Voice over IP
Early providers of voice-over-IP services used business models and offered technical solutions that mirrored the architecture of the legacy telephone network.
VoIP technology has been adapted for use in mobile networks, leading to the development of advanced systems designed to support voice communication over modern data infrastructures.
[5][6] VoLTE, introduced as part of 4G LTE networks, enables voice communication over an IP-based infrastructure initially developed for data transmission.
This integration ensures additional features such as emergency call support and quality-of-service guarantees, making them a central part of modern mobile telecommunication systems.
[18] For example, in 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.
[19][20] VoIP allows both voice and data communications to be run over a single network, which can significantly reduce infrastructure costs.
[21] 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 is focused on VoIP for medium to large enterprises, while another is targeting the small-to-medium business (SMB) market.
On-premises delivery methods are more akin to the classic PBX deployment model for connecting an office to local PSTN networks.
These connections typically take place over public internet links, such as local fixed WAN breakout or mobile carrier service.
This can provide numerous benefits in terms of QoS control (see below), cost scalability, and ensuring privacy and security of communications traffic.
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.
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 a variety of other applications.
Using a separate virtual circuit identifier (VCI) for voice over IP has the potential to reduce latency on shared connections.
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.
Some examples include: The quality of voice transmission is characterized by several metrics that may be monitored by network elements and by the user agent hardware or software.
Such emergency services are provided by VoIP vendors in the United States by a system called Enhanced 911 (E911), based on the Wireless Communications and Public Safety Act.
This means that hackers with knowledge of VoIP vulnerabilities can perform denial-of-service attacks, harvest customer data, record conversations, and compromise voicemail messages.
Compromised VoIP user account or session credentials may enable an attacker to incur substantial charges from third-party services, such as long-distance or international calling.
A result of the lack of widespread support for encryption is that it is relatively easy to eavesdrop on VoIP calls when access to the data network is possible.
[68] In September 2017, Saudi Arabia lifted the ban on VoIPs, in an attempt to reduce operational costs and spur digital entrepreneurship.
[74] On March 24, 2020, the United Arab Emirates loosened restriction on VoIP services earlier prohibited in the country, to ease communication during the COVID-19 pandemic.
However, popular instant messaging applications like WhatsApp, Skype, and FaceTime remained blocked from being used for voice and video calls, constricting residents to use paid services from the country's state-owned telecom providers.
[79] VoIP operators in the US are required to support local number portability; make service accessible to people with disabilities; pay regulatory fees, universal service contributions, and other mandated payments; and enable law enforcement authorities to conduct surveillance pursuant to the Communications Assistance for Law Enforcement Act (CALEA).
Operators of Interconnected VoIP (fully connected to the PSTN) are mandated to provide Enhanced 911 service without special request, provide for customer location updates, clearly disclose any limitations on their E-911 functionality to their consumers, obtain affirmative acknowledgements of these disclosures from all consumers,[80] and may not allow their customers to opt-out of 911 service.
The NSA is not authorized to tap Americans' conversations without a warrant—but the Internet, and specifically VoIP does not draw as clear a line to the location of a caller or a call's recipient as the traditional phone system does.
As VoIP's low cost and flexibility convinces more and more organizations to adopt the technology, surveillance for law enforcement agencies becomes more difficult.
LPC was capable of speech compression down to 2.4 kbps, leading to the first successful real-time conversation over ARPANET in 1974, between Culler-Harrison Incorporated in Goleta, California, and MIT Lincoln Laboratory in Lexington, Massachusetts.
Soon after it became an established area of interest in commercial labs of the major IT concerns, notably at AT&T, where Marian Croak and her team filed many patents related to the technology.
