Published: Sun 04 September 2016
By Javier Ruere
In play .
tags: networking mesh linux
Introduction
Needing to transfer a lot of data between two computers, I find the perfect excuse to mess with the network.
Unfortunately, my ethernet cable is broken so wireless it will be.
Transfering file through the router has a rate of 1MB/s. I'm disgusted by this. To improve it, I'll try an adhoc network between the machines.
This article will be very similar and is based on my previous B.A.T.M.A.N. articles.
Components
Custom built PC with a Qualcomm Atheros AR9300 WiFi and a current Arch Linux.
Acer Aspire E15 (E5-521-84UV) laptop with a Broadcom BCM43142 WiFi card and a current Arch Linux.
A current Arch has the 4.7.2 kernel.
Objectives
Setup a direct connexion.
Transfer files faster than through the router.
Configuration of an Ad-Hoc Connection
Since the machines are so similar, the instructions work almost verbatim with the exception of the device name.
$ sudo iw dev wlan0 set type ibss
$ sudo ip link set up dev wlan0
$ sudo iw dev wlan0 ibss join openadhoc 2472
$ iw dev wlan0 info
Interface wlan0
ifindex 3
wdev 0x1
addr 90:f6:52:17:92:06
ssid openadhoc
type IBSS
wiphy 0
channel 5 (2432 MHz), width: 20 MHz (no HT), center1: 2432 MHz
This sets both devices to the same channel as peers. Surprisingly, to channel 1 when I asked for channel 13.
ping works immediatelly! :D
A iw dev wlan0 station dump shows that a connection is established:
Station d0:53:49:c0:05:6a (on wlan0)
inactive time: 66 ms
rx bytes: 85589
rx packets: 1048
tx bytes: 0
tx packets: 0
tx retries: 0
tx failed: 0
rx drop misc: 0
signal: -40 [-51, -40, -55] dBm
signal avg: -37 [-55, -37, -48] dBm
tx bitrate: 1.0 MBit/s
rx bitrate: 6.0 MBit/s
authorized: yes
authenticated: yes
associated: yes
preamble: long
WMM/WME: yes
MFP: no
TDLS peer: no
DTIM period: 0
beacon interval:100
connected time: 228 seconds
Suprisingly, on the laptop (Broadcom), the station dump is empty.
The IP is provided by the IPv6 autoconfiguration and there's name resolution through Zeroconf.
There are two strange things. The first one is that the ping takes a second or two to begin.
The second is that the RTT is around a ms (rtt min/avg/max/mdev = 0.999/1.855/9.690/2.092 ms).
Unfortunately, SSH does not. I suppose it doesn't bind to link scoped addresses.
To autoconfigure an IP address, I used sudo avahi-autoipd -D wlan0.
Transfering files
With rsync, I get ~1MB/s. A little dissapointed but I'm sure it can be improved.
Lets try Deluge: 1.5MB/s. A definite improvement but I'm not satisfied.
Lets mess with the NICs. Lets change retry to 2 and disable power save.
Now rsync does ~1.8MB/s. That's a nice improvement but still dissapointing.
Deluge, on the other hand, is doing 5MB/s. This is great!
I mean, it's pathetic but for WiFi 11n HT20 (Broadcom), it's pretty good.
I guess I'll disable power save on my laptop!