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Old 6th December 2009, 23:06   #16
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Originally Posted by Rehaan View Post
... not much would be able to beat your ISPs DNS servers. (eg. Ping to MTNL DNS server is 25ms whereas Google DNS is 130ms)
...
The reason people switch is for more consistency and less problems.
It is true that no 3rd party DNS can beat the speed of DNS name resolution provided by your ISP because in most cases, ISP DNS server and the WAN Gateway (router) is either the same box or on same network switch/hub and they would work at "wire speed". However, depending on the synchronization policy at the ISP DNS the result you get may not be accurate or some pages may load slower. Unfortunately the phone book example for DNS is overtly naive. The DNS is much more involved than a phone book analogy. DNS records have concept of TTL (expiry), zoning and round robin ordering etc. Read this on how a smart DNS could help reduce the overall website latency Performance Benefits.

ISPs sometimes block certain sites on behest of GoI. While some newly launched websites may not yet be available in the DNS cache of ISP. In such situations external 3rd party DNS helps.

What I disliked about OpenDNS was that they would return a "fabricated response" if the domain name did not exit or I mistyped an URL. I found it very irritating. Google says that they would not do so. Read the "correct results" in the bottom of this page: Introduction to Google Public DNS

-BJ
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Old 7th December 2009, 16:18   #17
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I'm using Open DNS since a couple of months now, and it works like a charm. Any reason for me to switch over at all?
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Old 7th December 2009, 18:15   #18
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I'm using Open DNS since a couple of months now, and it works like a charm. Any reason for me to switch over at all?
What is an open DNS? pardon my ignorance.
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Old 7th December 2009, 18:26   #19
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^^Google doesn't redirect to ad pages if the DNS lookup does not return any results. Never used OpenDNS or Google DNS - this is what I have gathered from the web after reading numerous articles about each service.
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Old 7th December 2009, 20:57   #20
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Originally Posted by GTO View Post
I'm using Open DNS since a couple of months now, and it works like a charm. Any reason for me to switch over at all?
Not if you don't mind the sponsored search results everytime a domain doesn't resolve/exist. OpenDNS was a good thing when it started, but it's become quite intrusive now. The quality is still there, but with a pile of you-know-what.

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Originally Posted by Jayabusa
What is an open DNS? pardon my ignorance.
OpenDNS | Internet Navigation And Security
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Old 8th December 2009, 01:00   #21
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I'm using Open DNS since a couple of months now, and it works like a charm. Any reason for me to switch over at all?

Folks ( including subject matter experts ) who have tested opendns, Google DNS and ISP DNS have found OpenDNS better in terms of response and speed. Also , ISP DNS will work better for some , due to less number of hops. so practically there is nothing pathbreaking stuff in Google DNS except the fact that they dont have ads and redirection ( at the moment ) ..but considering the google's core business strat , it wont take that long for them to include ads. ( goog no more believes in dont be evil stuff )

Google Public DNS vs OpenDNS vs Your ISP’s DNS – measuring performance - The BrowserMob Blog
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Old 8th December 2009, 02:24   #22
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Google has this thing of adding hype to whatever they do. Though I have seldom personally used it, the global DNS servers of Level 3 communications, one of the largest backbone provider in the world, have been in use. I used to use in as much as 7 years back for testing DNS issues. For those who are in the know, 4.2.2.1, 4.2.2.2, 4.2.2.3, 4.2.2.4... would be familiar numbers.

Again, unless the ISP's DNS is known to be slow in resolving or fails to resolve a bunch of times, using an alternate, external DNS resolver is only waste of precious online milliseconds

I was on Airtel in India, and have been problems-free for as far as I can remember.
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Old 8th December 2009, 03:12   #23
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I've used many public DNS services.Sticked to OpenDNS for a long time now.But ,I have experienced opendns blocking sites like orkut once in a while irritates a lot.Here in My Computer ,I have dnsadvantage servers too added(in case!).

DNS Advantage
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Old 8th December 2009, 18:22   #24
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Quote:
Originally Posted by bj96 View Post
...
What I disliked about OpenDNS was that they would return a "fabricated response" if the domain name did not exit or I mistyped an URL. I found it very irritating. Google says that they would not do so. Read the "correct results" in the bottom of this page: Introduction to Google Public DNS
That is one irritating thing about OpenDNS! I guess thats one reason to switch to google.

And yes, the phone book analogy was a basic overview for someone asking what DNS was - though i don't really know things too well beyond that level!


Here's a question. When is the secondary DNS server used? When the primary server cant be found / returns no result? or are there any other circumstances?

cya
R

Last edited by Rehaan : 8th December 2009 at 18:25.
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Old 8th December 2009, 18:37   #25
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This let me Google it for you should be used judiciously. This time it is downright arrogant (maybe unintentionally).

Do you expect people to read through a 10000 word article to get the answer?
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Old 8th December 2009, 20:14   #26
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Quote:
Originally Posted by Rehaan View Post
When is the secondary DNS server used? When the primary server cant be found / returns no result? or are there any other circumstances?
Good question Rehaan. Thanks for stimulating my neurons . I guess there is no default behavior. It depends on the application which is trying to resolve the name. For example both IE and FF falls back to secondary DNS while some other application may not do so.

Ok, before I try to elaborate, I did a quick experiment. I purposely changed my primary dns to a server that doesn't exist e.g. 8.8.8.9 (this is not a DNS server) while my secondary DNS was correct. Here is the list of DNS on my laptop (last two are opendns ). You can find the configured DNS list by going to cmd prompt and typing c:\ipconfig /all

DNS Servers . . . . . . . . . . . : 8.8.8.9
208.67.222.222
208.67.220.220

went to windows vista cmd shell and used nslookup cmd to resolve blogspot.com. Checkout the window below. It could not resolve using 8.8.8.9 and did NOT fall back automatically to secondary DNSes (208.*) However, when I specifically told nslookup cmd to resolve same site using DNS server as 208.67.222.222, it did resolve fine.

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Now when I tried http://www.blogspot.com/ in both IE and FF (with same DNS setup) both loaded the blogspot page fine.

What does this mean?

It means falling back to secondary DNS is application behavior. nslookup cmd is not querying the secondary DNS in case of failure to contact (or get any result from) primary dns, while, both IE and FF do fall back to secondary DNS to resolve names. I remember writing a network application which would iterate through as many DNS servers it would find from operating system (sometimes 3-4) to resolve a name.

Also, to experiment with different DNS setups, don't forget to flush dns cache (c:\ipconfig /flushdns) after you change your DNS servers.

Quote:
Originally Posted by ph03n!x View Post
...for testing DNS issues. 4.2.2.1, 4.2.2.2, 4.2.2.3, 4.2.2.4... would be familiar numbers
Yes I have used them. Works great.



-BJ

Last edited by bj96 : 8th December 2009 at 20:33. Reason: typo/combine posts
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Old 9th December 2009, 00:30   #27
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Quote:
Originally Posted by Rehaan View Post
That is one irritating thing about OpenDNS! I guess thats one reason to switch to google.

And yes, the phone book analogy was a basic overview for someone asking what DNS was - though i don't really know things too well beyond that level!


Here's a question. When is the secondary DNS server used? When the primary server cant be found / returns no result? or are there any other circumstances?

cya
R

You are right . When primary server is down, secondary name servers palys the main role and resolvs the domain names . seconday server always stays in touch with primary server and fetches any config changes including new entries and makes sure that both servers are uptodate ..this is called zone transfers..
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Old 9th December 2009, 09:48   #28
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Originally Posted by hondafanboy View Post
You are right . When primary server is down, secondary name servers palys .... both servers are uptodate ..this is called zone transfers..
What you said, happens at the DNS server ends and NOT on client stations like my laptop. I guess Rehaan was seeking what happens with pDNS and sDNS fields that we set in clients e.g. windows desktop network configuration.

@Rehaan- is my assumption about your question correct?

-BJ
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Old 27th September 2010, 13:44   #29
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Quote:
Originally Posted by pranavt View Post
The best way to check the effectiveness of a DNS server is to......
Use namebench.
LINK

- Its a google engineer's project that runs DNS tests from your computer.
- It will use your browsing history to see which sites you visit frequently and factor that into the test, as well as a standard list.
- It actually does a lookup and measures the overall response time, unlike a basic ping test.

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cya
R

@bj96 - yep.
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