SNMP and Isode Servers
This whitepaper looks at the role of SNMP (Simple Network Management Protocol) in managing systems using Isode's messaging and directory servers. It explains why SNMP support is provided, the sub-agent architecture used by Isode products, and approaches to deploying SNMP monitoring.
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Goals of Isode Monitoring & Management Tools
Isode provides a number of GUI tools, such as MConsole (Message Console) to enable sophisticated monitoring and control of the Isode server products. These Isode GUI tools have three basic roles:
- To enable monitoring of the Isode servers.
- After a problem has been flagged, to help identify the details of the problem and its cause, and to enable appropriate configuration, parameter changes where needed.
- To enable the operator to view events, both errors and informational.
Operator Requirements and SNMP
For many deployments, it is important that a system operator watches the Isode servers to ensure correct operation and to rapidly respond to any problems. Isode's own tools are appropriate for this task, particularly where an operator is dedicated to the Isode servers.
In most deployments, where problems in one component (e.g., a network failure) will have effects on others, an operator will be expected to monitor many applications, servers and network components. Using a different monitoring system for each component is problematic, as:
- Each monitoring application is different.
- There is a real problem in managing "screen real estate".
The solution to this is to use a general purpose monitoring tool. The most popular tools make use of the Internet Standard SNMP (Simple Network Monitoring Protocol), which is supported by many network components and applications. A wide range of Management Consoles, such as HP Openview, use SNMP.
Isode does not use SNMP in its own management tools as SNMP does not provide appropriate functionality. Isode provides SNMP capabilities to integrate with third party monitoring tools. The key goal is to enable operators to be rapidly made aware of any problems. Isode tools can then be used for detailed diagnosis and problem resolution.
SNMP Monitoring works by the Management Console using SNMP to query an SNMP agent to retrieve information on the managed applications. The Management Console then presents this information to the operator, drawing operator attention to general system status and to problems.
Isode uses as sub-agent model for support of SNMP. This works by having a single Master Agent on a server, that will respond to external queries. Then the master agent interacts with sub-agents associated with each of the monitored servers. This enables the Management Console to get information from the application. Isode uses the Internet Standard AgentX protocol (RFC 2741) to communicate between the master agent and sub-agent. Full sub-agent and AgentX support is included with the Isode servers.
AgentX is widely supported by SNMP master agents, and the standard SNMP agent on most Unix platforms supports AgentX. For other platforms, Isode recommends the widely used Net-SNMP master agent. On Windows, the Net-SNMP master agent will support Windows sub-agents (using a Windows API) and will also support the Windows master agent as a sub-agent (using SNMPv2c).
There are a number of benefits to using a sub-agent architecture:
- SNMP functionality in the subagent only needs to deal with application specific information.
- Communication to the master agent with a single standard protocol reduces application monitoring complexity, and thus increases performance and resilience.
Isode MIB Support
The SNMP framework enables monitoring of an enormous variety of network components and applications by use of the MIB (Management Information Base) concept. A MIB defines the variables that are available in the application to be monitored using SNMP. A MIB provides a list of variables and tables, that look complex at first sight, but are generally a quite logical representation of useful information. There are three Internet Standard MIBs of particular importance to Isode, that are collectively known as the MADMAN (Mail And Directory MANagement) MIBs. These are:
- Network Services Monitoring MIB (RFC 2788) defines a generic MIB that is appropriate to any application that can make a network connection. It provides information on the basic application status, and information on active connections, including how long the connection has been running and the protocol. Isode supports this MIB for all of its server products: M-Switch, M-Vault, M-Box, and M-Store X.400. This MIB provides basic status and network information, which is supplemented by two specific MIBs.
- Mail Monitoring MIB (RFC 2789) defines additional information for a message switch. This includes information on messages queued, and historical information on messages transferred in and out over various channels. This MIB is implemented in Isode's M-Switch product.
- Directory Server Monitoring MIB (RFC 2605) defines additional information for a directory server, and in particular information on the various directory operations performed, so that directory operation rate and performance can be monitored. This MIB is implemented in Isode’s M-Vault product.
MIBs contain much detailed information. This can be understood by reading the MIB definitions Isode’s implementation can be observed using a MIB Browser, that simply connects with SNMP to examine the MIB contents, and interpret them in terms of the MIB definitions. MIBs are defined in a standard format, and a management console will usually import these to help render the information in a useful manner. Isode recommends the Unbrowse MIB browser, available from www.unleashnetworks.com.
Management Console & Web Integration
Isode's SNMP support provides straightforward integration with Management Consoles, such as HP OpenView (below), enabling a network operator to have detailed information on status and performance of the Isode servers. This type of system will enable flexible monitoring, giving a variety of views and information.
While this will be ideal for larger systems, there are some deployments where a simpler cross application and network type of monitoring is needed. A useful way to achieve this is to use a Web to SNMP tool. There are a variety of these available, and one recommended by Isode is Cacti.This can be used to display key performance information enabling "at a glance" checking of the general health of multiple components.
In the image below Cacti is displaying information from M-Switch SMTP, running at Isode's Head Office in Hampton.
This paper has given an overview of Isode's SNMP architecture, and how it can be used to support basic monitoring using a Web interface, and general purpose integration with Management Consoles such as HP Openview.