VoIP by gopishrine

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									VOIP Background Internet Voice, also known as Voice over Internet Protocol (VoIP), is a technology that allows you to make telephone calls using a broadband Internet connection instead of a regular (or analog) phone line. Some services using VoIP may only allow you to call other people using the same service, but other services may allow you to call anyone who has a telephone number; including local, long distance, mobile and international numbers. Also, while some services only work over your computer or a special VoIP phone, other services allow you to use a traditional phone through an adaptor. WHAT IS VoIP? VoIP, a short form for Voice over Internet Protocol, enables businesses to make phone calls across computer networks, providing a low cost and efficient way to complement traditional phone systems. VoIP can be used in individual local office networks or between sites, enabling you to integrate call handling and reporting with other business processes and with your website. Using broadband, it can also deliver telephone services to remote users and home workers. VoIP - How does it Work? VoIP technology is phone calls that travel networks using Internet Protocol (IP). What this means is that the calls are passed through the Internet or privately managed data networks that are using IP to send the calls from one location to the other. Therefore, whether the call is passed through the Internet or data networks, the voice stream is broken down into packets, compressed, and sent toward their final destination by several different routes. This is where circuit-switch technology and IP technology differ, in that circuit-switched technology uses a 'permanent' connection for the entire phone call. Once the call reaches the called, the voice stream packets are reassembled, decompressed, and switched back into a voice stream by several hardware and software elements depending on the caller's final destination. The type of software and hardware needed to start and end a phone call is determined by where the call originated, such as a PC, phone, or an Integrated Access Device (IAD) and whether the call is going to be completed on a PC, telephone, or IAD.

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VOIP How does VoIP look like? VoIP services can take many forms:
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PC to PC: when both caller and recipient would use lightweight headphone with mike PC to PSTN: when only the caller would use a headphone with mike PSTN to PSTN: when both the caller and called would use a special adaptor for his telephone


IP phone to PSTN: when the caller would not need an adaptor because the phone itself would be IP-enabled

The following is a list of the numerous advantages for using VoIP:
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Voice and data can be sent over the same lines. 8 times the number of phone calls can be placed on those lines than in the circuitswitched environment. Quality of sound is excellent. Lower operating costs due to reduced hardware requirements and a more efficient network infrastructure. Lower cost structures enable lower rates than the traditional telephone companies. Use of different devices to talk to one another.

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(Later we see more benefits of VoIP)

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VoIP Signaling Protocols H.323: ITU standard, ISDN-based, distributed topology; more than 90% of all Service Provider VoIP networks. The current interconnect for Call Manager to Service Providers Useful for video applications Skinny: Centralized Call-Control architecture. Call Manager controls all features. More than 700,000 IP Phones deployed.

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VOIP MGCP: IETF RFC2705 Centralized Call-Control Architecture. Call-Agents (MGC) & Gateways (MG) SIP: ETF RFC2543 Distributed Call-Control. Used for more than VoIP SIMPLE: Instant Messaging / Presence H.323 Characteristics  Handles transmission of digital audio telephone call.  Includes signaling to setup and manage the call.  Allows a transmission of video and data while a phone call is in progress.  Sends binary messages that are defined by ASN.1 and encoded using Basic Encoding Rules (BER).  Incorporates protocols for security.  Uses a special hardware unit known as Multipoint Control Unit (MCU) to support conference calls.  Defines servers to handle tasks such as address resolution (i.e mapping the called party’s phone number into an IP address), authentication, authorization (i.e Determining whether user is authorized to access a given service), accounting and features such as call forwarding.

SIP Characteristics The IETF has defined the Session Initiation Protocol (SIP). The highlights of SIP are: 4/ 10

VOIP  Operates at the application layer.  Encompasses all aspects of signaling, including location of a call party, notification and setup (i.e. ringing a phone), determination of availability ( i.e whether the party accepts the call), and termination.  Provides services such as call forwarding.  Relies on multicast for conference call.  Allows the two sides to negotiate capabilities and choose the media and the parameters to be used. SIP has become more popular these days and the latest version of Microsoft Operating System Windows XP incorporates the SIP communication protocol in their Windows Messenger.

THE BENEFITS  VoIP has one advantage that is cheaper calls In a study by Benchmark Research, businesses rated telecommunications and IT has the biggest priority for making cost savings. When you consider that the average employee spends hundreds of hours a year on the telephone, it is easy to see why VoIP is attracting a lot of attention.  VoIP uses only 10% of bandwidth than traditional phone calls. Traditional phone calls work by allocating an entire phone line to each call. With VoIP, voice data is compressed and transmitted over a computer network. This means VoIP uses up to 90% less bandwidth than traditional phone call and is consequently more cost-effective and more efficient. Phone companies are already using the technology to carry international calls. Currently 6% of international traffic is internet-based. According to a recent research report this will be up to 75% by 2007 (Frost & Sullivan). In fact if you use a cheap, long distance telephone service, you're probably already using IP telephony without knowing it. 5/ 10

VOIP  Cheaper external calls Both long-distance and international calls will be available for the price of a local call. Switching to VoIP can make your business more productive, accessible to customers, flexible and greatly reduce your phone bill.  Free internal calls The internal call to all parts of your company that share a computer network are available free. With a Virtual Private Network (VPN) in place, you can speak to connected colleagues at different branches or on the road free. This is particularly useful for the growing number of SMEs(Small and Medium Enterprises) who have multiple sites.  Simpler infrastructure. With VoIP on your computer network you can add telephones and increase call capacity without running additional cabling.  Scalability. Traditional PBX (Private Branch Exchange) phone systems have a set number of ports for telephones to connect. VoIP systems provide greater flexibility as you can run a number of ‘virtual’ users through each network socket.  Reduce operating costs. It is easier to manage and maintain as it is based on software rather than hardware.  Improve productivity. VoIP treats voice as if it were any other kind of data, so users can attach documents to voice messages or participate in virtual meetings using shared data and videoconferencing.  Wireless-compatible. With a wireless LAN in place, mobile devices like PDAs and smartphones can use your VoIP system. 6/ 10


 Connect to customers. By adding a ‘click to talk’ button to its website, a VoIP-enabled enterprise can put web users in touch with its customer service personnel.  Dependable call management. Voice-related services, like follow-me roaming, caller-ID, call forwarding and broadcast messaging, become simpler to maintain and can be updated as needed by your employees.  Flexibility. A Virtual Private Network (VPN) is an allocated amount of bandwidth on the public internet where public access is prevented through encryption. If your company has its own VPN and combines it with VoIP, you can set up a fully functioning office where there is a broadband connection. Green-field sites can be up and running in minutes not weeks. Different grades of VoIP service

Best effort or Internet Telephony - on such systems, no guarantees are made about the success or the quality of the call, since the network might be busy or the speech might simply become unintelligible.


Engineered quality or IP Telephony - on such systems, specific efforts are made to ensure that network delays are minimised and that data traffic does not interfere with voice traffic.


Carrier grade or PSTN-like - such networks have high reliability, strong resilience, and built-in redundancy, although this is only achieved at significant cost.


Better than PSTN - such networks will provide higher quality speech paths and combine basic voice services with other services such as multimedia and Instant Messaging. 7/ 10


Abstract: VoIP networks provide cheaper means of carrying voice but more importantly provide a much enhanced range of services. As an OECD paper of December 2001 put it: "The potential for IP-based voice as a cheaper alternative to traditional telephony is considered to be less important than the opportunity for the integration of voice in new IP-based applications that are considered drivers for broadband services". Many businesses are hoping VoIP will ultimately lead to greater efficiency, productivity and cost savings. VoIP eliminates redundant networks and network resources, simplifies network management and facilitates communication. However, for an existing TCP/IP network to successfully carry VoIP traffic, several modifications must be made to the network infrastructure. While data compression and QoS mechanisms will help reduce data traffic, an efficient and reliable data cabling solution is needed. Data network reliability concerns are not insurmountable. There are data cabling solutions available that provide efficient throughput and sufficient headroom to ensure that even bandwidth-hungry applications will run smoothly. There are many communication standards that are emerging now. There has been a huge increase of popularity for the SIP protocol and there is also a new P2P technology(for PC Calls) the VoIP world. Only time will make tell which will emerge as the global standard.

Glossary Codec: A compression/decompression algorithm used in IP telephony and other Streaming media applications. G.723.1: An ITU-T Codec, used in many IP telephony systems, that has two associated bit rates: 5.3Kbps and 6.3Kbps. 8/ 10

VOIP G.729: An ITU-T Codec used in many IP telephony systems that has an 8Kbps bit rate. Gateway: A network device that converts voice and fax calls between the PSTN (public Switched telephone network) and an IP network in real time. H.323: An ITU-T collection of standards used in VoIP (voice over IP) applications to define end points, gateways, and other IP telephony devices and their interaction. Proceeds SIP (Session Initiation Protocol). Fairview Industries Primer Series – Voice IP Telephony: The transmission of voice and fax phone calls over a packet-based IP data network; synonymous with VoIP. IP PBX: The server that provides call control and configuration management for an IPbased Phone system. IP Phone or Handset: A phone system handset that connects to the IP PBX over an IP LAN. IP phones often look and function much like typical legacy corporate phone system handsets, but in some cases they also take on PC-like functionality. MPLS: Multiprotocol label switching, an IETF set of quality-of-service labeling standards that ISPs use to manage different kinds of data streams based on priority and service plan. PBX: Private branch exchange, an in-house telephone switching system. PBX trunk: The shared communications path between the customer's PBX and the Public network. Protocol - A protocol (pronounced PROH-tuh-cahl, from the Greek protocollon, which was a leaf of paper glued to a manuscript volume, describing its contents) is the special set of rules that end points in a telecommunication connection use when they communicate. Protocols exist at several levels in a telecommunication connection. There are hardware telephone protocols. There are protocols between each of several functional layers and each corresponding layer at the other end of a communication. Both end points must recognize and observe a protocol. Protocols are often described in an industry or international standard. PSTN: Public switched telephone network, which is also called POTS (plain old telephone service). Q.Sig: Q Signaling, a signaling standard for PBX interoperability used in the United States and Europe. 9/ 10

VOIP RTP: Real-Time Transport Protocol, the Internet protocol used by VoIP systems for streaming digitized audio and video across an IP network. SIP: Session Initiation Protocol, an up-and-coming IETF signaling protocol for Internet conferencing, telephony, presence, events notification, and instant messaging. Competes with H.323. Soft phone: Software that provides IP phone functionality in a PC, notebook, or other Computing device.

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