CODEWITHSUNDEEP
network-programming
Sajal Ali
Sajal Ali

Reputation: 437

why 4 in TCP timeout formula

In the formula for TCP timeout calculation we multiply 4 with Deviation, my question is that why we multiply 4 and not any other number with the deviation? please tell.

FORMULA

Timeout_Interval = Estimated_RTT + 4*(Deviation_RTT)

Upvotes: 3

Views: 1366

Answers (1)

Brian White
Brian White

Reputation: 8746

If you think of standard deviations, then +1σ will cover about 84.1%, +2σ will cover about 97.7%, +3σ will cover about 99.8%, and +4σ will cover about 99.9%.

The "Deviation_RTT" is much the same and thus this equation will avoid retransmission for the vast majority of packets that are sent. You can make it larger to have slightly fewer retransmissions but also be slower to pull the trigger when a packet does get lost.

Upvotes: 2

Related Questions