CTC Union FRM220-NMC, Руководство пользователя

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Appendix A
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A.2.19 SNMP Configuration
A.2.19.1 General
The Simple Network Management Protocol ( SNMP ) is one of many protocols in the Internet Protocol (IP) suite.
SNMP is the protocol recommended specifically for the exchange of management information between hosts
residing on IP networks. Network management allows you to monitor and control network devices remotely using
conventional computer network technology.
The SNMP management functions of the 1000EAS are provided by an internal SNMP agent, which utilizes
communication over IP networks. The SNMP agent is compliant with the SNMPv1 and V2C standards. SNMP
communications use the User Datagram Protocol (UDP). UDP is a connectionless transport protocol, part of the
TCP/IP suite. The SNMP application uses an asynchronous command/response polling protocol and operates at
the OSI Layer 7 (Layer 7 is the Application Layer. Other IP applications that operate at this layer are FTP, Telnet,
HTTP, SMTP, etc.). All management traffic is initiated by the SNMP-based network management station. Only the
addressed managed entity (agent) answers the polling of the management station (except for trap messages).
A.2.19.2 SNMP Operations
The SNMP protocol includes four types of operations:
getRequest
Command for retrieving specific value of an "instance"
from the managed node. The managed node responds
with a getResponse message.
getNextRequest Command for retrieving sequentially specific
management information from the managed node.
The managed node responds with a getResponse
message.
getBulkRequest
Command for retrieving a block of management
information from the managed node. The managed
node responds with a getResponse message.
getBulkRequest was introduced in SNMPv2.
setRequest Command for manipulating the value of an "instance"
within the managed node. The managed node responds
with a getResponse message.
trap Management message carrying unsolicited
information on extraordinary events (that is, events
which occurred not in response to a management
operation) reported by the managed node.
A.2.19.3 The Management Information Base
The management information base (MIB) includes a collection of managed objects. Managed objects are
defined as parameters that can be managed, such as specific information on device configuring or on performance
statistics values.
The MIB includes the definitions of relevant managed objects (MIB variables) for the specific node. Various
MIB's can be defined for various management purposes, types of equipment, etc. The management data itself is a
collection of integer, string and MIB address variables that contain all the information necessary to manage the
node.
A leaf object's definition includes the range of instances (values) and the "access" rights:
Read-only
Instances of an object can be read, but cannot be set.
Read-write Instances of an object can be read or set.
Write-only Instances of an object can be set, but cannot be read.
Not accessible Instances of an object cannot be read, nor set.