This document discusses using Asterisk Gateway Interface (AGI), Asterisk Manager Interface (AMI), and Asterisk REST Interface (ARI) to build telephony features. It proposes using AGI for generic call setup/teardown and feature determination, and ARI apps running on an ARI proxy to control individual features during calls. This decouples features from Asterisk and isolates them, improving testability, replaceability, and avoiding direct developer interaction with Asterisk dialplan. The approach moves routing logic away from Asterisk and enables any feature via a low-level ARI API and high-level feature control.

1. ARI and AGI
A powerful combination
Jöran Vinzens
@vinzens81
linkedin.com/in/jvinzens/

2. What?

3. What?
It is not a manual how to use Asterisk!

4. What?
Story of how we think we could be ready for the future.

5. What are AMI, AGI and ARI

6. What are AMI, AGI and ARI
Interfaces to control the Asterisk

7. What are AMI, AGI and ARI
AMI - Asterisk Manager Interface
● Event based
● Modify or create Channels
● No access to Dialplan Functions or Apps
● Asynchronous does not block
https://wiki.asterisk.org/wiki/pages/viewpage.action?pageId=4817239

8. What are AMI, AGI and ARI
AGI - Asterisk Gateway Interface
● Execute a script or call a socket
● Only on dialplan operation
● Can execute dialplan applications and functions
● Easy to use
● Synchronous and blocks channel
https://wiki.asterisk.org/wiki/pages/viewpage.action?pageId=32375589

9. AGI != FastAGI

10. What are AMI, AGI and ARI
ARI - Asterisk REST Interface
● Event based
● HTTP socket and REST interface
● Control of low level resources in Asterisk
● Asynchronous, might block
ARI = Dialplan app Stasis
https://wiki.asterisk.org/wiki/pages/viewpage.action?pageId=29395573

11. What are AMI, AGI and ARI
https://wiki.asterisk.org/wiki/pages/viewpage.action?pageId=29395573

12. What are AMI, AGI and ARI
When to use what?
AMI - Channel manipulation during a call
AGI - Extended dialplan Handling
ARI - Write your own dialplan application
https://wiki.asterisk.org/wiki/display/AST/AMI+v2+Specification#AMIv2Specification-ProtocolOverview

13. Goal

14. Goal
Everyone should be able to write PBX features

15. Goal
SIP, Asterisk Dialplan, AGI, AMI, ARI, etc. are complex

16. Goal
Create an abstraction

17. What are we doing with the Asterisk

18. What are we doing with the Asterisk?
Call routing
In call features
Accounting/billing
Announcements
IVR, Conference etc….
Customer API

19. How are we using the Asterisk

20. How are we using the Asterisk?
Lot of Dialplan
Several FastAGI executions
Some AGI Scripts
AMI call manipulation

21. How are we using the Asterisk?
Lot of Dialplan
Several FastAGI executions
Some AGI Scripts
AMI call manipulation
Every feature is distributed allover the place

22. Problems with the current setup

23. Problems with the current Setup
Everything saved in Channel Vars
Several local Dial()
Multiple Calls of FastAGI and AGI and manager Interconnection

24. Problems with the current Setup
Loss of state and variables
Features interfere with each other

25. Problems with the current Setup
Loss of state and variables
Features interfere with each other
Setup has been grown beyond repair

26. Possible solution

27. Possible solution
Respect system boundaries
Stick to standards
Use components for what they are designed for

28. Possible solution
AGI
● Use as testable dialplan generic to any features
ARI
● Control of resources during the call specific to each feature

29. Possible solution
AGI
● Call Setup and Teardown
ARI
● The only instance controlling a feature during the entire call

30. Possible solution
AGI
● Check the feature and call correct Stasis App
● Determine outgoing carrier, write CDR, ...
ARI
● All feature relevant handlings

31. How would it look like

32. How would it look like?

33. How would it look like?

34. How would it look like?
App
dispatcher
ARI App
Out
dispatcher
App
dispatcher
ARI App
SIP SIPlocal

35. How would it look like?
App Dial -> App Stasis

36. How would it look like?
App Dial -> App Stasis
Small-sized Stasis apps

37. How would it look like?
Use ARI Proxy
Move routing logic away from Asterisk

38. How would it look like?
Use ARI Proxy
Move routing logic away from Asterisk
Kafka -> https://github.com/retel-io/ari-proxy
NATS / Rabbit MQ -> https://github.com/CyCoreSystems/ari-proxy

39. How would it look like?

40. How would it look like?
Low level API, ARI High level API

41. How would it look like?
Asterisk
ARI WS
ARI REST
Kafka
Low level
Call
control
High level
Feature
control
Low level API, ARI High level API
ARI Proxy

42. Benefits

43. Benefits
● Less untested dialplan
● Easy to replace features
● No developer interactions with Asterisk Dialplan
● Generic Asterisk dialplan
● Low level ARI API enables any feature
● Decouple telephony feature from Asterisk

44. Benefits
AGI -> control generic Features
ARI -> enables features and isolates from each other

45. Earlier

46. Earlier
Astricon 2018: How ARI-Proxy works
youtube.com/watch?v=vMCyuItMYxE
CommCon 2019: Migrate old to new
youtube.com/watch?v=Y9R0mg9eC9c

47. Questions?
Thanks for listening!
Jöran Vinzens
@vinzens81
linkedin.com/in/jvinzens/