5' SNMP MIB Management Information Base

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5. SNMP MIB(Management Information Base)

• 2003.12.30
• Hongseok Jang
• (Jwang_at_iat.chonnam.ac.kr)

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contents

• 0.MIB (Management Information Base)
• 1.Structure of Management Information
• 2.MIB-?
• 3.Practical Issues
• 4. Summary

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0.MIB

• Management Information Base
• RFC1156
• TCP/IP and OSI environments
• Database containing information about the
  elements to be managed
• Each resource to be managed is represented by an
  object
• Structured collection of such objects

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1.Structure of Management Information

• SMI (Structure of Management Information)
• RFC1155
• SMI defines MIB
• Simplicity and extensibility within the MIB
• MIB can store only simple data type
• - scalars and two-dimensional array of scalars
• Standardized techniques
• Lower levels are defined by other organizations
• Some branches define vendor-specific objects

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1.Structure of Management Information

• 1. MIB Structure
• ASN.1 type OBJECT IDENTIFIER
• Internet OBJECT IDENTIFIER iso org(3) dod(6)
  1
• Internet node has the object identifier value of
  1.3.6.1
• Under the internet node
• Directory(1)
• Mgmt(2)
• Experimental(3)
• Private(4)

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1.Structure of Management Information
Figure 5.1 MIB-? Object Groups
Iso(1)
org(3)
dod(6)
internet(1)
directory(1)
mgmt(2)
mib-2(1)
experimental(3)
system(1)
interfaces(2)

private(4)
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1.Structure of Management Information

• 2. Object Syntax
• Defined using ASN.1
• Universal Types
• Primitive type INTEGER, OCTET STRING, NULL,
  OBJECT IDENTIFIER
• Constructor type SEQUENCE, SEQUENCE OF
• Application Types
• NetworkAddress, IpAddress, Counter
• Gauge, TimeTicks, Opaque

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2.MIB-?

• RFC1213
• Superset of MIB-?
• The group organization is a convenience in
  organizing managed objects
• system, interfaces, at, ip, icmp, tcp, udp, egp
• transmission, snmp group
• ACCESS characteristic RO, RW, WO, NA
• STATUS M, D

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2.MIB-?

• System Group
• general information about the managed system
• sysObjectID system manufacturer
• sysServices protocol layer the device services
  using the formula 2L-1 L is protocol layer num
• Eg. router operates at layer 3 return a value 4
  (23-1)
• Eg. Host running transportation and application
  layer services return a value 72 (27-1)
  (24-1)
• sysUptime period length the system has been
  operational
• sysName, sysLocation, sysContact, sysDescr

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2.MIB-?

• Interfaces Group
• generic information about the physical interfaces
  of the entity
• including configuration information and
  statistics on the events occurring at each
  interface
• mandatory of all systems
• ifNumber records the total number of network
  interfaces
• ifTable all information about all the
  interfaces of an entity

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2.MIB-?

• ifEntry a row information about a specific
  interface
• ifIndex an integer an index for the array of
  ifEntry
• Value 1 lt ifIndex lt ifNumber
• ifSpeed a gauge that tracks the current
  interface speed in bits per second
• ifInUcastPkts rate of input unicast packets
• ifOutNUcastPkts rate of output nonunicast
  packets
• ifType, ifPhysAddress, ifInErrors, ifInDiscards,
  

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2.MIB-?

• Address-Translation Group
• Mapping from a network address to a physical
  address
• Deprecated in MIB-?
• In MIB-?, address-translation information is
  provided within each network protocol group
• IP Group
• Information relevant to the implementation and
  operation of IP at a node
• useful for performance and fault monitoring
• ipAddrTable information relevant to the IP
  addresses assigned to the entity

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2.MIB-?

• ipRouteTable information used for internet
  routing
• ipNetToMediaTable enable to tell the mapping of
  IP addresses to another protocol address
• ICMP Group ICMP messages
• TCP Group TCP traffic statistics
• UDP Group UDP traffic statistics
• EGP Group Exterior Gateway Protocol Statistics
• Transmission Group
• SNMP Group SNMP traffic statistics

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2.MIB-?

• The Scope of MIB-?
• limited by the objects available to manage
• support network monitoring and management from
  the transport layer down

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3.Practical Issues

• Measurement
• Examined by a group of ATT researchers
• (Network World, 1991)
• First experiment
• Test SNMP-managed bridge products(Mier1991a)
• Objective the accuracy of the data and the
  interoperability of the agent
• Second experiment
• Test SNMP-managed IP router products(Mier1991b)
• LANs were connected by a router
• SNMP agent is a useful tool for detecting faults

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3.Practical Issues

• Private MIBs
• accommodate growth and provide flexibility for
  adding new objects
• added to the private subtree
• The potential for difficulty arises when the two
  (management station/agent station) are from
  different vendors
• most vendors supply both a text version and a
  formal description of their MIB extensions
• currently used three different formats to define
  private MIBs (RFC1155, RFC1212, OSI SMI spec.)

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3.Practical Issues

• Limitations of MIB Objects
• Fundamental limitations
• limited by the capability of the
  network-management protocol and by the objects
  used to represent the environment to be managed
• MIB-? is designed to minimize the burden on
  systems and networks
• indeed limit the ability to monitor and control a
  network

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Summary

• MIB consists of a collection of objects organized
  into groups
• Represented using ASN.1
• Simplicity and extensibility
• MIB can store only simple data type
• Objects hold values that represent managed
  resources
• MIB-? is a superset of MIB-?, with some
  additional objects and groups