Voice over IP is a methodology and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. Other terms commonly associated with VoIP are IP telephony, Internet telephony, voice over broadband (VoBB), broadband telephony, IP communications, and broadband phone service.
The term Internet telephony specifically refers to the provisioning of communications services over the public Internet, rather than via the public switched telephone network (PSTN). The steps and principles involved in originating VoIP telephone calls are similar to traditional digital telephony, and involve signaling, channel setup, digitization of the analog voice signals, and encoding. Instead of being transmitted over a circuit-switched network, however, the digital information is packetized and transmission occurs as Internet Protocol (IP) packets over a packet-switched network. Such transmission entails careful considerations about resource management different from time-division multiplexing (TDM) networks.
Early providers of voice over IP services offered business models and technical solutions that mirrored the architecture of the legacy telephone network. Second generation providers, such as Skype, have 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 has limited the freedom of users to mix-and-match third-party hardware and software. Third generation providers, such as Google Talk have adopted the concept of federated VoIP ? which is a departure from the architecture of the legacy networks. These solutions typically allow dynamic interconnection between users on any two domains on the Internet when a user wishes to place a call.
| VoIP is available on computers, and on Internet access messages may be sent over 3G or | many smartphones, personal devices. Calls and SMS text Wi-Fi. |
| The H.323 protocol was protocols that found widespread traffic, as well as local area since the development of such as MGCP and SIP, H.323 limited to carrying existing particular, the Session Initiation VoIP market penetration. | one of the 1st VoIP implementation for long-distance network services. However, newer, less complex protocols deployments are increasingly long-haul network traffic. In Protocol has gained widespread - |
| These protocols can be software, such as Jitsi, or Google Talk. | used by special-purpose integrated into a web page, like - |
| It is becoming telecommunications providers to use VoIP public IP networks to connect interconnect with other telephony often referred to as ?IP | increasingly common for telephony over dedicated and switching centres and to network providers; this is backhaul?. |
| Because of the costs that VoIP technology are migrating from systems to VoIP systems to costs. In 2008, 80% of all new internationally were VoIP. | bandwidth efficiency and low can provide, businesses traditional copper-wire telephone reduce their monthly phone PBX lines installed - |
| VoIP solutions aimed at unified communications communications?phone calls, faxes, voice conferences and more?as discrete delivered via any means and to any Two kinds of competitors space: one set is focused on enterprises, while another is business market. | businesses have evolved into services that treat all mail, e-mail, Web units that can all be handset, including cellphones. are competing in this VoIP for medium to large targeting the small-to-medium - |
| VoIP allows both voice be run over a single significantly reduce infrastructure | and data communications to network, which can costs. |
| The prices of for PBX and key systems. commodity hardware, such as closed architectures, these interfaces. | extensions on VoIP are lower than VoIP switches may run on personal computers. Rather than devices rely on standard - |
| VoIP devices have interfaces, so users can often make changes. Dual-mode phones conversations as they move between an internal Wi-Fi network, so that to carry both a desktop Maintenance becomes simpler as oversee. | simple, intuitive user simple system configuration enable users to continue their outside cellular service and an it is no longer necessary phone and a cellphone. there are fewer devices to - |
| In the United States the Administration is converting its field traditional phone installations to carried over its existing data | Social Security offices of 63,000 workers from a VoIP infrastructure network. |
| Communication on the IP reliable in contrast to the network, as it does not provide a that data packets aren?t sequential order. It is a fundamental Quality of Service implementations may face problems | network is perceived less circuit-switched public telephone network-based mechanism to ensure lost, and are delivered in best-effort network without guarantees. Therefore, VoIP mitigating latency and jitter. |
| By default, network first-come, first-served basis. traffic links may introduce permissible thresholds for VoIP. controlled, as they are caused by the travel; however, latency can be packets as being DiffServ. | routers handle traffic on a Network routers on high volume latency that exceeds Fixed delays cannot be physical distance the packets minimized by marking voice delay-sensitive with methods such as - |
| VoIP endpoints usually of transmission of data may be sent. Although it less important packet in done, especially on transmission times are short even for alternative to preemption on slower digital subscriber line (DSL), transmission time by reducing the every packet must contain increases relative header traversed, not just the bottleneck | have to wait for completion previous packets, before new is possible to preempt a mid-transmission, this isn?t commonly high-speed links where maximum-sized packets. An links, such as dialup and is to reduce the maximum maximum transmission unit. But protocol headers, so this overhead on every link (usually Internet access) link. |
| DSL modems provide equipment, but inside they are Mode (ATM) modems. They use (AAL5) to segment each 53-byte ATM cells for into Ethernet frames at the identifier (VCI) is part of the cell, so the transmitter can circuits (VCs) in any arbitrary are always sent | Ethernet connections to local actually Asynchronous Transfer ATM Adaptation Layer 5 Ethernet packet into a series of transmission, reassembling them back receiving end. A virtual circuit 5-byte header on every ATM multiplex the active virtual order. Cells from the same VC sequentially. |
However, a majority of DSL providers use only one VC for each customer, even those with bundled VoIP service. Every Ethernet frame must be completely transmitted before another can begin. If a 2nd VC were established, given high priority and reserved for VoIP, then a low priority data packet could be suspended in mid-transmission and a VoIP packet sent right away on the high priority VC. Then the link would pick up the low priority VC where it left off. Because ATM links are multiplexed on a cell-by-cell basis, a high priority packet would have to wait at most 53 byte times to begin transmission. There would be no need to reduce the interface MTU and accept the resulting increase in higher layer protocol overhead, and no need to abort a low priority packet and resend it later.
| Voice, and all other IP networks with fixed may be more prone to traditional circuit switched system of insufficient connections while carrying the while the quality of conversations on packet-switched dramatically. | data, travels in packets over maximum capacity. This system congestion and DoS attacks than systems; a circuit switched capacity will refuse new remainder without impairment, real-time data such as telephone networks degrades - |
| When the load on a link switches experience queue data packets are lost. This like TCP to reduce its congestion. But VoIP usually uses recovering from congestion usually entails too much avoid the undesirable loss of transmitting them ahead of any queued link, even when that bulk | grows so quickly that its overflows, congestion results and signals a transport protocol transmission rate to alleviate the UDP not TCP because through retransmission latency. So QoS mechanisms can VoIP packets by immediately bulk traffic on the same traffic queue is overflowing. |
| The receiver must out of order and recover late or not at all. Jitter random changes in queue path due to competition from transmission links. VoIP receivers incoming packets briefly in a deliberately increasing latency to packet will be on hand when it is play it. The added delay is excessive latency and excessive interruptions. | resequence IP packets that arrive gracefully when packets arrive too results from the rapid and lengths along a given Internet other users for the same counter jitter by storing ?de-jitter? or ?playout? buffer, improve the chance that each time for the voice engine to thus a compromise between dropout, i.e. momentary audio - |
| It has been suggested to nature of media in VoIP of packets from the source phone simultaneously across temporary failures have less quality. In capillary routing it the packet level Fountain codes for transmitting extra communication more reliable. | rely on the packetized communications and transmit the stream phone to the destination different routes. In such a way, impact on the communication has been suggested to use at codes or particularly raptor redundant packets making the - |
| Rural areas in their ability to choose a VoIP generally down to the poor access rural country areas. With the potential for corporate users areas to switch their which is comparatively as broadband connection. This quality & user experience areas. This method was already surpassing all expectations. | particular are greatly hindered in system over PBX. This is to superfast broadband in release of 4G data, there is a based outside of populated internet connection to 4G data, fast as a regular superfast greatly enhances the overall of a VoIP system in these trialled in rural Germany, - |
| The Media VoIP Gateway stream, so as to complete well as data media. It connecting the standard PSTN Protocol networks. The Ethernet modern systems, which are that are passed via the VoIP. | connects the digital media creating the path for voice as includes the interface for networks with the ATM and Inter interfaces are also included in the specially designed to link calls - |
Related Sites for Voice over IP
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