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I just reinstalled Ubuntu to my Toshiba Satellite and uninstalled Windows 10 and the old Ubuntu on the system. My Internet worked fine on Windows 10, but is extremely slow on Ubuntu and I never solved this problem on my previous Ubuntu install.

I ran the Ubuntu wireless-info script and pasted the contents into a pastebin: http://pastebin.com/SymfQikh

Can someone help me figure out what my problem is and what I can do to increase my speeds?

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From your wireless-info output:

wlp3s0    Link encap:Ethernet  HWaddr <MAC 'wlp3s0' [IF2]>  
          inet addr:172.21.227.43  Bcast:172.21.255.255  Mask:255.255.0.0
          inet6 addr: fe80::a06b:d623:7a53:48a/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:95202 errors:0 dropped:0 overruns:0 frame:0
          TX packets:81103 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:124882281 (124.8 MB)  TX bytes:8863246 (8.8 MB)

On the 4th line, MTU:1500 shows the misconfiguration. MTU is the Maximum Transmission Unit, the size, in bytes, of the largest packet your system will send. Any larger lump-of-data to send will be split into multiple packets.

An MTU:1500 setting will cause your system to send 1500 byte packets to wlp3s0, which, because it's wireless, will wrap your 1500-byte packet in some additional metadata, making the actual packet length larger than 1500. Your ONE packet will have to be split into TWO packets to transmit. It takes longer to send two packets.

What can be done?

Install the iputils-tracepath package:

sudo apt-get install iputils-tracepath

Read man tracepath, then

tracepath -n slashdot.org

and look at the pmtu (Path MTU) value. Remember this number! Or, have the shell remember it for you:

 newMTU=$(tracepath -n slashdot.org| grep -o 'pmtu [0-9]\+'| tail -n 1 | awk '{print $2}')

Then, change the MTU. Since the MTU configuration setting is used in setting up the connection, you must do the Down-Change-Up dance. Note this is going to break all connections going through wlp3s0, so, if you're administering this system remotely (via ssh) you will be disconnected.

sudo ifconfig wlp3s0 down
sudo ifconfig wlp3s0 mtu $newMTU
sudo ifconfig wlp3s0 up

Alternate method:

Change the configuration of your router to provide the $newMTU value via DHCP, then take wlp3s0 down and up.

  • My pmtu value is 1500, what should I do? – ThisIsNotAnId Mar 7 at 16:38

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