Transcript Manager - Telkom University

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
(ASN.1)
 Basic Encoding Rules, BER
1
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
Network
control host
(Manager)
Server
(agent)
NMA
NME Appl
NME Appl
Comm
OS
Comm
OS
Router
(agent)
Workstation
(agent)
NME
Comm
NME Appl
Comm
OS
OS
Elements of NMS
 Network Management
Entity (NME)
o
o
o
o
Collect statistics on
communication and related
activities
Store statistics locally
Responds to commands
from the network control
center (e.g. report its object
status, etc.)
Generate messages to the
network control center when
local conditions change
(e.g., port failure)
 Network Management
Application (NMA)
o
o
Interface allowing
authorized users to manage
the network
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
Network
Agent
Network
Agent
Network
Objects
Network
Objects
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
Network
Agent
Network
Agent
Network
Objects
Network
Objects
Interoperability
Management related applications
e.g., fault and configuration
management)
Application
Services
Objects
Objects
Management
Protocol
Vendor A
Vendor B
Objects
Objects
Transport
Protocols
Case of two service providers: each
managed independently. Some mgnt
information can be shared
NMS
Vendor A
Messages
Services & Protocols
NMS
Vendor B
Network
Agent
Network
Agent
Network
Agent
Network
Agent
Network
Objects
Network
Objects
Network
Objects
Network
Objects
Distributed Network Management
Manager
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
NME Appl
Comm
OS
Server
(agent)
NME Appl
Comm
OS
Router
(agent)
Workstation
(agent)
NME
Comm
NME Appl
Comm
OS
OS
Distributed Network Management
Distributed management
Advantages:
 replaces the single network
 Traffic overhead is minimized:
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
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
Distributed Network Management
Management clients
(PCs, workstations)
Each may have access
to one or more mgnt
servers
Network
Management server
Management server
Management
application
Management
application
MIB
Network
Devices with different
Devices
to
management
protocols
be managed
Proxy
Network resources with
management agents
(servers, routers, etc.)
Proxy
MIB
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
Proprietary
management interface
Proxy manager
Client
stub
Server
stub
Protocol
stack
Protocol
stack
Standard operations
and event reports
Client proxy
stub
Protocol
stack
Server proxy
stub
Protocol
stack
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.
MANAGER
AGENTS

Polling and event
reporting are two
techniques used for this
purpose by both network
managers and agents.
MIB
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
Network Management Concepts: Models
and Languages
 Network Management Systems
 Origin of Network Management
 OSI Management Models
 Organization
 Information
 Communication
 Functional
 Abstract
Syntax
Notation
(ASN.1)
 Basic Encoding Rules, BER
1
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
0
3
3
3
3
3
3
4
Code
0
0
1
2
3
6
7
0
8
9
10
11
12
0
0
0
0
0
description
echo reply (ping)
dest. network unreachable
dest host unreachable
dest protocol unreachable
dest port unreachable
dest network unknown
dest host unknown
source quench (congestion
control - not used)
echo request (ping)
route advertisement
router discovery
TTL expired
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 Standards
Standard
OSI / CMIP
Salient Points







SNMP/Internet




TMN




IEEE




Web-based
Management


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
Industry standard (IETF)
Originally intended for management of Internet components, currently adopted for WAN
and telecommunication systems
Easy to implement
Most widely implemented
International standard (ITU-T)
Management of telecommunications network
Based on OSI network management framework
Addresses both network and administrative aspects of management
IEEE standards adopted internationally
Addresses LAN and MAN management
Adopts OSI standards significantly
Deals with first two layers of OSI
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)
IEEE
Adopted Internationally

International Standard (ITU)

Based on OSI Network Management
Addresses LAN/MAN management
Management of telecommunications
networks
Based on OSI Network
Management
Addresses both network and
administrative aspects of
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 Concepts: Models
and Languages
 Network Management Systems
 Origin of Network Management
 OSI Management Models
 Organization
 Information
 Communication
 Functional
 Abstract
Syntax
Notation
(ASN.1)
 Basic Encoding Rules, BER
1
Network Management Models
Network
Management
Organization
Model
Information
Model
Organization Model

the components of a NM
system, their functions, and
relationships (it defines
manager, agent, object)
Communication
Model
Functional
Model
Information Model
 Structure of Management
Information (SMI: Syntax
and semantics)
 Management Information
Base (MIB: Organization of
management information)
Network Management Models
Network
Management
Organization
Model
Information
Model
Communication Model

Transfer syntax with bidirectional messages;
Transfer structure (PDU)
Communication
Model
Functional
Model
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
MDB
Manager
Managed objects
Unmanaged objects
Objects are classified into
managed/unmanaged

Managed object has a
running management agent
MDB Management Database
Agent process
Two-Tier Network Management Organization Model
Organization Model
Management Station (Manager)




Interface for network managers to
monitor and control the network
MDB
Manager
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
Managed objects
Unmanaged objects
MDB Management Database
Agent process
Two-Tier Network Management Organization Model
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
MDB
Manager
Managed objects
Unmanaged objects
MDB Management Database
Agent process
Two-Tier Network Management Organization Model
Organization Model

Middle layer plays the dual role

Agent to the top-level manager

Manager to the managed
objects




MDB
Manager
MDB
Agent / Manager
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)
Managed objects
MDB Management Database
Agent process
Three-Tier Network Management Organization Model
Organization Model
MoM Manager of Managers
NMS Network Management System
MoM
MDB
Agent
Agent
Agent NMS
Agent NMS
MDB
Manager
Managed objects
MDB
Manager
Managed objects
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.
Communication Model
SNMP
MANAGER
MIB
AGENT
 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
Communication Model
SNMP
MANAGER
MIB
AGENT
 Management stations and agents are linked by a network
management protocol
 SNMP is used for the management of TCP/IP networks
o
o
o
Get: manager or management station can retrieve the value of
objects at the agent
Set: set the values of objects at the agent
Trap: agent notifies manager on significant events
Protocol Architecture
Management station
Network
manager
Host
Agent
process
Agent
process
Manager process
-SNMP uses UDP
port 161
- connection-less
SNMP
Central
MIB
UDP
Network-dependent (e.g., Ethernet, X.25, ATM)
protocols
Host
UDP
UDP
TCP
UDP
Network-dependent protocols
Agent
process
Agent
process
FTP, etc.
SNMP
SNMP
TCP
UDP
UDP
UDP
FTP, etc.
SNMP
Router
Agent
Userprocess
process
SNMP
SNMP
IP
IP
Agent
process
Agent
process
Agent
Userprocess
process
Internetwork
Internetwork
IP
Network-dependent protocols
UDP
UDP
IP
Network-dependent
protocols
Interprets SNMP
messages
and controls the
agent’s MIB
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)
Operations /
Requests
Manager
Applications
Responses
Agent
Notifications /
Traps
Network Elements
Managed Objects
Management Message Communication Model
Communication Model
SNMP Manager
Application
SNMP Messages
SNMP Agent
UDP
UDP
IP
IP
Layer 1 & 2
Networ
k
Trap
GetResponse
Central
MIB
SetRequest
manages object
GetNextRequest
SNMP managed
objects
GetRequest
Trap
GetResponse
SetRequest
GetNextRequest
GetRequest
Management
application
Layer 1 & 2
Trap-Directed Polling

SNMP encourages the
manager to use trapdirected 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!)
managing entity
managing
data
entity
agent data
managed device
agent data
network
management
protocol
managed device
agent data
agent data
managed device
managed device
Trap-Directed Polling

Initially a manager may poll
all the agents for some key
information


e.g., interface
characteristics (# pckts
in/out, etc..)
managing entity
managing
data
entity
network
Then, each agent is
management
responsible for notifying
protocol
(through trap messages)
the manager of any unusual
event
agent data

e.g., high pckt drop rate at
some interface
agent data
managed device
agent data
managed device
agent data
managed device
managed device
 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)
Example
sysDescr:
{ system 1 }
Syntax:
OCTET STRING
Definition: "A textual
description of the entity. "
Access:
read-only
Status:
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


MDB
Manager
MIB
MIB virtual database; schema compiled
into management software


Contains measured or administratively
configured values of NEs
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


Managed objects
Once detected, its information (e.g.,
 The NMS can identify a new
address, number of ports, etc.) is added
added object only after the
to MDB
MIB schema of the new
MIB does not need to be updated if
another hub from same vendor already
added object is compiled
exist
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
 Designation of objects:
iso
1
org
1.3
dod
1.3.6
internet
1.3.6.1
Root
itu
0
Level 1
Level 2
Standard organizations: define
management of objects under them
iso-itu
2
org
3
dod
6
Level 3
Management Information Tree
iso
1
Managed Objects
internet
1
OSI Management Information Tree
Object Type and Instance
Access:
Access
privilege
object ID
Object Type:
Object ID and
Descriptor
circle
unique ID
and descriptor and name for the object
syntax
used to model the object
access
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
Status:
Implementation
requirements
Syntax :
model of object
Definition:
Semantics textual description
Internet Perspective
Object Type and Instance
object class managed object
attributes
attributes visible at its
boundary
operations access operations that can
be applied to it
behavior
behavior exhibited by it in
response to an operation
Notifications notifications emitted by
the object
Object Class:
Circular
object
Operations:
Push
:
Attributes:
circle, dimension
Behavior
Object Class:
Elliptical
object
Notifications
:
Notify changes in
attribute values
Attributes:
ellipse, dimension
OSI Perspective
Object Type and Instance
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
OSI
Functional Model
Configuration
Management



Monitor performance of network
Security management




Detection and isolation of failures in network
Trouble ticket administration
Performance management


Security
Management
Accounting
Management
set and change network configuration and component parameters
Set up alarm thresholds
Fault management


Performance
Management
Configuration management


Fault
Management
Authentication
Authorization
Encryption
Accounting management

Functional accounting of network usage
Network Management Concepts: Models
and Languages
 Network Management Systems
 Origin of Network Management
 OSI Management Models
 Organization
 Information
 Communication
 Functional
 Abstract
Syntax
Notation
(ASN.1)
 Basic Encoding Rules, BER
1
Abstract and Transfer Syntaxes
User is concerned with
semantics of data
User
The user of data transfer
comp. e.g., SNMP, FTP,
TELNET for TCP/IP
User Presentation
Mapping
Application
Mapping Component
Local
Local
Storage
Mechanisms for transfer
of data between end
systems (e.g., TCP or UDP)
User
Abstract
Syntax
Application
Component
Encoding
Rules
Data
Transfer
Component
Transfer
Syntax
Concerned with syntax of data
Local
Mapping
Encoding
Rules
Data
Transfer
Component
Binary representation of data
Local
Storage
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 components
o
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
o
A common representation for the exchange of data between
different systems
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 9
 19 is construct of 1 and 9
 619 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
ASN.1 Modules
PersonnelRecord ::= SET
Constructs: “list makers”
Name,
{
GraphicString,
title
division CHOICE {
A module PersonnelRecord
[0] SEQUENCE
marketing
(a set of data types)
{Sector,
Primitives data types
Country},
[1] CHOICE
research
{product-based [0] NULL,
Construct: alternatives
[1] NULL},
basic
[2] SEQUENCE
production
{Product-line,
}}
Country }
Three construction mechanisms (develop structured data
types):
Alternatives: CHOICE
List:
SET and SEQUENCE
Repetition: SET OF and SEQUENCE OF
ASN.1 Modules
PersonnelRecord ::= SET
Lists built with “SEQUENCE”
{
Name,
maintains the correct order
title
GraphicString,
division CHOICE {
PersonnelRecord is a set of
marketing
[0] SEQUENCE
different data types, each uniquely
{Sector,
associated with a name and can
Country},
be encoded and transmitted
research
[1] CHOICE
in any order.
{product-based [0] NULL,
basic
[1] NULL},
production
[2] SEQUENCE
{Product-line,
Country }
}}
Example:
“Smith”, “Manager”, {“North”, “Chile”}
“Manager”, “Smith”, {“North”, “Chile”}
{“North”, “Chile”}, “Smith”, “Manager”
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
o
o
o
o
o
BOOLEAN
INTEGER
ENUMERATED
REAL
BIT STRING
OCTET STRING
 Character String Types (various subsets of ISO 10646-1)
o
o
o
o
o
o
o
NumericString
(0-9,<space>)
PrintableString (0-9,A-Z,a z,<space>,<special>)
VisibleString
GraphicString
TeletexString
UTF8String
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
o
o
o
Universal - similar to global variables
Application - only in the application used
Context-specific - specific context in application
Private - used extensively by commercial vendors
Example:
BOOLEAN
INTEGER
research
product-based
Universal 1
Universal 2
Application [1]
Context-specific under research [0]
ASN.1 Tagged Types
UNIVERSAL 1
BOOLEAN
UNIVERSAL 2
INTEGER
UNIVERSAL
3 BIT STRING
- basic types
UNIVERSAL 4
OCTET STRING
UNIVERSAL 9
REAL
UNIVERSAL 10 ENUMERATED
UNIVERSAL 6
OBJECT IDENTIFIER
- object types
UNIVERSAL 7
ObjectDescriptor
UNIVERSAL
26string
VisibleString
- character
types
UNIVERSAL 5
...
NULL
UNIVERSAL
23 UTCTime
- miscellaneous
types
UNIVERSAL 24 GeneralizedTime
UNIVERSAL
16 types
SEQUENCE [OF]
- structured
UNIVERSAL 17 SET [OF]
ASN.1 Tagged Types
PersonnelRecord ::= SET
{
Name,
title
GraphicString,
division CHOICE {
marketing
[0] SEQUENCE
Tag nb is 1 (overrides
{Sector,
that of BOOLEAN)
Country},
research
[1] CHOICE
{product-based [0] NULL,
Application specific
basic
[1] NULL},
production
[2] SEQUENCE
{Product-line,
Context specific (subset of
Country }
}}
an application, and limited
to the application)
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
root
ccitt(0)
iso(1)
joint-iso-ccitt(2)
org(3)
internet(1)
mgmt(2)
mib-2(1)
dod(6)
private(4)
experimental(3)
enterprise(1)
internet OBJECT IDENTIFIER ::= {iso(1) org(3) dod(6) 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
i tu
0
is o
1
o rg
3
dod
6
i n te rn e t
1
p riv a te
4
e n te rp ri s e
1
ibm OBJECT IDENTIFIER ::= {iso(1) org(3) dod(6)
internet(1) private(4) enterprize(1) 2}
IB M
2
i s o -i tu
2
Network Management Concepts: Models
and Languages
 Network Management Systems
 Origin of Network Management
 OSI Management Models
 Organization
 Information
 Communication
 Functional
 Abstract
Syntax
Notation
(ASN.1)
 Basic Encoding Rules, BER
1
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
Type
Class
(7-8th bits)
Length
P/C
(6th bit)
Value
Tag Number
(1-5th bits)
1 byte
 P/C (1-bit) specifies whether the structure is
simple or a construct


0 for simple
1 for construct
Encoding Structure
Type
Class
(7-8th bits)
Length
P/C
(6th bit)
Value
Tag Number
(1-5th bits)
1 byte
 Class (2 bits): specifies the class being used
Class
Universal
Application
Context-specific
Private
th
8 bit
0
0
1
1
th
7 bit
0
1
0
1
Encoding Structure
Type
Class
(7-8th bits)
Length
P/C
(6th bit)
Value
Tag Number
(1-5th bits)
1 byte
 Tag Number: designates the tag value in binary
 Example: 00 0 00010 for encoding INTEGER
Universal class
Primitive
Tag value = 2
Tag number < 31
Identifier Octet
Bits
8
7
Class
6
5
P/C
4
3
2
Tag number
0 = Primitive
1 = Constructed
0 0 = Universal
0 1 = Application
1 0 = Context-specific
1 1 = Private
1
Tag number >= 31
Leading octet
Class P/C 1 1 1 1 1
2nd octet
1
Last octet
...
1
+ ... +
= Tag number
0
+
Encoding of Length Field
 Short form ( L < 128 octets)
one octet
L octets
0
Length L
Contents (or Value) field
 Long form ( 128  L < 21008 octets)
first octet
1
K
K octets
L octets
Length L
Contents field
Example, L = 128: 10000001 10000000
Binary equivalent of 128
BER, Examples
distance
INTEGER
::= 27
Type
Length
Value
02
01
1B
00 0 00010
UNIVERSAL P
today INTEGER ::= 129
02
02
2
00 81
Length is 2 to
indicate 2 octets
for Value
DayOfYear ::= [APPLICATION 17] IMPLICIT INTEGER
today DayOfYear ::= 129
51
02
01 0 10001
APPLICATION
P
17
00 81
BER, Examples
Birthday
::= SEQUENCE {
name
VisibleString,
day
DayOfYear
}
myBirthday Birthday ::= {
name
"Jane",
day
129
}
Birthday Length Contents
30
??
0A
VisibleString
1A
DayOfYear
51
Type Definition
UNIVERSAL 16
00 1 10000
Value Assignment
BER Encoding
Length Contents
04
"Jane"
Length Contents
02
00 81
MACROS
 Macro is used to create new data types
<macroname> MACRO ::=
BEGIN
TYPE NOTATION ::= <syntaxOfNewType>
VALUE NOTATION ::= <syntaxOfNewValue>
<auxiliaryAssignments>
END
OBJECT-IDENTITY MACRO ::=
BEGIN
inse7120 OBJECT-IDENTITY
TYPE NOTATION ::=
“STATUS”
Status
“DESCRIPTION”
Text
VALUE NOTATION ::=
Value (VALUE OBJECT IDENTIFIER)
Status ::= “current” | “deprecated” | “obsolete”
Text
END
::= ““““ string ””””
STATUS
current
DESCRIPTION
"A graduate-level
network management course offered
by the CIISE at Concordia University."
::= {ciiseclasses 50}