1 Introduction

The Next Generation Network (NGN-Next GeneraTIon Network) is a packet-based network that uses a variety of broadband transmission technologies with QoS (Quality of Service) service quality assurance to provide various services including telecommunications services. NGN has the characteristics of separation of service and control, separation of control and bearer, and has the function of universal mobility. Users can flexibly and freely access different service providers through NGN. Softswitch network takes softswitch equipment as the core of call control, and provides real-time voice and multimedia service network on packet-switched network. Softswitch network is one of NGN implementation methods.

Softswitch systems include local network softswitches and long-distance network softswitches. This article mainly introduces the testing of the local network softswitch system. The softswitch networks in this article refer to the local network softswitch network. Softswitch system testing includes: testing of softswitch networking equipment and testing of protocols supported by softswitch networking equipment, various services, billing functions, network management systems, and interworking between softswitch networks.

2. Softswitch system test

2.1 Equipment test

(1) Equipment networking structure

Softswitch networking equipment mainly includes: softswitch equipment (Softswitch), signaling gateway (Signaling Gateway), application server (ApplicaTIon Server), media server (Media Server), integrated access media gateway (Integrated Access Media Gateway), China Trunk Media Gateway, Integrated Access Device (IAD), etc. Figure 1 shows the test logic network diagram of the softswitch system.

Figure 1 Soft switch system test logic network diagram

(2) Test content and method

The content of equipment test mainly includes: basic function test, statistical function test, network management function test, performance test, reliability test and clock synchronization test. Among them, the basic function test is mainly carried out on the basic capabilities of each device in the softswitch network, for example: softswitch equipment is mainly tested on call control and processing functions, and capabilities of lower-level device management functions; Tests for voice processing, resource control and other capabilities; signaling gateways are mainly tested for device networking capabilities and shielding functions. In the testing process, it is necessary to construct the environment for testing according to the different functions of different devices.

Because the capabilities of each device in the softswitch network are different from each other, the focus of the statistical function test of each device is also different. The softswitch devices focus on traffic statistics, and the relay media gateway pays more attention to link statistics. For signaling gateways, message count is an essential function. During the test, you can dial some calls on the network and operate some services to verify the statistical functions of each device.

The network management function test is mainly aimed at the network element management function test of the device, mainly including the SNMP protocol (Simple Network Management Protocol, simple network management protocol) test, configuration management test, fault management test, security and log management test, etc. This test requires configuration management operations on the device and verification to take effect. During the fault management test, some device faults can be manually set to verify the device alarm function. The operations and alarms performed on the device should be saved in the log.

The performance of the device determines the capacity and processing capacity of the network. Therefore, performance testing is an indispensable part for device testing. Among them, the performance of soft switching equipment is the most important. The performance testing of soft switching equipment includes equipment start-up time, capacity, call establishment time, long-term call and call processing ability tests. The keynote is that the performance design of the entire network is based on the performance of the softswitch equipment. In the same softswitch network, the performance of other networking equipment should be adapted and meet the performance requirements of the softswitch equipment. This test requires the call generator to simulate the call.

As a carrier-class equipment, the equipment in the softswitch network should have a relatively high reliability. Reliability tests include system startup tests, redundant backup tests, hot swap tests, system and equipment failure recovery time tests, equipment upgrade tests, etc. For the main control board of the device, it should be required to be able to be redundantly backed up and hot swapped, and it shall not affect the normal call during the operation.

In the soft switch system test, each networking device requires a clock synchronization test. In addition, since the networking equipment of the softswitch system is all IP bearers, more and more equipment manufacturers have added the NTP time synchronization function to the equipment to meet the needs of billing and instant bills. Therefore, with the addition of the NTP time synchronization function requirements, the time synchronization function test should also be added in the clock synchronization test.

In addition, the softswitch system networking equipment testing should also include testing the message tracking function of key devices in the network such as softswitch equipment and signaling gateways. In many cases, the device's message tracking function will be integrated into the network management function. Simultaneously with the network management function test.

2.2 Protocol testing

Softswitch standards and protocols are the key to network convergence. Now the industry, including equipment manufacturers and service providers, is working hard for the standard setting work, hoping to introduce advanced services and voice applications into the data network and integrate it smoothly with traditional networks. In the softswitch network, the protocols involved mainly include H.248 protocol, MGCP protocol, SIP protocol, SIP-I protocol, BICC protocol, M3UA protocol, M2UA protocol, etc.

(1) Protocol interface between devices

The protocol test mainly tests the support of the protocol for each device interface. Let's analyze the protocols supported by the device interface:

● SIP protocol is adopted between softswitch and application server.

● SIP / SIP-I or BICC protocol is adopted between softswitch and softswitch. When the softswitch network only supports traditional POTS terminals to provide traditional voice services, BICC or SIP-II protocols can be used between softswitches; when the softswitch network supports both traditional POTS terminals and SIP terminals, it is recommended to use SIP between softswitches / SIP-I protocol.

● The media control protocol is used between the softswitch and the media server, specifically SIP protocol, H.248 protocol or MGCP protocol can be used.

● The signaling transfer protocol (SIG-TRAN) is used between the softswitch and the signaling gateway to transmit high-level signaling information (TUP / ISUP / SCCP) of No. 7 signaling on the IP network. The specific SIGTRAN protocol is No. 7 signaling Let MTP third level user adaptation layer (M3UA) protocol.

● The interface between the softswitch and the relay media gateway (TG), which mainly completes the functions of media gateway control, resource control and management. The interface protocol is H.248 or MGCP protocol.

● The interface between the softswitch and the access gateway (AG) mainly performs media gateway control, resource control, and management functions. The interface protocol is H.248 or MGCP protocol.

● The interface between the application server / application gateway and the media server can use SIP protocol, H.248 protocol and MGCP protocol.

● The interface between the application server / application gateway and the signaling gateway can use the INAP protocol. The application server / application gateway communicates with the existing SSP / IP and other devices of the intelligent network through the signaling gateway, and through the INAP protocol to the soft switch users respectively Provide intelligent network services.

● The interface between softswitch and IAD can adopt H.248 protocol and MGCP protocol.

(2) Test method

In the softswitch system test, the protocol test is conducted for the system support protocol, and there is no need to perform protocol test for each device. When conducting MGCP, H.248, SIP protocol testing, you need to use the instrument to simulate MG and MGC separately for testing. First, the meter is connected to the softswitch, and the simulated MG (IAD, AG, SIP terminal) and softswitch send and receive messages to each other; the meter is connected to the MG, and the simulated softswitch and MG send and receive messages to each other.

When using the instrument in the protocol test, in addition to the normal message flow that needs to be checked, some abnormal message flows need to be checked.

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