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

2. 2 Kyung Hee University SNMP 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.txtdraft- perkins-smi-addition-00.txt l The new data types are Integer64, Unsigned64, Float, Double, and DiscUnion (discriminated union)

3. 3 Kyung Hee University Defining 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 l define an extended MIB for use with SNMP and CMIS/CMIP l is no longer realistic RFC 1065: “Structure and Identification of Management Information for TCP/IP based Internets (SMI)” l describe the syntax and type of information available in the MIB for TCP/IP networks RFC 1066 l use the rules of the SMI l present the first version of the MIB for TCP/IP l known as MIB-I

4. 4 Kyung Hee University Defining objects RFC 1155 (SMI) l RFC 1065 later was adopted by the IAB as a full standard l 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

5. 5 Kyung Hee University MIB 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 l directory l mgmt ----> mib-1, mib-2 l experimental l private  MIB tree (see fig. 5.1)

6. 6 Kyung Hee University Object Syntax  Universal types UNIVERSAL class of ASN.1 consisting of application-independent data types for defining MIB objects l integer (UNIVERSAL 2) l octetstring (UNIVERSAL 4) l null (UNIVERSAL 5) l object identifier (UNIVERSAL 6) l sequence, sequence-of (UNIVERSAL 16) Object ID consisting of sequence of integers l 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

7. 7 Kyung Hee University Object 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 l networkaddress : defined using CHOICE construct, ex) IP Address l ipaddress : 32-bit address using the format specified in IP l counter : non-negative integer that may be increamented but not decremented with maximum value of 2 23 - 1. If the counter reaches its maximum, it wraps around and starts from zero l 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. l Timeticks : counting the time since some epoch in second (relative timer to some event such as startup or reinitialization) l opaque : supporting the capability to pass arbitrary data : specifying octets of binary information, no limit to maximum number of octets : encoded as OCTET STRING

8. 8 Kyung Hee University Macro 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 definition  Macro instance value : representing a specific entity with a specific value  Macro used for the SNMP MIBs : RFC1155 for MIB-I, RC 1212 (concise MIB definitions) for MIB-II (Fig. 5.3)

9. 9 Kyung Hee University MIB 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)

10. 10 Kyung Hee University MIB 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) > DEFINITIONS :: = BEGIN > END

11. 11 Kyung Hee University Defining Tables  The SMI supports only one form of structuring of data: a simple two-dimensional table with scalar-valued entries.  Definition of tables involves the use of the sequence and sequence-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

12. 12 Kyung Hee University TCP Entity State Summary

13. 13 Kyung Hee University TCP Entity State Summary (cont’d) Server Client Unusual Input / Output Now connection is closed in one direction.

14. 14 Kyung Hee University Defining Tables  The entire table represents a single instance of the object type tcpConnTable.  Each row is an instance of the object type tcpConnEntry.

15. 15 Kyung Hee University Private 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

16. 16 Kyung Hee University SNMP V2  SNMPv2 Additional types l Integer32 l Counter32 l Gauge32 l Unsigned32 l Counter64

17. 17 Kyung Hee University SNMP Overview RFC 1156 l allow for expansion of the MIB for vendor specific enhancement RFC 1158 l propose a second MIB (MIB-II) l extend the information base defined in MIB-I l Note: most network devices have software agent that support MIB-II and their own private extensions Each MIB would focus on a specific technology l RFC 1743: IEEE 802.5 Token Ring Interface type MIB l RFC 1757: Remote Network Monitoring MIB (RMON) l RFC 1513: FDDI Interface type MIB l RFC 1493: Bridge MIB

18. 18 Kyung Hee University SNMP Overview  Object Identifier ISO ASN.1 (Abstract Syntax Notation One) Syntax l a subset of ASN.1 defines the syntax for the MIB l use the tree architecture to organize all available information – labeled node – object identifier (OID) and sort text description Subtree Root Node (2) Node (1) Object (1) Node (2) Node A (1) Object (2) Object A (1) OID: 1.2.1.1 or {node A 1}

19. 19 Kyung Hee University SNMP Overview Traversal of the MIB tree l 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)

20. 20 Kyung Hee University SNMP Overview l directory (1) – reserved for future use l 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

21. 21 Kyung Hee University SNMP Overview l experimental (3) – experimental protocols and MIB development intended to enter the standards track l 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 l 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

22. 22 Kyung Hee University SNMP Overview The five SNMPv1message types (RFC1157) l Get-Request: retrieve information from device l Get-Response: agent responds to the Get-Request l Get-Next-Request: ask for the next specific object l Set-Request: for remote configuration parameter l Trap: an unsolicited message Host MS-DOSRouter Terminal serverDevice Data Network station Managing host agent

23. 23 Kyung Hee University SNMP Overview Format 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 PDU type Request ID 0 0 Name X Value X…….. Version Community PDU type Request ID Error status Error index Name XValue X ……... Get-Request, Get-Next-Request, Set-Request Get-Response VersionCommunity PDU type Enterprise Agent addr Generic trap Specific trap TimeName XValue X Trap

24. 24 Kyung Hee University SNMP Overview SNMP trap l an unsolicited message an agent sends to a station l inform the server about the occurrence of specific event l 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 station Device agent Data Network Link failure Trap: interface #2, link down Managing host

25. 25 Kyung Hee University SNMP 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 l community string – station sends a particular password with each message – the password is referred to as the SNMP community string

26. 26 Kyung Hee University SNMP Overview l Examples of an SNMP query station Device agent Data Network Managing host station Device agent Managing host Community string: blee SNMP Get, community string = blee Communication string validated, SNMP Get-Response SNMP Trap, authentication failure Community string: blee SNMP Set, community string= public