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Structure of Management Information

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Computer Network & Management


Title: Structure of Management Information (SMI)

Structure of Management Information (SMI):

In the context of network management, for the Structure of Management Information (SMI):

a) Name its three hierarchical layers.

The Structure of Management Information (SMI) standard is responsible for defining the rules for how the Management Information Base (MIB) objects are structured, described and organized. SMI is a data definition language allows dissimilar devices to communicate by ensuring that they use a universal data representation for all management information. SMI is needed to ensure the syntax and semantics of the network management data are well defined and unambiguous.[TCP/IP Guide]

The three hierarchical layers of the Structure of Management Information are the base data types, object-type and module-identity.

b) Explain the function of each layer.

The Base Data Type layer is use in the SYNTAX clause of the OBJECT-TYPE macro that must be present. It defines the abstract data structure corresponding to the object. It includes the following eleven basic data types: INTEGER, Integer32, Unsigned32, OCTET STRING, OBJECT IDENTIFIER, IPaddress, Counter32, Counter64, Gauge32, TimeTicks, and Opaque. Any restriction on size, range or enumerations specified in this SYNTAX clause represents the maximal level of support which makes "protocol sense".[RFC2578]

The OBJECT-TYPE layer is use to specify the data type, status, and the semantics of managed objects. It has basic of five mandatory characteristics namely, OBJECT-NAME, SYNTAX, MAX ACCESS, STATUS, and DESCRIPTION, optionally with OPTIONAL-CHARACTERISTICS. The OBJECT-NAME is obviously. The SYNTAX clause specifies the basic data type of the object. The MAX-ACCESS clause specifies the managed object either can be read-create, read-write, read-only, accessible for notify only, or not accessible. The STATUS clause specifies the object is current, obsolete or deprecated. The DESCRIPTION clause contains a textual definition of the object. [RFC2578][RFC2013]

The MODULE-IDENTITY layer is used to express concisely the semantics of an information module. It groups related object into a Management Information Base (MIB) module. Each MODULE-IDENTITY contains a number of clauses like the LAST-UPDATED clause, ORGANIZATION clause, CONTACT-INFO clause, DESCRIPTION clause and REVISION clause. Theses clauses document the date of last updated, the organization and contact information of the author of the module, and a textual description of the module, and the revision information such as the date of revision and the revision description.[RFC2012][TCP-IP Guide]

c) For each layer, give four examples of defined entities.

Four examples of Base Data Types

1. Integer/Integer32 [RFC2578]

Integer/Integer32 is a 32-bit signed integer in twoÐŽ¦s complement notation, capable of holding a value between ÐŽV2,147,483,648 and +2,147,483,647.

2. Network Address/IpAddress [RFC2578]

It is an IP address, encoded as a 4-byte octet string.

3. TimeTicks [RFC2578]

Time Ticks is a 32-bit unsigned integer that indicates the number of hundredths of seconds since some arbitrary start date. Used for time stamping and to compute elapsed time.

4. Counter64 [RFC2578]

Counter64 is a counter of 64 bits wide, allowing a value between 0 to 18,446,744,073,709,551,615.

Four examples of Object Type

1) Total number of input datagrams successfully delivered

ipInDelivers OBJECT-TYPE

SYNTAX Counter32

MAX-ACCESS read-only

STATUS current


"The total number of input datagrams successfully delivered

to IP user-protocols (including ICMP)."

::= { ip 9 }


2) TCP Maximum number of connections


SYNTAX Integer32 (-1 | 0..2147483647)

MAX-ACCESS read-only

STATUS current


"The limit on the total number of TCP connections the entity

can support. In entities where the maximum number of

connections is dynamic, this object should contain the

value -1."

::= { tcp 4 }


3) UDP Local port number

udpLocalPort OBJECT-TYPE


MAX-ACCESS read-only

STATUS current


"The local port number for this UDP listener."

::= { udpEntry 2 }


4) Object counter on total number of packets counted on this priority level

smonPrioStatsPkts OBJECT-TYPE

SYNTAX Counter32

UNITS "packets"

MAX-ACCESS read-only



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