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There are many significant architectural changes in Asterisk 12. It is recommended that you not only read through this document for important changes that affect an upgrade, but that you also read through the CHANGES document and the information about what is New in 12 to better understand the new options available to you.

Upgrade Overview

Of particular note, the following systems in Asterisk underwent significant changes. Documentation for the changes and a specification for their behavior in Asterisk 12 are available in the Asterisk 12 Documentation section on this wiki.

  • AMI: Many events were changed, and the semantics of channels and bridges were defined. In particular, how channels and bridges behave under transfer scenarios and situations involving multiple parties has changed significantly. See the AMI v2 Specification for more information.
  • CDRs: CDR logic was extracted from the many locations it existed in across Asterisk and implemented as a consumer of Stasis message bus events. As a result, consistency of records has improved significantly and the behavior of CDRs in transfer scenarios has been defined in the CDR specification. However, significant behavioral changes in CDRs resulted from the transition. The most significant change is the addition of CDR entries when a channel who is the Party A in a CDR leaves a bridge. See the Asterisk 12 CDR Specification for more information.
  • CEL: Much like CDRs, CEL was removed from the many locations it existed in across Asterisk and implemented as a consumer of Stasis message bus events. It now closely follows the Bridging API model of channels and bridges, and has a much closer consistency of conveyed events as AMI. For the changes in events, see the Asterisk 12 CEL Specification.

Upgrade Changes

Build System:

  • Removed the CHANNEL_TRACE development mode build option. Certain aspects of the CHANNEL_TRACE build option were incompatible with the new bridging architecture.
  • Asterisk now depends on libjansson, libuuid and optionally (but recommended) libxslt and uriparser.
  • The new SIP stack and channel driver uses a particular version of PJSIP. Please see PJSIP-pjproject for more information on installing and configuring PJSIP for use with Asterisk 12.

AgentLogin, AgentRequest, and chan_agent:

  • Along with AgentRequest, this application has been modified to be a replacement for chan_agent. The chan_agent module and the Agent channel driver have been removed from Asterisk, as the concept of a channel driver proxying in front of another channel driver was incompatible with the new architecture (and has had numerous problems through past versions of Asterisk). The act of a channel calling the AgentLogin application places the channel into a pool of agents that can be requested by the AgentRequest application. Note that this application, as well as all other agent related functionality, is now provided by the app_agent_pool module.
  • This application no longer performs agent authentication. If authentication is desired, the dialplan needs to perform this function using the Authenticate or VMAuthenticate application or through an AGI script before running AgentLogin.
  •  The agents.conf schema has changed. Rather than specifying agents on a single line in comma delineated fashion, each agent is defined in a separate context. This allows agents to use the power of context templates in their definition.
  •  A number of parameters from agents.conf have been removed. This includes maxloginretries, autologoffunavail, updatecdr, goodbye, group, recordformaturlprefix, and savecallsin. These options were obsoleted by the move from a channel driver model to the bridging/application model provided by app_agent_pool.
  •  The AGENTUPDATECDR channel variable has also been removed, for the same reason as the updatecdr option.
  •  The endcall and enddtmf configuration options are removed. Use the dialplan function CHANNEL(dtmf-features) to set DTMF features on the agent channel before calling AgentLogin.


  •  This application has been removed. It was a holdover from when AgentCallbackLogin was removed.


  • It is no longer possible to bypass updating the CDR when answering a channel. CDRs are based on the channel state and will be updated when the channel is Answered.


  • The channel variable CPLAYBACKSTATUS may now return the value REMOTESTOPPED when playback is stopped by an external entity.


  • This application now has a dependency on the app_cdr module. It uses this module to hide the CDR created prior to execution of the DISA application.


  • The output of DumpChan no longer includes the DirectBridge or IndirectBridge fields. Instead, if a channel is in a bridge, it includes a BridgeID field containing the unique ID of the bridge that the channel happens to be in.


  • Nearly every parameter in ForkCDR has been updated and changed to reflect the changes in CDRs. Please see the documentation for the ForkCDR application, as well as the CDR specification.


  • The NoCDR application has been deprecated. Please use the CDR_PROP function to disable CDRs on a channel.


  • The app_parkandannounce module has been removed. The application ParkAndAnnounce is now provided by the res_parking module. See the Parking changes for more information.


  • The w and a options have been removed. Dispatching CDRs to registered backends occurs on an as-needed basis in order to preserve linkedid propagation and other needed behavior.
  • The e option is deprecated. Please use the CDR_PROP function to enable CDRs on a channel that they were previously disabled on.
  • The ResetCDR application is no longer a part of core Asterisk, and instead is now delivered as part of app_cdr.


  • Queue strategy rrmemory now has a predictable order similar to strategy rrordered. Members will be called in the order that they are added to the queue.
  • Removed the queues.conf check_state_unknown option. It is no longer necessary.
  • It is now possible to play the Queue prompts to the first user waiting in a call queue. Note that this may impact the ability for agents to talk with users, as a prompt may still be playing when an agent connects to the user. This ability is disabled by default but can be enabled on an individual queue using the announce-to-first-user option.
  • The configuration options eventwhencalled and eventmemberstatus have been removed. As a result, the AMI events QueueMemberStatus, AgentCalledAgentConnect, AgentComplete, AgentDump, and AgentRingNoAnswer will always be sent. The Variable fields will also no longer exist on the Agent* events. These events can be filtered out from a connected AMI client using the eventfilter setting in manager.conf.
  • The queue log now differentiates between blind and attended transfers. A blind transfer will result in a BLINDTRANSFER message with the destination context and extension. An attended transfer will result in an ATTENDEDTRANSFER message. This message will indicate the method by which the attended transfer was completed: BRIDGE for a bridge merge, APP for running an application on a bridge or channel, or LINK for linking two bridges together with local channels. The queue log will also now detect externally initiated blind and attended transfers and record the transfer status accordingly.
  • When performing queue pause/unpause on an interface without specifying an individual queue, the PAUSEALL/ UNPAUSEALL event will only be logged if at least one member of any queue exists for that interface.



  • The voicemail.conf configuration file now has an alias configuration parameter for use with the Directory application. The voicemail realtime database table schema has also been updated with an 'alias' column. Systems using voicemail with realtime should update their schemas accordingly.
  • Mailboxes defined by app_voicemail MUST be referenced by the rest of the system as [email protected].  The rest of the system cannot add @default to mailbox identifiers for app_voicemail that do not specify a context any longer.  It is a mailbox identifier format that should only be interpreted by app_voicemail.

Channel Drivers:

  • When a channel driver is configured to enable jiterbuffers, they are now applied unconditionally when a channel joins a bridge. If a jitterbuffer is already set for that channel when it enters, such as by the JITTERBUFFER function, then the existing jitterbuffer will be used and the one set by the channel driver will not be applied.


  •  chan_bridge is removed and its functionality is incorporated into ConfBridge itself.


  • Analog port dialing and deferred DTMF dialing for PRI now distinguishes between w and W. The w pauses dialing for half a second. The W pauses dialing for one second.
  • The default for inband_on_proceeding has changed to no.
  • The CLI command dahdi destroy channel is now dahdi destroy channelsA range of channels can be specified to be destroyed. Note that this command should only be used if you understand the risks it entails.
  • The script specified by the chan_dahdi.conf mwimonitornotify option now gets the exact configured mailbox name.  For app_voicemail mailboxes this is [email protected].
  • Added mwi_vm_boxes that also must be configured for ISDN MWI to be enabled.


  • The /b option has been removed.
  • chan_local moved into the system core and is no longer a loadable module.


  • The callevents parameter has been removed. Hold AMI events are now raised in the core, and can be filtered out using the eventfilter parameter in manager.conf.
  • Dynamic realtime tables for SIP Users can now include a path field. This will store the path information for that peer when it registers. Realtime tables can also use the supportpath field to enable Path header support.
  •  LDAP realtime configurations for SIP Users now have the AstAccountPathSupport objectIdentifier. This maps to the supportpath option in sip.conf.


  •  Masquerades as an operation inside Asterisk have been effectively hidden by the migration to the Bridging API. As such, many 'quirks' of Asterisk no longer occur. This includes renaming of channels, "<ZOMBIE>" channels, dropping of frame/audio hooks, and other internal implementation details that users had to deal with. This fundamental change has large implications throughout the changes documented for this version. For more information about the new core architecture of Asterisk, please see the Asterisk wiki.
  • All bridging in Asterisk is now performed using the Bridging API, which is the same bridging core that powers the ConfBridge application. As a result, significant changes have been made in all areas of Asterisk that are affected by bridging. Those changes are noted in the appropriate areas.

 AMI (Asterisk Manager Interface):

  • The Version has been increased to 2.0. For a full listing of the semantics changes in AMI, see the AMI v2 Specification.
  • The details of what happens to a channel when a masquerade happens (transfers, parking, etc) have changed. Channels no longer swap Uniqueid's as a result of the masquerade. In general, AMI clients will never actually "see" a masquerade, as the operation has been effectively hidden from external systems.
  • Major changes were made to both the syntax as well as the semantics of the AMI protocol. In particular, AMI events have been substantially modified and improved in this version of Asterisk. The major event changes are listed below:
  • The MCID AMI event now publishes a channel snapshot when available and its non-channel-snapshot parameters now use either the MCallerID or MConnectedID prefixes with Subaddr*, Name*, and Num* suffixes instead of CallerID and ConnectedID to avoid confusion with similarly named parameters in the channel snapshot.
  •  The Channel key used in the AlarmClear, Alarm, and DNDState has been renamed DAHDIChannel since it does not convey an Asterisk channel name.
  •  All AMI events now contain a SystemName field, if available.
  •  Local channel information in events is now prefixed with LocalOne and LocalTwo. This replaces the suffix of '1' and '2' for the two halves of the Local channel. This affects the LocalBridge, LocalOptimizationBeginand LocalOptimizationEnd events.
  •  The RTCPSent/RTCPReceived events have been significantly modified from previous versions. They now report all SR/RR packets sent/received, and have been restructured to better reflect the data sent in a SR/RR. In particular, the event structure now supports multiple report blocks.
  •  The deprecated use of | (pipe) as a separator in the channelvars setting in manager.conf has been removed.
  •  The SIP SIPqualifypeer action now sends a response indicating it will qualify a peer once a peer has been found to qualify. Once the qualify has been completed it will now issue a SIPqualifypeerdone event.
  •  The AMI event Newexten field Extension is deprecated, and may be removed in a future release. Please use the common Exten field instead.
  •  The AMI events ParkedCall, ParkedCallTimeOut, ParkedCallGiveUp, and UnParkedCall have changed significantly in the new res_parking module.
    • The Channel and From headers are gone. For the channel that was parked or is coming out of parking, a Parkee channel snapshot is issued and it has a number of fields associated with it. The old Channel header relayed the same data as the new ParkeeChannel header.
    • The From field was ambiguous and changed meaning depending on the event. For most of these, it was the name of the channel that parked the call (the Parker). There is no longer a header that provides this channel name, however the ParkerDialString will contain a dialstring to redial the device that parked the call.
    • On UnParkedCall events, the From header would instead represent the channel responsible for retrieving the parkee. It receives a channel snapshot labeled Retriever. The from field is is replaced with RetrieverChannel.
    • Lastly, the Exten field has been replaced with ParkingSpace.
  • The AMI event Parkinglot (response to Parkinglots command) in a similar fashion has changed the field names StartExten and StopExten to StartSpace and StopSpace respectively.
  • The AMI Status response event to the AMI Status action replaces the BridgedChannel and BridgedUniqueid headers with the BridgeID header to indicate what bridge the channel is currently in.

 CDR (Call Detail Records)

  • Significant changes have been made to the behavior of CDRs. The CDR engine was effectively rewritten and built on the Stasis message bus. For a full definition of CDR behavior in Asterisk 12, please read the Asterisk 12 CDR Specification. 
  • CDRs will now be created between all participants in a bridge. For each pair of channels in a bridge, a CDR is created to represent the path of communication between those two endpoints. This lets an end user choose who to bill for what during bridge operations with multiple parties.
  • The duration, billsec, start, answer, and end times now reflect the times associated with the current CDR for the channel, as opposed to a cumulative measurement of all CDRs for that channel.
  •  CDR backends can no longer be unloaded while billing data is in flight. This helps to prevent loss of billing data during restarts and shutdowns.     


  • The Uniqueid field for a channel is now a stable identifier, and will not change due to transfers, parking, etc.
  • CEL has undergone significant rework in Asterisk 12, and is now built on the Stasis message bus. Please see the Asterisk 12 CEL Specification for more detailed information. A summary of the affected events is below:
    • BRIDGE_START, BRIDGE_END, BRIDGE_UPDATE, 3WAY_START, 3WAY_END, CONF_ENTERCONF_EXIT, CONF_START, and CONF_END events have all been removed. These events have been replaced by BRIDGE_ENTER/ BRIDGE_EXIT.
    • BLINDTRANSFER/ ATTENDEDTRANSFER events now report the peer as NULL and additional information in the extra string field.


  • All channel and global variable names are evaluated in a case-sensitive manner. In previous versions of Asterisk, variables created and evaluated in the dialplan were evaluated case-insensitively, but built-in variables and variable evaluation done internally within Asterisk was done case-sensitively.
  • Asterisk has always had code to ignore dash '-' characters that are not part of a character set in the dialplan extensions. The code now consistently ignores these characters when matching dialplan extensions. 
  • BRIDGE_FEATURES channel variable is now case sensitive for feature letter codes. Uppercase variants apply them to the calling party while lowercase variants apply them to the called party.

 Dialplan Functions:

  • Certain dialplan functions have been marked as 'dangerous', and may only be executed from the dialplan. Execution from extenal sources (AMI's GetVar and SetVar actions; etc.) may be inhibited by setting live_dangerously in the [options] section of asterisk.conf to no. SHELL(), channel locking, andirect file read/write functions are marked as dangerous. DB_DELETE() and REALTIME_DESTROY() are marked as dangerous for reads, but can now safely accept writes (which ignore the provided value).


  • The features.conf [applicationmap] <FeatureName> ActivatedBy option is no longer honored. The feature is always activated by the channel that has DYNAMIC_FEATURES defined on it when it enters the bridge. Use predial to set different values of DYNAMIC_FEATURES on the channels
  • Executing a dynamic feature on the bridge peer in a multi-party bridge will execute it on all peers of the activating channel.
  • There is no longer an explicit features reload CLI command. Features can still be reloaded using module reload features.
  • It is no longer necessary (or possible) to define the ATXFER_NULL_TECH in features.c for atxferdropcall=no to work properly. This option now just works.


  • Parking has been extracted from the Asterisk core as a loadable module, res_parking.
  • Configuration is found in res_parking.conf. It is no longer supported in features.conf
  • The arguments for the Park, ParkedCall, and ParkAndAnnounce applications have been modified significantly. See the application documents for specific details.
  • Numerous changes to Parking related applications, AMI and CLI commands and internal inter-workings have been made. Please read the CHANGES file or the New in 12 page for the detailed list.

Security Events Framework:

  • Security Event timestamps now use ISO 8601 formatted date/time instead of the "seconds-microseconds" format that it was using previously.


  • The password option has been disabled, as the AgentLogin application no longer provides authentication.


  • Due to changes in the Asterisk core, this function is no longer needed to preserve a MixMonitor on a channel during transfer operations and dialplan execution. It is effectively obsolete.

CDR: (function)

  • The amaflags and accountcode attributes for the CDR function are deprecated. Use the CHANNEL function instead to access these attributes.
  • The l option has been removed. When reading a CDR attribute, the most recent record is always used. When writing a CDR attribute, all non-finalized CDRs are updated.
  • The r option has been removed, for the same reason as the l option.
  • The s option has been removed, as LOCKED semantics no longer exist in the CDR engine.


  • Mailboxes defined by app_voicemail MUST be referenced by the rest of the system as [email protected].  The rest of the system cannot add @default to mailbox identifiers for app_voicemail that do not specify a context any longer.  It is a mailbox identifier format that should only be interpreted by app_voicemail.


  • ICE/STUN/TURN support in res_rtp_asterisk has been made optional. To enable them, an Asterisk-specific version of PJSIP needs to be installed. Tarballs are available from


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