Pervasive Systems

Ioannis Chatzigiannakis

Sapienza University of RomeDepartment of Computer, Control, and Management Engineering (DIAG)

Lecture 9:CoAP

The Web and REST

Web Naming URL Resolution

An HTTP Request Web Paradigms

A REST Request CoAP Design Requirements

The CoAP Architecture The CoAP ProtocolI A very efficient RESTful protocolI Ideal for constrained devices and networksI Specialized for M2M applicationsI Easy to proxy to/from HTTPI Does not replace HTTPI Is not a cut-down HTTP versionI Not just for resource-constrained networks

CoAP FeaturesI Embedded web transfer protocol (coap://)I Asynchronous transaction modelI UDP binding with reliability and multicast supportI GET, POST, PUT, DELETE methodsI URI supportI Small, simple 4 byte headerI DTLS based PSK, RPK and Certificate securityI Subset of MIME types and HTTP response codesI Built-in discoveryI Optional observation and block transfer

Request Example

Dealing with Packet Loss Separate Response

Proxying and caching Observation

Block transfer