Cisco Systems Dial NMS manual What is SNMPv1?, SNMPv1 and ASN1 Data Types

Overview of Basic SNMP Building Blocks

What is SNMPv1?

SNMP must account for and adjust to incompatibilities between managed devices. Different computers use different data-representation techniques, which can compromise the ability of SNMP to exchange information between managed devices.

What is SNMPv1?

SNMPv1 is the initial implementation of the SNMP protocol and is described in RFC 1157 (http://www.ietf.org/rfc/rfc1157).

SNMPv1:

•Functions within the specifications of the Structure of Management Information (SMI).

•Operates over protocols such as User Datagram Protocol (UDP), Internet Protocol (IP), OSI Connectionless Network Service (CLNS), AppleTalk Datagram-Delivery Protocol (DDP), and Novell Internet Packet Exchange (IPX).

•Is the de facto network-management protocol in the Internet community.

The SMI defines the rules for describing management information by using Abstract Syntax Notation One (ASN.1). The SNMPv1 SMI is defined in RFC 1155 (http://www.ietf.org/rfc/rfc1155). The SMI makes three specifications:

•ASN.1 data types

•SMI-specific data types

•SNMP MIB tables

SNMPv1 and ASN1 Data Types

The SNMPv1 SMI specifies that all managed objects must have a subset of associated ASN.1 data types. Three ASN.1 data types are required:

•Name—Serves as the object identifier (object ID).

•Syntax—Defines the data type of the object (for example, integer or string). The SMI uses a subset of the ASN.1 syntax definitions.

•Encoding—Describes how information associated with a managed object is formatted as a series of data items for transmission over the network.

SNMPv1 and SMI-Specific Data Types

The SNMPv1 SMI specifies the use of many SMI-specific data types, which are divided into two categories:

•Simple data types—Including these three types:

`Integers—A signed integer in the range of -2,147,483,648 to 2,147,483,647.

`Octet strings—Ordered sequences of zero to 65,535 octets.

`Object IDs— Come from the set of all object identifiers allocated according to the rules specified in ASN.1.

Basic Dial NMS Implementation Guide

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