2.7 MODERN NETWORKING ELEMENTS IN MODERN COMPUTER NETWORK
2.7 MODERN NETWORKING ELEMENTS
QUALITY OF EXPERIENCE (QOE)
QoE is a subjective measure of performance as reported by the user. Unlike QoS, which can be precisely measured, QoE relies on human opinion. QoE is important particularly when we deal with multimedia applications and multimedia content delivery. QoS provides measurable, quantitative targets that guide the design and operation of a network and enable customer and provider to agree on what quantitative performance the network will deliver for give applications and traffic flows.
However, QoS processes by themselves are not sufficient in that they do not take into account the user’s perception of network performance and service quality. Although the maximum capacity may be fixed at a certain value by a media transmission system, this does not necessarily fix the quality of the multimedia content at, say, “high.” This is because there are numerous ways the multimedia content could have been encoded, giving rise to differing perceived qualities. The ultimate measure of a network and the services it offers is how subscribers perceive the performance. QoE augments the traditional QoS by providing information regarding the delivered services from an end user point of view.
There is a wide range of factors and features that can be included in a requirement for QoE, which can, roughly, be classified into the following categories:
Perceptual: This category encompasses the quality of the sensory aspects of the user experience. For video, examples include sharpness, brightness, contrast, flicker, and distortion. Audio examples include clarity and timbre.
Psychological: This category deals with the user’s feeling about the experience. Examples include ease of use, joy of use, usefulness, perceived quality, satisfaction, annoyance, and boredom.
Interactive: This category deals with aspects of an experience related to the interaction between the user and the application or device, such as responsiveness, naturalness of interaction, communication efficiency, and accessibility.
For practical application, these features need to be converted to quantitative measures. The management of QoE has become a crucial concept in the deployment of future successful applications, services, and products. The greatest challenges in providing QoE are developing effective methods for converting QoE features to quantitative measures and translating QoE measures to QoS measures. Whereas QoS can now easily be measured, monitored, and controlled at both the networking and application layers, and at both the end system and network sides, QoE is something that is still quite intricate to manage.
QUALITY OF SERVICE (QOS)
You can define QoS as the measurable end-to-end performance properties of a network service, which can be guaranteed in advance by a service level agreement (SLA) between a user and a service provider, so as to satisfy specific customer application requirements. Commonly specified properties include the following: Throughput: A minimum or average throughput, in bytes per second or bits per second, for a given logical connection or traffic flow.
Delay: The average or maximum delay. Also called latency.
Packet jitter: Typically, the maximum allowable jitter.
Error rate: Typically maximum error rate, in terms of fraction of bits delivered in error.
Packet loss: Fraction of packets lost.
Priority: A network may offer a given number of levels of priority. The assigned level for various traffic flows influences the way in which the different flows are handled by the network.
Availability: Expressed as a percentage of time available.
Security: Different levels or types of security may be defined.
QoS mechanisms ensure that business applications continue to receive the necessary performance guarantee even though they no longer run on dedicated hardware, such as when applications are transferred to a cloud. The QoS provided by an infrastructure is partially determined by its overall performance and efficiency. However, QoS is also the ability to prioritize specific workloads and allocate the needed resources to meet required service levels. It can offer a powerful way to allocate processor, memory, I/O, and network traffic resources among applications and virtual guests.
network functions virtualization (NFV)
The virtualization of network functions by implementing these functions in software and running them on virtual machines.
NFV has a number of features in common with SDN.
They share the following objectives:
NFV and SDN are independent but complementary schemes. SDN decouples the data and control planes of network traffic control, making the control and routing of network traffic more flexible and efficient. NFV decouples network functions from specific hardware platforms via virtualization to make the provision of these functions more efficient and flexible. Virtualization can be applied to the data plane functions of the routers and other network functions, including SDN controller functions. So, either can be used alone, but the two can be combined to reap greater benefits.
SOFTWARE DEFINED NETWORKING (SDN)
This constitutes the SDN control plane, and consists of one or more SDN controllers. The SDN controller defines the data flows that occur in the SDN data plane. Each flow through the network is configured by the controller, which verifies that the communication is permissible by the network policy. If the controller allows a flow requested by an end system, it computes a route for the flow to take, and adds an entry for that flow in each of the switches along the path. With all complex function subsumed by the controller, switches simply manage flow tables whose entries can only be populated by the controller.
The switches constitute the data plane. Communication between the controller and the switches uses a standardized protocol.
Network Devices
Network devices are physical devices that are required for communication and interaction between hardware on a computer network
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QUALITY OF EXPERIENCE (QOE)
QoE is a subjective measure of performance as reported by the user. Unlike QoS, which can be precisely measured, QoE relies on human opinion. QoE is important particularly when we deal with multimedia applications and multimedia content delivery. QoS provides measurable, quantitative targets that guide the design and operation of a network and enable customer and provider to agree on what quantitative performance the network will deliver for give applications and traffic flows.
However, QoS processes by themselves are not sufficient in that they do not take into account the user’s perception of network performance and service quality. Although the maximum capacity may be fixed at a certain value by a media transmission system, this does not necessarily fix the quality of the multimedia content at, say, “high.” This is because there are numerous ways the multimedia content could have been encoded, giving rise to differing perceived qualities. The ultimate measure of a network and the services it offers is how subscribers perceive the performance. QoE augments the traditional QoS by providing information regarding the delivered services from an end user point of view.
There is a wide range of factors and features that can be included in a requirement for QoE, which can, roughly, be classified into the following categories:
Perceptual: This category encompasses the quality of the sensory aspects of the user experience. For video, examples include sharpness, brightness, contrast, flicker, and distortion. Audio examples include clarity and timbre.
Psychological: This category deals with the user’s feeling about the experience. Examples include ease of use, joy of use, usefulness, perceived quality, satisfaction, annoyance, and boredom.
Interactive: This category deals with aspects of an experience related to the interaction between the user and the application or device, such as responsiveness, naturalness of interaction, communication efficiency, and accessibility.
For practical application, these features need to be converted to quantitative measures. The management of QoE has become a crucial concept in the deployment of future successful applications, services, and products. The greatest challenges in providing QoE are developing effective methods for converting QoE features to quantitative measures and translating QoE measures to QoS measures. Whereas QoS can now easily be measured, monitored, and controlled at both the networking and application layers, and at both the end system and network sides, QoE is something that is still quite intricate to manage.
QUALITY OF SERVICE (QOS)
You can define QoS as the measurable end-to-end performance properties of a network service, which can be guaranteed in advance by a service level agreement (SLA) between a user and a service provider, so as to satisfy specific customer application requirements. Commonly specified properties include the following: Throughput: A minimum or average throughput, in bytes per second or bits per second, for a given logical connection or traffic flow.
Delay: The average or maximum delay. Also called latency.
Packet jitter: Typically, the maximum allowable jitter.
Error rate: Typically maximum error rate, in terms of fraction of bits delivered in error.
Packet loss: Fraction of packets lost.
Priority: A network may offer a given number of levels of priority. The assigned level for various traffic flows influences the way in which the different flows are handled by the network.
Availability: Expressed as a percentage of time available.
Security: Different levels or types of security may be defined.
QoS mechanisms ensure that business applications continue to receive the necessary performance guarantee even though they no longer run on dedicated hardware, such as when applications are transferred to a cloud. The QoS provided by an infrastructure is partially determined by its overall performance and efficiency. However, QoS is also the ability to prioritize specific workloads and allocate the needed resources to meet required service levels. It can offer a powerful way to allocate processor, memory, I/O, and network traffic resources among applications and virtual guests.
network functions virtualization (NFV)
The virtualization of network functions by implementing these functions in software and running them on virtual machines.
NFV has a number of features in common with SDN.
They share the following objectives:
- Move functionality to software
- Use commodity hardware platforms instead of proprietary platforms
- Use standardized or open application program interfaces (APIs)
- Support more efficient evolution, deployment, and repositioning of network functions
NFV and SDN are independent but complementary schemes. SDN decouples the data and control planes of network traffic control, making the control and routing of network traffic more flexible and efficient. NFV decouples network functions from specific hardware platforms via virtualization to make the provision of these functions more efficient and flexible. Virtualization can be applied to the data plane functions of the routers and other network functions, including SDN controller functions. So, either can be used alone, but the two can be combined to reap greater benefits.
SOFTWARE DEFINED NETWORKING (SDN)
This constitutes the SDN control plane, and consists of one or more SDN controllers. The SDN controller defines the data flows that occur in the SDN data plane. Each flow through the network is configured by the controller, which verifies that the communication is permissible by the network policy. If the controller allows a flow requested by an end system, it computes a route for the flow to take, and adds an entry for that flow in each of the switches along the path. With all complex function subsumed by the controller, switches simply manage flow tables whose entries can only be populated by the controller.
The switches constitute the data plane. Communication between the controller and the switches uses a standardized protocol.
Network Devices
Network devices are physical devices that are required for communication and interaction between hardware on a computer network
- Hub
- Switch
- Router
- Bridge
- Gateway
- Modem
- Repeater
- Access Point
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