DNS Resolution

[dusty]

Where does DNS resolution occur;

1) at the origin of a link or

2) at the destination or

3) somewhere else?

[paul heller]

Dusty, I think the answer is some of all three. My understanding is that the administrator of the destination needs to register its IP address with DNS. This is often done automatically by the company (also knows as the registrar) who assigns the domain name.

Then the DNS entries spread throughout the internet. This takes time. There are lots and lots of DNS servers throughout the internet. Each sever tells other servers about the new entry.

Eventually, your computer asks for the DNS information when you access the website, and your computer also stores it locally in something called a cache. Sometimes the local cache gets confused, and it can be reset (called clearing the cache).

If the destination changes its IP address (because it moves it server to a different location, for example), it must register again with DNS, all the DNS servers throughout the internet must update, and your local computer must update. I'm not sure how the "register again" part is accomplished.

What I wrote might not be 100% accurate, but it is pretty close.

Paul

[dusty]

Dusty, I think the answer is some of all three. My understanding is that the administrator of the destination needs to register its IP address with DNS. This is often done automatically by the company (also knows as the registrar) who assigns the domain name.

Then the DNS entries spread throughout the internet. This takes time. There are lots and lots of DNS servers throughout the internet. Each sever tells other servers about the new entry.

Eventually, your computer asks for the DNS information when you access the website, and your computer also stores it locally in something called a cache. Sometimes the local cache gets confused, and it can be reset (called clearing the cache).

If the destination changes its IP address (because it moves it server to a different location, for example), it must register again with DNS, all the DNS servers throughout the internet must update, and your local computer must update. I'm not sure how the "register again" part is accomplished.

What I wrote might not be 100% accurate, but it is pretty close.

Paul

Thank you, Paul. This is more information to maul over (keeps the gray matter pliable).

I have learned that on my end of this discussion, my ISP (QWest) maintains my IP dynamically.

[ATTACH]8194[/ATTACH]

So I guess the remaining question is how/where is "shopsmith.net" resolved to an IP address.

Whenever I am unable to reach the forum, if I do a trace using VisualRoute 2010 I find that the IP address for "shopsmith.net" cannot be found.

[jmoore65]

[quote="dusty"]Where does DNS resolution occur]

DNS relies on a hierarchical network of servers to handle resolution from human readable name (e.g. http://www.shopsmith.net) to IP address (e.g. 24.123.75.51). However, software on your computer may be caching the mapping data locally.

Each domain (e.g. shopsmith.net) has a master DNS server that is the ultimate authority on the mapping info.

Between your computer and the master DNS server is a series of other DNS servers. These servers act as caches to reduce the amount of DNS requests bouncing around the Internet backbone. Your PC is caching the info for the same reason. Mapping data is marked with an expiration timestamp, which will cause workstation or server to do a network query.

Servers generally have static IP addresses.

PCs on broadband connections will generally have dynamic addresses.

Jim

[dusty]

All of this information and so little that I really, really understand.

I sorta get it but then when it seems that everything is setup and working and then without making changes there is a hiccup - that is confusing to me. My aging mind just cannot keep up.

All of that having been said - I have been online without a hiccup since about 4:00am this morning. The traccerts that I have been running seem to run faster. Hopefully this problem is fixed.

[mickyd]

All of this information and so little that I really, really understand....

Thanks cuz there's a bunch of bright people in this forum. I always prefered too much than not enough. The 'too much' sinks in after a while.

[wlhayesmfs]

Dusty, you think you are confused I am trying to learn how to build a website and get a provider so I have been asking for advise. Still trying to understand what everyone is telling me. Not much money and seems like it all cost so much to get going. Trying to put something together so I might make a little on the side while looking for work. But enjoying my time on the SS turning and making some toys for the kids.

[wannabewoodworker]

Dusty,
If you are asking this because you cannot get to the forums at times you are not alone. I work in IT as a support engineer and do this stuff all day everyday and I cannot get to the site either on many occassions. Here is what I just got doing two different network query's.

NSLOOKUP = What is the authoritative DNS answer to the query on a domain name/IP address (Shopsmith.net)

Whois = what/who owns the domain for a particular website and what are the authoritative name servers for that domain (Shopsmith.net) this is a very simplistic explanation of what I did and I have done this many times when I cannot get to the site. It would seem they are having issues with their DNS servers or th actual web server itself seems to have a mind of it's own.


nslookup www.shopsmith.net
Server: vdns1.srv.whplny.cv.net
Address: 167.206.251.129
Non-authoritative answer:
Name: www.shopsmith.net
Address: 24.123.75.51

WHOIS - shopsmith.net


status = "Getting WHOIS results...";
Registrar: ENOM, INC.Status: clientDeleteProhibitedDates: Created 20-may-1999 Updated 22-apr-2009 Expires 20-may-2010DNS Servers: DNS1.WRIGHTFIELD.COM INTERNET.SHOPSMITH.COM I was referred to whois.enom.com; I'm looking it up there.status = "Looking up at whois.enom.com...";=-=-=-=Registration Service Provided By: Enom, IncContact: ***************@enom.comVisit: http://www.enom.com Domain name: shopsmith.netRegistrant Contact: Shopsmith, Inc. Shopsmith, Inc. () Fax: 6530 Poe Avenue Dayton, OH 45414 USAdministrative Contact: Shopsmith, Inc. Wes Powell ********@shopsmith.com) +1.9378986070 Fax: +1.9378905197 6530 Poe Avenue Dayton, OH 45414 USTechnical Contact: Shopsmith, Inc. Wes Powell ********@shopsmith.com) +1.9378986070 Fax: +1.9378905197 6530 Poe Avenue Dayton, OH 45414 USStatus: LockedName Servers: dns1.wrightfield.com internet.shopsmith.com Creation date: 20 May 1999 11:48:00Expiration date: 20 May 2010 11:48:00

[wannabewoodworker]

Has anyone tried contacting the web site admin to ask why the site is down so often??? I know I have not done that but I will tonight just to see if they can offer an explanation.

webmaster@shopsmith.com

[heathicus]

How does DNS work?

As wannabewoodworker said, it is a hierarchical system. As he also said, there are DNS servers all over the world, each with different areas of responsibility. I'll try to supplement his explanation.

The best analogy for DNS resolution is looking for a phone number in a phone book. When you call someone, you don't dial their name, you dial their phone number. Likewise, when your computer "dials" Shopsmith.net, it really dial's the IP address that web site is on. But first, it has to find what that IP address is, and that is domain name resolution.

We'll use Shopsmith.net as our example. Your computer was given the IP address of your ISP's DNS server through another protocol called DHCP (Dynamic Host Configuration Protocol - when you connect to your ISP, this is how your computer receives certain network configuration information like a unique IP address, the gateway (path out to the internet), and DNS servers).

So, you type in "www.shopsmith.net" in your web browser and hit enter. Your computer looks in your configuration for the address of the DNS server. This is most likely at your ISP. It then contacts that server and asks it "where is www.shopsmith.net?" That server answers and says, "I don't know. You should ask one of the root DNS servers. There are several of them, but we'll pick 192.112.36.4. Ask it." These root servers keep track of which DNS servers are responsible for the various top level domains (.net, .com, .org, .edu, etc).

So your computer contacts that server and asks it, "Where is www.shopsmith.net?" That root server answers, "I don't know, but one of the servers for the .net domain is at 192.35.51.30. Go ask it."

So, your computer asks that server, "Hey, do you know where www.shopsmith.net" is? It answers, "Well, I don't know, but according to the registrar (the company that the domain name was purchased/registered through), the DNS servers for shopsmith.net is at dns1.wrightfield.com (70.60.40.182) and internet.shopsmith.com (24.123.75.51). Go ask one of those."

So your computer asks dns1.wrightfield.com, "Ok, so do you know where http://www.shopsmith.net is or are you going to keep giving me the runaround?" That server answers, "Chill dude, you've come to the right place. That web site is at 24.123.75.51. Have fun there."

So then, finally, your computer talks to 24.123.75.51 and loads the web site.

Now, sometimes one of those servers may not answer, so there is redundancy built in at every level. If dns1.wrightfield.com doesn't answer quickly enough, then your computer asks internet.shopsmith.net. But if that server doesn't answer, you're out of luck and you have to wait until one of them starts answering. The higher levels are more reliable.

Also, as wannabewoodworker said, this information is cached on your computer and at your IP's DNS server. That cache is kept for a limited amount of time before the lookup is performed again.

If you want to trace the DNS resolution and find out where any problems might be, you can use this web site:

http://www.simpledns.com/lookup-dg.aspx

(It's taken me 30 minutes to write this, with tired, whiny, crying kids climbing on me and demanding various services, and I have not done any proofreading so I hope this all made sense!)