Asterisk PBX

What is Asterisk ? A Full-featured open source (GPL) PBX for  Home users  Small to Medium Business  Enterprise  VoIP Service Providers  Telephone Companies  IVR Platform

Developed By Digium – Primary developers and maintainers of Asterisk  Developers and Manufacturer of IP PBX hardware  Provider of support for Asterisk and hardware

History of Digium and Asterisk Mark Spencer founds Linux Support Services (LSS ) in 1999 and need a phone system Due to the high cost and proprietary nature of existing PBX. He planned to write his own In 2002, LSS reincorporated as digium

Asterisk as a PBX PBX Stands for Private Branch eXchange A PBX Shares resources among users, such as “outside lines” Allows users to call each other on “inside lines” PBX: Features: voic , Conferencing, auto attendants

Traditional PBX and IP PBX

Where is Asterisk Used? Traditional TDM PBX Digium Hardware Cards Uses Cheap Analog phones and T1/E1 lines Inexpensive, no learning Curve Supports all asterisk Features

VoIP Only PBX No Special Hardware required Uses VoIP Phones as endpoints Supports analog devices using Analog Terminal Adapters (ATA’s) Uses Standard Ethernet Cabling Supports all Asterisk Features Can Connect to a legacy phone network using an network using an Internet Telephony Service Provider ( ITSP)

Hybrid PBX Combines both VoIP and traditional telephony using Asterisk

VoIP Gateway/ Toll Bypass Put Asterisk in front of an existing telephone switch Route Calls across the internet to avoid toll charges

Asterisk as a Feature Server Connect Asterisk to an existing phone switch, and simply use it for its features

Call center/ Contact Center Automated Call Distribution Remote Agent Calling Call Monitoring / Recording Service-on-Hold Skill Based routing Geographic Distribution and Routing Fail Over and Contigency Solution

Usage Scenarios Diagram

Architecture

PBX Core The Core is the heart of Asterisk. It handles much of the core functionality Loading dynamic modules Providing System timing Reading the system config Executing Applications Processing Dial Plans requests Creating Channel instances Convering between : Formats Codecs Protocols

Asterisk Modules Asterisk is built in a modular fashion Each module provides some piece of functionality to the overall system The module contain resources, applications, CLI Commands, drivers, codecs, etc. Asterisk administrators can choose which modules get loaded when Asterisk Starts

Channel Drivers Channel drivers handles all input/output with outside -for voice, video, text, etc. Each channel represents a specific technology or protocols ie SIP, IAX2, DAHDI Each resides in its own dynamic modules- chan_sip.so, chan_iax2.so,etc. Each Channel drivers speaks its protocol to the outside world and converts so that Asterisk can use

Applications and Functions Implement units of functionality within the system : Voice mail ( both leaving and retrieving messages). Playback of recorded sound files. Audio Conferencing Dynamically loaded by the core when required Stored in dynamically loadable modules – app_voic .so, app_meetme.so You can pass parameters to applications to change their behaviour

Resources Similar to Applications but are statically loaded by the core Provide common functionality that can be used at any time Music on Hold Call Recording Call Parking & Pick up Configuration loading / Parsing

Codecs Stands for “coder/decoder” Represents different algorithms for encoding and decoding media streams ( Sound, video etc ) Most of these algorithms also compress and decompress the stream Used by Asterisk to: Interpret incoming audio streams Encode outgoing audio streams Stored in codec_gsm.so

Format Drivers Driver modules for reading/writing various media file formats Used for both recording and playbacks ( Asterisk Supports over 20 different file formats) Media files are related to a codec

The Command Line Interface The human interface into Asterisk Allows administrators to : Query the status of system Reload and/ or restart the system Update certain values in real time

The Asterisk Manager Interface Designed for “computer telephony integration” Allows for computer-to-computer communication, monitoring, command and control A very simple text based protocol Created and controlled by PBX Core

Asterisk Gateway Interface One example of an Application Programming for Asterisk Allows Asterisk applications to be written in almost any programming language Details: Controls most call level aspects of Asterisk Link to external applications ( database, LDAP servers, etc..) Good for creating IVR Scripts

Asterisk Configuration By Default Asterisk loads its configuration from a series of text files ( ie the Asterisk configuration files) This system can be enhanced or replaced with “Asterisk Realtime Architecture” or ARA ARA Reads configuration from other resources

Configuration files

Cont… Asterisk is configured by a number of text files They are stored by default in /etc/asterisk They all have a.conf as extension Easy for editing ( extensions.conf, sip.conf and iax2.conf)

Installing Asterisk and Related components Latest Version of Asterisk is 1.6 Libpri (pri isdn library for T1/E1 Interfaces) DAHDI ( For Analog and digital cards) Asterisk (Optional) Asterisk Addons

Cont… ISDNconnections are delivered in two variants, PRI - Primary Rate Interface and BRI- Basic Rate Interface. PRI is the standard for connections to offices. It's based on a T1 line in the US, and E1 line in Europe. The T1 PRI consists of 24 channels, the E1 PRI of 32.

Getting Ready to install asterisk GCC Compiler Ncurses and ncurses-devel for CLI Zlib for compression Newt and newt-devel ( for DAHDI) CURL (Asterisk to interact with websites) Sendmail

Asterisk files and directories /usr/bin/asterisk -> contains asterisk binaries /etc/asterisk -> asterisk configuration files /usr/lib/asterisk/modules -> contains loadable modules for applications,codecs,formats and channels /var/lib/asterisk/sounds -> sound files gsm… /var/lib/asterisk/moh -> music on hold files

Cont… /var/lib/asterisk -> AstDB Database /var/spool/asterisk -> contains voice mail and user greetings file /var/log/asterisk -> Log file for asterisk /var/log/asterisk/cdr-csv -> Call Detailed record in CSV format