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NETWORK MANAGEMENT “Effective network management optimizes a telecommunication network’s operational capabilities and resources - Optimization.”
• System Depth - A Network Management Problem • Network Management - From A PSTN Perspective
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Network Management Functions
Some of the primary functions of network management can be listed as follows:
• It keeps the network operating at peak performance. • It informs the operator of impending deterioration. • It provides easy alternative routing and work
arounds when deterioration or failure takes place. • It also provides the tools for pinpointing the causes
of performance deterioration or failure. • It serves as the front-line command post for network
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The Need for Management • Typical problem
– Remote user arrives at regional office and experiences slow or no response from corporate web server
• Where do you begin? – Where is the problem? – What is the problem? – What is the solution?
• Without proper network management, these questions are difficult to answer…
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The Case for Management • With proper management tools
and procedures in place, you may already have the answer.
• Consider some possibilities: 1. What configuration changes
were made overnight? 2. Have you received a device
fault notification indicating the issue?
3. Have you detected a security breach?
4. Has your performance baseline predicted this behavior on an increasingly congested network link?
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• An accurate database of your network’s topology, configuration, and performance
• A solid understanding of the protocols and models used in communication between your management server and the managed devices
• Methods and tools that allow you to interpret and act upon gathered information
Response Times High Availability
Solving Problem Procedure
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SYSTEM DEPTH – A Network Management Problem
• Network Management System (NMS) – Automatic Vs Human Effort – Increased Network Size – Increased Complexity
• Heterogeneous equipment • Equipment from multiple vendors
• Network Management Requirements
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Network Management Requirements
• Ease of use • Security features • Restoral capability • Ability to delete/add • Monitor network availability • Traffic rerouting • Improved automation • User registration • Improved reporting
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Network Management Requirements
• Ability to monitor response time • Control corporate strategic assets • Control complexity • Improve service • Balance various needs • Reduce downtime • Control cost
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Network Management Systems (NMS)
• NMS is a collection of tools for network monitoring and control – Designed to view the entire network as a unified architecture
• addresses and labels assigned to each point • specific attributes of each element and link known to the
system – Single operator interface with a powerful but user-friendly set
of commands – a minimal amount of separate equipment (hardware/software)
is necessary • NMS software resides in the host computers and
communications processors (bridges, routers etc.)
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Network Management Systems
• The active elements of the network provide regular feedback of status information to the network control center
• NMS for single vendor equipment versus NMS for multiple-vendor network
• Two or more network control centers are used – for high availability or backup – one center is idle or collecting statistics – the other center is used for control
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NMA = network management application
NME = network management entity
Appl = application
Comm = communications software
OS = operating system
Network Management System
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Network Management Configuration
• Network Management Element (NME) – Contains a collection of software devoted to the NM task in each
network node – Collects statistics – Stores statistics locally – Responds to commands from network control center (manager)
• Transmit collect statistics to manager • Change a parameters (a timer in a transport protocol) • Provide status information • Generate artificial traffic for testing
– Send messages to network control center for significant changes in local conditions
– Be referred to as an agent – Agents are implemented in end systems and nodes
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Network Management Configuration
• Network Management Application (NMA) – Include an operator interface to allow an
authorized user to manage the network – Respond to user commands
• display information • issue commands to NMEs through the network
– Communicate with and control NME in other nodes
• Application-level network management protocol
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1- Isolated LAN (A Fairly Simple Example) • There is only a singular transmission medium and, under
normal operating conditions, only one user is transmitting information to one or several recipients.
• It is limited to only two OSI Layers and for troubleshooting, often a protocol analyzer will suffice, although much more elaborate network management schemes and equipment are available.
2- Connected LAN (A Complicated Challenge) • An example is a VAX running DECNET, that is a station on a
CSMA/CD LAN. • The LAN is bridged to a frame relay box that fed a 384 kbps
channel with an E1 hierarchy (six E0 channels), via tandemed microwave links to a large facility at the distant end (550 Km) with similar characteristics.
• Such is typical of a fairly complex network requiring an overall network management system.
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Network Management Provisioning Aids
• Modern E1 & T1 digital systems are provided a means for operational monitoring of performance.
• This monitoring is done in quasi-real time and while operational, i.e. in traffic.
• DS1 or T1 has a frame rate of 8000 frames per second.
• Each frame is delineated with a framing bit called F- bit.
• Maintaining the framing repetition of the F-bit 8000 times a second is excessive and unnecessary.
• Advantage of F-bit redundancy is taken by the development of the extended superframe (ESF).
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Extended Superframe (ESF)
• The ESF consists of 24 consecutive DS1 frames and within 24 frames, we have 24 framing bits.
• Ofthese, only 06 bits need to be used for framing. • Six are used for a cyclic redundancy check (CRC-6)
on the superframe. • The remaining 12 bits from a 4Kbps data link for
network control and maintenance. Total No. of Bits: 6 + 6 + 12 = 24
• It is this channel that can serve as transport for network management information and as an ad-hoc test link.
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Communication Channels for the Network Management System
• A network management facility is usually centrally located which must monitor and control distant communications equipment.
• It must have some means of communicating with this equipment which may be widely dispersed geographically.
• DS1 & E1 systems provide a data channel for operations and maintenance (OAM).
• Higher levels of the DS1 & E1 hierarchies have special communication channels for OAM.
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• The solution for a LAN is comparatively straight-forward, in which the network management facility or LAN protocol analyzer becomes just another active station on the LAN.
• Network management traffic remains as any other revenue-bearing traffic on the LAN, and ofcourse this should not overpower the LAN with message unit quantity.
• For a true network management system, a separate network managenent communication channel may have to be provided and sandwiched into the physical layer.
• However, SNMP was developed to typically use the transport services of UDP/IP, which is an additional overhead.
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What is a PSTN Network ? Switching
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Public Switched Telephone Network (PSTN)
Major Components of the Public Switched Telephone Network (PSTN): Switching Offices Transmission facilities Customer Premise Equipment (CPE)
Customer Premise Equipment (CPE) is the term used to identify any piece of equipment supplied by the customer to interface with the PSTN.
Examples include: • Single Line Telephone Set • Modems or Data Sets • Private Branch Exchange (PBX)
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Special Service Circuit
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Local Network Structure
Exchange Area 5
Exchange Area 4
Exchange Area 3
Exchange Area 2
Exchange Area 1
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Network Management From A PSTN Perspective
Objectives & Functions: The accurate term defining the network management
perfectly is “Surveillance & Control.” The major objectives for network surveillance and
control organizations are: • Maintaining a high level of network resources
utilization • Minimizing the effects of network overloads • Supporting the National Security Emergency
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There are three important functions that contribute to attaining the above stated objectives:
• Network Traffic Management - NTM Center - NTM Principles - NTM Functions - NTM Controls
• Network Services • Service Evaluation
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Typical Local Network
Tandem Office T
Tandem Trunk Groups (Final)
Direct Trunk Groups (High Usage)
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Typical LATA Network
Tandem OfficeCentral Office
Distribution Facility/Local Loop
Distribution Facility/Local Loop
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Network Traffic Management Center
• An NTM center provides real time surveillance and control of message traffic in local access and transport area (LATA) telephone networks.
• The goal of an NTM center is to increase call completions and optimize the use of available trunks and switching equipment.
• Several dedicated Operational Support Systems are employed by an NTM center to achieve this goal by accumulating information.
• Using this information and call control capability, a network traffic manager can optimize the call-carrying capacity of the network.
• OSSs also enable the network traffic manager to interact with the network to minimize the adverse effects of traffic overloads and machine/facility failures.
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Network Traffic Management Principles
NTM decisions are guided by four principles, which apply regardless of switching technology, network structure, signalling characteristics or routing techniques.
All NTM control actions are based on atleast one of the following principles:
• Keeping all trunks filled with messages. • Giving priority to single link connections. • Use of available trunking. • Inhibit switching congestion.
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Network Traffic Management Functions
• General Network Overload: It is caused by changes in traffic patterns and increased traffic load.
• Focused Overload: It is generally directed toward a particular location and may result from media stimulation.
• Switching System Overload: It occurs because each individual switch is engineered to handle a specific load that is known as ‘engineered capacity’.
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Network Traffic Management Controls
1- Circuit - Switched Network Controls • Protective Controls:
These controls remove traffic from the network during overload conditions. This traffic is usually removed as close as possible to its origin, thus making more of the network available to other traffic with a higher probability of completion.
• Expansive Controls: These controls reroute traffic from routes experiencing overflows or failures to other parts of the network that are lightly loaded with traffic because of non-coincident trunk and switching system busy hours.
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2- Automatic Controls in Modern Digital Switches
The current computer-based switches may include the following types of automatic controls:
• Selective dynamic overload control • Selective trunk reservation • Dynamic overload control • Trunk reservation control • Selective incoming load control
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REFERENCE • Chapter - 21, ‘Fundamentals of
Telecommunications’ by Roger L. Freeman, 2nd Ed. John Wiley & Sons Inc. N.J., 2005.
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