Hi all, I'm confused by the idea of setting RTO=4*RTT in TFRC. >From RFC 3448: -- We further simplify this by setting t_RTO = 4*R. A more accurate calculation of t_RTO is possible, but experiments with the current setting have resulted in reasonable fairness with existing TCP implementations [9]. -- (where [9] is Joerg Widmer's master thesis). I'd like to understand where the number 4 comes from. Was that just a magic number that worked well in Joerg's tests? If we apply the same intuition (whatever it was) that led to the choice of RTT/2 as an initial value for RTTVAR in RFC 2988 and forget about the EWMA processes for a minute, it would seem reasonable to set RTO to RTT + 4 * RTT/2 = 3*RTT instead... Also, I wonder how people apply the equation in other settings - is it a common thing to set RTO to 4*RTT when using it, or is this specific to TFRC? Cheers, Michael -- PS: maybe off-topic because it's related to RMT and not DCCP, but it's still somewhat related and maybe you could also answer that one in the same message: I noticed that, in RFC 4654, the following changes were made to the equation: 1) s became 8 s 2) b became 1 3) RTO became 4 (not 4 RTT!) I can understand 1) above, as this means that a non-DelACK receiver is assumed. I can also understand 2), because you need the throughput per 8 seconds (not 1 second) for the protocol - but I can't understand the reasoning behind replacing RTO with 4. I must be missing something, but this is really confusing me - I would greatly appreciate an explanation. Thanks!!
