Hashing Linearity Enables Relative Path Control in Data Centers
summary
Reveals that ECMP hashing in real switch ASICs uses hashing linearity (XOR/CRC) so flipping header bits gives deterministic path offsets, and implements RePaC to map those offsets using only 112 basis headers instead of 2^112 entries. Hosts change packet headers to migrate flows with predictable next-hop changes, achieving sub-second failover (milliseconds with fine RTO), orders-of-magnitude faster recovery than LACP, and up to 3× link utilization gain in production-config test pods without changing routing or switches.
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chapters (13)
- 0:00Intro
- 0:35Requirements for Data Centers
- 0:59Rich path diversity in data centers
- 2:15Problems in leveraging path diversity
- 4:33Existing approaches
- 6:03RePac: Relative Path Control
- 6:31Conventional perception of ECMP
- 6:48Hashing linearity of ECMP
- 8:32Model linearity with pathmap
- 9:36Path control with pathmap
- 10:23Showcase: fault tolerance
- 11:18Evaluation
- 12:36Takeaways
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