Chapter 4SNMPv1: Organization and Information Models

Internet SNMP Management

• Internet Engineering Task Force (IETF)• 1990 SNMPv1• 1995 SNMPv2• 1998 SNMPv3

• Internet documents:• Request for Comments (RFC)• IETF STD Internet Standard• FYI For your information

http://www.ietf.org/

http://www.ietf.org/rfc.htmlhttp://www.ietf.org/rfc/rfcNNNN.txt

SNMP MIBRFC 3418

SNMP MIBRFC 3418

SMIv2RFC 2578

SMIv2Conventions

RFC 2579

SMIv2Conformances

RFC 2580

SNMP MIBRFC 3418

SNMPv2Protocol Ops

RFC 3416

`

SNMP Model• Organization Model

• Relationship between network element, agent, and manager

• Hierarchical architecture• Information Model

• Uses ASN.1 syntax• SMI (Structure of Management Information• MIB (Management Information Base)

• Communication Model• Transfer syntax• SNMP over TCP/IP• Communication services addressed by messages• Security framework community-based model

Two-Tier Organization Model

Three-Tier Organization Model: RMON

ManagedObjects

SNMPManager

RMONProbe

• RMON Remote Monitoring• RMON I• RMON II

Three-Tier Organization Model: Proxy

Non-SNMPManagedObjects

SNMP Manager

ProxyServer

SNMPManagedObjects

SNMP System Architecture

Network

網路介面

SNMP

UDP

IP

網路介面

SNMP

UDP

IP

網路介面

SNMP

UDP

IP

Manager Agent Agent

. . .

ManagementStation Host Router

Network Elements (NEs)

Network Management

Protocol

SNMP

SNMP Services

Four Services Get, Set, GetNext, Trap

Five SNMP Messages GetRequest, SetRequest, GetNextRequest,

GetResponse, Trap

Manager Agent(s)

Get, Set, GetNext Request

Get Response

Trap

SNMP Services

Get Request

Get ResponseManager Agent

GetNext Request

Get ResponseManager Agent

Set Request

Get ResponseManager Agent

Trap RequestManager Agent

GetGet

GetNextGetNext

SetSet

TrapTrap

GetGet

GetNextGetNext

SetSet

TrapTrap

SNMP Services (cont.)

Get Request: Retrieve the values of objects in the MIB of an agent.

Get-Next Request: Retrieve the values of the next objects in the MIB of

an agent. Set Request:

Update the values of objects in the MIB of an agent. Trap Request

Report extraordinary events to the manager.

4.7 Information Model

• Structure of Management Information (SMI) (RFC 1155, RFC 1212)

• Managed Object• Scalar• Aggregate or tabular object

• Management Information Base (RFC 1213)

Managed Object

Object Type Object Instance

Managed Object: Multiple Instances

Object Type Object Instance

Object Name• Object is uniquely defined by

• DESCRIPTOR• OBJECT IDENTIFIER

Internet Subnodes

directory OBJECT IDENTIFIER ::= {internet 1}

mgmt OBJECT IDENTIFIER ::= {internet 2}

experimental OBJECT IDENTIFIER ::= {internet 3}

private OBJECT IDENTIFIER ::= {internet 4}

root

ccitt iso joint-iso-ccitt

directory

0 1 2

std regauthority

memberbody

org0

1 2 3

dod

internet

6

1

12 3 4

mgmt experimental private

MIB II

system1

interface2

at3

IP4

ICMP5

TCP6

UDP7

EGP8

Trans.10

SNMP11

1 1enterprises

1.3.6.1.2.1.2 1.3.6.1.4.1

1.3.6.1.2.1

MIB II

interface

enterprises

Private MIB Example

Enterprise Number

http://www.iana.org/assignments/enterprise-numbers

http://www.iana.org/

SNMP ASN.1 Data Type

Primitive Data Types

Structure Data Type Comments Primitive types INTEGER Subtype INTEGER (n1..nN)

Special case: Enumerated INTEGER type

OCTET STRING 8-bit bytes binary and textual data Subtypes can be specified by either range or fixed

OBJECT IDENTIFIER Object position in MIB NULL Placeholder

• subtype:

• INTEGER (0..255)

• OCTET STRING (SIZE 0..255)

• OCTET STRING (SIZE 8)

Enumerated

• Special case of INTEGER data type

Defined or Application Data Type

Constructor or Structured Data Type:SEQUENCE List Marker

SEQUENCE { <type1>, <type2>,…, <typeN> }

IpAddrEntry ::= SEQUENCE {

ipAdEntAddr IpAddress,ipAdEntIfIndex INTEGER,ipAdEntNetMask IpAddress,ipAdEntBcastAddr INTEGER,ipAdEntReasmMaxSize INTEGER

(0..65535)}

Constructor or Structured Data Type:SEQUENCE OFSEQUENCE OF <entry>

where <entry> is a list constructor ipAddrTable OBJECT-TYPE

SYNTAX SEQUENCE OF IpAddrEntry

ACCESS not-accessible

STATUS mandatory

DESCRIPTION

"The table of addressing information relevant to

this entity's IP addresses."

::= { ip 20 }

Example: IP Address Table

• Each row (table entry) is a sequence: IpAddrEntry.

• The ipAddrTable table is a sequence of rows (entries), i.e. a sequence of ipAddrEntry.

Encoding

• Basic Encoding Rules (BER)- Type, Length, and Value (TLV)

Type Length Value

Class(7-8th bits)

P/C(6th bit)

Tag Number(1-5th bits)

SNMP Data Types and Tags

Type Tag

OBJECT IDENTIFIER UNIVERSAL 6SEQUENCE UNIVERSAL 16IpAddress APPLICATION 0Counter APPLICATION 1Gauge APPLICATION 2TimeTicks APPLICATION 3Opaque APPLICATION 4

4.7.3 Managed Object: Structure

OBJECT:sysDescr: { system 1 }

Syntax: OCTET STRING Definition: "A textual description of the entity. This value should include the full name and version identification of the system's hardware type, software operating-system, and networking software. It is mandatory that this only contain printable ASCII characters." Access: read-only Status: mandatory

Figure 4.17 Specifications for System Description

SMIv1, SMIv2 SMIv1:

SMI (RFC 1155) Concise MIB (RFC 1212) Trap-Type (RFC 1215)

SMIv2: SMIv2 (RFC 2578) Textual Conventions (RFC 2579) Conformance Statements (RFC 2580)

OBJECT-TYPE MACRO ::= BEGINOBJECT-TYPE MACRO ::= BEGIN

TYPE NOTATION ::=TYPE NOTATION ::= "SYNTAX" type (TYPE "SYNTAX" type (TYPE ObjectSyntaxObjectSyntax))

"ACCESS" Access"ACCESS" Access

"STATUS" Status"STATUS" Status

VALUE NOTATION ::= value (VALUE VALUE NOTATION ::= value (VALUE ObjectNameObjectName))

Access ::= "read-only" | "read-write" | "write-only Access ::= "read-only" | "read-write" | "write-only | "not-accessible"| "not-accessible"

Status ::= "mandatory" | "optional" | "obsolete"Status ::= "mandatory" | "optional" | "obsolete"

ENDEND

Object-Type Macro (RFC 1155)

OBJECT-TYPE MACRO (RFC1212)OBJECT-TYPE MACRO ::=BEGIN TYPE NOTATION ::=

"SYNTAX" type(ObjectSyntax) "ACCESS" Access "STATUS" Status

DescrPartReferPartIndexPartDefValPart

VALUE NOTATION ::= value (VALUE ObjectName)

ObjectName ::= OBJECT IDENTIFIER

OBJECT-TYPE Example

sysLocation OBJECT-TYPE

SYNTAX DisplayString (SIZE (0..255))

ACCESS read-write

STATUS mandatory

DESCRIPTION

"The physical location of this node (e.g.,

`telephone closet, 3rd floor')."

::= { system 6 }

DisplayString ::= OCTET STRING (SIZE (0..255))

Go to Next Example

"SYNTAX" type(ObjectSyntax)ObjectSyntax ::=

CHOICE {simple SimpleSyntax,application-wide ApplicationSyntax

}

SimpleSyntax ::=CHOICE {

number INTEGER,string OCTET STRING,object OBJECT IDENTIFIER,empty NULL

}

ApplicationSyntax ::= CHOICE {

address NetworkAddress,counter Counter,gauge Gauge,ticks TimeTicks,

arbitrary Opaque}

Back to OBJECT TYPE

ApplicationSyntaxNetworkAddress ::=

CHOICE {internet IpAddress

} IpAddress ::=

[APPLICATION 0] IMPLICIT OCTET STRING (SIZE (4))Counter ::=

[APPLICATION 1] IMPLICIT INTEGER (0..4294967295)Gauge ::=

[APPLICATION 2] IMPLICIT INTEGER (0..4294967295)TimeTicks ::=

[APPLICATION 3] IMPLICIT INTEGER (0..4294967295) Opaque ::=

[APPLICATION 4] IMPLICIT OCTET STRING

0 .. 232-1

Back to OBJECT TYPE

"ACCESS" Access "STATUS" Status

Access ::= "read-only"| "read-write"| "write-only"| "not-accessible

Status ::= "mandatory"| "optional"| "obsolete"| "deprecated"

Back to OBJECT TYPE

DescrPartDescrPart ::=

"DESCRIPTION" value (description DisplayString)

| empty

ReferPart ::="REFERENCE" value (reference DisplayString)

| empty

ReferPart

Back to OBJECT TYPE

DefValPart

ifNumber OBJECT-TYPESYNTAX INTEGERACCESS read-onlySTATUS mandatoryDEFVAL 1DESCRIPTION

"The number of network interfaces (regardless of

their current state) present on this system.“::= { interfaces 1 }

DefValPart ::="DEFVAL" "{" value (defvalue

ObjectSyntax) "}" | empty

Example:

Back to OBJECT TYPE

IndexPart

IndexTypes ::=IndexType | IndexTypes "," IndexType

IndexType ::=value (indexobject

ObjectName)| type (indextype)

IndexSyntax ::=CHOICE {

number INTEGER (0..MAX), string OCTET STRING, object OBJECT IDENTIFIER, address NetworkAddress, ipAddress IpAddress }

IndexPart ::= "INDEX" "{" IndexTypes "}"

Back to OBJECT TYPE

instance-identifier (INDEX) integer-valued

3 3 string-valued, fixed-length strings

‘004096563c2e’H 0.64.150.86.60.46 string-valued, variable-length strings

“IIS Admin” 9.73.73.83.32.65.100.109.105.110

object identifier-valued 1.3.6.1.2 5.1.3.6.1.2

NetworkAddress-valued 163.22.20.16 1.163.22.20.16

IpAddress-valued 163.22.20.16 163.22.20.16

Index - variable-length stringsvSvcTable OBJECT-TYPE

SYNTAX SEQUENCE OF SvSvcEntry ACCESS not-accessible STATUS mandatory DESCRIPTION "A list of service entries describing network services installed on this server.“::= { server 3 }

svSvcEntry OBJECT-TYPE SYNTAX SvSvcEntry ACCESS not-accessible STATUS mandatory DESCRIPTION "The names of the network services installed on this server." INDEX { svSvcName }::= { svSvcTable 1 }

Back to OBJECT TYPE

OBJECT-TYPE Example

dot1dBasePortEntry OBJECT-TYPESYNTAX Dot1dBasePortEntryACCESS not-accessible STATUS mandatory DESCRIPTION

"A list of information for each port of the bridge."

REFERENCE"IEEE 802.1D-1990: Section 6.4.2, 6.6.1"

INDEX { dot1dBasePort }::= { dot1dBasePortTable 1 }

Aggregate Object

• A group of objects

• Also called tabular objectstabular objects

• Can be represented by a table with

• Columns of objects

• Rows of instances

Table of Objects

List of Objects

Objects

Aggregate M.O. Macro: Table Object

ipAddrTable OBJECT-TYPE SYNTAX SEQUENCE OF IpAddrEntry ACCESS not-accessible

STATUS mandatoryDESCRIPTION

"The table of addressing information

relevant to this entity's IP addresses."::= {ip 20}

Aggregate M.O. Macro: Entry Object

ipAddrEntry OBJECT-TYPESYNTAX IpAddrEntryACCESS not-accessibleSTATUS mandatoryDESCRIPTION

"The addressing information for one of this entity's IP addresses."

INDEX { ipAdEntAddr }::= { ipAddrTable 1 }

ipAddrEntry: OBJECT-TYPEIpaddrEntry: SYNTAX

Aggregate M.O. Macro: Entry Object

IpAddrEntry ::= SEQUENCE { ipAdEntAddr IpAddress, ipAdEntIfIndex INTEGER, ipAdEntNetMask IpAddress, ipAdEntBcastAddr INTEGER, ipAdEntReasmMaxSize INTEGER (0..65535) }

Aggregate M.O. Macro: Columnar Objects

ipAdEntAddr OBJECT-TYPE SYNTAX IpAddress

ACCESS read-onlySTATUS mandatoryDESCRIPTION

"The IP address to which this entry's

addressing information pertains.”::= { ipAddrEntry 1 }

Tabular Representation of Aggregate Object

Tabular Representation of Aggregate Object

Multiple Instances of Aggregate Managed Object

ipAddrTable {1.3.6.1.2.1.4.20}ipAddrEntry (1)

ipAdEntAddr (1)ipAdEntIfIndex (2)ipAdEntNetMask (3)ipAdEntBcastAddr (4)ipAdEntReasmMaxSize (5)

Columnar object ID of ipAdEntBcastAddr is (1.3.6.1.2.1.4.20.1.4):

iso org dod internet mgmt mib ip ipAddrTable ipAddrEntry ipAdEntBcastAddr 1 3 6 1 2 1 4 20 1 4

Figure 4.23(a) Columnar objects under ipAddrEntry

Example

Identification of Managed Objects Use Object Identifier (OID) OID = Object Type OID . Instance

Identifier Object Type OID:

Each Object type has a unique OID Instance Identifier:

Identify instances of object type E.g .mib-2.interface.ifTable.ifEntry.ifDescr.2

Two Kinds of Managed Objects

Type-Specific Objects: sysDescr OBJECT-TYPE

SYNTAX DisplayString (SIZE(0..255))

::= {system 1}

OID: mib-2.system.1.0 Columnar Objects

OID: mib-2.interface.ifTable.ifEntry.ifDescr.2mib-2.interface.ifTable.ifEntry.ifDescr.6 mib-2.interface.ifTable.ifEntry.ifType.2mib-2.interface.ifTable.ifEntry.ifType.6

Columnar Objects

ifTable OBJECT-TYPE SYNTAX SEQUENCE OF IfEntry … ::= { interface 2 }

IfEntry ::= SEQUENCE { ifIndex INTEGER, ifDescr DisplayString, ifType INTEGER, …}

ifEntry OBJECT-TYPE SYNTAX IfEntry … INDEX {ifIndex } ::= { ifTable 1}

ifDescr OBJECT-TYPE SYNTAX DisplayString (SIZE(0..255)) ACCESS read-only STATUS madatory...::= {ifEntry 2}

Columnar Objects

ifIndex ifDescr ifType . . .

1 le0 6 . . .

6 llc0 1 . . .

7 lo0 24 . . .

9 le1 6 . . .

.ifTable.ifEntry.1 (1.3.6.1.2.1.2.2.1.1) .ifTable.ifEntry.2 (1.3.6.1.2.1.2.2.1.2)

.ifTable.ifEntry.3 (1.3.6.1.2.1.2.2.1.3)

1.3.6.1.2.1.2.2.1.3.71.3.6.1.2.1.2.2.1.2.6

Index in MIB II ifEntry {ifIndex} atEntry {atNetIfIndex, atNetAddress} ipAddrEntry {ipAdEntAddr } ipRouteEntry {ipRouteDest} ipNetToMediaEntry {ipNetToMediaIfIndex,

ipNetToMediaNetAddress} tcpConnEntry

{tcpConnLocalAddress, tcpConnLocalPort, tcpConnRemoteAddress, tcpConnRemotePort}

udpEntry {udpLocalAddress, udpLocalPort}

egpNeighEntry {egpNeighAddr}

Index Example

To get the state of the TCP connection:10.10.13.137: 3125 ===> 61.30.91.235: 80

Use snmp_get_req. to get the “tcpConnState” of the tcpConnTable in MIB II.

tcpConnState ==> 1.3.6.1.2.1.6.13.1.1

1.3.6.1.2.1.6.13.1.1.10.10.13.137.3125.61.30.91.235.80

tcpConnTable

4.7.4 MIB-II

• MIB-II (RFC 1213) is superset of MIB-I

• Objects that are related grouped into object groups

• MIB module comprises module name, imports from other modules, and definitions of current module

• RFC 1213 defines eleven groups

MIB II (RFC 1213) System Group

Provide general information about the managed system. Interfaces Group

Contains generic information about the physical interfaces. Address-Translation Group

Contains information about the mapping between network addresses and physical addresses for each physical interface.

IP Group Contains information about the implementation and

operation of IP at the managed system. ICMP Group

Contains information about the implementation and operation of ICMP at the managed system.

MIB-II (cont.) TCP Group

Contains information about the implementation and operation of TCP at the managed system.

UDP Group Contains information about the implementation and

operation of UDP at the managed system. EGP Group

Contains information about the implementation and operation of EGP at the managed system.

CMOT Group Placeholder for OSI (CMIP Over TCP/IP)

Transmission Group Provides details about the underlying transmission

media for each interface. SNMP Group

Provides the statistics of SNMP operations at the managed system.

System Group

System Group

sysServices OBJECT-TYPE SYNTAX INTEGER (0..127) ACCESS read-only STATUS mandatory DESCRIPTION "A value which indicates the set of services that this entity primarily offers. The value is a sum. This sum initially takes the value zero, Then, for each layer, L, in the range 1 through 7, that this node performs transactions for, 2 raised to (L - 1) is added to the sum. For example, a node which performs primarily routing functions would have a value of 4 (2^(3-1)). In contrast, a node which is a host offering application services would have a value of 72 (2^(4-1) + 2^(7-1)). Note that in the context of the Internet suite of protocols, values should be calculated accordingly: layer functionality 1 physical (e.g., repeaters) 2 datalink/subnetwork (e.g., bridges) 3 internet (e.g., IP gateways) 4 end-to-end (e.g., IP hosts) 7 applications (e.g., mail relays) For systems including OSI protocols, layers 5 and 6 may also be counted." ::= { system 7 }

72= 8 + 64

01000100

System Information

Interfaces GroupInterfaces Group

iFEntry

ifEntry OBJECT-TYPE SYNTAX IfEntry ACCESS not-accessible STATUS mandatory DESCRIPTION

"An interface entry containing objects at the subnetwork layer and below for a particular interface."

INDEX {ifIndex}

::= {ifTable 1}

ifType

http://www.iana.org/assignments/smi-numbers

ifType OBJECT-TYPE SYNTAX INTEGER { other(1), -- none of the following regular1822(2), hdh1822(3), ddn-x25(4), rfc877-x25(5), ethernet-csmacd(6), iso88023-csmacd(7), iso88024-tokenBus(8), iso88025-tokenRing(9), iso88026-man(10), starLan(11), proteon-10Mbit(12), proteon-80Mbit(13), hyperchannel(14), fddi(15), lapb(16), sdlc(17), ds1(18), -- T-1 e1(19), -- european equiv. of T-1 basicISDN(20), primaryISDN(21), -- proprietary serial propPointToPointSerial(22), ppp(23),

……….

ifAdminStatus OBJECT-TYPE SYNTAX INTEGER { up(1), -- ready to pass packets down(2), testing(3) -- in some test mode } ACCESS read-write STATUS mandatory DESCRIPTION "The desired state of the interface. The testing(3) state indicates that no operational packets can be passed." ::= { ifEntry 7 }

ifOperStatus OBJECT-TYPE SYNTAX INTEGER { up(1), -- ready to pass packets down(2), testing(3) -- in some test mode } ACCESS read-only STATUS mandatory DESCRIPTION "The current operational state of the interface. The testing(3) state indicates that no operational packets can be passed." ::= { ifEntry 8 }

ifTable

ifTable (cont.)

IP GroupIP Group

IP Group

• ipForwarding: • forwarding(1)• not-forwarding(2)

• IP Address Table contains table of IP addresses• IP Route Table contains an entry for each route• IP Network-to-Media Table is address translation

table mapping IP addresses to physical addresses

IP Address Table

ipAddrTable

IP Routing Table

IP Routing TableEntity OID Description (brief)

ipRouteTable ip 21 IP routing tableipRouteEntry ipRouteTable 1 Route to a particular destinationipRouteDest ipRouteEntry 1 Destination IP address of this routeipRouteIfIndex ipRouteEntry 2 Index of interface, same as ifIndexipRouteMetric1 ipRouteEntry 3 Primary routing metric for this routeipRouteMetric2 ipRouteEntry 4 An alternative routing metric for this routeipRouteMetric3 ipRouteEntry 5 An alternative routing metric for this routeipRouteMetric4 ipRouteEntry 6 An alternative routing metric for this routeipRouteNextHop ipRouteEntry 7 IP address of the next hopipRouteType ipRouteEntry 8 Type of routeipRouteProto ipRouteEntry 9 Routing mechanism by which this route was

learnedipRouteAge ipRouteEntry 10 Number of seconds since routing was last updatedipRouteMask ipRouteEntry 11 Mask to be logically ANDed with the destination

address before comparing with the ipRouteDestfield

ipRouteMetric5 ipRouteEntry 12 An alternative metric for this routeipRouteInfo ipRouteEntry 13 Reference to MIB definition specific to the routing

protocol

ipRouteTable Example

other(1), invalid(2), direct(3), indirect(4)

other(1), local(2), netmgmt(3),icmp(4), egp(5),ggp(6),hello(7),rip(8),is-is(9),s-is(10),ciscoIgrp(11),bbnSpfIgp(12),ospf(13),bgp(14)

Sec.

IP Address Translation Table

IP Address Translation Table

Entity OID Description (brief)ipNetToMediaTable ip 22 Table mapping IP addresses to

physical addressesipNetToMediaEntry IpNetToMediaTable 1 IP address to physical address

for the particular interfaceipNetToMediaIfIndex IpNetToMediaEntry 1 Interfaces on which this entry's

equivalence is effective; sameas ifIndex

ipNetToMediaPhysAddress IpNetToMediaEntry 2 Media dependent physicaladdress

ipNetToMediaNetAddress IpNetToMediaEntry 3 IP addressipNetToMediaType IpNetToMediaEntry 4 Type of mapping

IPNetToMediaTable

= ARP Table

other(1),invalid(2)invalid(2), dynamic(3),static(4)

read-write

ICMP Group

ICMP

• Objects associated with ping• icmpOutEchos

- # ICMP echo messages sent• icmpInEchoReps

- # ICMP echo reply messages received

• Objects associated with traceroute/tracert• icmpInTimeExcs

• # ICMP time exceeded messages received

TCP Group

TCP Connection Table

TCP Connection Table

Entity OID Description (brief)

tcpConnTable tcp 13 TCO connection tabletcpconnEntry TcpConnTable 1 Information about a particular TCP

connectiontcpConnState TcpConnEntry 1 State of the TCP connectiontcpConnLocalAddressTcpConnEntry 2 Local IP addresstcpConnLocalPort TcpConnEntry 3 Local port numbertcpConnRemAddress TcpConnEntry 4 Remote IP addresstcpConnRemPort TcpConnEntry 5 Remote port number

tcpConnState OBJECT-TYPE SYNTAX INTEGER { closed(1), listen(2), synSent(3), synReceived(4), established(5), finWait1(6), finWait2(7), closeWait(8), lastAck(9), closing(10), timeWait(11), deleteTCB(12)deleteTCB(12) } ACCESS read-write STATUS mandatory …::= { tcpConnEntry 1 }

TCP Connection StateTCP Connection State

tcpConnTable

UDP Group

UDP Group

Entity OID Description (brief)udpInDatagrams udp 1 Total number of datagrams delivered to the

usersudpNoPorts udp 2 Total number of received datagrams for

which there is no applicationudpInErrors udp 3 Number of received datagrams with errorsudpOutDatagrams udp 4 Total number of datagrams sentudpTable udp 5 UDP Listener tableudpEntry udpTable 1 Information about a particular connection or

UDP listenerudpLocalAddress udpEntry 1 Local IP addressudpLocalPort udpEntry 2 Local UDP port

udpTable