McDATA 316095-B21 - StorageWorks Edge Switch 2/24 Manual page 494

SNMP Framework MIB
F
SnmpMessageProcessingModel
E/OS SNMP Support Manual
F-4
• Values greater than 255 are allocated to enterprise-specific
Security Models. An enterprise-specific securityModel value is
defined to be: enterpriseID * 256 + security model within
enterprise.
For example, the fourth Security Model defined by the enterprise
whose enterpriseID is 1 would be 260. The eight bits allow a
maximum of 255 (256-1 reserved) standards based Security Models.
Similarly, they allow a maximum of 255 Security Models per
enterprise.
It is believed that the assignment of new securityModel values will be
rare in practice because the larger the number of simultaneously
utilized Security Models, the larger the chance that interoperability
will suffer. Consequently, it is believed that such a range will be
sufficient. In the unlikely event that the standards committee finds
this number to be insufficient over time, an enterprise number can be
allocated to obtain an additional 255 possible values.
Note that the most significant bit must be zero; hence, there are 23
bits allocated for various Organizations to design and define
non-standard securityModels. This limits the ability to define new
proprietary implementations of Security Models to the first 8,388,608
enterprises.
It is worthwhile to note that, in its encoded form, the securityModel
value will normally require only a single byte since, in practice, the
leftmost bits will be zero for most messages and sign extension is
suppressed by the encoding rules.
As of this writing, there are several values of securityModel defined
for use with SNMP or reserved for use with supporting MIB Objects.
They are as follows:
0 reserved for 'any'
1 reserved for SNMPv1
2 reserved for SNMPv2c
3 User-Based Security Model (USM)
INTEGER(0..2147483647)
Syntax
current
Status