What is quality of service?Quality of service (QoS) refers to any technology that manages data traffic to reduce packet loss, latency and jitter on a network. QoS controls and manages network resources by setting priorities for specific types of data on the network. Show
Enterprise networks need to provide predictable and measurable services as applications -- such as voice, video and delay-sensitive data -- to traverse a network. Organizations use QoS to meet the traffic requirements of sensitive applications, such as real-time voice and video, and to prevent the degradation of quality caused by packet loss, delay and jitter. Organizations can reach a QoS by using certain tools and techniques, such as jitter buffer and traffic shaping. For many organizations, QoS is included in the service-level agreement (SLA) with their network service provider to guarantee a certain level of network performance. The term Class of Service (CoS) is sometimes used interchangeably with QoS. However, they are slightly different. CoS technology does not specifically guarantee a level of service in terms of bandwidth, and it approaches traffic control from a less granular perspective. In many cases though, whether someone refers to CoS or QoS, they are likely talking about the same thing. QoS parametersOrganizations can measure QoS quantitatively by using several parameters, including the following:
Why is QoS important?Without QoS, network data can become disorganized, 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. Quality of service determines Quality of Experience (QoE). If the services an organization provides are not reliable, customer and employee relationships may be put at risk. Additionally, data integrity and security are more likely to be compromised in a company with a poor QoS. In general, employees and customers depend on communication services to do their jobs. When quality of service suffers, quality of work and Quality of Experience suffer as well. How does QoS work?When organizations use their networks to send information back and forth between endpoints on the network, the information or data is formatted into packets. Packets are the way computers organize information to be transferred over a network, like how a person might package items to be sent through the physical mail system. Quality of service tools take on the responsibility of prioritizing packets to get the most out of the finite amount of bandwidth on their network. In other words, the network can only transport so much information in a certain amount of time. So, QoS tools prioritize packets in a way that ensures that bandwidth is used to provide the best internet service possible in that fixed amount of time. For example, packets pertaining to a video call would be prioritized over packets pertaining to an email download. This is because a video call is a more synchronous form of communication than an email -- video needs to happen in real time, whereas emailing is not necessarily time-sensitive. If a packet is dropped or delayed during a video chat, the end user may experience jitter or latency in the chat. If packets are dropped or delayed in the emailing process, they can still be sent after and the end-user will not experience any lapse in service. They will only receive the email when all packets have been assembled, whereas someone streaming video sees the packets as they arrive. A QoS tool looks at packet headers to prioritize packets. Packet headers are bits of information that tell the tool and other network components what the packet contains, where it is going (the IP address of its destination) and what it will be used for. The QoS tool can also read the packet header and determine that a packet is related to video streaming and prioritize it over packets that are less time-sensitive. A packet header can be thought of as the mailing and return addresses on a physical package. The QoS tool can alter a portion of the packet header to specify priority. What are the benefits of QoS?The main benefit of QoS is that it ensures the availability of an organization's network and the applications that run on that network. It provides the safe, efficient transfer of data over that network. QoS also allows organizations to use their existing bandwidth more efficiently, instead of upgrading network infrastructure to expand bandwidth. More specific benefits include:
Implementing QoSWhen implementing QoS tools and strategies, organizations should follow these steps:
Three models exist to implement QoS: Best Effort, Integrated Services and Differentiated Services.
Implementing IntServ requires IntServ-capable routers and uses the Resource Reservation Protocol (RSVP) for network resource reservation. IntServ has limited scalability and high consumption of network resources.
For example, voice traffic can be assigned a higher priority than other types of traffic. Packets are assigned priorities using Differentiated Services Code Point (DSCP) for classification. DiffServ also uses per-hop behavior to apply QoS techniques, such as queuing and prioritization, to packets. Network architecture also affects how an organization implements QoS. A Multiprotocol Label Switching (MPLS) network includes a private link that offers end-to-end QoS along a single path. SLAs for MPLS specify bandwidth, QoS, latency and uptime. However, an MPLS can be expensive for organizations. Software-defined WAN (SD-WAN) uses multiple connectivity types, including MPLS and broadband. SD-WAN monitors the state of current network connections for performance issues and uses its multiple connectivity types to fail over based on state. For example, if packet loss exceeds a certain level on one connection, SD-WAN capabilities will look for an alternative connection.
QoS mechanismsCertain QoS mechanisms can manage data traffic quality and maintain the QoS requirements specified in SLAs. QoS mechanisms fall under specific categories depending on the roles they play in managing the network.
QoS toolsQoS tools generally fall into these categories:
QoS tools may perform just one or a combination of these functions. Many QoS tools are managed and perform these functions automatically, giving administrators access to alter settings and policies as needed. Some popular QoS monitoring tools are:
This was last updated in September 2021 Continue Reading About quality of service (QoS)
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