89-614: Windows Media Connect ( WMC ) is a UPnP AV server from Microsoft for Windows XP and later Windows operating systems, to share and stream media on a Windows computer to WMC clients. The first two releases of WMC were made available as stand-alone software, and included a client as well. Following that, it was renamed to Home Media Ecosystem ( HME ) and the media server component was integrated into Windows Media Player and Windows Home Server . WMC version 2.0 can be manually installed on Windows Server 2008 or Windows Server 2008 R2 32bit or 64bit operating system but this type of installation
178-591: A PC . Hardware-based UPnP AV media servers may run on any NAS devices or any specific hardware for delivering media, such as a DVR . As of May 2008, there were more software-based UPnP AV media servers than there were hardware-based servers. One solution for NAT traversal , called the Internet Gateway Device Control Protocol (UPnP IGD Protocol), is implemented via UPnP. Many routers and firewalls expose themselves as Internet Gateway Devices, allowing any local UPnP control point to perform
267-455: A local area network . WMC advertises itself to the clients, so there is no need to manually configure the client to connect to the WMC server. Multiple WMC instances can run at a time, all will be accessible to a client. Any UPnP AV client can be used to access WMC shared media. The client can query WMC for the list of files shared, the result of the query is formatted using XML . Once it chooses from
356-402: A tunneling arrangement to accommodate the connection of dissimilar networks. For example, IP may be tunneled across an Asynchronous Transfer Mode (ATM) network. Protocol layering forms the basis of protocol design. It allows the decomposition of single, complex protocols into simpler, cooperating protocols. The protocol layers each solve a distinct class of communication problems. Together,
445-489: A UPnP audio/video (AV) architecture consists of: A UPnP AV media server is the UPnP-server ("master" device) that provides media library information and streams media-data (like audio/video/picture/files) to UPnP clients on the network. It is a computer system or a similar digital appliance that stores digital media, such as photographs, movies, or music and shares these with other devices. UPnP AV media servers provide
534-591: A UPnP device assigns itself an address is known within the UPnP Device Architecture as AutoIP . In UPnP Device Architecture Version 1.0, AutoIP is defined within the specification itself; in UPnP Device Architecture Version 1.1, AutoIP references IETF RFC 3927 . If during the DHCP transaction, the device obtains a domain name, for example, through a DNS server or via DNS forwarding ,
623-639: A coarse hierarchy of functional layers defined in the Internet Protocol Suite . The first two cooperating protocols, the Transmission Control Protocol (TCP) and the Internet Protocol (IP) resulted from the decomposition of the original Transmission Control Program, a monolithic communication protocol, into this layered communication suite. The OSI model was developed internationally based on experience with networks that predated
712-599: A computer environment (such as ease of mechanical parsing and improved bandwidth utilization ). Network applications have various methods of encapsulating data. One method very common with Internet protocols is a text oriented representation that transmits requests and responses as lines of ASCII text, terminated by a newline character (and usually a carriage return character). Examples of protocols that use plain, human-readable text for its commands are FTP ( File Transfer Protocol ), SMTP ( Simple Mail Transfer Protocol ), early versions of HTTP ( Hypertext Transfer Protocol ), and
801-455: A computer—to zero-configuration networking for residential and SOHO wireless networks. UPnP devices are plug-and-play in that, when connected to a network, they automatically establish working configurations with other devices, removing the need for users to manually configure and add devices through IP addresses . UPnP is generally regarded as unsuitable for deployment in business settings for reasons of economy, complexity, and consistency:
890-535: A device's service. To do this, a control point sends a suitable control message to the control URL for the service (provided in the device description). Control messages are also expressed in XML using the Simple Object Access Protocol (SOAP). Much like function calls , the service returns any action-specific values in response to the control message. The effects of the action, if any, are modeled by changes in
979-861: A fix to the protocol specification in April 2020, but since many devices running UPnP are not easily upgradable, CallStranger is likely to remain a threat for a long time to come. CallStranger has fueled calls for end-users to abandon UPnP because of repeated failures in security of its design and implementation. The UPnP protocols were promoted by the UPnP Forum (formed in October 1999), a computer industry initiative to enable simple and robust connectivity to standalone devices and personal computers from many different vendors. The Forum consisted of more than 800 vendors involved in everything from consumer electronics to network computing. Since 2016, all UPnP efforts have been managed by
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#17330848864921068-414: A list of the commands , or actions , to which the service responds, and parameters, or arguments , for each action; the description for a service also includes a list of variables ; these variables model the state of the service at run time and are described in terms of their data type, range, and event characteristics. Having retrieved a description of the device, the control point can send actions to
1157-490: A list of the problems with IGDP that prompted the creation of NAT-PMP and its successor PCP. A number of further standards have been defined for the UPnP Device Architecture: Networking protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any variation of a physical quantity . The protocol defines
1246-453: A machine rather than a human being. Binary protocols have the advantage of terseness, which translates into speed of transmission and interpretation. Binary have been used in the normative documents describing modern standards like EbXML , HTTP/2 , HTTP/3 and EDOC . An interface in UML may also be considered a binary protocol. Getting the data across a network is only part of the problem for
1335-415: A malicious web site when someone with a UPnP-enabled router simply visits that web site. This only applies to the "firewall-hole-punching"-feature of UPnP ; it does not apply when the router/firewall does not support UPnP IGD or has been disabled on the router. Also, not all routers can have such things as DNS server settings altered by UPnP because much of the specification (including LAN Host Configuration)
1424-453: A networking protocol, the protocol software modules are interfaced with a framework implemented on the machine's operating system. This framework implements the networking functionality of the operating system. When protocol algorithms are expressed in a portable programming language the protocol software may be made operating system independent. The best-known frameworks are the TCP/IP model and
1513-417: A packet-switched network, rather than this being a service of the network itself. His team was the first to tackle the highly complex problem of providing user applications with a reliable virtual circuit service while using a best-effort service , an early contribution to what will be the Transmission Control Protocol (TCP). Bob Metcalfe and others at Xerox PARC outlined the idea of Ethernet and
1602-434: A pointer (network location) to more detailed information. After a control point has discovered a device, the control point still knows very little about the device. For the control point to learn more about the device and its capabilities, or to interact with the device, the control point must retrieve the device's description from the location ( URL ) provided by the device in the discovery message. The UPnP Device Description
1691-554: A protocol. The data received has to be evaluated in the context of the progress of the conversation, so a protocol must include rules describing the context. These kinds of rules are said to express the syntax of the communication. Other rules determine whether the data is meaningful for the context in which the exchange takes place. These kinds of rules are said to express the semantics of the communication. Messages are sent and received on communicating systems to establish communication. Protocols should therefore specify rules governing
1780-554: A reference model for communication standards led to the OSI model , published in 1984. For a period in the late 1980s and early 1990s, engineers, organizations and nations became polarized over the issue of which standard , the OSI model or the Internet protocol suite, would result in the best and most robust computer networks. The information exchanged between devices through a network or other media
1869-532: A server or client (e.g. smart TV) appearing after power on, and then disappearing after a few minutes (often 30 by default configuration) due to IGMP group membership expiring. On 8 June 2020, yet another protocol design flaw was announced. Dubbed "CallStranger" by its discoverer, it allows an attacker to subvert the event subscription mechanism and execute a variety of attacks: amplification of requests for use in DDoS; enumeration; and data exfiltration. OCF had published
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#17330848864921958-422: A service to UPnP AV client devices, so-called control points , for browsing the media content of the server and request the media server to deliver a file to the control point for playback. UPnP media servers are available for most operating systems and many hardware platforms. UPnP AV media servers can either be categorized as software -based or hardware-based. Software-based UPnP AV media servers can be run on
2047-478: A set of cooperating processes that manipulate shared data to communicate with each other. This communication is governed by well-understood protocols, which can be embedded in the process code itself. In contrast, because there is no shared memory , communicating systems have to communicate with each other using a shared transmission medium . Transmission is not necessarily reliable, and individual systems may use different hardware or operating systems. To implement
2136-649: A single communication. A group of protocols designed to work together is known as a protocol suite; when implemented in software they are a protocol stack . Internet communication protocols are published by the Internet Engineering Task Force (IETF). The IEEE (Institute of Electrical and Electronics Engineers) handles wired and wireless networking and the International Organization for Standardization (ISO) handles other types. The ITU-T handles telecommunications protocols and formats for
2225-456: A standardization process. Such protocols are referred to as de facto standards . De facto standards are common in emerging markets, niche markets, or markets that are monopolized (or oligopolized ). They can hold a market in a very negative grip, especially when used to scare away competition. From a historical perspective, standardization should be seen as a measure to counteract the ill-effects of de facto standards. Positive exceptions exist;
2314-430: A transfer mechanism of a protocol is comparable to a central processing unit (CPU). The framework introduces rules that allow the programmer to design cooperating protocols independently of one another. In modern protocol design, protocols are layered to form a protocol stack. Layering is a design principle that divides the protocol design task into smaller steps, each of which accomplishes a specific part, interacting with
2403-507: A variety of actions, including retrieving the external IP address of the device, enumerating existing port mappings, and adding or removing port mappings. By adding a port mapping, a UPnP controller behind the IGD can enable traversal of the IGD from an external address to an internal client. There are numerous compatibility issues due the different interpretations of the very large actually backward compatible IGDv1 and IGDv2 specifications. One of them
2492-508: Is a distributed, open architecture protocol based on established standards such as the Internet Protocol Suite (TCP/IP), HTTP , XML , and SOAP . UPnP control points (CPs) are devices which use UPnP protocols to control UPnP controlled devices (CDs). The UPnP architecture supports zero-configuration networking. A UPnP-compatible device from any vendor can dynamically join a network, obtain an IP address, announce its name, advertise or convey its capabilities upon request, and learn about
2581-403: Is a set of networking protocols on the Internet Protocol (IP) 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 on the network and establish functional network services. UPnP is intended primarily for residential networks without enterprise-class devices. UPnP assumes
2670-560: Is expressed in XML and includes vendor-specific manufacturer information like the model name and number, serial number , manufacturer name, (presentation) URLs to vendor-specific web sites, etc. The description also includes a list of any embedded services. For each service, the Device Description document lists the URLs for control, eventing and service description. Each service description includes
2759-453: Is governed by rules and conventions that can be set out in communication protocol specifications. The nature of communication, the actual data exchanged and any state -dependent behaviors, is defined by these specifications. In digital computing systems, the rules can be expressed by algorithms and data structures . Protocols are to communication what algorithms or programming languages are to computations. Operating systems usually contain
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2848-492: Is not officially supported by Microsoft and requires manual tweaking of NT Services' dependencies in order to run. WMC 1.0 was originally released as an out-of-band update to Windows XP , which could stream only Windows Media files. Version 2.0 added support for UNC paths and removable devices as well as enhanced support for media formats, including ASF . Future versions were not released as stand-alone applications, but integrated into Windows Media Player , where it powers
2937-430: Is optional for UPnP enabled routers. As a result, some UPnP devices ship with UPnP turned off by default as a security measure. In 2011, researcher Daniel Garcia developed a tool designed to exploit a flaw in some UPnP IGD device stacks that allow UPnP requests from the Internet. The tool was made public at DEFCON 19 and allows portmapping requests to external IP addresses from the device and internal IP addresses behind
3026-449: Is referred to as communicating sequential processes (CSP). Concurrency can also be modeled using finite state machines , such as Mealy and Moore machines . Mealy and Moore machines are in use as design tools in digital electronics systems encountered in the form of hardware used in telecommunication or electronic devices in general. The literature presents numerous analogies between computer communication and programming. In analogy,
3115-592: Is the UPnP IGD client integrated with current Microsoft Windows and Xbox systems with certified IGDv2 routers. The compatibility issue still exist since the introduced of the IGDv1 client in Windows XP in 2001, and a IGDv2 router without a workaround that makes router port mapping impossible. If UPnP is only used to control router port mappings and pinholes, there are alternative, newer much simpler and lightweight protocols such as
3204-408: Is the synchronization of software for receiving and transmitting messages of communication in proper sequencing. Concurrent programming has traditionally been a topic in operating systems theory texts. Formal verification seems indispensable because concurrent programs are notorious for the hidden and sophisticated bugs they contain. A mathematical approach to the study of concurrency and communication
3293-594: Is typically independent of how it is to be implemented . Communication protocols have to be agreed upon by the parties involved. To reach an agreement, a protocol may be developed into a technical standard . A programming language describes the same for computations, so there is a close analogy between protocols and programming languages: protocols are to communication what programming languages are to computations . An alternate formulation states that protocols are to communication what algorithms are to computation . Multiple protocols often describe different aspects of
3382-744: The National Physical Laboratory in the United Kingdom, it was written by Roger Scantlebury and Keith Bartlett for the NPL network . On the ARPANET , the starting point for host-to-host communication in 1969 was the 1822 protocol , written by Bob Kahn , which defined the transmission of messages to an IMP. The Network Control Program (NCP) for the ARPANET, developed by Steve Crocker and other graduate students including Jon Postel and Vint Cerf ,
3471-581: The Network Sharing Service feature. WMP 11 in Windows XP contains WMC 3.0, and in Windows Vista it contains WMC 4.0; the Windows Vista version of WMP 11 includes a WMC client as well. While WMC 3.0 and WMC 4.0 offer similar feature-set, they are built using different codebases. With WMP integration, WMC can make available the entire media library managed by WMP. When a shared library is browsed by
3560-423: The OSI model . At the time the Internet was developed, abstraction layering had proven to be a successful design approach for both compiler and operating system design and, given the similarities between programming languages and communication protocols, the originally monolithic networking programs were decomposed into cooperating protocols. This gave rise to the concept of layered protocols which nowadays forms
3649-586: The Open Connectivity Foundation (OCF). In the fall of 2008, the UPnP Forum ratified the successor to UPnP 1.0 Device Architecture, UPnP 1.1. The Devices Profile for Web Services (DPWS) standard was a candidate successor to UPnP, but UPnP 1.1 was selected by the UPnP Forum. Version 2 of IGD is standardized. The UPnP Internet Gateway Device (IGD) standard has a WANIPConnection service, which provides similar functionality to IETF -standard Port Control Protocol . The NAT-PMP specification contains
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3738-612: The PARC Universal Packet (PUP) for internetworking. Research in the early 1970s by Bob Kahn and Vint Cerf led to the formulation of the Transmission Control Program (TCP). Its RFC 675 specification was written by Cerf with Yogen Dalal and Carl Sunshine in December 1974, still a monolithic design at this time. The International Network Working Group agreed on a connectionless datagram standard which
3827-793: The PCP and the NAT-PMP , both of which have been standardized as RFCs by the IETF. These alternatives are not yet known to have compatibility issues between different clients and servers, but adoption is still low. For consumer routers, only AVM and the open-source router software projects OpenWrt , OPNsense , and pfSense are currently known to support PCP as an alternative to UPnP. AVM 's Fritz!Box UPnP IGDv2 and PCP implementation has been very buggy since its introduction. In many cases it does not work. The UPnP protocol, by default, does not implement any authentication , so UPnP device implementations must implement
3916-543: The finger protocol . Text-based protocols are typically optimized for human parsing and interpretation and are therefore suitable whenever human inspection of protocol contents is required, such as during debugging and during early protocol development design phases. A binary protocol utilizes all values of a byte , as opposed to a text-based protocol which only uses values corresponding to human-readable characters in ASCII encoding. Binary protocols are intended to be read by
4005-521: The public switched telephone network (PSTN). As the PSTN and Internet converge , the standards are also being driven towards convergence. The first use of the term protocol in a modern data-commutation context occurs in April 1967 in a memorandum entitled A Protocol for Use in the NPL Data Communications Network. Under the direction of Donald Davies , who pioneered packet switching at
4094-581: The MediaServer and MediaRenderer device classes, allowing a higher level of interoperability between products made by different manufacturers. Some of the early devices complying with these standards were marketed by Philips under the Streamium brand name. Since 2006, versions 3 and 4 of the UPnP audio and video device control protocols have been published. In March 2013, an updated uPnP AV architecture specification
4183-542: The NAT. The problem is widely propagated around the world, with scans showing millions of vulnerable devices at a time. In January 2013, the security company Rapid7 in Boston reported on a six-month research programme. A team scanned for signals from UPnP-enabled devices announcing their availability for internet connection. Some 6900 network-aware products from 1500 companies at 81 million IP-addresses responded to their requests. 80% of
4272-507: The WMC standalone client (available as part of WMC 2.0) can give an enhanced experience. The query results for the list of media contain certain metadata about the files as well, including media type, dates, rating, keywords for artist, albums etc. It also contains shared playlists. A WMC client uses these metadata to present the media items categorically for browsing. The top-level menu in a WMC client has containers for Audio , Video , Pictures and Playlists , and sub-menus further categorize
4361-548: The WMP client, it can be browsed, filtered and sorted like a regular WMP media library. On Windows XP by default, Windows Media Connect 2.0 does not work after Windows Media Player 11 has been installed, although Windows Media Player 11 only includes the UPnP AV server and does not include the client. WMC is a UPnP AV server that can make media files stored on a computer available to UPnP AV -compatible digital media receiver clients over
4450-457: The actual UPnP specifications. UPnP uses UDP port 1900, and all used TCP ports are derived from the SSDP alive and response messages. The foundation for UPnP networking is IP addressing. Each device must implement a DHCP client and search for a DHCP server when the device is first connected to the network. If no DHCP server is available, the device must assign itself an address. The process by which
4539-529: The additional Device Protection service, or implement the Device Security Service . There also exists a non-standard solution called UPnP-UP (Universal Plug and Play - User Profile) which proposes an extension to allow user authentication and authorization mechanisms for UPnP devices and applications. Many UPnP device implementations lack authentication mechanisms, and by default assume local systems and their users are completely trustworthy. When
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#17330848864924628-456: The approval or support of a standards organization , which initiates the standardization process. The members of the standards organization agree to adhere to the work result on a voluntary basis. Often the members are in control of large market shares relevant to the protocol and in many cases, standards are enforced by law or the government because they are thought to serve an important public interest, so getting approval can be very important for
4717-435: The authentication mechanisms are not implemented, routers and firewalls running the UPnP IGD protocol are vulnerable to attack. For example, Adobe Flash programs running outside the sandbox of the browser (e.g. this requires specific version of Adobe Flash with acknowledged security issues) are capable of generating a specific type of HTTP request which allows a router implementing the UPnP IGD protocol to be controlled by
4806-448: The basis of protocol design. Systems typically do not use a single protocol to handle a transmission. Instead they use a set of cooperating protocols, sometimes called a protocol suite . Some of the best-known protocol suites are TCP/IP , IPX/SPX , X.25 , AX.25 and AppleTalk . The protocols can be arranged based on functionality in groups, for instance, there is a group of transport protocols . The functionalities are mapped onto
4895-442: The content being carried: text-based and binary. A text-based protocol or plain text protocol represents its content in human-readable format , often in plain text encoded in a machine-readable encoding such as ASCII or UTF-8 , or in structured text-based formats such as Intel hex format , XML or JSON . The immediate human readability stands in contrast to native binary protocols which have inherent benefits for use in
4984-481: The device should use that name in subsequent network operations; otherwise, the device should use its IP address. Once a device has established an IP address, the next step in UPnP networking is discovery. The UPnP discovery protocol is known as the Simple Service Discovery Protocol (SSDP). When a device is added to the network, SSDP allows that device to advertise its services to control points on
5073-461: The devices are home routers; others include printers, webcams and surveillance cameras. Using the UPnP-protocol, many of those devices can be accessed and/or manipulated. In February 2013, the UPnP forum responded in a press release by recommending more recent versions of the used UPnP stacks, and by improving the certification program to include checks to avoid further such issues. UPnP is often
5162-542: The entertainment content, including MPEG2, MPEG4, JPEG, MP3, Windows Media Audio (WMA), bitmaps (BMP), and NTSC, PAL or ATSC formats. Multiple types of transfer protocols are supported, including IEEE 1394, HTTP, RTP and TCP/IP. On 12 July 2006, the UPnP Forum announced the release of version 2 of the UPnP Audio and Video specifications, with new MediaServer (MS) version 2.0 and MediaRenderer (MR) version 2.0 classes. These enhancements are created by adding capabilities to
5251-673: The field of computer networking, it has been historically criticized by many researchers as abstracting the protocol stack in this way may cause a higher layer to duplicate the functionality of a lower layer, a prime example being error recovery on both a per-link basis and an end-to-end basis. Commonly recurring problems in the design and implementation of communication protocols can be addressed by software design patterns . Popular formal methods of describing communication syntax are Abstract Syntax Notation One (an ISO standard) and augmented Backus–Naur form (an IETF standard). Finite-state machine models are used to formally describe
5340-426: The horizontal message flows (and protocols) are between systems. The message flows are governed by rules, and data formats specified by protocols. The blue lines mark the boundaries of the (horizontal) protocol layers. The software supporting protocols has a layered organization and its relationship with protocol layering is shown in figure 5. To send a message on system A, the top-layer software module interacts with
5429-643: The internet as a reference model for general communication with much stricter rules of protocol interaction and rigorous layering. Typically, application software is built upon a robust data transport layer. Underlying this transport layer is a datagram delivery and routing mechanism that is typically connectionless in the Internet. Packet relaying across networks happens over another layer that involves only network link technologies, which are often specific to certain physical layer technologies, such as Ethernet . Layering provides opportunities to exchange technologies when needed, for example, protocols are often stacked in
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#17330848864925518-476: The layers make up a layering scheme or model. Computations deal with algorithms and data; Communication involves protocols and messages; So the analog of a data flow diagram is some kind of message flow diagram. To visualize protocol layering and protocol suites, a diagram of the message flows in and between two systems, A and B, is shown in figure 3. The systems, A and B, both make use of the same protocol suite. The vertical flows (and protocols) are in-system and
5607-427: The layers, each layer solving a distinct class of problems relating to, for instance: application-, transport-, internet- and network interface-functions. To transmit a message, a protocol has to be selected from each layer. The selection of the next protocol is accomplished by extending the message with a protocol selector for each layer. There are two types of communication protocols, based on their representation of
5696-547: The list the media to be played, the media file is streamed to the client for playing. Pictures are streamed using HTTP , different protocols are used for music and video . A client supporting the UPnP Media Renderer standard will be able to render the stream. While any UPnP AV client can act as a client, using a dedicated WMC client, like the Xbox 360 and PlayStation 3 , Zune music player, WMP 11 in Windows Vista or
5785-405: The media. Client-side playlists can be created out of these shared files as well. When the WMC 11 client is used to access a library shared by WMC 3.0 or WMC 4.0, it lists the media files as a Shared Library using the same library view it uses to organize local media files, complete with album art and thumbnails. UPnP#UPnP AV (Audio and Video) standards Universal Plug and Play ( UPnP )
5874-402: The module directly below it and hands over the message to be encapsulated. The lower module fills in the header data in accordance with the protocol it implements and interacts with the bottom module which sends the message over the communications channel to the bottom module of system B. On the receiving system B the reverse happens, so ultimately the message gets delivered in its original form to
5963-514: The multicast foundation makes it chatty, consuming too many network resources on networks with a large population of devices; the simplified access controls do not map well to complex environments; and it does not provide a uniform configuration syntax such as the CLI environments of Cisco IOS or JUNOS. The UPnP architecture allows device-to-device networking of consumer electronics , mobile devices, personal computers , and networked home appliances . It
6052-456: The names and values for all evented variables and allows the subscriber to initialize its model of the state of the service. To support scenarios with multiple control points, eventing is designed to keep all control points equally informed about the effects of any action. Therefore, all subscribers are sent all event messages, subscribers receive event messages for all "evented" variables that have changed, and event messages are sent no matter why
6141-686: The network must run Internet Protocol (IP) and then uses HTTP , SOAP and XML on top of IP, in order to provide device/service description, actions, data transfer and eventing. Device search requests and advertisements are supported by running HTTP on top of UDP using multicast (known as HTTPMU). Responses to search requests are also sent over UDP, but are instead sent using unicast (known as HTTPU). UPnP uses UDP due to its lower overhead in not requiring confirmation of received data and retransmission of corrupt packets. HTTPU and HTTPMU were initially submitted as an Internet Draft , but it expired in 2001; these specifications have since been integrated into
6230-493: The network runs IP, and then uses HTTP on top of IP to provide device/service description, actions, data transfer and event notification . Device search requests and advertisements are supported by running HTTP on top of UDP ( port 1900) using multicast (known as HTTPMU). Responses to search requests are also sent over UDP, but are instead sent using unicast (known as HTTPU). Conceptually, UPnP extends plug and play —a technology for dynamically attaching devices directly to
6319-420: The network. This is achieved by sending SSDP alive messages. When a control point is added to the network, SSDP allows that control point to actively search for devices of interest on the network or listen passively to the SSDP alive messages of devices. The fundamental exchange is a discovery message containing a few essential specifics about the device or one of its services, for example, its type, identifier, and
6408-511: The only significant multicast application in use in digital home networks; therefore, multicast network misconfiguration or other deficiencies can appear as UPnP issues rather than underlying network issues. If IGMP snooping is enabled on a switch, or more commonly a wireless router/switch, it will interfere with UPnP/DLNA device discovery (SSDP) if incorrectly or incompletely configured (e.g. without an active querier or IGMP proxy), making UPnP appear unreliable. Typical scenarios observed include
6497-465: The other parts of the protocol only in a small number of well-defined ways. Layering allows the parts of a protocol to be designed and tested without a combinatorial explosion of cases, keeping each design relatively simple. The communication protocols in use on the Internet are designed to function in diverse and complex settings. Internet protocols are designed for simplicity and modularity and fit into
6586-457: The possible interactions of the protocol. and communicating finite-state machines For communication to occur, protocols have to be selected. The rules can be expressed by algorithms and data structures. Hardware and operating system independence is enhanced by expressing the algorithms in a portable programming language. Source independence of the specification provides wider interoperability. Protocol standards are commonly created by obtaining
6675-533: The presence and capabilities of other devices. Dynamic Host Configuration Protocol (DHCP) and Domain Name System (DNS) servers are optional and are only used if they are available on the network. Devices can disconnect from the network automatically without leaving state information. UPnP was published as a 73-part international standard ISO/IEC 29341 in December 2008. Other UPnP features include: UPnP uses common Internet technologies. It assumes
6764-401: The protocol, creating incompatible versions on their networks. In some cases, this was deliberately done to discourage users from using equipment from other manufacturers. There are more than 50 variants of the original bi-sync protocol. One can assume, that a standard would have prevented at least some of this from happening. In some cases, protocols gain market dominance without going through
6853-526: The protocol. The need for protocol standards can be shown by looking at what happened to the Binary Synchronous Communications (BSC) protocol invented by IBM . BSC is an early link-level protocol used to connect two separate nodes. It was originally not intended to be used in a multinode network, but doing so revealed several deficiencies of the protocol. In the absence of standardization, manufacturers and organizations felt free to enhance
6942-445: The rules, syntax , semantics , and synchronization of communication and possible error recovery methods . Protocols may be implemented by hardware , software , or a combination of both. Communicating systems use well-defined formats for exchanging various messages. Each message has an exact meaning intended to elicit a response from a range of possible responses predetermined for that particular situation. The specified behavior
7031-458: The service at run time. The service publishes updates when these variables change, and a control point may subscribe to receive this information. The service publishes updates by sending event messages. Event messages contain the names of one or more state variables and the current value of those variables. These messages are also expressed in XML. A special initial event message is sent when a control point first subscribes; this event message contains
7120-427: The specific capabilities of the presentation page and device. UPnP AV architecture is an audio and video extension of the UPnP, supporting a variety of devices such as TVs, VCRs, CD/DVD players/jukeboxes, settop boxes, stereos systems, MP3 players, still image cameras, camcorders, electronic picture frames (EPFs), and personal computers. The UPnP AV architecture allows devices to support different types of formats for
7209-484: The state variable changed (either in response to a requested action or because the state the service is modeling changed). The final step in UPnP networking is presentation. If a device has a URL for presentation, then the control point can retrieve a page from this URL, load the page into a web browser , and depending on the capabilities of the page, allow a user to control the device and/or view device status. The degree to which each of these can be accomplished depends on
7298-510: The top module of system B. Program translation is divided into subproblems. As a result, the translation software is layered as well, allowing the software layers to be designed independently. The same approach can be seen in the TCP/IP layering. The modules below the application layer are generally considered part of the operating system. Passing data between these modules is much less expensive than passing data between an application program and
7387-506: The transmission. In general, much of the following should be addressed: Systems engineering principles have been applied to create a set of common network protocol design principles. The design of complex protocols often involves decomposition into simpler, cooperating protocols. Such a set of cooperating protocols is sometimes called a protocol family or a protocol suite, within a conceptual framework. Communicating systems operate concurrently. An important aspect of concurrent programming
7476-406: The transport layer. The boundary between the application layer and the transport layer is called the operating system boundary. Strictly adhering to a layered model, a practice known as strict layering, is not always the best approach to networking. Strict layering can have a negative impact on the performance of an implementation. Although the use of protocol layering is today ubiquitous across
7565-408: The variables that describe the run-time state of the service. Another capability of UPnP networking is event notification , or eventing . The event notification protocol defined in the UPnP Device Architecture is known as General Event Notification Architecture (GENA). A UPnP description for a service includes a list of actions the service responds to and a list of variables that model the state of
7654-415: Was first implemented in 1970. The NCP interface allowed application software to connect across the ARPANET by implementing higher-level communication protocols, an early example of the protocol layering concept. The CYCLADES network, designed by Louis Pouzin in the early 1970s was the first to implement the end-to-end principle , and make the hosts responsible for the reliable delivery of data on
7743-580: Was presented to the CCITT in 1975 but was not adopted by the CCITT nor by the ARPANET. Separate international research, particularly the work of Rémi Després , contributed to the development of the X.25 standard, based on virtual circuits , which was adopted by the CCITT in 1976. Computer manufacturers developed proprietary protocols such as IBM's Systems Network Architecture (SNA), Digital Equipment Corporation's DECnet and Xerox Network Systems . TCP software
7832-454: Was published, incorporating the updated device control protocols. UPnP Device Architecture 2.0 was released in April 2020. The UPnP AV standards have been referenced in specifications published by other organizations including Digital Living Network Alliance Networked Device Interoperability Guidelines, International Electrotechnical Commission IEC 62481-1, and Cable Television Laboratories OpenCable Home Networking Protocol. Generally
7921-516: Was redesigned as a modular protocol stack, referred to as TCP/IP. This was installed on SATNET in 1982 and on the ARPANET in January 1983. The development of a complete Internet protocol suite by 1989, as outlined in RFC 1122 and RFC 1123 , laid the foundation for the growth of TCP/IP as a comprehensive protocol suite as the core component of the emerging Internet . International work on
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