Design of Embedded Agent for OBS Network Management Based on SNMP
Figure 2 shows the basic model of OBS network management [1]. It can be seen from the figure that the Agent is mainly responsible for handling 3 things [1,2]: 1) The Agent communicates with the Manager through the SNMP protocol, obtains the management command sent by the Manager and responds to the management command, or in the form of a trap (Trap) The form reports some important events to the Manager to the Manager. 2) The Agent and the managed device communicate with a dedicated management protocol (mostly a custom protocol) to obtain information about the managed device object, complete parameter configuration, performance statistics, and fault reporting. 3) Agent must also be responsible for maintaining management information base (Management InformaTIon Base, MIB), including reading or modifying various variable values ​​in MIB.
Figure 2 OBS network management basic model
2.1 Simple Network Management Protocol The current industry's de facto network management standard SNMP is an application layer protocol [1], and there are currently SNMPv1, SNMPv2 and SNMPv3. The biggest feature of SNMPv1 is simplicity, easy implementation and low cost [1]. Compared with SNMPv1, SNMPv2 focuses on improving the management information structure, communication capabilities between managers and protocol operations [1, 3]. SNMPv3 defines a system framework including all functions of SNMPv1 and SNMPv2 and a brand-new security mechanism including authentication services and encryption services. It provides a set of special network security and access control rules, which greatly enhances the effectiveness of network management. And security [1,4].
2.2 The MIB definition management information base (MIB) of OBS network management is the core of the network management system, and the most widely used at present is MIB-II. For the OBS network management system, it mainly completes the management of edge nodes and core node objects, including working status, configuration parameters, performance statistics, and fault alarms.
The working state needs to define the working conditions of nodes and ports. The configuration parameters need to define the number of wavelengths, label forwarding table, IP routing table, buffer length, burst offset time, burst packet length, etc. Performance statistics need to be considered for edge nodes The average burst queue length, IP packet traffic, Burst traffic, etc. For the core node, it is necessary to consider the burst header packet (BHP) received by each port, the BHP forwarded by each port, the occupancy rate of each wavelength in each port, etc. For fault alarms, it is necessary to define possible optical device failures such as optical switches and optical delay lines (FDL).
According to the defined node objects, they are described with Abstract Syntax Notation 1 (Abstract Syntax NotaTIon One, ASN.1) [5, 6].
2.3 Embedded Agent software structure design From Figure 2 it is known that Agent acts as an agent like the name, responding to the Manager's operation request on the top, translating the Manager's instructions to the bottom, and traps (Trap) that appear in the managed object ) Reported to the Manager in time, and also responsible for maintaining the MIB library. Therefore, to complete the above functions, the embedded Agent software must include 4 parts in structure [7] (as shown in Figure 3):
1) SNMP protocol module: This module can be subdivided into socket communication module, pdu processing module and trap processing module. The socket communication module is responsible for accepting the Manager's operation request on port 161 and responding to the request, and sending the trap (Trap) or the notification (Inform) that needs to be responded on port 162. The pdu processing module and the Trap processing module are responsible for encapsulating or parsing the SNMP related operations. In order to realize the communication between SNMP Agent and Manager. 2) MIB management module: this module includes registration module, search module and access module. The registration module is responsible for the deconstruction of the MIB library and the realization of the legality of the object node, the search module is responsible for implementing the fast search algorithm for the node, and the access module is responsible for the management of the legal access to the data of the node, so as to avoid the MIB library under unexpected circumstances You may be in danger of collapse. 3) MIB processing module: This module actually corresponds to a specific implementation routine, which completes parameter configuration of specific nodes, information acquisition and trap processing, etc. 4) Remote communication module: This module mainly deals with the communication problem between Snmp Agent and managed device objects. In this design case, the collected data is obtained through the RS232 serial port protocol, and the message queue provided in the uClinux system is used to enable the Agent to communicate with the managed device object.
Figure 3 Embedded Agent software structure
2.4 Software and hardware development environment
The system core board of the OBS switching node adopts Motorola MCF5272 microprocessor, 16 M SDRAM and 4 M FLASH, and the embedded operating system adopts uClinux. The embedded agent software is designed in C language, using Redhat linux7.2 as the basic development environment, and ucd-snmp is selected as the agent software development kit, which is continuously compiled and debugged and finally transplanted into uClinux to run.
Realization of Embedded Agent Based on SNMP in OBS Network
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