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<year>1997</year><year>2013</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
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Licensed under the Apache License, Version 2.0 (the "License");
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<title>SNMP Introduction</title>
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<rev></rev>
<file>snmp_intro.xml</file>
</header>
<p>The SNMP development toolkit contains the following parts:
</p>
<list type="bulleted">
<item>An Extensible multi-lingual SNMP agent, which understands SNMPv1
(RFC1157), SNMPv2c (RFC1901, 1905, 1906 and 1907), SNMPv3
(RFC2271, 2272, 2273, 2274 and 2275), or any combination of
these protocols.
</item>
<item>A multi-lingual SNMP manager.
</item>
<item>A MIB compiler, which understands SMIv1 (RFC1155, 1212, and
1215) and SMIv2 (RFC1902, 1903, and 1904).
</item>
</list>
<p>The SNMP development tool provides an environment for
rapid agent/manager prototyping and construction. With the
following information provided, this tool is used to set up a
running multi-lingual SNMP agent/manager:
</p>
<list type="bulleted">
<item>a description of a Management Information Base (MIB) in
Abstract Syntax Notation One (ASN.1)
</item>
<item>instrumentation functions for the managed objects in the MIB,
written in Erlang.
</item>
</list>
<p>The advantage of using an extensible (agent/manager) toolkit is to
remove details such as type-checking, access rights, Protocol Data Unit
(PDU), encoding, decoding, and trap distribution from the
programmer, who only has to write the instrumentation functions,
which implement the MIBs. The <c>get-next</c> function only
has to be implemented for tables, and not for every variable in
the global naming tree. This information can be deduced from the
ASN.1 file.
</p>
<section>
<title>Scope and Purpose</title>
<p>This manual describes the SNMP development tool,
as a component of the Erlang/Open Telecom Platform development
environment. It is assumed that the reader is familiar with the
Erlang Development Environment, which is described in a separate
User's Guide.</p>
</section>
<section>
<title>Prerequisites</title>
<p>The following prerequisites
is required for understanding the material in the SNMP
User's Guide:
</p>
<list type="bulleted">
<item>the basics of the Simple Network Management Protocol
version 1 (SNMPv1)
</item>
<item>the basics of the community-based Simple Network
Management Protocol version 2 (SNMPv2c)
</item>
<item>the basics of the Simple Network Management Protocol
version 3 (SNMPv3)
</item>
<item>the knowledge of defining MIBs using SMIv1 and SMIv2
</item>
<item>familiarity with the Erlang system and Erlang programming
</item>
</list>
<p>The tool requires Erlang release 4.7 or later.
</p>
</section>
<section>
<title>Definitions</title>
<p>The following definitions are used in the SNMP User's Guide.
</p>
<taglist>
<tag>MIB</tag>
<item>The conceptual repository for management information is
called the Management Information Base (MIB). It does not
hold any data, merely a definition of what
data can be accessed. A definition of an MIB is a
description of a collection of managed objects.
</item>
<tag>SMI</tag>
<item>The MIB is specified in an adapted subset of the Abstract
Syntax Notation One (ASN.1) language. This adapted subset is
called the Structure of Management Information (SMI).
</item>
<tag>ASN.1</tag>
<item>ASN.1 is used in two different ways in SNMP. The SMI is
based on ASN.1, and the messages in the protocol are defined by
using ASN.1.
</item>
<tag>Managed object</tag>
<item>
<p>A resource to be managed is represented by a managed
object, which resides in the MIB. In an SNMP MIB, the managed
objects are either:</p>
<list type="bulleted">
<item><em>scalar variables</em>, which have only one instance
per context. They have single values, not multiple values like
vectors or structures.
</item>
<item><em>tables</em>, which can grow dynamically.
</item>
<item>a <em>table element</em>, which is a special type of
scalar variable.</item>
</list>
</item>
<tag>Operations</tag>
<item>SNMP relies on the three basic operations: get (object),
set (object, value) and get-next (object).
</item>
<tag>Instrumentation function</tag>
<item>An instrumentation function is associated with each
managed object. This is the function, which actually implements
the operations and will be called by the agent when it receives
a request from the management station.</item>
<tag>Manager</tag>
<item>A manager generates commands and receives notifications
from agents. There usually are only a few managers in a system.</item>
<tag>Agent</tag>
<item>An agent responds to commands from the manager, and sends
notification to the manager. There are potentially many agents
in a system.</item>
</taglist>
</section>
<section>
<title>About This Manual</title>
<p>In addition to this introductory chapter, the SNMP User's Guide
contains the following chapters:
</p>
<list type="bulleted">
<item>Chapter 2: "Functional Description" describes the features
and operation of the SNMP development toolkit. It includes
topics on Sub-agents and MIB loading, Internal MIBs, and Traps.
</item>
<item>Chapter 3: "The MIB Compiler" describes the features and the
operation of the MIB compiler.
</item>
<item>Chapter 4: "Running the application" describes how to start and
configure the application. Topics on how to debug the application
are also included.
</item>
<item>Chapter 5: "Definition of Agent Configuration Files" is a
reference chapter, which contains more detailed information about
the agent configuration files.
</item>
<item>Chapter 6: "Definition of Manager Configuration Files" is a
reference chapter, which contains more detailed information about
the manager configuration files.
</item>
<item>Chapter 7: "Agent Implementation Example" describes how an MIB
can be implemented with the SNMP Development Toolkit.
Implementation examples are included.
</item>
<item>Chapter 8: "Instrumentation Functions" describes how
instrumentation functions should be defined in Erlang for the
different operations.
</item>
<item>Chapter 9: "Definition of Instrumentation Functions" is a
reference chapter which contains more detailed information
about the instrumentation functions.
</item>
<item>Chapter 10: "Definition of Agent Net if" is a reference chapter,
which describes the Agent Net if function in detail.
</item>
<item>Chapter 11: "Definition of Manager Net if" is a reference chapter,
which describes the Manager Net if function in detail.
</item>
<item>Chapter 12: "Advanced Agent Topics" describes sub-agents, agent
semantics, audit trail logging, and the consideration of
distributed tables.
</item>
<item>Appendix A describes the conversion of SNMPv2 to SNMPv1
error messages.
</item>
<item>Appendix B contains the RFC1903 text on <c>RowStatus</c>.
</item>
</list>
</section>
<section>
<title>Where to Find More Information</title>
<p>Refer to the following documentation for more information about
SNMP and about the Erlang/OTP development system:
</p>
<list type="bulleted">
<item>Marshall T. Rose (1991), "The Simple Book - An
Introduction to Internet Management", Prentice-Hall
</item>
<item>Evan McGinnis and David Perkins (1997), "Understanding SNMP
MIBs", Prentice-Hall
</item>
<item>RFC1155, 1157, 1212 and 1215 (SNMPv1)
</item>
<item>RFC1901-1907 (SNMPv2c)
</item>
<item>RFC1908, 2089 (coexistence between SNMPv1 and SNMPv2)
</item>
<item>RFC2271, RFC2273 (SNMP std MIBs)
</item>
<item>the Mnesia User's Guide
</item>
<item>the Erlang 4.4 Extensions User's Guide
</item>
<item>the Reference Manual
</item>
<item>the Erlang Embedded Systems User's Guide
</item>
<item>the System Architecture Support Libraries (SASL) User's
Guide
</item>
<item>the Installation Guide
</item>
<item>the Asn1 User's Guide
</item>
<item>Concurrent Programming in Erlang, 2nd Edition (1996),
Prentice-Hall, ISBN 0-13-508301-X.
</item>
</list>
</section>
</chapter>
