1. VoIP with asterisk
© Mathias Weyland

2. VoIP – who cares? With VoIP, you can:
have a geek-safe telephone system
brag with features
save the big bucks
be mobile
know how to fix your system
be proud of yourself because you managed to set up asterisk
© Mathias Weyland

3. VoIP – downsides ISP down – no telephone ADSL down – no telephone
SIP proxy down – no telephone
Network down – no telephone
Brother leeching Ice Age 2 – no telephone
Loss of sound quality possible
Maybe no emergency calls
© Mathias Weyland

4. What do I need? SIP proxy SIP client
PBX (Private Branch Exchange) hard- or software
Patience
Friends who know how that stuff works
© Mathias Weyland

5. The SIP client can register with SIP proxies
knows how to handle incoming calls
is able to send DTMF signals
advanced sip clients can do some more voodoo
Both software and hardware sip clients exist, albeit sip clients for linux is a rare breed
© Mathias Weyland

6. The PBX software (asterisk)
Not a must, but can be used to blow the roof off
Can handle IAX2, SIP, H.323, SCCP
And Euro-ISDN, 4ESS, Isdn4Linux, DMS100, Lucent 5E, National ISDN2 and NFAS
Supports all common audio codecs: GSM, ADPCM, iLBC, SPEEX, G.711, mp3 etc.
Brings in leet features (voice mailbox, caller ID, call parking, call meetings, blacklists, queues, DND ect.)
© Mathias Weyland

7. SIP? SIP (Session Initiation Protocol)
SDP (Session Description Protocol)
RTP (Realtime Transport Protocol)
© Mathias Weyland

8. Codecs?
© Mathias Weyland

9. asterisk - config We are interested in three config files: sip.conf
extensions.conf
voic .conf
© Mathias Weyland

10. asterisk - sip.conf
This is the place where SIP devices are defined. Sample section:
[mathias]
type=friend
host=dynamic
username=mathias
secret=abc
context=internal
© Mathias Weyland

11. asterisk - extensions.conf
This file contains the dialplan. Key points:
Context
Includes
Extensions
Applications
© Mathias Weyland

12. asterisk - Applications
Dial(): Dial an extension
Answer(): Pick up the phone
Wait(): Look bored
Playback(): Play sound files
Voic ()/ Voic Main(): Mailbox
Goto(): Jump to some other extension
Hangup(): Hang up
© Mathias Weyland

13. asterisk – Extension
This is a sample extension: Call the devices hans and peter and launch the voice mailbox if they both are busy or do not answer
exten => 1000,1,Dial(SIP/hans&SIP/peter)
exten => 1000,2,Voic (u9999)
exten => 1000,102,Voic (b9999)
© Mathias Weyland

14. asterisk – be lazy and use patterns
You can use asterisks to simplify the asterisk dialplan
X: [0-9]
Z: [1-9]
N: [2-9]
[13-7]
.: match one or more characters
© Mathias Weyland

15. asterisk – dialplan variables
Variables can be used to pimp your dialplan or to add some logic:
exten => _XXX,1,SayDigits(${EXTEN})
${EXTEN:1}: Last two digits
${EXTEN:-1}: Last digit
© Mathias Weyland

16. asterisk – voice mailbox
Variables can be used to pimp your dialplan or to add some logic:
exten => _XXX,1,SayDigits(${EXTEN})
${EXTEN:1}: Last two digits
${EXTEN:-1}: Last digit
© Mathias Weyland

17. asterisk – QoS
set tos=0x18 in your sip.conf
© Mathias Weyland

18. asterisk – CLI and debugging
[sip] reload
help sip
sip [no] debug
debug level
© Mathias Weyland

19. asterisk - docs Asterisk – The future of telephony
Google
© Mathias Weyland

20. Questions, beer etc.
© Mathias Weyland