1. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Asterisk Jargon Carl Davis

2. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Agenda What is Asterisk? –PBX Definition and Functionality –Architecture Overview –Network Interfaces –VoIP Connections –Dial Plan –Codec –Channel Jargon –Context –Extension –Application –Variable –Macro

3. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California What is Asterisk? Popular Open Source, multi-protocol PBX (Private Branch Exchange) Provides a library of basic telephony applications for use as building blocks for advanced functionality Includes Common PBX functionality such as voicemail, call queuing, conferencing, music on hold and more Asterisk is one of the few PBXs in existence that connects legacy telephony technologies (Analog, PRI) to VoIP interfaces (SIP,H.323)

4. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Asterisk Architecture

5. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Network Interfaces PSTN –Analog (FXS/FXO) –Digital (E1/T1,BRI) IP –SIP –H.323 –IAX –SCCP/Skinny

6. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California FXS/FXO Analog Line Interface FXS – Foreign Exchange Station –Generates Dialtone –Generates Ring –Connects to Analog Phones (aka Stations) FXO – Foreign Exchange Office –Accepts Dialtone from Central Office (CO) –Provides Connection to the CO

7. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California T1 Primarily Used In US T1 – PSTN Digital Interface –CAS – Channel Associated Signaling (Wink, Immediate, etc) 24 Voice Channels MF/DTMF In-band Signaling –PRI – Primary Rate Interface (D Channel) 23 Voice Channels 1 Data Channel Q.931 Messages

8. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California E1 ITU-T Specification Digital Interface –CAS – Channel Associated Signaling 30 Voice Channels R2MF –PRI – Primary Rate Interface (D Channel) 28 Voice Channels 2 Data Channel Q.931 Messages

9. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Telephony Channels Telephony Connections –Channels map physical FXO and FXS connections to logical Asterisk channels –Trunkgroups – an advanced topic Non-Facility Associated Signaling (NFAS) Generic Requirement-303 (GR-303) These relationships are defined in the zapata.conf channel configuration

10. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Connections (Users/Peers/Friends) VoIP Connections –Users -> connections that authenticate to us (phones, etc) –Peers –> authenticate us (to a service provider) –Friends ->Connections that may do both These relationships are defined in the channel configuration (sip.conf, iax.conf)

11. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Channels Telephony connections to the PBX Call Processing in Asterisk Is Centered Around Channels Drivers for various kinds of connections –IP (SIP,H.323,IAX,SCCP,MGCP) –PSTN (Analog, PRI, BRI)

12. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Channel Types Channel Types can be Physical or Logical Agent: ACD Agent channelAgent Console: Linux console client driver for sound cards (using OSS or ALSA)Console H.323: An older VOIP protocolH.323 IAX and IAX2: Inter-Asterisk Exchange protocol, Asterisk's own VOIP protocolIAXIAX2 MGCP: Media Gateway Control Protocol, another VOIP protocolMGCP SIP: Session Initiation Protocol, the most common VOIP protocolSIP Skinny and SCCP: Drivers for Cisco Skinny Client Control Protocol (a VOIP protocol)Skinny and SCCP VOFR: voice over frame relay Adtran styleVOFRAdtran VPB: For connecting ordinary telephone and telephone lines using Voicetronix cardsVPB Zap: For connecting ordinary telephones and telephone lines using Digium cards. Also for TDMoE and for zaphfcZapTDMoEzaphfc

13. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Channel Drivers Channel drivers offering other technologies can be optionally installed: Bluetooth: Allows the use of bluetooth devices to change routing - see CVS "chan_btp"Bluetooth CAPI: ISDN CAPI channelCAPI mISDN: mISDN channelmISDN vISDN: vISDN channel (native BRI channel for HFC chipsets)vISDN SCCP: An alternate Skinny/SCCP channelSCCP Sirrix: ISDN BRI for Sirrix cards (with optional ISDN encryption)Sirrix UNISTIM: Nortel Unistim channelUNISTIM Unicall: Replacement for zaptel, with R2 supportUnicall SS7: SS7 (ISUP on MTP2/3) channelSS7

14. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Codec Codec – Short for Coder/Decoder Codecs determine the sustained data bit rate which is required for each channel. The codec converts the analog voice signal to a digitally encoded one that should take less space. The quality and data bit-rate vary from one codec to the next. Examples: –ulaw, alaw, gsm, g.723, g.726, g.729

15. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Dialplan The "road map" for your Asterisk PBX. specifies how Asterisk handles calls. consists of a list of instructions or steps that Asterisk should follow. To successfully set up your Asterisk system, it is absolutely vital that you understand dialplans.

16. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Contexts Named group of Extensions Extensions are unique only inside a context Example of a context label: [incoming] Special Contexts –[globals] –[general] Contexts are used for security and to differentiate services

17. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Extensions An extension is an instruction triggered by an incoming call or by digits being dialed on a Channel. Defined Within Context Specify what happens to calls as they make their way through the dialplan. Can be numeric or alphanumeric Can be defined using wildcard syntax to provide handling for predefined extension groups

18. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California More Extensions An extension is composed of three components: –descriptor –priority (each extension can include multiple steps; the step number is called the priority) –application that performs action for the call Example –exten => 123,1,Answer( ) –exten=> _NXX976XXXX,1,Congestion()

19. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Special Extension s - extension Calls entering a context without a specific destination (i.e. ring on FXO line), they are handled automatically by the s extension. Example –[incoming] –exten => s,1,Answer( ) –exten => s,n,Playback(hello-world) –exten => s,n,Hangup( )

20. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Priority Defines step number in an Extension script Numbered sequentially, starting with 1 Unnumbered Priority –n priority, - next –Takes the number of the previous priority and adds 1 –No need to re-number dial plan when changes are made. –Example: exten => 123,1,Answer( ) exten => 123,n,do something exten => 123,n,do something else exten => 123,n,Hangup( ) –Label Priority exten => 123,n(label),do something Executes one Specific Application

21. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Variables A channel variable (such as the Caller*ID number) is associated only with a particular call. Predefined channel variables are available for use within the dialplan and are explained in the README.variables file Channel variables are set via the Set( ) application: –exten => 123,1,Set(MAGICNUMBER=42) Environment variables are a way of accessing Unix environment variables from within Asterisk. –Example: ${ENV(var)} –Global Variables [globals] – Special Context in extensions.conf –JOHN=ZIP/1 –JANE=SIP/JANE –exten => 123,1,SetGlobalVar(JOHN=Zap/1)

22. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Applications Applications are the workhorses of the dialplan. –performs a specific action on the current channel Types –Generic (Authenticate, VMAuthenticate, etc) –Billing (SetAccount, SetAMAFlags) –Call Processing (Answer, Busy, Dial, Hangup) –Caller Presentation (SetCallerID, SetCallerCIDName) –Database (DBdel, DBget, DBput) –Application Interface (AGI, EAGI, PERL, PHP) –Audio (Playback, Playtones, MusicOnHold) –Voicemail & Conferencing (MeetMe, VoiceMailMain) –Queue/ACD (AddQueueMember, AgentLogin)

23. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Macros Macros are used to reduce the amount of redundant code in the dialplan. Passing arguments to a macro allows generalization Single line invocation from dialplan Macros are identified in the dialplan by starting a context name with "macro-". s extension is used within macros since we want the actions to be performed automatically Arguments in macros are accessed as {ARGn}

24. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Example Macro [macro-dialuser] exten => s,1,GotoIf($[${DB_EXISTS(CFD/${MACRO_EXTEN})} = 0]?checkdnd) exten => s,n,set(CFD=${DB_RESULT}) exten => s,n,set(MYEXTEN=${MACRO_EXTEN}) exten => s,n,goto(staff_incoming,${CFD},1) exten => s,n(checkdnd),GotoIf($[${DB_EXISTS(DND/${MACRO_EXTEN} )} = 0]?dialuser,1) ; Tell them we are not all there exten => s,n,Playback(tt-monkeysintro) exten => s,n,Hangup exten => dialuser,1,dial(${ARG1},15) exten => dialuser,n,goto(d-${DIALSTATUS},1)

25. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Example Macro (cont) exten => d-NOANSWER,1,Answer exten => d-NOANSWER,n,wait(2) exten => d-NOANSWER,n,Playback(vm-nobodyavail) exten => d-NOANSWER,n,Hangup exten => d-BUSY,1,Answer exten => d-BUSY,n,wait(2) exten => d-BUSY,n,Playback(tt-allbusy) exten => d-BUSY,n,Hangup exten => _d-.,1,Answer exten => _d-.,n,wait(2) exten => _d-.,n,Playback(pbx-invalid) exten => _d-.,n,Hangup

26. www.itexpo.com October 10-13, 2006 San Diego Convention Center, San Diego California Q&A Carl Davis President & Chief Architect Stellar System Technologies, Inc carl_davis@stellarsystech.com www.stellarsystech.com Executive Director High Tech Business Council of Rochester www.htbc.org