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CompTIA Network+ (N10-008) > Network Availability (2.2 & 3.3) > Flashcards

Network Availability (2.2 & 3.3) Flashcards

1
Q

Network Availability

A

o Measure of how well a computer network can respond to connectivity and
performance demands that are placed upon it

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2
Q

High Availability

A

▪ Availability is measured by uptime
▪ Five nines of availability (99.999%)
▪ Maximum of 5 minutes of downtime per year

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3
Q

Availability

A

o Concerned with being up and operational

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4
Q

Reliability

A

o Concerned with not dropping packets

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5
Q

Mean Time to Repair (MTTR)

A

o Measures the average time it takes to repair a network

device when it breaks

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6
Q

Mean Time Between Failures (MTBF)

A

o Measures the average time between failures of a device

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7
Q

Redundant Network with Single Points of Failure

A

▪ Link Redundancy (Multiple connections between devices)

● Internal Hardware Redundancy (Power supplies and NICs)

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8
Q

Redundant Network with No Single Points of Failure

A

▪ Link Redundancy (Multiple connections between devices)

● Redundancy of Components (Switches and Routers)

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9
Q

Hardware Redundancy

A

▪ Takes many forms
▪ Devices with two network interface cards (NICs), hard drives, or internal
power supplies
▪ Often found in strategic network devices
● Routers, Switches, Firewalls, and Servers
● Not often found in clients due to costs and administrative
overhead involved in management

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10
Q

Active-Active

A

▪ Multiple NICs are active at the same time
▪ NICs have their own MAC address
▪ Makes troubleshooting more complex

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11
Q

Active-Passive

A

▪ One NIC is active at a time

▪ Client appears to have a single MAC address

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12
Q

Network Interface Card Teaming

A

Network Interface Card Teaming
▪ Using a group of network interface cards for load balancing and failover
on a server or other device

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13
Q

Layer 3 Redundancy

A

▪ Clients are configured with a default gateway (router)
● If the default gateway goes down, they cannot leave the subnet
● Layer 3 Redundancy occurs with virtual gateways

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14
Q

Hot Standby Router Protocol (HSRP)

A

▪ Proprietary first-hop redundancy by Cisco
▪ Allows for active router and standby router
▪ Creates virtual router as the default gateway

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15
Q

Virtual Router Redundancy Protocol (VRRP)

A

▪ IETP open-standard variant of HSRP
▪ Allows for active router and standby router
▪ Creates virtual router as the default gateway

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16
Q

Gateway Load Balancing Protocol (GLBP)

A

▪ Proprietary first-hop redundancy by Cisco
▪ Focuses on load balancing over redundancy
▪ Allows for active router and standby router
▪ Creates virtual router as the default gateway

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17
Q

Link Aggregation Control Protocol (LACP)

A

▪ Achieves redundancy by having multiple links
between devices
▪ Load balancing occurs over multiple links
▪ Multiple links appear as single logical link

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18
Q

Link Aggregation Control Protocol (LACP)

A

▪ Achieves redundancy by having multiple links
between devices
▪ Load balancing occurs over multiple links
▪ Multiple links appear as single logical link
▪ Creates more than one physical path between the server and its storage
devices for better fault tolerance and performance

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19
Q

Design Considerations

A

▪ Where will redundancy be used?
● Module (or Parts) Redundancy
● Chassis Redundancy
▪ What software redundancy features are appropriate?
▪ What protocol characteristics affect design requirements?
▪ What redundancy features should be used to provide power to an
infrastructure device?
▪ What redundancy features should be used to maintain environmental
conditions?

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20
Q

Best Practices

A

est Practices
▪ Examine the technical goals
▪ Identify the budget to fund high availability features
▪ Categorize business applications into profiles
● Each requires a certain level of availability
▪ Establish performance standards for high-availability solutions
● Performance standards will drive how success is measured
▪ Define how to manage and measure the high-availability solution
● Metrics help quantify success to decision makers

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21
Q

Remember…

A

▪ Existing networks can be retrofitted, but it reduces the cost by integrating
high availability practices and technologies into your initial designs

22
Q

Cold Sites

A

old Sites
▪ An available building that does not have any hardware or software in
place or configured
▪ While recovery is possible, it is going to be slow and time-consuming

23
Q

Warm Sites

A

▪ An available building that already contains a lot of the equipment
▪ Restoral time is between 24 hours and seven days

24
Q

Hot Sites

A

▪ An available building that already has the equipment and data in place
and configured
▪ Minimal downtime and with nearly identical service levels maintained

25
Q

Cloud Site

A

▪ Allows for the creation of a recovery version of an organization’s
enterprise network in the cloud

26
Q

Recovery Time Objective (RTO)

A

o Time and service level within which a business process
must be restored after a disaster to avoid unacceptable
consequences
o How much time did it
take to recover after the notification of a business process
disruption?
o Use either a hot site or a cloud site for low RTO situations

27
Q

Recovery Point Objective (RPO)

A

o Interval of time during a disruption before data lost
exceeds the BCP’s maximum allowable threshold or
tolerance

28
Q

Backup and Recovery

A

▪ Full
● Complete backup is the safest and most comprehensive; Time
consuming and costly

▪ Incremental
● Backup only data changed since last backup

▪ Differential
● Only backups data since the last full backup

▪ Snapshots
● Read-only copy of data frozen in time (VMs)

29
Q

Uninterruptible Power Supply (UPS)

A

▪ Provides emergency power to a load when the input power source or
main power fails
▪ Great for short duration power outages (less than 15 minutes)

30
Q

Power Distribution Unit (PDU)

A

▪ Distributes electric power, especially to racks of computers and
networking equipment located within a data center
▪ PDUs combined with a UPS or a generator can provide power during a
blackout

31
Q

Generator

A

▪ Provides long-term power during a power outage in a region
● Takes a while to start up
● Hot and cold aisle concept

32
Q

Wet Pipe System

A

▪ Using a sprinkler system and pipes that always contain water

33
Q

Pre-Action System

A

▪ A detector actuation like a smoke detector and a sprinkler must be
tripped prior to water being released

34
Q

Need for Quality of Service (QoS)

A

▪ Networks carry data, voice, and video content
▪ Convergence of media on the network requires high availability to ensure
proper delivery
▪ Optimizing the network to efficiently utilize the bandwidth to deliver
useful solutions to network users is crucial to success and cost savings

35
Q

Quality of Service (QoS)

A

▪ Enables strategic optimization of network performance for different
types of traffic
● Identifies types of traffic needing priority
● Determines how much bandwidth required
● Efficiently uses WAN link’s bandwidth
● Identifies types of traffic to drop during network congestion
▪ For example:
● Voice (VoIP) and Video should have higher priority levels (less
latency)

36
Q

Categories of QoS

A 
▪ Delay
● Time a packet travels from source to destination
● Measured in milliseconds (ms)
▪ Jitter
● Uneven arrival of packets
● Especially harmful in VoIP
▪ Drops
● Occurs during link congestion
● Router’s interface queue overflows and causes packet loss
37
Q

“Effective” Bandwidth

A

Pictures

38
Q

“Effective” Bandwidth

A

Pictures

39
Q

Purpose of QoS

A

▪ To categorize traffic, apply a policy to those traffic categories, and
prioritize them in accordance with a QoS policy

40
Q

Categorization of Traffic

A

ategorization of Traffic
▪ Determine network performance requirements for various traffic types
(Voice, Video, Data)
▪ Categorize traffic into specific categories:
● Low delay
o Voice
o Streaming Video
● Low priority
o Web browsing
o Non-mission critical data
▪ Document your QoS policy and make it available to your users

41
Q

Best Effort

A 
● Does not truly provide
QoS to that traffic
● No reordering of packets
● Uses FIFO (first in, first
out) queuing
42
Q 
Integrated Services (IntServ or
Hard QoS)
A

● Makes strict bandwidth
reservations
● Reserves bandwidth by signaling devices

43
Q

Differentiated Services (DiffServ or Soft QoS)

A

● Differentiates between multiple traffic flows
● Packets are “marked”
● Routers and switches make decisions based on those markings

44
Q

Methods of Categorizing Traffic

A 
▪ Classification
▪ Marking
▪ Congestion management
▪ Congestion avoidance
▪ Policing and shaping
▪ Link efficiency
45
Q

Ways of Categorizing Traffic

A 
▪ Classification
▪ Marking
▪ Congestion management
▪ Congestion avoidance
▪ Policing and shaping
▪ Link efficiency
46
Q

Classification of Traffic

A

▪ Traffic is placed into different categories
▪ For example, the E-mail class might contain various types of traffic
● POP3
● IMAP
● SMTP
● Exchange
▪ Classification does not alter any bits in the frame or packet

47
Q

Marking of Traffic

A

▪ Altered bits within a frame, cell, or packet indicates handling of traffic
▪ Network tools make decisions based on markings

48
Q

Congestion Management

A

▪ When a device receives traffic faster than it can be transmitted, it buffers
the extra traffic until bandwidth becomes available
● Called queuing
▪ Queuing algorithm empties the packets in specified sequence and
amount
▪ Queuing algorithms types
● Weighted fair queuing
● Low-latency queuing
● Weighted round-robin

49
Q

Congestion Avoidance

A

▪ Newly arriving packets would be discarded if the device’s output queue
fills to capacity
▪ Random Early Detection (RED) is used to prevent this from occurring
● As the queue fills, the possibility of a discard increases until it
reaches 100%
● If at 100%, all traffic of that type is dropped
● RED instead drops packets from selected queues based on
defined limits
▪ If TCP traffic, it will be retransmitted
▪ If UDP, it will simply be dropped

50
Q

Policing and Shaping

A

▪ Policing
● Typically discards packets that exceed a configured rate limit
(speed limit)
● Dropped packets result in retransmissions
● Recommended for higher-speed interfaces
▪ Shaping
● Buffers (delays) traffic exceeding configured rate
● Recommended for slower-speed interfaces

51
Q

Link Efficiency: Compression

A

▪ Packet payload is compressed to conserve bandwidth
▪ VoIP payload can be reduced by 50%
● Payload size from 40 bytes to 20 bytes
▪ VoIP header can be reduced by 90-95%
● Uses RTP header compression (cRTP)
● Header size goes from 40 bytes to 2 to 4 bytes
▪ Utilized on slower-speed links to make most of limited bandwidth

52
Q

Link Efficiency: LFI

A

▪ Link Fragmentation & Interleaving (LFI)
▪ Fragments large data packets and interleaves smaller data packets
between the fragments
▪ Utilized on slower-speed links to make the most of limited bandwidth

CompTIA Network+ (N10-008) (23 decks)

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