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Dion (N10-008) > Network Availability > Flashcards

Network Availability Flashcards

1
Q

Availability

A

Concerned with being up & operational

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2
Q

Reliability

A

Concerned with not dropping packets

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3
Q

MTTR

A

Mean Time to Repair
Measures the average time it takes to repair a network device when it breaks

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4
Q

MTBF

A

Mean Time Between Failures
Measures the average time between failures of a device

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5
Q

Redundant Networks w/Single Point of Failure

A

Link Redundancy:
Internal Hardware Redundancy
(PSUs & NICs)

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6
Q

Redundant Networks w/No Single Points of Failure

A

Link Redundancy:
Redundancy of Components
(Switches & Routers)

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7
Q

Hardware Redundancy

A

(Takes many forms)
Devices with two NICs, HDDs/SSDs, or internal PSUs

Often found in strategic network devices
(Routers/Switches/Firewalls/Servers)
Usually not found in clients due to cost

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8
Q

Hardware Redundancy: Active-Active

A

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

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9
Q

Hardware Redundancy: Active-Standby

A

One NIC is active at a time
Client appears to have a single MAC address

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10
Q

Layer 3 Redundancy

A

Clients are configured with a default gateway (router)

If default gateway goes down, they cannot leave subnet

Layer 3 redundancy creates virtual gateways to avoid this issue

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11
Q

HSRP

A

Hot Standby Router Protocol:
Proprietary first-hop redundancy by Cisco
Allows for active router and standby router
Creates virtual router as the default gateway

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12
Q

CARP

A

Common Address Redundancy Protocol:
Open-standard variant of HSRP
Allows for active & standby router
Creates virtual router as default gateway

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13
Q

VRRP

A

Virtual Router Redundancy Protocol:
IETP open-standard variant of HSRP
Allows for active & standby router
Creates virtual router as default gateway

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14
Q

GLBP

A

Gateway Load Balancing Protocol:
Proprietary first-hop redundancy by Cisco
Focuses on load balancing over redundancy
Allows for active & standby router
Creates virtual router as default gateway

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15
Q

LACP

A

Ling Aggregation Control Protocol:
Achieves redundancy by having multiple links between devices
Load balancing occurs over multiple links
Multiple links appear as a single logical link

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16
Q

Availability Best Practices

A

Examine technical goals
Identify budget to fund high avail features

Categorize business apps into profiles
(Each requires certain level of availability)

Establish performance standards
Define how to manage & measure the solution
(Need metrics to quantify success)

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17
Q

Recovery Sites: Cold Sites

A

Building is available, but no hardware/software configured

Need to buy resources (or ship them in) and the configure network

Slow & time consuming recovery

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18
Q

Recovery Sites: Warm Sites

A

Building & equipment available

Software may not be installed & latest data unavailable

Recovery is fairly quick, but not everything from original site is available to employees

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19
Q

Recovery Sites: Hot Sites

A

Building, equipment, & data available
Software & hardware configured
Ready as soon as people walk in
Downtime is very minimal

20
Q

Backup Types

A

Full: Complete backup (time consuming & costly)

Incremental: Backup only data changed since last backup

Differential: Backup only data since last full backup

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

21
Q

QoS

A

Quality of Service:
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

22
Q

QoS Categories

A

Delay:
Time a packet travels from source to destination
Measured in ms

Jitter:
Uneven arrival of packets (harmful in VoIP/streaming)

Drops:
Occurs during link congestion
Router’s interface queue overflows & causes packet loss

23
Q

QoS Traffic Categorization

A

Determine network performance requirements for various traffic types (voice, video, data, etc)

Low delay: Voice, video streaming

Low priority: Web browsing, non-mission critical data

24
Q

QoS Traffic Categorization: Best Effort

A

Does not truly provide QoS to that traffic

No reordering of packets

Uses FIFO (first in, first out) queuing

25
Q

QoS Traffic Categorization: IntServ

A

Integrated Services (IntServ/Hard QoS):
Makes strict bandwidth reservations

Reserves bandwidth by signaling devices

26
Q

QoS Traffic Categorization: DiffServ

A

Differentiated Services (DiffServ/Soft QoS):
Differentiates between multiple traffic flows
Packets are “marked”
Routers/switches make decisions based on markings

27
Q

QoS Traffic Categorization Methods

A

Classification
Marking
Congestion management
Congestion avoidance
Policing & shaping
Link efficiency

28
Q

Marking of Traffic

A

Altered bits within a frame/cell/packet indicates handling of traffic

Network tools make decisions based on markings

29
Q

Congestion Management

A

Queuing: When a device receives traffic faster than it can be transmitted, it buffers the extra traffic until bandwidth is available

Queuing algorithm empties the packets in specified sequence & amount

Queuing Algorithm types:
Weighted fair queuing
Low-latency queuing
Weighted round-robin

30
Q

Congestion Avoidance

A

Newly arriving packets would be discarded if the device’s output queue fills to capacity

If TCP: Will be retransmitted
If UDP: Will be dropped

31
Q

Congestion Avoidance: RED

A

Random Early Detection:

As the queue fills, the possibility of a discard increases until it reaches 100%
At 100%, all of that traffic type is dropped

RED instead drops packets from selected queues based on defined limits

32
Q

Policing

A

Typically discards packets that exceed a configured rate limit (speed limit)

Recommended for higher-speed interfaces

33
Q

Shaping

A

Buffers (delays) traffic exceeding configured rate

Recommended for slower-speed interfaces

34
Q

Link Efficiency: Compression

A

Packet payload is compressed to conserve bandwidth

VoIP payload can be reduced by 50%
(40 bytes to 20 bytes)

VoIP header can be reduced by 90-95%
Uses RTP header compression (cRTP)
(40 bytes to 2-4 bytes)

Utilized on slower-speed links to make most of limited bandwidth

35
Q

Link Efficiency: LFI

A

Link Fragmentation & Interleaving:

Fragments large data packets & interleaves smaller data packets between the fragments

Utilized on slower-speed links to make the most of limited bandwidth

36
Q

Multipathing

A

Creates more than one physical path between the server & its storage devices for better fault tolerance & performance

37
Q

Designing Redundant Networks

A

Examine technical/operational goals
Identify the budget to fund high-availability features
Categorize business apps into profiles
Establish performance standards for high-availability solutions
Define how to manage & measure the high-availability solutions

(Time vs Cost vs Quality)

38
Q

Recovery Sites: Cloud Site

A

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

39
Q

Recovery Sites: Cloud Site - RTO

A

Recovery Time Objective:
Time & service level within which a business process must be restored after a disaster to avoid unacceptable consequences

How much time did it take to recovery after the notification of a business process disruption?

For low RTO situations: Use a hot or cold site

40
Q

Recovery Sites: Cloud Site - RPO

A

Recovery Point Objective:
Interval of time during a disruption before data lost exceeds the BCP’s (business continuity plan) maximum allowable threshold or tolerance

41
Q

Facilities Support: UPS

A

Uninterruptible Power Supply:
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)

42
Q

Facilities Support: PDU

A

Power Distribution Unit:
Distributes electric power, especially to racks of computers & networking equipment located within a data center

PDUs combined with a UPS or generator can provide power during a blackout

43
Q

Facilities Support: Generator

A

Provides long-term power during a power outage in a region

Takes a while to start up
Hot & cold aisle concept

44
Q

Facilities Support: Wet Pipe System

A

Using a sprinkler system & pipes that always contain water

45
Q

Facilities Support: Pre-Action System

A

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

Dion (N10-008) (27 decks)

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