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In which situations FoIP switches to a second call peer

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In which situations does Kofax Communiction Server - Fax over IP (KCS FoIP) switch to another / next configured call peer?


It is possible to configure multiple call peers within the KCS FoIP stack, by default the first call peer is used until it fails (Option Use first available call peer) and only then the second configured call peer is used. On the next call the first call peer is tried again to see if it's available. 

As mentioned, this is the default behaviour. It's also possible to configure two other failover strategies.

  • Use current call peer until it fails. Messages are sent out by the call peer that was most recently successfully used. If that fails, other call peers are used.
  • Load balancing (round robin). Call peers are used sequentially; each message is sent by another call peer. This strategy also takes into account the last known state of a call peer. Unavailable call peers are skipped, until a certain time period passes (30 seconds for busy and 5 minutes for unreachable). However, if all call peers are marked as being unavailable, KCS FoIP will attempt to use them for sending anyway. 

Below solution describes in which situations switching to another call peer occurs.


KCS FoIP switches to the next available call peer if the connection level of a failed call attempt is lower than 30.
See page 117 of the KCS FoIP technical manual for a description of all of the connection level values.

e.g. a SIP call completes with a connection level of 30 or higher if the initial SIP INVITE gets one of the following status values:

• 180 Ringing
• 200 OK
• 486 Busy Here
• 600 Busy Everywhere
• 603 Decline

So if the response to a SIP INVITE is one of the above, the current call peer is used,
When the response is something else; e.g. 503 Service unavailable, it switches to the next call peer.

Level of Complexity 


Applies to  

Product Version Build Environment Hardware
Kofax Communication Server All   Windows  



Article # 3039313
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