What is the Quality of Service (QoS)?

The use of mechanisms or technologies on a network to control traffic and ensure the performance of critical applications with limited network capacity is known as quality of service (QoS). It enables organizations to prioritize specific high-performance applications while adjusting overall network traffic.

 

QoS is commonly used in networks that transport traffic for resource-intensive systems. It is commonly required for services such as internet protocol television (IPTV), online gaming, streaming media, videoconferencing, video on demand (VOD), and Voice over IP (VoIP).

 

What is the Quality of Service?

 

Quality of Service (QoS) is a collection of network technologies that ensure a network's ability to reliably run high-priority applications and traffic despite limited network capacity. QoS technologies achieve this by offering differentiated handling and capacity allocation to specific networks traffic flows. This allows the network administrator to specify the order in which packets are processed as well as the amount of bandwidth available to that application or traffic flow.

 

QoS measurements include bandwidth (throughput), latency (delay), jitter (latency variation), and error rate. This makes QoS especially important for high-bandwidth, real-time traffic like voice over IP (VoIP), video conferencing, and video-on-demand, which are sensitive to latency and jitter. These applications are referred to as "inelastic," because they have low bandwidth requirements and high latency limits.

 

Queuing and bandwidth management are QoS mechanisms for ordering packets and allocating bandwidth. However, before they can be implemented, traffic must be classified using classification tools. Organizations can ensure the consistency and adequate availability of resources for their most critical applications by categorizing traffic according to policy.

 

Traffic can be classified crudely by port or IP, or more sophisticatedly by application or user. The latter parameters enable more meaningful data identification and, as a result, classification. Following that, rules are assigned to queuing and bandwidth management tools to handle traffic flows based on the classification they received upon entering the network.

 

The queuing mechanism stores packets within traffic flow until the network is ready to process them. Priority Queuing (PQ) was created to ensure the availability and minimal latency of network performance for the most important batches of applications and traffic by assigning them a priority and specific bandwidth based on their classification. This ensures that the most important network activities are not deprived of bandwidth by lower priority activities. Applications, users, and traffic can be queued in up to eight distinct queues.

 

Bandwidth management mechanisms monitor and control network traffic flows to avoid exceeding network capacity and resulting in network congestion. Traffic shaping, a rate-limiting technique used to optimize or guarantee performance and increase usable bandwidth where necessary, and scheduling algorithms, which offer various methods for providing bandwidth to specific traffic flows, are examples of bandwidth management mechanisms.

 

Also Read | What is Network Management 

 

Concepts of Quality of Service:

 

The concepts of QoS are explained further below.

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Concepts of Quality Of Service 

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1. Congestion Management:

 

The bursty nature of data traffic can sometimes cause traffic to exceed connection speed. QoS allows a router to place packets in various queues. Service-specific queues frequently rely on priority rather than buffering traffic in a single queue and allowing the first packet out.

 

2. Management of Queues:

 

A buffer's queues can fill up and overflow. If a queue is full, a packet is dropped, and the router cannot prevent it from being dropped if it is a high-priority packet. This is known as tail drop.

 

3. Link Effectiveness:

 

Low-speed links act as bottlenecks for smaller packets. Because of the serialization delay caused by the high packets, the lower packets must wait longer. The serialization delay is the amount of time it takes to send a packet over a connection.

 

4. Traffic management and policing:

 

Shaping can prevent buffer overflow by limiting the full bandwidth potential of application packets. Many network topologies with a high-bandwidth link connecting to a low-bandwidth link in remote sites can occasionally overflow low bandwidth connections.

 

As a result, shaping is used to bring traffic from the high bandwidth link closer to the low bandwidth link in order to avoid overflow on the low bandwidth link. Traffic that exceeds the configured rate can be discarded by police, but it is buffered in the case of shaping.

 

Why is Quality of Service Important? 

 

Traditional business networks functioned as distinct entities. One network handled phone calls and teleconferences, while another handled laptops, desktops, servers, and other devices. They rarely met, unless a computer used a phone line to connect to the internet.

 

When networks only carried data, speed was not an issue. However, interactive applications containing audio and video content must now be delivered at high speeds, with no packet loss or variation in delivery speed.

 

QoS is especially important for ensuring the high performance of critical applications that require large amounts of bandwidth for real-time traffic. For example, it enables businesses to prioritize the performance of "inelastic" applications, such as VoIP and videoconferencing., which frequently have low bandwidth requirements, high latency limits, and high sensitivity to jitter and latency.

 

QoS assists businesses in preventing the delay of these critical applications, ensuring that they perform to the level that users expect. For example, lost packets could cause a delay in the stream, resulting in choppy and indecipherable sound and video quality during a video conference call.

 

QoS is becoming increasingly important as network performance requirements evolve to meet the growing number of people who use them. The most recent online applications and services necessitate massive amounts of bandwidth and network performance, and users expect them to be available at all times. As a result, organizations must implement techniques and technologies that ensure the best possible service.

 

Quality of service (QoS) is also becoming more important as the Internet of Things (IoT) matures. In the manufacturing sector, for example, machines now use networks to provide real-time status updates on any potential issues. As a result, any delay in feedback could result in extremely costly errors in IoT networking. QoS allows the data stream to take precedence in the network and ensures that data flows as quickly as possible.

 

Cities are now teeming with smart sensors, which are essential for running large-scale IoT projects like smart buildings. Data collected and analyzed, such as humidity and temperature data, is frequently time-sensitive and must be appropriately identified, marked, and queued.

 

Characteristics and Benefits of Quality of Service :

 

Characteristics of Quality of Service: 

 

We must contend with four characteristics of network traffic:

 

1. Bandwidth- It is the link's speed in bits per second (bps). We can instruct the router on how to use this bandwidth using QoS. FIFO serves packets on a first-come, first-served basis. One of the things we can do with QoS creates different queues and place different types of traffic in different queues. We can then configure the router so that queue one receives 50% of the bandwidth, queue two receives 20% of the bandwidth, and queue three receives the remaining 30% of the bandwidth.

 

2. Delay - The time it takes for a packet to travel from its origin to its destination is known as the one-way delay. The amount of time it takes to travel from the source to the destination and back is called the round-trip delay. There are different types of delay; without going into too much detail, let us give you a quick overview:

 

• Processing Delay: the time it takes for a device to complete all of the tasks required to forward a packet. A router, for example, must perform a routing table lookup, as well as check its ARP table and outgoing access lists. The processing delay is affected by the router model, CPU, and switching method. 

 

• Queuing delay: The amount of time a packet spends waiting in a queue. When an interface is overloaded, the packet must wait in the queue before being transmitted.

 

• Serialization delay: The time it takes to send all bits of a frame to the physical interface for transmission is referred to as serialization delay.

 

• Propagation delay: The time it takes for bits to cross a physical medium is referred to as propagation delay. The time it takes for bits to travel through a 10-mile fiber optic link, for example, is much shorter than the time it takes for bits to travel through satellite links.

 

3. Jitter- It is a variation of a one-way delay in a packet stream. Assume an IP phone sends a constant stream of voice packets. Some packets are delayed due to network congestion. The delay between packets 1 and 2 is 20 milliseconds, the delay between packets 2 and 3 is 40 milliseconds, the delay between packets 3 and 4 is 5 milliseconds, and so on. The receiver of these voice packets must deal with jitter, ensuring that the packets have a consistent delay, or the voice quality will suffer.

 

4. Loss - The amount of lost data, usually expressed as a percentage of lost packets sent, is referred to as loss. If you send 100 packets and only 95 of them arrive at their destination, your packet loss is 5%. Packet loss is unavoidable. For example, when there is congestion, packets are queued; however, once the queue is full, packets are dropped. With QoS, we can at least control which packets are dropped when this occurs.

 

Benefits of Quality of Service:

 

QoS solutions offer several advantages. Among the most important are:

 

1. Improved Application Performance: The main advantage of QoS is that it can improve the performance of critical applications within an organization's IT infrastructure. QoS can help to ensure that packet loss, delay, and latency requirements are met by identifying and prioritizing critical applications based on network traffic. This ensures that sensitive applications are not degraded in performance or rendered unusable by overburdened networks.

 

2. Improved Network Utilization: Most organizations have invested heavily in their network infrastructure and may be using more expensive transport media. For resiliency and redundancy, an organization may have MPLS links installed or use mobile networks. Because QoS network traffic identification can prioritize traffic based on the associated application, application-specific policies can be developed to ensure that expensive and high-performance network bandwidth is used primarily or exclusively by the applications that require it.

 

3. Optimized Traffic Routing: Because traffic from different applications has different destinations, a "one-size-fits-all" approach to traffic routing can lead to inefficiencies and delays. An organization can more efficiently route network traffic to its destination by identifying the application associated with a specific network connection and applying application-specific policies to it.

 

4. Reduced Network Congestion: Low-priority traffic on an organization's network can quickly become congested. QoS can help to reduce network congestion by dropping or throttling low-priority traffic during peak utilization periods, as well as by using application-specific traffic routing to reduce congestion in critical network sectors.

 

In the end, what matters is not how good you believe your service is, but what your customers believe. It's easy to see how total customer satisfaction can lead to higher profits. Top-quality service is not an option for growing and prospering; it is a requirement.