Pinana : Old proposal for distributed SIP states in Asterisk

DISTRIBUTED CALL STATESMaking Asterisk blinking lamps scale

!V 3 - 2010-07-03

Olle E. Johansson * [email protected] Edvina AB, Sollentuna, Sweden 2008-2009. All rights reserved.

SIPSecurity

© 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


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ASTERISK VERSION

• Trunk ( to be integrated)

• Asterisk 1.4/Edvx

• Other versions depends on sponsor’s needs


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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


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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).


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IDEA

SIP

Presence server

ast01* ast02*

Asterisk 02 subscribes to remote SIP device status.

exten => 1234,hint,sip-dialog:sip:[email protected]

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:[email protected] ; Publish a complete context ; Changes in the context won’t be published publishcontext = internal, edvina.net !!


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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


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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


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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


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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


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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


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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


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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.


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PUBLISH DEVICE STATES

• Create a subdomain for device states in presence server

• Using dialog-info

• Publish to devicename@domain • SIP/[email protected]

• Simple prefix-based filters in sip-presense.conf


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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:[email protected]

• exten => anna, pubhint, sip-dinfo,sips:[email protected]

• exten => brad,pubhint,xmpp,xmpp:[email protected]


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CONFIGURATION OF MAPPING

[contextname] outboundproxy=<peer or domain> defaultdomain=edvina.net urimap=1236474,sip:[email protected] urimap=12922,sips:[email protected]

sip-publish.conf

Pinana : Old proposal for distributed SIP states in Asterisk

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