The document discusses CoAP (Constrained Application Protocol), a protocol designed for resource-constrained devices. It describes CoAP's features like RESTful interaction, observing resources, and resource discovery. It also discusses integrating CoAP with the web through a CoAP implementation in Firefox called Copper. A user study found that most prefer a web browser for interacting with CoAP resources. The document envisions future work on enabling CoAP requests from browsers and scripting for physical mashups.

1. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 1|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
Matthias Kovatsch
kovatsch@inf.ethz.ch
CoAP for the Web of Things:
From Tiny Resource-constrained Devices
to the Web Browser
Monday, 9 Sep 2013
4th International Workshop on the Web of Things (WoT 2013)
Zurich, Switzerland

2. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 2|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
The Web of Things
Electronic things are invading us...
Slide courtesy
of Vlad Trifa

3. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 3|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
The Web of Things – of Powerful Devices
Often mains-powered, capable of running Linux, or using application-level gateways

4. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 4|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
Directly connecting to the Internet in a secure manner
Tiny Resource-constrained Devices
Target of
less than $1
Class 1 devices
~100kB ROM
~10kB RAM

5. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 5|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
6LoWPAN for seamless Internet integration
Custom WSN Protocols on the Retreat
TCP and HTTP
problematic in
low-power
networks

6. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 6|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
 RESTful protocol designed from scratch
 Transparent mapping to HTTP
 Additional features for M2M scenarios
Constrained Application Protocol (CoAP)
Message Sub-layer
Reliability
UDP DTLS …
Request/Response Sub-layer
RESTful interaction
GET, POST, PUT, DELETE,
URIs, and Internet Media Types
Deduplication and
optional retransmissions (Confirmables)
CoAP

7. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 7|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
 Binary protocol
 Low parsing complexity
 Small message size
 Header options
 Numbers with IANA registry
 Type-Length-Value
 Special option header
marks payload if present
Constrained Application Protocol (CoAP)
0 – 8 Bytes Token
Exchange handle for client
4-byte Base Header
Version | T-len | Type | Code | ID
Header Options
Location, Max-Age, ETag, …
Marker
0xFF
Payload
Representation

8. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 8|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
Observing Resources
Server
Client
Resource state at origin server
Replicated state at client
Notification
lost
Max-Age
Observe illustration courtesy of Klaus Hartke

9. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 9|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
Observing Resources – CON Notifications
Server
Client
Resource state at origin server
Replicated state at client
Observe illustration courtesy of Klaus Hartke

10. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 10|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
RESTful Group Communication
all-lights.floor-d.example.com
GET /status/power
PUT /control/color
#00FF00
Enabled by IP multicast

11. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 11|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
 Based on Web Linking (RFC 5988)
 Extended to CoRE Link Format (RFC 6690)
 Multicast Discovery
 Resource Directories
Resource Discovery
</config/groups>;rt="core.gp";ct=39,
</sensors/temperature>;rt="ucum.Cel";ct="0 41 50";obs,
</large>;rt="block";sz=1280;title="Large resource"
GET /.well-known/core (RFC 5785)

12. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 12|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
 Short Message Service (SMS)
 Unstructured Supplementary
Service Data (USSD)
 Addressable through URIs
(URI scheme not finalized)
 Response possible over UDP/IP
through Return-Path option
Alternative Transports
*101# 
coap+sms://+123456789/bananas/temperature

13. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 13|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
 Proposed Standard since 15 Jul 2013
 draft-ietf-core-coap-18
 In RFC Editor Queue: MISSREF
 draft-ietf-tls-oob-pubkey (Raw Public Keys)
 draft-mcgrew-tls-aes-ccm-ecc (Elliptic Curve Crypto)
 In use by
 OMA Lightweight M2M
 IPSO Alliance
 ETSI M2M
 Accounting and monitoring for network operators
 Lighting systems for smart cities
Status of CoAP

14. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 14|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
48 participants knowledgeable about CoAP and the IoT
 Contiki and TinyOS communities (Wireless Sensor Networks)
 ETSI M2M associates (M2M solutions)
 IETF followers (Internet technology)
 Differentiation checked with Wilcoxon rank-sum test
User Study
Academia
and
Hobbyists
(30+2)
Industry
(16)
0-4 years
experience
(33)
5+ years
(15)

15. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 15|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
Agreement with our Hypotheses
Responses from 48 participants on the Likert scale
(0 = strongly disagree, 4 = strongly agree, error bars: +/- 1 std. dev.)
0
1
2
3
4
Internet protocols ease the
development of distributed
software for tiny devices.
Web patterns ease the
development of distributed
software for tiny devices.
CoAP in addition to HTTP is
a necessity for the Internet of
Things.
I prefer using a HTTP-CoAP
cross-proxy for accessing
devices.
Overall
Academia
Industry
Less than
5 years
5 years
and more

16. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 16|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
 CoAP protocol handler
for Mozilla Firefox
 Browsing and bookmarking
of CoAP URIs
 Interaction with resource like
RESTClient1 or Poster2
 Treat tiny devices like
normal RESTful Web services
CoAP Support in the Web Browser
1 https://addons.mozilla.org/en-US/refox/addon/poster/
2 https://addons.mozilla.org/en-US/refox/addon/restclient/
https://addons.mozilla.org/firefox/addon/copper-270430/

17. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 17|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
Copper (Cu)

18. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 18|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
 Majority (N=41) prefers the
Web browser as CoAP client
for user interaction
 Main use cases for Copper (Cu)
 Debugging own implementation
 Giving a demo
 Browsing existing
CoAP Web services
 Reasons for a different client
 Automation and scripting (55%)
 I do not use Firefox (8%)
Market Share of CoAP Clients
Copper (Cu)
41%
libcoap client
17%
Sensinode
NanoService
Java Client
5%
Californium (Cf)
GUI client
5%
Californium (Cf)
console client
10%
other
22%

19. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 19|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
 Web-like interaction with
tiny devices is preferable
 People not as confident to see
native support in Web browsers
2.8 / 4 on the Likert scale
 UDP and DTLS support through
Real-time communication
in Web browsers (RTCWeb)
 Mozilla open for patches
Native CoAP Support in Web Browsers
Web browser
integration of CoAP
(77%)
standalone
(23%)

20. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 20|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
 Actinium (Ac) App-server for Cf
 Server-side JavaScript
 CoapRequest object API
 Mashups in the background
Future work
 Enable CoapRequest object
in the Web browser
 Script interactions
 Visualize data
 Mashups with GUI
Scripting for Physical Mashups

21. Questions?
Matthias Kovatsch https://github.com/mkovatsc/
kovatsch@inf.ethz.ch http://people.inf.ethz.ch/mkovatsc/

22. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 22|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
Application-agnostic Device Infrastructure
 Erbium (Er) REST Engine
 RESTful wrapper for hardware
 Impact of radio duty cycling
on application-layer protocols
[A Low-Power CoAP for Contiki, MASS 2012]
 Implementation guidance
[draft-kovatsch-lwig-coap-01, IETF 2013]
 https://github.com/contiki-os/contiki
The Thin Server Architecture

23. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 23|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
Application development outside of the embedded domain
 Californium (Cf) framework
 Unconstrained service back-end
[Moving Application Logic from the Firmware to
the Cloud: Towards the Thin Server Architecture
for the Internet of Things, IMIS 2012]
 DTLS 1.2 implementation
 IETF “running code”
 ETSI Plugtests
[Industry Adoption of the Internet of Things:
A Constrained Application Protocol Survey,
SOCNE 2012]
 https://github.com/mkovatsc/Californium
Application Logic in the Cloud

24. CoAP for the Web of Things: From Tiny Resource-constrained Devices to the Web Browser 24|
Matthias Kovatsch
http://people.inf.ethz.ch/mkovatsc
Customization for SMEs and consumers
 Actinium (Ac) App-server for Cf
 Server-side JavaScript
 CoapRequest object API
 Feasibility study of scripting for
IoT applications
[Actinium: A RESTful Runtime Container for
Scriptable Internet of Things Applications,
IoT 2012]
 https://github.com/mkovatsc/Actinium
Scripting for End-user Mashups