What Is Cable-Length Skew?_
In high-speed fabrics the electrical or optical delay increases with conductor or fiber length, so a longer cable introduces a measurable time offset relative to a shorter one. This offset appears as inter-lane or inter-link skew at the receiver and must stay inside the tolerance budgeted by the SerDes and protocol logic. Fabric designers therefore either match cable lengths within a group or rely on the endpoint's built-in deskew buffers to absorb the difference.
Technical Details
Skew is cumulative across the entire cable assembly, including patch cords and trunk cables. Copper twinax and single-mode or multi-mode fiber each exhibit their own propagation velocity, so mixing media types between otherwise equal lengths also creates skew. In practice, installers group cables by measured or labeled length bins rather than attempting field trimming. The receiving PHY reports skew status through its diagnostic registers; persistent out-of-range readings usually indicate a length mismatch rather than a faulty connector.
How Leviathan Systems Works with Cable-Length Skew
During rack-scale fabric bring-up the crew verifies that all InfiniBand or Ethernet links between a given pair of spine and leaf switches use cables from the same length bin so that deskew margins remain consistent across the plane. When a link fails deskew during commissioning, the first check is whether a replacement cable of different length was inadvertently installed.
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