Fix ping timeout and interval #4

Merged

lx merged 8 commits from fix-ping into main

2022-09-02 12:22:57 +00:00

lx commented

2022-08-31 14:49:31 +00:00

Owner

We had issues before where ping timeouts were causing disconnections between nodes too easily. This was due to the combination of two problems:

a too low ping timeout (5 seconds)
a bug where several pings were sent in rapid succession, instead of waiting for PING_INTERVAL time to be elapsed, when the ping wasn't returned before the loop interval (1s) of the main loop

This PR upgrades the ping timeout to 10 seconds, makes sure that no ping is re-sent before 15 seconds after the previous one, and sets the number of consecutive failures before disconnection to 4 instead of 3. In an mknet simulation with very limited bandwidth, this allowed for more concurrent traffic before timeouts caused a disconnection. Disconnections still happenned in the simulation, because kernel packet buffers allowed for traffic to have up to 24 seconds RTT, which still triggers the 10 seconds ping timeout repetitively.

Question: in a real-world network, taking into account the rate at which TCP throttles sends on a slow connection, what is the expected maximum RTT on a saturated link? This should guide us to set the correct ping timeout in the definitive version.

We had issues before where ping timeouts were causing disconnections between nodes too easily. This was due to the combination of two problems: - a too low ping timeout (5 seconds) - a bug where several pings were sent in rapid succession, instead of waiting for PING_INTERVAL time to be elapsed, when the ping wasn't returned before the loop interval (1s) of the main loop This PR upgrades the ping timeout to 10 seconds, makes sure that no ping is re-sent before 15 seconds after the previous one, and sets the number of consecutive failures before disconnection to 4 instead of 3. In an mknet simulation with very limited bandwidth, this allowed for more concurrent traffic before timeouts caused a disconnection. Disconnections still happenned in the simulation, because kernel packet buffers allowed for traffic to have up to 24 seconds RTT, which still triggers the 10 seconds ping timeout repetitively. **Question:** in a real-world network, taking into account the rate at which TCP throttles sends on a slow connection, what is the expected maximum RTT on a saturated link? This should guide us to set the correct ping timeout in the definitive version.

lx added 5 commits 2022-08-31 14:49:31 +00:00