Chapter 22 VoIP Solutions: SIP : FortiGate VoIP solutions: SIP : SIP and HA: session failover and geographic redundancy : Support for RFC 2543-compliant branch parameters
  
Support for RFC 2543-compliant branch parameters
RFC 3261 is the most recent SIP RFC, it obsoletes RFC 2543. However, some SIP implementations may use RFC 2543-compliant SIP calls.
The rfc2543-branch VoIP profile option allows the FortiGate unit to support SIP calls that include an RFC 2543‑compliant branch parameter in the SIP Via header. This option also allows FortiGate units to support SIP calls that include Via headers that are missing the branch parameter.
config voip profile
edit VoIP_Pro_Name
config sip
set rfc2543-branch enable
end
end