With the rapid development of modern information technology, a large number of general and special information systems have been widely used in space ground systems. However, in the process of system integration, the diversification of communication systems of various communication equipment leads to the difficulty of system integration and the decrease of maintenance and support efficiency. In recent years, the space ground system follows the "three" design concept of generalization, serialization and combination, and adopts the unified new generation serial bus Standard VITA Standard 46 (VPX) to carry out the series design of each single equipment and module board, and realizes the interconnection between different supporting units. Although the traditional optical fiber transmission equipment, such as synchronous digital system (SDH), quasi-synchronous digital system (PDH) optical terminal and double wire transmission equipment, has been transformed according to the VPX design standard, mainly focused on the structural design, that is, the realization of communication equipment board card, but has not yet reached the degree of platform design. It also fails to effectively solve the problem of data transfer by means of intermediate equipment due to various transmission systems.
Platform design scheme
The platform design of optical fiber packet transmission module includes two parts: overall design and software design.
Integrated design
Fiber packet transmission module implements Layer 2 and Layer 3 protocols such as virtual Local Area Network (VLAN), Spanning tree Protocol (STP), Link Layer Discovery Protocol (LLDP), open Shortest Path First (OSPF) routing, and bidirectional forwarding detection (BFD). Provides operation, management, and maintenance (OAM), service bearing, service protection, and quality of service assurance based on multi-protocol Label Switching transport application (MPLS-TP). The optical fiber packet transmission module is divided into the main control switch module and interface module. The main control switch module switches and distributes Ethernet packets, controls routes, and protects and restores Ethernet packets. The interface module only needs to convert optical signals at the physical layer into Ethernet packets. In the data receiving direction, the interface module converts the input optical signal to optical/electrical, extracts the Ethernet data frame, and sends it to the main control switch module for processing through the high-speed serial interface. In the direction of data transmission, the main control switch module sends Ethernet data frames to the interface module through the corresponding high-speed serial interface based on the forwarding outlet, and the interface module converts Ethernet data frames into optical signals and sends them to the optical interface line. Sufficient service serial interfaces are planned for the main control switch module, and the number of external interfaces can be expanded and cut by adjusting the number of supporting interface modules. In addition to the standard Gigabit / 10-Gigabit Ethernet optical interface, the interface module can also be compatible with SDH and PDH through pseudo-line simulation.
Software design
Optical fiber packet transmission module includes three main software configuration items: CPU software of main control switch module, MCU software and interface module FPGA software. Although MCU software runs on different modules, they are still treated as the same software configuration item. The CPU software of the main control switch module runs in the Linux operating system and consists of multiple processes. The network service implements Layer 2 and Layer 3 protocols, PTN service management and message distribution among protocol processes. OAM management covers the OAM management and connectivity management (CFM) of MPLS-TP services. Route management implements OSPF routes. The hardware adaptation layer is responsible for receiving configuration messages from the network service and configuring the switching chip by calling the SDK API. The SNMP agent implements the communication function of the SNMP interface. The northbound interface agent communicates with northbound interfaces. The system management section covers device management, condition monitoring, and communication with MCU software.
Conclusion
The scheme adopts the unified service carrying mode based on packet switching and reuses the VPX standard interface, which effectively meets the service transmission requirements based on packet data and the supporting requirements of space ground system. Through the mechanism of automatic module identification, automatic port registration and snapshot organization of module information, it can flexibly adapt to different external interface requirements by configuring different types and quantities of interface module hardware boards without changing the software design. At present, the scheme has been widely used in the space ground system, forming a series of products that support the unity of hardware and software and the interchange of module level.