Chapter 16: Network Management Principles of Computer Networks and Communications M. Barry Dumas and Morris Schwartz

Chapter 16:Network Management

Principles of Computer Principles of Computer Networks and CommunicationsNetworks and Communications

M. Barry Dumas and Morris SchwartzM. Barry Dumas and Morris Schwartz

Principles of Computer Networks and Communications

2Chapter 16

Objectives

Describe the purpose and function of network management in corporate networks

Distinguish between the roles of people and technology in managing corporate network and identify various responsibilities and functions for each

Identify essential elements in network management planning Describe considerations on what to manage and what not to manage

including impact on dimensions of time, equipment, people, and money Explain the basic structure of network management systems and specifically

illustrate how SNMP operates Demonstrate the significance of network performance monitoring and

indicate the types of information that might assist in network management Describe the ISO FCAPS network management model Provide business considerations that should be incorporated into a network

management plan Provide an example of an open systems network management solution


3Chapter 16

Overview

For network management, corporations are concerned with managing Main corporate networks Isolated corporate LANs and VLANs Connections to public data networks (PDNs)

Public data networks (PDNs) Privately owned and operated WANs Provide public access and charge fees for connection services Commonly used by corporations to extend the reach of their own networks

“From a business perspective, whether we are dealing with simple or complex networks, their

management should be a centralized operation.”


4Chapter 16

Overview

WAN/LAN management—Who’s responsible? Often, corporations do not own their own WANs WANs are typically managed by WAN owners who

are responsible for Link maintenance Upgrades Problem fixes

Problems within the corporate LAN are the province of corporate network management.


5Chapter 16

Overview

Routers See multiple internal LANs as simply connections Move transmissions among them via network layer

protocols (typically using the TCP/IP suite)

“An organization’s own internal networks routinely comprise multiple LANs

interconnected by internal routers.”

If TCP / IP is used, the collective internal networkis called an intranet.


6Chapter 16

Overview

Intranets Are accessible only to authorized employees With external connections reside behind corporate firewalls

vs.

Extranets Are accessible to people outside the company Provide limited access to specific parts of an intranet

Internal corporate network

External “special clients” network access


7Chapter 16

Overview

Network management system (NMS) Developed in the 1990s Systems for automated network management Offered simple method for monitoring and managing

entire corporate networks

NMS problems Simplification was a myth Not necessarily compatible with corporate devices NMS (proprietary) monitoring devices were

complicated

NMS consoles in the late 1990swere more versatile and compatible


8Chapter 16

People and Systems

Technology tasks in network management Databases track access rights, usage, and passwords Sniffers monitor traffic Hardware and software modules installed in network devices

provide activity data and respond to commands NMS consoles integrate and coordinate (all of the above)

“No matter how automated a company’s network management system is, the ultimate responsibility for network

management rests with people.”


9Chapter 16

People and Systems

Who manages the networks?

Large company (complex networks) Administrators are

Accounts managers (passwords/access rights) Technicians (resolve faults/perform upgrades) Upper-lever managers (oversee department-level operations)

Small company (few networks) One (or two) network administrators (for tasks above)


10Chapter 16

Network Management—Who are these people?Network administratorResponsibilities Network installation, management,

and control (access) Network set-up, maintenance,

security Software licensing and acquisition,

application installation, distribution, and upgrading

Performance and activity monitoring, performance testing

Network design, reconfiguration Storage management, back-up,

restore

Systems administratorResponsibilities Firewall configuration,

password assignment, management of user accounts

Acquisition, installation, and maintenance of network hardware, software, and operating systems

Back-up and recovery E-mail address assignment

Job responsibilities will overlap

Job responsibilities will be organization-dependent


11Chapter 16

People and Systems

Four perspectives for network management planning and process Scope Heterogeneity Size and complexity Intermittent failures


12Chapter 16

People and Systems

Planning and process—scope issues are associated with establishing priorities; that is deciding What network devices to manage How closely devices should be managed What network devices not to manage

The more closely a device is managed,the more it costs!

(time, people, equipment, money)


13Chapter 16

People and Systems

Planning and process scope—setting prioritiesFirst priority Critical systems—those that are most important to the

functioning of the business

Next priority Systems whose malfunctioning is disruptive but not disabling

to the business

Last priority Systems where faults cause little to no disruption

e.g., bank transaction processing

e.g., online ordering

e.g., employee desktop login


14Chapter 16

People and Systems

Planning and process—heterogeneity Network hardware and software are most likely

heterogeneous—products of different manufacturers even for the same type of device

Hardware and software might Be based on different standards Have the same standard but different versions Have proprietary standards Be installed by employees apart from what is “authorized”


15Chapter 16

People and Systems

Network manager responsibilities in a heterogeneous network (with examples)

Helping determine network design Presenting the case for reducing variety

to an acceptable minimum as systems are replaced and upgraded

Managing existing systems What to manage? How closely?

Discovery and enforcement Removing unauthorized products

and preventing their installation

Managing a heterogeneous network compounds as the network grows!


16Chapter 16

People and Systems

Planning and process—size and complexity The larger and more interconnected the networks,

the more difficult they are to manage

Network managers need to keep networks trim and fit Avoid unneeded connections Block unused ports (to reduce intrusion risk) Consider segmenting LANs as traffic patterns emerge Balance connectivity needs with options for providing for

those needs (e.g., more cable or go wireless)


17Chapter 16

People and Systems

Planning and process—intermittent failures Discovering sources and causes of intermittent failures is

one of the more frustrating and time-consuming situations for network managers and affected parties

Intermittent failures might appear as Random packet loss Odd instances of dropped connections Arbitrary login rejections

NMSs might help to isolate problems (e.g., logging alarms and notifications)

Intermittent failures are often orders of magnitude more difficult than even catastrophic failures


18Chapter 16

Structuring Network Management

There are two major incompatible protocol sets for structuring and managing networks

Simple network management protocol (SNMP) Developed by the Internet Engineering Task Force (IETF) TCP/IP layer 5 protocol Latest version is SNMPv3

Common management information protocol (CMIP) OSI layer 7 protocol

SNMP is a simpler protocol than CMIP

SNMP is much more popular than CMIPso the next slides will not be discussing CMIP


19Chapter 16


Network managed device characteristics Has network management modules (NMMs) installed NMMs provide software agents that monitor their devices,

collecting information about their device states and packets they process Network managed devices (examples)

Computers (workstations) Hubs Switches Routers

“The degree to which a network or intranet can be managed depends upon which of its

components are managed devices.”

SNMP provides a structure for information exchange between the managed devices

and the manager.


20Chapter 16


SNMP collects information (“objects”)

Collections of objects—management information base (MIB)

Objects (aka MIB objects or managed objects) Individual items of information within each type

(generic or device-specific) are called objects Objects are contained in MIB modules Device manufacturers provide MIB modules

for their devices Objects are defined by manufacturers

according to the needs/capabilities of their devices

Types of information collected Generic data—commonly defined for any device following

the TCP/IP protocol (e.g., device IP address) Device-specific data—particular to the device itself

(e.g., a configuration setting)

The MIB modules incorporated in a managed device determine what it can report and how it can be controlled.


21Chapter 16


SNMP network management in operation

A network management module (NMM) agent sends data to SNMP manager software for any of the following

1. When polled2. At intervals3. When a problem arises4. When a problem is impending

An NMS can perform most routine operations automatically


22Chapter 16


SNMP—network management communications

Manager-initiated communications follow a “fetch/store” (also “get/set”) object-oriented model

comprising two types of commands 1. Fetch (read data from devices)

Retrieves data collected by device agents

2. Store (write data to devices) Acts to control the device by resetting

counters or re-initializing the device

Each MIB object has a unique name that the manager uses when sending a fetch or store command

Example:MIB object: failchkthat counts frames failing their frame check

Manager Sends fetch failchk command to read status

Sends store failchk command to reset device


23Chapter 16


SNMP—network management communications

Device problem

When some fault (failure) occurs or is about to occur, the device sends an alarm (fault alert message) to the manager

Alarm types are predefined in the MIB


24Chapter 16


SNMP—network management setup Basic

Manager can request agent information only from devices that are on the same network as the manager

Remote For devices on other attached networks Requires remote monitoring (RMON) protocol


25Chapter 16


SNMP—network management setup Remote

For devices on other attached networks Requires remote monitoring (RMON) protocol

Extension of SNMP Defines statistics that can be passed between managers and

remote devices Defines functions that can be activated for control purposes

RMON uses probes to collect/analyze data—For traffic monitoring—To send alarms about impending or actual faults


26Chapter 16


Fig. 16.1Managed network structure

Everyone has SNMP MIBs

Agents send data to SNMP manager software when polled?

D

To extendednetworks


27Chapter 16

Concerns of Network Management

Network management—concerns More than discovering, locating, and resolving faults

Faults can be Actual failures Symptoms of unusual activity that can

Eventually become a failure Cause failures in other parts of an intranet

Correction is usually simpler if a problem can be identified before that (failure) state is reached.

This points to the importance of monitoring network performance.


28Chapter 16

Concerns of Network Management

Yes! Reacting to alarms and taking action for those that

cannot be handled automatically Reviewing NMS tracking statistics to spot potential

problem areas Taking proactive steps to ward off impending failure

With automatic network managing systems,

do we still need people?


29Chapter 16

FCAPS

Fault management Discovering, locating, correcting, and logging failures

and conditions likely to lead to failures Configuration management

Device software and software components Network physical and logical topologies and protocols

Accounting management Efficient allocation of resources (e.g., user accounts, password management)

Performance management Track performance measures and keep networks running efficiently

Security management Controlling access to network resources (i.e., network itself and data contained)

FCAPS

“A commonly used model for network management is ISO’s FCAPS.”


30Chapter 16

Network Performance Measures

Throughput Number of bits per second (bps) at the destination node

Resource utilization Percentage of a resource’s capacity used by packets it is processing

Error rate (also bit error rate) Number of erroneous bits received as a proportion of the total number

of bits sent Latency

Time between packet transmission and receipt (measure of network responsiveness)

Mean time before failure (MTBF) Average length of time before a network component fails

Mean time to repair (MTTR) Length of time between when a failure occurs (or is reported)

and when the device is put back into service


31Chapter 16

Business Considerations

Network management is an expensive proposition!

Costs can include Hardware and software (Highly salaried) support personnel Costs from downtime

“Business decisions regarding internal resources and systems usually are made on a cost/benefit basis.”


32Chapter 16

Business Considerations

Businesses tend to go in one of two directions (views)

Network management as a cost center Budget as little as possible to get by Leads to large unexpected expenses from problems

Network management as the most important information system component

Leads to overinvestment in complex NMSs, large inventories of spare equipment, and very large staffs

The solution is to apply a business case that incorporates a network management function only

if it directly addresses a business problem.


33Chapter 16

Open Network Management

Freeware Available without charge (or with non-mandatory requests for donations) Owned and distributed by its creator Not subject to modification by others

vs.

Open source Available without charge Not owned by anyone (i.e., in the public domain) Available for viewing and modification by others

Open Network Management System (OpenNMS)

Billed as “the world’s first enterprise grade network management platform developed under the open source model.”

Documents

Chapter 16: Network Management Principles of Computer Networks and Communications M. Barry Dumas and Morris Schwartz