Session Initiation Protocol
The Session Initiation Protocol is a signaling protocol used for initiating and terminating real-time sessions that include voice and messaging applications. SIP is used for signaling and controlling multimedia communication sessions in applications of Internet telephony for voice and video calls, in private IP telephone systems, in instant messaging over Internet Protocol networks as well as mobile phone calling over LTE; the protocol defines the specific format of messages exchanged and the sequence of communications for cooperation of the participants. SIP is a text-based protocol, incorporating many elements of the Hypertext Transfer Protocol and the Simple Mail Transfer Protocol. A call established with SIP may consist of multiple media streams, but no separate streams are required for applications, such as text messaging, that exchange data as payload in the SIP message. SIP works in conjunction with several other protocols that carry the session media. Most media type and parameter negotiation and media setup is performed with the Session Description Protocol, carried as payload in SIP messages.
SIP is designed to be independent of the underlying transport layer protocol, can be used with the User Datagram Protocol, the Transmission Control Protocol, the Stream Control Transmission Protocol. For secure transmissions of SIP messages over insecure network links, the protocol may be encrypted with Transport Layer Security. For the transmission of media streams the SDP payload carried in SIP messages employs the Real-time Transport Protocol or the Secure Real-time Transport Protocol. SIP was designed by Mark Handley, Henning Schulzrinne, Eve Schooler and Jonathan Rosenberg in 1996; the protocol was standardized as RFC 2543 in 1999. In November 2000, SIP was accepted as a 3GPP signaling protocol and permanent element of the IP Multimedia Subsystem architecture for IP-based streaming multimedia services in cellular networks. In June 2002 the specification was revised in RFC 3261 and various extensions and clarifications have been published since. SIP was designed to provide a signaling and call setup protocol for IP-based communications supporting the call processing functions and features present in the public switched telephone network with a vision of supporting new multimedia applications.
It has been extended for video conferencing, streaming media distribution, instant messaging, presence information, file transfer, Internet fax and online games. SIP is distinguished by its proponents for having roots in the Internet community rather than in the telecommunications industry. SIP has been standardized by the IETF, while other protocols, such as H.323, have traditionally been associated with the International Telecommunication Union. SIP is only involved for the signaling operations of a media communication session and is used to set up and terminate voice or video calls. SIP can be used to establish multiparty sessions, it allows modification of existing calls. The modification can involve changing addresses or ports, inviting more participants, adding or deleting media streams. SIP has found applications in messaging applications, such as instant messaging, event subscription and notification. SIP works in conjunction with several other protocols that specify the media format and coding and that carry the media once the call is set up.
For call setup, the body of a SIP message contains a Session Description Protocol data unit, which specifies the media format and media communication protocol. Voice and video media streams are carried between the terminals using the Real-time Transport Protocol or Secure Real-time Transport Protocol; every resource of a SIP network, such as user agents, call routers, voicemail boxes, are identified by a Uniform Resource Identifier. The syntax of the URI follows the general standard syntax used in Web services and e-mail; the URI scheme used for SIP is sip and a typical SIP URI has the form sip:username@domainname or sip:username@hostport, where domainname requires DNS SRV records to locate the servers for SIP domain while hostport can be an IP address or a qualified domain name of the host and port. If secure transmission is required, the scheme sips is used. SIP employs design elements similar to the HTTP request/response transaction model; each transaction consists of a client request that invokes a particular method or function on the server and at least one response.
SIP reuses most of the header fields, encoding rules and status codes of HTTP, providing a readable text-based format. SIP can be carried by several transport layer protocols including Transmission Control Protocol, User Datagram Protocol, Stream Control Transmission Protocol. SIP clients use TCP or UDP on port numbers 5060 or 5061 for SIP traffic to servers and other endpoints. Port 5060 is used for non-encrypted signaling traffic whereas port 5061 is used for traffic encrypted with Transport Layer Security. SIP-based telephony networks implement call processing features of Signaling System 7, for which special SIP protocol extensions exist, although the two protocols themselves are different. SS7 is a centralized protocol, characterized by a complex central network architecture and dumb endpoints. SIP is a client-server protocol of equipotent peers. SIP features are implemented in the communicating endpoints, while the traditional SS7 architecture is in use only between switching centers; the network elements that use the Session Initiation Protocol for commun
A media gateway is a translation device or service that converts media streams between disparate telecommunications technologies such as POTS, SS7, Next Generation Networks or private branch exchange systems. Media gateways enable multimedia communications across packet networks using transport protocols such as Asynchronous Transfer Mode and Internet Protocol; because the media gateway connects different types of networks, one of its main functions is to convert between different transmission and coding techniques. Media streaming functions such as echo cancellation, DTMF, tone sender are located in the media gateway. Media gateways are controlled by a separate Media Gateway Controller which provides the call control and signaling functionality. Communication between media gateways and Call Agents is achieved by means of protocols such as MGCP or Megaco or Session Initiation Protocol. Modern media gateways used with SIP are stand-alone units with their own call and signaling control integrated and can function as independent, intelligent SIP end-points.
Voice over Internet Protocol media gateways perform the conversion between Time-division multiplexing voice to a media streaming protocol, such as the Real-time Transport Protocol, as well as a signaling protocol used in the VoIP system. Mobile access media gateways connect the radio access networks of a public land mobile network PLMN to a next-generation core network. 3GPP standards define the functionality of IMS-MGW for UTRAN and GERAN based PLMNs. Signaling gateway
Telecommunication is the transmission of signs, messages, writings and sounds or information of any nature by wire, optical or other electromagnetic systems. Telecommunication occurs when the exchange of information between communication participants includes the use of technology, it is transmitted either electrically over physical media, such as cables, or via electromagnetic radiation. Such transmission paths are divided into communication channels which afford the advantages of multiplexing. Since the Latin term communicatio is considered the social process of information exchange, the term telecommunications is used in its plural form because it involves many different technologies. Early means of communicating over a distance included visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, optical heliographs. Other examples of pre-modern long-distance communication included audio messages such as coded drumbeats, lung-blown horns, loud whistles. 20th- and 21st-century technologies for long-distance communication involve electrical and electromagnetic technologies, such as telegraph and teleprinter, radio, microwave transmission, fiber optics, communications satellites.
A revolution in wireless communication began in the first decade of the 20th century with the pioneering developments in radio communications by Guglielmo Marconi, who won the Nobel Prize in Physics in 1909, other notable pioneering inventors and developers in the field of electrical and electronic telecommunications. These included Charles Wheatstone and Samuel Morse, Alexander Graham Bell, Edwin Armstrong and Lee de Forest, as well as Vladimir K. Zworykin, John Logie Baird and Philo Farnsworth; the word telecommunication is a compound of the Greek prefix tele, meaning distant, far off, or afar, the Latin communicare, meaning to share. Its modern use is adapted from the French, because its written use was recorded in 1904 by the French engineer and novelist Édouard Estaunié. Communication was first used as an English word in the late 14th century, it comes from Old French comunicacion, from Latin communicationem, noun of action from past participle stem of communicare "to share, divide out.
Homing pigeons have been used throughout history by different cultures. Pigeon post had Persian roots, was used by the Romans to aid their military. Frontinus said; the Greeks conveyed the names of the victors at the Olympic Games to various cities using homing pigeons. In the early 19th century, the Dutch government used the system in Sumatra, and in 1849, Paul Julius Reuter started a pigeon service to fly stock prices between Aachen and Brussels, a service that operated for a year until the gap in the telegraph link was closed. In the Middle Ages, chains of beacons were used on hilltops as a means of relaying a signal. Beacon chains suffered the drawback that they could only pass a single bit of information, so the meaning of the message such as "the enemy has been sighted" had to be agreed upon in advance. One notable instance of their use was during the Spanish Armada, when a beacon chain relayed a signal from Plymouth to London. In 1792, Claude Chappe, a French engineer, built the first fixed visual telegraphy system between Lille and Paris.
However semaphore suffered from the need for skilled operators and expensive towers at intervals of ten to thirty kilometres. As a result of competition from the electrical telegraph, the last commercial line was abandoned in 1880. On 25 July 1837 the first commercial electrical telegraph was demonstrated by English inventor Sir William Fothergill Cooke, English scientist Sir Charles Wheatstone. Both inventors viewed their device as "an improvement to the electromagnetic telegraph" not as a new device. Samuel Morse independently developed a version of the electrical telegraph that he unsuccessfully demonstrated on 2 September 1837, his code was an important advance over Wheatstone's signaling method. The first transatlantic telegraph cable was completed on 27 July 1866, allowing transatlantic telecommunication for the first time; the conventional telephone was invented independently by Alexander Bell and Elisha Gray in 1876. Antonio Meucci invented the first device that allowed the electrical transmission of voice over a line in 1849.
However Meucci's device was of little practical value because it relied upon the electrophonic effect and thus required users to place the receiver in their mouth to "hear" what was being said. The first commercial telephone services were set-up in 1878 and 1879 on both sides of the Atlantic in the cities of New Haven and London. Starting in 1894, Italian inventor Guglielmo Marconi began developing a wireless communication using the newly discovered phenomenon of radio waves, showing by 1901 that they could be transmitted across the Atlantic Ocean; this was the start of wireless telegraphy by radio. Voice and music had little early success. World War I accelerated the development of radio for military communications. After the war, commercial radio AM broadcasting began in the 1920s and became an important mass medium for entertainment and news. World War II again accelerated development of radio for the wartime purposes of aircraft and land communication, radio navigation and radar. Development of stereo FM broadcasting of radio
Windows Mobile is a discontinued family of mobile operating systems developed by Microsoft for smartphones and Pocket PCs. Its origin dated back to Windows CE in 1996, though Windows Mobile itself first appeared in 2000 as PocketPC 2000, it was renamed "Windows Mobile" in 2003, at which point it came in several versions and was aimed at business and enterprise consumers. It became one of the most popular mobile operating systems as of the mid-2000s, but its popularity faded in the following years, by February 2010, facing competition from rival mobile OSs, including Apple's iOS and Android, Microsoft announced Windows Phone to supersede Windows Mobile; as a result, Windows Mobile has been deprecated. Windows Phone is incompatible with software; the last version of Windows Mobile, released after the announcement of Windows Phone, was 6.5.5. After this, Microsoft ceased development on Windows Mobile, in order to concentrate on Windows Phone. Most versions of Windows Mobile have a standard set of features, such as multitasking and the ability to navigate a file system similar to that of Windows 9x and Windows NT, including support for many of the same file types.
To its desktop counterpart, it comes bundled with a set of applications that perform basic tasks. Internet Explorer Mobile is the default web browser, Windows Media Player is the default media player used for playing digital media; the mobile version of Microsoft Office, is the default office suite. Internet Connection Sharing, supported on compatible devices, allows the phone to share its Internet connection with computers via USB and Bluetooth. Windows Mobile supports virtual private networking over PPTP protocol. Most devices with mobile connectivity have a Radio Interface Layer; the Radio Interface Layer provides the system interface between the Cell Core layer within the Windows Mobile OS and the radio protocol stack used by the wireless modem hardware. This allows OEMs to integrate a variety of modems into their equipment; the user interface changed between versions, only retaining similar functionality. The Today Screen called the Home Screen, shows the current date, owner information, upcoming appointments, e-mails, tasks.
The taskbar display the current time as well as the volume level. Devices with a cellular radio show the signal strength on said taskbar. Windows Mobile is based on the Windows CE kernel and first appeared as the Pocket PC 2000 operating system, it includes a suite of basic applications developed with the Microsoft Windows API, is designed to have features and appearance somewhat similar to desktop versions of Windows. It allowed third party developers to develop software for Windows Mobile with no restrictions imposed by Microsoft. Software applications were purchasable from Windows Marketplace for Mobile during the service's lifespan. Most early Windows Mobile devices came with a stylus, which can be used to enter commands by tapping it on the screen; the primary touch input technology behind most devices were resistive touchscreens which required a stylus for input. Devices used capacitive sensing which does not require a stylus. Along with touchscreens, a large variety of form factors existed for the platform.
Some devices featured slideout keyboards. Microsoft's work on handheld portable devices began with research projects in 1990, with the work on Windows CE beginning in 1992; the OS and the user interface were developed separately. With Windows CE being based on Windows 95 code and a separate team handing the user interface, codenamed WinPad. Windows 95 had strong pen support making porting easy, it is treating pens right for the first time." WinPad was delayed due to price and performance issues, before being scrapped in early 1995 due to touchscreen driver problems relating to WriteTouch technology, made by NCR Microelectronic Products. Although WinPad was never released as a consumer product, Alpha builds were released showcasing many interface elements. During development of WinPad a separate team worked on a project called Pulsar; this project was canceled around the same time as WinPad. The two disbanded groups would form the Pegasus project in 1995. Pegasus would work on the hardware side of the Windows CE OS, attempting to create a form factor similar to a PC-esque PDA like WinPad, with communications functionality like Pulsar.
A hardware reference guide was created and devices began shipping in 1996, although most of these device bore little resemblance to the goal of a pen-based touchscreen handheld device. Pocket PC 2000 codenamed "Rapier", was released on April 19, 2000, was based on the Windows CE 3.0 kernel. It was the debut of what was dubbed the Windows Mobile operating system, meant to be a successor to the operating system aboard Palm-Size PCs, it retained backwards compatibility with such Palm-Size PC applications. Pocket PC 2000 was intended for Pocket PC devices. While, several Pocket PC 2000 phones were released, Microsoft's smartphone hardware platform was not yet created; the only resolution supported by this release was 240×320. Removable storage card formats that were supported were MultiMediaCard. At this time Pocket PC devices had not been standardized with a specific CPU architecture; as a result, Pocket PC 2000 was released on multiple CPU architectures. Infrared File beaming capability was amo
IPhone is a line of smartphones designed and marketed by Apple Inc. All generations of the iPhone use Apple's iOS mobile operating system software; the first-generation iPhone was released on June 29, 2007, multiple new hardware iterations with new iOS releases have been released since. The user interface is built around the device's multi-touch screen, including a virtual keyboard; the iPhone can connect to cellular networks. An iPhone can shoot video, take photos, play music and receive email, browse the web and receive text messages, follow GPS navigation, record notes, perform mathematical calculations, receive visual voicemail. Other functionality, such as video games, reference works, social networking, can be enabled by downloading mobile apps; as of January 2017, Apple's App Store contained more than 2.2 million applications available for the iPhone. Apple has released twelve generations of iPhone models, each accompanied by one of the twelve major releases of the iOS operating system.
The original first-generation iPhone was a GSM phone and established design precedents, such as a button placement that has persisted throughout all releases and a screen size maintained for the next four iterations. The iPhone 3G added 3G network support, was followed by the 3GS with improved hardware, the 4 with a metal chassis, higher display resolution and front-facing camera, the 4S with improved hardware and the voice assistant Siri; the iPhone 5 featured Apple's newly introduced Lightning connector. In 2013, Apple released the 5S with improved hardware and a fingerprint reader, the lower-cost 5C, a version of the 5 with colored plastic casings instead of metal, they were followed by the larger iPhone 6, with models featuring 4.7-and-5.5-inch displays. The iPhone 6S was introduced the following year, which featured hardware upgrades and support for pressure-sensitive touch inputs, as well as the SE—which featured hardware from the 6S but the smaller form factor of the 5S. In 2016, Apple unveiled the iPhone 7 and 7 Plus, which add water resistance, improved system and graphics performance, a new rear dual-camera setup on the Plus model, new color options, while removing the 3.5 mm headphone jack found on previous models.
The iPhone 8 and 8 Plus were released in 2017, adding a glass back and an improved screen and camera. The iPhone X was released alongside the 8 and 8 Plus, with its highlights being a near bezel-less design, an improved camera and a new facial recognition system, named Face ID, but having no home button, therefore, no Touch ID. In September 2018, Apple again released 3 new iPhones, which are the iPhone XS, an upgraded version of the since discontinued iPhone X, iPhone XS Max, a larger variant with the series' biggest display as of 2018 and iPhone XR, a lower end version of the iPhone X; the original iPhone was described as "revolutionary" and a "game-changer" for the mobile phone industry. Subsequent iterations of the iPhone have garnered praise; the iPhone is one of the most used smartphones in the world, its success has been credited with helping Apple become one of the world's most valuable publicly traded companies. Development of what was to become the iPhone began in 2004, when Apple started to gather a team of 1,000 employees to work on the confidential "Project Purple."
Apple CEO Steve Jobs steered the original focus away from a tablet towards a phone. Apple created the device during a secretive collaboration with Cingular Wireless at the time—at an estimated development cost of US$150 million over thirty months. According to Steve Jobs, the "i" word in "iMac" stands for internet, instruct and inspire. Apple rejected the "design by committee" approach that had yielded the Motorola ROKR E1, a unsuccessful collaboration with Motorola. Among other deficiencies, the ROKR E1's firmware limited storage to only 100 iTunes songs to avoid competing with Apple's iPod nano. Cingular gave Apple the liberty to develop the iPhone's hardware and software in-house and paid Apple a fraction of its monthly service revenue, in exchange for four years of exclusive US sales, until 2011. Jobs unveiled the iPhone to the public on January 9, 2007, at the Macworld 2007 convention at the Moscone Center in San Francisco; the two initial models, a 4 GB model priced at US$499 and an 8 GB model at US$599, went on sale in the United States on June 29, 2007, at 6:00 pm local time, while hundreds of customers lined up outside the stores nationwide.
The passionate reaction to the launch of the iPhone resulted in sections of the media dubbing it the'Jesus phone'. Following this successful release in the US, the first generation iPhone was made available in the UK, Germany in November 2007, Ireland and Austria in the spring of 2008. On July 11, 2008, Apple released the iPhone 3G including the original six. Apple released the iPhone 3G in upwards of eighty territories. Apple announced the iPhone 3GS on June 8, 2009, along with plans to release it in June and August, starting with the US, Canada and major European countries on June 19. Many would-be users objected to the iPhone's cost, 40% of users had household incomes over US$100,000; the back of the original first generation iPhone was made of aluminum with a black plastic accent. The iPhone 3G and 3GS feature a full plastic back to increase the strength of the GSM signal; the iPhone 3G was available in
London is the capital and largest city of both England and the United Kingdom. Standing on the River Thames in the south-east of England, at the head of its 50-mile estuary leading to the North Sea, London has been a major settlement for two millennia. Londinium was founded by the Romans; the City of London, London's ancient core − an area of just 1.12 square miles and colloquially known as the Square Mile − retains boundaries that follow its medieval limits. The City of Westminster is an Inner London borough holding city status. Greater London is governed by the Mayor of the London Assembly. London is considered to be one of the world's most important global cities and has been termed the world's most powerful, most desirable, most influential, most visited, most expensive, sustainable, most investment friendly, most popular for work, the most vegetarian friendly city in the world. London exerts a considerable impact upon the arts, education, fashion, healthcare, professional services and development, tourism and transportation.
London ranks 26 out of 300 major cities for economic performance. It is one of the largest financial centres and has either the fifth or sixth largest metropolitan area GDP, it is the most-visited city as measured by international arrivals and has the busiest city airport system as measured by passenger traffic. It is the leading investment destination, hosting more international retailers and ultra high-net-worth individuals than any other city. London's universities form the largest concentration of higher education institutes in Europe. In 2012, London became the first city to have hosted three modern Summer Olympic Games. London has a diverse range of people and cultures, more than 300 languages are spoken in the region, its estimated mid-2016 municipal population was 8,787,892, the most populous of any city in the European Union and accounting for 13.4% of the UK population. London's urban area is the second most populous in the EU, after Paris, with 9,787,426 inhabitants at the 2011 census.
The population within the London commuter belt is the most populous in the EU with 14,040,163 inhabitants in 2016. London was the world's most populous city from c. 1831 to 1925. London contains four World Heritage Sites: the Tower of London. Other landmarks include Buckingham Palace, the London Eye, Piccadilly Circus, St Paul's Cathedral, Tower Bridge, Trafalgar Square and The Shard. London has numerous museums, galleries and sporting events; these include the British Museum, National Gallery, Natural History Museum, Tate Modern, British Library and West End theatres. The London Underground is the oldest underground railway network in the world. "London" is an ancient name, attested in the first century AD in the Latinised form Londinium. Over the years, the name has attracted many mythicising explanations; the earliest attested appears in Geoffrey of Monmouth's Historia Regum Britanniae, written around 1136. This had it that the name originated from a supposed King Lud, who had taken over the city and named it Kaerlud.
Modern scientific analyses of the name must account for the origins of the different forms found in early sources Latin, Old English, Welsh, with reference to the known developments over time of sounds in those different languages. It is agreed; this was adapted into Latin as Londinium and borrowed into Old English, the ancestor-language of English. The toponymy of the Common Brythonic form is much debated. A prominent explanation was Richard Coates's 1998 argument that the name derived from pre-Celtic Old European *lowonida, meaning "river too wide to ford". Coates suggested that this was a name given to the part of the River Thames which flows through London. However, most work has accepted a Celtic origin for the name, recent studies have favoured an explanation along the lines of a Celtic derivative of a proto-Indo-European root *lendh-, combined with the Celtic suffix *-injo- or *-onjo-. Peter Schrijver has suggested, on these grounds, that the name meant'place that floods'; until 1889, the name "London" applied to the City of London, but since it has referred to the County of London and Greater London.
"London" is sometimes written informally as "LDN". In 1993, the remains of a Bronze Age bridge were found on the south foreshore, upstream of Vauxhall Bridge; this bridge either reached a now lost island in it. Two of those timbers were radiocarbon dated to between 1750 BC and 1285 BC. In 2010 the foundations of a large timber structure, dated to between 4800 BC and 4500 BC, were found on the Thames's south foreshore, downstream of Vauxhall Bridge; the function of the mesolithic structure is not known. Both structures are on the south bank. Although there is evidence of scattered Brythonic settlements in the area, the first major settlement was founded by the Romans about four years after the invasion
The Nokia Eseries consists of business-oriented smartphones running Symbian OS, with emphasis on enhanced connectivity and support for corporate e-mail push services, as well as enterprise-styled products and many featuring QWERTY keyboards. All devices have advanced office features through its S60 platform. Phones equipped with Wireless LAN provide a VoIP client. Throughout the series' lifetime its main competitors were BlackBerry products from Research In Motion; the Eseries was marketed until 2011. On October 12, 2005, mobile phone manufacturer Nokia announced what the company refers to as the Eseries, consisting of the three mobile phones, the Nokia E60, Nokia E61 and Nokia E70. On May 18, 2006, Nokia announced the addition of the E50 to the series, which it refers to as a "business device" rather than a "smartphone". On February 12, 2007, Nokia announced the addition of three new devices to the series. On April 11, 2008, Nokia Australia has advised that the E61i will be discontinued in May 2008 and be replaced by a more featured but smaller E71.
Releases included E72, E52 and E5. The last Eseries device was the Nokia E6 from 2011. Nokia phone series#List of Eseries devices Nokia Eseries Detail Information for all Nokia devices "Nokia E62 hits Cingular". Engadget Mobile. 2006-09-12. Retrieved 2006-09-12. "First Look: Nokia E61". OhGizmo!. 2006-06-08. Retrieved 2006-06-14. "E60 photos". Flickr. 2006-06-08. Retrieved 2006-06-12. "Nokia's E60, E61, E70 E-series mobile business phones". Engadget. 2005-10-12. Retrieved 2006-05-28. "Nokia Eseries". Phonescoop.com. 2005-10-14. Retrieved 2006-05-28. "VoIP on the Nokia E-Series". Aql.com. 2006-10-19. Archived from the original on 2006-10-25. Retrieved 2006-10-19. "How to set up VoIP with Asterisk on the E61 and E70". Christian Dannemann. 2006-12-11. Archived from the original on 2007-01-02. Retrieved 2006-12-11