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1. Introduction to SNMP#

The chapter introduces the Simple Network Management Protocol (SNMP) and explains the components of ALTIBASE-MIB.

What is SNMP?#

Overview of SNMP#

The Simple Network Management Protocol (SNMP) is a protocol that communicates the network server status and the process status to the manager.

Before the SNMP was used, the Internet Control Message Protocol (ICMP) was used to provide brief information, such as whether each network host was functioning properly, if so, its response time, and so on. One of the most useful tools using ICMP is probably the Ping program.

As the use of the internet became widespread, the number of network hosts increased, and this lead to a complex network environment. Since it became impossible to manage network using only ICMP efficiently, research was conducted on alternative protocols, and this lead to the development of SGMP, HEMS, CMIP/SMIS, and so on. Among these, SNMP (an improvement to SGMP) became the standard protocol for network management.

SNMP is an improvement to SGMP and accepts the MIB definition for HEMS.

Management Information Base (MIB) Structure and OID#

SNMP manages a Management Information Base (MIB), which is the categorized information of objects to be managed. System information, network usage, network interface information are examples of such objects. The SNMP agent monitors traffic and stores statistical information in its MIB. Variables defined by the MIB can be changed with a Network Management System (NMS) or by the SNMP manager.

The general structure of the MIB is shown below. MIB objects are structured as a tree for easy management.

Data is requested as below: 

ISO.org.dod.internet.mgmt.mib-2.system.sysDescr

However, this request is converted to numbers when requesting for data as below: 

1.3.6.1.2.1.1.1

Each MIB can be represented in numbers. These numbers are called OIDs.

Internet Assigned Number Authority (IANA) maintained MIBs are acknowledged as the standard. IANA OIDs are necessary to implement a standard MIB module. This way, users can use multiple MIBs without having to worry about duplicates.

[Figure 1-1] Typical MIB Structure

ALTIBASE-MIB#

Altibase has registered an entity and uses the IANA OID altibase(17180) under enterprises(1)1.

[Figure 1-2] ALTIBASE-MIB

ALTIBASE-MIB is classified as altiTrap, altiPropertyTable, and altiStatus. Each MIB contains the following information for which further information is given in the next chapter.

  • altiTrap
    Defines the OID used in the trap when a significant situation is detected.

  • altiPropertyTable MIB
    Reads or changes Altibase's environment properties.

  • altiStatus MIB
    Displays Altibase's status

This section explains SNMP terminology in Altibase.

[Figure 1-3] Diagram of SNMP

  • SNMP((Simple Network Management Protocol))
    SNMP is a protocol for network management. Information such as the network server status, the process status, and so on is sent to the manager.

  • MIB(Management Information Base)
    MIB is a categorical classification of the objects used by SNMP to monitor and control the network. System information, network usage, network interface information, and so on are target objects for management. MIB objects have a tree structure for easy management.

  • OID
    When requesting information, MIB can be represented as numbers. OIDs are granted OID numbers from the Internet Assigned Number Authority (IANA) to implement a standard MIB.

  • ALTIBASE-MIB
    Altibase has registered an entity and uses the IANA OID altibase(17180) under enterprises(1)1.

  • SNMP Agent
    The SNMP agent installs sniped and snmptrap in a monitor object, collects management information, and sends it to the manager.

  • snmpd
    snmpd is the SNMP master agent daemon.

  • snmptrapd
    snmptrapd is the daemon for SNMP traps.

  • altisnmpd
    altisnmpd is the SNMP subagent daemon installed on the Altibase server.


Altibase SNMP Model#

This section discusses how SNMP manages a network.

[Figure 1-4] Altibase-SNMP Model

The figure above shows how snmpmanager imports Altibase MIB (The port number is net-snmp by default). This is the sync method. If snmpmanger sends a request on UDP port 161, snmpd passes this request to altisnmpd on TCP port 705, which in turn altisnmpd ultimately passes on to Altibase on UDP port 20400. When altisnmpd receives a response from Altibase, altisnmpd passes it on to snmpd and this is ultimately passed on to snmpmanger.

The figure below shows how a trap raised in Altibase is passed on to snmpd. This is the async method. If Altibase passes the trap to altisnmpd on UDP port 20500, altisnmpd passes it on TCP port 705 to snmpd, and snmpd ultimately passes it on UDP port 162 to snmptrapd.

Altibase's own protocol is used between Altibase and altisnmpd. AgentX, the standard protocol for master agent/subagent communication is used between altisnmpd and snmpd.

The SNMP is used as the standard protocol between snmpd, snmpmanager, and snmptrapd.

  1. An MIB has a hierarchical structure and can be extended when necessary. The user may wish to add an MIB for a product only available for use in the office or a product that controls the network within a limited network area. In this case, the user can create user's own MIB and define it under private(4) and enterprises(1). ↩↩