.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. CoAP Requirements . . . . . . . . . . . . . . . . . . . . 3
2. CoAP Feature Analysis . . . . . . . . . . . . . . . . . . . . 5
2.1. Compact Header . . . . . . . . . . . . . . . . . . . . . . 5
2.2. Basic Messages . . . . . . . . . . . . . . . . . . . . . . 6
2.3. REST Methods . . . . . . . . . . . . . . . . . . . . . . . 6
2.4. Content-type encoding . . . . . . . . . . . . . . . . . . 7
2.5. URLs . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.6. Caching . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.7. Subscribe/Notify . . . . . . . . . . . . . . . . . . . . . 9
2.8. Transport Binding . . . . . . . . . . . . . . . . . . . . 10
2.8.1. UDP . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.8.2. TCP . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.9. Resource Discovery . . . . . . . . . . . . . . . . . . . . 11
2.10. HTTP Mapping . . . . . . . . . . . . . . . . . . . . . . . 11
3. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1. Energy Applications . . . . . . . . . . . . . . . . . . . 12
3.2. Building Automation . . . . . . . . . . . . . . . . . . . 13
3.3. General M2M Applications . . . . . . . . . . . . . . . . . 13
4. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 14
5. Security Considerations . . . . . . . . . . . . . . . . . . . 14
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
8.1. Normative References . . . . . . . . . . . . . . . . . . . 15
8.2. Informative References . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
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1. Introduction
The use of web services on the Internet has become ubiquitous in most
applications, and depends on the fundamental Representational State
Transfer (REST) architecture of the web. The proposed Constrained
RESTful Environments (CoRE) working group aims at realizing the REST
architecture in a suitable form for the most constrained nodes (e.g.
8-bit microcontrollers with limited RAM and ROM) and networks (e.g.
6LoWPAN). One of the main goals of CoRE is to design a generic
RESTful protocol for the special requirements of this constrained
environment, especially considering energy and building automation
applications. The result of this work should be a Constrained
Application Protocol (CoAP) which easily traslates to HTTP for
integration with the web while meeting specialized requirements such
as multicast support, very low overhead and simplicity.
This document first analyzes the requirements for CoAP from the
proposed charter and related application requirement drafts in
Section 1.1. The key features needed for the CoAP protocol are then
identified in Section 2. Possible ways of realizing each feature are
considered and recommendations made where possible. Finally, the
applicability of these features to energy, building automation and
general M2M applications is considered in Section 3.
1.1. CoAP Requirements
The following requirements for CoAP have been identified in the
proposed charter of the working group (Feb 13, 2010 version), in the
6lowapp problem statement [I-D.bormann-6lowpan-6lowapp-problem], or
in the application specific requirement documents. This section is
not meant to introduce new requirements, only to summarize the
requirements from other sources. The requirements relevant to CoAP
can be summarizes as follows:
REQ1: CoRE solutions must be of appropriate complexity for use by
nodes have limited code size and limited RAM (e.g.
microcontrollers used in low-cost wireless devices typically
have on the order of 64-256K of flash and 4-12K of RAM).
[charter], [I-D.sturek-6lowapp-smartenergy]
REQ2: Protocol overhead and performance must be optimized for
constrained networks, which may exhibit extremely limited
throughput and a high degree of packet loss. For example,
multihop 6LoWPAN networks often exhibit application
throughput on the order of tens of kbits/s with a typical
payload size of 70-90 octets after transport layer headers.
[charter]
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REQ3: The ability to deal with sleeping nodes. Devices may be
powered off at any point in time but periodically "wake up"
for brief periods of time. [charter],
[I-D.sturek-6lowapp-smartenergy], [I-D.gold-6lowapp-sensei]
REQ4: Protocol must support the caching of recent resource
requests, along with caching subscriptions to sleeping nodes.
[charter]
REQ5: Must support the manipulation of simple resources on
constrained nodes and networks. The architecture requires
push, pull and a notify approach to manipulating resources.
CoAP will be able to create, read, update and delete a
Resource on a Device. [charter],
[I-D.sturek-6lowapp-smartenergy],
[I-D.martocci-6lowapp-building-applications],
[I-D.gold-6lowapp-sensei]
REQ6: The ability to allow a Device to publish a value or event to
another Device that has subscribed to be notified of changes,
as well as the way for a Device to subscribe to receive
publishes from another Device. [charter]
REQ7: Must define a mapping from CoAP to a HTTP REST API; this
mapping will not depend on a specific application and must be
as transparent as possible using standard protocol response
and error codes where possible. [charter],
[I-D.sturek-6lowapp-smartenergy], [I-D.gold-6lowapp-sensei]
REQ8: A definition of how to use CoAP to advertise about or query
for a Device's description. This description may include the
device name and a list of its Resources, each with a URL, an
interface description URI (pointing e.g. to a Web Application
Description Language (WADL) document) and an optional name or
identifier. The name taxonomy used for this description will
be consistent with other IETF work, e.g.
draft-cheshire-dnsext-dns-sd. [charter]
REQ9: CoAP will support a non-reliable multicast message to be sent
to a group of Devices to manipulate a resource on all the
Devices simultaneously [charter]. The use of multicast to
query and advertise descriptions must be supported, along
with the support of unicast responses
[I-D.sturek-6lowapp-smartenergy].
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REQ10: The core CoAP functionality must operate well over UDP and
UDP must be implemented on CoAP Devices. There may be
optional functions in CoAP (e.g. delivery of larger chunks of
data) which if implemented are implemented over TCP.
[charter], [I-D.sturek-6lowapp-smartenergy],
[I-D.martocci-6lowapp-building-applications]
REQ11: Reliability must be possible for application layer messages
over UDP [I-D.sturek-6lowapp-smartenergy].
REQ12: Latency times should be mimimized of the Home Area Network
(HAN), and ideally a typical exchange should consist of just
a single request and a single response message.
[I-D.sturek-6lowapp-smartenergy]
REQ13: Internet media type and transfer encoding type support.
[I-D.sturek-6lowapp-smartenergy], [I-D.gold-6lowapp-sensei]
REQ14: Consider operational and manageability aspects of the
protocol and at a minimum provide a way to tell if a Device
is powered on or not. [charter]
2. CoAP Feature Analysis
This section introduces the minimum set of features needed to realize
CoAP, and looks at the possible options for realizing them. These
features are considered in light of the requirements listed in
Section 1.1. The goal is to consider the cross-dependencies,
benefits and drawbacks of alternatives for realizing CoAP and to
narrow down the options where obvious.
2.1. Compact Header
There is a requirement for a header overhead appropriate for
constrained networks and with limited complexity due to node
limitations. The following header design options are considered:
Fixed approach: The simplest approach is to assume as fixed set of
byte-aligned fields. The use of variable length fields should
be avoided if possible, one obvious exception being a string
URL (see Section 2.5). This results in a simple header that
can be represented as a struct and easily parsed/created. The
disadvantages are difficult evolvability and the tendency to
design missing tranport features on-top of CoAP.
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Extensible approach: The approach of [I-D.frank-6lowapp-chopan] is
to encode HTTP headers as binary tuples, assuming that a large
number of optional headers will be needed. A similar approach
could be takenin CoAP, giving total header flexibility. The
disadvantage is header parsing complexity.
Hybrid approach: It is unclear how much extensibility is really
required from the headers of CoAP. Some of the fields in the
protocol will obviously require a sufficient value space for
future extensions, such as for indicating content type. Other
headers are clearly optional, such as those related to cache
control (see Section 2.6) or even the URL (see Section 2.5). A
hybrid approach would be to design a small fixed header, with
the ability to include extension headers, such as in ICMP
[RFC0792].
Considering the features foreseen by this document, some kind of
extensible hybrid approach is recommended. Many features are fixed
for messages, whereas some are expected to be optional.
2.2. Basic Messages
It is assumed that basic Request and Response messages will be
required by the CoAP protocol. This also provides a natural mapping
to HTTP (See Section 2.10) and the response may be useful as an
acknowledgement in UDP reliability (See Section 2.8.1). It can be
considered that CoAP methods are different kinds of Request messages,
therefore a separate Request message is not needed.
2.3. REST Methods
The core methods of REST must be supported within CoAP. To minimize
confusion with HTTP methods, having their own protocol semantics, in
CoAP we call the basic REST methods CREATE, READ, UPDATE, DELETE
(CRUD)
[http://en.wikipedia.org/wiki/Create,_read,_update_and_delete].
Additionally, CoAP must support a light-weight Subscribe/Notify
mechanism (see Section 2.7). This may require a new NOTIFY method.
The discovery mechanism of CoAP may also require a new method called
DISCOVER which has different semantics than a READ (see Section 2.9).
In order to maintain compatibility with HTTP, these new messages must
be mapped to a standard HTTP method. See Section 2.10 for more about
HTTP mapping.
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2.4. Content-type encoding
In order to support hetergenous uses, it is important that CoAP is
transparent to the use of different application payloads. In order
for the application process receiving a packet to properly parse a
payload, its content-type and encoding should be explicitly known
from the header (as e.g. with HTTP). The use of typical binary
encodings for XML is discussed in [I-D.shelby-6lowapp-encoding],
which includes recommendations for header indication. The draft
recommends the indication of at least 10 Internet media types (MIME)
[RFC2046] and 2 content transfer encodings.
It is obvious that string names of Internet media types [RFC2046] are
not appropriate for use in the CoAP header. But then how to make
this small yet extensible? One possible solution is to simply assign
codes to a small subset of common MIME and content transfer encoding
types and have IANA maintain that. A field of 16-bits should be
sufficient for encoding both media and content transfer encoding
types. For extending some types, magic numbers can also be used from
the beginning of the payload (as defined in associated Internet media
type RFCs). This could be indicated by a header value something like
"See magic numbers".
2.5. URLs
The Universal Resource Locator (URL) [RFC3986] is an important
feature of the REST architecture, the relative part of the URL
indicates which resource on the server is being manipulated. It is
surely useful for CoAP to support string URLs, which requires a
variable length-value field. Although URLs can be designed for
compactness, this still often results in 10s of bytes of overhead.
The encoding of the URL string also needs to be considered, as this
is becoming increasingly complex. It is recommended that only US-
ASCII is supported in URL strings for CoAP as defined in [RFC3986],
or even a stricter subset as URL parsing is complex and may result in
security problems on constrained devices.
Constrained devices are not general purpose web servers, and thus
often won't host but a small set of resources with fixed URLs. Thus
in addition to string URLs a feature for compressing fixed URLs would
be useful.
One way of achieving this would be to assign an integer identifier
(7-8 bits should be sufficient) to each fixed URL in an off-line
interface description (e.g. Web Application Description Langauge
(WADL)) or in its description. This identifier could be encoded in
the URL length field instead of the string length with a flag.
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2.6. Caching
The cachability of CoAP messages will be important, especially with
the sleeping node configurations and power limitations typically
found in constrained networks and nodes. What features of
cachability are really required and how much energy are we willing to
spend on it? Roughly 50% of the HTTP specifications are dedicated to
sohpisticated caching. With CoAP we should look at the bare minimum
caching feature possible.
Before talking about caching solutiongs, we should consider in what
scenarios caching will actually be required. The following two
scenarios have been identified:
o An intermediate CoAP proxy may cache resources and answer READ
requests using a cached version. The resource may be cached from
previous responses or notifications. This requires at least Max-
Age cache control information about each resource.
o An intermediate CoAP proxy may cache subscriptions to a sleeping
node. This requires at least Max-Age information about the
subscription.
Three possible approaches have been identified for caching support.
In-band approach: One approach is suggested in
[I-D.frank-6lowapp-chopan], which analyses the subset of
features from HTTP that could be used for simple sensor data
purposes. The proposal is that simply using the using the HTTP
Age header (for resource age) and Cache-Control header (for
max-age). Max-age may also be applied in requests. Both
headers make use of a 2-byte value in seconds. The advantage
of this approach is that cache control information is easily
available from the header. The disadvantage is some header
overhead.
Out-of-band approach: Here the CoAP protocol would be agnostic to
the cachability of the resources it is carrying, instead
leaving the definition of cache control parameters to the body
of the resources in an application specific way. The
disadvantage is that this makes proxies dependent on the
application.
Discovery approach: In this approach the cache control information
for resources is defined off-line in the list of a Device's
resources. This approach is used e.g. in the SENSEI system
[I-D.gold-6lowapp-sensei]. The disadvantage is that the
caching is dependent on the profile, which may not be a problem
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if the cache information is in a universal format (see
Section 2.9).
Based on the current analysis the In-band approach would be
reasonable for CoAP considering the requirements. This doesn't
prevent the inclusion of cachability information in a resource
description as well.
2.7. Subscribe/Notify
CoAP is required to integrate a push model for interaction in
addition to traditional request/response. This means that interested
clients could subscribe to a resource (a URL), and receive
notifications to a call-back URL of their choice. In its most basic
form a notification would be sent each time the resource changes.
There are many issues to consider including managing subscription
leasing and timeouts, how to batch multiple changes and how to tune
notification times. Before considering the details, there are a two
general models possible for realizing the Subscribe/Notify mechanism:
Resource: Subscribe is realized using CREATE on a well known
resource (e.g. /subsribe) with the URL of the resource of
interest and a URL call-back in the body). Notifications would
be made using a NOTIFY (or alternatively UPDATE) message to the
call-back URL. Likewise, de-subscribe is realized using DELETE
on the same well known resource with the URL in the body.
Notifications would cease after the DELETE.
Watch: This method would require a CREATE to a new URI to "create" a
new watch resource. UPDATE is then used to add/remove a set of
URIs being "watched" along with call-backs.
Subscribe: An alternative to using CREATE on /subscribe or to make a
new watch resource, would be to develop an explicit SUBSCRIBE
method which is used directly on the URL of interest. The body
of the SUBSCRIBE would include the call-back URL and other
subscription information.
The mapping requirement of CoAP with HTTP requires that the mapping
between methods should be as simple as possible. Therefore the
addition of new methods such as NOTIFY and SUBSCRIBE should be done
with care. As NOTIFY is a push concept, this may at least be
justified.
The complexity of subscription management should also be carefully
considered when working with constrained devices. An increasing
number of subscription options leads to greater complexity,
especially when dealing with multiple subscriptions to a resource.
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Subscription options to a proxy via HTTP may be quite a bit more
complex than those via CoAP to a constrained device.
2.8. Transport Binding
The CoAP protocol will operate by default over UDP. There may be
OPTIONAL functions in CoAP (e.g. delivery of larger chunks of data)
which if implemented are implemented over TCP. In this section we
look at transport issues.
2.8.1. UDP
The goal of binding CoAP to UDP is to provide the bare minimum
features for the protocol to operate over UDP, going nowhere near
trying to re-create the full feature set of TCP. The bare minimum
features required would be:
o Stop-and-wait would be sufficient for reliability. A simple
response message itself would suffice as an acknowledgement with
retransmission support. Not all requests require reliability,
thus this should be optional. Performance is not the key here and
for more sophisticated reliability and flow control TCP could be
used.
o A sequence number (transaction ID) is needed to match responses to
open requests and would be generated by the client. A 12-16 bit
unsigned interger would be sufficient. [I-D.frank-6lowapp-chopan]
also considered this solution.
o Multicast support. Providing reliability with a multicast
destination address would be very complex. Therefore the goal is
to provide a non-reliable multicast service. In many cases there
may not be a response to a multicast message. A multicast command
might result in an action being taken at a device, but no response
being sent. Therefore a multicast request may be answered with a
unicast response, however without reliability (retransmission
e.g.).
2.8.2. TCP
The CoAP protocol also may also make use of TCP for some features.
As TCP provides a reliable stream this binding does not require
anything special from the CoAP protcol design. The same basic
messages could be applied over TCP without stop-and-wait. A
transaction ID should still be used over TCP. The question is for
which features, or in which configurations would TCP be recommended?
The following have been identified so far:
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o Delivering a large chunk of data.
o Delivering a continuous stream of data, for example streaming
sensor readings for a long period.
o TCP may also be useful for providing congestion control if CoAP is
being applied across the wider Internet.
2.9. Resource Discovery
This document assumes that an application either a) knows that CoAP
services are running on a default or pre-configured port in the
network or b) a service discovery method has already been used to
locate CoAP services. Thus service discovery is not considered in
this document.
CoAP is required to support the querying and advertisement of
resources offered by CoAP services. In order to achieve this, the
protocol would need to suport multicast with optional responses for
discovery, along with unicast or multicast advertisement of resource
descriptions. A well-known resource (e.g. /resources) could be used
to enable discovery through a new DISCOVER method (or alternatively a
READ). The response to a DISCOVER message would include a list of
resource URLs available, an optional URI to an interface description
and an optional name or identifier. CoAP services could also
advertise their description by sending e.g. a multicast NOTIFY to
/resources, or by posting their description to a central place (e.g.
a proxy) with a CREATE to /resources.
In order to save overhead as descriptions for some nodes could become
long, nodes could apply a technique similar to that used in XMPP. By
default Devices would advertise a hash of their description or a hash
of each resource in the description. A receiver would be able to
match hashes of already known resources, and could DISCOVER the
resource for its full description.
2.10. HTTP Mapping
It shall be possible to map from CoAP directly to HTTP, CoAP however
only offers a small subset of the HTTP protocol features. As a
result, programs implementing translation between HTTP and CoAP must
either implement other HTTP 1.1 commands on behalf of the CoAP nodes
(e.g. LINK, TRACE, OPTIONS), or must reject such request. The
primary responsibility of a program translating between HTTP and CoAP
is to rewrite the headers, translating between the highly optimized
CoAP headers and plain text HTTP headers. It must also manage/
maintain TCP sessions necessary for HTTP. Depending on how some of
the features of CoAP are realized, the mapping may also need to make
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further translations for subscription or caching.
Subscription (see the exampe below) will require a proxy mapping
CoAP-HTTP to support some kind of LONG POLL method as being defined
in the HyBi WG in order to avoid continuous polling of a subscription
status [draft-loreto-http-bidirectional-01].
Sensor <------ coap ------> Proxy <------- http --------> Client
CREATE /subscribe <- <- POST /subscribe
OK -> -> OK (/sub1)
<- LONG GET /sub1
GET stays open
Resource changes
NOTIFY /temp -> -> OK (/temp)
OK <-
Figure 1: Example CoAP-HTTP mapping for subscription.
3. Applicability
This sections looks at the applicability of the CoAP features for
energy, building automation and other macine-to-machine (M2M)
applications.
3.1. Energy Applications
Rising energy prices, concerns about global warming and energy
resource depletion, and societal interest in more ecologically
friendly living have resulted in government mandates for Smart Energy
solutions. In a Smart Energy environment consumers of energy have
direct, immediate access to information about their consumption, and
are able to take action based on that information. Smart Energy
systems also allow device to device communication to optimize the
transport, reliability, and safety of energy delivery systems. While
often Smart Energy solutions are electricity-centric, i.e. Smart
Grid, gas and water are also subject to the same pressures, and can
benefit from the same technology.
Smart Energy Transactions typically include the exchange of current
consumption information, text messages from providers to consumers,
and control signals requesting a reduction in consumption. Advanced
features such as billing information, energy prepayment transactions,
management of distributed energy resources (e.g. generators and
photo-voltaics), and management of electric vehicles are also being
developed.
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Smart Energy benefits from Metcalfe's Law. The more devices that are
part of a smart energy network within the home or on the grid, the
more valuable it becomes. Showing a consumer how much energy they
are using is useful. Combining that with specific information about
their major appliances, and enabling them to adjust their consumption
based on current pricing and system demand is much much more
powerful. To do this however requires a system that is resillient,
low cost, and easy to install. In many areas this is being done with
systems built around IEEE 802.15.4 radios. In the United States,
there are over 30 million electric meters that will be deployed with
these radios. These radios will be combined to form a mesh network,
enabling Smart Energy communication within the home. The maximum
packet size for IEEE 802.15.4 is only 127 bytes. Additionally, there
is the well known issue of how TCP manages congestion working sub-
optimally over wireless networks. IEEE 802.15.4 is ideal for these
applications because of its low cost and its support for battery
powered devices; however, it is not as well suited for heavier
protocols like HTTP. These technical issues with IEEE 802.15.4
networks combined with a desire to facilitate broader compatibility,
makes a protocol like CoAP desireable. Its REST architecture will
allow seamless compatibility with the rest of the Internet, allowing
it to be easily integrated with web browsers and web-based service
providers, while at the same time being appropriately sized for the
low-cost networks necessary for its success.
3.2. Building Automation
Building automation applications were analyzed in detail including
use cases in [I-D.martocci-6lowapp-building-applications]. Although
many of the embedded control solutions for building automation make
use of industry-specific application protocols like BACnet over IP,
there is a growing use of web services in building monitoring, remote
control and IT integration. The OASIS oBIX standard [ref] is one
example of the use of web services for the monitoring and
interconnection of heterogeneous building systems. Several of the
CoAP requirements have been taken from
[I-D.martocci-6lowapp-building-applications]. The resulting features
should allow for peer-to-peer interactions as well as node-server
request/response and push interfactions for monitoring and some
control purposes. For building automation control with very strict
timing requirements using e.g. multicast, further features may be
required on top of CoAP.
3.3. General M2M Applications
CoAP provides a natural extension of the REST architecture into the
domain of constrained nodes and networks, aiming at requirements from
automation applications in energy and building automation. A very
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wide range of machine-to-machine (M2M) applications have similar
requirements to those considered in this document, and thus it is
foreseen that CoAP may be widely applied in the industry. One
standardization group considering a general M2M architecture and API
is the ETSI M2M TC [ref], which considers a wide range of
applications including energy. Another group developing solutions
for general embedded device control is the OASIS Device Proile Web
Services (DPWS) group. The consideration of DPWS over 6LoWPAN is
available in [I-D.moritz-6lowapp-dpws-enhancements].
4. Conclusions
This document analyzed the requirements associated with the design of
the foreseen Constrained Application Protocol (CoAP). Based on these
requirements a list of minumum features was analyzed along with
different options for realizing them. If possible a recommendation
was also made where obvious. Finally, the identified features of
CoAP are considered for energy, building automation and M2M
applications. This document is meant to serve as a basis for the
design of the CoAP protocol and relevant discussion.
CoAP is proposed as a transport agnostic extension of REST for
deployment in confined computing environments. The intent is to
align CoAP with HTTP wherever possible to leverage the web services
computing environment already in place.
Whereas REST envisions just 4 primitives (CRUD), CoAP may propose to
extend this paradigm with e.g. a NOTIFY primitive to enable publish/
subscribe along with a DISCOVER primitive to support multicast
discovery of services denoted by URL. The main architectural
difference between READ and the new discovery primitive is the
support for multicast and a possible matching feature.
Finally, CoAP seeks to preserve the caching facilities of HTTP and
extend that capability for power saving devices that are not always
active on the network.
5. Security Considerations
Some of the features considered in this document will need further
security considerations during a protocol design. For example the
use of string URLs may have entail security risks due to complex
processing on limited microcontroller implementations.
The CoAP protocol will be designed for use with e.g. (D)TLS or
object security. A protocol design should consider how integration
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with these security methods will be done, how to secure the CoAP
header and other implications.
6. IANA Considerations
This draft requires no IANA consideration.
7. Acknowledgments
Thanks to Cullen Jennings, Guido Moritz, Peter Van Der Stok, Adriano
Pezzuto, Lisa Dussealt, Gilbert Clark and Salvatore Loreto for
helpful comments and discussions.
8. References
8.1. Normative References
[I-D.frank-6lowapp-chopan]
Frank, B., "Chopan - Compressed HTTP Over PANs",
draft-frank-6lowapp-chopan-00 (work in progress),
September 2009.
[I-D.gold-6lowapp-sensei]
Gold, R., Krco, S., Gluhak, A., and Z. Shelby, "SENSEI
6lowapp Requirements", draft-gold-6lowapp-sensei-00 (work
in progress), October 2009.
[I-D.martocci-6lowapp-building-applications]
Martocci, J. and A. Schoofs, "Commercial Building
Applications Requirements",
draft-martocci-6lowapp-building-applications-00 (work in
progress), October 2009.
[I-D.shelby-6lowapp-encoding]
Shelby, Z., Luimula, M., and D. Peintner, "Efficient XML
Encoding and 6LowApp", draft-shelby-6lowapp-encoding-00
(work in progress), October 2009.
[I-D.sturek-6lowapp-smartenergy]
Sturek, D., Shelby, Z., Lohman, D., Stuber, M., and S.
Ashton, "Smart Energy Requiements for 6LowApp",
draft-sturek-6lowapp-smartenergy-00 (work in progress),
October 2009.
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
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Extensions (MIME) Part Two: Media Types", RFC 2046,
November 1996.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
8.2. Informative References
[I-D.bormann-6lowpan-6lowapp-problem]
Bormann, C., Sturek, D., and Z. Shelby, "6LowApp: Problem
Statement for 6LoWPAN and LLN Application Protocols",
draft-bormann-6lowpan-6lowapp-problem-01 (work in
progress), July 2009.
[I-D.moritz-6lowapp-dpws-enhancements]
Moritz, G., "DPWS for 6LoWPAN",
draft-moritz-6lowapp-dpws-enhancements-00 (work in
progress), December 2009.
[RFC0792] Postel, J., "Internet Control Message Protocol", STD 5,
RFC 792, September 1981.
Authors' Addresses
Zach Shelby
Sensinode
Kidekuja 2
Vuokatti 88600
FINLAND
Phone: +358407796297
Email: zach@sensinode.com
Michael Garrison Stuber
Itron
2111 N. Molter Road
Liberty Lake, WA 99025
U.S.A.
Phone: +1.509.891.3441
Email: Michael.Stuber@itron.com
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Don Sturek
Pacific Gas & Electric
77 Beale Street
San Francisco, CA
USA
Phone: +1-619-504-3615
Email: d.sturek@att.net
Brian Frank
Tridium, Inc
Richmond, VA
USA
Phone:
Email: brian.tridium@gmail.com
Richard Kelsey
Ember
47 Farnsworth Street
Boston, MA 02210
U.S.A.
Phone: +1.617.951.1201
Email: richard.kelsey@ember.com
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