An old proposal on how to create distributed states in Asterisk. This was never completed.

1. DISTRIBUTED CALL STATES
Making Asterisk blinking lamps scale
!
V 3 - 2010-07-03
Olle E. Johansson * oej@edvina.net
Copyright Edvina AB, Sollentuna, Sweden 2008-2009.All rights reserved.
SIP
Security

2. © Copyright Edvina AB, Sollentuna, Sweden July 2010.All rights reserved.
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REQUIREMENTS
• Ability to share device states between Asterisk servers
• Ability to subscribe to status of devices in local Asterisk server
as well as remote (as long as they exist in the dial plan)
• Ability to get remote device status in dialplan, like local device
states

3. © Copyright Edvina AB, Sollentuna, Sweden July 2010.All rights reserved.
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ASTERISK VERSION
• Trunk ( to be integrated)
• Asterisk 1.4/Edvx
• Other versions depends on sponsor’s needs

4. © Copyright Edvina AB, Sollentuna, Sweden July 2010.All rights reserved.
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CALL STATES IN SIP
• SIP uses Subscribe/Notify with
the Dialog-info event package
to distribute call states
• A user agent updates the
presence server with
PUBLISH
SUBSCRIBE
Send me updates
NOTIFY
Here’s a requested update
PUBLISH
Here’s my changed status

5. © Copyright Edvina AB, Sollentuna, Sweden July 2010.All rights reserved.
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ASTERISK CURRENT
SUPPORT
• Asterisk 1.4 has support for a variety of event packages for subscriptions,
including dialog-info
• Asterisk 1.6 added remote subscriptions, where Asterisk subscribes for mailbox
notifications (only)
• Asterisk trunk has limited support for PUBLISH for other event types (call
completion/camp-on).

6. © Copyright Edvina AB, Sollentuna, Sweden July 2010.All rights reserved.
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IDEA
SIP
Presence server
ast01
* ast02
*
Asterisk 02 subscribes to remote
SIP device status.
exten => 1234,hint,sip-dialog:sip:oej@ast01.edvina.net
Asterisk 01 publishes device
status updates to presence server.
[general]
presenceserver=pres.edvina.net
presencedomain=edvina.net
!
[presence]
; Publish a single extension
publish = 1234,sip:1234@edvina.net
; Publish a complete context
; Changes in the context won’t be published
publishcontext = internal, edvina.net
!
!

7. © Copyright Edvina AB, Sollentuna, Sweden July 2010.All rights reserved.
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QUEUES
SIP
Presence server
ast01
* ast02
*
Asterisk 02 subscribes to remote
SIP device status.
Asterisk 01 publishes device
status updates to presence server.
If you want Mary to join the support queue as a full member,
you need to add remote device state
!
exten => mary,hint,remote-sip-blah-blah
exten => mary,1,dial(sip/ast02/mary)
!
!
Arne
bertil
Cecilia
Mary
John
Piggy
Queue:
support

8. © Copyright Edvina AB, Sollentuna, Sweden July 2010.All rights reserved.
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NEW QUEUE
ARCHITECTURE?
ast01
* Queue:
support
ast02
*
ast03
*
One server handles queues,
the other servers handles all the agents.
SIP Presence server

9. © Copyright Edvina AB, Sollentuna, Sweden July 2010.All rights reserved.
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OFFLOADING ASTERISK
ast01
*
ast03
*
Asterisk publishes call states to presense
server, Phones subscribe to presense server directly
instead of Asterisk.
SIP Presence server

10. © Copyright Edvina AB, Sollentuna, Sweden July 2010.All rights reserved.
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BENEFITS
• Using a SIP presence server scales
• Other devices can subscribe directly to status with the
presence server
• We can add some extra data - Asterisk-specific - to the
presence items
• It’s standardized

11. © Copyright Edvina AB, Sollentuna, Sweden July 2010.All rights reserved.
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POTENTIAL ISSUES
• Using a proprietary distributed event system might make it
easier to add Asterisk functionality and support legacy systems,
like flash operator panel

12. © Copyright Edvina AB, Sollentuna, Sweden July 2010.All rights reserved.
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TO BE TESTED
• Can we potentially create a dialplan that can handle remote
call pickup?
• Asterisk supports invite with replaces today. Can we force such an action in
the dialplan and have Asterisk pickup a remote SIP call?
• Yes, provided we send the Asterisk channel ID as call-id
• How would this work with manager events/actions?
• We need to spend more time on scenarious here
• Manager support considered out of scope for this first project

13. © Copyright Edvina AB, Sollentuna, Sweden July 2010.All rights reserved.
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REALTIME SUPPORT.
• If a new device activates, based on realtime database, will we have to know that
and publish the state?
• Can be done for SIP devices in the SIP channel I think
• Using regcontext= we can hook into that part and publish the state
• We need to check how the server aggregates states from different servers
• If a phone reboots, it may register on server A and still have registration on
server B.When the registration expires, the state changes - AFTER the other
server has said that everything is fine... Food for thought.

14. © Copyright Edvina AB, Sollentuna, Sweden July 2010.All rights reserved.
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PUBLISH DEVICE STATES
• Create a subdomain for device states in presence server
• Using dialog-info
• Publish to devicename@domain
• SIP/323-3xyy@devicestates.mydomain.org
• Simple prefix-based filters in sip-presense.conf

15. © Copyright Edvina AB, Sollentuna, Sweden July 2010.All rights reserved.
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PUBLISHING EXT STATES
• We need to map exten@context to a SIP uri
• Per extension
• Default mapping per context - map to SIP domain
• Realtime support a requirement
• Maybe add a ”pubhint” in dialplan for XMPP and SIP
• exten => olle,pubhint,sip-pidf,sip:oej@edvina.net
• exten => anna, pubhint, sip-dinfo,sips:anna@pinapalmera.org
• exten => brad,pubhint,xmpp,xmpp:marquis42@deepspace9.trek

16. © Copyright Edvina AB, Sollentuna, Sweden July 2010.All rights reserved.
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CONFIGURATION OF
MAPPING
[contextname]
outboundproxy=<peer or domain>
defaultdomain=edvina.net
urimap=1236474,sip:ross@mydomain.com
urimap=12922,sips:lars@otherdomain.se
sip-publish.conf