📸Why Frame Relay's QoS Outshines MPLS | A Walk Down Memory Lane🖼️
Exploring Why Frame Relay's QoS Was Superior to MPLS in Networking History
In the ever-evolving landscape of networking, the debate over Quality of Service (QoS) is perennial. Frame Relay, a once-dominant WAN technology, has faded into the annals of history, replaced by MPLS and more recently by SD-WAN. Yet, it’s worth revisiting the QoS of Frame Relay, which was in many ways superior to that of MPLS. Here's why Frame Relay’s QoS deserves a nostalgic nod.
1. Built-In Simplicity | Frame Relay's QoS Approach
Frame Relay offered QoS in a straightforward and deterministic manner. It used concepts like Committed Information Rate (CIR) and Excess Information Rate (EIR), ensuring predictable performance. CIR guaranteed a minimum bandwidth, while EIR allowed for bursts of data when capacity was available. These mechanisms were simple to configure, easy to understand, and highly effective in ensuring application performance.
MPLS, by contrast, introduced a more complex system based on Class of Service (CoS) labels. While theoretically more flexible, MPLS QoS often required intricate policy configurations and relied heavily on the underlying IP network's behavior. This complexity could lead to inconsistencies, especially in multi-vendor environments.
2. Hard Guarantees vs. Best-Effort Flexibility
Frame Relay networks provided hard guarantees on bandwidth through CIR. If an application required 2 Mbps, you could reserve it, and the network would deliver. Excess traffic was either dropped or marked as discard-eligible, keeping the core network stable. This predictability made it ideal for latency-sensitive applications like voice and video.
MPLS, while offering QoS, typically operates on a best-effort model for traffic outside its priority classes. In practice, this means that during congestion, lower-priority traffic can suffer significantly. While MPLS supports traffic engineering via RSVP-TE or Segment Routing, these add layers of complexity and are not universally deployed.
3. Consistency Across the Network
Frame Relay was a layer 2 technology with end-to-end QoS mechanisms baked into its architecture. Every node in a Frame Relay network adhered to the same QoS rules, ensuring consistency.
MPLS, however, is a hybrid Layer 2/Layer 3 technology. Its QoS relies on proper configuration of each node in the path, making it prone to misconfigurations or vendor-specific nuances. Furthermore, in MPLS networks, QoS often depends on the service provider’s backbone configuration, leaving enterprise customers with limited control over performance.
4. Robust Congestion Management
Frame Relay had a simple yet effective way of managing congestion. When the network became congested, it flagged traffic as Forward Explicit Congestion Notification (FECN) or Backward Explicit Congestion Notification (BECN). These signals allowed endpoints to adjust their sending rates, avoiding further congestion.
MPLS lacks a comparable native congestion signaling mechanism. Instead, it relies on Differentiated Services Code Point (DSCP) markings and mechanisms like Weighted Random Early Detection (WRED), which can vary in effectiveness and implementation across vendors.
5. Operational Visibility & Simplicity
In Frame Relay, QoS metrics were transparent and easy to monitor. Metrics like CIR usage and discard eligibility were directly visible, enabling straightforward troubleshooting.
MPLS, while powerful, requires complex tools for monitoring and troubleshooting QoS. Vendors offer varying degrees of visibility, and achieving end-to-end monitoring often involves expensive software suites and expertise.
6. MPLS Overlays Lack QoS Transparency
MPLS is often used as an overlay to an IP backbone. While this provides scalability, it also hides much of the underlying network’s QoS mechanisms from the end user. Frame Relay’s direct circuits, on the other hand, provided clear visibility into performance guarantees and traffic behavior.
Wrap | QoS Lessons from the Past
Frame Relay’s QoS was simpler, more deterministic, and ultimately more reliable for many use cases than MPLS. While MPLS brought significant advancements in scalability and flexibility, its QoS mechanisms often felt like an afterthought, relying on IP-layer workarounds and vendor-specific implementations.
Today, with the rise of SD-WAN, the networking world is returning to some of Frame Relay’s core principles: simple, predictable QoS with clear guarantees. While we celebrate the innovations of MPLS and SD-WAN, it’s worth remembering that sometimes, the old ways—like Frame Relay’s QoS—were not just good but great.