network management concepts: models and languages * * mani subramanian “network management:...

Network Management Concepts: Models and Languages*

*Mani Subramanian “Network Management: Principles and practice”, Addison-Wesley, 2000.

Network Management Concepts: Models and Languages

Network Management Systems Origin of Network Management OSI Management Models

Organization Information Communication Functional

Abstract Syntax Notation 1 (ASN.1)

Basic Encoding Rules, BER

Network Management Systems (NMS)

A NMS is an integrated collection of tools for network monitoring and control

Network management is concerned with system resources (e.g., hubs, bridges, routers, etc.) and the connectivity among them

NME and NMA: collection of software devoted for NM task

Workstation (agent)

NMA

OSComm

NME Appl

OS

Comm

NME Appl OS

Comm

NME

Router (agent)

Server (agent)

OS

Comm

NME Appl

Network control

host (Manager)

Elements of NMS

Network Management Entity (NME)o Collect statistics on

communication and related activities

o Store statistics locallyo Responds to commands

from the network control center (e.g. report its object status, etc.)

o Generate messages to the network control center when local conditions change (e.g., port failure)

Network Management Application (NMA)

o Interface allowing authorized users to manage the network

o Display mgnt information and issue control commands to NME

To maintain high availability, two or more network control hosts (managers) are used!

Network Management Components

Network Agent monitors its respective objects either in response to a query from the NMS or triggered by a local alarm

The agent communicates the relevant data to the NMS

NMS

NetworkAgent

NetworkAgent

NetworkObjects

NetworkObjects

Network Management Components

A NMS manages all the components connected to a network which may be coming from different vendors

This might require installing multiple NMS or a single NMS capable of managing multiple vendor components (Interoperability).

Therefore, standards are required (2 major standards emerged: the Internet and OSI)

NMS

NetworkAgent

NetworkAgent

NetworkObjects

NetworkObjects

Interoperability

Vendor A

ApplicationServices

ManagementProtocol

TransportProtocols

Objects

Objects

Vendor B

Objects

Objects

NMSVendor A

NetworkAgent

NetworkAgent

NetworkObjects

NetworkObjects

NMSVendor B

NetworkAgent

NetworkAgent

NetworkObjects

NetworkObjects

Messages

Services & Protocols

Management related applications e.g., fault and configuration management)

Case of two service providers: each managed independently. Some mgnt information can be shared

Distributed Network Management

Centralized management central control (makes

sense when key resources reside in a central site and services are provided to remote users).

Enables managers to maintain control over the entire configuration, balancing resources against needs, and optimizing the overall resource utilization

Drawbacks traffic overhead, scalability

and “single point of failure”

NMA

OSComm

NME Appl

OS

Comm

NME Appl OS

Comm

NME

Router (agent)

Server (agent)

OS

Comm

NME Appl

Manager

Workstation (agent)


Distributed management replaces the single network

control with interoperable workstations located on distributed LANs.

local control for managers over their own segments.

Hierarchical architecture is typically used where a central workstation (with backup) has global access rights and the ability to manage all network resources

Advantages: Traffic overhead is minimized:

much of the traffic is confined to the local environment

Greater scalability: more workstations can be deployed to provide additional management

Eliminate the single “point of failure” by using multiple networked management stations


Management server Management server

Network

Network

Managementapplication


MIB MIB

ProxyProxy

Network resources with management agents (servers, routers, etc.)

Management clients (PCs, workstations)

Devices to be managed

Devices with different management protocols

Each may have access to one or more mgnt servers

Proxies

Ideally, all network components that are to be managed should include a network management entity (NME) with common network management software across all managers and agents.

This may actually not be practical or possible: Proprietary management systems Some components (e.g., modems) may not support

additional software It is common to have agents acting as proxies:

A proxy acts on behalf of other nodes A manager communicates with a proxy to get information

for a specific node

Proxies

Management application

Client stub

Protocol stack

Protocol stack

Proxy manager

Protocol stack

Protocol stack

Serverstub

Client proxystub

Proprietary management interface

Server proxy stub

Standard operations and event reports

Proprietary operations and event reports

Polling and Event Reporting

Information that is useful for monitoring is collected and stored by agents and is made available to one or more manager systems.

Polling and event reporting are two techniques used for this purpose by both network managers and agents.

MANAGER

AGENTS

Polling

MIB

Event Reporting

Polling and Event Reporting

Polling A “request-response”

interaction between a manager and agent.

A query is made by a manager to an authorized agent to request values for various information elements

The agent responds with information from its MIB

The request may take any shape: asking for some specific

values or could be about the structure used for the MIB

Event Reporting the agent initiates, and the

manager acts as a listener waiting for incoming information

A “reporting period” may be defined and configured by the manager

When a significant (unusual) event occurs (e.g., a fault), the agent reports to the manager Reporting is more efficient than

polling, especially for monitoring objects whose values change only infrequently

Polling and Event Reporting A network monitoring system employs both polling and

reporting schemes Traditional TMN relies on event reporting whereas SNMP

relies on polling and OSI falls in between The choice of either depends on number of factors:

Amount of traffic generated Robustness in critical situations Delays in notifying Amount of processing in managed devices Reliable vs. unreliable transport Network monitoring applications supported Robustness of notification devices

ICMP: Internet Control Message Protocol

used by hosts & routers to communicate network-level information error reporting:

unreachable host, network, port, protocol

echo request/reply (used by PING)

network-layer “above” IP: ICMP msgs carried in IP

datagrams ICMP message: type, code

plus first 8 bytes of IP datagram causing error

Type Code description0 0 echo reply (ping)3 0 dest. network unreachable3 1 dest host unreachable3 2 dest protocol unreachable3 3 dest port unreachable3 6 dest network unknown3 7 dest host unknown4 0 source quench (congestion control - not used)8 0 echo request (ping)9 0 route advertisement10 0 router discovery11 0 TTL expired12 0 bad IP header

Traceroute and ICMP

Source sends series of UDP segments (probes) to dest First has TTL =1 Second has TTL=2, etc. Provide also unlikely port

number When nth datagram arrives

to nth router: Router discards datagram And sends to source an

ICMP message (type 11, code 0)

Message includes name of router& IP address

When ICMP message arrives, source calculates RTT

Traceroute does this 3 times

Stopping criterion UDP segment eventually

arrives at destination host Destination returns ICMP

“host unreachable” packet (type 3, code 3)

When source gets this ICMP, stops.

PING and ICMP

PING (Packet Internet Groper) is a simple management tool that depends on ICMP protocol Measure round trip delays,

packet loss, etc. Isolates points of failure

and areas of congestion

Ping, ”Sends ICMP ECHO_REQUEST packets to network hosts”, used to: Test destination reachability, compute round trip time count the # of hops to destination may provide record route option

Ping failure does not guarantee un-reachability Firewalls may filter pings

Origin of NM

Internet currently growth in the number of

attached hosts, number of distinct

administrative domains, multi-vendor equipment,

etc. PING capability was not

satisfactory! need for automated capabilities

Standardized protocols with more functionalities than PING and yet as simple!

SNMP (Simple Network Management Protocol) and CMIP (Common Management Information protocol) over TCP/IP have emerged and were approved by the IAB

NM StandardsStandard Salient Points

OSI / CMIP International standard (ISO / OSI) Management of data communications network - LAN and WAN Deals with all 7 layers Most complete Object oriented Well structured and layered Consumes large resource in implementation

SNMP/Internet Industry standard (IETF) Originally intended for management of Internet components, currently adopted for WAN

and telecommunication systems Easy to implement Most widely implemented

TMN International standard (ITU-T) Management of telecommunications network Based on OSI network management framework Addresses both network and administrative aspects of management

IEEE IEEE standards adopted internationally Addresses LAN and MAN management Adopts OSI standards significantly

Deals with first two layers of OSI

Web-based

Management Web-Based Enterprise Management (WBEM) Java Management Application Program Interface (JMAPI)

NM Standards

OSI (Open System Interconnection) NM Adopted by the ISO (International Standards Organization) Its management protocol is the CMIP (Common Management

Information Protocol) Very comprehensive and addresses the 7 layers of OSI Managed objects are based on object classes and inheritance

rules Management of data communications network - LAN and WAN Complex and consumes large resource in implementation designed 1980’s: too slowly standardized

NM Standards

Simple Network Management protocol (SNMP) Industry standard (IETF) Managed objects are defined as scalars with few characteristics

such as data types, read-only, read-write attributes Originally intended for management of Internet components,

currently adopted for WAN and telecommunication systems Easy to implement Most widely implemented NM: most vendor equipment supports

SNMP

NM Standards

Telecommunication Management Network (TMN)

International Standard (ITU) Based on OSI Network Management Management of telecommunications

networks Addresses both network and

administrative aspects of management

IEEE Adopted Internationally Addresses LAN/MAN

management Based on OSI Network

Management Deals with first two layers of OSI

(physical and data link layers)

NM Standards

Web-based Management Based on Web technology (web servers and browsers) Still an evolving technology Web-Based Enterprise Management (WBEM)

Desktop Management Task Force (DMTF) is actively developing specs for WBEM

DMTF had chosen Microsoft OO management model Java Management Extensions (JMX)

Based on JAVA applets developed by Sun Microsystems

Network Management Models

Organization Model the components of a NM

system, their functions, and relationships (it defines manager, agent, object)

NetworkManagement

InformationModel

OrganizationModel

FunctionalModel

CommunicationModel

Information Model Structure of Management

Information (SMI: Syntax and semantics)

Management Information Base (MIB: Organization of management information)

Network Management Models

Communication Model Transfer syntax with bi-

directional messages; Transfer structure (PDU)

NetworkManagement

InformationModel

OrganizationModel

FunctionalModel

CommunicationModel

Functional Model Application functions

Configure components Monitor components Measure performance Secure information Usage accounting

Organization Model

Managed object A network element that is

managed (e.g., routers, bridges, hubs, etc.)

Houses SNMP management agent

Objects are classified into managed/unmanaged Managed object has a

running management agent

Manager

Managed objects

Unmanaged objects

Two-Tier Network Management Organization Model

Agent process

MDB

MDB Management Database

Organization Model

Management Station (Manager) Interface for network managers to

monitor and control the network Contains management applications

(data analysis, fault recovery, etc.) Translation capabilities from

manager’s requirements into actual monitoring and control of remote elements

Contains DB of information extracted from MIBs of all the managed entities in the Network

Manager

Managed objects

Unmanaged objects


Agent process

MDB


Organization Model

Management Agent Gathers information from objects Configures parameters of objects

(e.g., enable/disable a router port, shut down a port on a hub, etc.)

Responds to requests for information and actions from managers

Generates alarms and sends them to managers

Manager

Managed objects

Unmanaged objects


Agent process

MDB


Organization Model Middle layer plays the dual role

Agent to the top-level manager Manager to the managed

objects collects, processes and stores

data locally Performs statistical operation on

the data and passes it to top level manager

The intermediate system could be at a local site and passes info. to a remote site.

Example of middle level: Remote monitoring agent (RMON)

Agent / Manager

Managed objects

Agent process

Manager

Three-Tier Network Management Organization Model

MDB

MDB


Organization Model

Different network domains, each managed locally Agent NMS manages the domain MoM presents integrated view of domains Domain may be geographical, administrative, vendor-specific

products, etc.

MoM

AgentAgent NMS

Manager

Managed objectsManaged objects

MDB

MDB MDB

MoM Manager of Managers

AgentAgent NMS

Manager

NMS Network Management System

Communication Model

Resources are represented as objects (or data variables) Collection of objects is a MIB (more later) A manager performs monitoring by retrieving the value of MIB

objects A manager causes an action to take place or changes the

configuration settings by modifying values of specific variables

MIB

MANAGERMANAGER AGENTAGENT

SNMP

Communication Model

Management stations and agents are linked by a network management protocol

SNMP is used for the management of TCP/IP networkso Get: manager or management station can retrieve the value of

objects at the agento Set: set the values of objects at the agento Trap: agent notifies manager on significant events

MIB

MANAGERMANAGER AGENTAGENT

SNMP

Protocol Architecture

InternetworkInternetwork

Router

IP

Network-dependent protocols

UDP

SNMP

Agent processAgent process

SNMP

UDPUDP

SNMP


SNMP

UDP UDP

SNMP

Agent processUser process

FTP, etc.

TCP

Host

IP


Host

UDP

SNMP


SNMP

UDP UDP

SNMP

Agent processUser process

FTP, etc.

TCP

IP


IP

UDP

SNMP

Manager process


Management station

Network manager

Central MIB

(e.g., Ethernet, X.25, ATM)

Interprets SNMP messages and controls the agent’s MIB

-SNMP uses UDP port 161- connection-less

Communication Model

Management data is communicated between agent and manager as well as between managers

Three aspects: Transport medium of message exchange (transport protocol) Message format (application protocol) Actual message (commands and responses)

Manager Agent

Operations /Requests

Responses

Notifications /TrapsApplications Network Elements

Managed Objects

Management Message Communication Model

Communication ModelG

etR

eque

st

Get

Nex

tReq

uest

SetR

eque

st

Get

Res

pons

e

Trap

Layer 1 & 2

IP

SNMP Manager

UDP

Layer 1 & 2

IP

SNMP Agent

UDP

Network

Get

Req

uest

Get

Nex

tReq

uest

SetR

eque

st

Get

Res

pons

e

Trap


SNMP managedobjects

Application

manages object

SNMP Messages

Central MIB

Trap-Directed Polling SNMP encourages the

manager to use trap-directed polling A manager may be

responsible for a large number agents, each maintains a large number of managed objects

It is impractical to regularly poll all agents for all their readable objects (management overhead on the network may be very excessive!)

agent data

agent data

agent data

agent data

managed device

managed device

managed device

managed device

managingentity data

networkmanagement

protocol

managing entity

Trap-Directed Polling Initially a manager may poll

all the agents for some key information e.g., interface

characteristics (# pckts in/out, etc..)

Then, each agent is responsible for notifying (through trap messages) the manager of any unusual event e.g., high pckt drop rate at

some interface

agent data

agent data

agent data

agent data

managed device

managed device

managed device

managed device

managingentity data

networkmanagement

protocol

managing entity

Substantial savings in network capacity and agent processing (use network resources for the right reason!)

Information Model The representation of

objects and information relevant to their management

This information is usually communicated between agents and management processes

SMI (Structure of Management Information) defines the syntax and semantics of management information stored in MIB (Management Information Base)

ExamplesysDescr: { system 1 }Syntax: OCTET STRINGDefinition: "A textual description of the entity. "Access: read-onlyStatus: mandatory

MIB Contains information about objects Organized by grouping of related objects Defines relationship between objects Agent MIB vs. Manager MIB

MIB Agent: local information MIB Manager: info. on all network

components

Information Model MDB physical database; e.g.. Oracle

Contains measured or administratively configured values of NEs

MIB virtual database; schema compiled into management software Info necessary for processes to

exchange info. (e.g., #ports/hub) A NMS can automatically discover

(periodic broadcast of PING messages) a managed object, such as a hub, when added to the network Once detected, its information (e.g.,

address, number of ports, etc.) is added to MDB

MIB does not need to be updated if another hub from same vendor already exist

Manager

Managed objects

MDB MIB

The NMS can identify a new added object only after the MIB schema of the new added object is compiled into manager MIB.

Management Information Tree Both Internet and OSI

define objects uniquely by a tree structure

Each managed object occupies a node in the tree underneath the root

Root

Level 1

Level 2

Level 3

Management Information Tree Managed Objects

Standard organizations: definemanagement of objects under them

iso-itu2

itu0

iso1

org3

dod6

internet1

OSI Management Information Tree

Designation of objects: iso 1 org 1.3 dod 1.3.6 internet 1.3.6.1

Object Type and Instance

object ID unique IDand descriptor and name for the objectsyntax used to model the objectaccess access privilege to a managed

object (read-only, etc)status implementation requirements

(e.g., optional or mandatory)definition textual description of the

semantics of object type

Object Type:Object ID and

Descriptorcircle

Access:Access

privilege

Definition:Semantics -

textual description

Status:Implementationrequirements

Syntax :model of object

Internet Perspective


object class managed objectattributes attributes visible at its

boundaryoperations access operations that can

be applied to itbehavior behavior exhibited by it in

response to an operationNotifications notifications emitted by

the object

Behavior

Object Class:Circularobject

Obj

ect C

lass

:E

llipt

ical

obje

ct

Attributes::

circle, dimension

Operations:Push

Attributes:ellipse, dimension

Notifications:

Notify changes in attribute values

OSI Perspective


Characteristics Example Object type PktCounter

Syntax Counter

Access Read-only

Status Mandatory

Description Counts number of packets

Internet Perspective

Characteristics Example Object class Packet Counter

Attributes Single-valued

Operations get, set

Behavior Retrieves or resets values

Notifications Generates notifications on new value

OSI Perspective

Packet Counter As Example of Managed Object

Function Model

Configuration management set and change network configuration and component parameters Set up alarm thresholds

Fault management Detection and isolation of failures in network Trouble ticket administration

Performance management Monitor performance of network

Security management Authentication Authorization Encryption

Accounting management Functional accounting of network usage

OSIFunctional Model

FaultManagement

ConfigurationManagement

PerformanceManagement

SecurityManagement

AccountingManagement

Abstract and Transfer Syntaxes

TransferSyntax

Encoding Rules

Encoding Rules

LocalMapping

LocalStorage

Data Transfer Compone

nt

Data Transfer Compone

nt

Application

Component

Application

ComponentLocal

Storage

LocalMapping

User PresentationMapping

User User

AbstractSyntax

The user of data transfer comp. e.g., SNMP, FTP, TELNET for TCP/IP

Mechanisms for transferof data between end systems (e.g., TCP or UDP)

Binary representation of data

User is concerned with semantics of data

Concerned with syntax of data

Abstract and Transfer Syntaxes For the application component, information is presented in

an abstract syntax that deals with data types and data values

o Abstract syntax is the set of rules used to specify data types and structures for storage of information

Abstract syntax is used to exchange info. between application components in systems

o Makes application layer protocols independent of lower layer protocols

Abstract syntax must be mapped into some form for presentation to the human user

And to some local format for storage (e.g. of this mapping is in the case of MIB; however, elements within MIB are defined using abstract syntax)

Abstract and Transfer Syntaxes The transfer syntax defines a unified representation of the

data to be exchanged between data transfer componentso Transfer syntax represents the set of rules for communicating

information between systems

Mapping from abstract syntax to transfer syntax is accomplished by means of encoding

o A common representation for the exchange of data between different systems

o Can generate machine-readable code: Basic Encoding Rules (BER) is used in management modules

ASN.1 is based on the Backus system and uses the formal syntax and grammar of the Backus-Nauer Form (BNF) ASN.1 is independent from lower layer protocols

Backus-Nauer Form (BNF)

Definition: <name> ::= <definition> where <entity> denotes “entity” and the symbol “::=“ represents “defined as” primitive definitions:

<digit> ::= 0|1|2|3|4|5|6|7|8|9<op> ::= +|-|x|/

similarly, an entity number can be constructed from primitives:

<number> ::= <number> | <digit> <number>Example:

9 is primitive 919 is construct of 1 and 9619 is construct of 6 and 19

ASN.1 Assignments

Assignments <BooleanType> ::= BOOLEAN data type assignment (or

name of the entity) <BooleanValue> ::= TRUE | FALSE value assignment

(assigned value to the data type)

Group of assignments: Modules Start with capital letters Usually modules are built from primitive (atomic) data types (e.g.,

INTEGER, REAL, etc..) May use ASN.1 constructs (e.g., SET, SEQUENCE, etc.) Constructors are used to build structured data types Backward and forward references, and inline definition

A module PersonnelRecord(a set of data types)

ASN.1 Modules

Three construction mechanisms (develop structured data types):Alternatives: CHOICEList: SET and SEQUENCERepetition: SET OF and SEQUENCE OF

PersonnelRecord ::= SET { Name, title GraphicString, division CHOICE { marketing [0] SEQUENCE {Sector, Country}, research [1] CHOICE {product-based [0] NULL, basic [1] NULL}, production [2] SEQUENCE {Product-line, Country } }}

Primitives data types

Constructs: “list makers”

Construct: alternatives

PersonnelRecord is a set of different data types, each uniquely associated with a name and can be encoded and transmitted in any order.

ASN.1 Modules

Example:“Smith”, “Manager”, {“North”, “Chile”}“Manager”, “Smith”, {“North”, “Chile”}{“North”, “Chile”}, “Smith”, “Manager”


Lists built with “SEQUENCE” maintains the correct order

ASN.1 Symbols

Symbol Meaning::= Defined as| or, alternative, options of a list- Signed number-- Following the symbol are comments{} Start and end of a list[] Start and end of a tag() Start and end of subtype.. Range

Data Types

Data Types

Convention

Example

Object name Initial lowercase letter sysDescr, etherStatsPkts

Application data type Initial uppercase letter Counter, IpAddress

Module Initial uppercase letter PersonnelRecord

Macro, MIB module All uppercase letters RMON-MIB

Keywords All uppercase letters INTEGER, BEGIN

Data types are generally defined based on a structure and a tag: Structure: simple (or atomic), structured, etc.. Tag: class and a tag

ASN.1 simple types Basic Types

o BOOLEANo INTEGERo ENUMERATEDo REALo BIT STRINGo OCTET STRING

Character String Types (various subsets of ISO 10646-1)o NumericString (0-9,<space>)o PrintableString (0-9,A-Z,a z,<space>,<special>)o VisibleStringo GraphicStringo TeletexStringo UTF8Stringo IA5String

ASN.1 simple types Syntax : <type name> ::= type Example: counter ::= INTEGER IpAddress ::= OCTET STRING PageNumber ::= INTEGER ChapterNumber::= INTEGER

Months ::= ENUMERATED {january (1), february (2),

march (3), april (4), may (5), june (6), july (7 august (8), september (9), october (10), november (11), december (12)}

ASN.1 simple types A subtype is derived from a parent type

Syntax: <subtype name> ::= <type> ( <constraint> )

Examples:

Counter ::= INTEGER ( 0..4294967295 )

IpAddress ::= OCTET STRING ( SIZE(4) )

Spring ::= Months ( march | april | may )

Summer ::= Months ( june | july | august )

SmallPrime ::= INTEGER ( 2 | 3 | 5 | 7 | 11 )

ASN.1 structured types A data type is structured type when it contains other types (i.e.,

have components) BookPageNumber ::= SEQUENCE

{ChapterNumber, Separator, PageNumber}

separator is a VisibleString data type with value “-”

Example: {1-1, 2-3, 3-39} BookPages ::= SEQUENCE OF { BookPageNumber }

BookPages ::= SEQUENCE OF {

SEQUENCE

{ChapterNumber, Separator, PageNumber}} Example: {1-1, 1-2,..,2-1, 2-2,…..}

ASN.1 structured types The pages of a book could also be specified as a

collection of individual pages in random order

BookPages ::= SET OF{ SEQUENCE {ChapterNumber, Separator, PageNumber}}

ASN.1 Tagged Types Tag uniquely identifies a data type and is required for

encoding the data types for communication Comprises class and tag number Class:

o Universal - similar to global variableso Application - only in the application usedo Context-specific - specific context in applicationo Private - used extensively by commercial vendors

Example: BOOLEAN Universal 1 INTEGER Universal 2 research Application [1]

product-based Context-specific under research [0]

ASN.1 Tagged Types

- basic types

- object types

- character string types

- miscellaneous types

- structured types

UNIVERSAL 1

UNIVERSAL 3

UNIVERSAL 9 UNIVERSAL 10

BOOLEAN

BIT STRING

REAL ENUMERATED

UNIVERSAL 2 INTEGER

UNIVERSAL 4 OCTET STRING

UNIVERSAL 6

UNIVERSAL 7 ObjectDescriptor

OBJECT IDENTIFIER

UNIVERSAL 5 NULL

UNIVERSAL 23 UTCTime

UNIVERSAL 24 GeneralizedTime

UNIVERSAL 16 SEQUENCE [OF] UNIVERSAL 17 SET [OF]

UNIVERSAL 26 VisibleString . . .

ASN.1 Tagged Types

Context specific (subset of an application, and limited to the application)

Tag nb is 1 (overrides that of BOOLEAN)

Application specific


ASN.1 Object Types Used to name and describe information objects

Such as standard documents, data structures, managed objects In general, an information object is a class of information,

e.g., file format, rather than an instance of such a class (i.e., individual file)

Object identifier is a unique identifier for a particular object and its value consist of a set of integers

Object descriptor is a human readable description of an information object

ASN.1 Object Types

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

root

ccitt(0) iso(1) joint-iso-ccitt(2)

org(3)

dod(6)internet(1)

private(4)mgmt(2)experimental(3)

enterprise(1)mib-2(1)

private OBJECT IDENTIFIER ::= {internet 4 }

ASN.1 Object Types

Private type is used extensively by vendors of network products

A vendor is assigned a node on the MIT, all branches and leaves under that node will be assigned private data types by the vendor

iso-itu2

iso1

itu0

org3

dod6

internet1

private4

enterprise1

IBM2

ibm OBJECT IDENTIFIER ::= {iso(1) org(3) dod(6) internet(1) private(4) enterprize(1) 2}

Encoding Structure

ASN.1 syntax containing management information is encoded using the Basic Encoding Rules (BER) that is defined for the transfer syntax

BER is a specification developed and standardized by CCITT and OSI

ASCII data is converted to bit-oriented data

TLV, Type-Length-Value: is a specific encoding structure Type: indicates the ASN.1 type, class of the type Length: length of the actual value representation Value: the value of the ASN.1 type as a string of octets

Encoding Structure

P/C (1-bit) specifies whether the structure is simple or a construct 0 for simple 1 for construct

Type Length Value

Class(7-8th bits)

P/C(6th bit)

Tag Number(1-5th bits)

1 byte

Encoding Structure

Class (2 bits): specifies the class being used

Type Length Value

Class(7-8th bits)

P/C(6th bit)


1 byte

Class 8th bit 7th bit Universal 0 0 Application 0 1 Context-specific 1 0 Private 1 1

Universal class Primitive Tag value = 2

Encoding Structure

Tag Number: designates the tag value in binary

Example: 00 0 00010 for encoding INTEGER

Type Length Value

Class(7-8th bits)

P/C(6th bit)


1 byte

Tag number < 31

Class P/C Tag number

0 = Primitive1 = Constructed

0 0 = Universal0 1 = Application1 0 = Context-specific1 1 = Private

8 7 6 5 4 3 2 1Bits

Identifier Octet

Tag number >= 31

Class P/C 1 1 1 1 11 1 1 1 1

Leading octet

1

2nd octet

1 0

Last octet

. . .

+ +. . . +

= Tag number

Encoding of Length Field

Binary equivalent of 128

Short form ( L < 128 octets)

0 Length L

one octet

Contents (or Value) field

L octets

Long form ( 128 L < 21008 octets)

1 K

first octet

Length L

K octets

Contents field

L octets

Example, L = 128: 10000001 10000000

BER, Examples

distance INTEGER ::= 27

00 0 00010

UNIVERSAL P 2

today INTEGER ::= 129 02 02 00 81 Length is 2 to indicate 2 octets for Value

DayOfYear ::= [APPLICATION 17] IMPLICIT INTEGER

01 0 10001

APPLICATION P 17

51 02 00 81today DayOfYear ::= 129

02 01 1BType Length Value

BER, Examples

BER EncodingBirthday Length Contents30 ?? VisibleString Length Contents 1A 04 "Jane" DayOfYear Length Contents 51 02 00 81

Birthday ::= SEQUENCE {name VisibleString,day DayOfYear

}

Type Definition

myBirthday Birthday ::= {name "Jane",day 129

}

Value Assignment

0A

UNIVERSAL 1600 1 10000

MACROS Macro is used to create new data types

<macroname> MACRO ::= BEGIN TYPE NOTATION ::= <syntaxOfNewType> VALUE NOTATION ::= <syntaxOfNewValue> <auxiliaryAssignments> END

OBJECT-IDENTITY MACRO ::=

BEGIN TYPE NOTATION ::= “STATUS” Status “DESCRIPTION” Text

VALUE NOTATION ::= Value (VALUE OBJECT IDENTIFIER) Status ::= “current” | “deprecated” | “obsolete” Text ::= ““““ string ””””

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inse7120 OBJECT-IDENTITY

STATUS current

DESCRIPTION "A graduate-level

network management course offered

by the CIISE at Concordia University."

::= {ciiseclasses 50}

network management concepts: models and languages * * mani subramanian “network management:...

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