VoLTE Testing (Network Host)

Landslide supports the majority of the signaling aspects associated with creating a VoLTE call in the EPC. This support includes the following when testing an MME (MME Nodal test case) or SGW/PGW (SGW Nodal/PGW nodal test case).

Creation of multiple default bearers per UE during attach for Internet Access and IMS VoLTE access
UE IMS registration and authentication using IMS-AKAv1 or IMS-AKAv2 to real (customer) or emulated P-CSCF
Call initiation: DMF-based SIP call flow from UE to an emulated external SIP user to establish call.
Rx Message Trigger from emulated P-CSCF (in Network Host) to PCRF (real or emulated) to create dedicated SIP media bearer.
Establishment of the dedicated bearer to the UE
Transmission of an emulated RTP-based media stream over the dedicated bearer
Call Termination – SIP call flow from UE to an emulated SIP user to terminate call.
RX Message Trigger from emulated P-CSCF (Network Host test case) to PCRF (real or Emulated) to tear down dedicated SIP media bearer

Landslide also supports extensive testing of Circuit Switched Fallback (CSFB) functionality (2G and 3G networks) including the SGs interface to an emulated MSC/Call Server.

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Example VoLTE Configuration

The following illustrates a simplified VoLTE configuration for testing a combined SGW-PGW System Under Test (SUT).

Landslide test cases:

SGW Nodal Test Case emulates UEs, enodeBs and MME
PCRF Node Test Case emulates the PCRF
Network Host Test case emulates the Network host/P-CSCF.

The SIP RX DMF is assigned to the default bearer in the SGW nodal test case and in the External Network Host Test Case as well. The external Network host and PCRF are configured as described previously.

Simplified VoLTE configuration using Landslide SGW Nodal, PCRF Node, and External Network Host acting as P-CSCF.

Simplified VoLTE configuration using Landslide SGW Nodal, Landslide PCRF Node, and

External Network Host Configuration

The External Network Host test case emulates the P-CSCF side of the RX interface when the SIP RX DMF is used. The following configuration activates the Rx interface:

Rx option
Mobile subscribers options within RX message
Network Devices: AF SUT is PCRF Rx interface IP address
Network Devices: AF node is Network host/emulated P-CSCF RX interface IP address
Rf: Af Application ID for Rx interface: 16777236

PCRF Configuration

The Landslide emulated PCRF node may be used to generate the Gx messages to an emulated PGW or a customer/real PGW. In PCRF Node test case, the RX messages to the emulated PCRF will send GX messages to the PGW to create and/or delete dedicated bearer associated with VoLTE media stream. The following configuration is required:

AGW I/F with Gx
AF I/F with Rx
Session Stop from AF Server
Network Devices: AGW I/F Node is IP address of PCRF Gx interface
Network Devices: AF I/F Node is IP address of PCRF Rx Interface
Gx: Two rule sets required.
First rule set is for default bearer: Action: Install : Include Policy Rule with QOS class ID = 5
Second rule set is for dedicated Bearer: Action: Reserved: Include Policy Rule with QOS class ID = 1

SIP RX DMF

A customized SIP DMF named SIP RX is included in the Basic library, which enables the External Network Host test case to emulate P-CSCF side of the Rx interface for creation and deletion of the dedicated SIP bearer for the VoLTE call media stream.

NOTE: In Landslide release 10.8, this SIP RX DMF, or a DMF based upon this SIP DMF, is required if Landslide is emulating the P-CSCF. If a customer P-CSCF is used then the SIP RX DMF is not required. Landslide supports both IMS-AKAv1 and IMS-AKAv2 authentication.

The SIP RX DMF contains 2 external triggers (programmed) that emulate the P-CSCF end of the Rx interface. The SIP RX DMF sends the AA Request (AAR) message to the PCRF to create dedicated bearer at the beginning of the call and waits for the AA Answer (AAA) response from the PCRF on the Rx link before activating the Media stream subflow built into the DMF. After the media stream has completed, the SIP RX DMF will send the Session Termination Request (STR) and wait for the Session Termination Answer (STA) from the PCRF to terminate the dedicated bearer. The SIP RX message sequence is shown below.

NOTE: The SIP RX DMF should be included in the associated Nodal Test Case and the External Network Host test case for VoLTE testing.

Default Message flow for SIP RX DMF including the RTP Subflow

NOTES:

You may modify aspects of this DMF, but there is no guarantee that the messaging will still function properly if the control messages and paste buffers are significantly modified.
Modifying the contents of the RTP media stream subflow will not affect the SIP control, but may have an impact on the number of supported VoLTE calls due to increased data packet throughput.

The SIP RX DMF is a interim SIP solution until R11.0. In R11.0 the SIP functionality is integrated directly into the MME nodal and SGW nodal test case and an external IMS node emulator becomes available.