Unformatted text preview: ey travel aro und the Internet?
Check o ut a to o l called tracero ute. Tracero ute repeatedly sends a cluster o f three packets
starting at the f irst ro uter co nnected to a co mputer, then the next, and so o n, building o ut the
path that packets take to their destinatio n. Tracero ute is built into all majo r deskto p o perating systems (Windo ws, Macs, Linux), and
several Web sites will run tracero ute between lo catio ns (tracero ute.o rg and
visualro ute.visualware.co m are great places to explo re). The message belo w sho ws a tracero ute perf o rmed between Irish f irm VistaTEC and Bo sto n
Co llege. At f irst, it lo o ks like a bunch o f gibberish, but if we lo o k clo sely, we can decipher what’s
go ing o n.
Figure 1 2. 5 The table abo ve sho ws ten ho ps, starting at a do main in vistatec.ie and ending in 22.214.171.124
(the table do esn’t say this, but all IP addresses starting with 136.167 are Bo sto n Co llege
addresses). The three gro ups o f numbers at the end o f three lines sho ws the time (in
milliseco nds) o f three packets sent o ut to test that ho p o f o ur jo urney. These numbers might be
interesting f o r netwo rk administrato rs trying to diagno se speed issues, but we’ll igno re them
and f o cus o n ho w packets get f ro m po int to po int. At the start o f each line is the name o f the co mputer o r ro uter that is relaying packets f o r that
leg o f the jo urney. So metimes ro uters are named, and so metimes they’re just IP addresses.
When ro uters are named, we can tell what netwo rk a packet is o n by lo o king at the do main
name. By lo o king at the ro uter names to the lef t o f each line in the tracero ute abo ve, we see
that the f irst two ho ps are within the vistatec.ie netwo rk. Ho p 3 sho ws the f irst ro uter o utside
the vistatec.ie netwo rk. It’s at a do main named tinet.net, so this must be the name o f
VistaTEC’s Internet service pro vider since it’s the f irst co nnectio n o utside the vistatec.ie
netwo rk. So metim...
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This document was uploaded on 01/31/2014.
- Winter '14