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    What is Qos?

    Quality of service (QoS) is the use of mechanisms or technologies that work on a network to control traffic and ensure the performance of critical applications with limited network capacity. It enables organizations to adjust their overall network traffic by prioritizing specific high-performance applications.

    Why is QoS important?

    Without QoS, the applications and services running on the network can degrade to a point where there is an unacceptable user experience, clogging networks to the point where performance degrades or, in certain cases, the network shuts down completely. Quality of service is important because enterprises need to provide stable services for employees and customers to use.

    For example, QoS policies are integral for businesses that rely on live video meetings, online training, and media streaming to function in their day-to-day tasks. QoS prevents the delivery of these types of data from being jeopardized by high traffic levels on the network.

    How does QoS work?

    QoS networking technology works by marking packets to identify service types, then configuring routers to create separate virtual queues for each application, based on their priority. As a result, bandwidth is reserved for critical applications or websites that have been assigned priority access.

    QoS addresses the following issues:

    • Latency 

    Latency is the amount of time it takes for a packet to venture from the source to its intended IP address. Ideally, the latency of these packets should be as close to zero as possible. Still, it can result in an echo effect for the recipient or overlapping audio in IP audio and voice packets if latency occurs.

    Network latency can be a common and troublesome issue for IT departments if real-time transport protocol (RTP) packets are left unclassified. Classification and prioritization are essential in these cases to avoid latency issues in video and audio IP exchanges.

    • Jitter 

    Jitter is another ill-effect of network congestion and results in a degradation in voice quality, audio, and video data. The irregular signal pulses often result in erratic distribution and speed of data packets between IP addresses – this can cause flickering effects, gaps in audio or imagery and out-of-sequence packet delivery.

    • Packet Loss 

    Packet loss is, as it sounds, the loss of data packets because of congestion on a network. Packet loss occurs when the router or switch must disregard inbound data packets due to overload until the issue is resolved. With QoS effectively in place, the steady stream of traffic is supported, meaning packets don’t drop out completely. Prioritization policies dictate that types of data are pipelined accordingly and eradicate jams within a congested network.

    • Bandwidth

    Bandwidth refers to the maximum amount of data that can be transmitted over a network or communication channel in a given period of time. It is commonly expressed in terms of bits per second (bps) or multiples of it, such as kilobits per second (Kbps), megabits per second (Mbps), or gigabits per second (Gbps). By monitoring network bandwidth, network administrators can assess the available capacity and determine if it meets the demands of the connected devices and applications.

    Other valuable tools and technologies that can be employed alongside QoS to monitor, analyze, and optimize network performance are as follows:

    • Packet Capture helps in analyzing the characteristics and behavior of network traffic, which is essential for effective QoS implementation. By capturing packets, network administrators can examine important QoS parameters, such as latency, jitter, packet loss and bandwidth utilization. This information allows them to identify and address network performance issues, determine if QoS policies are being properly applied, and optimize the network to meet specific QoS requirements.
    • Packet Analysis involves examining captured packets to gain insights into network behavior, identify patterns, and detect anomalies. It helps in understanding the performance of network applications, identifying bottlenecks, and optimizing network configurations. By analyzing packet-level data, network administrators can assess the impact of QoS mechanisms and fine-tune them for better performance.
    • Flow Monitoring, a subset of network monitoring, is a technique used to track and monitor the flow of network traffic. It involves collecting data on network flows, which represent sequences of packets that share common characteristics, such as source and destination IP addresses, ports, and protocols. Flow monitoring provides visibility into network traffic patterns, bandwidth utilization, and application behavior. It can help identify congestion points, detect abnormal traffic patterns, and optimize QoS policies to address specific network issues.
    • SD-WAN (Software-Defined Wide Area Network) is a technology that enhances network connectivity and performance by dynamically managing and optimizing network traffic. SD-WAN solutions use software-defined networking principles to intelligently route traffic across multiple network paths, including MPLS, internet, and other connections. By prioritizing critical applications, optimizing traffic flows, and leveraging QoS mechanisms, SD-WAN can address problems such as latency, packet loss, and bandwidth contention. It provides organizations with greater control and flexibility in managing their network resources, ensuring reliable and efficient performance for applications and services.

    Benefits of QoS

    • Guaranteed Performance for Critical Applications: QoS ensures the correct allocation of network resources, making sure that critical applications and services receive the necessary bandwidth and priority.
    • Enhanced User Experience: By prioritizing important traffic, such as voice communications, QoS provides a high-quality user experience and minimizes issues like dropped calls and video buffering.
    • Traffic Management: Administrators can control and manage the flow of traffic based upon predefined policies and rules.  They can set priorities, manage traffic during peak periods, and allocate bandwidth.
    • Reliability: QoS reduces network congestion and allows for load balancing.  It ensures that important applications and services are available during peak times. This is very important for businesses that need continuous connectivity and for services to be available to their customers.

    QoS Best Practices & Techniques

    A successful QoS implementation begins with planning.  To begin, the enterprise must first define the business objectives for QoS. Next, analyze the traffic requirements of the different applications being used by the organization.  The process of analyzing can provide valuable information as to the current state of the network and a baseline for the types and quantities of data flows being processed. It’s the fastest and easiest way to identify areas of congestion, network misconfigurations, and any other network issues that might impact the usefulness of an end-to-end QoS deployment.

    Finally, there is designing and testing the policies to be implemented. It’s important that the business leaders drive the categorization of applications as QoS works by providing preferential treatment of one type of data flow at the expense of others. After data flows have been loosely broken down into categories based on latency requirements and business importance, the next task is to place these applications into one of several classes. Here are some commonly used classes of data used in QoS:

    • Real-Time Data: This class includes time-sensitive applications that require low latency and consistent delivery.  Examples are voice and video conferencing and real-time streaming.
    • Interactive Data: This class includes applications that require low latency and prompt response but with less stringent requirements than real-time data.  Instant messaging and remote desktop applications fall into this category.
    • Bulk Data: This includes non-time-sensitive traffic that involves large file transfer or data backups like software updates and file downloads. This type of traffic is typically given low priority.
    • Best Effort: This consists of all remaining traffic that does not have specific QoS requirements like email or web browsing.

    Much of the complexity and management overhead involved in a QoS strategy has to do with maintaining each class and the policies to which they are attached. Therefore, the fewer classes you create, the easier the deployment and ongoing maintenance will be.

    Other techniques used with QoS include:

    • Traffic Prioritization: Assigning different priorities to different types of network traffic.
    • Traffic Shaping: Controlling the rate at which traffic flows through a network.
    • Traffic Policing: Enforcing traffic rules and limiting the amount of traffic that can pass through a network.
    • Packet Scheduling: Using algorithms to determine the order in which packets are transmitted from a queue.
    • Congestion Avoidance: Preventing network congestion before it occurs using a technique like Random Early Detection which monitors the length of network queues and selectively drops packets when the queue exceeds a particular threshold.
    • Resource Reservation: Allowing network devices to reserve bandwidth and allocate resources in advance.
    • Traffic Engineering: Managing network traffic with methods like route optimization, load balancing, and path selection.

    Once tested, the next step is implementing followed by managing. It is important to note that QoS is a not a one-time setup. It’s a continuous process that must be closely monitored to ensure it’s working as intended. An assessment should be done periodically to identify changes in application usage and data flows. This information can then be used for network upgrades or to re-categorize applications or QoS policies as business needs change.

    Concluding Thoughts 

    QoS is vital to optimizing network performance, prioritizing traffic, and providing an enhanced user experience, it is especially important in enterprises where different applications and services coexist and where network resources need to be allocated and managed efficiently.

    QoS is a continual process of monitoring and then adjusting policies and techniques to meet evolving business requirements.

    LiveAction’s LiveNX lets you view and control application performance through a graphical QoS management interface.  This intuitive interface lets you configure and manage QoS to ensure the performance of VoIP, video, and other application traffic to ensure a high-quality user experience and reduce overall network latency while helping to secure the network.

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    Related Glossary Terms

    SD-WAN, or software-defined wide area network, is a wide area network that uses software to control network operations across different geographies.

    Packet analysis is a primary traceback technique in network forensics, which, providing that the packet details captured are sufficiently detailed, can play back even the entire network traffic for a particular point in time.