VOIP Gateways

Nayomi Ranamuka

Overview

• Introduction• Network gateway• What is a VOIP Gateway ?• VOIP Gateway protocols and codecs• How does a VOIP Gateway work?• Convergence with VOIP Gateway• Types of VOIP Gateway• Media Gateway Controller• Signaling Gateway• Factors to purchase a gateway• Standard VoIP gateway Configurations• Examples of VOIP gateways• Summary

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Introduction

VOIP allows cheap phone call , call conferencing , voice mail over the internet

Some VoIP service providers offer live broadcasts of radio shows and sports events

Components of a VoIP network User agents Gateways Proxy servers

Selecting the right gateway is a crucial

Understanding the role VoIP gateway is very important

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Voice traffic over IP networks

1. PC to PC

• Need a pc with sound card

• IP telephony software

2. PC to phone

• Need a gateway that connects IP network to phone

network

( Router to PBX )

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(3) Phone to Phone

• Need more gateways that connect IP network to phone network• Ip network could be Internet or dedicated intranet

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Network gateway It is a network point that acts as an entrance to another network

A gateway links two systems that do not use the same: Communication protocols         ,       Languages                                  Data formatting structures , Architecture

It can be implemented in software, hardware, or as a combination of both Ex:- Electronic mail gateways(X.400 gateway) receive messages in one format, and then translate it and forward in X.400 format used by the receiver, and vice

versa.

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What is a VoIP gateway?

Act as conversion interface between PSTN and an IP network

This device converts voice and fax calls, in real time, between the public switched telephone network (PSTN) and an IPnetwork

The primary functions of a VoIP gateway include• voice and fax compression/decompression• packetization• call routing• control signaling

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What is a VoIP gateway?

Media gateways, also commonly referred to as VoIP gateways

Users on a VoIP network can't make or receive calls to and from "outsiders" with traditional phone lines without gateway.

There are VoIP-to-GSM(Mobile communication ) gateways and VoIP-to-CDMA(Code-Division Multiple Access ) gateways that route VoIP calls directly for GSM or CDMA

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VoIP gateway protocols and codecs Codec ( coder – decoder ) :- Software or hardware that converts analog signals to digital form

and signals from digital to analog form

It also determines sound quality and bandwidth required to send the packet

If a user doesn’t able to hear anything, the application in user side does not support codec with which data had been coded

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Codec ( coder – decoder )

In voice gateways a concept of "codec" supposes not only coding/decoding algorithms but their hardware realization

The most common voice codecs are: GSM – 13 Kbps iLBC – 15 Kbps G .711– 64 Kbps G. 722 – 4 8 / 56 / 64 Kbps G. 726 - 16 / 24 / 32 / 40 Kbps G. 728 - 16 Kbps G. 729 - 8 Kbps

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VoIP protocols A VoIP protocol determines how your voice packet is transported across a network

A VoIP gateway will typically support a single protocol

Most common VoIP protocols

SIP (Session Initiation Protocol) Used and supported by the vast majority of VoIP phone systems and services SCCP (Cisco Skinny Client Control Protocol) – Used by Cisco’s Call Manager and IP phones. MGCP – an older VoIP protocol H.323 – an older VoIP protocol But is no longer widely used and or supported both MGCP & H.323

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Make sure your VoIP gateway supports the same protocols and codecs that your VoIP service and or VoIP phone system support

If you’re the responsible person, for the set-up, installation and maintenance of a VoIP gateway you will

want to further your knowledge in the area of protocols and codecs.

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PBX

IP Voice

IP Network

If the voice traffic is originating from the PSTN VoIP gateway convert analog voice signal into a digital signal This digital signal is then compressed using a codec Then broken into a series of packets

to transfer across the IP network using a signaling protocol

How does a VoIP gateway work?

PSTNVOIP

GatewayProtocol conversion

Voice compression

Packetization

PBX:- a private telephone network used within an enterprise

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PBX

IP Voice

IP Network

If the voice traffic is originating from an IP network

VoIP gateway decompress the digital packets into a digital signal Then converted into an analog signal

to be sent across the PSTN

How does a VoIP gateway work?

PSTN

VOIP Gateway

Protocol conversion

Voice decompression

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Convergence with VOIP Gateway

VOIP Gateway receive outbound phone calls and determines that the outgoing calls to the internet or to the PSTN depending call type

VOIP Gateway receive inbound phone calls and determines that the incoming calls to the PABX, IP Phone or to another VOIP Gateway

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Types of VoIP Gateways

There are two main types of gateways Analog gateway Digital gateway

Analog Gateway

• Used to connect PSTN to a VoIP phone system or VoIP phone system to the PSTN

• Due to this dual purpose an analog VoIP gateway comes in two different forms fxs - fxo

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Analog Gateway

FXS gateway – A FXS gateway is used to connect your PSTN to a VoIP phone system.

FXO gateway – An FXO gateway is used to connect your VoIP phone system to your PSTN lines.

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PSTN

PBX

EthernetPPP

Frame RelayATM

IP Voice

IP Network

Digital Gateway

PSTN

Used to connect traditional PBX system to an IP network

Analog and digital gateways both do the same thing

The difference between an analog and a digital VoIP gateway are the interfaces uses to connect to various solution components

VoIP Gateway

PBX

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Media Gateway Controller (MGC)

Receives signaling information (like dialed digits) from the Media Gateway and can inform it to alert the called party, to send and receive voice

data Protocols between MGC and Media Gateway: SGCP, IPDC, SS7, H.323,SIP,MGCP and Megaco(also known as H.248)

A media gateway controller is sometimes called as call agent, call controller, or softswitch

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Signaling Gateway

A network device that converts control signals from one format to another

SS7:- (Signaling System 7) The protocol used in PSTN

SIGnaling TRANsport :- An IP telephony protocol that is used to transfer SS7 signals over IP networks

Ex:- SIGTRAN signaling gateway converts SS7 signals of the PSTN to SIGTRAN for transport over IP

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Coverged network

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Factors to purchase a gateway

Call load• Make sure the gateway you select can handle

the volume of VoIP calls that will need to go through it

VoIP protocol support• Gateway must support the protocol used by your network's VoIP system

Compatibility• Should have compatible ports with those on your private branch

exchange (PBX) equipment. Cost

• Price depend on type, brand, features, and capacity. • You want the best VoIP gateway solution that fits your budget and meets

your needs.

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Standard VoIP gateway Configurations

FXS / FXO Gateway :-• 4 port• 8 port• 16 port• 24 port• 48 port

Digital gateways :-• 1T1, 2T1, 4T1• 1E1, 2E1, 4E1• 1BRI, 2BRI, 4BRI

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Examples of VoIP gateways

Motorola• Provides traditional, advanced, and wireless VoIP gateways designed

to work with broadband Internet connections.

Mediatrix• Can connect to traditional PBX systems as well as IP PBX, with

both analog and digital gateways

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Examples of VoIP gateways

NovaTec• Provide VoIP-to-GSM gateways

Hypermedia• Offers the CDMA Gateway Series for connecting IP PBX devices with CMDA cellular networks.

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Cisco AS5300/Voice Gateway

• The Cisco AS5300 is an dialup remote access server and voice-over-IP (VoIP) gateway.

• When equipped with voice feature cards (VFCs) and voice-enabled Cisco IOS® software,

the AS5300 supports carrier-class VoIP and fax over IP services

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Summary

• Understanding the role VoIP gateway is very important• Network gateway is a network point that acts as an entrance to another

network• VOIP Gateway act as conversion interface between PSTN and an IP network • You should have a knowledge in the area of protocols and codecs• Two main types of gateways are analog gateway & digital gateway• A media gateway controller is called as call agent, call controller, or

softswitch.• Signaling gateway converts control signals from one format to another

• Factors to purchase a gateway are call load, voip protocol support, compatibility & cost

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References

• www.wikipedia.org

• www.voipsupply.com

• www.voip-info.org

• www.roseindia.net

• www.3cx.com

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Any Questions ?

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Thank You…..

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