Simple Service Discovery Protocol
Encyclopedia
The Simple Service Discovery Protocol (SSDP) is a network protocol based on the Internet Protocol Suite
Internet protocol suite
The Internet protocol suite is the set of communications protocols used for the Internet and other similar networks. It is commonly known as TCP/IP from its most important protocols: Transmission Control Protocol and Internet Protocol , which were the first networking protocols defined in this...

 for advertisement and discovery of network services and presence information. It accomplishes this without assistance of server-based configuration mechanisms, such as the Dynamic Host Configuration Protocol
Dynamic Host Configuration Protocol
The Dynamic Host Configuration Protocol is a network configuration protocol for hosts on Internet Protocol networks. Computers that are connected to IP networks must be configured before they can communicate with other hosts. The most essential information needed is an IP address, and a default...

 (DHCP) or the Domain Name System
Domain name system
The Domain Name System is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities...

 (DNS), and without special static configuration of a network host. SSDP is the basis of the discovery protocol of Universal Plug and Play
Universal Plug and Play
Universal Plug and Play is a set of networking protocols for primarily residential networks without enterprise class devices that permits networked devices, such as personal computers, printers, Internet gateways, Wi-Fi access points and mobile devices to seamlessly discover each other's presence...

 and is intended for use in residential or small office environments. It was formally described in an IETF Internet draft
Internet Draft
Internet Drafts is a series of working documents published by the IETF. Typically, they are drafts for RFCs, but may be other works in progress not intended for publication as RFCs. It is considered inappropriate to rely on Internet Drafts for reference purposes...

 by Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...

 and Hewlett-Packard
Hewlett-Packard
Hewlett-Packard Company or HP is an American multinational information technology corporation headquartered in Palo Alto, California, USA that provides products, technologies, softwares, solutions and services to consumers, small- and medium-sized businesses and large enterprises, including...

 in 1999. Although the IETF proposal has since expired, SSDP was incorporated into the UPNP protocol stack, and a description of the final implementation is included in UPnP standards documents.

Protocol transport and addressing

SSDP is a text-based protocol based on HTTPU
HTTPU
HTTPU is an extension of the HTTP/1.1 protocol using UDP as the data transport instead of the usual TCP protocol. HTTPMU is a variant of HTTPU that uses IP multicast.HTTPU is used as part of the implementation of Universal Plug and Play....

. It uses the User Datagram Protocol
User Datagram Protocol
The User Datagram Protocol is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol network without requiring...

 (UDP) as the underlying transport protocol. Services are announced by the hosting system with multicast
Multicast
In computer networking, multicast is the delivery of a message or information to a group of destination computers simultaneously in a single transmission from the source creating copies automatically in other network elements, such as routers, only when the topology of the network requires...

 addressing to a specifically designated IP multicast
IP Multicast
IP multicast is a method of sending Internet Protocol datagrams to a group of interested receivers in a single transmission. It is often employed for streaming media applications on the Internet and private networks. The method is the IP-specific version of the general concept of multicast...

 address at port number 1900. In IPv4
IPv4
Internet Protocol version 4 is the fourth revision in the development of the Internet Protocol and the first version of the protocol to be widely deployed. Together with IPv6, it is at the core of standards-based internetworking methods of the Internet...

, the multicast address is 239.255.255.250 and SSDP over IPv6
IPv6
Internet Protocol version 6 is a version of the Internet Protocol . It is designed to succeed the Internet Protocol version 4...

 uses the address set FF0X::C for all scope ranges indicated by X.

This results in the following well-known practical multicast addresses for SSDP:
  • 239.255.255.250 (IPv4 site-local address)
  • [FF02::C] (IPv6 link-local
    Link-local address
    A link-local address is an Internet Protocol address that is intended only for communications within the segment of a local network or a point-to-point connection that a host is connected to. Routers do not forward packets with link-local addresses....

    )
  • [FF05::C] (IPv6 site-local)
  • [FF08::C] (IPv6 organization-local)
  • [FF0E::C] (IPv6 global)

Additionally, applications may use the source-specific multicast addresses derived from the local IPv6 routing prefix, with group ID C (decimal 12).

SSDP uses a NOTIFY HTTP method to announce the establishment or withdrawal of services (presence) information to the multicast group. A client that wishes to discover available services on a network, uses the M-SEARCH method. Responses to such search requests are sent via unicast addressing to the originating address and port number of the multicast request.

Microsoft's IPv6 SSDP implementations in Windows Media Player and Server use the link-local scope address. Microsoft uses port number 2869 for event notification and event subscriptions. However, early implementations of SSDP also used port 5000 for this service.

See also

  • Service Location Protocol
    Service Location Protocol
    The Service Location Protocol is a service discovery protocol that allows computers and other devices to find services in a local area network without prior configuration. SLP has been designed to scale from small, unmanaged networks to large enterprise networks...

  • JINI
    Jini
    Jini , also called Apache River, is a network architecture for the construction of distributed systems in the form of modular co-operating services.Originally developed by Sun, Jini was released under an open source license...

  • Zero configuration networking
  • Neighbor Discovery Protocol
    Neighbor Discovery Protocol
    The Neighbor Discovery Protocol is a protocol in the Internet Protocol Suite used with Internet Protocol Version 6 . It operates in the Link Layer of the Internet model and is responsible for address autoconfiguration of nodes, discovery of other nodes on the link, determining the Link Layer...


External links

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