Assume a computer has a precise clock which is not initialized. That is, the time on the computer's clock is the real time plus some constant offset. The computer has a network connection and we want to use that connection to determine the constant offset $B$.The simple method is that the computer sends a query to a time server, noting the local time $B + C_1$. The time server receives the query at a time $T$ and sends a reply containing $T$ back to the client, which receives it at a time $B + C_2$. Then $B + C_1 \le T \le B + C_2$, i.e. $T - C_2 \le B \le T - C_1$.If the network transmission time and the server processing time are symmetric, then $B = T - \dfrac{C_1 + C_2}{2}$. As far as I know, NTP, the time synchronization protocol used in the wild, operates on this assumption.How can the precision be improved if the delays are not symmetric? Is there a way to measure this asymmetry in a typical Internet infrastructure?
Clock synchronization in a network with asymmetric delays
clocks;distributed systems;computer networks