Jon Elson 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. Nope. It would be pretty useless to see how long it takes packets to get from your switch to your PC, when you're trying to see how long it takes to get to some FTP server. > I think you need traceroute > to see the delay > at each hop. That's true, but is also generally not needed. Since you don't care how long it takes to get from switch 1 to switch 2 (unless you're considering eliminating one or more of them), you don't need to see the intermediate times. The time ping reports is the cumulative time. There's a program called "mtr" which gives a very nice display of ping times, by the way. > Still, 300 uS is not such a great time if you need 3 > messages to propagate > within one millisecond. > Note that ping is one outbound and one reply packet. The pinging machine has to get a response back before it can know the delay time. I don't know how ping calculates the delay time though - start of send to end of receive, end of send to end of receive, compensation for the number of bytes, etc.
The minimum packet size can actually carry a fair amount of information too, it's a 46 byte payload I think. You can try using larger packets (ping -s packetsize) to see how much time a real data exchange would take. - Steve ------------------------------------------------------------------------------ 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
