IrLMP

IrLMP, or Infrared Link Management Protocol, is a layer in the Infrared Data Association (IrDA) protocol stack that provides the management of logical connections between infrared devices. It operates above the Link Access Protocol (IrLAP) and below upper-layer protocols such as OBEX, serving as the middleware that establishes, maintains, and terminates sessions and channels over an IrDA link.

The core purpose of IrLMP is to enable multiple higher-layer services to share a single infrared link by multiplexing them over logical channels. It supports both connection-oriented (reliable) and connectionless (unreliable) communication and handles session setup, negotiation, and release. Upper-layer services register themselves with IrLMP via service access points (SAPs), which identify the services offered by a device. IrLMP also handles basic flow control and error reporting at the session level and coordinates with the underlying IrLAP connection.

A key feature of IrLMP is its integration with service and device discovery. Using the Service Discovery Protocol (SDP) framework, devices can advertise and browse available services on remote IrDA devices, facilitating dynamic connection establishment without prior knowledge of remote capabilities.

In typical usage, IrLMP manages the lifecycle of connections that carry data for upper-layer protocols such as OBEX, which is commonly used for object exchange (e.g., file transfers). By providing multiplexing and session management, IrLMP enables efficient use of infrared links and supports a range of infrared-enabled applications.

Today, IrLMP is a component of the legacy IrDA stack. While once widespread in practical devices, it has largely been superseded in modern contexts by other wireless technologies, though it remains of historical and educational interest in infrared communication standards.