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What are the ONTAP KTLS handshake limits

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Applies to

  • ONTAP 9.13.1 and higher
  • KTLS

Answer

  • For ONTAP 9.13.1 and higher, KTLS handshake limits are based on the number of CPU cores. 
  • ONTAP 9.17.1 added a second, or deferral and pending request queue effectively doubling the size of the handshake limits for applications. 
Number of CPU Cores 9.13.1 9.16.1 9.17.1
Concurrent Handshake Limit Concurrent Handshake Limit Concurrent Handshake Limit Deferral Queue Total Effective Limit
1-2  50

50

 50 50 100
3-6  90 90 90 90 180
7-14  130 130 130 130 260
15-30 170 170 170 170 340
31-62 210 210 210 210 420
63-126 250 250 250 250 500
127-254 Not supported 290 290 290 580

Additional Information

  • Starting in ONTAP 9.16.x, a new new handshake deferral feature where, at the moment, the limit at which ONTAP will start to abort handshakes is effectively increased by a factor 4. 
    • Specifically, the handshake deferral queue size defaults to 3 times the concurrent handshake limit. 
    • 9.16.x also has the much faster handshake control plane which will support more concurrent handshakes across the board. 
  • KB: ONTAP reached the maximum limit of 290 concurrent TLS connection handshakes
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