Network management history
The US Department of Defense designed ARPANET in one of the world's first few package exchange network. In the 1970s, the TCP / IP protocol was officially set as military communication standards, and the network management became a big event as the extensive use of this agreement. . In the 1980s, the Internet has developed rapidly in the early 1980s, and the increase in many subnets has enabled monitoring network activities a must.
In the early stages of network management, the management of the network is based on ICMP and PING, but with the increase in host data in the network, this simple tool is impossible to complete the work of network management.
SNMP history
With the increasing number of networks and hosts in the network, it is impossible to rely on some network majors to conduct network management. There must be a passive network management standard and corresponding management tools to manage networks. The first related protocol is SGMP, which provides a method of direct monitoring gateways, and therefore has become a general network management tool. Taken, there are three optional management tools: HEMS, SNMP, and CMIP (cMot) based on TCP / IP, because ISO / OSI models need to be used for network management, SNMP preferred CMOT as management tools. Basic SNMP has been widely used, all network products provide support for SNMP, newly developed SNMPs with remote management capabilities are RMON, which enables managers to manage the entire subnet instead of the entire subnet The device is managed.
Some definition
SNMP, Simple Network Management Protocol: Simple Network Management Agreement
It is a standard for managing protocols on the IP network. This agreement includes two data formats for monitoring and controlling variables and for monitoring devices: SMI and MIB.
MIB, Management Information Base: Manage Information Library
The management object database accessed by the Network Management Protocol, which includes SNMP that can be set via the SNMP management agent of the network device.
SMI, Structure Of Management Information: Management Information Structure
Used to define the rules for objects that can be accessed through the network management protocol. SMI defines the name or representation of the data type used in the MIB and the name or representation of the network resource in the MIB.
ASN.1, Abstract Syntax Notation ONE: Abstract syntax definition
The format of the SNMP is used to define the format of the SNMP protocol data unit and object in SNMP.
PDU, Protocol Data Unit: Protocol Data Unit
The packet transmitted in the network.
BER, Basic Encoding Rules: Basic Code Rules
The encoding rule specified by CCITT (X.209) and ISO (ISO 8825) describes how to represent the ASN.1 type as a string.
SNMP introduction
Network management using SNMP requires the following important parts: Manage base stations, managed agents, manage information libraries, and network management tools. The management base station is usually a separate device that is used as a user interface for network managers for network management. The base station must be equipped with management software, administrators can use, and obtain information from the MIB, and to perform network management it should have the ability to send the management command to the base station.
Management agents are a network device such as host, bridge, router, and hub, which must be able to receive information from the management base station, and their status must also be monitored by management base stations. The management agent responds to the request of the base station to perform the corresponding operation, or may send information to the base station without the request.
MIB is a collection of objects that represent resources and devices that can manage in the network. Each object is basically a data variable that represents information on one aspect of managed objects. The last aspect is the management protocol, that is, SNMP, the basic function of SNMP is: acquisition, set and receive unexpected information sent by the agent. The result is a base station sends a request. According to the corresponding data according to this request, the setting is the value of the base station setting management object (which is the agent), and the unexpected information transmitted by the agent means that the agent can be in a state where the base station is not requested. Accidents occurring in the base station report.
MIB and objects
The MIB includes a list of objects that are related to Object Identifier, indicating object type. The structure of the MIB is a tree structure. There are two ways to access the value of the object in the MIB. One is a quick access, another slow access, only entering some data when accessing, slow access, add other information.
SNMP MIB is the definition of objects is very strict, defining the data type of the object, the permitted form, the value range, and the relationship with other MIB objects. ASN.1 definition method is used to define each object while also defining the entire MIB structure.
There are two different object data structures: a special type of common type, universal type refers to integers, strings, null values, object identity, sequence, and serial number; dedicated type refers to network addresses, IP addresses, records, standards Wait.
To define the object itself, you must use asn.1. Below is a basic definition structure:
Begin
Exports
Imports
AssignmentList
End
software
The application can display SNMP data, and the application developed by NAS is a better tool in this regard. For details, please refer to: http://www.nas.nasa.gov/groups/lan/trouble/hnms.html
If you don't want to spend money, you can get a free management software below.
FTP: //ftp.ida.liu.se/pub/isode-snmpv2/iode-8.tar.gz ftp:/AllSpice.lcs.mit.edu/pub/snmp/ ftp: //ftp.net.cmu . 12.2ar ftp://ftp.cs.utwente.nl:/pub/src/snmp ftp://ftp.ecd.ucdavis.edu/pub/snmp/ UCD-SNMP.TAR.GZ http://www.cs.tu-bs.de/ibr/projects/nm/tkined/ http://www.cs.tu-bs.de/ibr/projects/nm/scotty /
Architecture
All TCP / IP layers under application layers have its own SNMP structural hardware manufacturer to implement the corresponding management structure in its product, but there are many MIBs, but the server has only one
Server processing process
The request for the base station has only two types, and the value and assignment a request can be performed.
ASN.1
ASN.1 is the basic type of SNMP for defining a MIB object using an ASN.1 subset of subsets: integer, string, object identifier, sequence, and null value BER to compile ASN.1 to SNMP can be transmitted. String, transfers between SNMP proxy. For variables ASN.1 use dictionary sequential sequential order, the namespace of the namespace of the hierarchical state can be defined to allow the server to directly respond directly to the request. All variables have post suffix iso.org.dod.Internet.mgmt.mib or 1.3.6.1.2.1
PDU
Customers can send the following three basic commands: Setting, reading, and remove a setting and reading instruction To make the server perform direct variable mapping Remove an instruction to specify the variable name to be taken, the server returns the name of the current row in the variable. The value of the variable name is the value of a variable. When this instruction is very useful when not knowing the table size, it is very useful in the hierarchical tree structure. Of course, this will be used to send requests and corresponding data corresponding to the request. Unnecessary pressures can also be made in a tree structure, if an unexpected situation occurs, the customer sends a message to the 162 port of the server to inform the server to change the variable value specified. The data typically obtained by the server request is received by the 161 port of the server. Hash table design
The HASH meter is used to quickly find variables. The Hash table is a pointer array, and each array points to a set of nodes having the same HASH value. If you need to find the value of the MIB variable, the server determines the number of sets of index values according to the number of variable names, by looking up the nodes pointing by the array, and each element in the MIB can be used in addition to using a dictionary In addition to sorting, there is also a pointer to the next element, which is especially useful when performing an instruction, and includes an ASN.1 name, and an address capable of all functions that can be made by this variable and The internal variable address initializes the value of these variables when the server is started.
SNMP summary
SNMP is an easy-to-implement basic network management tool that meets short-term management requirements. Because OSI-based management agreements are slow, it has played an important supplement.
The SNMP protocol provides protocol standards for defining network information and frameworks and for exchange information. The SNMP model introduces the concept of the manager and agent, the manager refers to the software that is responsible for all networks (or partial networks) as human administrators. The agent refers to the software in the managed device, which is used to complete the functionality of the local management and emergency notification manager you need to perform.
