Reporting Network Response Time Problems

Last Update: July 1, 2007

[ SLAC Computer Services (SCS) | Network Group | Computer Networking ]

If you notice response time problems please report them to the SLAC HELP desk (Email help@slac.stanford.edu, phone (650)926-HELP or (650)926-4357, FAX (650)926-5400). Please include the time and date the problem was experienced, name and IP address of your computer/Xterminal and the server host, a traceroute between the hosts, the results of a set (say 20) pings between your computer/Xterminal and the server or host with which you are experiencing slow response. An example of such a set of pings from cadhub, a SunOS workstation (for a Linux host the equivalent command is ping -c 20 redwing), to the redwing computer, is shown below:

2cottrell@cadhub:~>ping -s redwing 56 20
PING redwing.SLAC.Stanford.EDU: 56 data bytes
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=0. time=7. ms
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=1. time=6. ms
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=2. time=5. ms
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=3. time=8. ms
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=4. time=6. ms
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=5. time=6. ms
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=6. time=6. ms
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=7. time=6. ms
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=8. time=6. ms
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=9. time=6. ms
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=10. time=6. ms
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=11. time=6. ms
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=12. time=10. ms
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=13. time=6. ms
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=14. time=6. ms
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=15. time=6. ms
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=16. time=5. ms
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=17. time=6. ms
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=18. time=6. ms
64 bytes from REDWING.SLAC.Stanford.EDU (134.79.128.77): icmp_seq=19. time=6. ms

----REDWING.SLAC.Stanford.EDU PING Statistics----
20 packets transmitted, 20 packets received, 0% packet loss
round-trip (ms)  min/avg/max = 5/6/10

This example is for a well functioning network. Note the consistent response time (around 6ms), and the 0% packet loss. Also note that the first ping often takes longer than the remainder due to priming the name cache. The magnitude of the minimum RTT varies depending on the distance between the hosts. Roughly speaking it is roughly 1 msec / 100 km for resonably direct routes.

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Owner: Les Cottrell