Quality of Services (QoS) vs. Quality of Experience (QoE)

As SD-WAN continues to take share from MPLS, networkers should understand the difference between Quality of Service (QoS) and Quality of Experience (QoS).

five stars quality
Rob Rodier

Dec 30, 2021


For anything to move forward in the enterprise telecom world, service providers and enterprises need to reach agreement on what defines “quality” connectivity - and the contractual terms used to define your circuit quality will vary based on the type of service you are procuring. 

Today we’ll cover Quality of Service (QoS) and Quality of Experience (QoE); two standards for quality that sound similar but are quite different and apply to MPLS and SD-WAN, respectively.

Quick Review: MPLS vs SD-WAN

In 2021, SD-WAN continued to take market share from the incumbent standard for multi-site WANs, Multiprotocol Label Switching (MPLS). The key differences between MPLS and SD-WAN is that an MPLS network connects over a completely private, dedicated network while an SD-WAN, in most cases, intelligently steers traffic over the public internet.

If you need a refresher on these services, check out our guide on MPLS vs SD-WAN before reading further. 

Due to this key difference in network structure (private vs public connectivity), both of these services offer their own unique standard for quality. The Quality of Service (QoS) agreement has long been the “quality standard” in multi-site wide area networks connected by MPLS, while a new term has entered the mix to define quality standards for SD-WAN connections: Quality of Experience (QoE)

Now let’s discuss what QoS and QoE actually mean for your telecom contract and network users. 

Quality of Service (QoS) 

Service Level Agreements (SLAs), which have been around since the 1980s, set minimum thresholds for Quality of Service performance and guarantee that QoS will not fall below these limits. MPLS QoS standards are defined in terms of bandwidth, latency, jitter, and packet loss. This means that when your network is backed by a QoS agreement, you are guaranteed your bandwidth at all times, high network speed (aka low latency), and a high quality connection (aka minimal/no jitter or packet loss).    

QoS is a contractual feature in MPLS networks and other dedicated WAN services that do not utilize the public Internet as part of their network. This is because, given your provider is utilizing their own private core network and not the public internet, they are able to guarantee high standards for your network, whereas networks over the public internet are at the mercy of other traffic delaying your traffic or reducing your connection quality. 

QoS isn’t just a point of reference for a collection of customer-facing performance metrics. It also puts a name to the notion of how service providers actively manage quality by shaping and prioritizing network traffic as a whole. They achieve this by using MPLS to intelligently group and prioritize similar types of traffic to be transmitted before other traffic on the private network. 

It’s important to note that, while an MPLS circuit is backed by SLA and QoS standards, you are responsible for actually tracking if the telecom provider is meeting these standards. If they aren’t you can seek remedies (usually in the form of service credits) for the reduced quality. 

Quality of Experience

Recent years have witnessed the rise of another concept - Quality of Experience (QoE). 

Created in the era of increasing Internet-based video and mobile applications, QoE, at its core, refers to the rules set by the network administrator to prioritize and selectively route ingress and egress traffic during times of network congestion. QoE is put into place to increase the probability that ALL users on the network can access applications and services on the network in a productive way.

The birth of “QoE” arose in part out of the reality that using the public Internet in your network (as is the case with SD-WANs) not only as a transport for private WAN traffic but also as a primary network node in SaaS and applications residing in public clouds, will inevitably lead to unpredictable and unstable levels of performance.

SD-WAN combats the instability of the public Internet in its network by creating policies at the network edge as well as virtual private tunnels through the public Internet and other networks that make Internet-based traffic transmission more deterministic and more consistent. 

Some SD-WAN vendors have gone a step further by creating their own “middle mile networks”. When utilizing their own middle mile network, SD-WAN providers have full control over routing and traffic prioritization between all nodes on a WAN and are also able to “drain” traffic destined for the public internet from their private network very close in proximity to its final destination. For example, an SD-WAN provider could take requests from Miami that are destined for AWS-WEST-1 in Northern CA and route it across their network backbone (avoiding the Internet’s dynamic routing) and drain it back to the Internet in San Francisco, which is geographically close to West-1. Some SD-WAN providers even go a step further by peering directly with AWS or offering a private express route right into the AWS network. 

Other real world examples of QoE are throttling users or applications that are consuming too many resources on the network; YouTube and Netflix are easy examples, but there could also be replication or data backups happening during peak hours, or heavy file sharing happening across the WAN, that chews up lots of resources/bandwidth. VoIP calls can be benchmarked with MOS scoring and the SD-WAN appliance can steer traffic from one circuit to another if it thinks that it will increase the quality of the call. 

Quality of Service vs Quality of Experience

If your enterprise is currently utilizing an ultra-reliable MPLS network, the thought of moving to an SD-WAN that exposes you to the public Internet might seem like a risky decision. Thankfully, SD-WAN providers have figured out all of the “tricks” to ensure a great Quality of Experience for their customers, which essentially accomplishes the same thing as QoS - they are simply achieving it in a different way that is a little less exact/predictable. 

That said, anytime you’re making a network decision, it’s important to understand not only the technological ramifications of that decision but also the new contractual terms that will come with it (and their impact). 

If you’re considering making the switch to SD-WAN but don’t want to waste time speccing out the technical and legal ramifications - reach out to us! The telco experts at Lightyear are eager to help answer your networking questions. You can get started with our 2-minute, online questionnaire or you can schedule a call with us here.   

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