Asterisk

The Open Source PBX & Telephony Platform

Topics

• Basic Telephony terms• VOIP Protocols (relevant ones)• Asterisk info• How to control and change settings• Configuration files• Live demo• Set up your soft phone• Set up Grandstream SIP Phone

Terms

• PBX - Private Branch Exchange– The control center for a phone system– Also called a switch or switchboard

• PSTN - Public Switched Telephone Network

• POTS - Plain Old Telephone System– Uses 48 VDC for passing analog voice– Rings at around 90-100 VAC

Terms

• DTMF - Dual Tone Multi Frequency– Tones used to dial and send signals to the

switch– Inband

• Uses same frequencies we talk with• Some peoples voices can trigger this (mostly

females)

– rfc2833• Out of band standard for passing dialing tones

Terms

• FXS - term used with POTS for a system that supplies voltage for dial tone and ring voltage

• FXO - term used with POTS that connects to an FXS system. Your telephone is FXO.

(These are mixed up a lot)

Terms

• Softphone - software phone that runs on your computer

• Hardphone - Hardware phone• VOIP - Voice Over the Internet Protocol

– Generic Term for all IP telephony• Skype• Ventrilo• Teamspeak

– As far as I know always uses UDP/IP. Can use TCP/IP but why?

Terms - Protocols

• SIP - Session Initiation Protocol– Used to set up the VOIP call– Only sets up the connection– Passes voice packets off to RTP

• RTP - Real-time Transport Protocol– Carries the voice packets for a SIP phone call– Issues with NAT (uses different ports than SIP)

Terms - Protocols

• IAX - Intra Asterisk Exchange– Designed by Asterisk– Uses same port for both connection and voice packets

so better through NAT

• DUNDi - Distributed Universal Number Discovery– Just put in here because sample .conf files

have code for it.– New protocol NOT universaly used but

supported by Asterisk

The Last Mile

• The last mile is the term used to describe how the telephone company gets the signal to your home or office.

• Typically POTS

• Ironic as they convert everything to digital from that point and send it down the trunk.

Asterisk

• Open Source (*nix only, but windows bransh avalable)

• Current Version 1.4.21.2• Version 1.6 RC6 is out• Code base controlled by Digium Inc.• Can run on a headless system• Business model is give away the software

and sell the hardware.

Asterisk Control

• Command line and .conf files– /etc/asterisk except zaptell.conf which is in /etc– More on .conf files later– If you like emacs, vi or the like enjoy– You need to know the Asterisk syntax and

settings– There are alternatives…..

Asterisk Control

• GUI tools– Asterisk GUI

• Web based AJAX

• Edits .conf files directly

• Same UI as AsteriskNOW (more later)

• Says can edit .conf files manualy or use GUI and will not have problems (WRONG)

• Does not use Apache, has own web server

• /etc/asterisk/http.conf holds settings

Other Free PBXs

• OpenPBX by VMX– Not the same as CallWeaver

• CallWeaver - formerly OpenPBX.org

Asterisk Control

• GUI Tools (cont)– AsteriskNOW

• From Digium

• Self installing with OS, Asterisk, and GUI

• Wipes out ALL hard drives on the machine

– Trixbox• Similar to AsteriskNOW but has better UI

Configuration Files

• Only going to mention the most used– extensions.conf– Sip.conf– Iax.conf– Users.conf– Manager.conf– Logger.conf– Voicemail.conf– Asterisk.conf– Manager.conf– Zaptel.conf

Configuration Files

• extensions.conf– Holds the Dial Plan

– Most complex to set up

– Context• [incoming]

Code here

• [general]– Has some settings

• [globals]– Holds global variable info

Configuration Files

• extensions.conf (cont)– Funky syntax

• exten => (extension) a unique series of steps

• exten => extension, series number, application– Exten => 123, 1, Answer()

exten => 123, n, Wait(2)

exten => 123, n, Background(tt-weasles)

exten => 123, n, Hangup()

Configuration Files

• extensions.conf (cont)– Include

• Include = name of another context

• Include = [default]

– Macros• Used to create reusable code

• Can accept paramaters

Configuration Files

• asterisk.conf– Tell Asterisk where thing are located

• Log files

• Run directory

– Set verbosity of console– Turn debug on– System limits (max calls)

Configuration Files

• features.conf– Mostly for parked calls settings

• http.conf– Setting for the Asterisk GUI web server

• rtp.conf– Limit the ports RTP can use

Configuration Files

• iax.conf and sip.conf– Settings for connections– sip.conf for sip connections, ias.conf well you

get it– Not used with GUIs, users.conf holds all that

data– Contexts like in extensions.conf

• [101] will be phone extension 101• All settings for that user under that context

Configuration Files

• zaptel.conf– Used to set up hardware for connecting your

Asterisk system to POTS, either in or out.– I did not use this so can’t help here

• manager.conf– Settings for the Asterisk GUI

• Turn it on or off

• Timeout

• Password and user

• Amount of control the GUI has

Configuration Files

• logger.conf– Name of log files– What to log

• voicemail.conf– Turn on voicemail for a user– What capabilities the user has in VM

Configuration Files

• users.conf– Combines most of iax.conf, sip.conf,

zaptel.conf, and voicemail.conf into one file.– Changed in later releases to make management

easier– Uses contexts again like in sip.conf and

iax.conf– Will show an example later

Phones• Hardphones

– Grandstream BT200 inexpensive (about $50)• Only has 7 segment display so not caller ID name only number• Having problems with staying connected to Asterisk• Set up TFTP to set up firmware and ring tones for the phones• Use SIP • 100bTx in and out

– Grandstream HT503• Multi use device

– FXO to FXS– FXO to SIP– FXS to SIP– FXS to FXO– One 100bTx in and out

Phones

• Soft phones - program that runs on a computer– Xlite SIP (my favorite)– Zoiper - IAX

Resources

• Asterisk, The Future of Telephone, 2nd ed.– O’Reily Publishing– Free PDF download from asterisk.org– Keep in mine this book does not talk about users.conf

• voip-info.org• asterisk.org• trixbox.org• asterisktutorials.com• I found a web site from a San Diego company that had

great Trixbox tutorials but alas I can’t find it now.