nanog mailing list archives
Re: Is latency equivalent to RTT?
From: "Henk Uijterwaal (RIPE-NCC)" <henk () ripe net>
Date: Wed, 14 May 2003 17:17:55 +0200 (CEST)
On Wed, 14 May 2003 Michael.Dillon () radianz com wrote:
Has it become common usage to define latency in an IP network as the round trip time in that network? I've always considered latency to be a one-way measure of delay and RTT to be the sum of the latencies in both directions. When I tried to find something to back up this view, I discovered that a number of companies define latency as equivalent to RTT in their SLAs. Assuming that one has measuring devices in every PoP, do you think it is harder to measure a full matrix of one way latency compared to measuring a full matrix of RTT?
The problem is buying and installing the equipment, even if you buy an off the shelf product like RIPE NCC's TTM :-). Once installed, these products will just provide you with the numbers.
Does it even make sense to measure a full matrix of RTT when the measurement of A to B to A should be equivalent to the measurement of B to A to B?
If you are sure that the path taken for A-B-A is equal to B-A-B, then no, measuring only A-B-A is sufficient. Henk ------------------------------------------------------------------------------ Henk Uijterwaal Email: henk.uijterwaal () ripe net RIPE Network Coordination Centre WWW: http://www.ripe.net/home/henk P.O.Box 10096 Singel 258 Phone: +31.20.5354414 1001 EB Amsterdam 1016 AB Amsterdam Fax: +31.20.5354445 The Netherlands The Netherlands Mobile: +31.6.55861746 ------------------------------------------------------------------------------ That problem that we weren't having yesterday, is it better? (Big ISP NOC)
Current thread:
- Is latency equivalent to RTT? Michael . Dillon (May 14)
- Re: Is latency equivalent to RTT? Stephen J. Wilcox (May 14)
- Re: Is latency equivalent to RTT? Andrew Bangs (May 14)
- Re: Is latency equivalent to RTT? John Kristoff (May 14)
- Re: Is latency equivalent to RTT? Henk Uijterwaal (RIPE-NCC) (May 14)
- Re: Is latency equivalent to RTT? Barney Wolff (May 14)
- <Possible follow-ups>
- Re: Is latency equivalent to RTT? Michael . Dillon (May 14)
- NTp sources that work in a datacenter (was Re: Is latency equivalent to RTT?) Steve Francis (May 14)
- Re: NTp sources that work in a datacenter (was Re: Is latency equivalent to RTT?) Henk Uijterwaal (RIPE-NCC) (May 14)
- Re: NTp sources that work in a datacenter (was Re: Is latency equivalent to RTT?) Joel Jaeggli (May 14)
- Re: NTp sources that work in a datacenter (was Re: Is latency equivalent to RTT?) Sean Donelan (May 14)
- Re: NTp sources that work in a datacenter (was Re: Is latency equivalent to RTT?) just me (May 14)
- NTp sources that work in a datacenter (was Re: Is latency equivalent to RTT?) Steve Francis (May 14)
- Re: NTp sources that work in a datacenter (was Re: Is latency equivalent bmanning (May 14)
- Re: NTp sources that work in a datacenter (was Re: Is latency equivalent to RTT?) David G. Andersen (May 14)
- Re: NTp sources that work in a datacenter (was Re: Is latency equivalent to RTT?) David G. Andersen (May 14)