Fix Harry's wifi
Background
A friend suffers from crappy wifi. I keep telling him that I'll fix it, but I haven't yet. We spend time talking or eating instead of poking at the wifi. Before I go over again, I want to have a streamlined process for diagnosing the problem with all the necessary tools pre-loaded on my laptop so I can look like a rock star.
So I'm practicing on our wifi and trying to make sure I've got all my tools together. These procedures assume that I have access to an Android phone and a linux laptop both on the wifi network of interest.
Android Wifi Analyzer for signal strength
At home I get a maximum signal of about -50 db from Portlandia when the phone is less than 5 feet from it. I get about -75 db from ahub which is one floor down from the phone.
Identify protocol
Standard android wifi settings page tells me link speed, security type, and IP.
- Portlandia: 54Mbps (802.11g)
- ahub: 36Mbps (mixed 802.11b+g)
Other possibilities are:
- 802.11n (2009) up to 150Mbps
- 802.11ac (2012) up to 866Mbps
see what dhcp is giving us
root@ferret:~# less /var/lib/dhcp/dhclient.leases
lease {
interface "eth0";
fixed-address 10.0.0.6;
option subnet-mask 255.0.0.0;
option routers 10.0.0.3;
option dhcp-lease-time 43200;
option dhcp-message-type 5;
option domain-name-servers 8.8.8.8,8.8.4.4;
option dhcp-server-identifier 10.0.0.3;
option domain-name "finninday.net";
renew 0 2013/11/24 04:12:33;
rebind 0 2013/11/24 08:53:29;
expire 0 2013/11/24 10:23:29;
}
what does the routing table look like?
root@ferret:~# ip route list default via 10.0.0.3 dev eth0 proto static 10.0.0.0/8 dev eth0 proto kernel scope link src 10.0.0.6 metric 1 root@ferret:~# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 10.0.0.3 0.0.0.0 UG 0 0 0 eth0 10.0.0.0 0.0.0.0 255.0.0.0 U 1 0 0 eth0
measure ping time and packet loss to default gateway with mtr
- on a wired network ping time is between 0.2 and 0.4ms
- across portlandia ping time between a desktop and a tablet is between 1.9 and 99ms. Average is 57ms.
- there is no measurable packet loss
how many hops to DNS?
how fast is DNS?
I can expect a response in 20 to 35 ms.
root@ferret:~# dig finninday.net ; <<>> DiG 9.9.3-rpz2+rl.13214.22-P2-Ubuntu-1:9.9.3.dfsg.P2-4ubuntu1.1 <<>> finninday.net ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 28458 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 512 ;; QUESTION SECTION: ;finninday.net. IN A ;; ANSWER SECTION: finninday.net. 217 IN A 216.99.216.99 ;; Query time: 20 msec ;; SERVER: 8.8.8.8#53(8.8.8.8) ;; WHEN: Tue Feb 04 18:07:56 PST 2014 ;; MSG SIZE rcvd: 58
measure bandwidth with curl
The curl manual says the speed is measured in bytes per second.
Over a wired link, I get this:
root@ferret:~# curl -o /dev/null http://speedtest.wdc01.softlayer.com/downloads/test500.zip
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
20 500M 20 103M 0 0 5683k 0 0:01:30 0:00:18 0:01:12 6896k^C
Over Portlandia, I get about 2MBps out of a theoretical max of 6.75MBps:
[rday@servo lf]$ curl -o /dev/null http://speedtest.wdc01.softlayer.com/downloads/test500.zip
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
7 500M 7 38.2M 0 0 1595k 0 0:05:20 0:00:24 0:04:56 1936k^C
Over ahub, I get about 2.6MBps out of a theoretical max of 4.5 to 6.75MBps:
[rday@servo lf]$ curl -o /dev/null http://speedtest.wdc01.softlayer.com/downloads/test500.zip
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
11 500M 11 56.3M 0 0 2397k 0 0:03:33 0:00:24 0:03:09 2632k^C