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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

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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

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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.)

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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.)

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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

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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

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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.)

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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.)

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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

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Training
What’s new memos/emails
Steps for NOS Upgrade
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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
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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

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Networked workstation
Networked printer
Hub
Server
Switches or routers
Adding or Upgrading Equipment

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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 and
Backbone Upgrades
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Cabling upgrades
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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


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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

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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
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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

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replicates itself so as to infect more
computers
Trojan horse
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Program that is disguised itself as
something useful but actually harms your
system
Types of Viruses
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Boot sector viruses
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Macro Viruses
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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
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

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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


Stealth
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Hide within a program
Polymorphism
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Format that virus checker can’t read
Change themselves as they move from system to
system
Time-dependence
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Only activate on a particular date
Antivirus Software
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Symptoms of a virus
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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
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Signature scanning
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Integrity checking

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Comparison of a file’s content with known virus
signatures in a signature database
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.)
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Receive regular updates and modifications
from a centralized network console
Consistently report only valid viruses,
rather than reporting “false alarms”
Antivirus Policy
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General guidelines for an antivirus policy
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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

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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
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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
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Fail-over
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Hot swappable
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Process of one component immediately assuming
the duties of an identical component
Identical components that automatically
assume the functions of their counterpart if
one suffers a fault
Single point of failure
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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
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Environment
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Analyze the physical environments in which your
devices operate
How well are your critical network components
protected from environmental hazards
Power
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Whatever the cause, networks cannot tolerate
power loss or less than optimal power
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Surge
Line noise
Brownout--Also known as a sag
Blackout
Uninterruptible Power Supply
(UPS)
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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

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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

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Low-end --$50-$300
Higher-end--$200-$3000
Generators
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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
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Mesh or Hybrid Mesh
Topology
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Provide redundant connections
between network components
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FDDI and SONET
Topology
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Dual rings provide fault
tolerance
Redundant Storage—RAID
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Redundant Array of Inexpensive (or
Independent) Disks

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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
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0, 1, 5 are the levels most commonly used in
Windows-based networks
RAID Level 0—Disk Striping
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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
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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
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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 and
Server Clustering
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Server mirroring
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Fault tolerance technique in which one server
duplicates the transactions and data storage of
another
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Servers must be identical machines; same processor,
same type/size hard disk(s), etc.
Can slow network performance
Server clustering
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Fault tolerance technique that links multiple servers
together to act as a single server
Data Backup
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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
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Questions to ask when selecting the appropriate
tape backup solution for your network
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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
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Questions to ask in developing a backup
strategy
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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
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Full
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Incremental backup
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Backs up all selected files
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

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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

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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