Lync Emergency Call SPL Plug-in

When using the Oracle® Enterprise Session Border Controller (ESBC) as a gateway for E911, service providers may require a Post-dial-delay of 6 seconds or greater to receive an 18x message and progress the session. Microsoft Lync emergency calls have an internal timer of 10 seconds to route advance to the alternate gateway in the event no 18x message is received. The Lync Emergency Call SPL plug-in responds to the initial INVITE with the 183 message, allowing theESBC to ensure normal call delivery when there is Post-dial-delay on egress routes that exceed the Lync emergency call timer.

When enabled, the return_183_on_initial_invite SPL plug-in sends a provisional 183 session progressing message to Lync when the ESBC receives the initial INVITE request. This satisfies the 10 second emergency call timer.

The ESBC monitors the primary and secondary trunks with a SIP OPTIONS ping. If the primary trunk is unavailable, the system automatically fails over to the second destination in session-group and completes the call.

In the following example, the ESBC replies to an emergency call INVITE from Lync with a SIP 183 message. Lync moves the call and dialog to RFC 3261 Timer C (180 seconds), allowing sufficient time to complete the call and to find the nearest PSAP (Public Safety Answering Point) with the primary trunk. If the primary trunk is unavailable (The system monitors the two trunks with a SIP OPTIONS ping), the system routes the emergency call by failing over to a secondary trunk to complete the call.

The Lync emergency call SPL call flow is described above.

Set Lync Emergency Call Options on Realms, Session Agents, and SIP Interfaces

You can configure the return_183_initial_invite option on each session-agent, realm-config, or sip-interface that interacts with Microsoft Lync. This option is not recognized in the global spl-config and is required for SPL functionality.

In Superuser mode, type configure terminal, and press Enter.
```
ACMEPACKET# configure terminal
```

Type session-router, and press Enter.

ACMEPACKET(configure)# session-router
ACMEPACKET(session-router)#

Type session-agent, and press Enter.

ACMEPACKET(session-router)# session-agent
ACMEPACKET(session-agent)#

Type spl-config , and press Enter.

ACMEPACKET(session-agent)# spl-config
ACMEPACKET(spl-config)#

Type spl-options +return_183_initial_invite.

ACMESYSTEM(spl-config)# spl-options +return_183_initial_invite

Type done to save the configuration.

Example Playback-on-Refer Configuration

The following code block shows an example of a playback-on-refer configuration:

session-router
	session-agent
		spl-config
			spl-options          +return_183_on_initial_invite