Chapter 6:SNMP Management: SNMPv2 6.3.1 SMI Definitions for SNMPv2 SMIv2 structural indentations to bring out clearly the BEGIN and END of macros.The definitions begin with the high-level nodes under the Internet MIB.Two additional nodes, security and SNMPv2,are introduced.Security node is just a placeholder and is reserved for the future.The snmpV2 node has three subnodes: snmpDomains,snmpProxys,and snmpModules. The MIB tree showing all these nodes defined in SMIv2 is presented in Figure 6.5
Chapter 6: SNMP Management: SNMPv2 6.3.1 SMI Definitions for SNMPv2 SMIv2 structural indentations to bring out clearly the BEGIN and END of macros. The definitions begin with the high-level nodes under the Internet MIB. Two additional nodes, security and SNMPv2, are introduced. Security node is just a placeholder and is reserved for the future. The snmpV2 node has three subnodes: snmpDomains, snmpProxys, and snmpModules. The MIB tree showing all these nodes defined in SMIv2 is presented in Figure 6.5
internet 039 (1361月 6冷925的 AOITAOIITOW 038 directory mgmt experimental private security () snmpV2 ②) (3) 4 5) () 四42 snmpDomains snmpProxys snmpModules ) (2) 3) Figure 6.5 SNMPv2 Internet Nodes Defined in SMlv2
6.3.2 Information Modules RFC 1902 defines information module as an ASN.1 module that defines information relating to network management.The SMI describes how to use a subset of ASN.1 to define an information module.Three kinds of information modules that are defined in SNMPv2:MIB modules,compliance statements for MIB modules,and capability statements for agent implementations.This classification scheme does not impose rigid taxonomy in the definition of managed objects.The information on SMIv2 has been split into three parts in the documentation.MIB modules for SMIv2 are covered in RFC 1902.The textual conventions to be used to describe MIB modules have been formalized in RFC 1903.The conformance information,which encompasses both compliance e and agent capabilities,is covered in RFC 1904
6.3.2 Information Modules RFC 1902 defines information module as an ASN.1 module that defines information relating to network management. The SMI describes how to use a subset of ASN.1 to define an information module. Three kinds of information modules that are defined in SNMPv2: MIB modules, compliance statements for MIB modules, and capability statements for agent implementations. This classification scheme does not impose rigid taxonomy in the definition of managed objects. The information on SMIv2 has been split into three parts in the documentation. MIB modules for SMIv2 are covered in RFC 1902. The textual conventions to be used to describe MIB modules have been formalized in RFC 1903. The conformance information, which encompasses both compliance and agent capabilities, is covered in RFC 1904
6.3.3 SNMP Keywords The keywords used in the specifications of SMIv2 are a subset of ASN.1.But it is a different subset from that of SMIv1.P238 Table 6.1 shows the comparison of keywords used in the two versions.It's worth noting here that some general keywords have been replaced with limited keywords.Thus,Counter is replaced by Counter32,Gauge by Gauge32,and INTEGER by Integer32.The NetworkAddress is deleted from use and only the IpAddress is used. Note that reference in IMPORTS clause or in clauses of SNMPv2 macros to an informational module is not through "descriptor"as it was in version 1.It is referenced through specifying its module name,an enhancement in SNMPv2.Note also that the expansion of the ASN.1 module macro occurs during the implementation phase of a product,and not at run-time
6.3.3 SNMP Keywords The keywords used in the specifications of SMIv2 are a subset of ASN.1. But it is a different subset from that of SMIv1. P238 Table 6.1 shows the comparison of keywords used in the two versions. It's worth noting here that some general keywords have been replaced with limited keywords. Thus, Counter is replaced by Counter32, Gauge by Gauge32, and INTEGER by Integer32. The NetworkAddress is deleted from use and only the IpAddress is used. Note that reference in IMPORTS clause or in clauses of SNMPv2 macros to an informational module is not through "descriptor" as it was in version 1. It is referenced through specifying its module name, an enhancement in SNMPv2. Note also that the expansion of the ASN.1 module macro occurs during the implementation phase of a product, and not at run-time
6.3.4 Module Definitions The MODULE-IDENTITY macro is added to SMIv2 to specify an informational module.The SMIv2 MODULE-IDENTITY macro is presented in Figure 6.7. Figure 6.8 shows an example of a MODULE- IDENTITY macro (a hypothetical example of a nonexistent module)for a network component vendor, InfoTech Services,Inc.(isi). The last-updated clause is mandatory and contains the date and time in UTC (universal time)format [RFC 19021."Z"refers to Greenwich mean time (GMT).The Text clause uses the NVT ASCII character set [RFC 854],which is a printable set.All clauses,except the revision clause,must be present in the macro
6.3.4 Module Definitions The MODULE-IDENTITY macro is added to SMIv2 to specify an informational module. The SMIv2 MODULE-IDENTITY macro is presented in Figure 6.7. Figure 6.8 shows an example of a MODULEIDENTITY macro (a hypothetical example of a nonexistent module) for a network component vendor, InfoTech Services, Inc. (isi). The last-updated clause is mandatory and contains the date and time in UTC (universal time) format [RFC 1902]. "Z" refers to Greenwich mean time (GMT). The Text clause uses the NVT ASCII character set [RFC 854], which is a printable set. All clauses,except the revision clause, must be present in the macro