Network Availability

CompTIA+ Network Learning

Network availability

Network availability

A measure of how well a computer network can respond to connectivity and performance demands, usually quantitatively measured as uptime.

Five nines of availability

The gold standard in network availability, referring to an uptime of 99.999%.

Downtime

Periods when the network is not operational due to device failures, connection issues, or incorrect configurations.

Availability and reliability

Availability refers to the network being up and operational, while reliability refers to the network not dropping packets.

Mean time to repair (MTTR)

The average time it takes to repair a network device when it breaks.

Mean time between failures (MTBF)

The average time between when a failure happens on a device and the next failure happens.

Redundancy

Adding duplicate devices or components to a network to ensure high availability and reliability.

Hardware redundancy

Having duplicate network devices or components to provide backup in case of failure.

Active-active configuration

A clustering configuration where multiple network interface cards are active at the same time, increasing bandwidth and load balancing.

Network Interface Card teaming (NIC teaming)

Using a group of network interface cards for load balancing and failover for a server or device.

Active-Passive

A configuration in which one network interface card is active and being used at all times, while the other card serves as a backup and takes over when the active card fails.

Redundancy

The use of backup or redundant components to ensure continuous operation and prevent system failure.

First Hop Redundancy Protocol (FHRP)

A layer three redundancy protocol used to create a virtual gateway for client devices in the event of a default gateway failure.

Hot Standby Router Protocol (HSRP)

A proprietary FHRP used in Cisco devices to provide layer three redundancy by allowing an active and standby router to be used together.

Virtual Router Redundancy Protocol (VRRP)

An open standard variant of HSRP that allows for one master or active router and multiple standby routers to be used together.

Gateway Load Balancing Protocol (GLBP)

A proprietary FHRP used in Cisco devices to provide load balancing and redundancy between two routers or gateways.

Link Aggregation Control Protocol (LACP)

A redundancy protocol used at layer two to achieve redundancy and increase bandwidth by aggregating multiple links between network devices.

Multipathing

A redundancy technique used in storage area networks to create multiple physical paths between servers and storage devices for better fault tolerance and performance enhancements.

Diversity

The use of multiple paths or connections from different providers to ensure redundancy and prevent complete loss of connectivity.

Software Redundancy

The use of software-based solutions, such as virtual switches or software RAID, to provide redundancy instead of relying on additional hardware components.

Design Considerations

Factors to consider when designing a redundant network, including the choice between module or chassis redundancy, software redundancy options, and protocol characteristics.

Power Redundancy

Redundancy features used to maintain continuous power supply to infrastructure devices, such as internal power supplies, battery backups, or generators.

Environmental Redundancy

Redundancy features used to maintain optimal environmental conditions, such as power, space, and cooling, for network equipment.

Air conditioning

The system used to cool and regulate the temperature of a space.

Redundancy

The duplication of critical components or systems to ensure continuous operation in case of failure.

Server farm

A collection of servers that work together to provide a large amount of computing power and storage.

Uptime

The amount of time a system or network is operational and available for use.

High-availability

The design and implementation of systems that are continuously operational and accessible.

NAS (Network Attached Storage)

A device that provides file storage and sharing capabilities over a network.

RAID (Redundant Array of Independent Disks)

A data storage technology that combines multiple physical disks into a single logical unit for improved performance, reliability, or both.

Cloud server

A virtual server that is hosted and operated by a cloud computing provider.

Metrics

Quantifiable measures used to evaluate the performance or success of a system or network.

Recovery sites

Alternate locations where a company can continue its operations in the event of a disaster or disruption.

Hot site

A secondary site that is fully operational and ready to take over operations in the event of a disaster, with minimal downtime.

Recovery time objective (RTO)

The duration of time within which a business process must be restored after a disaster to avoid unacceptable consequences.

Recovery point objective (RPO)

The interval of time that might pass during a disruption before the quantity of data loss exceeds the maximum allowable threshold.

Cloud site

A virtual recovery site in the cloud that allows organizations to create a recovery version of their network and shift operations to telework in the event of a disaster.

Full backup

A complete backup of every single file on a machine, ensuring the safest and most comprehensive backup method, but also the most time-consuming and costly.

Incremental backup

A backup that only backs up the data that has changed since the last backup, reducing time and disk space requirements.

Differential backup

A backup that backs up the data since the last full backup, including all changes made since the last full backup.

Snapshot

A read-only copy of data frozen in time, commonly used in virtualization for dynamic analysis or restoring to a clean state after malware analysis.

State of a network device

The configuration and dynamic information of a network device at any given time, which can be exported and restored to the same or another device.

Configuration backup

Backing up the configuration information of a network device, usually done using the command line interface or third-party tools.

Facilities support

Support for power, cooling, and fire suppression in data centers and recovery sites, including uninterrupted power supplies, generators, HVAC, and fire suppression systems.

Uninterruptible Power Supply (UPS)

An electrical apparatus that provides emergency power to a load when the main power source is going to fail.

Power Distribution Unit (PDU)

A device fitted with multiple outputs designed to distribute electrical power, especially to racks of computers and networking equipment in data centers.

Generator

A device that provides long-term power during a power outage, usually powered by diesel, gasoline, or propane.

HVAC Units

Heating, ventilation, and air conditioning systems used in data centers to cool down servers and networking equipment to prevent overheating.

Fire Suppression Systems

Built-in systems in data centers to suppress fires, including wet pipe sprinklers, pre-action sprinklers, and special suppression systems using clean agent agents or inert gases.

Effective bandwidth

The lowest bandwidth among all the connections in a network, which determines the overall speed of data transfer.

Quality of service

Categorizing network traffic and assigning priorities to different types of data based on their importance and requirements.

Traffic categorization

Classifying network traffic into different buckets or categories based on their type, such as web traffic, email traffic, and voice or video traffic.

Best effort

A quality of service approach where there are no strict policies or reservations for bandwidth, and traffic is handled on a first-come, first-served basis.

Integrated services

A hard quality of service approach where strict bandwidth reservations are made for different types of traffic, ensuring a specific amount of bandwidth for each category.

Differentiated services

A soft quality of service approach where traffic is marked and categorized, allowing routers and switches to make decisions based on those markings to prioritize traffic dynamically.

Classification and marking

The process of categorizing network traffic and assigning specific markings or labels to each packet based on its category or priority.

Congestion management

Techniques used to control and manage network congestion, such as prioritizing certain types of traffic or implementing traffic shaping.

Congestion avoidance

Strategies employed to prevent network congestion from occurring, usually by monitoring network conditions and adjusting traffic flow accordingly.

Policing and shaping

Methods used to control and regulate network traffic, such as limiting the rate of incoming or outgoing packets (policing) or adjusting the traffic flow to match a specific rate (shaping).

Link efficiency

Techniques aimed at optimizing the utilization of network links, ensuring that bandwidth is used efficiently and effectively.

Traffic Classification

The process of categorizing network traffic based on its type, such as email, POP3, IMAP, SMTP, or Exchange, to determine priority and quality of service.

Traffic Marking

Altering the bits within a frame, cell, or packet to indicate how the traffic should be handled by network tools based on priority and QoS requirements.

Congestion Management

Mechanisms used to handle traffic when a device receives more traffic than it can transmit, including weighted fair queuing, low-latency queuing, and weighted round-robin.

Congestion Avoidance

Techniques such as Random Early Detection (RED) to prevent overflow in output queues by dropping packets based on priority.

Policing

Discarding packets that exceed the configured rate limit to enforce speed limits on the network.

Shaping

Allowing the buffer to delay traffic from exceeding the configured rate, holding packets in the buffer and shaping them out when there is available space.

Link Efficiency

Strategies to maximize bandwidth utilization, including compression of packets to conserve bandwidth and WAN accelerators for optimizing data transfer on slower speed links.

LFI

Stands for Link Fragmentation and Interleaving. It is a method used to optimize the use of WAN links by breaking up large packets and interleaving smaller packets between them.

Link fragmentation

The process of dividing large packets into smaller fragments to improve the efficiency of data transmission over slower speed links.

Interleaving

The technique of inserting smaller packets between the fragments of larger packets to minimize latency and prioritize high priority traffic.

Bandwidth

The maximum amount of data that can be transmitted over a network connection in a given period of time.

Voice packets

Small packets of data that carry voice signals over a network.

Data packets

Packets of information that contain data to be transmitted over a network.

Latency

The delay or lag experienced in data transmission, often measured in milliseconds.