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<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE chapter SYSTEM "chapter.dtd">
<chapter>
<header>
<copyright>
<year>1997</year><year>2023</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
</legalnotice>
<title>SNMP Introduction</title>
<prepared></prepared>
<responsible></responsible>
<docno></docno>
<approved></approved>
<checked></checked>
<date></date>
<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
are 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>
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