Bridging Calls between asterisk instances using ARI

1. Bridging calls using ARI
across Asterisk instances
Jöran Vinzens
@vinzens81

2. Jöran Vinzens
Twitter: @vinzens81 - linkedin.com/in/jvinzens
sipgate GmbH VoIP Carrier Germany/UK
SIP since 2004
MVNO since 2013
https://de.slideshare.net/JranVinzens
Who am I

3. What? Bridge Calls?

4. What? Bridge Calls?
We are about to build the best VoIP platform
Used AMI in the past
Now about to use modern technologies

5. What? Bridge Calls?
Yes, bridge calls!

6. What? Bridge Calls?
Yes, bridge calls!
Like: Pickup, Conferencing...

7. What? Bridge Calls?

8. What? Bridge Calls?
Yes, bridge calls!
Not like: Alice calls Bob

9. What? Bridge Calls?

10. What? Bridge Calls?
Connect call A with call B
Sounds simple...

11. What? Bridge Calls?
Using built in applications from Asterisk, it is simple…
but..

12. What? Bridge Calls?
Using ARI

13. What? Bridge Calls?
Using ARI
High scaled environment

14. What? Bridge Calls?
Using ARI
High scaled environment
Remote controlled Asterisk

15. Why?

16. Why?
Why use ARI?

17. Why?
Scaling

18. Why?
Scaling brings some problems

19. Why?
There are two ways of scaling

20. Why?
1. Bring up an instance for each Customer

21. Why?

22. Why?
Limits size of customer
Single point of failure
Orchestrate instances with lots of customers

23. Why?
2. Spread all calls randomly across all instances

24. Why?

25. Why?
No single point of failure
Mixed hardware types possible
Rolling deployment
No customer size limit

26. Why?
OK, where is the problem?

27. Why?
Knowing calls
Connecting calls

28. Why?
app_queue.so

29. Why?
Call comes in → routing to agent according to its position in the queue

30. Why?
Call comes in → routing to agent according to its position in the queue
Simple, if there is only one Asterisk!

31. Why?

32. Why?
Two calls coming in
One on instance 1
One on instance 2
Which is the first?

33. Why?

34. Why?
“If no application solves your problem, build your own!”
Control two Asterisk at once

35. Why?

36. Why?

37. Why?
ARI Proxy
Kafka
Callcontroller

38. Why?
https://github.com/retel-io
https://youtu.be/vMCyuItMYxE

39. Why?
https://github.com/retel-io
https://youtu.be/vMCyuItMYxE

40. Why?
ARI proxy generates routing key
Use routing key to correlate all call relevant events
Only one callcontroller instance for a call

41. Why?
Problem solved!

42. Why?
Problem solved!
But what about connecting calls?

43. Why?
A conference needs to collect all media streams

44. How?
Calls hitting different instances
Challenge: bring the calls together
Just the knowledge about other calls is not enough

45. Why?

46. Why?

47. Why?
Why no 302?
Carrier and Clients need to handle the 302

48. Why?

49. Why?
Use SIP proxy to pass calls
No need to know all other instances
Provide routing information for proxy

50. How?
Things we need to do

51. How?
Identify a conference call
Check for existing conferences
Create a new one or bridge calls

52. How?
Identify a conference call
Check for existing conferences
Create a new one or bridge calls

53. How?
Identify a conference call
Identify by Phone number / DID
Stored data in global database

54. How?
Identify call as conference call

55. How?
Identify a conference call
Check for existing conferences
Create a new one or bridge calls

56. How?
Check for existing conferences
Store data on startup of conference
Globally read/writeable

57. How?
Check for existing conferences
Conference DID as identifier
Asterisk instance and routing key of first call as data
“4921163550000 -> 1.2.3.4, routing key”

58. How?
Check for existing conferences

59. How?
Identify a conference call
Check for existing conferences
Create a new one or bridge calls

60. How?
Create a new conference
Add calls to conference

61. How?
Create a new conference
Write data into database

62. How?

63. How?
Create a new conference
Create bridge (holding)
Start MOH
Add channel to bridge
Wait for new calls

64. How?
Create a new conference

65. How?
Create a new conference
Add calls to conference

66. How?
Add calls to conference
Get data from existing conference
Create a new channel (and bridge) on the Asterisk instance
Add routing key to the channel as header

67. How?
Add calls to conference

68. How?
Add calls to conference

69. How?
Add calls to conference
Routing key is used for routing

70. How?
Add calls to conference
Add second channel to bridge
Stop MOH
Set bridge to type mixing

71. How?

72. How?
Add calls to conference

73. How?
Add calls to conference

74. How?
Add calls to conference

75. How?
Problems:
Possible race condition
Initial calls on same Asterisk instance

76. How?
Possible race condition
Use of ACID DB
Consistency is important - second call must roll back

77. How?
Problems:
Possible race condition
Initial calls on same Asterisk instance

78. How?
Initial calls on same Asterisk instance
Use of local channel

79. How?
Initial calls on same Asterisk instance

80. How?
Initial calls on same Asterisk instance

81. How?
Easy to orchestrate
Only one instance controls the conference
All other instances handle just a simple call

82. How?

83. How?

84. How?

85. Finally
Added a complex setup
Knowledge of all ongoing calls
Flexibility to connect all types of calls

86. Questions?
I’m ready to answer all your question
Join me at the astricon chat!
Or poke me later via twitter/linkedIn