1 Kyung Hee University Prof. Choong Seon HONG SNMP Management Information.

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Kyung Hee University

Prof. Choong Seon HONG

SNMP Management InformationSNMP Management Information

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SNMP Management InformationSNMP Management Information

Database contains information about the elements to be managed : MIB

Each resource to be managed is represented by object

MIB : structured collection of such object having the form of tree

Structure of Management Information (SMI)

Specified in RFC 1155

Providing a standardized technique for defining the structure of a particular MIB

Providing a standardized technique for defining individual objects, including the syntax and the value of each object

Providing a standardized technique for encoding object values

SMI Data Type Additions To Structure of Management Information Version 2 (SMIv2) And Structure of Management Information Version 1 (SMIv1) : draft-perkins-smi-addition-00.txt

The new data types are Integer64, Unsigned64, Float, Double, and DiscUnion (discriminated union)

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Defining objectsDefining objects

MIB (Management Information Base)

a precise definition of the information accessible through a network management protocol

each device must use the format for displaying information that is defined by the MIB

RFC 1052 define an extended MIB for use with SNMP and CMIS/CMIP is no longer realistic

RFC 1065: “Structure and Identification of Management Information for TCP/IP based Internets (SMI)”

describe the syntax and type of information available in the MIB for TCP/IP networks

RFC 1066 use the rules of the SMI present the first version of the MIB for TCP/IP known as MIB-I

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Defining objectsDefining objects

RFC 1155 (SMI)

RFC 1065 later was adopted by the IAB as a full standard four primitive data type

– INTEGER• 32bit value in two’s complement representation• -2147483648 ~ 2147483647

– OCTET STRING• zero or more octets• 0 ~ 255• represent a text string

– OBJECT IDENTIFIER• a sequence of integers• traverse a hierarchical MIB tree

– NULL

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MIB StructureMIB Structure

Leaf objects of the tree to be actual managed objects to represent

some resource, activity, or related information

Object identifier : a unique identifier for particular object type

Serving as name the object

internet OBJECT IDENTIFIER :: = { iso (1) org(3) dod (6) 1}

therefore, internet node’s object ID : 1.3.6.1

four nodes under the internet node

directory mgmt ----> mib-1, mib-2 experimental private

MIB tree (see fig. 5.1)

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Object SyntaxObject Syntax

Universal types

UNIVERSAL class of ASN.1 consisting of application-independent data types for defining MIB objects

integer (UNIVERSAL 2) octetstring (UNIVERSAL 4) null (UNIVERSAL 5) object identifier (UNIVERSAL 6) sequence, sequence-of (UNIVERSAL 16)

Object ID consisting of sequence of integers

for example : object ID for tcpConnTable : 1.3.6.1.2.1.6.13

iso org dod internet mgmt mib-2 tcp tcpConnTable

1 3 6 1 2 1 6 13

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Object SyntaxObject Syntax

Application-wide Types

APPLICATION class of ASN.1 consisting of data types that are relevant to a particular application

application wide data types defined in RFC 1155

networkaddress : defined using CHOICE construct, ex) IP Address ipaddress : 32-bit address using the format specified in IP counter : non-negative integer that may be increamented but not decremen

ted with maximum value of 2 23 - 1. If the counter reaches its maximum, it wraps around and starts from zero

gauge : non-negative integer that may increase or decrease with maximum value of 2 23 -1. If the counter reaches its maximum, it remains its value.

Timeticks : counting the time since some epoch in second (relative timer to some event such as startup or reinitialization)

opaque : supporting the capability to pass arbitrary data : specifying octets of binary information, no limit to maximum number of octets : encoded as OCTET STRING

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Macro object definitionMacro object definition

Object : having a type (syntactic description) and value

To extend ASN.1 to define new types and their values

Macro definition : specifying the syntax of a set of related types

Macro instance : an instance generated from a specific macro defi

nition

Macro instance value : representing a specific entity with a specifi

c value

Macro used for the SNMP MIBs : RFC1155 for MIB-I, RC 1212 (conc

ise MIB definitions) for MIB-II (Fig. 5.3)

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MIB Object Definition FormatMIB Object Definition Format

SYNTAX : ASN.1 syntax for object’s abstract data structure

ACCESS : defining the way in which an instance of the object may be accessed, via SNMP or another protocol - read-only or read-write or write-only or not-accessible

STATUS : current implementation status - mandatory or optional, or deprecated or obsolete

DescrPart : a textual description of the semantics of the object type (optional)

ReferPart : a textual cross-reference to an object defined in some other MIB module (optional)

IndexPart : used in defining tables

DefValPart : defining an acceptable default value that may be used when an object instance is created (optional)

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MIB Object Definition FormatMIB Object Definition Format OBJECT-TYPE macro (see Fig. 5.3)

A formal template for defining the objects that will consists MIB

ASN.1 module syntax (refer Fig. 5.4)

module : containing specific RFC

Structure of Management Information (RFC 1155, see Fig. 5.4)

An Example of an Object Type Definition (Figure 5.5)

<< module>> DEFINITIONS :: = BEGIN<<linkage>><<declarations>>

END

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Defining TablesDefining Tables

The SMI supports only one form of structuring of data: a simple tw

o-dimensional table with scalar-valued entries.

Definition of tables involves the use of the sequence and sequenc

e-of ASN.1 types and the IndexPart of the OBJECT-TYPE macro.

Object type tcpConnTable (Figure 5.7) (See APPENDIX 5A)

consisting of a SEQUENCE OF TcpConnEntry

each row consists of a SEQUENCE

MIB specification of TCP connection table (RFC 1213)

See Figure 5.6

The overall table consists of a SEQUENCE OF TcpConnEntry

Each row consists of a SEQUENCE that includes five scalar elements

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TCP Entity State SummaryTCP Entity State Summary

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TCP Entity State Summary (cont’d)TCP Entity State Summary (cont’d)

Server

Client

Unusual

Input / Output

Now connection is closed in one direction.Now connection is closed in one direction.

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Defining TablesDefining Tables

The entire table represents a single instance of the object type tcpConnTable.

Each row is an instance of the object type tcpConnEntry.

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Private MIBsPrivate MIBs

MIB has been designed to accommodate growth and to provide flexibility for adding new objects.

Private extensions can be added to the private subtree (Figure 5.1)

The management station must be loaded with the private MIB structure

The potential for difficulty arises when the two are from different vendors

Most vendors supply both a text version and a formal description of their MIB extensions

But, vendors can use different formats as follows

- The original SNMP SMI specification, RFC 1155

- The newer Concise MIB Format, RFC 1212

- The OSI SMI specification

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SNMP V2SNMP V2

SNMPv2

Additional types

Integer32 Counter32 Gauge32 Unsigned32 Counter64

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SNMP OverviewSNMP Overview

RFC 1156

allow for expansion of the MIB for vendor specific enhancement

RFC 1158

propose a second MIB (MIB-II) extend the information base defined in MIB-I Note: most network devices have software agent that support MIB-II and their own

private extensions

Each MIB would focus on a specific technology

RFC 1743: IEEE 802.5 Token Ring Interface type MIB RFC 1757: Remote Network Monitoring MIB (RMON) RFC 1513: FDDI Interface type MIB RFC 1493: Bridge MIB

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Object Identifier

ISO ASN.1 (Abstract Syntax Notation One) Syntax

a subset of ASN.1 defines the syntax for the MIB use the tree architecture to organize all available information

– labeled node– object identifier (OID) and sort text description

Subtree

Root

Node (2)Node (1)

Node (1)

Object (1)

Node (2)

Node A (1)Object (2)

Object A (1)

OID: 1.2.1.1 or {node A 1}

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Traversal of the MIB tree

root node– itu-t (0), administered by the ITU-T– iso (1), administered by the ISO– joint-iso-itu-t (2), jointly administered by ISO and ITU-T

• internet: OID= 1.3.6.1 or {iso org(3) dod(6), 1}

ITU-T(0) ISO(1) joint-ISO-ITU-T (2)

…. org(3) …..

….. dod(6) …..

….. internet (1) …..

directory(1) …… mgmt(2) …. Experimental(3) private(4)

mib(1) enterprises(1)

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SNMP OverviewSNMP Overview directory (1)

– reserved for future use mgmt(2)

– MIB-I originally assigned OID 1.3.6.1.2.1 or {mib 1}– MIB-I has been superseded by MIB-II– system(1): network device operating system– interfaces(2): network interface specific– address translation(3): address mappings– ip(4): Internet protocol specific– icmp(5): ICMP specific– tcp(6): transmission protocol specific– udp(7): user datagram protocol specific– egp(8): exterior gateway protocol specific– cmot(9): CMIP on TCP specific– transmission(10): transmission media specific– snmp(11): SNMP specific

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experimental (3)– experimental protocols and MIB development intended to enter the standards tr

ack private(4)

– used to specify objects defined unilaterally– enterprises(1) or {private 1}

• an organization that has registered its own specific extensions to the MIB• vendor-specific MIBs are found• OID (1.3.6.1.4.1)

OIDs represent each manageable object with a unique sequence of numbers and names

SNMP uses the number as an abbreviated form of the name – to make requests for data values– to identify each response that carries the values

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SNMP OverviewSNMP OverviewThe five SNMPv1message types (RFC1157)

Get-Request: retrieve information from device Get-Response: agent responds to the Get-Request Get-Next-Request: ask for the next specific object Set-Request: for remote configuration parameter Trap: an unsolicited message

Host

MS-DOS Router

Terminal server Device

Data Network

station

Managing host

agentagentagent

agentagent

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SNMP OverviewSNMP OverviewFormat of SNMP

SNMP

ISO presentation

ISO session

UDP

IP

ISO data link

Physical

Layer 7

Layer 6

Layer 5

Layer 4

Layer 3

Layer 2

Layer 1

Version Community PDUtype

Request ID

0 0 Name X Value X ……..


Request ID

Errorstatus

Errorindex

Name X Value X ……...

Get-Request, Get-Next-Request, Set-Request

Get-Response


Enterprise Agentaddr

Generic trap

Specific trap

Time Name X Value X

Trap

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SNMP trap

an unsolicited message an agent sends to a station inform the server about the occurrence of specific event seven types of SNMP traps (MIB-II)

– coldstart of a system: reinitialing itself such that its configuration or protocol has changed

– warmstart of a system: reinitialing itself such that its configuration or protocol has not changed

– link down: a specific link has failed

stationDevice

agent

Data Network

Link failure

Trap: interface #2, link down

Managing host

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SNMP OverviewSNMP Overview– link up: a specific link has come up– failure of authentication: a request does not provide proper authentication– EGP (Exterior Gateway Protocol) neighbor loss

• EGP is a reachability protocol used between data networks– enterprise specific

• a vendor to provide additional functionality that complements the generic traps

security

community string– station sends a particular password with each message– the password is referred to as the SNMP community string

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SNMP OverviewSNMP Overview Examples of an SNMP query

stationDevice

agent

Data NetworkManaging host

stationDevice

agent

Managing host Communitystring: blee

SNMP Get, community string = blee

Communication string validated, SNMP Get-Response

SNMP Trap, authentication failure

Community string: blee

SNMP Set, community string= public

1 Kyung Hee University Prof. Choong Seon HONG SNMP Management Information.

Documents

object mib

mib rfc

mib objects

particular mib

object identifier universal

extended mib

particular object type

private mib tree