Traceroute reveals your Internet tracks


Traceroute reveals your Internet tracks
Mac Tip #383, 06 May 2009

Use Traceroute to show how web pages, files or emails actually reach your machine.

Whether you call up a web page, check your email or download a file from the Internet your computer is not connected directly to the web page, email or file server.

Instead your computer sends a signal out, asking for the information. Another piece of equipment, such as your modem or router, catches that signal and sends it to the next device in the ‘chain’ — perhaps your ISP’s computer.

That device sends the signal to another device, which sends it on again, until eventually the signal reaches its destination. The web server receives the request for the web page and send the data back along the chain, until your computer finally displays the web page.

It’s similar to passing a note in a crowded theatre: you write the note, add an address on the outside, such as Seat 16A, and ask the person next to you to pass it along. They see the address and pass it to the person next to them. Each person in the chain does the same thing, and eventually the note reaches its destination.

Sometimes things break down though — the web page doesn’t appear, the email isn’t working, and you’d like to see where in the ‘chain’ things have broken down. Traceroute can help you with that.

Network Utility contains Traceroute

Traceroute shows your Internet tracks.

Traceroute shows your Internet tracks.

To use Traceroute on your Mac open Applications > Utilities > Network Utility. The Network Utility window opens to display half a dozen tabs. Click on the Traceroute tab to call up the Traceroute interface.

Enter an address and start the Trace

In the text box near the top of the window enter an Internet address, such as google.co.nz or tidbits.com.

Note: Traceroute has been misused in the past for evil purposes, so some systems may effectively disable it.

Click the Trace button.

What the Traceroute results mean

The results area in the lower part of the window now shows you the trace or track for the signal your computer sends to the address you specified.

When you run a trace your machine sends out a tiny packet of data (40 bytes). The next device along the line sends a notification to you that the data reached it. That all takes a little time, measured in milliseconds. 1 millisecond (ms) = 1/1000th of a second.

I sent a Trace to tidbits.com. The results were:

Traceroute has started ...

traceroute to tidbits.com (216.168.61.78), 64 hops max, 40 byte packets
 1  10.0.1.1 (10.0.1.1)  1.649 ms  0.846 ms  0.783 ms
 2  * [address removed].cable.telstraclear.net ([address removed])  16.623 ms  11.516 ms
 3  ae0-840.ie4.telstraclear.net (203.167.223.114)  9.515 ms  9.562 ms  9.085 ms
 4  ge-1-2-0-843.ie1.telstraclear.net (218.101.61.105)  19.958 ms  19.191 ms  19.259 ms
 5  ge-0-2-0-1.xcore1.acld.telstraclear.net (203.98.50.251)  20.550 ms  20.413 ms  19.684 ms
 6  203.167.233.10 (203.167.233.10)  20.954 ms  20.180 ms  20.439 ms
 7  i-3-2-0.wil-core02.bx.reach.com (202.84.219.117)  145.304 ms  145.401 ms  144.706 ms
 8  i-3-0-0.paix-core02.bi.reach.com (202.84.140.90)  156.312 ms  159.249 ms  155.333 ms
 9  i-1-2.paix01.bi.reach.com (202.84.251.74)  156.249 ms  155.855 ms  156.687 ms
10  peer-02.palo.twtelecom.net (198.32.175.111)  157.888 ms  157.273 ms  161.457 ms
11  216.64.147.38 (216.64.147.38)  188.444 ms  190.512 ms  188.023 ms
12  216.64.147.38 (216.64.147.38)  186.646 ms  188.405 ms  191.005 ms
13  emperor.tidbits.com (216.168.61.78)  187.616 ms  187.043 ms  196.771 ms

This Trace shows that the route from my computer first goes to my cable modem, then my service provider, TelstraClear, in Wellington, New Zealand. Then it goes up to Auckland, New Zealand. All of that is fairly quick.

Then the data heads off overseas, through the immensely long undersea cable that connects New Zealand to the West Coast of the USA. That cable’s around 13,000 Km, so it takes a while for the signals to get through.

Finally it reaches the tidbits.com server. The whole trip took just under 200 milliseconds — around 0.2 of a second.

Experiment with Traceroute while your Internet connection is working correctly. Try sending traces to different addresses and see what results come back.

Then, if things aren’t working correctly some time, try Traceroute to see if it can give you some clues about where the problem lies.

Check last Week’s Mac Tip too: How to check your Internet connection with Ping for another handy troubleshooting tool.

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