Lei wrote: > In RFC 2030(written by Prof. D.Mills), we have roundtrip delay time > formula as follows: > > d = (T4 - T1) - (T2 - T3) .................(1) > > However, IMHO, it should be > > d = (T4-T1) - (T3 - T2)....................(1)'
This is the same as d = -T1 + T2 -T3 +T4 or d = (T2-T1) - (T3-T4) right? "Use the source, Luke" :-) From ntp_proto.c, around line 1200: > * Let t1 = p_org, t2 = p_rec, t3 = p_xmt, t4 = peer->rec: > */ > ci = p_xmt; /* t3 - t4 */ > L_SUB(&ci, &peer->rec); > LFPTOD(&ci, t34); > ci = p_rec; /* t2 - t1 */ > L_SUB(&ci, &p_org); > LFPTOD(&ci, t21); I.e Dr. Mills have here calculated (T3-T4) and (T2-T1), both of which should be small (normally positive) numbers, and the difference between them is the same as in your formula. The conclusion is that I'm almost certain you've found a typo in the RFC: The total on-network-cable time must of course be the total time from request to reply (T4-T1), minus the time spent inside the server (T3-T2), so your second version is correct. Assuming the RFC does indeed use the first form, that would also be against the written description of the algorithm. Terje -- - <Terje.Mathisen at tmsw.no> "almost all programming can be viewed as an exercise in caching" _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
