MAPS™ Diameter Protocol Emulator

Rx/Gx Interface

S13/S13' Interface

Testing CTF and OCS in Gy/Ro interface

As provided in the figure below, MAPS™ Diameter can be configured as CTF or OCS, while the other acting as the DUT in the network. If MAPS™ Diameter is configured as CTF, it tests the DUT (OCS) by initiating the messages towards OCS.

Similarly, if MAPS™ Diameter is configured as OCS, it tests the DUT (CTF) by receiving the requests from CTF and sending responses back to the CTF (DUT).

MAPS™ configured as CTF in GY/RO interface (Session Based Charging)

 Session Based Charging is a credit-control process that makes use of several interrogations: the first (INITIAL_REQUEST), a possible intermediate (UPDATE_REQUEST), and the final (TERMINATION_REQUEST). The first interrogation is used to reserve money from the user’s account and to initiate the process. The intermediate interrogations may be needed to request new quota while the service is being rendered. The final interrogation is used to exit the process.

The MAPS™ Diameter as CTF initiates a call by sending a CCR (Credit Control Request) message to the test the OCS. The CCA (Credit Control Answer) response message received back from the DUT (OCS) can be verified as shown in the message sequence window below.

MAPS™ configured as OCS in GY/Ro interface (Event Based Charging)

Event Based Charging is a  one-time event process used when there is no need to maintain any state in the Diameter credit-control server; for example, enquiring about the price of the service. The use of a one-time event implies that the user has been authenticated and authorized beforehand.

In CTF testing, MAPS™ Diameter is loaded with a set of inbuilt scripts to handle the incoming messages. MAPS™ Diameter acts as OCS and sends response to the one-time event based charging request as shown in the message sequence window below.

SLh Interface (LoCation Service)

SLg Interface (LoCation Service)

The following call flow illustrates the Provide Subscriber Location and Subscriber Location Report procedures over Diameter based SLg interface between GMLC and MME entities:

• Provide Subscriber Location - The Provide Subscriber Location operation is used by GMLC to request the location of a target UE from the MME
• Subscriber Location Report - Subscriber Location Report operation is used by MME or SGSN to provide the location of a target UE to GMLC when a request for location has been implicitly issued.

Sh interface

Method of communication between the AS (Application Server) function and the HSS (Home Subscriber Server), AS uses the Sh interface in two basic ways:

• To query or update a user's data stored on the HSS
• To subscribe to and receive notifications when a user's data changes on the HSS

The following illustrates the procedure in Diameter Sh interface:

CxDx Interface

The Diameter Cx and Dx interfaces are the reference points for interactions between Home Subscriber Server (HSS) and Interrogating Call Session Control Function (I-CSCF) or Serving Call Session Control Function (S-CSCF).

Serving-CSCF (S-CSCF) is always located in the home network. It is the central node of the signaling plane and performs session control as well. S-CSCF uses Diameter Cx and Dx interfaces to the HSS to download and upload user profiles, it has no local storage of the user. All requisite information will be loaded from the HSS.

Interrogating-CSCF (I-CSCF) is an another function located at the edge of an administrative domain. I-CSCF queries the HSS using the Diameter Cx interface to retrieve the user location and then routes the SIP request to its assigned S-CSCF.

Server-Assignment-Request (SAR): The Diameter client in a SIP server sends Server-Assignment-Request command to the Diameter server to indicate the completion of the authentication process and to request that the Diameter server store the URI of the SIP server that is currently serving the user. The main functions of the Diameter SAR command are to inform the Diameter server of the URI of the SIP server allocated to the user, and to store or clear it from the Diameter server.

Server-Assignment-Answer (SAA): The Diameter server sends Server Assignment Answer command in response to a previously received Diameter Server-Assignment-Request (SAR) command. The response may include the user profile or part of it, if requested.

User-Authentication-Request (UAR): The Diameter client in a SIP server sends User Authentication Request command to the Diameter server to request authorization for the SIP User Agent to route a SIP REGISTER request. Because the SIP REGISTER request implicitly carries a permission to bind an AOR to a contact address, the Diameter client uses the Diameter UAR as a first authorization request towards the Diameter server to authorize the registration.

User-Authentication-Answer (UAA): The Diameter server sends User-Authentication-Answer command in response to a previously received Diameter User-Authorization-Request (UAR) command. The Diameter server indicates the result of the requested registration authorization.