Voice over Internet Protocol

(VoIP) and Asterisk

HOUNGUE Pélagie

Contact: hepy1900@yahoo.fr

Outline Introduction Enterprise Telephony : PABX The IPBX What is Asterisk? Material and software recommendations for

the deployment of Asterisk solutions Different scenarios for Asterisk solution

deployment Practical case of IMSP in Benin Conclusion

Introduction

Why enterprises need telephony?

Telephony is indispensable in conducting business and to be competitive

So Companies spend lot of money to buy their own telephony switch (PABX)

Enterprise Telephony : PABX

Presentation of a PABXDefinition : it is a private telephony switch.Common Functionalities

Direct dialing-in Transfer call Connection to PSTN etc

Cost between $1300 et $148000 (from studies

conducted in Benin)

Problematic Extremely high costUse of proprietary protocols

Interesting and new perspectives introduced by VoIP emergence:Possibility for the deployment enterprise

telephony infrastructure using software (IPBX)

Enterprise Telephony : PABX (Con’t)

VoIP Definition : carry a voice on data network

using IP packets. Components

The IPBX

What is a IPBX?Software which can be installed on a PC or a

server and acting as an auto-switch. Example of IPBX

Cisco Call ManagerSipXOpenSERAsteriskAnd many more.

What is Asterisk? (Con’t)

Functionalities Voicemail, conference call, put in wait of

calls, transfer call, call forwarding, etc. Supported Protocols and codecs

Protocols :H.323, SIP, IAX, MGCP, Skinny, etc.

Codecs : G711, G723, G726 (ADPCM ), Speek, GSM, etc.

Signalling Protocols

H.323 Standard published by ITU in 1996. Stack of protocols

H.225 RAS signaling, H.225.0 Call signaling (Q.931), H.245 Control signaling

H.323 elements: Terminals Gatekeepers Gateways Multiconference Unit (MCU)

Signalling Protocols

SIP (Session Initiation Protocol)Created by the Internet Engineering Task

Force (IETF) in 1999. RFC 3261Based on HTTP and SMTP

SDP (Session Description protocol) RTP/RTCP

SIP elements: User Agents Proxy Servers

Example of Call transaction with SIP

Signalling Protocols

IAX protocolsprovide control and transmission of voip data

between Asterisk servers main goals of

Minimize bandwidth usage Avoid NAT problems Support the ability to transmit dialplan

information

Asterisk’s Implementation

Package sources for installation Asterisk main program (Asterisk 1.4.19 ; 2008 Apr

02) Zapata Telephony Driver (zaptel) PRI librairies (libpri) Asterisk Sounds Package

Asterisk’s Implementation

Download Files on /usr/src Extractions : # tar zxvf file_name.tar.gz Compile Zaptel, libpri and asterisk

#Cd /usr/src/name_directory# make clean# make# make install# make config

Asterisk’s Implementation Dialplan

extensions.conf in /etc/asterisk/ Fours mains parts

Contexts [general]

Extensions exten => 2223,1,Answer()

Priorities exten => 2223,1,Answer() exten => 2223,2,hangup()

Applications Answer() Hangup()

Asterisk’s Implementation Example of Content of sip.conf [general]

bindport=5060 disallow=all allow=alaw allow=ulaw allow=gsm language=fr

[500] type=friend host=dynamic username=pelagie secret=pelagie callerid="HOUNGUE Pelagie" <500> context=interne  account_code=pelagie callgroup=1

Material and software recommendations

Hardware and Software recommendations

Material and software recommendations (Con’t)

Telephony hardware recommendations

Different scenarios for Asterisk solution deployment

Suggested architecturesAsterisk server behind PABX Architecture

Different scenarios for Asterisk solution deployment (con’t)

Suggested architectures Asterisk server in front of the PABX

architecture

Different scenarios for Asterisk solution deployment (con’t)

Suggested architecturesPure VOIP architecture

Different scenarios for Asterisk solution deployment (Con’t)

Suggested architectures Interconnexion of

multi sites enterprises

Different scenarios for Asterisk solution deployment (Con’t)

Suggested architectures Interconnexion of multi sites enterprises

Pratical case of IMSP at Benin

Choice of the pure VoIP architecture Hardware : PC with linux CentOs distribution Some deployed services

Call Detail Record Call Transfer Service of presence Call Parking Conference Voicemail Access voicemail box using web interface …

Conclusion

Asterisk presents many advantages for Africa Small and Medium enterprises. These advantages are :

- Cost reduction for enterprise telephony deployment - Easy administration and custom management of the IPBX - Mobility and remote work- Asterisk facility to integrate information system (Customer

Relationship Management)- Etc.

REFERENCES

http://www.voip-info.org/ www.asterisk.org www.digium.com Asterisk : The future of Telephony , Jim

Van, Jared Smith, Leif Madsen

Thank You