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101-492: Windows Live Call offered three ways of calling: The Phone Call service utilized Windows Live Messenger and Voice over Internet Protocol ( VoIP ) technology to provide users an inexpensive way to make domestic and international phone calls from a computer. Microsoft also released the Windows Live Messenger Phone, which acts as an extension to Windows Live Messenger to make calls to other PC users or acts just like

202-514: A 3G handset or USB wireless broadband adapter, the IP address has no relationship with any physical location known to the telephony service provider, since a mobile user could be anywhere in a region with network coverage, even roaming via another cellular company. At the VoIP level, a phone or gateway may identify itself by its account credentials with a Session Initiation Protocol (SIP) registrar. In such cases,

303-782: A call with the Windows Live Messenger Phone: Additionally, when a contact calls from Windows Live Messenger, the Windows Live Messenger Phone will ring, display information about the caller, and allow the user to answer the call. Currently Uniden and Philips have manufactured the Windows Live Messenger Phone. Verizon was the provider for the Windows Live Call PC-to-Phone service in the United States, but discontinued its Web Calling services for Windows Live Messenger as of September 1, 2008. Microsoft would instead partner with Telefonica to provide

404-402: A computer or mobile device), will connect to the VoIP service remotely. These connections typically take place over public internet links, such as local fixed WAN breakout or mobile carrier service. In the case of a private VoIP system, the primary telephony system itself is located within the private infrastructure of the end-user organization. Usually, the system will be deployed on-premises at

505-421: A copyleft base must come with the source code, and the source code must be available under the same or a similar license. This offers protection against proprietary software consuming code without giving back. Richard Stallman stated that "the central idea of copyleft is to use copyright law, but flip it over to serve the opposite of its usual purpose: instead of a means of privatizing software, [copyright] becomes

606-450: A digital equivalent where the user must click to accept. Open-source software has an additional acceptance mechanism. Without permission from the copyright holder, the law prohibits redistribution. Therefore, courts treat redistribution as acceptance of the license terms. These can include attribution provisions or source code provisions for copyleft licenses. Developers typically achieve compliance without lawsuits. Social pressures, like

707-487: A few and must be used in concert. These functions include: VoIP protocols include: Mass-market VoIP services use existing broadband Internet access , by which subscribers place and receive telephone calls in much the same manner as they would via the PSTN. Full-service VoIP phone companies provide inbound and outbound service with direct inbound dialing . Many offer unlimited domestic calling and sometimes international calls for

808-593: A file-based definition, the CPL and EPL use a module-based definition, and the FSF's own LGPL refers to software libraries. License compatibility determines how code with different licenses can be distributed together. The goal of open-source licensing is to make the work freely available, but this becomes complicated when working with multiple terminologies imposing different requirements. There are many uncommonly used licenses and some projects write their own bespoke agreements. As

909-555: A first-come, first-served basis. Fixed delays cannot be controlled as they are caused by the physical distance the packets travel. They are especially problematic when satellite circuits are involved because of the long distance to a geostationary satellite and back; delays of 400–600 ms are typical. Latency can be minimized by marking voice packets as being delay-sensitive with QoS methods such as DiffServ . Network routers on high volume traffic links may introduce latency that exceeds permissible thresholds for VoIP. Excessive load on

1010-482: A flat monthly subscription fee. Phone calls between subscribers of the same provider are usually free when flat-fee service is not available. A VoIP phone is necessary to connect to a VoIP service provider. This can be implemented in several ways: It is increasingly common for telecommunications providers to use VoIP telephony over dedicated and public IP networks as a backhaul to connect switching centers and to interconnect with other telephony network providers; this

1111-453: A framework for consolidation of all modern communications technologies using a single unified communications system. Voice over IP has been implemented with proprietary protocols and protocols based on open standards in applications such as VoIP phones, mobile applications, and web-based communications . A variety of functions are needed to implement VoIP communication. Some protocols perform multiple functions, while others perform only

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1212-470: A given network path due to competition from other users for the same transmission links. VoIP receivers accommodate this variation by storing incoming packets briefly in a playout buffer , deliberately increasing latency to improve the chance that each packet will be on hand when it is time for the voice engine to play it. The added delay is thus a compromise between excessive latency and excessive dropout , i.e. momentary audio interruptions. Although jitter

1313-459: A license covers free and open-source software. There is significant diversity among individual licenses but little difference between the rival definitions. The three definitions each require that people receiving covered software must be able to use, modify, and redistribute the covered work. Eric S. Raymond was a proponent of the term " open source " over "free software". He viewed open source as more appealing to businesses and more reflective of

1414-448: A link can cause congestion and associated queueing delays and packet loss . This signals a transport protocol like TCP to reduce its transmission rate to alleviate the congestion. But VoIP usually uses UDP not TCP because recovering from congestion through retransmission usually entails too much latency. So QoS mechanisms can avoid the undesirable loss of VoIP packets by immediately transmitting them ahead of any queued bulk traffic on

1515-436: A means of keeping software free." Free software licenses are also open-source software licenses. The separate terms free software and open-source software reflect different values rather than a legal difference. Both movements and their formal definitions require the covered work to be made available with source code and with permission for modification and redistribution. There are occasional edge cases where only one of

1616-530: A media gateway (aka IP Business Gateway) and connects the digital media stream, so as to complete the path for voice and data. Gateways include interfaces for connecting to standard PSTN networks. Ethernet interfaces are also included in the modern systems which are specially designed to link calls that are passed via VoIP. E.164 is a global numbering standard for both the PSTN and public land mobile network (PLMN). Most VoIP implementations support E.164 to allow calls to be routed to and from VoIP subscribers and

1717-565: A more specific and objective standard for the FOSS that Debian would host in their repositories. The OSI adopted the DSFG and used them as the basis for their Open Source Definition. The Free Software Foundation maintains a rival set of criteria, the Free Software Definition. Historically, these three organizations and their sets of criteria have been the notable authorities in determining whether

1818-402: A normal telephone. Windows Live Call was discontinued on June 1, 2010 because Windows Live Messenger Wave 4 release no longer supports VoIP functionalities. However, the "Computer Call" and "Video Call" features are still supported, in the forms of audio and video conversations respectively. The Windows Live Messenger Phone is a two-line phone. The first line plugs into a wall jack similar to

1919-424: A patent retaliation clause. Patent retaliation, or patent suspension, clauses take effect if a licensee initiates patent infringement litigation on covered code. In that situation, the patent grants are revoked. These clauses protect against patent trolling . Copyleft licenses require source code to be distributed with software and require the source code to be made available under a similar license. Like

2020-474: A regular home telephone. The second line is a USB connection to the PC. The base/charger stays near the PC but the handset is wireless , allowing users to take it across their room. The Windows Live Messenger Phone does not require any installation of drivers or control software. The only requirement to take full advantage of the phone is the latest version of Windows Live Messenger. There are two ways users can make

2121-400: A result, this causes more confusion than other legal aspects. When releasing a collection of applications, each license can be considered separately. However, when attempting to combine software, code from another project can only be in-licensed if the project uses compatible terms and conditions. When combining code bases, the original licenses can be maintained for separate components, and

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2222-439: A service provider or telecommunications carrier hosting the telephone system as a software solution within their own infrastructure. Typically this will be one or more data centers with geographic relevance to the end-user(s) of the system. This infrastructure is external to the user of the system and is deployed and maintained by the service provider. Endpoints, such as VoIP telephones or softphone applications (apps running on

2323-602: A similar license. Since the mid-2000s, courts in multiple countries have upheld the terms of both types of license. Software developers have filed cases as copyright infringement and as breaches of contract. Intellectual property (IP) is a legal category that treats creative output as property, comparable to private property . Legal systems grant the owner of an IP the right to restrict access in many ways. Owners can sell, lease, gift, or license their properties. Multiple types of IP law cover software including trademarks , patents , and copyrights . Most countries, including

2424-567: A site within the direct control of the organization. This can provide numerous benefits in terms of QoS control (see below ), cost scalability, and ensuring privacy and security of communications traffic. However, the responsibility for ensuring that the VoIP system remains performant and resilient is predominantly vested in the end-user organization. This is not the case with a Hosted VoIP solution. Private VoIP systems can be physical hardware PBX appliances, converged with other infrastructure, or they can be deployed as software applications. Generally,

2525-441: A subscriber to select a new telephone carrier without requiring a new number to be issued. Typically, it is the responsibility of the former carrier to "map" the old number to the undisclosed number assigned by the new carrier. This is achieved by maintaining a database of numbers. A dialed number is initially received by the original carrier and quickly rerouted to the new carrier. Multiple porting references must be maintained even if

2626-448: A variety of other applications. DSL modems typically provide Ethernet connections to local equipment, but inside they may actually be Asynchronous Transfer Mode (ATM) modems. They use ATM Adaptation Layer 5 (AAL5) to segment each Ethernet packet into a series of 53-byte ATM cells for transmission, reassembling them back into Ethernet frames at the receiving end. Using a separate virtual circuit identifier (VCI) for voice over IP has

2727-616: Is a design that identifies the distinct source of a product. Because they distinguish products, the same designs can be used in different fields where there is no risk of confusing similar sources. To give up control of a trademark would result in the loss of that trademark. Therefore, no open-source license freely offers the use of a trademark. Trademark restrictions can overlap copyrights and affect material otherwise freely available. The US Supreme Court described using trademark law to restrict public domain content as "mutant copyright". In Dastar Corp. v. Twentieth Century Fox Film Corp. ,

2828-521: Is a random variable, it is the sum of several other random variables that are at least somewhat independent: the individual queuing delays of the routers along the Internet path in question. Motivated by the central limit theorem , jitter can be modeled as a Gaussian random variable . This suggests continually estimating the mean delay and its standard deviation and setting the playout delay so that only packets delayed more than several standard deviations above

2929-452: Is a set of conditions under which actions otherwise restricted by IP laws are permitted. Under the bare license interpretation, advocated by the FSF, a case is brought to court by the copyright holder as copyright infringement . Under the contract interpretation, a case can be brought to court by an involved party as a breach of contract . US and French courts have tried cases under both interpretations. Non-profit organizations like FSF and

3030-426: Is also covered by other forms of IP. Major open-source licenses written since the late 1990s contain patent grants. These open-source patent grants cover the patents held by the developers. Software patents cover ideas and, rather than a specific implementation, cover any implementation of a claim . Patent claims give the holder the right to exclude others from making, using, selling, or importing products based on

3131-399: Is characterized by several metrics that may be monitored by network elements and by the user agent hardware or software. Such metrics include network packet loss , packet jitter , packet latency (delay), post-dial delay, and echo. The metrics are determined by VoIP performance testing and monitoring. A VoIP media gateway controller (aka Class 5 Softswitch) works in cooperation with

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3232-708: Is focused on VoIP for medium to large enterprises, while another is targeting the small-to-medium business (SMB) market. Skype , which originally marketed itself as a service among friends, has begun to cater to businesses, providing free-of-charge connections between any users on the Skype network and connecting to and from ordinary PSTN telephones for a charge. In general, the provision of VoIP telephony systems to organizational or individual users can be divided into two primary delivery methods: private or on-premises solutions, or externally hosted solutions delivered by third-party providers. On-premises delivery methods are more akin to

3333-595: Is generally uncommon for those private connectivity methods to be provided by Hosted or Cloud VoIP providers. Communication on the IP network is perceived as less reliable in contrast to the circuit-switched public telephone network because it does not provide a network-based mechanism to ensure that data packets are not lost, and are delivered in sequential order. It is a best-effort network without fundamental quality of service (QoS) guarantees. Voice, and all other data, travels in packets over IP networks with fixed maximum capacity. This system may be more prone to data loss in

3434-574: Is how they define derivative works covered by the reciprocal provisions. The GPL, and the Affero License (AGPL) based on it, use a broad scope to describe affected works. The AGPL extends the reciprocal obligation in the GPL to cover software made available over a network. They are called strong copyleft in contrast to the weaker copyleft licenses often used by corporations. Weak copyleft uses narrower, explicit definitions of derivative works. The MPL uses

3535-533: Is more comprehensive and explicit. The Apache Software Foundation wrote it for their Apache HTTP Server . Version 2, published in 2004, offers legal advantages over simple licenses and provides similar grants. While the BSD and MIT licenses offer an implicit patent grant, the Apache License includes a section on patents with an explicit grant from contributors. Additionally, it is one of the few permissive licenses with

3636-491: Is no longer necessary to carry both a desktop phone and a cell phone. Maintenance becomes simpler as there are fewer devices to oversee. VoIP solutions aimed at businesses have evolved into unified communications services that treat all communications—phone calls, faxes, voice mail, e-mail, web conferences, and more—as discrete units that can all be delivered via any means and to any handset, including cellphones. Two kinds of service providers are operating in this space: one set

3737-471: Is often referred to as IP backhaul . Smartphones may have SIP clients built into the firmware or available as an application download. Because of the bandwidth efficiency and low costs that VoIP technology can provide, businesses are migrating from traditional copper-wire telephone systems to VoIP systems to reduce their monthly phone costs. In 2008, 80% of all new Private branch exchange (PBX) lines installed internationally were VoIP. For example, in

3838-444: Is received by a center the location is automatically determined from its databases and displayed on the operator console. In IP telephony, no such direct link between location and communications end point exists. Even a provider having wired infrastructure, such as a DSL provider, may know only the approximate location of the device, based on the IP address allocated to the network router and

3939-404: Is the continual process where developers can build on the derivative works of each other and combine their projects into collective works. Explicitly making covered code sublicensable provides a legal advantage when tracking the chain of authorship. The BSD and MIT are template licenses that can be adapted to any project. They are widely adapted and used by many FOSS projects. The Apache License

4040-412: Is to reduce the maximum transmission time by reducing the maximum transmission unit . But since every packet must contain protocol headers, this increases relative header overhead on every link traversed. The receiver must resequence IP packets that arrive out of order and recover gracefully when packets arrive too late or not at all. Packet delay variation results from changes in queuing delay along

4141-498: Is triggered when covered code is hosted or distributed. Some developers have adopted the AGPL, and others have switched to proprietary licenses with features of open-source licensing. For example, open-core developer Elastic switched from the Apache license to the "source-available" Server Side Public License . Source-available software comes with source code as a reference. Since 2010,

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4242-614: The Creative Commons CC0, provides a waiver of copyright claims into the public domain along with a permissive software license as a fallback. In jurisdictions that do not accept a public domain waiver, the permissive license takes effect. Public domain waivers share limitations with simple academic licenses. This creates the possibility that an outside party could attempt to control a public domain work via patent or trademark law. Public domain waivers handle warranties differently from any type of license. Even very permissive ones, like

4343-458: The E.164 number to URI mapping (ENUM) service in IMS and SIP. Echo can also be an issue for PSTN integration. Common causes of echo include impedance mismatches in analog circuitry and an acoustic path from the receive to transmit signal at the receiving end. Local number portability (LNP) and mobile number portability (MNP) also impact VoIP business. Number portability is a service that allows

4444-559: The European Court of Justice noted in the 2012 SAS Institute case that "ideas and principles which underlie [computer program] interfaces are not protected by copyright". In a similar 2021 case , the US Supreme Court permitted the recreation of an API in a transformative product under fair use . A long-debated subject within the FOSS community is whether open-source licenses are "bare licenses" or contracts . A bare license

4545-483: The GNU General Public License (GPL). Traditional, proprietary software licenses are written with the goal of increasing profit , but Stallman wrote the GPL to increase the body of available free software. His reciprocal licenses offer the rights to use, modify, and distribute the work on the condition that people must release derivative works under a license offering these same freedoms. Software built on

4646-649: The Internet telephony service provider (ITSP) knows only that a particular user's equipment is active. Service providers often provide emergency response services by agreement with the user who registers a physical location and agrees that, if an emergency number is called from the IP device, emergency services are provided to that address only. Open-source license Open-source licenses are software licenses that allow content to be used, modified, and shared. They facilitate free and open-source software (FOSS) development. Intellectual property (IP) laws restrict

4747-521: The Software Freedom Conservancy offer to hold the rights to developers' projects to enforce compliance. When a copyright expires, the work enters the public domain , and is freely available to anyone. Some creative works are not covered by copyright and enter directly into the public domain. In the early history of computing, this applied to software. Early computer software was often given away with hardware. Developed initially at MIT,

4848-443: The US and German courts rejected these claims. They ruled that the defendants could not have legally distributed the software if the licenses were unenforceable. Courts have found that distributing software indicates acceptance of the license's terms. Physical software releases can obtain the consumer's assent with notices placed on shrinkwrap . Online distribution can use clickwrap ,

4949-497: The free software movement in response to the rise of proprietary software . The term "open source" was used by the Open Source Initiative (OSI), founded by free software developers Bruce Perens and Eric S. Raymond . "Open source" emphasizes the strengths of the open development model rather than software freedoms. While the goals behind the terms are different, open-source licenses and free software licenses describe

5050-861: The linear predictive coding (LPC) and modified discrete cosine transform (MDCT) compression methods. Popular codecs include the MDCT-based AAC-LD (used in FaceTime ), the LPC/MDCT-based Opus (used in WhatsApp ), the LPC-based SILK (used in Skype ), μ-law and A-law versions of G.711 , G.722 , and an open source voice codec known as iLBC , a codec that uses only 8 kbit/s each way called G.729 . Early providers of voice-over-IP services used business models and offered technical solutions that mirrored

5151-522: The 1980s, he started the GNU Project to create a free operating system, wrote essays on freedom, founded the Free Software Foundation (FSF), and wrote several free software licenses. The FSF used existing intellectual property laws for the opposite of their intended goal of restriction. Instead of imposing restrictions, free software explicitly provided freedoms to the recipient. In the 90s,

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5252-406: The 2004 Apache License offer explicit patent grants and limited protection from patent litigation. These patent retaliation clauses protect developers by terminating grants for any party who initiates a patent lawsuit regarding covered software. Trademarks are the only form of IP not shared by free and open-source software. Trademarks on FOSS function the same as any other trademark. A trademark

5353-561: The FSF or the OSI accept a license, but the popular free software licenses are open source, including the GPL . Practical benefits to copyleft licenses have attracted commercial developers. Corporations have used and written reciprocal licenses with a narrower scope than the GPL. For example, Netscape drafted their own copyleft terms after rejecting permissive licenses for the Mozilla project. The GPL remains

5454-427: The GPL and are said to be GPL-compatible. GPL software can only be used under the GPL or AGPL. Permissive licenses are broadly compatible because they can cover separate parts of a project. Multiple licenses including the GPL and Apache License have been revised to enhance compatibility. Translation issues, ambiguity in licensing terms, and incompatibility of some licenses with the law in certain jurisdictions compound

5555-476: The MIT license, disclaim warranty and liability. Anyone using the free software must accept this disclaimer as a condition. Because public domain content is available to everyone, the copyright waiver cannot impose a disclaimer. Open-source licenses allow other businesses to commercialize covered software. Work released under a permissive license can be incorporated into proprietary software. Permissive licenses permit

5656-436: The OSI. Open-source licenses are categorized as copyleft or permissive . Copyleft licenses require derivative works to include source code under a similar license. Permissive licenses do not, and therefore the code can be used within proprietary software. Copyleft can be further divided into strong and weak depending on whether they define derivative works broadly or narrowly. Licenses focus on copyright law, but code

5757-543: The PSTN/PLMN. VoIP implementations can also allow other identification techniques to be used. For example, Skype allows subscribers to choose Skype names (usernames) whereas SIP implementations can use Uniform Resource Identifier (URIs) similar to email addresses . Often VoIP implementations employ methods of translating non-E.164 identifiers to E.164 numbers and vice versa, such as the Skype-In service provided by Skype and

5858-513: The United States (US), have created copyright laws in line with the Berne Convention . These laws assign a copyright whenever a work is released in any fixed format. Under US copyright law, the initial release is considered an original work . The creator, or their employer, holds the copyright to this original work and therefore has the exclusive right to make copies, release modified versions, distribute copies, perform publicly, or display

5959-911: The United States, the Social Security Administration is converting its field offices of 63,000 workers from traditional phone installations to a VoIP infrastructure carried over its existing data network. VoIP allows both voice and data communications to be run over a single network, which can significantly reduce infrastructure costs. The prices of extensions on VoIP are lower than for PBX and key systems. VoIP switches may run on commodity hardware, such as personal computers . Rather than closed architectures, these devices rely on standard interfaces. VoIP devices have simple, intuitive user interfaces, so users can often make simple system configuration changes. Dual-mode phones enable users to continue their conversations as they move between an outside cellular service and an internal Wi-Fi network, so that it

6060-505: The addition of new terms, including proprietary ones. Proprietary software has heavily integrated open-source code released under the Apache, BSD, and MIT licenses. Open core is a business model where developers release a core piece of software as open source and monetize a product containing it as proprietary software. The strong copyleft GPL is written to prevent distribution within proprietary software. Weak copyleft licenses impose specific requirements on derivative works that may allow

6161-647: The analog voice signals, and encoding. Instead of being transmitted over a circuit-switched network , the digital information is packetized and transmission occurs as IP packets over a packet-switched network . They transport media streams using special media delivery protocols that encode audio and video with audio codecs and video codecs . Various codecs exist that optimize the media stream based on application requirements and network bandwidth; some implementations rely on narrowband and compressed speech , while others support high-fidelity stereo codecs. The most widely used speech coding standards in VoIP are based on

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6262-426: The architecture of the legacy telephone network. Second-generation providers, such as Skype , built closed networks for private user bases, offering the benefit of free calls and convenience while potentially charging for access to other communication networks, such as the PSTN. This limited the freedom of users to mix-and-match third-party hardware and software. Third-generation providers, such as Google Talk , adopted

6363-446: The classic PBX deployment model for connecting an office to local PSTN networks. While many use cases still remain for private or on-premises VoIP systems, the wider market has been gradually shifting toward Cloud or Hosted VoIP solutions. Hosted systems are also generally better suited to smaller or personal use VoIP deployments, where a private system may not be viable for these scenarios. Hosted or Cloud VoIP solutions involve

6464-399: The concept of federated VoIP . These solutions typically allow dynamic interconnection between users in any two domains of the Internet, when a user wishes to place a call. In addition to VoIP phones , VoIP is also available on many personal computers and other Internet access devices. Calls and SMS text messages may be sent via Wi-Fi or the carrier's mobile data network. VoIP provides

6565-741: The court "caution[ed] against misuse or over-extension of trademark" law without providing a firm decision on those mutant copyrights. Trademark overlap can leave open-source and free content projects vulnerable to a "hostile takeover" if outside parties file for trademarks on derivative works. Notably, Andrey Duskin applied for trademarks on the SCP Foundation , a collaborative writing project, when creating derivative works based on SCP stories. Permissive licenses , also known as academic licenses, allow recipients to use, modify, and distribute software with no obligation to provide source code. Institutions created these licenses to distribute their creations to

6666-439: The covered code to be distributed within proprietary software in certain circumstances. Cloud computing relies on free and open-source software and avoids the distribution that triggers most licenses. Cloud software is hosted rather than distributed. A vendor hosts the software online, and their end users do not have to download, access, or even know about the code in use. The copyleft GNU Affero General Public License (AGPL)

6767-399: The covered software. The BSD licenses brought the concept of academic freedom of ideas to computing. Early academic software authors had shared code based on implied promises. Berkeley made these concepts explicit with clear disclaimers for liability and warranty along with conditions, or clauses , for redistribution. The original had four clauses, but subsequent versions have further reduced

6868-436: The enterprise markets because of LCR options, VoIP needs to provide a certain level of reliability when handling calls. A telephone connected to a land line has a direct relationship between a telephone number and a physical location, which is maintained by the telephone company and available to emergency responders via the national emergency response service centers in form of emergency subscriber lists. When an emergency call

6969-576: The idea. Because patents grant the right to exclude rather than the right to create, it is possible to have a patent on an idea but still be unable to legally implement it if the invention relies on another patented idea. Thus, open-source patent grants can offer permission only from covered patents. They cannot guarantee that a third party has not patented any concepts embodied in the code. The older permissive licenses do not discuss patents directly and offer only implicit patent grants in their offers to use or sell covered material. Newer copyleft licenses and

7070-404: The jitter buffer. VoIP metrics reports are exchanged between IP endpoints on an occasional basis during a call, and an end of call message sent via SIP RTCP summary report or one of the other signaling protocol extensions. VoIP metrics reports are intended to support real-time feedback related to QoS problems, the exchange of information between the endpoints for improved call quality calculation and

7171-508: The known service address. Some ISPs do not track the automatic assignment of IP addresses to customer equipment. IP communication provides for device mobility. For example, a residential broadband connection may be used as a link to a virtual private network of a corporate entity, in which case the IP address being used for customer communications may belong to the enterprise, not the residential ISP. Such off-premises extensions may appear as part of an upstream IP PBX. On mobile devices, e.g.,

7272-425: The larger work released under a compatible license. This compatibility is often one-way. Public domain content can be used anywhere as there is no copyright claim, but code acquired under any almost any set of terms cannot be waved to the public domain. Permissive licenses can be used within copyleft works, but copyleft material cannot be released under a permissive license. Some weak copyleft licenses can be used under

7373-525: The latter two options will be in the form of a separate virtualized appliance. However, in some scenarios, these systems are deployed on bare metal infrastructure or IoT devices. With some solutions, such as 3CX, companies can attempt to blend the benefits of hosted and private on-premises systems by implementing their own private solution but within an external environment. Examples can include data center collocation services, public cloud, or private cloud locations. For on-premises systems, local endpoints within

7474-480: The license, increasing the difficulties of compliance. Free and open-source software licenses have been successfully enforced in civil court since the mid-2000s. In a pair of early lawsuits— Jacobsen v. Katzer in the United States and Welte v. Sitecom in Germany—;defendants argued that open-source licenses were invalid. Sitecom and Katzer separately argued that the licenses were unenforceable. Both

7575-498: The mean will arrive too late to be useful. In practice, the variance in latency of many Internet paths is dominated by a small number (often one) of relatively slow and congested bottleneck links . Most Internet backbone links are now so fast (e.g. 10 Gbit/s) that their delays are dominated by the transmission medium (e.g. optical fiber) and the routers driving them do not have enough buffering for queuing delays to be significant. A number of protocols have been defined to support

7676-465: The modern usage begins with Richard Stallman's efforts to create a free operating system. In 1984, programmer Don Hopkins mailed a manual to Stallman with a "Copyleft Ⓛ" sticker. Stallman, who was working on the GNU operating system, adopted the term. An early version of copyleft licensing was used for the 1985 release of GNU Emacs . The term became associated with the FSF's later reciprocal licenses, notably

7777-521: The modification and sharing of creative works. Free and open-source licenses use these existing legal structures for an inverse purpose. They grant the recipient the rights to use the software, examine the source code , modify it, and distribute the modifications. These criteria are outlined in the Open Source Definition . After 1980, the United States began to treat software as a literary work covered by copyright law. Richard Stallman founded

7878-674: The most popular license of this type, but there are other significant examples. The FSF has crafted the Lesser General Public License (LGPL) for libraries . Mozilla uses the Mozilla Public License (MPL) for their releases, including Firefox . IBM drafted the Common Public License (CPL) and later adopted the Eclipse Public License (EPL). A difference between the GPL and other reciprocal licenses

7979-475: The network root prefix to determine how to route a call. Instead, they must now determine the actual network of every number before routing the call. Therefore, VoIP solutions also need to handle MNP when routing a voice call. In countries without a central database, like the UK, it may be necessary to query the mobile network about which home network a mobile phone number belongs to. As the popularity of VoIP increases in

8080-405: The number is routed to a mobile phone number on a traditional mobile carrier. LCR is based on checking the destination of each telephone call as it is made, and then sending the call via the network that will cost the customer the least. This rating is subject to some debate given the complexity of call routing created by number portability. With MNP in place, LCR providers can no longer rely on using

8181-461: The permissive licenses, most copyleft licenses require attribution. Most, including the GPL, disclaim implied warranties. Copyleft uses the restrictions of IP law—contrary to their usual purpose—to mandate that the code remain open. The term and it's related slogan, "All rights reversed", had been previously used in a playful manner by the Principia Discordia and Tiny BASIC ;

8282-557: The pioneering video game Spacewar! was used to market and test the PDP-1 computer. According to attorney Lawrence Rosen , copyright laws were not written with the expectation that creators would place their work into the public domain. Thus intellectual property laws lack clear paths to waive a copyright. Highly permissive licenses described as "public domain" may legally function as unilateral contracts that offer something but impose no terms. A public-domain-equivalent license , like

8383-919: The potential for community backlash, are often sufficient. Cease and desist letters are a common method to bring companies back into compliance, especially in Germany. A standard process has developed in the German legal system. FOSS developers present companies with a cease and desist letter. These letters outline how to come back into compliance from a violation. German judges can issue a court-mandated cease and desist order to unresponsive companies. Civil cases proceed if these first steps fail. The German procedural laws are clear and favorable to claimants. Uncertainties remain in how different courts will handle certain aspects of licensing. For software in general, there are debates about what can be patented and what can be copyrighted. Regarding an application programming interface (API),

8484-748: The potential to reduce latency on shared connections. ATM's potential for latency reduction is greatest on slow links because worst-case latency decreases with increasing link speed. A full-size (1500 byte) Ethernet frame takes 94 ms to transmit at 128 kbit/s but only 8 ms at 1.5 Mbit/s. If this is the bottleneck link, this latency is probably small enough to ensure good VoIP performance without MTU reductions or multiple ATM VCs. The latest generations of DSL, VDSL and VDSL2 , carry Ethernet without intermediate ATM/AAL5 layers, and they generally support IEEE 802.1p priority tagging so that VoIP can be queued ahead of less time-critical traffic. ATM has substantial header overhead: 5/53 = 9.4%, roughly twice

8585-463: The presence of congestion than traditional circuit switched systems; a circuit switched system of insufficient capacity will refuse new connections while carrying the remainder without impairment, while the quality of real-time data such as telephone conversations on packet-switched networks degrades dramatically. Therefore, VoIP implementations may face problems with latency , packet loss, and jitter . By default, network routers handle traffic on

8686-417: The problem of license compatibility. Downloading an open-source module is straightforward, but complying with the licensing terms can be more difficult. Because of the amount of software dependencies, engineers working on complex projects often rely on license management software to achieve compliance with the licensing terms of open-source components. Many open-source software files do not unambiguously state

8787-529: The proprietary model where small pools of secretive workers carried out this work with the development of Linux where the pool of testers included potentially the entire world. He summarized this strength as "Given enough eyeballs, all bugs are shallow." The OSI succeeded in bringing open-source development to corporate developers including Sun Microsystems, IBM , Netscape, Mozilla , Apache , Apple Inc., Microsoft, and Nokia. These companies released code under existing licenses and drafted their own to be approved by

8888-401: The provisioning of voice and other communications services ( fax , SMS , voice messaging ) over the Internet, rather than via the public switched telephone network (PSTN), also known as plain old telephone service (POTS). The steps and principles involved in originating VoIP telephone calls are similar to traditional digital telephony and involve signaling, channel setup, digitization of

8989-545: The public. Permissive licenses are usually short, often less than a page of text. They impose few conditions . Most include disclaimers of warranty and obligations to credit authors. A few include explicit provisions for patents, trademarks, and other forms of intellectual property. The University of California, Berkeley created the first open-source license when they began distributing their Berkeley Software Distribution (BSD) operating system. The BSD license and its later variations permit modification and distribution of

9090-689: The reporting of quality of service (QoS) and quality of experience (QoE) for VoIP calls. These include RTP Control Protocol (RTCP) extended reports, SIP RTCP summary reports, H.460.9 Annex B (for H.323 ), H.248 .30 and MGCP extensions. The RTCP extended report VoIP metrics block specified by RFC   3611 is generated by an VoIP phone or gateway during a live call and contains information on packet loss rate, packet discard rate (because of jitter), packet loss/discard burst metrics (burst length/density, gap length/density), network delay, end system delay, signal/noise/echo level, mean opinion scores (MOS) and R factors and configuration information related to

9191-412: The restrictions. As a result, it's common to specify if the covered software uses a 2-clause or 3-clause version. The Massachusetts Institute of Technology (MIT) created an academic license based on the BSD original. The MIT license clarified the conditions by making them more explicit. For example, the MIT license describes the right to sublicense . One of the strengths of open-source development

9292-497: The same link, even when the link is congested by bulk traffic. VoIP endpoints usually have to wait for the completion of transmission of previous packets before new data may be sent. Although it is possible to preempt (abort) a less important packet in mid-transmission, this is not commonly done, especially on high-speed links where transmission times are short even for maximum-sized packets. An alternative to preemption on slower links, such as dialup and digital subscriber line (DSL),

9393-530: The same location typically connect directly over the LAN . For remote and external endpoints, available connectivity options mirror those of Hosted or Cloud VoIP solutions. However, VoIP traffic to and from the on-premises systems can often also be sent over secure private links. Examples include personal VPN, site-to-site VPN , private networks such as MPLS and SD-WAN, or via private SBCs (Session Border Controllers). While exceptions and private peering options do exist, it

9494-421: The same type of licenses. The two main categories of open-source licenses are permissive and copyleft . Both grant permission to change and distribute software. Typically, they require attribution and disclaim liability . Permissive licenses come from academia. Copyleft licenses come from the free software movement. Copyleft licenses require derivative works to be distributed with the source code and under

9595-529: The service. Other partners who hosted the Windows Live Call service included: Voice over IP Voice over Internet Protocol ( VoIP ), also called IP telephony , is a method and group of technologies for voice calls for the delivery of voice communication sessions over Internet Protocol (IP) networks, such as the Internet . The broader terms Internet telephony , broadband telephony , and broadband phone service specifically refer to

9696-522: The subscriber returns to the original carrier. The Federal Communications Commission (FCC) mandates carrier compliance with these consumer-protection stipulations. In November 2007, the FCC in the United States released an order extending number portability obligations to interconnected VoIP providers and carriers that support VoIP providers. A voice call originating in the VoIP environment also faces least-cost routing (LCR) challenges to reach its destination if

9797-528: The tangible advantages of FOSS development. One of Raymond's goals was to expand the existing hacker community to include large commercial developers. In The Cathedral and the Bazaar , Raymond compared open-source development to the bazaar , an open-air public market. He argued that aside from ethics, the open model provided advantages that proprietary software could not replicate. Raymond focused heavily on feedback , testing , and bug reports . He contrasted

9898-501: The term "open source" was coined as an alternative label for free software, and specific criteria were laid out to determine which licenses covered free and open-source software. Two active members of the free software community, Bruce Perens and Eric S. Raymond , founded the Open Source Initiative (OSI). At Debian , Perens had proposed the Debian Free Software Guidelines (DFSG). The DFSG were drafted to provide

9999-443: The total header overhead of a 1500 byte Ethernet frame. This "ATM tax" is incurred by every DSL user whether or not they take advantage of multiple virtual circuits – and few can. Several protocols are used in the data link layer and physical layer for quality-of-service mechanisms that help VoIP applications work well even in the presence of network congestion . Some examples include: The quality of voice transmission

10100-477: The work publicly. Modified versions of the original work are derivative works . When a creator modifies an existing work, they hold the copyright to their modifications. Unless the original work was in the public domain, a derivative work can only be distributed with the permission of every copyright holder. In 1980, the US government amended the law to treat software as a literary work. Software released after this point

10201-495: Was restricted by IP laws. At that time, American activist and programmer Richard Stallman was working as a graduate student at the MIT Computer Science and Artificial Intelligence Laboratory . Stallman witnessed fragmentation among software developers. He blamed the spread of proprietary software and closed models of development. To push back against these trends, Stallman founded the free software movement . Throughout

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