UPnP is an architecture for pervasive peer-to-peer network connectivity of intelligent appliances, wireless devices, and PCs of all form factors. The scope of UPnP is large enough to encompass many existing, as well as new and exciting scenarios including home automation, printing and imaging, audio/video entertainment, kitchen appliances, automobile networks, and proximity networks in public venues. UPnP is a distributed, open networking architecture that leverages TCP/IP and the Web technologies to enable seamless proximity networking in addition to control and data transfer among networked devices. Under UPnP, no device drivers; common protocols are used instead. UPnP networking is media independent. UPnP devices can be implemented using any programming language, and on any operating system.

UPnP is more than just a simple extension of the plug and play peripheral model. It is designed to support zero-configuration, "invisible" networking, and automatic discovery for a breadth of device categories from a wide range of vendors. In other words, an UPnP device can dynamically join a network, obtain an IP address, convey its capabilities, and learn about the presence and capabilities of other devices. Finally, a device can leave a network smoothly and automatically without leaving any unwanted state behind.

UPnP leverages Internet technologies, including IP, TCP, UDP, HTTP, SSDP and XML. Like the Internet, contracts are based on wire protocols that are declarative, expressed in XML, and communicated via HTTP. UPnP has been explicitly designed to accommodate these environments. Further, via bridging, UPnP accommodates media running non-IP protocols when cost, technology, or legacy prevents the media or devices attached to it from running IP. UPnP does not specify the APIs applications will use, allowing operating system vendors to create the APIs that will meet their customer needs.

The following are the key components of UPnP architecture:

UPnP Devices - A UPnP device is a container of services and nested devices. For instance, a VCR device may consist of a tape transport service, a tuner service, and a clock service. A TV/VCR combo device would consist not just of services, but a nested device as well.

UPnP Services - The smallest unit of control in a UPnP network is a service. A service exposes actions and models its state with state variables. For instance, a clock service could be modeled as having a state variable, current_time, which defines the state of the clock, and two actions, set_time and get_time, which allow you to control the service.

UPnP Control Points - A control point in a UPnP network is a controller capable of discovering and controlling other devices.

UPnP Architecture Components

UPnP Protocol Stack

Related Terms: Plug and Play, SSDP, XML, HTTP,SOAP

Reference Links:
http://www.upnp.org/download/UPnPDA10_20000613.htm: UPnP Device Architecture
http://www.upnp.org: The Official Site of UPnP™ Forum