wondering about setting up a local DNS cache [resolved]

[mmmmna]

I've used OpenDNS for some time, and it is serving my needs for restricting porn from certain users. Sadly, the OpenDNS configuration which serves in one way is also slowing us all down. I've seen Firefox say 'looking up www.l kjaskljashd...' and needing several seconds while nothing is happening on the screen (and that message is not flickering), after that, the requested page tosses some information and Firefox changes to saying 'fetching...' and whatnot. Since the 'looking up' phase is the process of telling my browser the proper IP address to use to call the page to load, I see this as a problem fetching from the DNS server.

I have tried Google's DNS service, and those delays are MUCH longer, usually 6-10 seconds, often 15 seconds, and sometimes nearly 20 seconds before the fetching phase begins.

I've read that Bodacious Bacon (aka U bun tu) can be configured to use a local DNS cache, so now I'm curious about the process.

If anyone can answer:
Now big is the common DNS cache? I once heard, 8 years ago, that it was around 318 megs, but maybe I was thinking of a Mopar V8 engine.... too long ago.
Are there any tools in PCLOS which can be set to refresh a local DNS cache on a periodic basis?
Would I need to subscribe to something in order to have a reasonable experience or can I just get a full mirror of some existing public DNS server and refresh that every so often?

I suspect that setting up a DNS server is probably easy in this day and age, and would appreciate any suggested package to handle the needs I've outlined.


I'm going to pause this thread, because I was chasing the local DNS cache method as a way to speed up browser delays. Problem seems to have been Firefox configuration to allow IPV6 lookups. Yes, a classic tweak, but I forgot how slowly Firefox will respond without disabling IPV6.

[muungwana]

I set up a DNS cache couple of months ago and then i removed it because i didnt see any improvement.

There is one in the repository but i dont remember its name at the moment.

This is how it works, you make a DNS request, the server checks its cache, if it cant fulfill the request, it then goes online and get it and store it in its cache and pass it one. All subsequent requests will be fetched from the cache speeding up things hence you dont have to download and maintain a DNS cache, it is maintained automatically and on the fly.

[mmmmna]

I set up a DNS cache couple of months ago and then i removed it because i didnt see any improvement.
...

This is how it works, you make a DNS request, the server checks its cache, if it cant fulfill the request, it then goes online and get it and store it in its cache and pass it one. All subsequent requests will be fetched from the cache speeding up things hence you dont have to download and maintain a DNS cache, it is maintained automatically and on the fly.

Thanks for your informative reply.

Could that program have been configured so as to cache everything first and thus NOT fetch each missing URL?  I just had a 4 second look-up for Google; I would expect that to reduce to about 1/2 second if the match happens with the cache inside my machine.

[muungwana]

I am not aware of any DNS cache program that comes with its own list of entries.

[AS]

I have tried Google's DNS service, and those delays are MUCH longer, usually 6-10 seconds, often 15 seconds, and sometimes nearly 20 seconds before the fetching phase begins.

Sorry for the intrusion, but the times you are showing are really very high. Are you sure it's a DNS problem and not some some other network related problem ?
can I suggest you some simple command to check the answer time of a DNS ? (you will find my results quoted below)

google dns:
try the following, should report the round trim time from your location to google DNS:
ping -c 3 8.8.8.8

Code:

ping -c 3 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_req=1 ttl=52 time=25.7 ms
64 bytes from 8.8.8.8: icmp_req=2 ttl=52 time=26.5 ms
64 bytes from 8.8.8.8: icmp_req=3 ttl=52 time=25.7 ms

try:
time -p ping -c 1 www.google.com

PING www.l.google.com (74.125.232.114) 56(84) bytes of data.
64 bytes from www.l.google.com (74.125.232.114): icmp_req=1 ttl=54 time=16.1 ms

--- www.l.google.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 16.176/16.176/16.176/0.000 ms
real 0.23
user 0.00
sys 0.00

above in blue color the answer time of the IP address, the time in red includes the DNS query time too.

lastly try to ping the IP address you have seen in the previous ping (in my case was 74.125.232.114)
time -p ping -c 1 74.125.232.114

PING 74.125.232.114 (74.125.232.114) 56(84) bytes of data.
64 bytes from 74.125.232.114: icmp_req=1 ttl=54 time=16.9 ms

--- 74.125.232.114 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 16.966/16.966/16.966/0.000 ms
real 0.01
user 0.00
sys 0.00

Theoretically you should obtain times of the same magnitude of those you saw from browser ...
Sorry if the things above were really obvious, my post is just about to not overlook something else.

AS

[muungwana]

I was thinking the same thing, his DNS responses are taking way too long and i wondered in silence where he is. These dns servers are in america and maybe the slowdown is due to time and route his traffic takes on its way there and back and this is a function of where he is in the world.

A reginal(maybe from local ISPs) dns server could speed things up.

If he has multiple computers, setting up different dns servers for different users could also solve the problem. Those whose web experience need to be monitored could be on one dns server and the rest on another.

It would have been better if he presented a problem and ask for solutions than to come up with a solution on his own and then ask for help on how to implement the solution.

[mmmmna]

I am not aware of any DNS cache program that comes with its own list of entries.

I didn't imply that the program should install along with a full cache; I was thinking more along the lines of installing the program then running an update session to acquire a full, fresh cache.   

[mmmmna]

I have tried Google's DNS service, and those delays are MUCH longer, usually 6-10 seconds, often 15 seconds, and sometimes nearly 20 seconds before the fetching phase begins.

Sorry for the intrusion, but the times you are showing are really very high. Are you sure it's a DNS problem and not some some other network related problem ?

Intrusion? NOT! This is a forum thread! Besides, I've made wrong assumptions before, this could be yet another.

I suppose I cannot definitively declare that the DNS lookup is the whole delay. I can only say that from the time I click a link, to the time when the time the destination begins loading, I experience this: A] Firefox says "Looking up....", then many whole seconds elapse (counted via a real timepiece), then, B] Firefox changes its status message to "Fetching..." AND something begins loading in Firefox at that same moment.

can I suggest you some simple command to check the answer time of a DNS ? (you will find my results quoted below)

google dns:
try the following, should report the round trim time from your location to google DNS:
ping -c 3 8.8.8.8

My results are:

Code:

[mmmmna@localhost ~]$ ping -c 3 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_req=1 ttl=56 time=31.4 ms
64 bytes from 8.8.8.8: icmp_req=2 ttl=56 time=30.5 ms
64 bytes from 8.8.8.8: icmp_req=3 ttl=56 time=31.3 ms

--- 8.8.8.8 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2023ms
rtt min/avg/max/mdev = 30.572/31.143/31.483/0.454 ms
[mmmmna@localhost ~]$

Reasonable data.

try:
time -p ping -c 1 www.google.com

My data:

Code:

[mmmmna@localhost ~]$ time -p ping -c 1 http://www.google.com
ping: unknown host http://www.google.com
Command exited with non-zero status 2
real 0.15
user 0.00
sys 0.00
[mmmmna@localhost ~]$ time -p ping -c 1 http://www.google.com
ping: unknown host http://www.google.com
Command exited with non-zero status 2
real 0.12
user 0.00
sys 0.00
[mmmmna@localhost ~]$ time -p ping -c 1 http://www.google.com
ping: unknown host http://www.google.com
Command exited with non-zero status 2
real 0.10
user 0.00
sys 0.00
[mmmmna@localhost ~]$

Hehehe... wow.
Google DNS can't find Google.

lastly try to ping the IP address you have seen in the previous ping (in my case was 74.125.232.114)
time -p ping -c 1 74.125.232.114

Again, here is my data:

Code:

[mmmmna@localhost ~]$ time -p ping -c 1 74.125.232.114
PING 74.125.232.114 (74.125.232.114) 56(84) bytes of data.
64 bytes from 74.125.232.114: icmp_req=1 ttl=54 time=116 ms

--- 74.125.232.114 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 116.145/116.145/116.145/0.000 ms
real 0.11
user 0.00
sys 0.00
[mmmmna@localhost ~]$ time -p ping -c 1 74.125.232.114
PING 74.125.232.114 (74.125.232.114) 56(84) bytes of data.
64 bytes from 74.125.232.114: icmp_req=1 ttl=54 time=115 ms

--- 74.125.232.114 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 115.593/115.593/115.593/0.000 ms
real 0.11
user 0.00
sys 0.00
[mmmmna@localhost ~]$

So that is that.

Theoretically you should obtain times of the same magnitude of those you saw from browser ...
Sorry if the things above were really obvious, my post is just about to not overlook something else.

I'll offer my explanation for why I wanted to have a local DNS cache of any value.

These tests are sending a ping request to an IP address.
Q: Doesn't the DNS situation determine the proper destination IP address address according to what is defined in some record? I believe it does, to a large extent. That said, and with a major amount of simplification, lets assume a record exists where the ping calls are sent to a single specific server. Is there any definitive requirement where the IP address for a ping request also shares the same IP address for HTTP requests? I believe not. Therefore, any ping test results will likely not be responses from the same servers where http data is served.
Therefore, testing ping times will probably be unrelated to ever possible cause of slow http responses.

Besides that, when you use Googles public DNS, IIRC, Googles terms state that Google is going to analyze the data. I'd say that the time for them to analyze the data is part of why I get such slow responses. From that conclusion, I return to the request about setting up a local DNS server.

[menotu]

Don't know whether this narrows down the answer to your problem mmmmna but I'm currently using OpenDNS and not seeing any slowing down of web calls.

The Namebench app - in the repos says this:

"Namebench is a benchmarking utility

Namebench hunts down the fastest DNS servers available for your computer to use. Namebench runs a fair and thorough benchmark using your web browser history, tcpdump output, or standardized datasets in order to provide an individualized recommendation. Namebench does not modify your system in any way. Namebench is available with a graphical user interface as well as a command-line interface."

[AS]

I have tried Google's DNS service, and those delays are MUCH longer, usually 6-10 seconds, often 15 seconds, and sometimes nearly 20 seconds before the fetching phase begins.

Sorry for the intrusion, but the times you are showing are really very high. Are you sure it's a DNS problem and not some some other network related problem ?

Intrusion? NOT! This is a forum thread! Besides, I've made wrong assumptions before, this could be yet another.

I suppose I cannot definitively declare that the DNS lookup is the whole delay. I can only say that from the time I click a link, to the time when the time the destination begins loading, I experience this: A] Firefox says "Looking up....", then many whole seconds elapse (counted via a real timepiece), then, B] Firefox changes its status message to "Fetching..." AND something begins loading in Firefox at that same moment.

can I suggest you some simple command to check the answer time of a DNS ? (you will find my results quoted below)

google dns:
try the following, should report the round trim time from your location to google DNS:
ping -c 3 8.8.8.8

My results are:

Code:

[mmmmna@localhost ~]$ ping -c 3 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_req=1 ttl=56 time=31.4 ms
64 bytes from 8.8.8.8: icmp_req=2 ttl=56 time=30.5 ms
64 bytes from 8.8.8.8: icmp_req=3 ttl=56 time=31.3 ms

--- 8.8.8.8 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2023ms
rtt min/avg/max/mdev = 30.572/31.143/31.483/0.454 ms
[mmmmna@localhost ~]$

Reasonable data.

Of course, 30ms are a quite reasonable time, you can try also using the IP address of OpenDNS.

try:
time -p ping -c 1 www.google.com

My data:

Code:

[mmmmna@localhost ~]$ time -p ping -c 1 http://www.google.com
ping: unknown host http://www.google.com
Command exited with non-zero status 2
real 0.15
user 0.00
sys 0.00
[mmmmna@localhost ~]$ time -p ping -c 1 http://www.google.com
ping: unknown host http://www.google.com
Command exited with non-zero status 2
real 0.12
user 0.00
sys 0.00
[mmmmna@localhost ~]$ time -p ping -c 1 http://www.google.com
ping: unknown host http://www.google.com
Command exited with non-zero status 2
real 0.10
user 0.00
sys 0.00
[mmmmna@localhost ~]$

Hehehe... wow.
Google DNS can't find Google.

No, there is an error introduced by the forum editor: ping must be used with a hostname without the http:// prefix
please retry the command by handwriting the command (without quotes):
"time -p ping -c 1 www.google.com"

lastly try to ping the IP address you have seen in the previous ping (in my case was 74.125.232.114)
time -p ping -c 1 74.125.232.114

Again, here is my data:

Code:

[mmmmna@localhost ~]$ time -p ping -c 1 74.125.232.114
PING 74.125.232.114 (74.125.232.114) 56(84) bytes of data.
64 bytes from 74.125.232.114: icmp_req=1 ttl=54 time=116 ms

--- 74.125.232.114 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 116.145/116.145/116.145/0.000 ms
real 0.11
user 0.00
sys 0.00
[mmmmna@localhost ~]$ time -p ping -c 1 74.125.232.114
PING 74.125.232.114 (74.125.232.114) 56(84) bytes of data.
64 bytes from 74.125.232.114: icmp_req=1 ttl=54 time=115 ms

--- 74.125.232.114 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 115.593/115.593/115.593/0.000 ms
real 0.11
user 0.00
sys 0.00
[mmmmna@localhost ~]$

So that is that.

The IP 74.125.232.114 is what I have obtained from www.google.com, but I'm in Europe, once  you have repeated the ping to www.google.com
you will find an IP which probably will answer much faster for you.

Theoretically you should obtain times of the same magnitude of those you saw from browser ...
Sorry if the things above were really obvious, my post is just about to not overlook something else.

I'll offer my explanation for why I wanted to have a local DNS cache of any value.

These tests are sending a ping request to an IP address.
Q: Doesn't the DNS situation determine the proper destination IP address address according to what is defined in some record? I believe it does, to a large extent.

Yes, more or less a DNS work like a phonebook, you ask by name and it will answer an IP number.

That said, and with a major amount of simplification, lets assume a record exists where the ping calls are sent to a single specific server. Is there any definitive requirement where the IP address for a ping request also shares the same IP address for HTTP requests? I believe not.

Yes, ping use a different protocol from http (ICMP vs. TCP) but both requests share the same route and destination.

Therefore, any ping test results will likely not be responses from the same servers where http data is served.
Therefore, testing ping times will probably be unrelated to ever possible cause of slow http responses.

No, see above, however my request to evaluate "ping answer" are only directed to exclude other (eventually hidden) problems.

Besides that, when you use Googles public DNS, IIRC, Googles terms state that Google is going to analyze the data. I'd say that the time for them to analyze the data is part of why I get such slow responses. From that conclusion, I return to the request about setting up a local DNS server.

No, at least not to the level to impact so much to leave you with such long waits. (Other than this I believe that google simply record all traffic (origin + destination) and then will process this data later, as a completely separated process).

@menotu,
thank for the suggestions, greatly appreciated,
however, as said before my aim is to avoid to search for a DNS problem when possibly the problem is not the DNS,
this because I believe that a web page rendered after 10 +- 15 secs may be it's not an issue exclusively related to DNS.

And of course a DNS answer time of 30ms like shown from mmmmna let me believe that the problem is elsewhere.

AS

[Was_Just19]

Sounds to me like an IPv4/IPv6 problem.

I would ensure that IPv6 is disabled in FF if not in use.

Under about:config

network.dns.disableIPv6;                 true

[mmmmna]

Code:

[mmmmna@localhost ~]$ time -p ping -c 1 [url=http://www.google.com]www.google.com[/url]
PING [url=http://www.l.google.com]www.l.google.com[/url] (74.125.230.113) 56(84) bytes of data.
64 bytes from 74.125.230.113: icmp_req=1 ttl=57 time=92.5 ms

--- [url=http://www.l.google.com]www.l.google.com[/url] ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 92.521/92.521/92.521/0.000 ms
real 5.34
user 0.00
sys 0.00
[mmmmna@localhost ~]$ time -p ping -c 1 [url=http://www.google.com]www.google.com[/url]
PING [url=http://www.l.google.com]www.l.google.com[/url] (74.125.230.116) 56(84) bytes of data.
64 bytes from 74.125.230.116: icmp_req=1 ttl=57 time=95.5 ms

--- [url=http://www.l.google.com]www.l.google.com[/url] ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 95.584/95.584/95.584/0.000 ms
real 5.22
user 0.00
sys 0.00
[mmmmna@localhost ~]$

In any event, my browser can exhibit delays to beginning to load which are  as quick as a fraction of a second.

Dropping Google DNS, returning to the default OpenDNS service.

[mmmmna]

Sounds to me like an IPv4/IPv6 problem.

I would ensure that IPv6 is disabled in FF if not in use.

Under about:config

network.dns.disableIPv6;                 true

Excellent post. I just installed PCLOS after wiping Kubun tu, and I have forgotten to tweak the (newly installed) browser.

To be sure, let me give this configuration a test run before I seek more assistance.

PS: Just out of curiosity, will delays like this be the norm when IPV6 becomes mandatory and we no longer can disable this in Firefox?

[muungwana]

PS: Just out of curiosity, will delays like this be the norm when IPV6 becomes mandatory and we no longer can disable this in Firefox?

It depends, an application gives a small waiting window when it makes a DNS request before giving up. If it defaults to ipv6 DNS request and a request fails then the delay will be there because it will first wait for a response and then giving up on ipv6 and then try an ipv4 request which will succeed.

A default ipv4 DNS lookup will always be faster than a default first look up on ipv6 at the moment because the chances of hitting a working ipv6 system is not very high and the delay will almost always be there.

[AS]

[mmmmna@localhost ~]$ time -p ping -c 1 www.google.com
PING www.l.google.com (74.125.230.113) 56(84) bytes of data.
64 bytes from 74.125.230.113: icmp_req=1 ttl=57 time=92.5 ms

--- www.l.google.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 92.521/92.521/92.521/0.000 ms
real 5.34
user 0.00
sys 0.00
[mmmmna@localhost ~]$ time -p ping -c 1 www.google.com
PING www.l.google.com (74.125.230.116) 56(84) bytes of data.
64 bytes from 74.125.230.116: icmp_req=1 ttl=57 time=95.5 ms

--- www.l.google.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 95.584/95.584/95.584/0.000 ms
real 5.22
user 0.00
sys 0.00
[mmmmna@localhost ~]$

In any event, my browser can exhibit delays to beginning to load which are  as quick as a fraction of a second.

Dropping Google DNS, returning to the default OpenDNS service.

now that's is interesting, because even with an answer time of approx 100ms, you are receiving a DNS answer after 5 secs.
As highlighted from Just19 and muungwana it can be an IPv6 issue, still may be something else.

(Note: the default timeout for dns resolver is 5 secs)

can you post the content of your /etc/resolv.conf ?
additionally can you check the status of the services resolvconf and nscd:
chkconfig --list resolvconf
chkconfig --list nscd