|
North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: NTp sources that work in a datacenter (was Re: Is latencyequivalent to RTT?)
On Wed, 14 May 2003, Steve Francis wrote: > > [email protected] wrote: > > > I assume that it's fairly common for people to have Solaris or Linux > > boxes > > > >in every PoP to do measurements. In that case, the difficulty isn't in > >measuring one-way latency, it's in synchronizing the time on all the > >servers. And with fairly cheap GPS and CDMA clocks that is a lot > >easier/cheaper than it once was. > > > But what GPS clock can you install in a datacenter? AFAIK, they all > require roof (or at least window) access in order to install the > antenna. (At least, all the GPS based ntp servers I've looked at do). Half the sky is sufficient, so if you have a window that can open, you are usually fine. Just stick the receiver outside the window. > Is that not true of CDMA servers? No, they work inside buildings if there is not too much interference. An advantage of these units is that they work whereever a CDMA phone works, so it really easy to check. We have 2 CDMA units installed in data-centers and they just work. > How have others solved this issue? (Short of owning their datacenters.) For GPS: There are units on the market that can work with 250m of regular CAT5 cable between GPS receiver and PC, if the building has structured wiring, get permission to access the roof, then use the existing wiring to reach the computer room. Getting permission to access the roof is the tricky part. Henk ------------------------------------------------------------------------------ Henk Uijterwaal Email: [email protected] 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)
|