SNMPv3 -- User Security Model
By Eric Davis, April 09, 2004
This is the first of two articles describing the security features of the SNMP version 3 protocol. The SNMPv3 RFCs describe a new framework that is used for defining the relationships between the SNMP versions 1, 2, and 3 specifications. This framework is partitioned in a modular fashion and is heavily based on previous work (i.e., SNMPv1, SNMPv2c, SNMPv2u, and SNMPv2*).
Figure 1: SNMPv3 packet format
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/|\ | msgVersion |
| |-----------------------|
| | msgID |
| |-----------------------| USM Security Parameters
| | msgMaxSize |
| |-----------------------| ------------------------------
| | msgFlags | /| msgAuthoritativeEngineID |
scope of |-----------------------| / |----------------------------|
authentication | msgSecurityModel |/ | msgAuthoritativeEngineBoots|
| |-----------------------| |----------------------------|
| | | | msgAuthoritativeEngineTime |
| | msgSecurityParameters | |----------------------------|
| | | | msgUserName |
| |-----------------------| |----------------------------|
| /|\ | |\ | msgAuthenticationParameters|
| | | | \ |----------------------------|
| | | | \| msgPrivacyParameters |
| scope of | scopedPDU | ------------------------------
| encryption | |
| | | |
| | | |
| | | |
\|/ \|/ | |
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