Fix Harry's wifi
Contents
- 1 Background
- 2 Tools
- 3 Details
- 3.1 Android Wifi Analyzer for signal strength
- 3.2 Identify protocol
- 3.3 see what dhcp is giving us
- 3.4 what does the routing table look like?
- 3.5 measure ping time and packet loss to default gateway with mtr
- 3.6 use firebug net to measure stages of web page load
- 3.7 how many hops to DNS?
- 3.8 how fast is DNS?
- 3.9 measure bandwidth with curl
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.
Tools
- Netalyzr http://netalyzr.icsi.berkeley.edu/
- Ntop http://www.linuxforu.com/2010/10/ntop-network-diagnostics-tool/
Details
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
use firebug net to measure stages of web page load
- DNS lookup
- Connecting
- Sending
- Waiting
- Receiving
At home on wired network visiting finninday.net Main_page:
| DNS | Connecting | Sending | Waiting | Receiving |
|---|---|---|---|---|
| 35ms | 0 | 0 | 228ms | 56ms |
how many hops to DNS?
root@ferret:~# mtr --report 8.8.8.8 Start: Tue Feb 4 18:09:22 2014 HOST: ferret Loss% Snt Last Avg Best Wrst StDev 1.|-- weasel.local 0.0% 10 0.1 0.1 0.1 0.2 0.0 2.|-- ??? 100.0 10 0.0 0.0 0.0 0.0 0.0 3.|-- xe-0-0-3-sur03.troutdale. 0.0% 10 8.1 8.0 4.9 13.7 2.2 4.|-- ae-53-0-ar03.beaverton.or 0.0% 10 9.2 18.3 7.6 69.6 20.3 5.|-- ae-1-0-ar03.troutdale.or. 0.0% 10 7.5 13.7 7.5 43.6 11.6 6.|-- he-2-0-0-0-11-cr01.seattl 0.0% 10 13.3 13.7 11.6 15.2 1.1 7.|-- be-10-pe03.seattle.wa.ibo 0.0% 10 15.1 13.1 12.0 15.1 0.7 8.|-- as15169-1-c.seattle.wa.ib 0.0% 10 17.8 13.7 12.1 17.8 1.7 9.|-- 209.85.249.32 0.0% 10 11.6 12.0 10.9 13.1 0.3 10.|-- 66.249.94.199 0.0% 10 12.6 13.1 11.9 15.4 1.1 11.|-- 216.239.46.200 0.0% 10 20.0 19.5 18.4 21.6 0.8 12.|-- 216.239.48.167 0.0% 10 20.7 19.4 15.1 22.8 1.9 13.|-- ??? 100.0 10 0.0 0.0 0.0 0.0 0.0 14.|-- google-public-dns-a.googl 0.0% 10 19.1 19.5 15.9 22.7 1.9
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
