To deploy Emergency call routing for direct routing users, Avaya SBC can be configured either as an ELIN gateway or not depending on the emergency calling network within a given country or region.

When Avaya SBC is used as an ELIN gateway, it is configured the same way as above with a few additional steps outlined below. When an emergency call arrives with ELIN number, Avaya SBC:

• Emergency routing service provider should be configured as trunk server in Avaya SBC.

• Avaya SBC should be configured to route Emergency URIs to Emergency routing service provider.

When Avaya SBC is used as an ELIN gateway, it is configured the same way as above. When an emergency call arrives with ELIN number, Avaya SBC:

• Parses ELIN phone number.

• Maps the emergency caller's number with the ELIN phone number.

• Stores ELIN number Mappings in an internal table.

• Substitutes the emergency caller's number with the ELIN phone number.

• Routes the call to the service provider configured on Avaya SBC.

Upon a call back to the emergency number, Avaya SBC will do the reverse called number substitution to that of the original emergency caller.

This mapping is kept in the internal table for a period of "Callback Timeout" in minutes and removed after. This helps to route the call back to original emergency caller in case call drops.