How to Calculate One-way Packet Delay without using NTP, PTP

Question

Hi All,

I am looking for the way to calculate the one-way delay in a packet-switched network. I do not want to use NTP or PTP (Network Time Protocol, Precision Time Protocol).

Consider the scenario:

Host-1 Sends the packet to Host-2. Both Hosts have different Clock rates and the hosts are located in different countries.

Packet may be UDP/TCP/Layer 2 Frame.

Is there any way to sync the clock rates of two hosts so as to calculate the one-way delay.

Now how do you guys calculate the one way delay without relying on a timing protocol. I am looking some generic formula to do this.

I would much appreciate the answers for this question.

Thanks a ton in advance.

Answer 1

Synchronizing clocks is exactly what [S]NTP are meant to accomplish. If there was a simpler way, the protocols would be simpler. You can approximate RTT without them, but one-way delay is hard to do.

Answer 2

I use iperf to do network testing like that. You might get some insight by looking at how they do it.

Answer 3

No, you cannot. Measuring a one-way delay requires synchronized clocks (and NTP is typically not good enough for this task, independent synch to reliable clocks is necessary).

Read RFC 4656 for the gory details. There are two available implementations, OWAMP in C and Jowamp in Java.