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DarlingBri
Posts: 3123
From: Left of Centre, Cork, Ireland
Status: offline
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Understanding DNS & Domain Names - 5/11/2002 16:39:27
This was a very old post I wrote for someone at Outfront more than a year ago. I found it in my files when I was housecleaning my compute, and repost it for anyone else interested.
You connect to the Internet through your ISP. Your ISP has a special Domain Name System (DNS) server that keeps a record of all the domain names it hosts, and where to find them on their web servers.
You open your browser and type in http://www.somedomain.com. Your ISP looks at that request and says, “Somedomain.com? I can’t find that on my DNS server, so that’s not hosted here. Hold on, I’ll find out where it lives.”
The DNS server you are connected to then sends an external request to what’s called a Root Server. Root servers are very large servers all over the world, co-ordinating different domain name types for a particular country. Your ISP will send a question to it’s nearest Root Server, saying “Hello, Root Server—where is somedomain.com?”
Now, the letters in a domain name are there for the convenience of people. Computers are happy to talk to each other in numbers, and each domain name has an associated IP address—a string of numbers unique to that domain name. The IP address is assigned to the domain name by the hosting company where the domain lives. In our example, somedomain.com is hosted by Bob’s Hosting Service, which has declared that it will handle all requests for anything having to do with somedomain.com. It is the somedomain.com “authority.”
So, not surprisingly, the Root Server checks it’s list and replies, “According to my records, somedomain.com is really IP address 1.1.1.1. Bob’s Hosting is authoritative for 1.1.1.1. Go ask Bob.”
Your ISP’s DNS server now knows where to send your request for somedomain.com, and sends you on your way to Bob’s Hosting Service. You arrive on Bob’s doorstep, at which point your computer says to Bob’s DNS server, “Hello, Bob, is 1.1.1.1 at home?”
Bob’s DNS server looks at your request, checks it’s records, and says “1.1.1.1? Oh, you mean somedomain.com. Sure, it’s on my web server, right here. I’ll show it to you.”
And, as if by magic, http://www.somedomain.com appears in your browser.
For more information, see:
http://www.stamey.nu/DNS/DNSHowItWorks.asp
http://www.woz.org/pages/staff/auri/dns/How_Does_It_Work.html
--Bri
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#!usr/bin/girl
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Yzywyz
Posts: 132
Joined: 6/27/2002
From: Louisville, Kentucky (USA)
Status: offline
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RE: Understanding DNS & Domain Names - 7/4/2002 21:50:42
Real headaches arise when an ISP doesn' t update their DNS entry for your domain. So their clients are directed to whatever the old address was, while the rest of the world sees the right thing.
Example: ISP X hosts site A on their servers. Customers A, B, and C use ISP' s X, Y, and Z, accordingly.
Site owner O gets tired of the outages and bad service offered by ISP X and switches to hosting and internet access through ISP Y, who hosts for a lower price and offers service with courtesy and professionalism, and takes support issues seriously.
Owner M secretly hopes ISP X will burn down and go out of business, but could get in trouble for saying it.
When Owner M requests a DNS record change, ISP Y and ISP Z get the changes right as they propagate quickly through the DNS servers. Thus, customers B and C see the site as intended.
ISP X never updates their DNS record for Owner M' s website, and to this day customer A sees the last version of Owner M' s site posted on ISP X' s servers, because their DNS request is handled by the server with the obsolete record.
Owner M wishes he would have put a redirect page on ISP X' s server before they shut off his access and disabled his password, because now he despairs that customer A will ever come back to his website, since in A' s world it is still frozen in 1999' s update.
Creepy, eh?
_____________________________
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I just run the frikkin' maze.
James
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Gil
Posts: 7533
From: North Carolina, USA
Status: offline
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RE: Understanding DNS & Domain Names - 7/6/2002 13:46:04
Good info.
But, don' t confuse the terms ISP & host. ISP = Internet Service Provider and while sometimes they are the same, not always.
_____________________________
Gil Harvey, 1947-2004
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treetopsranch
Posts: 1156
From: Cottage Grove, OR, USA
Status: online
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RE: Understanding DNS & Domain Names - 7/14/2002 14:32:17
Dumb Question here: Why did my host assign me three different IP address' s for one web site?
Don from TreeTops Ranch in Oregon
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leehintz
Posts: 383
Joined: 10/10/2000
From: Oak Creek Wisconsin USA
Status: offline
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RE: Understanding DNS & Domain Names - 7/27/2002 21:45:19
Hi TTR,
I believe the three addresses you are refering to are the name server addresses, for ns1, ns2 and optional ns3. They are associated with your domain name record. The name servers then point to your web site address (only one) assigned by your web hosting company. I hope that this helps. It' s a complex subject for most of us.
_____________________________
Lee A. Hintz, Consultant
ArtGals.com
www.artgals.com
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