Igor Chudov wrote: > On Wed, Sep 29, 2010 at 8:12 PM, Jon Elson <[email protected]> wrote: > >> Igor Chudov wrote: >> >>> Things may have somewhat improved. >>> >>> I checked on my unsophisticated home network. Ping time (roundtrip), >>> involving three switches (one in my basement office, then the main >>> switch at the main interconnect in the utility room, then the switch >>> in the family room), and two linux boxes, is 0.21-0.34 milliseconds. >>> >>> >> My understanding of ping is that it does NOT report the total round trip >> time through >> all nodes and switches, just the last hop. I think you need traceroute >> to see the delay >> at each hop. Still, 300 uS is not such a great time if you need 3 >> messages to propagate >> within one millisecond. >> > > Jon, this is not the case. > > ``Round-trip times and packet loss statistics are computed.'' > Well, comparing results from distant nodes on the WAN seems to refute this, unless you have a ping option not present on my system. I use Charter cable modem, and their backbone is a GHASTLY mess. I have a paid secondary DNS provider with a good T3 connection. When I ping them, I get ~60ms, which is awful. But, when I traceroute them, I get 30 hops, many of them INDIVIDUALLY in the 60 ms range. So, the total round-trip message has to be several hundred ms.
Despite your quoted sentence from the ping man page, I do not believe this information is correct, due to the difference between ping and traceroute results. Compare them yourself and see if you get quite different results. Try pinging your name server or other reliable host on your WAN to put enough hops in it to make a difference. Unfortunately, the ISPs are hiding info to keep people from seeing what hideous service they are getting, so traceroute usually gives very incomplete info, now. Jon ------------------------------------------------------------------------------ Start uncovering the many advantages of virtual appliances and start using them to simplify application deployment and accelerate your shift to cloud computing. http://p.sf.net/sfu/novell-sfdev2dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
