Blog O’ Matty

Measuring packet loss

In continuing on with my commitment to describe my favorite network utilities, I bring to you mtr:

$ mtr -r -c 10 mail.prefetch.net

HOST: me                           Loss%   Snt   Last   Avg  Best  Wrst StDev
  1. 10.238.4.1                    0.0%    10    9.2   8.2   5.4  12.6   2.1
  2. 68.86.108.13                  0.0%    10    9.2   9.4   6.3  14.9   2.8
  3. 68.86.106.45                  0.0%    10   15.1  10.1   6.9  17.5   3.5
  4. 68.86.106.13                  0.0%    10   14.0  11.0   5.7  22.1   4.8
  5. 68.86.106.9                   0.0%    10   14.6  11.4   7.2  18.5   3.6
  6. 12.118.120.89                 0.0%    10   10.2  10.3   8.2  14.6   2.2
  7. tbr1-p012201.attga.ip.att.ne  0.0%    10   23.8  25.8  21.8  33.9   3.6
  8. tbr2-cl1.wswdc.ip.att.net     0.0%    10   27.3  26.9  23.7  33.4   3.0
  9. ggr2-p390.wswdc.ip.att.net    0.0%    10   23.0  27.6  22.6  41.0   5.6
 10. so6-3-0-2488M.ar1.DCA3.gblx.  0.0%    10   26.0  30.4  23.9  43.3   6.3
 11. so0-0-0-622M.ar2.CLE1.gblx.n  0.0%    10  130.3  49.8  37.7 130.3  28.4
 12. Enet-Inc-Internet.so-0-3-3.a  0.0%    10   51.2  45.9  42.5  54.9   4.0
 13. extreme.xlhost.com            0.0%    10   44.2  67.1  41.4 261.4  68.3
 14. mail.prefetch.net            0.0%    10   48.3  56.6  41.5 172.9  40.9

mtr allows you to view hop-by-hop latency metrics, and is invaluable for finding busy devices between two endpoints. Some routers will place low QOS priorities on ICMP traffic, so it is important to capture traffic at various intervals to see if a device is truly overloaded.