SSDP (Simple Service Discovery Protocol)

You may have encountered SSDP (Simple Service Discovery Protocol) in the context of the Services tab in Task Manager in the form of SSDPSRV (SSDP Discovery Service). 

It is a HTTPU (HTTP UDP) text based protocol i.e. relies on UDP underneath.

The SSDP protocol can discover Plug and Play devices, with uPnP (Universal Plug and Play).

The SSDP protocol has been found to be used in DDoS attacks also known as SSDP Reflection Attack with Amplification.

Vulnerabilities also arise from widespread proliferation of certain open source libraries e.g. pupnp.