SNMP protocol overview and operation process

The network protocol architecture aims to effectively support normal network operations and facilitate management of massive networks. We should be familiar with the SNMP Protocol in terms of Network Management. The SNMP Protocol is "Simple Network Management Protocol ", SNMP is first organized by Internet Engineering tasks (IETF) to solve the router management problems on the Internet ｡

SNMP is currently the most commonly used Environment Management Protocol. SNMP is designed to be protocol-independent, so it can be used in IP, IPX, AppleTalk, OSI and other used transport protocols are used. They provide a method for collecting Network Management Information from devices on the network. SNMP also reports problems and the error provides a method ｡

Currently, almost all network equipment manufacturers have achieved support for SNMP. The most popular SNMP is a public communication protocol for collecting and managing information from devices on the network. and recorded in the management information library (MIB). This information reports device features, data throughput, communication overload, and errors. MIB have common formats, so SNMP management tools from multiple vendors can collect MIB information, presented to the system administrator on the Management Console ｡

By embedding SNMP in data communication devices, such as routers, switches, or hubs, you can manage these devices from a central station, view information graphically. Currently, many management applications can run in most of the currently used operating systems, for example, Windows 95, Windows 98, Windows NT, and UNIX of different versions ｡

A managed device has a management agent responsible for requesting information and actions from the Management site. The agent can also provide information for the management site by means of traps. Therefore, some key network devices (such as hubs, routers, and switches) provide this management proxy, also known as the SNMP protocol proxy, for management through the SNMP Management site ｡

SNMP running process

The AGENT residing on the managed device receives serialized packets from the network management site from UDP port 161. The nodes corresponding to the management variables in the MIB tree are obtained through decoding, group name verification, and analysis, obtain the value of the Management variable from the corresponding module, form a response message, and send the code back to the network management station. After the network management station obtains the response message, it returns the result after the same processing ｡

The following describes the actions taken by the Agent after receiving the packets based on RFC1157:

First, the message is decoded and generated in the internal data structure. The decoding is based on the Basic Encoding Rules of ASN.1. If an error occurs during this process and the decoding fails, the message is discarded without further processing ｡

Step 2: remove the version number in the message. If it is different from the SNMP Protocol version supported by this Agent, the message is discarded, the data communication product currently developed by Beijing only supports SNMP Version 1 ｡

Step 3: remove the group name in the message. The group name is filled in by the requesting Network Management site. If the group name does not match the group name recognized by the device, the message will be discarded without further processing, at the same time, a trap message is generated. SNMPv1 only provides weak security measures, which will be greatly enhanced in version 3 ｡

Step 4: propose the protocol data unit PDU from the verified ASN.1 object. If the PDU fails, the packet will be discarded without further processing. Otherwise, a message will be generated when the PDU is processed, the destination address of the message should be the same as the source address of the received message ｡

Common SNMP Program Development

Agent: NetSNMP, Agent ++, MG-soft, and solarwind

Management end: winsnmp-the SNMP library that comes with windows;

Snmp4j-JAVA version of the SNMP protocol stack;

ObjectSNMP-Object-Oriented java snmp Development Kit; O/M Mapping technology. SNMP protocol toolkit in Linux/Unix: net-snmp.