(Universal Plug aNd Play) A family of protocols from the UPnP Forum (www.upnp.org) for automatically configuring devices, discovering services and providing peer-to-peer data transfer over an IP network. Introduced in 1999, UPnP is not related to PnP (Plug and Play). It is related by concept: both provide zero configuration, which is automatic installation without manual configuration (see Plug and Play).
Comprised of more than 750 companies, the UPnP Forum covers many more application areas than the ones highlighted below, including lighting, heating and air conditioning, quality of service (QoS), security cameras and scanners.
UPnP Vs. Zeroconf
UPnP shares some features with Zeroconf, a widely used zero configuration technology implemented by Apple with its Bonjour software and by others. They both use link-local addressing for IP assignment and both provide service discovery, but each use different protocols (see Zeroconf). The functions that overlap are summarized below.
Automatic IP Address Assignment
If a device does not have an IP address and there is no DHCP server in the network, UPnP employs link-local addressing to create an IP address. See link-local address and DHCP.
Discovery and Data Transfer
Software such as Windows Media Connect uses UPnP to stream audio and video over the network. Several UPnP standards are employed including the Simple Service Discovery Protocol (SSDP) for finding devices and UPnP AV Architecture, MediaServer and MediaRenderer for streaming. See SSDP.
Port Forwarding (Port Mapping)
UPnP is used to open ports in a router to let a party from the outside world contact a user inside the network. For example, opening ports for VoIP and videoconferencing traffic makes two-way communications easier no matter which side initiates the call. See TCP/IP port.
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