Understanding Delay Skew in Ethernet Cables

In high-performance Ethernet networks, timing is everything. One often-overlooked factor that can affect performance and reliability is delay skew—a crucial metric in structured cabling design and testing.

What is Delay Skew?

Delay skew is the difference in signal propagation time between the twisted pairs within an Ethernet cable. It can result from differences in pair length, twist rate, or impedance, and can affect the timing of data delivery across multiple pairs.

Why Does Delay Skew Matter?

Delay skew directly affects timing synchronization in networks. Excessive delay skew can lead to timing errors, data corruption, or signal integrity issues, impacting network reliability and performance. Delay skew is an important consideration in Ethernet networks, particularly in applications where precise timing synchronization is crucial, such as high-speed data transmission or PoE (Power over Ethernet) applications.

Acceptable Delay Skew Values

For a standard 100-meter Ethernet cable:

• Excellent: < 25 ns
• Good: < 45 ns
• Marginally Acceptable: 45–50 ns
• Unacceptable: > 50 ns

Choosing high-quality Ethernet cables with certified delay skew performance is essential for ensuring stable, high-speed network operations.

When selecting Ethernet cables for specific applications, it’s essential to consider the delay skew specifications provided by the manufacturer to ensure compatibility with the requirements of the network and to maintain reliable communication between devices.