View Full Version : DNS problems again?? :(
Tezcatlipoca
11-03-2004, 22:03
I'm in Cambridge & have started having problems accessing certain websites.
It's been happening for the last couple of days, with today getting worse.
The problems disappear if I change my DNS servers to non-NTL ones.
Have NTL's DNS servers gone tits-up once again?
Chrysalis
11-03-2004, 22:45
for me they were never working since the day I signed up :(
Haven't heard of any problems with dns at the moment... try specifying an alternative webcache proxy instead, because this quite often causes the problem that you have described. I assume you know how to do this... if not pm me for details and some to try.
hth
Chrysalis
12-03-2004, 00:01
well my problem wasnt webcache for about 7 months since I signed up I wasnt even using a webcache proxy, and dns issues went away when dns server was changed.
Not hard to work out what the problem was. On the few occasions I changed back every couple of months or so, just to see if problem was fixed it wasn't so now I just use my alternate dns servers, doesnt bother me that much.
threadbare
12-03-2004, 01:07
well my problem wasnt webcache for about 7 months since I signed up I wasnt even using a webcache proxy, and dns issues went away when dns server was changed.
Not hard to work out what the problem was. On the few occasions I changed back every couple of months or so, just to see if problem was fixed it wasn't so now I just use my alternate dns servers, doesnt bother me that much.
so how do you know its not these alternative dns servers causing the slow browsing?
Chrysalis
12-03-2004, 02:21
a dns server doesnt control throughput and maximum connections to a server, it just affects how long it takes to resolve an address and if the address is resolved correctly.
If you are routing via your default cache (proxy) servers then what dns you have specified on your pc is irrelevant for http traffic - since the proxy is doing the actual dns lookup for the site.
threadbare
12-03-2004, 17:45
a dns server doesnt control throughput and maximum connections to a server, it just affects how long it takes to resolve an address and if the address is resolved correctly.
yes, so how do you know that it isn't that causing slow browsing?
threadbare
12-03-2004, 17:47
If you are routing via your default cache (proxy) servers then what dns you have specified on your pc is irrelevant for http traffic - since the proxy is doing the actual dns lookup for the site.i am getting confused now - proxies cache pages. they can be set up to cach dns lookups afaik, and the pc itself stores dns lookups in the cache but if they are a lookup is not cahed then surely the dns server does the lookup?
JonathanLH
12-03-2004, 19:12
when going via the proxy, your browser sends the URL as you typed it to the proxy server. the proxy then resolves it (using ntl's dns?) and returns the page to you. you will need working dns however to get the ip address of the proxy server.
Chrysalis
12-03-2004, 19:31
I always got the impression when you type the domain in the browser, your computer resolves the domain using the dns servers then the request for the page is sent out, so if your dns servers cannot resolve the address then it will fail, I am sure this is how it would work, the proxies cache the web page itself not the dns lookups.
Threadbare in answer to your question, I can normally tell when the slow performance is down to dns or not, the best example that comes to mind is hotmail, when I get a large email 100kb+, when I wasnt using ntl proxies before 2 weeks ago it would be very quick, almost instant on my 1mbit connection but now it takes about 10 seconds, it seems to peak at about 30k/sec but averages lower, this is an example of poor throughput.
An example of max connections to server problem would be any page that has lots of icons, forums for example that use smilies, now I got the problem it can only load about 8 at a time before it loaded them all simultanuously.
Initial delay, after the dns delay when domain is been resolved there is now an initial delay while the proxy is checking if the page is cached and downloading it before it sends to me.
Now if my dns server was causing slow down this is what I would notice, I would get a large delay when the url was entered whilst it was trying to resolve, then once the page starts loading if everything is hosted on the same domain there will be no more delays as it is already resolved, but if images are loaded on a 3rd party site there would be further pauses whilst they are resolved, a good dns server minmises this.
i am getting confused now - proxies cache pages. they can be set up to cach dns lookups afaik, and the pc itself stores dns lookups in the cache but if they are a lookup is not cahed then surely the dns server does the lookup?
Ok, how it actually works is not quite as simple - I have now tried to explain it in a topic elsewhere. :D
JonathanLH
12-03-2004, 22:00
I always got the impression when you type the domain in the browser, your computer resolves the domain using the dns servers then the request for the page is sent out, so if your dns servers cannot resolve the address then it will fail, I am sure this is how it would work, the proxies cache the web page itself not the dns lookups.
i don't think so, because if this was so, then the proxy would be cacheing via ip address, which would not allow hosting companies to work correctly which host many domain names on 1 ip address/server.
only 1 way to test, set your proxy server as an ip address, then set your dns server to 127.0.0.1 (assuming you are not running your own dns server) therefore stopping your pc doing dns. if http on port 80 still works, then the proxy does the dns, which is what i expect.
i could be wrong though, as i have not tried this.
:shrug:
Maybe I should have asked stuart to post this topic (http://forum.nthellworld.co.uk/showthread.php?p=165689) instead :erm:
Chrysalis
13-03-2004, 03:22
well I have many domains set to 127.0.0.1 in my hosts file to block lots of ads and spyware and this hasnt stopped working when the proxies came on so I assume the dns lookups done on my pc seem to do something, as far as www servers are concerned recieving a ip url request to load site I believe that is not a problem as the domain should be in the header, I am not sure on this tho, pem has posted in another topic on how it works tho and seems to know what he is talking about.
Chrysalis
13-03-2004, 03:35
guys I am going from my cable modem to a us server (it just proxies no caching) and hotmail is a lot faster, other sites are nippier as well but hotmail is a big difference, the new problem I got now is this proxy is defenitly doing the dns lookups because the ads are now showing up, so I will need to import the data into the hosts file on my server.
127.0.0.1 is your local machine (Loopback) - anything addressed to that never leaves your PC. Combine this with the explanation on how it works and you will see how both the above are exactly as expected.
Chrysalis
13-03-2004, 15:06
proximation fixed the ads problem however this has added a small delay, still alot faster than ntl tho.
Tezcatlipoca
13-03-2004, 21:57
Haven't heard of any problems with dns at the moment... try specifying an alternative webcache proxy instead, because this quite often causes the problem that you have described. I assume you know how to do this... if not pm me for details and some to try.
hth
Cheers.
I've not tried changing proxy yet (currently not got a specified one - just using the Cambridge transparent proxy), as changing DNS seems to have done the job. I might put a specific proxy in IE, & go back to using the NTL DNS servers, & see if there's any difference.
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