Very slow network response time

vodyle · 03-14-2010, 05:03 PM

Hello!

It's been a while since I posted on a linux forum, so please tell me if I left out any vital information. Found no answer by myself for a long time, so I figured it's worth asking for advice.

I've noticed over the past few months that my internet connection speed (D/Ls, browsing) are getting incredibly slow, but only on my linux box (my laptop, for instance, is fine - in fact, I'm dual-booting with WinXP and it isn't happening there, so I think I've managed to narrow it down to the OS alone):

Code:

uname -a
Linux PC 2.6.27-1-mepis-smp #1 SMP PREEMPT Fri Jan 8 13:33:17 EST 2010 i686 GNU/Linux

It seems to me this only happens when DNS is involved - I get very very slow responses when dealing with a URL instead of a direct IP address (pinging or tracing, for example (same goes for simple web browsing - replacing the URL with the server's IP seems much quicker)).Like I said, this doesn't happen on my Windows system (same machine) or my laptop. Some output:

Code:

ifconfig
eth0      Link encap:Ethernet  HWaddr 00:15:f2:17:6b:d9
          inet addr:194.166.1.100  Bcast:255.255.255.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:576  Metric:1
          RX packets:1566622 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1248558 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:799020027 (762.0 MiB)  TX bytes:129391039 (123.3 MiB)
          Interrupt:23 Base address:0x6000

Code:

root@Mepis:/# ping www.linuxquestions.org -c 10
PING www.linuxquestions.org (75.126.162.205) 56(84) bytes of data.
64 bytes from www.linuxquestions.org (75.126.162.205): icmp_seq=1 ttl=47 time=194 ms
64 bytes from www.linuxquestions.org (75.126.162.205): icmp_seq=2 ttl=47 time=192 ms
64 bytes from www.linuxquestions.org (75.126.162.205): icmp_seq=3 ttl=47 time=199 ms
64 bytes from www.linuxquestions.org (75.126.162.205): icmp_seq=4 ttl=47 time=201 ms
64 bytes from www.linuxquestions.org (75.126.162.205): icmp_seq=5 ttl=47 time=208 ms
64 bytes from www.linuxquestions.org (75.126.162.205): icmp_seq=6 ttl=47 time=210 ms
64 bytes from www.linuxquestions.org (75.126.162.205): icmp_seq=7 ttl=47 time=197 ms
64 bytes from www.linuxquestions.org (75.126.162.205): icmp_seq=8 ttl=47 time=193 ms
64 bytes from www.linuxquestions.org (75.126.162.205): icmp_seq=9 ttl=47 time=209 ms
64 bytes from www.linuxquestions.org (75.126.162.205): icmp_seq=10 ttl=47 time=207 ms

--- www.linuxquestions.org ping statistics ---
10 packets transmitted, 10 received, 0% packet loss, time 46961ms
rtt min/avg/max/mdev = 192.591/201.431/210.705/6.752 ms

root@Mepis:/# ping 75.126.162.205 -c 10
PING 75.126.162.205 (75.126.162.205) 56(84) bytes of data.
64 bytes from 75.126.162.205: icmp_seq=1 ttl=47 time=201 ms
64 bytes from 75.126.162.205: icmp_seq=2 ttl=47 time=202 ms
64 bytes from 75.126.162.205: icmp_seq=3 ttl=47 time=232 ms
64 bytes from 75.126.162.205: icmp_seq=4 ttl=47 time=222 ms
64 bytes from 75.126.162.205: icmp_seq=5 ttl=47 time=217 ms
64 bytes from 75.126.162.205: icmp_seq=6 ttl=47 time=202 ms
64 bytes from 75.126.162.205: icmp_seq=7 ttl=47 time=193 ms
64 bytes from 75.126.162.205: icmp_seq=8 ttl=47 time=201 ms
64 bytes from 75.126.162.205: icmp_seq=9 ttl=47 time=202 ms
64 bytes from 75.126.162.205: icmp_seq=10 ttl=47 time=199 ms

--- 75.126.162.205 ping statistics ---
10 packets transmitted, 10 received, 0% packet loss, time 9038ms
rtt min/avg/max/mdev = 193.307/207.615/232.223/11.659 ms

root@Mepis:/# tracert www.linuxquestions.org
traceroute to www.linuxquestions.org (75.126.162.205), 30 hops max, 40 byte packets
 1  BB-152-60.018.net.il (91.205.152.60)  17.268 ms  17.608 ms *
 2  * * *
 3  * * *
 4  * * *
 5  * * *
 6  * ge2-0.gw1.ptk.nv.net.il (212.143.10.209)  28.673 ms  33.797 ms
 7  * * *
 8  * * *
 9  * * *
10  * * *
11  * * vlan69.csw1.Frankfurt1.Level3.net (4.68.23.62)  80.255 ms
12  ae-62-62.ebr2.Frankfurt1.Level3.net (4.69.140.17)  83.185 ms * *
13  * * *
14  * * *
15  * * *
16  * * *
17  * ae-7.ebr3.Dallas1.Level3.net (4.69.134.21)  204.299 ms  204.281 ms
18  ae-1-60.edge3.Dallas1.Level3.net (4.69.145.8)  196.419 ms  196.768 ms  196.777 ms
19  te2-1.cer01.dal01.dallas-datacenter.com (4.71.198.18)  197.268 ms  197.274 ms  198.667 ms
20  * * *
21  po1.fcr02.dal01.dallas-datacenter.com (66.228.118.178)  203.573 ms  203.573 ms *
22  www.linuxquestions.org (75.126.162.205)  202.069 ms * *

Connected by ethernet to my TP-Link router (WR641G) => to the modem => to the ISP using L2TP. Even though this only occurs on this OS I made sure - no packet loss, no ethernet card (or PCI bus) errors in logs or in ifconfig.
If this was an ISP issue then it would not have had an effect only on my Linux OS; same goes for router, cables or ethernet card.
This must be simple but I'm afraid I have little knowledge in networking, and unfortunately I'm now a student so I have very little time to dig up info and mess things up - losing my internet connection = no grades = no diploma.

Thanks in advance! All replies will be appreciated.

irishbitte · 03-14-2010, 05:35 PM

Can you give some info on your linux distribution, and your network configuration, that is, have you set your IP address locally to be static for some reason?

vodyle · 03-15-2010, 02:36 AM

I'm running Mepis 8, kernel version 2.6.27-1. Getting the IP from the router (set as gateway) by DHCP (just like the two other systems). I'm using address reservation for this specific MAC address to allow port forwarding (had a few ports opened in iptables but that's about it).
I might as well mention: /etc/resolve.conf was updated to be:

Code:

user@Mepis:~\ >> cat /etc/resolv.conf
nameserver 194.166.1.1    # <= router
nameserver 91.205.152.152    # ISP DNS

irishbitte · 03-15-2010, 07:19 PM

Why have you the nameserver of your ISP in /etc/resolv.conf? I'm not sure I get what you're trying to achieve. Is it not simpler to allow the router to handle external DNS for you? This will probably solve your speed issue. Try commenting out the second nameserver in /etc/resolv.conf, then reload your net connection.

vodyle · 03-16-2010, 02:59 AM

This was a few months back, when I had to set up the network in a haste - there might have been an original DNS problem, I honestly can't remember. It seems that resolv.conf is run over with these nameservers whenever I restart the network services, so I must have hard-coded it somewhere; still trying to figure out where... :-| I'll update as soon as I find out where I messed up.
Can this explain the long response times? Why would it matter if the machine simply uses the external DNS, instead of going through the router (which uses it anyway)?

vodyle · 03-18-2010, 06:08 PM

Solved.

Something weird with Mepis's network manager - it kept updating resolv.conf with these addresses even after I removed them manually. Reset everything, set to DHCP and restarted the network services - it now only uses the ISP nameservers and everything works fine. My mistake, as always. :-)

Thanks for the help, irishbitte!

ericsully · 04-29-2010, 09:58 AM

If your having issues with response time there is a free tool that can help to monitor this, Response Time Monitoring Tool

irishbitte · 04-30-2010, 07:00 AM

Glad you got sorted vodyle, good stuff! Can you remember where you hardcoded the initial resolv.conf file? How did you solve your issue, did you find the script you had hardcoded and change it, or what? Just to give more info for anyone who finds this thread. Cheers! :-D

vodyle · 05-14-2010, 02:10 PM

Took me a while to reply, sorry.
ericsully - thanks for the link! I'll check it out.

It seems I didn't hard-code anything, apparently I wasn't THAT much in a rush.

Something weird with Mepis' Network Assistant; I entered these addresses as static in the past (so not to get them from the router), but after switching back to "Use DHCP for DNS" it kept updating resolv.conf with them anyway (something similar happened to me in Mepis 7). After erasing them from the "Static" mode, switching back to DHCP and applying, things now work fine.