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Editor to share with you whether snmp is an application layer protocol. I hope you will get something after reading this article. Let's discuss it together.

Snmp is an application layer protocol. SNMP (simple Network Management Protocol) is a standard protocol specially designed to manage network nodes in IP network. It is located at the top layer of ISO/OSI and TCP/IP network model (that is, application layer). It belongs to the application layer protocol and relies on UDP protocol for transmission in the transport layer.

Simple Network Management Protocol (SNMP) is a standard protocol specially designed to manage network nodes (servers, workstations, routers, switches and HUBS, etc.) in IP networks. It is an application layer protocol.

A brief introduction to SNMP Protocol

Before you understand the SNMP protocol, you need to understand the network model of ISO/OSI and TCP/IP. ISO/OSI divides the network into seven layers, and TCP/IP divides the network into four layers (also known as five layers)

SNMP is located in the top layer of the two network models, that is, the application layer, which belongs to the application layer protocol. In the transport layer, it relies on the UDP protocol for transmission. The packet of SNMP is at the transport layer, so it is called PDU (Protocol data Unit).

SNMP (Simple Network Management Protocol) is a simple network management protocol, which is mainly used to manage devices in the local area network. The most widely used is the management of network devices such as routers and switches. Of course, it is not limited to network devices.

SNMP enables network administrators to manage network performance, identify and resolve network problems, and plan network growth. Receive random messages (and event reports) through SNMP. The network management system learns that there is a problem with the network.

SNMP is divided into management side and agent side (agent). The default port of management side is UDP 162.It is mainly used to receive Agent messages such as TRAP alarm messages; Agent side uses UDP 161port to receive messages sent by management side such as SET/GET instructions.

Differences between different versions of SNMP Protocol

At present, there are three versions of SNMP protocol, which are V1 Magi V2C Magi V3. The main differences are security, message encapsulation format, GET efficiency and so on.

1. Introduction of SNMPV1 version

SNMPV1 defines five types of PDU:Get (get parameter values, cannot traverse parameter groups of table type), GetNext (can get parameter values of table type, a set of parameters), Set (set parameter values) and Trap (send alarm), and Response (response information of GET operation).

SNMPv1 uses group characters (community) as authentication information. The message reply will not be made until the Agent receives a management-side message with the same group word.

The whole message of SNMPV1 is transmitted in clear text, which can be seen through wireshark/tcpdump and other packet grabbing tools.

2. Introduction of SNMPV2 version

SNMPV2 defines 7 types of PDU:Get (get parameter values, cannot traverse parameter groups of table type), GetNext (can get parameter values of table type, a set of parameters), Set (set parameter values) and Trap (send alarm), GetBulk (the basic operation corresponding to GetBulk operation is GetNext, by setting Non repeaters and Max repetitions parameters, efficiently obtain a large amount of management object data from Agent, if one of the parameters in get-request does not exist The request will still be executed normally. In SNMPv1, you will receive an error message), inform (equivalent to an upgraded version of Trap, but you will not receive a response message after the Trap message is sent, while an inform message will receive a response message after it is sent), Response (response information for the GET operation).

SNMPv2c also uses group character authentication.

The whole message of SNMPV2C is transmitted in clear text, which can be seen through wireshark/tcpdump and other packet grabbing tools.

3. Introduction of SNMPV3 version

Seven types of PDU in V2 are used in SNMPV3, with the addition of report (sending a message when it cannot be decrypted).

SNMPV3 uses USM and VACM technology. USM provides authentication and encryption functions, and VACM determines whether users are allowed to access specific MIB objects and how.

USM (user-based security model): Agent authenticates and verifies the integrity of the message by authenticating and verifying the user, password (encrypted by MD5 or SHA), authkey (authentication key) and engineid (identification code of agent). The whole message body is encrypted by DES.

SNMPV3 data messages are transmitted in ciphertext, and the actual content is not visible through packet grabbing tools such as wireshark/tcpdump.

When the SNMP manager communicates with the agent (Agent), both parties must have a common set of parameters in order to "communicate" normally. This set of parameters is called MIB (Management Information Base). Because the file organization format is a tree, collectively known as the MIB tree, the MIB trees of different manufacturers and different equipment types are generally different.

After reading this article, I believe you have a certain understanding of "whether snmp is an application layer protocol". If you want to know more about it, you are welcome to follow the industry information channel. Thank you for your reading!

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