Some main parameters should be identified during design phase to understand the required size of implementation
CUC has three terminologies for codecs:
- Line or Advertise Code (the codec negotiated with caller endpoint for RTP stream between caller and CUC voicemail port)
- System Codec (this is used by CUC system (CUC script). CUC system can realize one codec ONLY which is PCM Linear Codec)
- Recording Codec (This is the codec used for recording the received voice mail messages).
Therefore incoming call to CUC will be transcoded from line codec to system codec (PCM Linear), then from system codec to recording as per below diagram. This transcoding is done natively by CUC.
Note in the figure the list of supported codecs for both line and recording.
- The type of recording codec used will impact the size of voice mail store (low bitrate codecs will generate less size and less clarity)
- The type of advertise codec will impact the performance of CUC and number of voicemail ports supported (more complex codecs [low bitrate] less voicemail ports)
- When configuring advertising codecs in CUC, they can be added in order of preference
- For SCCP integration between CUCM and CUC, the order of preference isn’t important because CUCM will select the codec based on voicemail port location and calling device location
- For SIP integration, the order of codec preference is considered
- Makesure that the selected codec is supported by voicemail client (player)
As will see later, CUC can receive voicemail messages stored in another VoiceMail System and send voicemail messages using VPIM protocol.
Here are some codec considerations for voicemail messages exchanged between two messaging systems (between CUC-to-CUC, CUC-to-Unity, CUC-to-ThridParty).
Note: Here we are talking about recording codec since those messages are already stored either in CUC or the other system
• For inbound messages, Connection can do one of the following:
- Convert voice messages to any audio format that Connection supports.
- Not convert the audio format of the voice message, keeping the voice message in its original audio format.
• For outbound voice messages, Connection can do one of the following:
- Convert voice messages to the G.726 audio format.
- Not convert the audio format of the voice message, keeping the voice message in its original audio format
Voice Messaging Ports
Voicemail ports supply the following functions to Cisco Unity Connection:
- Answer calls for incoming callers
- Recording messages
- Retrieving messages
- Message notification (Envelop logo on phone LCD which utilized one port)
- Telephony Record and Playback (TRaP)
- Message waiting indicator (MWI)
- Users retrieving messages using IP Phone will use one voice port. However, users using IMAP client won’t use ports
- Users retrieving messages using Cisco Message Inbox or ViewMail Plugin of MS Outlook can hear their messages using PC Speaker and Microphone (in this case no ports are required). In case the client directed the message to hear through IP Phone (TRaP feature), one port will be utilized.
- When voice message is received, CUC sends specific digits to users phone to turn MWI light ON. When the last message is retrieved, CUC sends another specific digits to users phone to turn MWI light OFF.
Storage Capacity for Voice Messages
For CUC systems that are configured to store voicemails only, the storage size is calculated based on the total number of voice storage minutes.
For CUC systems that are configured to store faxes and email replies to voice messages in addition to voice messages, the storage is calculated based on bytes. The voice messages length in minutes is converted into equivalent bytes and added that to the current mailbox limits.