Measure the test taker's knowledge about the implementation of 2 m high-speed links in the softswitch system gateway.

There are many things worth learning about the softswitch system. Here we mainly introduce the implementation of 2 m high-speed links in the softswitch system gateway. At present, the telecom business is developing rapidly and new businesses are emerging constantly. With the development of Internet networks, the data business is growing rapidly, not only in the traditional narrowband Circuit Switching Network SCN) provides telephone services and intelligent network services, and also needs to provide these services in the IP network.

Due to business development requirements, circuit switching networks and the Internet that supports telephone services are required to communicate with each other. In order to realize the intercommunication between SCN and the IP network, the No. 7 signaling that is used to support SCN also needs to communicate with the IP address. Therefore, the data network based on group switching and the circuit switching network will eventually converge to form a unified IP core network, that is, the next generation network. The Next Generation Network is a brand new network that integrates voice, data, fax, and video services. The softswitch system is born under the needs of the next generation network.

Softswitch system

In the circuit switching network, call control, service provision, and switching matrix are all concentrated in one switching system. The main design concept of the softswitch system is the separation of business/control and transmission/access, entities connect and communicate with each other through standard protocols, so as to provide various services more flexibly online. The softswitch system is a software-based distributed exchange/control platform that separates the call control function from the gateway and opens the protocol between services, control, access, and exchange, the concept of "network is exchange" is introduced to truly implement the network operation environment of multiple manufacturers and facilitate the introduction of various services on the Internet. To achieve intercommunication between the signaling 7 and the IP network, a signaling gateway device is required.

Signaling Gateway

The signaling gateway is a device that connects the No. 7 signaling network and the IP network. It is mainly used to convert the signals on the PSTN/ISDN side to those on the IP side. The signaling gateway is the signaling proxy for receiving and sending signaling messages at the edge of the No. 7 signaling network and the IP network. The signaling gateway is used at the gateway of the No. 7 signaling network and the IP network to relay, translate, or terminate signaling messages. M3UA is used to regulate the transmission of signaling between the signaling gateway SG and the Media Gateway controlling MGC) or between databases. M3UA supports MTP user signaling of any number 7, such as ISUP and SCCP messages), and implements intercommunication between the number 7 signaling and the IP network through IP-based Stream Transmission Control Protocol SCTP.

According to the standard, the softswitch system should support 10 Mbit/s/Mbit/s adaptive Ethernet interfaces on the IP network side, and support 64 Kbps and 2 Mbit/s signaling links on the circuit switching network side. When the signaling gateway only uses 64 Kbps, it has a large asymmetry compared with the IP network transmission rate. Therefore, it is necessary to introduce a 2 Mbit/s high-speed link.

2 m high speed link

The 2 m high-speed link belongs to the MTP2 part of the No. 7 signaling and is a link layer protocol. Together with MTP1, MTP1 provides a signaling link for transmitting signal messages between two points, and defines the functions and procedures for transmitting signal messages on a signaling link. On the one hand, MTP2 needs to send the signal messages to be sent to the signaling data link MTP1 Based on the MTP3 coding function, and transmit the correctly received signal messages to MTP3. On the other hand, information about the status of the signaling link and the working status of the processor should also be transmitted within or between the two signaling point terminals, and relevant control activities should be carried out.

Software Implementation

According to the technical specifications of 2 Mbps high-speed link, it is divided into eight relatively independent functional modules. The functions of each module are as follows:

1) Link Status Control LSC) LSC controls and manages the link status. When a signal unit in the link status is received, function modules or level 3 should be notified about the link status at the peer end. LSC should be used as the control module to control the operation of other related modules.

2) start positioning control IAC) when the signal link is started for the first time or the link is recovered after a fault occurs, start IAC and perform emergency locating or normal locating according to MTP3 commands.

3) processor fault control POC) records whether the local processor and remote processor are faulty, and notifies LSC of "No processor fault" based on fault recovery ".

4) Basic sending control TXC) is used for sending signal units, controlling the sending sequence of the signal units, verifying the other party, and re-sending the signal unit when an error occurs.

(5) RC (basic receiving control) is used for receiving signal units. It checks whether the received signal units arrive in order and whether the received signal units are valid. When packet loss occurs, notify TXC to send a negative confirmation.

6) Positioning Error Rate Monitoring AERM) is used in the verification status of the signaling link in the initial positioning process. It collects statistics on the error rate of the signal unit and determines whether to terminate the verification.

7) error time period monitoring EIM) by monitoring the error situation of the queue model established by the sender within the specified time period, to determine whether the link is in a fault condition.

(8) congestion control CC) controls the traffic of signal messages. In order to distinguish from faults, SIB is sent regularly when congestion occurs.

We use C language programming to implement its functions. The hardware completes error detection and identification, and the operating system platform running the program is VxWorks. Each module in MTP2 communicates with each other using the status word, and uses the status word to indicate the status of each module. The most basic function of MTP2 is to send and receive messages. Each interface of TXC and RC must be provided to send and receive messages.

Level 2 and Level 3 Interfaces

In principle, the second and third-level interfaces do not need to be modified. Because the service load on the 2 m high-speed link is large, the buffer capacity opened for the faulty link should be larger than the buffer value of 64 Kbps, the buffer size should be determined based on the specific application.

Test Results

Since the maximum rate is generally not reached during actual use, in order to accurately understand QMC's support for data rate, QMC's message sending and receiving rate is tested based on the above configuration method. Test the data transmission rate of QMC in a closed loop. The result is as follows: the zero time slot of the E1 link is used to transmit the synchronous signal, and each channel uses only 31 time slots, therefore, the ideal speed should be 64 kbps × 31 = 1,984 kbps. The test results show that the actual rate reaches 99% of the ideal rate. Considering the required delay, it can be considered to meet the speed requirements of 2 m high-speed link technical specifications.

Summary

This article introduces the implementation of 2 m high-speed links in the signaling gateway and the configuration of the MPC860QMC. The fast processing speed and powerful communication processing capability of the MPC860 provide good real-time performance for the system, it also has the upgrade capability and can be upgraded to the MPC8260, supporting more 2 m links. According to the technical specifications, up to 16 signaling links can be configured between two signaling points in the No. 7 signaling network. When using a 64 Kbps signaling data link, the maximum signaling transmission bandwidth between two signaling points is 64 kbps × 16 = 1024 kbps. Currently, it cannot fully meet the business needs of the No. 7 signaling network. Therefore, a 2 m high-speed link can also be used between the gateway of the No. 7 Signaling Network to increase the transmission bandwidth and meet service requirements.