SSDP is used by some consumer-level equipment for network discovery. It does not have any real use on public servers and is used for reflection DDoS attacks on dedicated servers.
On Linux machines SSDP is generally run through some type of UPNP server. The exact one varies significantly.
For Linux, we suggest blocking this with an iptables rule, such as:
iptables -I INPUT 1 -p udp -m udp --dport 1900 -j DROP
