Howto:SIP redundancy / failover

FIXME: this article is still in progress and not finished yet

Overview

Often scenarios are needed in which a reliability of the SIP connection is to be realized. There are several approaches and scenarios for SIP redundancy or failover.

How well SIP redundancy and / or failover works depends on the interaction between the PBX and the carrier providing the SIP account.

PBX / Gateway

To support various carriers, we bring natively the following features which can be configured:

• Accepting trunk registrations from multiples Sources (GWs)
• Always place the call on a primary trunk and in case of a fault on a secondary trunk or round robin
• Receive calls from multiple trunk registrations
• Route calls between GWs back and forth

Carrier scenarios

Now it depends on the carrier featureset what you can do

Two permanent active SIP Interfaces

• SIP Interfaces on two Gateways with equal configuration
  • Both Interfaces register to the Trunk Object in the PBX
• The Carrier must be accept two registration from different souces with the same credentials
• The call distribution is not critical, only needs to be considered in the configuration
  • Some carriers put al incoming calls only on the first trunk and expect all outgoing calls over the same first trunk
    • Outgoing Calls must first send to the first Interface, then to the second one
  • Some carriers use both trunks for incoming and outgoing calls

Active SIP Interface, secondary disabled SIP Interface

• SIP Interfaces on two Gateways with equal configuration
  • Both Interfaces register to the Trunk Object in the PBX