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190 lines
8.2 KiB
Plaintext
190 lines
8.2 KiB
Plaintext
================
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Advice of Charge
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================
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Written by: David Vossel
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Initial version: 04-19-2010
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Email: dvossel@digium.com
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This document is designed to give an overview of how to configure and
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generate Advice of Charge along with a detailed explanation of how each
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option works.
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--------------------------------------
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| READ THIS FIRST |
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--------------------------------------
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PLEASE REPORT ANY ISSUES ENCOUNTERED WHILE USING AOC. This feature
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has had very little community feedback so far. If you are using this
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feature please share with us any problems you are having and any
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improvements that could make this feature more useful. Thank you!
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--------------------------------------
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| Terminology |
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--------------------------------------
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AOC: Advice of Charge
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AOC-S: Advice of Charge message sent at the beginning of a call during
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call setup. This message contains a list of rates associated with the
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call.
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AOC-D: Advice of Charge message sent during the call. This message
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is typically used to update the endpoint with the current call charge.
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AOC-E: Advice of Charge message sent at the end of a call. This
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message is used to indicate to the endpoint the final call charge.
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AMI: Asterisk Manager Interface. This interface is used to generate
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AOC messages and listen for AOC events.
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--------------------------------------
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| AOC in chan_dahdi |
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--------------------------------------
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----- LibPRI Support:
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ETSI, or euroisdn, is the only switchtype that LibPRI currently supports
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for AOC.
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----- Enable AOC Pass-through in chan_dahdi
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To enable AOC pass-through between the ISDN and Asterisk use the
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'aoc_enable' config option. This option allows for any combination
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of AOC-S, AOC-D, and AOC-E to be enabled or disabled.
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For example:
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aoc_enable=s,d,e ; enables pass-through of AOC-S, AOC-D, and AOC-E
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aoc_enable=s,d ; enables pass-through of AOC-S and AOC-D. Rejects
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; AOC-E and AOC-E request messages
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Since AOC messages are often transported on facility messages, the
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'facilityenable' option must be enabled as well to fully support AOC
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pass-through.
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----- Handling AOC-E in chan_dahdi
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Whenever a dahdi channel receives an AOC-E message from Asterisk, it
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stores that message to deliver it at the appropriate time during call
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termination. This means that if two AOC-E messages are received on the
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same call, the last one will override the first one and only one AOC-E
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message will be sent during call termination.
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There are some tricky situations involving the final AOC-E message. During
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a bridged call, if the endpoint receiving the AOC messages terminates
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the call before the endpoint delivering the AOC does, the final AOC-E
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message sent by the sending side during termination will never make it to
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the receiving end because Asterisk will have already torn down that channel.
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This is where the chan_dahdi.conf 'aoce_delayhangup' option comes into play.
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By enabling 'aoce_delayhangup', anytime a hangup is initiated by the
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ISDN side of an Asterisk channel, instead of hanging up the channel,
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the channel sends a unique internal AOC-E termination request to its bridge
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channel. This indicates it is about to hangup and wishes to receive the
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final AOC-E message from the bridged channel before completely tearing
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down. If the bridged channel knows what to do with this AOC-E termination
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request, it will do whatever is necessary to indicate to its endpoint that
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the call is being terminated without actually hanging up the Asterisk channel.
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This allows the final AOC-E message to come in and be sent across the bridge
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while both channels are still up. If the channel delaying its hangup for
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the final AOC-E message times out, the call will be torn down just as it
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normally would. In chan_dahdi the timeout period is 1/2 the T305 timer
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which by default is 15 seconds.
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'aoce_delayhangup' currently only works when both bridged channels are
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dahdi_channels. If a SIP channel receives an AOC-E termination request, it
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just responds by immediately hanging up the channel. Using this option when
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bridged to any channel technology besides SIP or DAHDI will result in the
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15 second timeout period before tearing down the call completely.
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----- Requesting AOC services
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AOC can be requested on a call by call basis using the DAHDI dialstring
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option, A(). The A() option takes in 's', 'd', and 'e' parameters which
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represent the three types of AOC messages, AOC-S, AOC-D, and AOC-E. By using
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this option Asterisk will indicate to the endpoint during call setup that it
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wishes to receive the specified forms of AOC during the call.
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Example Usage in extensions.conf
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exten => 1111,1,Dial(DAHDI/g1/1112/A(s,d,e) ; requests AOC-S, AOC-D, and AOC-E on
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; call setup
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exten => 1111,1,Dial(DAHDI/g1/1112/A(d,e) ; requests only AOC-D, and AOC-E on
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; call setup
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--------------------------------------
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| AOC in chan_sip |
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--------------------------------------
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Asterisk supports a very basic way of sending AOC on a SIP channel to Snom
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phones using an AOC specification designed by Snom. This support is limited
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to the sending of AOC-D and AOC-E pass-through messages. No support for
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AOC-E on call termination is present, so if the Snom endpoint receiving the
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AOC messages from Asterisk terminates the call, the channel will be torn
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down before the phone can receive the final AOC-E message.
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To enable passthrough of AOC messages via the snom specification, use
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the 'snom_aoc_enabled' option in sip.conf.
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--------------------------------------
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| Generate AOC Messages via AMI |
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--------------------------------------
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Asterisk supports a way to generate AOC messages on a channel via
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the AMI action AOCMessage. At the moment the AOCMessage action is limited
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to AOC-D and AOC-E message generation. There are some limitations
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involved with delivering the final AOC-E message as well. The AOCMessage
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action has its own detailed parameter documentation so this discussion will
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focus on higher level use. When generating AOC messages on a Dahdi channel
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first make sure the appropriate chan_dahdi.conf options are enabled. Without
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enabling 'aoc_enable' correctly for pass-through the AOC messages will never
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make it out the pri. The same goes with SIP, the 'snom_aoc_enabled' option
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must be configured before messages can successfully be set to the endpoint.
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----- AOC-D Message Generation
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AOC-D message generation can happen anytime throughout the call. This
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message type is very straight forward.
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Example: AOCMessage action generating AOC-D currency message with Success
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response.
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Action: AOCMessage
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Channel: DAHDI/i1/1111-1
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MsgType: d
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ChargeType: Currency
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CurrencyAmount: 16
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CurrencyName: USD
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CurrencyMultiplier: OneThousandth
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AOCBillingId: Normal
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ActionID: 1234
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Response: Success
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ActionID: 1234
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Message: AOC Message successfully queued on channel
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----- AOC-E Message Generation
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AOC-E messages are sent during call termination and represent the final charge
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total for the call. Since Asterisk call termination results in the channel
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being destroyed, it is currently not possible for the AOCMessage AMI action to
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be used to send the final AOC-E message on call hangup. There is however a
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work around for this issue that can be used for Dahdi channels. By default
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chan_dahdi saves any AOC-E message it receives from Asterisk during a call and
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waits to deliver that message during call termination. If multiple AOC-E messages
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are received from Asterisk on the same Dahdi channel, only the last message received
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is stored for delivery. This means that each new AOC-E message received on the
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channel overrides the previous one. Knowing this the final AOC-E message can be
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continually updated on a Dahdi channel until call termination occurs allowing
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the last update to be sent on hangup. This method is only as accurate as the
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intervals in which it is updated, but allows some form of AOC-E to be generated.
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Example: AOCMessage action generating AOC-E unit message with Success response.
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Action: AOCMessage
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Channel: DAHDI/i1/1111-1
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MsgType: e
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ChargeType: Unit
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UnitAmount(0): 111
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UnitType(0): 6
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UnitAmount(1): 222
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UnitType(1): 5
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UnitAmount(2): 333
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UnitType(3): 4
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UnitAmount(4): 444
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AOCBillingId: Normal
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ActionID: 1234
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Response: Success
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ActionID: 1234
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Message: AOC Message successfully queued on channel
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