Networking / Beginners

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Simple Network Management Protocol

Once the management station and the managed devices have a common view of the management data (that is, MIB objects) all that remains is to provide a mechanism for the management station to create, write, read, and delete those objects. This is achieved using the Simple Network Management Protocol (SNMP), which, like anything that calls itself "simple," should be taken with a pinch of salt.

MplsBitRate::=TEXTUAL-CONVENTION
DISPLAY-HINT "d"
STATUS current
DESCRIPTION
    "If the value of this object is greater
    than zero, then this represents the
    bandwidth of this MPLS interface (or Label
    Switched Path) in units of '1000 bits per second.'
    The value, when greater than zero,
    represents the bandwidth of this MPLS
    interface (rounded to the nearest 1000)
    in units of 1000 bits per second.
    If the bandwidth of the MPLS interface
    is between ((n * 1000) - 500) and
    ((n * 1000) + 499), the value of this
    object is n, such that n > 0.
    If the value of this object is 0 (zero),
    this means that the traffic over this MPLS
    interface is considered to be best effort."
SYNTAX Unsigned32 (0|1..4294967295)

A textual convention allows multiple MIB modules to import the same construct and meaning without having to redefine it.

SNMP is an application-level protocol that can use any transport mechanism. In practice, it is most often used with UDP using port 161 since that is mandatory for conformance with SNMP standards. Other transport protocols are sometimes used in a misguided attempt to handle some of the security issues. TCP is occasionally chosen when a management application does not handle lost messages.