Voice over Internet Protocol Voice over Internet Protocol (VoIP, Voice over IP) is a general term for a family of methodologies, communication protocols, and transmission technologies for delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. Other terms frequently encountered and synonymous with VoIP are IP telephony, Internet telephony, voice over broadband (VoBB), broadband telephony, and broadband phone. Internet telephony refers to communications services -” voice, facsimile, and/or voice-messaging applications -” that are transported via the Internet, rather than the public switched telephone network (PSTN). The basic steps involved in originating an Internet telephone call are conversion of the analog voice signal to digital format and compression/translation of the signal into Internet protocol (IP) packets for transmission over the Internet; the process is reversed at the receiving end. VoIP systems employ session control protocols to control the set-up and tear-down of calls as well as audio codecs which encode speech allowing transmission over an IP network as digital audio via an audio stream. Codec use is varied between different implementations of VoIP (and often a range of codecs are used); some implementations rely on narrowband and compressed speech, while others support high fidelity stereo codecs.
Example of residential network including VoIP A major development that started in 2004[2] was the introduction of mass-market VoIP services that utilize existing broadband Internet access, by which subscribers place and receive telephone calls in much the same manner as they would via the public switched telephone network (PSTN). Full-service VoIP phone companies provide inbound and outbound service with Direct Inbound Dialing. Many offer unlimited domestic calling for a flat monthly subscription fee. This sometimes includes international calls to certain countries. Phone calls between subscribers of the same provider are usually free when flat-fee service is not available.[3] A VoIP phone is necessary to connect to a VoIP service provider. This can be implemented in several ways: · Dedicated VoIP phones connect directly to the IP network using technologies such as wired Ethernet or wireless Wi-Fi. They are typically designed in the style of traditional digital business telephones. · An analog telephone adapter is a device that connects to the network and implements the electronics and firmware to operate a conventional analog telephone attached through a modular phone jack. Some residential Internet gateways and cablemodems have this function built in. · A softphone is application software installed on a networked computer that is equipped with a microphone and speaker, or headset. The application typically presents a dial pad and display field to the user to operate the application by mouse clicks or keyboard input. PSTN and mobile network providers It is becoming increasingly common for telecommunications providers to use VoIP telephony over dedicated and public IP networks to connect switching stations and to interconnect with other telephony network providers; this is often referred to as “IP backhaul”. Smartphones and Wi-Fi enabled mobile phones may have SIP clients built into the firmware or available as an application download. Such clients operate independently of the mobile telephone phone network and use either the cellular data connection or WiFi to make and receive phone calls. Corporate use Because of the bandwidth efficiency and low costs that VoIP technology can provide, businesses are gradually beginning to migrate from traditional copper-wire telephone systems to VoIP systems to reduce their monthly phone costs. 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 competitors are competing 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. VoIP runs both voice and data communications over a single network, which can significantly reduce infrastructure costs. The prices of extensions on VoIP are lower than for PBXs and key systems. VoIP switches run on commodity hardware, such as PCs or Linux systems. 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 cellphones enable users to continue their conversations as they move between an outside cellular service and an internal Wi-Fi network, so that it is no longer necessary to carry both a desktop phone and a cellphone. Maintenance becomes simpler as there are fewer devices to oversee. 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 the United States the Social Security Administration (SSA) is converting its field offices of 63,000 workers from traditional phone installations to a VoIP infrastructure carried over its existing data network. Benefits Operational cost VoIP can be a benefit for reducing communication and infrastructure costs. Examples include: · Routing phone calls over existing data networks to avoid the need for separate voice and data networks. · Conference calling, IVR, call forwarding, automatic redial, and caller ID features that traditional telecommunication companies (telcos) normally charge extra for are available free of charge from open source VoIP implementations Flexibility VoIP can facilitate tasks and provide services that may be more difficult to implement using the PSTN. Examples include: · The ability to transmit more than one telephone call over a single broadband connection. · Secure calls using standardized protocols (such as Secure Real-time Transport Protocol). Most of the difficulties of creating a secure telephone connection over traditional phone lines, such as digitizing and digital transmission, are already in place with VoIP. It is only necessary to encrypt and authenticate the existing data stream. · Location independence. Only a sufficiently fast and stable Internet connection is needed to get a connection from anywhere to a VoIP provider. Lack of redundancy With the current separation of the Internet and the PSTN, a certain amount of redundancy is provided. An Internet outage does not necessarily mean that a voice communication outage will occur simultaneously, allowing individuals to call for emergency services and many businesses to continue to operate normally. In situations where telephone services become completely reliant on the Internet infrastructure, a single-point failure can isolate communities from all communication, including Enhanced 911 and equivalent services in other locales. Number portability Local number portability (LNP) and Mobile number portability (MNP) also impact VoIP business. In November 2007, the Federal Communications Commission in the United States released an order extending number portability obligations to interconnected VoIP providers and carriers that support VoIP providers.[18] Number portability is a service that allows 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 the subscriber returns to the original carrier. The FCC mandates carrier compliance with these consumer-protection stipulations. A voice call originating in the VoIP environment also faces challenges to reach its destination if the number is routed to a mobile phone number on a traditional mobile carrier. VoIP has been identified in the past as a Least Cost Routing (LCR) system, which 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.[19] This rating is subject to some debate given the complexity of call routing created by number portability. With GSM number portability now in place, LCR providers can no longer rely on using 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 might be necessary to query the GSM network about which home network a mobile phone number belongs to. As the popularity of VoIP increases in the enterprise markets because of least cost routing options, it needs to provide a certain level of reliability when handling calls. MNP checks are important to assure that this quality of service is met. By handling MNP lookups before routing a call and by assuring that the voice call will actually work, VoIP service providers are able to offer business subscribers the level of reliability they require. PSTN integration 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 URIs similar to email addresses. Often VoIP implementations employ methods of translating non-identifiers to numbers and vice-versa, such as the Skype-In service provided by Skype and the 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 acoustic coupling of the transmit and receive signal at the receiving end. Security VoIP telephone systems are susceptible to attacks as are any internet-connected devices. This means that hackers who know about these vulnerabilities (such as insecure passwords) can institute denial-of-service attacks, harvest customer data, record conversations and break into voice mailboxes. Another challenge is routing VoIP traffic through firewalls and network address translators. Private Session Border Controllers are used along with firewalls to enable VoIP calls to and from protected networks. For example, Skype uses a proprietary protocol to route calls through other Skype peers on the network, allowing it to traverse symmetric NATs and firewalls. Other methods to traverse NATs involve using protocols such as STUN or ICE. Many consumer VoIP solutions do not support encryption, although having a secure phone is much easier to implement with VoIP than traditional phone lines. As a result, it is relatively easy to eavesdrop on VoIP calls and even change their content. An attacker with a packet sniffer could intercept your VoIP calls if you are not on a secure VLAN. There are open source solutions, such as Wireshark, that facilitate sniffing of VoIP conversations. A modicum of security is afforded by patented audio codecs in proprietary implementations that are not easily available for open source applications, however such security through obscurity has not proven effective in other fields. Some vendors also use compression to make eavesdropping more difficult. However, real security requires encryption and cryptographic authentication which are not widely supported at a consumer level. The existing security standard Secure Real-time Transport Protocol (SRTP) and the new ZRTP protocol are available on Analog Telephone Adapters (ATAs) as well as various softphones. It is possible to use IPsec to secure P2P VoIP by using opportunistic encryption. Skype does not use SRTP, but uses encryption which is transparent to the Skype provider. In 2005, Skype invited a researcher, Dr Tom Berson, to assess the security of the Skype software, and his conclusions are available in a published report. The Voice VPN solution provides secure voice for enterprise VoIP networks by applying IPSec encryption to the digitized voice stream. Securing VoIP To prevent the above security concerns the government and military organizations are using; Voice over Secure IP (VoSIP), Secure Voice over IP (SVoIP), and Secure Voice over Secure IP (SVoSIP) to protect confidential, and/or classified VoIP communications. Secure Voice over IP is accomplished by encrypting VoIP with Type 1 encryption. Secure Voice over Secure IP is accomplished by using Type 1 encryption on a classified network, like SIPRNet. Public Secure VoIP is also available with free GNU programs. Caller ID Caller ID support among VoIP providers varies, although the majority of VoIP providers now offer full Caller ID with name on outgoing calls. In a few cases, VoIP providers may allow a caller to spoof the Caller ID information, potentially making calls appear as though they are from a number that does not belong to the caller[36] Business grade VoIP equipment and software often makes it easy to modify caller ID information. Although this can provide many businesses great flexibility, it is also open to abuse. The “Truth in Caller ID Act” has been in preparation in the US Congress since 2006, but as of January 2009 still has not been enacted. This bill proposes to make it a crime in the United States to “knowingly transmit misleading or inaccurate caller identification information with the intent to defraud, cause harm, or wrongfully obtain. Support for other telephony devices Another challenge for VoIP implementations is the proper handling of outgoing calls from other telephony devices such as Digital Video Recorders DVR boxes, satellite television receivers, alarm systems, conventional modems and other similar devices that depend on access to a PSTN telephone line for some or all of their functionality. These types of calls sometimes complete without any problems, but in other cases they fail. If VoIP and cellular substitution becomes very popular, some ancillary equipment makers may be forced to redesign equipment, because it would no longer be possible to assume a conventional PSTN telephone line would be available in consumer’s homes. Using VOIP with Cell Phone Before many of us came to rely on cell phones to make long distance phone calls, our only option was to commit to a long distance phone company. Long distance carriers charged what were at times exorbitant by-the-minute fees to make calls to friends and loved ones often living only a few hours away. When cell phones came into prominence, they brought with them service plans that gave us such luxuries as free night and weekend calling anywhere domestically. Alas, even cell phones had their drawbacks, in that their reception was often broken up, and calls could be dropped unceremoniously. When along came VOIP, a new choice in long distance phone calling was on the horizon. VOIP has many different options, and now it seems that we have the choice of combining VOIP technology with cell phones. The prospect of VOIP cell phone service brings with it the potential for even more freedom and convenience, along with lower prices. Or does it? Normally, VOIP service is available in three modes: ATA, IP phone, and computer-to-computer. All of these services are common and available for use at your home computer. ATA, or analog telephone adapter, lets you connect your regular home telephone to your computer and use it for VOIP service by converting analog sound bits into digital data. IP, or Internet protocol, phones are telephones that are specially designed for use with VOPI service. These phones look just like a standard home phone, but are wired differently to be VOIP capable. You can have a cordless IP phone that allows you to move freely through your home or office as you talk. Computer-to-computer VOIP is achieved by installing software that you can get through a provider. You make long distance calls from your computer, and talk through a microphone that is hooked up to your machine. All of these services are convenient in their own ways, but do not have quite the portability that cell phones offer. That is why the idea of VOIP cell phones is so appealing. Potentially, it is the best of both worlds: portability and low cost phone service. Cost savings is by far the most attractive aspect of VOIP. With typical VOIP, you can expect to pay anywhere from $19.95 to $34.99 per month for a service that consists of many features, including free domestic calls, dirt cheap International calling rates, Caller ID, Call Waiting, 3-way Calling, among others. This, of course, is in addition to your current monthly ISP charge, which for broadband is usually around $40 per month. The combined cost for your ISP and VOIP services is likely to still be less expensive than if you were to remain in service with a traditional telephone company. However, this is not necessarily the case if you were to switch your cell phone over to VOIP as well. Providers that offer VOIP cell phone services usually charge a monthly fee in addition to a per-minute fee. If you don’t use your cell phone often enough to meet or exceed your current allotted plan minutes, then it is simply not cost effective for you to subscribe to VOIP cell phone service. VOIP and cell phones go well together for those customers that regularly exceed their plan minutes or make International calls on their cell phone on a regular basis. And, if your Internet connection if prone to outages, you could experience the same dropped call occurrences that you might often get with a standard cell phone service. There is no doubt that VOIP is a reasonably priced and convenient way to bundle all of you communications together. VOIP service is improving all the time as technologies moves forward, which will allow providers to offer more reliable and even more affordable service down the line. Currently, VOIP cell phone service is in its infancy, and the kinks are being worked out. If you do the math, and feel that your monthly cell phone bill would benefit from a reasonable VOIP service plan, then it is worth the switch. If you do not make International calls on your cell phone, and you rarely or never go over your plan’s allotted monthly minutes, then you are probably better off sticking with your traditional cell phone service for now than putting out more money for VOIP cell phone service. International VoIP implementation IP telephony in Japan In Japan, IP telephony (IP Denwa) is regarded as a service applied by VoIP technology to the whole or a part of the telephone line. As of 2003, IP telephony services have been assigned telephone numbers. IP telephony services also often include videophone/video conferencing services. According to the Telecommunication Business Law, the service category for IP telephony also implies the service provided via Internet, which is not assigned any telephone number. IP telephony is basically regulated by Ministry of Internal Affairs and Communications (MIC) as a telecommunication service. The operators have to disclose necessary information on its quality, etc., prior to making contracts with customers, and have an obligation to respond to their complaints cordially. Many Japanese Internet service providers (ISP) are including IP telephony services. An ISP who also provides IP telephony service is known as a “ITSP (Internet Telephony Service Provider)”. Recently, the competition among ITSPs has been activated, by option or set sales, in connection with ADSL or FTTH services. The tariff system normally applied to Japanese IP telephony is described below; · A call between IP telephony subscribers, limited to the same group, is usually free of charge. · A call from IP telephony subscribers to a fixed line or PHS is usually a uniformly fixed rate all over the country. Between ITSPs, the interconnection is mostly maintained at VoIP level. · Where the IP telephony is assigned normal telephone number (0AB-J), the condition for its interconnection is considered same as normal telephony. · Where the IP telephony is assigned specific telephone number (050), the condition for its interconnection is described below; o Interconnection is sometimes charged. (Sometimes, it is free of charge.) In case of free-of-charge, mostly, communication traffic is exchanged via a P2P connection with the same VoIP standard. Otherwise, certain conversions are needed at the point of the VoIP gateway which incurs operating costs. Since September 2002, the MIC has assigned IP telephony telephone numbers on the condition that the service falls into certain required categories of quality. High-quality IP telephony is assigned a telephone number, normally starting with the digits 050. When VoIP quality is so high that a customer has difficulty telling the difference between it and a normal telephone, and when the provider relates its number with a location and provides the connection with emergency call capabilities, the provider is allowed to assign a normal telephone number, which is a so-called “0AB-J” number. Voice over IP can be used together with static IP addresses so that one can talk to any computer just the way one uses internet, but instead he can access IP-address as definitive unique ‘internet voip’-phone number…
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