Navigation: System Settings > Line > Add/Edit Trunk Line > SIP Line > SIP Engineering
You can use this tab to enter commands that apply special features to the SIP line. The commands are called SIP Line Custom (SLIC) strings.
These settings can be edited online. Changes to these settings do not require a reboot of the system.
reINVITE Codec Renegotiation
For R11.0 and higher, the IP Office supports codec renegotiation when a reINVITE is received. See Codec selection.
You can use the following command to retain the pre-R11.0 behavior of no renegotiation. Note: On existing IP Office systems upgraded to R11.0 or higher, this command is automatically added to all existing SIP lines.
SLIC_STIR_REJECT_CODE=<n> where <n> is the response code sent for calls rejected by the IP Office.
SLIC_STIR_REJECT_STRING=<y> where <y> is the response string sent for calls rejected by the IP Office.
SLIC_STIR_ATTEST="<w>" where <w> is the name of the header the IP Office checks for a call's authorization level.
SLIC_STIR_CUSTOM=<z> where <z> value enables or disables various call features.
Server Name Identification (SNI)
The following SLIC codes can be used for SIP trunks using TLS. When used:
On outgoing connections, the IP Office adds Server Name Indication (SNI) information to the SAN field it sends.
If the IP Office system's Received certificate checks (Telephony endpoints) settings is set to Medium + Remote Checks or High + Remote Checks, then the SLIC value is also used to validate the received certificates SAN.
The SLIC codes are:
SLI_ADD_SIP_SAN=<X>
Use a SNI set to sip:<SNI> where the <SNI> value is taken from the existing IP Office SIP line configuration based on the following values of <X> as below:
D = Use the value of the SIP line's ITSP Domain Name setting (Line > SIP Line). For example, for a SIP line with the ITSP Domain Name set to ipo.example.com, adding SLIC_ADD_SIP_SAN=D sets the SNI added to sip:ipo.example.com.
P = Use the value of the SIP line's configured ITSP Proxy Address setting (Line > Transport > ). This option is only supported for a ITSP Proxy Address set to a single address. For example: SLI_ADD_SIP_SAN=P
Keepalives
Supported with IP Office R11.1.3.1 and higher.
You can add SLIC_HNT_EMPTY_PACKET to have the SIP line send RTP packets with payload 20 (unassigned payload) and no data as keepalives. This overrides the default of send STUN packets for keepalives.
