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As consumers, we have been spoiled by the utility
companies, which, for the most part, own their own
equipment and provide their own maintenance. The
internet is a completely different animal, related
more to the highway system than the telephone system.
This article addresses the mechanisms used by the
internet in as non-technical a way as possible.
Every computer on the internet has an address,
not unlike a street address. Since these are numeric
addresses like 206.171.14.2, they would be difficult
to remember. Domain names were created to make it
easier for people to get where they want to be.
When you click on a link, the first thing the
browser needs to know is where you are heading.
When you type in the address Net2Business.com, it
first needs to look up the address. This is handled
by the Domain Name System or DNS. The DNS server
resides at your ISP (e.g. RoadRunner, or Earthlink,
or AOL) , and communicates with other DNS servers.
It is typical for your request to pass through 9-13
DNS servers to get to your destination. To avoid
clogging the internet with requests, DNS servers
save (cache) information for up to 12 hours. For
this reason, if you switch your web site or email
from one host to another, it can take up to two
full days for everyone to see the change.
If the DNS server of your ISP is broken, or you
can't reach it, you're dead in the water. Most ISPs
will have at least two DNS servers to prevent this
from happening.
Once the browser has the address, it will send
a request to the nearest router (called a gateway).
Since it would be unwieldy for every router to know
where every computer on the internet is, the request
is sent from that router to one that claims to know
a path to where the destination computer resides.
This is called a hop, and there will likely be many
hops between your computer and the web site you
are seeking. A hop in internet terms is the computer
stop where information is handed off to the next
"runner" in the relay event.
And this is the tricky bit. You can think of
your ISP as a toll-road on-ramp to the highway.
On the receiving end, your web host also has a paid
on-ramp. In-between is a loose collection of privately
owned routers, and there may be several companies
involved that don't have direct relationships with
each other.
You can see this in action by openning the Command
Prompt on your computer (Start|Programs|MS-DOS Prompt
under Windows 98 and NT, Start|Programs|Accessories
under all others). Type in
tracert www.yourdomain.com
tracert is short for Trace Route, and
details the travels of your request. Below is a
sample trace route for Net2Business. There is some
useful information in this gobbledy-gook, so stick
with me.
tracert net2business.com
Tracing route to net2business.com [216.243.235.10]
over a maximum of 30 hops:
- 7 ms 17 ms 7 ms 10.60.32.1
- 8 ms 7 ms 7 ms pos2-0.kscyks119-rtr1.kc.rr.com
[24.94.164.149]
- 9 ms 6 ms 7
ms pos2-0.kscymoworn-rtr1.kc.rr.com [24.94.161.201]
- 8 ms 9 ms 6 ms pos6-1.kscymordc-rtr2.kc.rr.com
[24.94.161.42]
- 7 ms 7 ms 8 ms srp14-0.kscymordc-rtr3.kc.rr.com
[24.94.160.193]
- 8 ms 11 ms 19 ms pop2-kcy-P2-0.atdn.net
[66.185.137.249]
- 10 ms 9 ms 9 ms bb1-kcy-P0-1.atdn.net [66.185.137.240]
- 20 ms 22 ms 22 ms bb1-chi-P6-0.atdn.net
[66.185.152.124]
- 20 ms 20 ms 22 ms pop2-chi-P0-0.atdn.net
[66.185.148.65]
- 21 ms 21 ms 22 ms aol-gw.cgcil.ip.att.net
[192.205.32.237]
- 21 ms 23 ms 34 ms tbr2-p012201.cgcil.ip.att.net
[12.123.6.38]
- 30 ms 29 ms 28 ms tbr2-p012301.sl9mo.ip.att.net
[12.122.10.46]
- 32 ms 32 ms 30 ms gbr6-p90.sl9mo.ip.att.net
[12.122.11.126]
- * 41 ms 38 ms ar1-p3110.desia.ip.att.net
[12.123.198.133]
- 42 ms 42 ms 41 ms 12.119.178.54
- 39 ms 40 ms 38 ms oc3-4-1.ddm-sms-1.lh.net
[216.81.154.134]
- 46 ms 45 ms 46 ms fe2-24.kcy-ar-bi1.lh.net
[216.243.197.45]
- 45 ms 47 ms 45 ms net2business.com [216.243.235.10]
Trace complete.
On the first line, you can see that the address
has been found ([216.243.235.10]).
If you get: "Unable to resolve target
system name"
…it means your DNS is broken, or you have no
connection to the internet.
The very first entry is your own router (or the
ISP's if you're on dial-up); The ms numbers are
the milliseconds (thousandths of a second) it took
for that router to respond. Numbers over 100 usually
means a traffic jam. Numbers over a thousand mean
big trouble, and you probably can't get there from
here. An * (like the one on hop 14) means the router
didn't respond.
We can get a pretty good idea of where the request
is going by looking at the domain names of the routers.
pos2-0.kscyks119-rtr1.kc.rr.com is Time Warner's
Road Runner. The kscyks part is a dead give-way
for Kansas City, Kansas. Our request goes bounding
across the Road Runner network and connects up with
pop2-kcy-P2-0.atdn.net which is AOL's network. Note
the chi in bb1-chi-P6-0.atdn.net (hop 8) which is
undoubtedly Chicago. The request then meanders through
St. Louis on the ATT network, and finally reaches
its destination on the Lighthouse network in Lenexa,
KS.
Note that even though I'm physically only a couple
of miles from the server, the request travelled
over 1000 miles. It's not unusual to see requests
pass through Florida or Dallas when headed across
the street.
Problems arise from the fact that even though
Road Runner is owned by AOL, and AOL has a relationship
with ATT, AOL does not necessarily have a relationship
with Lighthouse. So if a Road Runner customer is
having problems because of router failure further
down the line, Road Runner isn't a direct customer,
and can only ask nicely for someone to fix the problem,
if they can figure out whom to ask.
While this is little consolation if can't get
your email, it's not unlike a wreck on the highway
that blocks traffic. Everyone is inconvenienced,
but it's just one of those things. Luckily, a bum
router or bad connection affects so many people,
that outages of more than a few hours are rare.
So, the next time you see slow response from
a web or email server, you'll know that you request
has traveled on a long and perilous journey.
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