Download Fault Tolerance (continued)

Network+ Guide to Networks
Third Edition
Chapter 13:
Ensuring Integrity and Availability
Objectives:
Identify the characteristics of a network that
keep data safe from loss or damage
Protect an enterprise-wide network from
viruses
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Objectives: (continued)
Explain network- and system-level faulttolerance techniques
Discuss issues related to network backup
and recovery strategies
Describe the components of a useful disaster
recovery plan
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What are Integrity and
Availability?
• Integrity refers to the soundness of a
network’s programs, data, services,
devices, and connections.
• Availability of a file or system refers to
how consistently and reliably it can be
accessed by authorized personnel
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What are Integrity and
Availability? (continued)
• General guidelines for protecting your
network
• Allow only network administrators to create or
modify NOS and application system files
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What are Integrity and
Availability? (continued)
• Monitor the network for unauthorized access or
changes
• Record authorized system changes in a change
management system
• Install redundant components
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What are Integrity and
Availability? (continued)
• General guidelines for protecting your
network (continued)
• Perform regular health checks on the network
• Check system performance, error logs, and the
system log book regularly
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What are Integrity and
Availability? (continued)
• Keep backups, boot disks, and emergency repair
disks current and available
• Implement and enforce security and disaster
recovery policies
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Viruses
• A virus is a program that replicates itself
with the intent to infect more computers
• Other unwanted and potentially
destructive programs are called viruses,
but technically do not meet the criteria
used to define a virus
• Program that disguises itself as something useful
but actually harms your system is called a Trojan
horse
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Viruses (continued)
• Types of Viruses
• Boot sector viruses, Macro viruses, File-infected
viruses, Worms, Trojan horse, Network viruses,
Bots
• Virus Characteristics
• Encryption, Stealth, Polymorphism, Timedependence
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Viruses (continued)
• Virus Protection
• Antivirus Software
• Suspecting a virus
• Unexplained increases in file sizes
• Significant, unexplained decline in system
performance
• Unusual error messages
• Significant, unexpected loss of system memory
• Fluctuations in display quality
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Viruses (continued)
• Virus Protection
• Antivirus Software
• Antivirus software should perform
• Signature scanning
• Integrity checking
• Monitoring of unexpected file changes
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Viruses (continued)
• Virus Protection
• Antivirus Software
• Antivirus software should perform (continued)
• Regular updates and modifications
• Consistently report only valid viruses
• Heuristic scanning -- most fallible
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Viruses (continued)
• Virus Protection
• Antivirus Policies
• Virus detection and cleaning software that regularly
scans for viruses
• Users not allowed to alter or disable
• Users know what to do
• Antivirus team appointed maintaining antivirus
measures
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Viruses (continued)
• Virus Protection
• Antivirus Policies (continued)
• Users prohibited from installing any unauthorized
software
• System-wide alerts issued
• Virus Hoaxes
• Type of rumor consists of a false alert about a
•
dangerous, new virus
Verify a possible hoax
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Fault Tolerance
• The capacity for a system to continue
performing despite an unexpected
hardware or software malfunction
• Failure is a deviation from a specified level of
system performance for a given period of time
• Fault involves the malfunction of one component
of a system
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Fault Tolerance (continued)
• Environment
• Analyze the physical environment in which your
devices operate
• Power
• Power Flaws
• Surge—A momentary increase in voltage
• Noise—A fluctuation in voltage levels
• Brownout—A momentary decrease in voltage
• Blackout—A complete power loss
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Fault Tolerance (continued)
• Power (continued)
• Uninterruptible Power Supplies (UPSs)
• Prevents A/C power from harming device or
interrupting its services
• Standby UPS provides continuous voltage to a
device by switching
• Online UPS providing power to a network
device through its battery
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Fault Tolerance (continued)
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Fault Tolerance (continued)
• Which UPS is right for your network
• Amount of power needed
• Period of time to keep a device running
• Line conditioning
• Cost
• Generators
• If your organization cannot withstand a power loss
you might consider investing in an electrical
generator for your building
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Fault Tolerance (continued)
• Topology and Connectivity
• Each physical topology inherently assumes certain
•
advantages and disadvantages
Supplying multiple paths data can use to travel
from any one point to another
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Fault Tolerance (continued)
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Fault Tolerance (continued)
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Fault Tolerance (continued)
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Fault Tolerance (continued)
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Fault Tolerance (continued)
• Servers
• Server Mirroring
• Mirroring is a fault-tolerance technique in which one
device or component duplicates the activities of
another
• In server mirroring, one server continually
duplicates the transactions and data storage of
another
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Fault Tolerance (continued)
•
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Fault Tolerance (continued)
• Servers
• Clustering
• Fault-tolerance technique that links multiple servers
together to act as a single server
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Fault Tolerance (continued)
• Storage
• Redundant Array of Independent (or Inexpensive)
Disks (RAID)
• Collection of disks that provide fault tolerance for
shared data and applications
• Hardware RAID
• Set of disks and a separate disk controller
• Software RAID
• Software to implement and control RAID
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Fault Tolerance (continued)
• Storage
• RAID (continued)
• RAID Level 0—Disk Striping RAID Level 0
• data is written in 64 KB blocks equally across all
disks in the array
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Fault Tolerance (continued)
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Fault Tolerance (continued)
• Storage
• RAID (continued)
• RAID Level 1—Disk Mirroring RAID Level 1
• provides redundancy through a process called
disk mirroring
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Fault Tolerance (continued)
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Fault Tolerance (continued)
• Storage
• RAID (continued)
• RAID Level 3—Disk Striping with Parity ECC RAID
Level 3
• Involves disk striping with a special error
correction code (ECC)
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Fault Tolerance (continued)
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Fault Tolerance (continued)
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Fault Tolerance (continued)
• Storage
• RAID (continued)
• RAID Level 5—Disk Striping with Distributed Parity
• Highly fault-tolerant
• Data is written in small blocks across several
disks
• Parity error checking information is distributed
among the disks
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Fault Tolerance (continued)
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Fault Tolerance (continued)
• Storage
• Network Attached Storage
• specialized storage device or group of storage
devices that provides centralized fault-tolerant data
storage for a network
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Fault Tolerance (continued)
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Fault Tolerance (continued)
• Storage
• Storage Area Networks (SANs)
• Distinct networks of storage devices that
communicate directly with each other and with other
networks
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Fault Tolerance (continued)
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Data Backup
• A backup is a copy of data or program
files created for archiving or safekeeping
• Tape Backups
• Copying data to a magnetic tape
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Data Backup (continued)
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Data Backup (continued)
• Tape Backups (continued)
• Select the appropriate tape backup solution
• Sufficient storage capacity
• Proven to be reliable
• Data error-checking techniques
• Is the system quick enough
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Data Backup (continued)
• Tape Backups (continued)
• Select the appropriate tape backup solution
• Tape drive, software, and media cost
• Hardware and software be compatible with
existing network
• Frequent manual intervention
• Accommodate your network’s growth
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Data Backup (continued)
• Online Backups
• Companies on the Internet now offer to back up
data over the Internet
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Data Backup (continued)
• Backup Strategy
• What data must be backed up
• What kind of rotation schedule
• When will the backups occur
• How will you verify
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Data Backup (continued)
• Backup Strategy (continued)
• Where will backup media be stored
• Who will take responsibility
• How long will you save backups
• Where will backup and recovery documentation be
stored
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Data Backup (continued)
• Backup Strategy (continued)
• Different backup methods
• Full backup
• Incremental backup
• Differential backup
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Data Backup (continued)
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Disaster Recovery
• A disaster recovery plan should identify a
disaster recovery team
• Contact for emergency coordinators
• Which data and servers are being backed up
• Network topology, redundancy, and agreements
• Regular strategies for testing
• A plan for managing the crisis
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Chapter Summary
• Integrity refers to the soundness of your
•
•
•
•
network’s files, systems, and connections
Several basic measures can be employed
to protect data and systems
A virus is a program that replicates itself
Boot sector viruses position their code in
the boot sector
Macro viruses take the form of a macro
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Chapter Summary (continued)
• File-infected viruses attach themselves to
•
•
•
•
executable files
Network viruses take advantage of
network protocols
A virus bot is a virus that spreads
automatically between systems
Worms are not technically viruses
A Trojan horse claims to do something
useful but instead harms
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Chapter Summary (continued)
• Any type of virus may have additional
•
•
characteristics that make it harder to
detect and eliminate
A good antivirus program should be able
to detect viruses through signature
scanning, integrity checking, and heuristic
scanning
Antivirus software is merely one piece of
the puzzle in protecting your network
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Chapter Summary (continued)
• A virus hoax is a false alert about a
•
dangerous, new virus
A failure is a deviation from a specified
level of system performance for a given
period of time
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Chapter Summary (continued)
• A fault is the malfunction of one
•
component of a system
Fault tolerance is a system’s capacity to
continue performing despite an
unexpected hardware or software
malfunction
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Chapter Summary (continued)
• Networks cannot tolerate power loss or
•
•
less than optimal power
A UPS is a battery power source directly
attached to one or more devices and to a
power supply
A standby UPS provides continuous
voltage to a device by switching
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Chapter Summary (continued)
• An online UPS uses the A/C power from
•
the wall outlet to continuously charge its
battery
For utmost fault tolerance in power
supply, a generator is necessary
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Chapter Summary (continued)
• Network topologies such as a full mesh
•
•
WAN or a star-based LAN with a parallel
backbone offer the greatest fault tolerance
Hot swappable components can be
changed (or swapped) while a machine is
still running (hot)
Critical servers often contain redundant
components
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Chapter Summary (continued)
• Utilizing a second, identical server to
•
duplicate the transactions and data
storage of one server is called server
mirroring
Server clustering links multiple servers
together to act as a single server
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Chapter Summary (continued)
• An important storage redundancy feature
•
•
is a Redundant Array of Independent (or
Inexpensive) Disks (RAID)
Network attached storage (NAS) is a
dedicated storage device
A storage area network (SAN) is a distinct
network of multiple storage devices and
servers
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Chapter Summary (continued)
• A backup is a copy of data or program
•
•
files created for archiving or safekeeping
A popular, economical method for backing
up networked systems is tape backup
You can also back up data over the
Internet
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Chapter Summary (continued)
• The aim of a good backup rotation scheme
•
is to provide excellent data reliability
Every organization should have a disaster
recovery team
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