voice

• gateway - bridges calls between VoIP and traditional PSTN networks:
  • analog - traditional phones and faxes
  • digital - digital PBX system
• PSTN = Public Switched Telephone Network
• SIP = Session Initiation Protocol - establishes, modifies and terminates calls
• RTP = Real-Time Transport Protocol - transmits audio and video over the Internet
• SDP = Session Description protocol - describes multimedia sessions
• codecs - (de)compress data to conserve bandwidth while maintaining audio quality
  • G.711 - uncompressed, high quality, high BW usage
  • G.729 - compressed, good quality, low BW usage
  • Opus - versatile, supports both voice and music
• ATA = Analog Telephone Adapter - used to connect traditional analog telephones to the VoIP network
• PBX server = Private Branch Exchange - manages the internal phone system of the business; call routing, voicemail...
• CUCM = Cisco Unified Communications Manager
• BW standard VoIP call - 100 kbps per call
• BW high quality - up to 1 Mbps per call
• SBC = Session Border Controller
• UAC = User Agent Client - initiates SIP requests
• UAS = User Agent Server - responds to SIP requests
• registrar server - registers user location and helps finding the user in the network
• SIP message structure: request/status line, headers, body
• SIP methods:
  • INVITE - initiates a call
  • ACK - confirms the call setup
  • BYE - terminates a call
  • REGISTER - registers a user with a SIP server
  • OPTIONS - queries the capabilities of other endpoints
  • CANCEL - cancels pending requests
• RTP packet structure - header and payload
• RTCP = Real-Time Control Protocol
• CID = Caller ID
• VoIP extension - internal phone number -> short code
• CRM = Customer Relationship Management
• ERP = Enterprise Resource Planning
• UC = Unified Communications - voice + video + messaging
• BLF = Busy Lamp Field - a row of programmable keys that indicate e. g. whether a colleague's phone line is busy or not, usually by the use of a color LED
• DID = Direct Inward Dialing / DDI = Direct Dialing Inward
• IVR = Interactive Voice Response
• polling strategies:
  • prioritized hunt - calls are distributed starting with the first agent in the "users" list if the agent is busy, the call moves to the next available agent this method is ideal for skills-based routing, ensuring the most qualified agents handle calls first
  • ring all - all queue members receive the call simultaneously until someone answers or the ring time limit is reached
  • hunt random start - calls are assigned to a randomly selected agent, ensuring an even distribution among available agents
  • round robin - distributes calls sequentially among logged-in agents, ensuring each agent receives a fair share of calls
  • longest waiting - routes the call to the agent who has been idle the longest
  • least talk time - directs the call to the agent with the least accumulated talk time
  • fewest answered - sends the call to the agent who has handled the fewest calls
  • hunt by threes random - simultaneously rings three randomly selected agents
  • hunt by threes prioritized - calls three agents at a time in the order defined in the "users" list
• queue managers have three options to train agents during live calls:
  • listen - monitor live conversations without either the agent or caller knowing
  • whisper - provide real-time coaching by speaking only to the agent without the caller hearing
  • barge - intervene in the conversation when necessary, allowing the manager to speak directly with both the agent and the caller