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>>How to know that you have healthy TCP sessions ?

How to know that you have healthy TCP sessions ?

By | 2018-04-11T15:54:15+00:00 December 18th, 2017|Categories: Network performance|

Learn the 5 criteria that determine whether you have healthy TCP sessions

As a rule of thumb, healthy TCP sessions are identified and referenced by the following 5 Key Performance Indicators (KPIs) and their thresholds:

  • # SYN’s – refers to session starts; these should be twice the number of sessions. This is because of the 3-way handshake SYN | SYN-ACK | ACK (ACK equals Acknowledgment indicating “no errors – please continue”).healthy tcp sessions with ACKs
  • # FIN’s – refers to session endings; these should roughly be twice the number of sessions. This is because with healthy TCP sessi0ns, each session ends with a FIN-ACK initiated and confirmed by both the client and the server side. Since some applications are working with long-lasting sessions, from time-to-time, the amount of FIN’s might actually be lower than twice the number of sessions.healthy tcp sessions with FINs
  • # RST’s – refers to session restarts; these should be close to zero, indicating a low number of session resets. Depending on the TCP stack, it could also be an indicator of the number of session endings; similar to using a FIN-ACK. In particular, Microsoft applications running over SSL are well-known for this (mis-)behavior.
  • # DupAck’s – refers to packets that are delayed or dropped; these should be close to zero indicating a low number of delayed/lost packets.
  • # 0-Win’s – refers to a high system utilization; the value is expected to be close to zero indicating that the hosts involved are in good shape for processing incoming packets.
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About the Author:

Will Moonen
Will is an experienced, result driven consultant with a proven track record in improving the performance of IT processes, applications and infrastructures while keeping an open mind for human aspects. (LinkedIn profile)