Voip

Voice over IP (VOIP).

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Content Introduction Principle PSTN telephony vs VoIP

Advantages and Benefits of Voice over IP Types of IP Telephony VIOP Function How they fit in: The ISO Model VOIP Architectures Quality of Service Issues in IP Network VOIP Advantages Conclusion

INTRODUCTION

Voice over IP

CMTS Video Feed

MTA

“Managed” IP Network Public Internet

QoS = Controlled Load or Guaranteed

Wireless

Wireline

separate voice and data networks. Voice over Internet Protocol (VOIP), is a technology that allows you to make voice calls using a broadband Internet connection instead of a regular (or analog) phone line Voice over IP application provide legacy voice networks by allowing both voice and signaling information to be transported over IP.

Voice processing will need to handle greater and variable delays, jitter, and cancel echoes that will be introduced from the telephony side. Some VOIP services only work over your computer or a special VOIP phone, other services allow you to use a traditional phone connected to a VOIP adapter

There are three styles of Voice over IP calls. It can be either from PC to PC, or it could be from a PC to phone or from phone to phone. The key components here are the gateways, which adapt traditional telephony to the Internet. A call goes over the local public switched telephone network (PSTN) to the nearest gateway server, which digitizes the analog voice signal using pulse code modulation, compresses it into IP packets, and moves it onto the Internet for transport to a gateway at the receiving end.

Principle: It is based on Digital Switching

VoIP begins with Digital Voice A

D

A/D Converter

In Digital Switching … … Voice is Data.

PSTN telephony vs VoIP PSTN telephony - Circuit switched E.164 numbering Intelligent network / dumb terminal Charging bases 

location, distance, min

Closed system 

inherited security

Tech quality

VoIP - Packet switched - URL SIP names, E.164, IP addr, - Dumb network / - intelligent terminal - Charging bases - more limited

- Open system - security vital issue

- Tech quality

Advantages Cost reduction: These savings from lower prices are however, based on avoiding telephony access charges and settlement fees, rather than actually reducing resource costs. Simplification: VOIP support an integrated Infrastructure by which dynamic bandwidth optimization and a fault tolerant design, all forms of communication available and reduces the total equipment complement. Consolidation: Universal use of the IP protocol for all applications will reduce complexity and provide more flexibility.

Transmitting Voice over Internet Protocol is also beneficial for the following reasons Internet is the connectionless network. So each voice signal travel over separate network paths. Private data networks require only ‘n’ access links. Data transmission has no bandwidth limitation. Voice data has flat time-sensitive charges.

Types of IP Telephony: PC-to-PC Internet Telephony :It developing in 1994 and used by young cyber addicts. A microphone connected to the computer receives the voice, and then the computer transmits the voice through the Internet. For this service a software is processes the voice compress into IP data, later reconstructed into voice waves at the end user's compute PC to Telephone or Fax Telephony: It developing in 1996. A microphone connected to the computer receives the voice, and then the computer transmits the voice through the Internet. But using a gateway bridge between the PSTN and the Internet

PC to a Content Provider’s Call Center or Website: The user can access a company’s website and request to speak to a representative at any time by just clicking the appropriate icon in the screen. There are representative is part of call center. This IP TELEPHONY provide better customer service. Telephones-to-Telephone IP Telephony: Using this technology the caller uses a normal phone, and then the signal travels through the local telephone infrastructure to a gateway based on the local area. The gateway sends the signal converted into IP protocol packets over the Internet. The voice packets travel to other gateway located at the callee's local area. Then the signal travels over the local telephone infrastructure to the callee’s regular phone.

Common Infrastructure for All Call Agents

VIOP Function Click to call or Talk :Call-center customer can request a call back from the Web site (also known as “click to call back”), which uses the PSTN or even places an Internet telephony call. This saves the call center money because it doesn’t have to pay the incoming 800 toll charges.

Two-Stage Dialing: Two-stage dialing means that us don’t

dial 1+10 numbers and directly ring the person us are calling. Instead, we call a number that prompts us for authentication or provides us with a second dial tone, at which point us can dial the number us want to call.

Two-Stage Dialing

Call Flow: Part I

Call Flow Part II

Call Flow Part III

How they fit in: The ISO Model ISO Model Layer

Protocol or Standard

Presentation

Applications / CODECS

Session

H.323 & SIP

Transport

RTP / UDP / TCP

Network

IP – Non QOS

Data Link

ATM, FR, PPP, Ethernet

VOIP Architectures: There are many vendors offering VOIP solutions Offerings are the same, the transfer of voice traffic over a packet zed or non-switched medium. Some architecture are as follow: Internet Protocol (IP) Centric: Based on core switching system. Internet Protocol (IP) Enabled: This type of architecture use facilities of TDM circuit switches. TDM circuit switch that provides the core call processing and switching of all calls. VOIP Environmental Vulnerabilities: This type of architecture Operates on a converged (voice, data, and video) network .

Quality of Service Issues in IP Network QOS usually refers to the fidelity of the transmitted voice and facsimile document it can also be applied to network availability, telephone feature availability, and scalability. 1.DELAY:There are two problem ECHO & Talk overlap because of high end-to-end delay in a voice network. Echo is caused by signal reflections of the speaker’s voice. It create problem after 50millisecond delay Talkers overlap is the problem of one caller stepping on the other talker’s speech. It create problem after 250 millisecond. The variable delay components include the queuing delay, dejitter buffers.

Jitter (Delay Variability) Jitter is the variation in inter-packet arrival time as introduced by the variable transmission delay.

Packet Loss: But due to the time sensitivity of voice transmissions.

Bandwidth Availability: Due to Band width limitation there are pocket loss periods of silence in the conversation,

VOIP Advantages No long distance fees No dedicated circuit More efficient use of networks 64 Kbps raw audio vs. 13 Kbps compressed  Data need not be transmitted during silence    

Conclusion Data has been traditionally transmitted over the voice networks. The Internet has created the opportunity to reverse this trend and now send voice over data networks such as IP, The market for VOIP is established and is beginning its rapid growth phase and corporations must look to capitalize on this new wave of voice over packet networks, like IP

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