• SonicOS 7.0 VoIP
• Overview
  • About SonicOS
  • SonicOS Workflow
  • How to Use the SonicOS Administration Guides
  • Guide Conventions
• VoIP
  • VoIP Security
    • Security Appliance Requirements for VoIP
  • VoIP Protocols
    • H.323
    • SIP
  • SonicWall’s VoIP Capabilities
    • VoIP Security
    • VoIP Network
    • VoIP Network Interoperability
    • Supported Interfaces
    • Supported VoIP Protocols
      • H.323
      • SIP
      • SonicWall VoIP Vendor Interoperability
      • CODECs
      • VoIP Protocols on which SonicOS Does Not Perform Deep Packet Inspection
    • BWM and QoS
      • Quality of Service
    • How SonicOS Handles VoIP Calls
      • Incoming Calls
      • Local Calls
  • Settings
    • Configuring VoIP Settings
      • General Settings
      • SIP Settings
        • Enabling SIP
      • H.323 Settings
        • Configuring Bandwidth on the WAN Interface
        • Configuring VoIP Access Rules
    • Configuring VoIP Logging
• Call Status
• SonicWall Support
  • About This Document

Incoming Calls

Incoming Call Sequence of Events shows the sequence of events that occurs during an incoming call.

Incoming Call Sequence of Events

The following describes the sequence of events shown in Incoming Call Sequence of Events:

1. Phone B registers with VoIP server - The Security Appliance builds a database of the accessible IP phones behind it by monitoring the outgoing VoIP registration requests. SonicOS translates between phone B’s private IP address and the Security Appliance’s public IP address used in registration messages. The VoIP server is unaware that phone B is behind a Security Appliance and has a private IP address—it associates phone B with the Security Appliance’s public IP address.
2. Phone A initiates a call to phone B - Phone A initiates a call to phone B using a phone number or alias. When sending this information to the VoIP server, it also provides details about the media types and formats it can support as well as the corresponding IP addresses and ports.
3. VoIP Server validates the call request and sends the request to phone B - The VoIP server sends the call request to the Security Appliance’s public IP address. When it reaches the Security Appliance, SonicOS validates the source and content of the request. The Security Appliance then determines phone B’s private IP address.
4. Phone B rings and is answered - When phone B is answered, it returns information to the VoIP server for the media types and formats it supports as well as the corresponding IP addresses and ports. SonicOS translates this private IP information to use the Security Appliance’s public IP address for messages to the VoIP server.
5. VoIP server returns phone B media IP information to phone A - Phone A now has enough information to begin exchanging media with Phone B. Phone A does not know that Phone B is behind a Security Appliance, as it was given the public address of the Security Appliance by the VoIP Server.
6. Phone A and phone B exchange audio/video/data through the VoIP server - Using the internal database, SonicOS ensures that media comes from only Phone A and is only using the specific media streams permitted by Phone B.