I wish I had longer to write this article, but I've got to leave in 10 minutes, so here's what I can do in the time alloted.
Ping time is a very coarse measurement of link latency and does NOT give you an absolute number worth anything because it doesn't distinguish between server latency and link latency and for pings, server latency is not consistent from one machine/device to another. Ping time is mostly useful when you have a previous measurement to compare to from the same machine as a relative indicator of link speed and even then, it is still a coarse measurement. For many/most devices, responding to a ping is a very low priority task.
A better measure is to look at the latency for a file service request. Just about any PC or Mac made in the last 5 years will turn around a file read request in much less than a millisecond (1/1000 second), so the latency you measure is the latency of the link. Downside, you need to do this with a protocol analyzer.
A router will often have a ping turnaround time of 20 milliseconds or greater and this number is variable depending on load, so ping time can be a (very coarse) measurement of router load and then only when you have a reference when the router was not loaded.
The latency of Ethernet itself is 9.6 microseconds (one millionth second) for 10 MB, 0.96 microseconds for 100 MB, although that's a theoretical limit -- it's the time that an Ethernet sender has to observe no signal before sending, but this only applies to half duplex. There's no wait time in full duplex. The actual limit is how fast can you get it through the system, across the bus and out the NIC. In most cases, this is less than a millisecond.
Token ring has many drawbacks in typical modern network situations. It was designed with a strong and predictable client-server relationship in mind where you would attach to and use a limited number of servers for long periods of time. Its actual link latency is comparable to Ethernet - so minute as to be insignificant.
Gotta go,
Kurt VanderSluis
PS, I just dashed this off, so if there's a typo, sorry, but I didn't have time to do the fine tooth comb thing
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I wish I had longer to write this article, but I've got to leave in 10 minutes, so here's what I can do in the time alloted. Ping time is a very coarse measurement of link latency and does NOT give you an absolute number worth anything because it doesn't distinguish between server latency and link latency and for pings, server latency is not consistent from one machine/device to another. Ping time is mostly useful when you have a previous measurement to compare to from the same machine as a relative indicator of link speed and even then, it is still a coarse measurement. For many/most devices, responding to a ping is a very low priority task. A better measure is to look at the latency for a file service request. Just about any PC or Mac made in the last 5 years will turn around a file read request in much less than a millisecond (1/1000 second), so the latency you measure is the latency of the link. Downside, you need to do this with a protocol analyzer. A router will often have a ping turnaround time of 20 milliseconds or greater and this number is variable depending on load, so ping time can be a (very coarse) measurement of router load and then only when you have a reference when the router was not loaded. The latency of Ethernet itself is 9.6 microseconds (one millionth second) for 10 MB, 0.96 microseconds for 100 MB, although that's a theoretical limit -- it's the time that an Ethernet sender has to observe no signal before sending, but this only applies to half duplex. There's no wait time in full duplex. The actual limit is how fast can you get it through the system, across the bus and out the NIC. In most cases, this is less than a millisecond. Token ring has many drawbacks in typical modern network situations. It was designed with a strong and predictable client-server relationship in mind where you would attach to and use a limited number of servers for long periods of time. Its actual link latency is comparable to Ethernet - so minute as to be insignificant. Gotta go, Kurt VanderSluis PS, I just dashed this off, so if there's a typo, sorry, but I didn't have time to do the fine tooth comb thing