CME Media Resources - Conference Bridge

There are two types of conferences supported by CME

Ad-hoc Conferences

In ad-hoc conferences, the initiator will use Conf softkey to dial parties and join them into conference (there are other advanced methods to establish conference as well) . Ad-hoc conferences can be completed using software CFB or hardware CFB.

Software CFB

- Software CFB uses router CPU  
- Software resources can provide a max of 3 participants (SIP, SCCP, or PSTN) with G711 codec only. For mixed codecs transcoder should be invoked. In case XCODER isn't available, conference can't be completed.  
- The max number of software ad-hoc simultaneous conferences depends on CME platform.
- Each phone can be part of one conference at a time

For software CFB nothing needs to be configured since its enabled by default and can't be disabled. A workaround to disable it is to enable hardware CFB without configuring DSP resources.

To change some default configuration for software CFB:

Number of Conference Sessions and Gain

As mentioned earlier, the maximum number of conferences is platform dependent. However, this can be limited manually using,

 max-conferences max-conference-number [gain -6 | 0 | 3 | 6]

The gain keyword offers the option to raise the volume of the stream for all call legs (VoIP/Tele).

Note: Although its applied under SCCP CME, its applicable for phone SIP/SCCP phones.

Modify Conference End Call behavior

By default, once the initiator disconnects the call, all conference parties will be disconnected (regardless if they are SCCP/SIP/Tele). This behavior can be changed per phone.

ephone phone-tag
 keep-conference [drop-last] [endcall] [local-only]
voice register pool pool-tag

For SCCP initiators, here are the available options:
  1. no keep-conference: This is the default mode, where the conference is dropped once initiator hangs up or press EndCall softkey. Also, initiator can use Conf softkey to drop the last participant
  2. keep-conference (No keywords used): The initiator can use EndCall softkey to terminate the conference or hang up to disconnect from conference while other two parties are connected. Conf softkey can be used to break the conference but stay connected to both parties while one is on-hold
  1. drop-last: This changes the action of Conf softkey which will disconnect the last party from conference.
  1. Endcall: This changes the action of Endcall softkey which will disconnect the initiator from conference while keeping other parties connected. The same will be the case if initiator hangs up
  1. local-only: When the initiator disconnects, parties will remain connected (using transfer) only if one of them is local to CME

For SIP initiators, those options aren't available. Its either all parties disconnected or leave them joined once the initiator disconnects.

Its very important to know that keep-conference feature requires call transfer to enabled. Once the initiator disconnects, call transfer will be initiated to join the remaining parties together. This isn't a problem in case all phones are part of same CME system since transfer is allowed. However, if one of the parties is remote (e.g. SIP trunk), in this case call transfer (either blind or consult) should be enabled to keep the other parties connected.

Note: During call conference, the display on initiator will be showing last called number. Also, on parties, initiator will be displayed as calling number. On initiator screen, Conference keyword will be displayed in the place of system message. In case the initiator disconnects, the display will be updated to show the on-call parties as calling numbers (assuming keep-conference is enabled).

Note: MOH isn't suppressed from the conference call incase any of the parties places the call on-hold

Hardware CFB

- Once hardware CFB is enabled, software CFB will be disabled.  
- Allow more than 3 participants per conference  
- Does not support the local-consult transfer method (transfer-system local-consult command)  
- In case of multi-codec legs, CFB can do transcoding as well as conferencing (it won't invoke separate XCODER)  
- Hardware CFB isn't supported for SIP phones. SIP phones will still use software CFB with max of 3 participants in case SIP phone is initiator. However, SIP phones can be parties of hardware conference (SCCP phone will be initiator).
- Each phone can be part of one conference at a time  
- For CFB to work, DNs should be configured to act as bridges with conference ad-hoc/meetmefeature enabled. Those DNs can't have other features such as call forward and can't be assigned to ephones.  
- Once conference is triggered, each party will be transferred to one of those conference DNs acting as its bridge. Therefore, the number of conference DNs configured should be enough to accommodate the max number of participants configured combined with max number of conference sessions.  
- Those DNs can't be single lines (conference ad-hoc/meetme command won't be taken and will throw error). They can be either dual or octo lines. E.g. for one conference with 5 parties, we should have 3 dual-line conference DNs or one octo-line conference DN.

ephone-dn  20  octo-line
 number 3020
 description **** HW CFB ***
 conference ad-hoc

SiteC#show call leg active summary
G  L     Elog A/O FAX T Codec       type        Peer Address       IP R:
G17B4  L 372      N   ORG     T33    g711ulaw    TELE        P3002
G17B9  L 374      N   ORG     T24    g729r8      VOIP        P3001    
G17B4  L 377      N   ORG     T21    g711ulaw    TELE        P3020
G17B9  L 378      N   ORG     T21    g729r8      TELE        P3020
G0     L 379      N   ORG     T21    g711ulaw    VOIP        P        
G0     L 37D      N   ORG     T21    g729r8      VOIP        P        
G17C6  L 37E      N   ANS     T17    g711ulaw    TELE        P32143003
G17C6  L 37F      N   ORG     T17    g711ulaw    TELE        P3020
G0     L 380      N   ORG     T17    g711ulaw    VOIP        P        

- Since the parties will be transferred to conference DNs, then CME call transfer should be enabled (especially for external parties to join).  
- Once the conference is established, the display on all parties will show To Conference.  
- If any party disconnect from conference, the audio stream of other remaining parties won't break and will remain connected to CFB. If the number of remaining parties become 2, the CFB will be release and the stream will break to reconnect directly between parties as point-to-point call. Also, the display will be updated with new DNs.  
- The keep-conference feature under ephones/voice pools is ignored. If the  initiator disconnects from conference, other parties will remain connected through CFB as long as the number of participants is more than 2.  
- Also, max-conferences option under telephony-service is ignored. The max number of conferences depends on dspfarm configuration.  
- Similar to software CFB, MOH isn't suppressed from conference  
- Conference initiator should have at least one dual-line or two single-line DNs to be able to start conference.  
- Initiator with octo-line DN will select an idle channel from that DN to establish new call. In case free line isn't available, the conference can't be completed. CME won't select idle channels from other DNs within the same phone similar to single/dual lines behavior.  
- CME admin can assign admin role to any of the ephones within a conference. The conference administrator can:
1. Dial in to any conference directly through the conference number
2. Use the ConfList soft key to list conference parties
3. Remove any party from any conference


- In meet-me conferences, the creator presses MeetMe soft key before dialing the conference number. Other meet-me conference parties only dial the conference number to join the conference.  
- In case software CFB is used, Meet-Me conferences can't be completed.  
- Max number of Meet-Me conference parties is 32 for G711 codec and 16 for G729 codecs

Conference Softkeys

The RmLstC, ConfList, Join, and Select soft keys are not supported for software-based conferencing. Only Conf softkey is supported with software CFB.

- ConfList: Lists all parties in a conference. For meet-me conferences, this soft key is available for the creator only unlike Ad-hoc. Press Update to update the list of parties in the conference  
- Join: Joins an established call to an Ad-hoc conference. You must first press Select to choose each connected call that you want to join in a conference, then press Join to join the selected calls to the conference.  
- RmLstC: Removes the last party added to the conference. This soft key works for the creator only.  
- Select: Selects a call or conference to join to a conference and selects a call to remove from a conference. The creator only can remove other parties by pressing the ConfList soft key, then use the Select and Remove soft keys to remove the appropriate parties.

Configuration Template

voice-card 0
 dsp services dspfarm
voice class custom-cptone CONFERENCE-LEAVE
 dualtone conference
  frequency 1800 3210
  cadence 1000 1000 2000 1000 3000 1000
voice class custom-cptone CONFERENCE-JOIN
 dualtone conference
  frequency 1210 2800
  cadence 3000 1000 2000 1000 1000 1000
sccp local
sccp ccm identifier version 7.0
sccp ccm group
 bind interface
 associate ccm priority
 associate profile register
 switchback method graceful
dspfarm profile conference 
 codec g711ulaw
 codec g711alaw
 codec g729ar8
 codec g729abr8
 codec g729r8
 codec g729br8
 maximum conference-participants
 maximum sessions
 conference-join custom-cptone CONFERENCE-JOIN
 conference-leave custom-cptone CONFERENCE-LEAVE
 associate application SCCP
 conference hardware
!!!!... Define the digits that can be used during conference to mute/unmute. You can mute and unmute your phone using the phone's mute button also. You must unmute the phone in the same way that you muted it, either with the keypad or the mute button.
 sdspfarm conference mute-on mute-off           
 sdspfarm units
 sdspfarm tag
 max-ephones 10
 max-dn 20
 ip source-address port 2000
 transfer-system full-consult
ephone-dn dn-tag [dual-line | octo-line]
 number number [secondary number] [no-reg [both | primary]]
 conference {ad-hoc | meetme}
 no huntstop [channel]
 conference add-mode [creator]           !!!... Enable adding parties to conference. By default both creator and participants can add parties to conference.
 conference drop-mode [creator | local]           !!!... Default is conference never drops. You can tune it to drop conference when creator drops or when the last local participants drops.
 conference admin           !!!... Configures the ephone as the conference administrator
 softkeys connected {[Acct] [ConfList] [Confrn] [Endcall] [Flash] [HLog] [Hold] [Join][LiveRcd] [Park] [RmLstC] [Select] [TrnsfVM] [Trnsfer]}
 softkeys hold {[Join] [Newcall] [Resume] [Select]}
 softkeys idle {[Cfwdall] [ConfList] [Dnd] [Gpickup] [HLog] [Join] [Login] [Newcall] [Pickup][Redial] [RmLstC]}
 softkeys seized {[CallBack] [Cfwdall] [Endcall] [Gpickup] [HLog] [MeetMe] [Pickup][Redial]}
 conference add-mode [creator]
 conference drop-mode [creator | local]
 conference admin


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