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<H2>1 SNMP Introduction</H2>

<P>The SNMP development toolkit contains the following parts:


<P>
<UL>

<LI>
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.


</LI>


<LI>
A multi-lingual SNMP manager.


</LI>


<LI>
A MIB compiler, which understands SMIv1 (RFC1155, 1212, and
1215) and SMIv2 (RFC1902, 1903, and 1904).


</LI>


</UL>

<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>
<UL>

<LI>
a description of a Management Information Base (MIB) in
Abstract Syntax Notation One (ASN.1)


</LI>


<LI>
instrumentation functions for the managed objects in the MIB,
written in Erlang.


</LI>


</UL>

<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 <CODE>get-next</CODE> 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.

<A NAME="1.1"><!-- Empty --></A>
<H3>1.1 Scope and Purpose</H3>

<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.
<A NAME="1.2"><!-- Empty --></A>
<H3>1.2 Prerequisites</H3>

<P>The following prerequisites
is required for understanding the material in the SNMP
User's Guide:


<P>
<UL>

<LI>
the basics of the Simple Network Management Protocol
        version 1 (SNMPv1)


</LI>


<LI>
the basics of the community-based Simple Network
        Management Protocol version 2 (SNMPv2c)


</LI>


<LI>
the basics of the Simple Network Management Protocol
        version 3 (SNMPv3)


</LI>


<LI>
the knowledge of defining MIBs using SMIv1 and SMIv2


</LI>


<LI>
familiarity with the Erlang system and Erlang programming


</LI>


</UL>

<P>The tool requires Erlang release 4.7 or later.

<A NAME="1.3"><!-- Empty --></A>
<H3>1.3 Definitions</H3>

<P>The following definitions are used in the SNMP User's Guide.



<P>
<DL>

<DT>
MIB


</DT>

<DD>
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.


</DD>

<DT>
SMI


</DT>

<DD>
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).


</DD>

<DT>
ASN.1


</DT>

<DD>
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.


</DD>

<DT>
Managed object


</DT>

<DD>
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:

        
<UL>

<LI>
<STRONG>scalar variables</STRONG>, which have only one instance
         per context. They have single values, not multiple values like
         vectors or structures.
         
         
</LI>


<LI>
<STRONG>tables</STRONG>, which can grow dynamically.
         
         
</LI>


<LI>
a <STRONG>table element</STRONG>, which is a special type of
         scalar variable.
        
</LI>


</UL>



</DD>

<DT>
Operations


</DT>

<DD>
SNMP relies on the three basic operations: get (object),
set (object, value) and get-next (object).


</DD>

<DT>
Instrumentation function


</DT>

<DD>
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.
</DD>

<DT>
Manager
</DT>

<DD>
A manager generates commands and receives notifications 
        from agents. There usually are only a few managers in a system.
</DD>

<DT>
Agent
</DT>

<DD>
An agent responds to commands from the manager, and sends
        notification to the manager. There are potentially many agents 
        in a systrem.
</DD>

</DL>
<A NAME="1.4"><!-- Empty --></A>
<H3>1.4 About This Manual</H3>

<P>In addition to this introductory chapter, the SNMP User's Guide
contains the following chapters:


<P>
<UL>

<LI>
Chapter 2: &#34;Functional Description&#34; describes the features
        and operation of the SNMP development toolkit. It includes
        topics on Subagents and MIB loading, Internal MIBs, and Traps.


</LI>


<LI>
Chapter 3: &#34;The MIB Compiler&#34; describes the features and the
        operation of the MIB compiler.


</LI>


<LI>
Chapter 4: &#34;Running the application&#34; describes how to start and
        configure the application. Topics on how to debug the application 
        are also included.


</LI>


<LI>
Chapter 5: &#34;Definition of Agent Configuration Files&#34; is a
        reference chapter, which contains more detailed information about
        the agent configuration files.


</LI>


<LI>
Chapter 6: &#34;Definition of Manager Configuration Files&#34; is a
        reference chapter, which contains more detailed information about
        the manager configuration files.


</LI>


<LI>
Chapter 7: &#34;Agent Implementation Example&#34; describes how an MIB
        can be implemented with the SNMP Development Toolkit. 
        Implementation examples are included.


</LI>


<LI>
Chapter 8: &#34;Instrumentation Functions&#34; describes how
        instrumentation functions should be defined in Erlang for the
        different operations.


</LI>


<LI>
Chapter 9: &#34;Definition of Instrumentation Functions&#34; is a
        reference chapter which contains more detailed information
        about the instrumentation functions.


</LI>


<LI>
Chapter 10: &#34;Definition of Agent Net if&#34; is a reference chapter,
        which describes the Agent Net if function in detail.


</LI>


<LI>
Chapter 11: &#34;Definition of Manager Net if&#34; is a reference chapter,
        which describes the Manager Net if function in detail.


</LI>


<LI>
Chapter 12: &#34;Advanced Agent Topics&#34; describes subagents, agent
        semantics, audit trail logging, and the consideration of
        distributed tables.


</LI>


<LI>
Appendix A describes the conversion of SNMPv2 to SNMPv1
        error messages.


</LI>


<LI>
Appendix B contains the RFC1903 text on <CODE>RowStatus</CODE>.


</LI>


</UL>
<A NAME="1.5"><!-- Empty --></A>
<H3>1.5 Where to Find More Information</H3>

<P>Refer to the following documentation for more information about
SNMP and about the Erlang/OTP development system:


<P>
<UL>

<LI>
Marshall T. Rose (1991), &#34;The Simple Book - An
        Introduction to Internet Management&#34;, Prentice-Hall


</LI>


<LI>
Evan McGinnis and David Perkins (1997), &#34;Understanding SNMP
MIBs&#34;, Prentice-Hall


</LI>


<LI>
RFC1155, 1157, 1212 and 1215 (SNMPv1)


</LI>


<LI>
RFC1901-1907 (SNMPv2c)


</LI>


<LI>
RFC1908, 2089 (coexistence between SNMPv1 and SNMPv2)


</LI>


<LI>
RFC2271, RFC2273 (SNMP std MIBs)


</LI>


<LI>
the Mnesia User's Guide


</LI>


<LI>
the Erlang 4.4 Extensions User's Guide


</LI>


<LI>
the Reference Manual


</LI>


<LI>
the Erlang Embedded Systems User's Guide


</LI>


<LI>
the System Architecture Support Libraries (SASL) User's
        Guide


</LI>


<LI>
the Installation Guide


</LI>


<LI>
the Asn1 User's Guide


</LI>


<LI>
Concurrent Programming in Erlang, 2nd Edition (1996),
        Prentice-Hall, ISBN 0-13-508301-X.


</LI>


</UL>
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