VoIP Phones

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• a VoIP/SIP endpoint can be implemented as:
  • software running on a computer or smartphone
  • or as a dedicated hardware handset
• VoIP phones use VLAN tagging to ensure that the SIP control and RTP media protocols can be segregated from normal data traffic
• In a typical voice VLAN configuration,
  • LAN port on the handset is connected to the wall port
  • PC is connected to the PC port on the handset
  • the two devices share the same physical link
    • but data traffic is distinguished from voice traffic by configuring separate VLAN IDs
• handsets can use Power over Ethernet (PoE) to avoid the need for separate power cable or batteries
• handsets can be wireless over 802.11 Wi-Fi
• connection security for VoIP
  • works similar to HTTPS
  • to initiate the call, the secure version of SIP (SIPS) uses digital certificates to authenticate the endpoints and establish a TLS tunnel
  • secure connection is used to generate a master key to use with the secure versions of the transport and control protocols
• installing a new handset:
  • test that the connection works and that the link provides sufficient call quality
  • most service providers have test numbers to verify basic connectivity
    • can perform an echo test call, which replays a message you record so that you can confirm voice quality