SNMP Versions

The System Management Agent supports three SNMP protocols. Along with their associated RFCs, these protocols are:

SNMP v1

SNMP v1 is defined in RFC 1155 and 1157 at http://www.ietf.org/rfc/rfc1155.txt and http://www.ietf.org/rfc/rfc1157.txt

SNMP v2c

SNMP v2c is defined in RFC 1901 at http://www.ietf.org/rfc/rfc1901.txt

SNMP v3

SNMP v3 is defined in RFC 2570 at http://www.ietf.org/rfc/rfc2570.txt

These versions of SNMP supported by the System Management Agent can co-exist following the guidelines laid down in RFC 3584 at http://www.ietf.org/rfc/rfc3584.txt.

Some security models and other instances described in this manual do not support all versions of SNMP. Restrictions regarding which version of SNMP you can use are indicated in this book and in the relevant man pages. Restrictions are due in part to the enhanced packet structure of SNMPv3. The SNMPv3 packet structure is shown in Figure 1–1.

Figure 1–1 SNMPv3 Packet Structure

The packets outlined in Figure 1–1 are:

msgVersion

The SNMP version of the packet. Possible values are 1, 2, or, in the case of SNMPv3, 3.

msgID

Used to coordinate request and response messages between the manager and the agent. The msgID in a response must be the same as the msgID in a request.

msgMaxSize

Conveys the maximum size of a message that the sender can accept from another SNMP engine.

msgFlags

A single octet to indicate how the message is to be processed. For more information, see Where VACM Security Information Is Contained.

msgSecurityModel

Specifies the security model used to generate the message. For more information, see Where VACM Security Information Is Contained.

msgSecurityParameters

An octet string containing data about the security model. For more information, see Where VACM Security Information Is Contained.

scopedPDU

Contains the normal Protocol Data Unit (PDU) and information for identifying the administratively unique context for processing the PDU. For more information, see Where VACM Security Information Is Contained.