Introduction to SNMPagungsr.staff.gunadarma.ac.id/.../Materi_10+SNMP.pdf · 4 SNMP Standard...

transcript

Introduction to SNMP

Contents

1. Basic Concepts

2. Management Information Base

3. Simple Network Management Protocol

4. SNMP Application Examples

5. Reference

Appendix: ASN.1 Concept

Internet UNIX

1. Basic Concepts

ManagementStationNM

PC UNIX

.... FDDI

Polling RMONDevice Notification

/ Router .... ....PC

Internet PC

SNMP Standard

Internet SNMPv1, SNMPv2, SNMPv3

ISO/ITU-T X.700 Series: CMIP/S (Common Management Information Protocol /

Service)

ITU-T M.3000 Series: TMN (Telecommunication Management Networks)

SNMP Concepts

SNMP: Simple Network Management Protocol

De facto standards of network management for TCP/IPnetworks (Internet)

IAB recommends all IP & TCP implementations shouldbe network manageable.

That is, all TCP/IP network devices should supportSNMP.

IAB: Internet Activities Board

SNMP Architectural Model

Key Components One or more Management Stations

• Perform management applications, i.e, Monitor & Control.

Multiple Network Elements• hosts, routers, gateways, ..., which each contain an Agent.

Network Management Protocol• Exchange network management information.

SNMP Architectural Model (cont.)

Management Network Elements (NEs)Station Host Router

NetworkManagement

Protocol. . .

Management Components

Manager

Network Management Protocol

Management Information Base (MIB)

Management Components

Management Station (Manager) Network management applications. Provide an interface which the human network manager can

monitor and control the network.

Network devices should be equipped with agent software sothat they can be managed from a management station. Responds to requests for information from managers. Responds to requests for actions from managers. May asynchronously provide managers with important but

unsolicited information.

Management Components (cont.)

Network Management Protocol Communication protocol between managers and agents

NM protocol provides a standard way to exchangemanagement information between managers and agents.

Management Information Base (MIB) A collection of Managed Objects.

The resources to be managed are represented as objects,called Managed Objects (MOs).

Management Information Base (MIB)Managed Resources

Each resource to be managed isrepresented by an object, calledmanaged object (MO).

The MIB is a structured collectionof MOs. MIB

variable.

Each agent in an NE maintains anMIB.

Monitor: by reading the values ofMOs in the MIB.

Control: by modifying the values ofMOs in the MIB.

NE: Network Element

SNMP Services Four Services Get, Set, GetNext, Trap

Five SNMP PDUs GetRequest, SetRequest, GetNextRequest, GetResponse, Trap

Get, Set, GetNext Request

Get Response

PDU: Protocol Data Unit

SNMP Services

GetNext

Get Request

Get Response

GetNext Request

Get Response

Set Request

Get Response

Trap Request

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.

Get-Next Request

MIB Tree : ＊ In SNMP,Only leaf objects havevalues.

Default UDP Ports for SNMP

ManagementStation

Network Elements (NEs)

162 Any 161 Any

SNMP Standards

SNMP Protocol (Std 15) RFC1157: Simple Network Management Protocol.

Structure of Management Information (SMI) (Std 16) RFC1155: Structure and Identification of Management

Information for TCP/IP-based Internets. RFC1212: Concise MIB Definitions.

MIB-II (Std 17) RFC1213: Management Information Base for Network

Management of TCP/IP-based Internets: MIB-II.

http://www.isi.edu/rfc-editor/rfc.html

2. Management Information Base

Structure of Management Information (SMI) Set of rules on how managed objects should be defined. Objects are defined using Abstract Syntax Notation One ASN.1

(ITU-T X.208 / ISO 8824)

MIB The collection of all defined objects Contains hierarchically organized variables corresponding to

managed objects. MIB-II, RMON MIB, Bridge MIB, Repeater MIB, X.25 MIB,

FDDI MIB, Token Ring MIB, ...

bodyorg

Object Identifier Object Identifier (OID): Global identifier for a particular object type.

An OID consists of a sequence of integers, which specify theposition of the object in the global object identifier tree.

root0 1 2

ccitt iso joint-iso-ccitt0

1 2 3std reg

authority

1.3.6.1.2.1.2

member6

internet

1.3.6.1.2.1

1.3.6.1.4.1

directory1

2 3 4mgmt experimental private

1 1MMIIBB IIII eenntteerrpprriisseess

system iiinnnttteeerrrfffaaaccceee at IP ICMP TCP UDP EGP Trans. SNMP1 2 3 4 5 6 7 8 10 11

Private MIB Registration

Companies can register their private MIBextensions in the global MIB tree bycontacting the Internet Assigned NumbersAuthority (IANA). http://www.iana.org/

Currently assigned enterprise subtrees

ftp://ftp.isi.edu/in-notes/iana/assignments/enterprise-numbers

SMI (RFC1155)RFC1155-SMI DEFINITIONS ::=BEGINEXPORTS -- EVERYTHING

internet, directory, mgmt, experimental, private,enterprises, OBJECT-TYPE, ObjectName,ObjectSyntax, SimpleSyntax,

Counter, Gauge, TimeTicks, Opaque;

internet OBJECT IDENTIFIER ::= { iso org(3) dod(6) 1 }directory OBJECT IDENTIFIER ::= { internet 1 }mgmt OBJECT IDENTIFIER ::= { internet 2 }experimental OBJECT IDENTIFIER ::= { internet 3 }private OBJECT IDENTIFIER ::= { internet 4 }enterprises OBJECT IDENTIFIER ::= { private 1 }

SMI (cont.)OBJECT-TYPE MACRO ::=

BEGINTYPE NOTATION ::=

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

VALUE NOTATION ::= value (VALUE ObjectName)Access ::= "read-only"

| "read-write"| "write-only"| "not-accessible"

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

ASN.1 Macro

ObjectName ::= OBJECT IDENTIFIER

OBJECT-TYPE Example

sysDesc OBJECT-TYPE

SYNTAX DisplayString (SIZE (0..255))

ACCESS read-only

STATUS mandary

::= { system 1}

SMI (cont.)ObjectName ::= OBJECT IDENTIFIER

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}

NetworkAddress ::=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

Object Syntax Summary

Simple Syntax Integer

Octet String

Object Identifier

Application Syntax Network Address

Counter

Time Ticks

Opaque

Concise MIB Definition (RFC 1212)

OBJECT-TYPE MACRO ::=BEGINTYPE NOTATION ::=

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

VALUE NOTATION ::=value (VALUE ObjectName)

DescrPart ::="DESCRIPTION" value (description DisplayString)

| emptyReferPart ::=

"REFERENCE" value (reference DisplayString)| empty

IndexPart ::=

IndexTypes ::=IndexType | IndexTypes "," IndexType

IndexType ::=value (indexobject ObjectName) | type (indextype)

DefValPart ::="DEFVAL" "{" value (defvalue ObjectSyntax) "}"

| emptyEND

Examples: MIB II (RFC 1213)mib-2 OBJECT IDENTIFIER ::= { mgmt 1 }system OBJECT IDENTIFIER ::= { mib-2 1 }interfaces OBJECT IDENTIFIER ::= { mib-2 2 }at OBJECT IDENTIFIER ::= { mib-2 3 }

tcp OBJECT IDENTIFIER ::= { mib-2 6 }udp OBJECT IDENTIFIER ::= { mib-2 7 }egp OBJECT IDENTIFIER ::= { mib-2 8 }-- cmot OBJECT IDENTIFIER ::= { mib-2 9 }

ip OBJECT IDENTIFIER ::= { mib-2 4 }icmp OBJECT IDENTIFIER ::= { mib-2 5 }

transmission OBJECT IDENTIFIER ::= { mib-2 10 }snmp OBJECT IDENTIFIER ::= { mib-2 11 }

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.6mib-2.interface.ifTable.ifEntry.ifType.2mib-2.interface.ifTable.ifEntry.ifType.6

Columnar Objects

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

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

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

ifDescr OBJECT-TYPESYNTAX DisplayString (SIZE(0..255))ACCESS read-onlySTATUS madatory

...::= {ifEntry 2}

Columnar Objects.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)

1.3.6.1.2.1.2.2.1.2.6 1.3.6.1.2.1.2.2.1.3.7

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:10.144.18.118:1200 ===> 10.144.14.40:1600

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

.1.3.6.1.2.1.6.13.1.1.0.144.18.118.1200.10.144.14.40.1600

MIB II

System Group Provide general information about the managed system.

Interfaces Group Contains generic information about the physical interfaces.

Address-Translation Group

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.

TCP Group

MIB-II (cont.)

Contains information about the implementation and operation of TCP at themanaged 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.

Transmission Group Provides details about the underlying transmission media for each interface.

SNMP Group Provides the statistics of SNMP operations at the managed system.

IETF MIBs

1213 MIB-II

1316 Character Stream

1317 RS-232-like Hardware

1471 PPP

1513 RMON for Token Ring

1757 RMON

2021 RMON-II

SNMP Message Version Identifier

Community Name

3. SNMPMessage ::=

SEQUENCE {version INTEGER {version-1(0)},community OCTET STRING,data ANY

Protocol Data Unit }

The length of SNMP messages should notexceed 484 octets.

Version Community SNMP PDU

SNMP Authentication

Community Relationship between an Agent and Managers.

Community Name Used to validate the SNMP messages.

SNMP Password.

Default ‘Get’ community name: “public”. Authentication Failure Agent sends “Authentication Failure Trap” to Manager.

SNMP PDUPDU ::= SEQUENCE {

request-id INTEGER,

Five SNMP PDUs: error-status INTEGER {noError(0),

GetRquest :GetNextRequest :

GetResponse :SetRequest :

Trap :

[0] PDU[1] PDU[2] PDU[3] PDU[4] Trap-PDU

tooBig(1),noSuchName(2),badValue(3),readOnly(4)genErr(5)},

error-index INTEGER,variable-bindings

SEQUENCE OF {name ObjectName,value ObjectSyntax

PDU: Protocol Data Unit

SNMP PDU (cont.)

GetRequest, GetNextRequest, SetRequest

PDU type request-id 0 0 variable-bindings

GetResponse

PDU type request-id error-status error-index variable-bindings

variable-bindings

name value name value . . . name value

Enterprise:

Trap-PDUTrap-PDU ::= [4]

Type of Object generating trap.

Agent Address:Address of object generating trap.

Generic Trap:Generic trap type.

Specific Trap:Enterprise specific trap.

Time Stamp:Time elapsed between the lastinitialization of the network entity andthe generation of the trap.

Variable Bindings“Interesting” information

IMPLICIT SEQUENCE {enterprise OBJECT IDENTIFIER,agent-addr NetworkAddress,generic-trap INTEGER {

coldStart(0),warmStart(1),linkDown(2),linkUp(3),authenticationFailure(4),egpNeighborLoss(5),enterpriseSpecific(6)},

specific-trap INTEGER, time-stamp TimeTicks, variable-bindings VarBindList

PDU type enterprise agent-addr generic-trapspecific-trap time-stamp variable-bindings

How does a Manager do?

NMApplication

Translates InternalData to

ASN.1 Format

Sends RequestPDU to Agent Agent

NMApplication

Translates ASN.1Package to Internal

Data Format

Received ResponsePDU from Agent

Manager

How does an Agent do?

FromManager

Received SNMPRequest PDUfrom Manager

Translates ASN.1Structure to

Internal Data

Maps MIBVariables to

Internal Variables

ToManager

Sends SNMPResponse PDU

to Manager

Translates ResponsePDU to ASN.1

Format

Implement SNMPRequest to Set orGet MIB Value

Main Loop of Agent Agent waits for an incoming datagram in Port 161 Reads the datagram from UDP and notes the transport

address of the sending entity. Increments the QUANTUM to keep track of the logical

request-id being processed by agent De-serializes the datagram into an ASN.1 structure. If error

occurs, log error and discard packet. The ASN.1 structure is translated into SNMP message. If

error occurs, log error and discard packet. Check on VERSION-NUMBER field. If error occurs, log

error and discard packet.

Main Loop of Agent (cont.) Community name is looked up.

If community is unknown to agent, agent sendAUTHENTICATION trap to Manager station in Port 162; logerror and discard packet.

Agent loops through list of variables in the request.

If no prototype is found, return a GET-RESPONE with errornoSuchName and discard package.

Once prototype is fund, operation is checked against community profile. Ifmismatch occurs, return get-respone with error noSuchName or readOnlyand discard package.

Otherwise, agent invokes access routine to perform the desired operation.

What's New in SNMPv2

No more Trap PDU, 3 New PDUs: getBulkReq, InformReq, SNMPv2-Trap

Added Security

18 Error Status Values

SNMPv2 SMI / SNMPv2 MIB

M-to-M Communications

Table Operations

4. SNMP Application Examples SNMP Commands snmpget [options] node variable [...]

• query a node using SNMP Get request

snmpnext [options] node variable [...]• query a node using SNMP GetNext request

snmpwalk [options] node variable• query a node repeatedly using SNMP GetNext/GetBulk requests

snmptrap [-d] [-p port] [-c community] node enterprise agent-addr generic-trap specific-trap time-stamp variable type value[variable type value...]

• issue an SNMP Version 1 Trap

options:[-d] [-t timeout] [-r retries] [-p port] [-c community] [-v version]

Example for snmpget>>snmpget -d 10.144.18.118 .1.3.6.1.2.1.1.1.0Transmitted 41 bytes to camry (10.144.18.118) port 161:Initial Timeout: 0.80 seconds

0: 30 27 02 01 00 04 06 70 75 62 6c 69 63 a0 1a 02 0'.....public...16: 02 18 bc 02 01 00 02 01 00 30 0e 30 0c 06 08 2b .........0.0...+32: 06 01 02 01 01 01 00 05 00 -- -- -- -- -- -- -- ................0: SNMP MESSAGE (0x30): 39 bytes

5: OCTET-STR COMMUNITY (0x4) 6 bytes: "public"13: GET-REQUEST-PDU (0xa0): 26 bytes15: INTEGER REQUEST-ID (0x2) 2 bytes: 633219: INTEGER ERROR-STATUS (0x2) 1 bytes: noError(0)22: INTEGER ERROR-INDEX (0x2) 1 bytes: 025: SEQUENCE VARBIND-LIST (0x30): 14 bytes27: SEQUENCE VARBIND (0x30): 12 bytes29: OBJ-ID (0x6) 8 bytes: .1.3.6.1.2.1.1.1.039: NULL (0x5) 0 bytes

Example for snmpget (cont.)Received 69 bytes from camry (10.144.18.118) port 161:

0: 30 43 02 01 00 04 06 70 75 62 6c 69 63 a2 36 02 0C.....public.6.16: 02 18 bc 02 01 00 02 01 00 30 2a 30 28 06 08 2b .........0*0(..+32: 06 01 02 01 01 01 00 04 1c 53 75 6e 20 53 4e 4d .........Sun SNM48: 50 20 41 67 65 6e 74 2c 20 53 55 4e 57 2c 55 6c P Agent, SUNW,Ul64: 74 72 61 2d 31 -- -- -- -- -- -- -- -- -- -- -- tra-1...........0: SNMP MESSAGE (0x30): 67 bytes2: INTEGER VERSION (0x2) 1 bytes: 0 (SNMPv1)5: OCTET-STR COMMUNITY (0x4) 6 bytes: "public"13: RESPONSE-PDU (0xa2): 54 bytes15: INTEGER REQUEST-ID (0x2) 2 bytes: 633219: INTEGER ERROR-STATUS (0x2) 1 bytes: noError(0)22: INTEGER ERROR-INDEX (0x2) 1 bytes: 025: SEQUENCE VARBIND-LIST (0x30): 42 bytes27: SEQUENCE VARBIND (0x30): 40 bytes29: OBJ-ID (0x6) 8 bytes: .1.3.6.1.2.1.1.1.039: OCTET-STR (0x4) 28 bytes: "Sun SNMP Agent, SUNW,Ultra-1"

system.sysDescr.0 : DISPLAY STRING- (ascii): Sun SNMP Agent, SUNW,Ultra-1

Example of snmpwalk

snmpwalk 10.144.18.118 .1.3.6.1.2.1.1system.sysDescr.0 : DISPLAY STRING- (ascii): Sun SNMP Agent, SUNW,Ultra-1

system.sysObjectID.0 : OBJECTIDENTIFIER: .iso.org.dod.internet.private.enterprises.42.2.1.1

system.sysUpTime.0 22 days, 22:36:39.58

system.sysContact.0 : DISPLAY STRING- (ascii): lino@ms.chttl.com.tw

system.sysName.0 : DISPLAY STRING- (ascii): camry

system.sysLocation.0 : DISPLAY STRING- (ascii): Information TechnologyLaboratory 3F

system.sysServices.0 : INTEGER: 72 (01001000)B

Example of snmptrap snmptrap -d manager .1.3.6.1.4.1.612.1.1 10.144.18.116 6 99999

0 .1.3.6.1.1 octetstringascii "Trap test"Transmitted 64 bytes to manager (10.144.18.100) port 162:

0: 30 3e 02 01 00 04 06 70 75 62 6c 69 63 a4 31 06 0>.....public.1.16: 09 2b 06 01 04 01 84 64 01 01 40 04 0a 90 12 74 .+.....d..@....t32: 02 01 06 02 03 01 86 9f 43 01 00 30 13 30 11 06 ........C..0.0..48: 04 2b 06 01 01 04 09 54 72 61 70 20 74 65 73 74 .+.....Trap test0: SNMP MESSAGE (0x30): 62 bytes2: INTEGER VERSION (0x2) 1 bytes: 0 (SNMPv1)5: OCTET-STR COMMUNITY (0x4) 6 bytes: "public"

13: V1-TRAP-PDU (0xa4): 49 bytes15: OBJ-ID ENTERPRISE (0x6) 9 bytes: .1.3.6.1.4.1.612.1.126: IPADDRESS AGENT-ADDR (0x40) 4 bytes: 10.144.18.116 (manager2)32: INTEGER GENERIC-TRAP (0x2) 1 bytes: 635: INTEGER SPECIFIC-TRAP (0x2) 3 bytes: 9999940: TIMETICKS TIME-STAMP (0x43) 1 bytes: 0 (0x0)43: SEQUENCE VARBIND-LIST (0x30): 19 bytes45: SEQUENCE VARBIND (0x30): 17 bytes47: OBJ-ID (0x6) 4 bytes: .1.3.6.1.153: OCTET-STR (0x4) 9 bytes: "Trap test"

Get System Information

Get “System Group” of MIB II

Use get_request or get_next_requestsysDescr .1.3.6.1.2.1.1.1.0

sysObjectID .1.3.6.1.2.1.1.2.0

sysUptime .1.3.6.1.2.1.1.3.0

sysContact .1.3.6.1.2.1.1.4.0

sysName .1.3.6.1.2.1.1.5.0

sysLocation .1.3.6.1.2.1.1.6.0

Get Interface Information

Get “Interface Group” of MIB II

Repeatedly Use “get_next_request” Note: We don’t know the ifIndex values in

ifTable.First get the next object of .ifTable.ifEntry.0

Then repeatedly “get_next”Until the whole subtree is visited.

Traffic Monitoring

Get “ifInOctets” and “ifOutOctets” of MIB IIInterface Group

t1: C1 t2: C2

Utilization (%) =(C2 - C1 ) 8

(t2 - t1) Bandwidth 100%

6. Reference

The Simple Book, marshall T.Rose, Prentice-Hall Inc.

SNMP, SNMPv2 and RMON: The Practical Guide to NetworkManagement, Willeam Stallings

SMI; http://ds.internic.net/rfc/rfc1155.txt

Concise MIB Format; http://ds.internic.net/rfc/rfc1212.txt

SNMP; http://ds.internic.net/rfc/rfc1157.txt

MIB II; http://ds.internic.net/rfc/rfc1213.txt

Trap Format; http://ds.internic.net/rfc/rfc1215.txt

ASN.1 and BER; ITU-T X.208, X.209

Development of SNMP Standards

SNMPv2 SNMPv3

RMON I

RMON II

SNMPv3

An Architecture for Describing Internet ManagementFrameworks

Local Processing Model for version 3 of the SimpleNetwork Management Protocol (SNMPv3)

Message Processing and Control Model for version 3of the Simple Network Management Protocol (SNMP)

User-based Security Model for version 3 of the SimpleNetwork Management Protocol (SNMPv3)

View-based Access Control Model (VACM) for version3 of the Simple Network Management Protocol (SNMP)

User-based Security Model (USM) for version 3 of theSimple Network Management Protocol (SNMPv3)

RMON I & II

APPLICATION Presentation

Session RMON2

RMON 2

Transport Network

Data Link(MAC)

Ethern et

TokenRing

Frame Relay,HDLC, PPD,SDLL, X.25,

CIRPPhysical

seriesT1 E1

Appendix: ASN.1 Concepts

ASN.1: Abstract Syntax Notation One

ISO/ITU-T Standards: ISO 8824/ITU-T X.208

Abstract Syntax: Use a syntax to define data/data structure independent of

machine-oriented structures and restrictions.

Use in SNMP Define SNMP PDU format

Define management information (MIB)

ASN.1 Reserved Words

All reserved words MUST be upper case BOOLEAN INTEGER BIT STRING

OCTET NULL OF SEQUENCE

SET IMPLICIT CHOICE ANY

EVTERNAL OBJECT END IDENTIFIER

OPTIONAL DEFAULT TRUE COMPONTS

FALSE BEGIN

What are defined using ASN.1 Types: data structures e.g. Counter, Gauge, IpAddess, ...

Values:

e.g. sysContact, ifTable, ifSpeed, ...

Macros: used to change the actual grammar of ASN.1 e.g. OBJECT-TYPE, ACCESS, ...

Modules

Module: A collection of ASN.1 descriptionsModule Structure

<module name> DEFINITION ::= BEGIN<module body>

Example EmptyModule

DEFINITION ::= BEGINEND

Tags and Types

Tags Every type defined with ASN.1 is assigned a tag

Tag = Class + Number

• Class: (Bit 8,7 in BER tag)– Universal 0 0

– Application 0 1

– Context-specific 1 0

– Private 1 1

• Number: non-negative Integer

BER: Basic Encoding Rules

Tags and Types (cont.) Universal Tag ASN.1 Type

1 BOOLEAN2 INTEGER3 BIT STRING4 OCTET STRING5 NULL

7 ObjectDescriptor8 EXTERNAL9 REAL10 ENUMERATED12-15 Reserved

Universal Tag ASN.1 Type

18 NumericString

19 PrintableString

20 TeletexString

21 VediotextString

22 IA5String

23 UTCTime

24 GeneralizeTime

25 GraphicString

26 VisssibleString

27 GeneralString16 SEQUENCE, SEQUENCE OF17 SET, SET OF

28 CharacterString

29-... Reserved

Values in ASN.1

General format of a value assignment <valuereference> <type> ::= <value>

Examples: BOOLEAN

• Married ::= BOOLEAN

• currentStatus Married ::= FALSE

INTEGER• Color ::= INTEGER{red (0), blue (1), yellow (2)}

• defaultColor Color ::= 1

• defaultColor Color ::= blue

Basic Encode Rules

A transfer syntax notation

ISO/ITU-T Standards: ISO 8825/ITU-T X.209

Values from any abstract syntax defined using ASN.1 can

BER uses Tag, Length, Value (TLV) encoding• Tag: “identifier”, Length: length of content, Value: “contents”

Each value may itself be made up of one or more TLV-encoded values

Introduction to SNMPagungsr.staff.gunadarma.ac.id/.../Materi_10+SNMP.pdf · 4 SNMP Standard...

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