Using MTR to Detect Network Congestion

Matt's Traceroute is an application you can use to do a repeated TRaceroute in real time; it dynamically shows the round-trip time to reach each hop along the TRaceroute path. The constant updates enable you not only to visually determine which hops are slow, but also to determine when they appear to be slow. It is a good tool to use whenever you suspect there is some intermittent network congestion.

You type mTR followed by the target IP address to get output similar to the following:

     [root@bigboy tmp]# mtr 192.168.25.26
                         Matt's traceroute  [v0.52]
     Bigboy                                        Fri Feb 20 17:19:17 2004
     Keys:  D - Display mode    R - Restart statistics    Q - Quit
                                        Packets               Pings
     Hostname                        %Loss  Rcv  Snt  Last Best  Avg   Worst
        1. 192.168.1.1                    0%   17   17   32   10   15    32
        2. 192.168.2.254                  0%   17   17   12   11   18    41
        3. 192.168.3.15                   0%   17   17   23   14   18    25
        4. 192.168.18.35                  0%   16   16   24   23   29    42
        5. 192.168.25.26                  0%   16   16   23   21   26    37
     ^C
     [root@bigboy tmp]#

One of the nice features of MTR is that it gives you the best, worst, and average round-trip times in milliseconds for the probe packets between each hop along the way to the final destination. The advantage of this is that you can let MTR run for an extended period of time, acting as a constant monitor of communication path quality. The constant refreshing of the screen also enables you to instantaneously spot transient changes in quality fairly easily, making it much more convenient than a regular TRaceroute.

MTR is automatically installed as part of Fedora Linux. If MTR isn't installed on your system, you can download the RPM software installation package from many of the Fedora download sites. The installation of RPMs is covered in Chapter 6, "Installing RPM Software." There is even a free Windows version called WinMTR.