Chapter Thirteen

Maintaining

and Upgrading

a Network

Keeping Track Establish the baseline for your network

Baselining Practice of measuring and recording a

network’s current state of operation System’s performance may begin to

degrade, sometimes gradually at other times dramatically. Compare baseline observation to current

system behavior.

Keeping Track

Asset management System of identifying and tracking the hardware

and software on your network Record information about how your network is set

up and why Physical network layout Documentation on licensing agreements

Change management Use your change management system to record

any changes resulting from network maintenance or upgrades

Software Changes

General steps for software changes Determine whether the change is necessary

Research the purpose of the change and its potential effects on other programs

Determine whether the change should apply to some or all user and whether it will be distributed centrally or machine-by-machine

If you decide to implement the change, notify system administrators, help desk personnel, and users

Make sure that people get appropriate training

Software Changes

General steps for software changes (cont.) Back up current system or software before

making any modifications Prevent users from accessing the system or

part of the system being altered Keep the upgrade instructions handy and

follow them during installation of the patch or revision

Make the change

Software Changes

General steps for software changes (cont.) Test the system fully after the change, preferably

using the software as a typical user would If the change was successful, re-enable access to

the system; if unsuccessful, revert to previous system version of the software

Inform system administrators, help desk personnel, and users when the change is complete

Record the change in the change management system

Software Changes

Patch Improvement or enhancement to a

particular piece of a software program May be released to fix major bugs in the

original program Bug--Flaw in a software program that causes

some part of the program to malfunction Service pack

Term Microsoft uses for its significant patches for Windows NT Server and Windows 2000

Software Changes

Upgrade Major change to existing code May or may not be offered free from a

vendor In general, upgrades are designed to

add functionality and fix bugs

Software Changes

Application upgrades Represent modifications to all or part of a

program that are designed to enhance functionality or fix problems related to software

Apply to software shared by clients on the network

For example, an upgrade of the database program used to store all the client records

Network Operating System Upgrades

Considerations for NOS upgrade Affect on user IDs, groups, rights, and policies Affect on file, printer, and directory access on the

server Affect on applications or client interactions on

the server Affect on configuration files, protocols, and

services running on the server

Network Operating System Upgrades

Considerations for NOS upgrade (cont.) Affect on the server’s interaction with other

devices on the network Accurately testing the upgrade software in

simulated environment Taking advantage of the new operating

system to make your system more efficient Having resources available during upgrade

process to address any problems

Network Operating System Upgrades

Considerations for NOS upgrade (cont.) Allot enough time to perform the upgrade Ensure that users, help desk personnel, and

system administrators understand how the upgrade will affect their daily operations and support burdens

Training What’s new memos/emails

Steps for NOS Upgrade

Research Proposal Evaluation Training Pre-implementation Implementation Post-implementation

Reversing a Software Upgrade

Backleveling Process of reverting to a previous version of

software after attempting to upgrade it Use the operating system uninstall feature (if

available) Restore from backups

Hardware and Physical Plant Changes

Guide for changing network hardware Determine whether the upgrade is necessary If possible, back up the current hardware’s

configuration Let people that will be affected know that you are

making the change, when, and why After change, test the hardware to insure that it is

fully operational before allowing users to access Record the change

Adding or Upgrading Equipment

Networked workstation Networked printer Hub Server Switches or routers

Adding or Upgrading Equipment

The best way to safely gain experience with adding, upgrading, or repairing devices is to experiment with devices that are not currently used on a network

Bear in mind that adding a new processor to a server, a new NIC to a router, or more memory to a printer may affect your service or warranty agreement with the manufacturer

Cabling Upgrades andBackbone Upgrades

Cabling upgrades May require significant planning and time

to implement, depending on the size of your network

Backbone upgrades The most comprehensive and complex

upgrade involving network hardware

Reversing Hardware Changes

As with software changes, you should provide a way to reverse the hardware upgrade and reinstall the old hardware if necessary

Keep the old component safe, as you not only might you need to put it back in the device, but you might also need to refer to it for information

Managing Growth and Change

Factors that might influence currently developing trends in networking technology Faster data transmission and greater accessibility will

bring network access to more people in less time Increasing compatibility between vendors Open standards will make networking careers less

specialized and probably more interesting Smarter devices will contribute to each of the above

trends, enabling the development of faster, more open standards and providing greater accessibility

Researching Network Trends

Magazines, industry associations, colleagues, Internet

Newsgroups on the Web can provide valuable information, too

Chapter Fourteen

Ensuring Integrity

and Availability

What Are Integrity and Availability?

Integrity Reliability and accuracy of a network’s

programs, data, services, devices, and connections

Availability Refers to how consistently and reliably a

system can be accessed by authorized personnel

Guidelines for Protecting Your Network

Prevent anyone other than a network administrator from opening or changing the system files

Monitor the network for unauthorized access or change

Process of monitoring a network for unauthorized access to its devices is known as intrusion detection

Record authorized system changes in a change management system

Guidelines for Protecting Your Network

Install redundant components Situation in which more than one component is installed and

ready for use for storing, processing, or transporting is referred to as redundancy

Perform regular health checks on the network Monitor system performance, error logs, and the

system log book regularly Keep backups, boot disks, and emergency repair

disks current and available Implement and enforce security and disaster recovery

policies

Virus

Program that contains code that may cause the loss of data replicates itself so as to infect more

computers Trojan horse

Program that is disguised itself as something useful but actually harms your system

Types of Viruses Boot sector viruses

Reside on the boot sector of a floppy disk and become transferred to the partition sector or the DOS boot sector on a hard disk

Macro Viruses Take the form of a word-processing or

spreadsheet program macro File infected viruses

Attach themselves directly to the file

Types of Viruses

Network viruses Propagate themselves via network

protocols, commands, messaging programs, and data links

Worms Technically not viruses, but rather

programs that run independently and travel between computers across networks

Virus Characteristics

Encryption Format that virus checker can’t read

Stealth Hide within a program

Polymorphism Change themselves as they move from system to

system Time-dependence

Only activate on a particular date

Antivirus Software

Symptoms of a virus Unexplained increases in file sizes Programs launching, running, or exiting more

slowly than usual Unusual error messages appearing without

probable cause Significant, unexpected loss of system memory Fluctuations in display quality

Antivirus Software

Functions your antivirus software should perform Signature scanning

Comparison of a file’s content with known virus signatures in a signature database

Integrity checking Method of comparing current characteristics of files and

disks against an archived version of these characteristics to discover any changes

It should detect viruses by monitoring unexpected file changes or virus-like behaviors

Antivirus Software

Functions your antivirus software should perform (cont.) Receive regular updates and modifications

from a centralized network console Consistently report only valid viruses,

rather than reporting “false alarms”

Antivirus Policy

General guidelines for an antivirus policy Every computer in an organization should be

equipped with virus detection and cleaning software that regularly scans for viruses

Users should not be allowed to alter or disable the antivirus software

Users should know what to do in case their antivirus program detects a virus

Users should be prohibited from installing any unauthorized software on their systems

Organizations should impose penalties on users who do not follow the antivirus policy

Virus Hoaxes

False alert about a dangerous, new virus that could cause serious damage to your workstation

Usually have no realistic basis and should be ignored

Fault Tolerance

Capacity for a system to continue performing despite an unexpected hardware or software malfunction

Fault tolerant systems provide redundancy or duplication of critical components

Fault Tolerance Fail-over

Process of one component immediately assuming the duties of an identical component

Hot swappable Identical components that automatically

assume the functions of their counterpart if one suffers a fault

Single point of failure Point on a network where, if a fault occurs, the

transfer of data may break down without possibility of an automatic recovery

Environment and Power

Environment Analyze the physical environments in which your

devices operate How well are your critical network components

protected from environmental hazards Power

Whatever the cause, networks cannot tolerate power loss or less than optimal power

Surge Line noise Brownout--Also known as a sag Blackout

Uninterruptible Power Supply (UPS)

Battery-operated power source directly attached to one or more devices and to a power supply

Standby UPS--Switches instantaneously to the battery when it detects a loss of power from the wall outlet

Online UPS--Uses the A/C power from the wall outlet to continuously charge its

battery, while providing power to a network device through its battery

Factors in Choosing a UPS

Amount of power needed A volt-amp (VA) is the product of the voltage and

current of the electricity on a line Period of time to keep a device running Line conditioning—surge and line noise

protection Cost

Low-end --$50-$300 Higher-end--$200-$3000

Generators

If your organization cannot withstand a power loss of any duration, consider investing in an electrical generator for your building

Gas or diesel powered Cost for industrial-type--$10,000-1M+

Redundant Topologies

FDDI and SONET Topology

Dual rings provide fault tolerance

Mesh or Hybrid Mesh Topology Provide redundant connections

between network components

Redundant Storage—RAID

Redundant Array of Inexpensive (or Independent) Disks A group of hard disks is called a disk array

A sophisticated means for dynamically duplicating or storing data using several physical hard drives

Provides fault tolerance for data There are several levels of RAID

0, 1, 5 are the levels most commonly used in Windows-based networks

RAID Level 0—Disk Striping

Simple implementation of RAID in which data are written in 64 KB blocks equally across all disks in the array

No duplication of data--not actually fault tolerant because if one of the disks fails, you will still lose all your data

Requires a minimum of two drives and can support up to 32 Fast because data can be written to multiple drives

simultaneously

RAID Level 1—Disk Mirroring

Data from one disk are copied to another disk automatically as the information is written

Makes an exact copy of a partition on one hard disk to a partition on another hard disk

RAID Level 5—Disk Stripping with Distributed Parity

Data are written in small blocks across several disks Includes error correction information (parity) so that if one of

the disks fails the lost data can be recovered from the other disks

Requires at least 3 partitions of the same size. Each partition should be on a different hard disk.

Server Mirroring andServer Clustering

Server mirroring Fault tolerance technique in which one server

duplicates the transactions and data storage of another

Servers must be identical machines; same processor, same type/size hard disk(s), etc.

Can slow network performance Server clustering

Fault tolerance technique that links multiple servers together to act as a single server

Data Backup

Copy of data and program files created for archiving purposes

Backups should be stored in a safe, fireproof location

Good idea to store off site Backing up can generate

high network traffic Pick a time when there is

little or no network traffic

Tape Backups

Questions to ask when selecting the appropriate tape backup solution for your network

Does the backup drive and/or media storage capacity? Are the backup software and hardware reliable? Does the backup software use data error checking

techniques? Is the system quick enough to complete the backup

process before daily operations resume? How much do the tape drive, software and media cost? Will the backup hardware and software be compatible with

existing network hardware and software? Does the backup system require frequent manual

intervention?

Backup Strategy

Questions to ask in developing a backup strategy What kind of rotation schedule will backups follow? At what time of day or night will the backups occur? How will you verify the accuracy of the backups? Where will backup media be stored? Who will take responsibility for ensuring that backups

occurred? How long will you save backups? Where will backup and recovery documentation be

stored?

Backup Strategy Methods

Full Backs up all selected files

Incremental backup Backs up data that have changed since the

last backup (full or incremental)

Differential backup Backs up data that have changed since the

last full backup

Disaster Recovery

Process of restoring critical functionality and data after enterprise-wide outage that affects more than a single system or limited group of users

Must take into account the possible extremes, rather than relatively minor situations

Pertinent Issues to a Data Recovery Plan

Contact names for emergency coordinators who will execute the disaster recovery response

Details on which data and servers are being backed up, how frequently backups occur, where backups are kept, and how backup data can be recovered in full

Details on network topology, redundancy, and agreements with national service carriers

Regular strategies for testing the disaster recovery plan

Plan for managing the crisis