Wi-fi speed

[PowerGod]

I know, too many discussion about the topic, but I just found something strange that I never noticed.

When downloading a file through internet (considering a clean connection without interferences), the download speed of the Pandora is 60 kb/s (same speed with different browsers or directly with wget)

Downloading with the PC the SAME file on the same server is ~360 kb/s

And here nothing new, there is a lot of people with this kind of comparison...

BUT if I use a bittorrent client on the Pandora, the speed goes (and remains stable) at 300/400 kb/s !! 

I tried this different times, and I wander why... I was thinking that the integrated wifi was not so powerful, but this destroys all my previous thoughts...

Can it depend on the protocol used ?!

Or maybe some sort of speed limit set on a single connection ? (bittorrent uses different connections at the same time...)

It can't be just a matter of luck...

EDIT: the bittorrent client is Transmission

EDIT: googling "ftp http slower bittorent" I found A LOT of people having the same problem on DIFFERENT systems !! Seems like some values required optimization in their case...

EDIT: the problem seems the MTU value

EDIT: and reading on the wiki I found something interesting... the "Destination Unreachable" error !! The same thing that keeps my Pandora disconnecting from the router when the PC is using the wifi !!!  

 

[EssoAir]

Torrent is a different protocol. Not really comparable to FTP or HTTP

 

[dreamer]

<rediculous statement>

Ever heard of the concept of 'bandwidth' ?

 

[Linux-SWAT]

Sandwich ?

 

[PowerGod]

Playing with the MTU value changes nothing... and I need to postpone my trials... anyway there must be something in these parameters... THERE MUST BE !! :angry:

 

[Yoyobuae]

Maybe it's due to TCP:

http://bradhedlund.com/2008/12/19/how-to-calculate-tcp-throughput-for-long-distance-links/

What's the default TCP window size setting on Pandora? You can run these:

$ cat /proc/sys/net/ipv4/tcp_rmem 
4096    87380   6291456
$ cat /proc/sys/net/ipv4/tcp_wmem
4096    16384   4194304
$ cat /proc/sys/net/ipv4/tcp_window_scaling
1

This what I get on my PC runing Fedora.

 

[kojack]

Maybe it's due to TCP:

http://bradhedlund.com/2008/12/19/how-to-calculate-tcp-throughput-for-long-distance-links/


What's the default TCP window size setting on Pandora? You can run these:


$ cat /proc/sys/net/ipv4/tcp_rmem
4096 87380 6291456
$ cat /proc/sys/net/ipv4/tcp_wmem
4096 16384 4194304
$ cat /proc/sys/net/ipv4/tcp_window_scaling
1

This what I get on my PC runing Fedora.

rmem:

4096  87380  944768

wmem:

4096  16384  944768

scaling:

1

 

[Yoyobuae]

Maybe try to temporarilly increase those values (ie. double them) like so:

sudo sysctl -w "net.ipv4.tcp_rmem=4096 87380 1889536"
sudo sysctl -w "net.ipv4.tcp_wmem=4096 16384 1889536"And check if download speeds improve.
If it does help then make the change permanently by adding them to /etc/sysctl.conf:

net.ipv4.tcp_rmem = 4096 87380 1889536
net.ipv4.tcp_wmem = 4096 16384 1889536It's weird though, I get no performance degradation on my desktop PC when I lower those values. Only when lower them down to extremely low values (ie. net.ipv4.tcp_rmem=4096 4096 4096) there is an effect on download speed (down to 120 KB/s from 300 KB/s).

Maybe there's something else going on? I wonder if it affects TCP only or if UDP is also affected. Can someone try fetching some file using TFTP? (probably would need to run an TFTP server to download from to do the test)

 

[freamon]

Can it depend on the protocol used ?!

Or maybe some sort of speed limit set on a single connection ? (bittorrent uses different connections at the same time...)

Bittorrent works on top of http, so I would guess it's multiple connections of 60 Kb/s that get you the better speed.

 

[Yoyobuae]

Which should not be the case. A single TCP connection should be able to max out the bandwidth, unless there's something wrong at the protocol level or the server is limiting download speed.

 

[F_Slim]

I noticed that downloading with PNDManager is pretty fast on my Pandora ...

 

[Neelix]

I noticed that downloading with PNDManager is pretty fast on my Pandora ...

I've noticed that my PNDManager download speed tends to max out at ~ 176KB/s per file. Multiple concurrent downloads can individually reach this limit until my actual bandwidth is maxed out.

- Neelix

 

[PowerGod]

Yesterday a friend of mine asked me to try "arp -a", and so, in my ignorance I tried... the first thing I saw was that in Windows the arp table was perfectly pointing at the access point, while the Pandora arp table was EMPTY !!

Now, I tried to add manually the mac/ip of the access point, to the Pandora arp table... then I started utorrent on my PC and Transmission on the Pandora both connected on the wifi...

After an hour them are both downloading fullspeed (the Pandora seems a little faster) and the Pandora is STILL CONNECTED TO THE NETWORK !! 

I have still to look at the http download speed issue, but I think this is a great achievement for now !!

But WHY the arp table is empty ? What does it fill the table on Windows ?

 

[Neelix]

But WHY the arp table is empty ? What does it fill the table on Windows ?

Probably because you hadn't communicated with any other network device since booting the pandora when you first checked it. To quote the man page arp "displays the kernel's IPv4 network neighbour cache."

I just tried this on my pandora, it only had a listing for my netbook. Then I pinged the router, then I ran arp again and the router address showed up in the table.

- Neelix

 

[PowerGod]

@Neelix: you are right

Anyway, after a while the bandwidth reached 0 so I tried to see the arp table and here what I got


? (192.168.0.1) at <incomplete> on wlan0


seems like the MAC of the access point is lost... but the strange thing is that it was permanent cause I manually added it...

EDIT: I tried re-adding it manually, but seems like it can't even ping the access point after that... and I mean that the ping IS NOT SENT !!


PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data.

and then nothing...

EDIT: no, wait, if I stop the ping I get a number of packets transmitted but 0 received...

 

[Neelix]

That doesn't mean its not sent, just that there are no replies.

- Neelix

 

[PowerGod]

Is there something else I can try to find a solution ? 

EDIT: I deleted the access point entry in arp table, then tried to ping it, and it was added to the table WITH the MAC address !! But the ping returns "Destination host unreachable"

 

[Neelix]

Your attempt to manually change it probably messed with the routing table in some way, I'd recommend disconnecting and reconnecting to the network to correct the problem.

As for other solutions, I'm afraid I don't have an answer for that one.

- Neelix

 

[PowerGod]

I hope to find a real fix one day... cause disconnecting and reconnecting works only for a matter of minutes and then all the comunication problems starts again...

 

[notaz]

Do you have the latest firmware? Problems like that were widespread during transition to 3.2 kernel (SuperZaxxon beta) due to some missing code, after that was merged it was resolved for most users.