In Cisco ACI, Forward
Error Correction (FEC) is a mechanism used to improve the reliability
of high-speed data transmission across physical links, especially in
environments using 25G, 40G, 100G, or 400G interfaces.
🔍 What Is Forward Error Correction?
FEC is a technique
where the sender adds redundant data (parity bits) to each
transmission. If some bits are corrupted during transit, the receiver can detect
and correct those errors without needing a retransmission. Think of it
like sending a puzzle with extra pieces so the receiver can still complete it
even if a few pieces go missing.
🧠 How FEC Works in Cisco ACI
In ACI, FEC is
negotiated between switches and endpoints during auto-negotiation.
The devices advertise their supported FEC modes and agree on the best one.
Common FEC modes include:
- FC-FEC (Firecode FEC): Used for 25G links.
- RS-FEC (Reed-Solomon FEC): Used for 25G, 100G, and 400G links.
- CL91-RS-FEC and IEEE-RS-FEC:
Advanced versions for higher speeds. - AUTO-FEC: Automatically selects the best FEC mode based on link
capabilities.
⚙️ Why It Matters
FEC is especially
important in Cisco ACI because:
- High-speed links (like 25G or 100G) are more prone to
bit errors. - Breakout ports (e.g., 4x25G from a 100G port) often
require FEC to maintain link stability. - Copper DAC cables used in short-distance connections
rely on FEC to compensate for signal degradation.
✅ Use Cases
- Ensuring error-free transmission over
high-speed links. - Supporting auto-negotiation on
breakout ports. - Enhancing link reliability without
increasing latency or requiring retransmissions.