Odroid C2 - Big gigabit speed problem

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Odroid C2 - Big gigabit speed problem

Unread postby tealc59 » Fri Aug 04, 2017 12:44 am

Hello,


I'm a new ODROID C2 user, installed last kzsaq LibreELEC image, and i have problem with Gigabit Ethernet.

In fact the C2 is automatically in 1000baseT-FD, but the connection speed is incredibly sloooow. (in fact almost 0kb/s).
I have tested 2 network cables (1st is cat.6, the other is cat.5e). Both are good and the issue is the same with both of them.

When i force the link in 100baseTX-FD, all is working very well (at 100mb).


Please find attached screenshots (1000baseT-FD, then the same in 100baseTX-FD).

- 1000baseT-FD mode :
c2_libreelec_1000baseT-FD.jpg
1000baseT-FD mode
c2_libreelec_1000baseT-FD.jpg (150.6 KiB) Viewed 704 times


- 100baseTX-FD mode :
c2_libreelec_100baseTX-FD.jpg
100baseTX-FD mode
c2_libreelec_100baseTX-FD.jpg (149.64 KiB) Viewed 704 times



Thanks a lot for your assistance. It would be very cool to use gigabit ethernet instead of 100mb :-)

Best regards,
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Re: Odroid C2 - Big gigabit speed problem

Unread postby odroid » Fri Aug 04, 2017 11:21 am

Since we don't use the same image, it is not easy to help you efficiently.
Please try to use our Ubuntu image for the network configuration test.
iperf test will be helpful to narrow down the root causes too.
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Re: Odroid C2 - Big gigabit speed problem

Unread postby tealc59 » Mon Aug 07, 2017 9:33 pm

Hello,

Thanks for your answer.

Unfortunately i have tested the last Ubuntu image, then i just tried to launch Firefox (so slow i couldn't have the "google" page). I then tried to install iperf package, but again it was veeeery slow.

Since then, i put back the "working LibreElec /w forced 100mb" image on SD card, and i made another test :
- i let 1gb link without forcing 100mb, then tried to a torrent image with Transmission, i was very surprised to see a peak in torrent speed around 30MB/s (lot better, ~280mb connection)


So strange.

Thanks again for your assistance.

Best regards,
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Re: Odroid C2 - Big gigabit speed problem

Unread postby rpcameron » Tue Aug 08, 2017 12:13 am

This might be related to jumbo frames on your network. Check the MTU of the C2's eth0, as this might be the source of your problem.
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Re: Odroid C2 - Big gigabit speed problem

Unread postby tealc59 » Tue Aug 08, 2017 10:28 pm

rpcameron wrote:This might be related to jumbo frames on your network. Check the MTU of the C2's eth0, as this might be the source of your problem.



Hello rpcameron,

eth0 MTU is 1500. I don't know if i can change it (and if yes, to what value).

ip link | grep mtu
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 4096 qdisc noqueue
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP8000> mtu 1500 qdisc fq_codel qlen 1000
3: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue

I tried "ifconfig eth0 mtu 9000" but it returned an error "ifconfig: SIOCSIFMTU: Device or resource busy".

Plus, if i could change MTU, do i need to change something on my router too ? (it's my Internet provider router and i can't see any MTU option).

Thanks again for your assistance.

Regards,
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Re: Odroid C2 - Big gigabit speed problem

Unread postby odroid » Wed Aug 09, 2017 9:49 am

The maximum size of the MTU is limited at 1500 by CPU.
If your router/switch doesn't work well with the JUMBO frame feature, try to change the MTU value to 0.
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Re: Odroid C2 - Big gigabit speed problem

Unread postby rpcameron » Wed Aug 09, 2017 1:50 pm

Depending upon how you have your network settings done, you can apply jumbo frames differently. For systemd-networkd you use MTUBytes in the [Link] section of your network unit. If you are using ip, it's ip link set eth0 mtu <size>. Jumbo frames are generally 9000, but lower sizes can help too, such as 4000. But, all devices involved in the chain need to support it, so your router and any intermediate switches all need to support jumbo frames too.
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Re: Odroid C2 - Big gigabit speed problem

Unread postby tealc59 » Thu Aug 10, 2017 6:42 pm

Thanks for your answers :)

I'm not 100% sure i can change MTU in LibreELEC after testing a little :
- ip link set eth0 mtu <value> => "Device or resource busy"
- ifconfig eth0 mtu <value> => "Device or resource busy"

I'll try to do it too using Ubuntu SD soon, but it'll be on my return from vacation.

On a side note i don't think my router can handle Jumbo frames or change MTU at all (quite old box from my Internet provider, with gigabit ethernet hub, NAS... but still a 2011 model) :?
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Re: Odroid C2 - Big gigabit speed problem

Unread postby brad » Fri Aug 11, 2017 6:40 pm

tealc59 wrote:Thanks for your answers :)

I'm not 100% sure i can change MTU in LibreELEC after testing a little :
- ip link set eth0 mtu <value> => "Device or resource busy"
- ifconfig eth0 mtu <value> => "Device or resource busy"


You need to shutdown the interface before making the change and then restart it, the following command should do the trick (change the MTU for your needs)..

Code: Select all
ip link set down eth0; ip link set eth0 mtu 1501; ip link set up eth0;
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Re: Odroid C2 - Big gigabit speed problem

Unread postby tealc59 » Fri Aug 11, 2017 8:45 pm

brad wrote:You need to shutdown the interface before making the change and then restart it, the following command should do the trick (change the MTU for your needs)..
Code: Select all
ip link set down eth0; ip link set eth0 mtu 1501; ip link set up eth0;



i tried to set mtu to "0", but it didn't work (invalid argument). I could set eth0 mtu to 3710 at max.

Code: Select all
ip link set down eth0; ip link set eth0 mtu 3710; ip link set up eth0;


Problem remains :-\ (no change done on router as i can't change anything on it)
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Re: Odroid C2 - Big gigabit speed problem

Unread postby gnif » Tue Aug 15, 2017 8:55 pm

The C2 MCU doesn't support MTUs larger then 3582

See this thread for more information:

viewtopic.php?f=141&t=27456
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