NETWORK MANAGEMENT SYSTEMS
UNIT-I
1.1 Syllabus
Data communications and Network Management Overview : Analogy of Telephone Network
Management, Communications protocols and Standards, Case Histories of Networking and Management,
Challenges of Information Technology Managers, Network Management: Goals, Organization, and
Functions, Network and System Management, Network Management System Platform, Current Status and
future of Network Management.
1.2 Objectives:
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Learn about data communications and networks
Learn about telephone networks and data networks
Understand the usage of different protocols and standards
Learn the case histories of network management
Understand the functionalities and goals of network management
Learn about the different platforms of NMS
Analogy of Telephone Network Management
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The reason for reliability, dependability and quality is more than the careful
planning, design and implementation of a good telephone network using good and
reliable components. The key is the management and operations of the network.
The architecture of the telephone network is hierarchical. There are five levels of
network switches and three types of trunks that connect these switches.
A trunk is a logical link between two switches that my traverse one or more
physical links.
The direct distance dialing (DDD) network which enables us to dial the far-end
telephone without an operator’s assistance, comprises three transmission trucks.
A direct trunk connects two end offices, a toll-connecting trunk connects an end
office to any too office, and a toll trunk connects any two toll offices.
A circuit connection is setup either directly using a local trunk or via the higher
level switches and routes. Primary and secondary routes are already programmed
into the switch. If the primary route is broken or the facilities over the primary
routes are filled to capacity, an alternative route is automatically assigned.
Operations support systems ensure the quality of service in the telephone network.
(bandwidth, traffic at switches)
For a given region, there is a network operations center (NOC) where the global
status of the network is monitored.
The telephone network is managed from the user’s prospective, not that of the
system or service provider, even through the objective of both are the same.
To manage a network remotely, i.e., to monitor and control the network
components from a central location, network management functions need to be
considered in building the components of the network.
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The computer communication network, however, has not matured to the same
extent as the telephone network. The data communication technology is still
evolving and as merging with telephone technology.
Regional Center
Class 1 switch
Regional Center
Class 1 switch
Sectional Center
Class 2 switch
Sectional Center
Class 2 switch
Primary Center
Class 3 switch
Primary Center
Class 3 switch
Toll Center
Class 4 switch
Toll Center
Class 4 switch
End Office
Class 5 switch
End Office
Class 5 switch
To other
Regional centers
Sectional centers
Primary centers
Toll centers
End offices
To other
Primary centers
Toll centers
End offices
To other
Class 4 toll points
End offices
Legend:
Loop
Direct Trunk
Toll-Connecting Trunk
Voice
Toll Trunk
Voice
Figure 1.1 Telephone Network Model
Communications Protocols and Standards.
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Architecture can be defined as the basic structure of a system that shows its
functional components and the relationships among them.
Communication architecture describes the functional components of a
communication network, as well as the operational interfaces among them.
Operational procedures – both intra and inter modules- are specified in terms of
protocols.
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Communication Architectures.
User A
User Z
Peer-Protocol Interface
Application Layers
Application Layers
Transport Layers
Transport Layers
Physical Medium
(a) Direct Communication between End Systems
System A
Intermediate system
System Z
User A
User Z
Peer-Protocol Interface
Application Layers
Application Layers
Transport Layer
Transport Layers
Transport Layers
Conversion
Physical Medium
Physical Medium
(b) Communication between End Systems via an Intermediate System
Figure 1.11 Basic Communication Architecture
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Each system can be divided into two broad sets of communication layers. The
top set of layers consists of the application layers and the bottom set of the
transport layers.
Direct communication occurs between the corresponding co-operation layers
of each system. Thus transport layers can exchange information, and so can
the application layers and the users.
The end systems communicating via an intermediate system N, which enables
the use of different physical media for the two end systems. System N
converts the transport-layer information into the appropriate protocols. Thus,
system A could be on a copper-wire LAN and system z could be on a fiberoptic cable.
The International standards organization (ISO) has developed a highly
modular, or layered, architecture for communication protocols that is called
the open systems interconnection (OSI) Reference Model, published as
OSIRM-ISO7498.
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This model was developed based on premise that the different layers of
protocol provide different services, and that each layer can communicate with
only its own neighboring level.
Layers 1 through 4 are the transport system protocol layers and layers 5,6 and
7 are application support protocol layers.
The OSI protocol layers
User / Application program
Layer 7
Application
Layer 6
Presentation
Layer 5
Session
Layer 4
Transport
Layer 3
Network
Layer 2
Data link
Layer 1
Physical
Physical medium
Figure 1.12 OSI Protocol Layers
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OSI Layers and Services
Layer
No.
Layer Name
Salient services provided by the layer
1
Physical
-Transfers to and gathers from the physical medium raw
bit data
-Handles physical and electrical interfaces to the
transmission medium
2
Data link
-Consists of two sublayers: Logical link control (LLC) and
Media access control (MAC)
-LLC: Formats the data to go on the medium; performs
error control and flow control
-MAC: Controls data transfer to and from LAN; resolves
conflicts with other data on LAN
3
Network
Forms the switching / routing layer of the network
4
Transport
-Multiplexing and de-multiplexing of messages from
applications
-Acts as a transparent layer to applications and thus
isolates them from the transport system layers
-Makes and breaks connections for connection-oriented
communications
-Flow control of data in both directions
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Session
-Establishes and clears sessions for applications, and
thus minimizes loss of data during large data exchange
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Presentation -Provides a set of standard protocols so that the display
would be transparent to syntax of the application
-Data encryption and decryption
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Application
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-Provides application specific protocols for each specific
application and each specific transport protocol system
The message in each layer is contained in message units called protocol
data units (PDUs), which consists of two parts - protocol control
information (PCI) and user data (UD).
PCI consists of header information about the layer UD contains the data
that the layer, acting as service provider, receives from or transmits to the
upper layer / service user layer.
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End System A
User A
End System Z
User Z
UD
Application
(A) PCI
Presentation
(P) PCI
Session
(S) PCI
Transport
(T) PCI
Network
(N) PCI
Data link
(D) PCI
Application
UD
Presentation
(A) PDU
Session
(P) PDU
Transport
(S) PDU
Network
(T) PDU
Data link
(N) PDU
Physical
Physical
(D)PDU Data stream
Physical Medium
Figure 1.14 PDU Communication Model between End Systems
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The size of the PDU increases as it goes towards lower layers.
The size of PDU exceeds the maxsize of layers specifications, it is
fragmented into multiple packets.
Protocol layers and Services.
Layer 1, Physical Layer
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There are various protocol standards for physical layer interface, depending on the
transmission medium and type of signal.
Two classes of standards have been established by
(i)
the International Telecommunications Union Telecommunications
Sector (ITU-T)
(ii)
(ii) Electronics Industries Association (EIA)
Layer 2, Data Link Control Layer.
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The data communication between two data terminating equipment (DTE)s is
controlled by this layer.
Two sub layer LLC (logical link control) and MAC ( Medium Access Control)
are there.
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LLC – it performs link management & data transfer
MAC - Controls the access and transmittal of data to the physical layer in an
algorithmic manner.
 There are two types of Physical medium algorithms we are using.
(i)
LAN – bustype – distributed probabilistic algorithm- (CSMA / CD)
(ii)
LAN – token ring – deterministic token –passing algorithm – Token ring(TR),
Fiber distributed data Interface (FDDI)
Layer 3, Network Layer.
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It controls and managers the switching facric of the network.
It provides connection oriented network service (CONS) and
network service (CLNS).
CONS – for long message transmission, not reliable.
CLNS – for short message transmission, it is reliable.
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connectionless
SNICP – Subnetwork Independent convergence Protocol, that interfaces to the transport
layer. Internet Communicates between nodes using an Internet address
and SNICP
SNDCP – Subnetwork-Dependent Convergence Protocol, which depends on
the subnetwork protocol and could be any proprietary protocol.
SNDCP - It communicates with its data link layer via SNDAP
SNDAP – Subnetwork-dependent Access Protocol.
DTE-A
A
N
DTE-N1
Z
N1
N2
A-N-Z Standard Network
N-N1-N2-N3 Subnetwork under Node N
N3
(a) Network configuration
System A
Gateway System N
Transport
Transport
SNICP
SNICP
Subnet system N1
Transport
SNICP
SNDCP
SNDCP
SNDAP
SNDAP
SNDAP-SN
SNDAP-SN
Data link
Data link
Data link-SN
Data link-SN
Physical
Physical
Physical-SN
Physical-SN
SNDCP-SN
Network Medium
SNDCP-SN
Subnetwork Medium
(b) Protocol Communication
Figure 1.17 Gateway Communication to Proprietary Subnetwork
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Gateway Communication to a proprietary subnetwork. Examples are Connection
Oriented OSI Protocol is X.25 packet layer protocol, ISO CLNP is TCP/IP.
4th Layer, Transport Layer.
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It multiplexes the user data provided by the application layers and passes the
packets to the network layer.
Connection oriented protocol TCP (Transmission Control Protocol).
Connectionless protocol UDP (User datagram Protocol).
ISO has five transport-layer specifications, TP0 to TP4
An application Process Communicates with another application process during a
session
5th Layer, Session Layer
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The session-layer establish the communication at the beginning of the session,
monitor, synchronize and error-correct the information exchanged during the
session, and release the logical link at the end of the session.
6th Layer, Presentation Layer.
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Presentation layer is a context-sensitive layer. A common syntax semantics is
Abstract Syntax Notation Number One (ASN.1)
Primary function of presentation layer is conversion of syntax, data encryption
and data compression are also generally done in that layer.
SNA
OSI
End User Application
Application
Presentation Services
Presentation
Data Flow Control
Session
Transmission Control
INTERNET
Transport
SNICP
Path Control
Network
Application Specific
Protocols
Transport
Connection- Connectionless: UDP oriented: TCP
Network
IP
SNDCP
SNDAP
Data Link
Data Link
Physical
Physical
Not Specified
Figure 1.18 Comparison of OSI, Internet, and SNA Protocol Layer Models
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OSI User
Internet User
VT
Terminal
Application
TELNET
FTAM
FTP
MOTIS
SMTP
CMIP
Mail / Message
Transfer
Management
Application
SNMP
Presentation Layer
File Transfer
Transport Layer
Figure 1.19 Application Specific Protocols in ISO and Internet Models
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The above figure compares four common application-specific protocols in the
OSI and Internet models. There are more OSI application-specific protocols,
which we do not discuss here. All application-specific protocols services in OSI
are sandwiched between the user and presentation layers. In the Internet model,
they are sandwiched between the user and the transport layers.
Case Histories of Networking and Management.
Case History 1: The Importance of Topology (“the case of the Footprint”)
Case History 2: Filtering Does Not Reduce Load on Node.
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Repeater
Repeater
Repeater
Repeater
Bridge
ISP
Backup ServerMail Server
(a) Multi-Segment Bus LAN with Single Port Bridge Connection
Repeater
Repeater
Repeater
Repeater
Bridge
ISP
Backup ServerMail Server
(b) Dual Multi-Segment Bus LANs with Two-port Bridge Connection
Backup Server Mail Server
Hub
Hub
Hub
Bridge
ISP
(c) Multi-Segment Hub Configuration
Figure 1.20 Case History 2: Network Configuration Evolution
(a) most of the traffic was internal to the LAN segment, except for
e-mail and back up operations, which went across the bridge.
(b) LAN segment was split into two and used two ports of the
bridge. This decreased the rate of failure from two per day to
two per week.
(c) All three hubs and the bridge are in a central place.
Some Common Network Problems
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The most common and serious problems of networks are connectivity failure,
which are in the category of fault management.
The network failure is caused more often by a node failure than by failure of
passive links.
The node failures manifest as connectivity failures to the user.
Another cause of network connectivity failure is procedural, but very common
(like IP address)
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A host or system interface problem in a shared medium can bring the entire
segment down.
The intermittent problems could also occur as a result of traffic overload, which
could cause packets to be lost.
Power hits could reset network component configuration, causing network failure.
A performance problem could manifest as a network delay and is an annoyance to
the network manager.
With the ever increasing size of networks and connectivity to the Internet,
security violation is a frequent problem.
Perspectives of Network Managers
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Learning network management involves more than understanding networks
and network management protocols.
General:
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People expect all networks to be like telephone networks
Network reliability equal to telephone reliability is unrealizable. The
telephone network was monopolistic and had expensive redundancy. Data
network is adhoc, decentralized, has loosely specified interfaces, and has
dynamic routing. Thus, it is more flexible than a telephone network, through
less reliable. The latest user satisfaction for an ISP is 16 percent and the ISPs
are still growing.
 Some of the data communications are non-real time such as execution of
instructions like Mars Rover. Thus, when a problem is detected it is too late
to fix it.
1. What are your top challenges in managing the network?
 Saying abreast of the rapid advance of technology, depending on trade
journals, vendor product info, and conversations with colleagues.
 Analyzing problems, which requires intuition and skill.
 Anticipating customers’ demands
 Acquiring resources
 Sustainable network that is scaleable and maintainable
 Managing the client/server environment
 Networking with emerging technology as part of continuing education
 Collaborative research between academic institutions and industry
 Maintaining reliability, that is, making changes, upgrades, and such
without disrupting the network and affecting business
 Diagnosing problems or outages in a nondisruptive manner
 Estimating the value of a technology transition
 Maintaining a secure firewall between the internal network and the
Internet while gaining the value of the information and services available
from the Internet.
 Determining responsibility for outages to the WAN, coordinating
telephone company repair efforts.
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Keeping the topology as simple as possible within the confines of the
technology in order to reduce administrative effort and chance for
mistakes.
2. Which elements of managing your network require most of your time? What
percentage of time do you spend on maintenance compared to growth?
 Configuring the management system itself
 Expanding the network
 Gathering and analyzing statistics for presentation to upper management.
 Traditional maintenance 30% (Manager of Organization X)
Mandatory maintenance 40%
Growth
30%
 Growth
50% (Manager of Organization Y)
Maintenance 50%
3. How did you or would you manage your network without an NMS?
 Reactively, not proactively, firefighting
 Troubleshooting tools
 Home-grown systems
 Managed the network in the spare time after installation
 Human intuition
 Rely on consultant advice and technical information for growth decisions
4. Do you need an NMS? If so, why?
 Yes, for proactive management of the network
 Yes, to verify customer configuration
 Yes, to diagnose problems
 Yes, to provide statistics on performance
 Yes, to help remove bottlenecks
 Yes, because an NMS formalizes the manual practice of network
management
 Yes, because NMS products reflect the practices of the company that
develops them
 Yes, but remember NMS does not solve problems, people do
 Yes, but a low-end NMS is adequate
 Yes, the configuration and operation of NMS reflects the person who sets
it up
 Yes, to see the trend in growth
5. How would you use NMS and why/
 Save time and use human resources effectively
 Saved time goes into improving network management
 Turn-around time for problem resolution smaller
 Monitor the status and performance of the network
 Gather statistics to improve OAM&P
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Document events for auditing purposes
Troubleshooting
Remove constraints and bottlenecks
Fault isolation
I would expect the NMS to help me evaluate load on network segments
and pinpoint failures
6. what does a network failure cost the user?
 There are tangible and intangible losses
 The losses of academic and research(A&R) laboratories differ from the
losses of business corporations. A&R labs need high technology and
tolerate low reliability. Business accept lower and proven technology but
require high reliability.
 The cost is a function of the dependence of the business upon shared data.
If we have a general network failure, our ability to conduct business is
severely impacted because we cannot get access to the data.
7. What are your expectations of a newly graduated student with networking as
area of specialization?
 Prefer to hire candidates with networking experience
 Need to be familiar with protocols
 Possess the drive to understand and to envision
 Be a self-starter
 Lab experience at school is essential
 Knowledge of basic networking
 Know the differences between system, applications, and network
 Technical: knowledge foundations, applications, tools, utilities, and so
forth
 Be technically current with the common protocols, wiring topologies, and
common network equipment
 Be professional, have more than just technical skill
 Know how to succeed in commercial organizations
 Recognize the importance of customer service, and see IT as the service
provider
 Know how to stay ahead of demand curve
 Possess personal communication skills
 Be cost conscious
 Have a sense of business risk reduction.
Network Management: Goals, Organization and Functions
Network management can be defined as OAM&P (Operations, administration,
maintenance and provisioning)
Operations group – daily operations
Administration – establishing and administering the over all goals, policies, and
procedures of network.
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Installation & maintenance group – installation and repairs of facilities & equipment
Provisioning – network planning and circuit provisioning, traditionally handled by
provisioning department.
Goal of Network Management
Network
Management
Network
Provisioning
Network
Operations
Network
Maintenance
Planning
Fault Management / Service Restoration
Fault Management
Design
Configuration Management
Trouble Ticket
Administration
Performance Management / Traffic Management
Network Installation
Security Management
Network Repairs
Accounting Management
Facilities Installation
Reports Management
& Maintenance
Routine Network
Inventory Management
Tests
Data Gathering & Analyses
Figure 1.21 Network Management Functional Groupings
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The goal of network management is to ensure that the users of a network
receive the information technology services with the quality of service that
they expect. Toward meeting this goal, management should establish
policy to either formally or informally contract a service level agreement
with the user. (Eg. 2X7 services or 8X5 services)
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Network
Users
Configuration Data
Management
Decision
Performance & Traffic Data
New
Technology
Engineering Group
- Network Planning &
Design
TT Restoration
Operations Group
NOC
I & M Group
-Network Installation &
Maintenance
- Network Operations
Fault TT
Installation
Figure 1.22. Network Management Functional Flow Chart
Network Provisioning
It consists of network planning and design and is the responsibility of engineering
group.
Network Operations and NOC
 NOC – Network operations center
 They are concerned with daily operation s of the network and providing
network services
 ISO has defined fine OSI network management applications.
Trouble ticket Administration
 It is part of fault management and is used to track problems in the network.
Configuration Management
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There are three types of configuration managements.
1. Static Configuration – it is permanent configuration of the network. Come
up if network started from idle status.
2. current running configuration.
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3. planned configuration – for future.
Security Management
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physically securing the network and controlling access to the network by the
users,
a security database is established and maintained by the NOC for access to the
network and network information.
Performance Management
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Network statistics include data on traffic, network availability and network delay.
Accounting Management
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The NOC administers costs and allocates the use of the network. Metrics are
established to measure the usage of resources and services.
System reports – for network operations to track the activities
Management reports – performance of NOC & network
User reports – status of network performance
Network Installation and Maintenance
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Takes care of all installation and maintenance of equipment and cables.
Network and System Management
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System management as the management of systems and system resources in the
network.
Network management is concerned with network resources such as hubs,
switches, bridges, routers and gateways, and the connectivity among them via a
network.
It is relatively simple for a vendor to develop a network management system to
manage a network of components it produced.
To connect different vendor components require installation of multiple network
management systems.
Common management system as well as the integration of different management
systems ad their inter operability has played a major role in the network
management arena in the past decade.
Transport Protocols are the first 4 layers of OSI model and TCP/IP over any of
the first two layers of the seven-layer OSI model.
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Network management Components
NMS
Network
Agent
Network
Agent
Network
Objects
Network
Objects
Figure 1.24 Network Management Components
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Each network agent monitors its respective objects.
Interoperability
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
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Application
Services
Objects
Objects
Management
Protocol
Vendor A
Objects
Vendor B
Objects
Transport
Protocols
(b) Services and Protocols
Figure 1.23 Network Management Dumbbell Architecture
(b) application services are the management related applications such as fault and
configuration management. The management protocols are CMIP (Common
management information protocol) for OSI model and SNMP for Internet model.
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As the two NMS’s communicate, each NMS can superimpose the data from the
other and present an integrated picture to the network administrator.
Another area of system management is logging and archiving events.
Network Management System Platform
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High – end systems are housed either on SUN or HP unix-based workstations.
Some run on windows-NT based PC.
Low-end NMS run either on Windows 95/98 or NT.
Common troubleshooting and monitoring network element parameters could be
done by using simple networking and network management tools. These are part
of TCP/IP stack.
Current Status and future of Network Management
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The current network management systems are based on the SNMP Protocol.
Current NMS has several limitations.
1. They need a dedicated NMS monitoring station, which must be on a
specific type of platform
2. limit of an SNMP- based management system is that the values of the
managed objects should be defined as scalar values.
3. CMIP (OSI model) is object- oriented. Complexity of specifications of
managed objects, enormous memory required to handle CMIP.
4. SNMP – a polling based system.
NMS polls each agent as to its status, or for any data that it needs for
network management.
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5. SNMP – have been overcome by the emerging web-based management.
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A web-based system is plat form – independent for the management software
using java language in the managed components, for the web-based NMS server,
as well as for web-browser monitors.
Object-oriented technology is reaching a mature state and hardware capacity to
handle object-oriented stacks is now commercially available.
Two potential web-based management schemes
1. JMX – Java management extensions – developed by SUN
2. WBEM – Web based enterprise management – based on common
information model developed by Microsoft.
Another re-emerging technology on the horizon for network management is
wireless technology. This is being deployed widely for WAN, mobile and
broadband access services.
An active network, which is the direction of the next generation network, would
include embedded network management applications.
A single failure in a network can cause multiple symptoms and manifest itself in
multiple locations.
The fault can propagate in space and time across the network.
With the proliferation of the Internet, securing networks and communication has
become extremely important. Existing management standards do not go far
enough in this.
Prepared By
Sivakumar P V
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