Voice over Internet Protocol (VoIP) and Asterisk

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9 Δεκ 2013 (πριν από 3 χρόνια και 6 μήνες)

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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 PABX


Definition : 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 cost


Use 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 Manager


SipX


OpenSER


Asterisk


And 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 3261


Based 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 protocols


provide 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 architectures


Asterisk 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 architectures


Pure 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