Wireless
Motivation
The UW wireless network has a couple of major deficiencies:
- Weak signal in MC 3036, preventing some laptops from connecting
- Aggressive throttling of bandwidth, even to wired systems within the club office
- Ignorance of the "Don't Count" list
The second point is quite important: UW's wireless will begin to throttle high bandwidth connections after a minute or two, decreasing bandwidth slowly from 1MB/s or more down to 40KB/s or less. Members can expect to sit in the office for an hour or more if they want to download many packages off of the CSC mirror.
To work around this problem we have an access point in the Computer Science Club.
Configuration
- ESSID: csc-wireless
- AP: 00:11:95:ff:da:ec
- Channel: 36 (5.18 GHz)
- Network: auth3net (129.96.192.0/23)
Clients must authenticate to the Network Authentication Appliance (NAA) as with uw-wireless, in accordance with this IST policy, points #2 through #4.
Technical Overview
The AP connects to acesulfame-potassium through a secondary NIC. On acesulfame-potassium, the following decision is made:
- IP packets destined for mathstudentorgsnet are brouted with SNAT to wireless-nat.csclub.uwaterloo.ca
- All other ethernet frames are bridged to auth3net
The network is identical to connection through uw-wireless in all respects, except for the special treatment of mathstudentorgs traffic. This special treatment bypasses uw-wireless throttling for machines on our network.
Wireless Performance
- uw-wireless
- 400MB Ubuntu CD image
- Initial speed: 2.13MB/s
- Final speed: 19.9KB/s
- Time: finished in 1h 41m, ETA increased for first half.
mike@freyr:/tmp/test$ wget http://mirror.cs.uwaterloo.ca/ubuntu-releases/dapper/ubuntu-6.06.2-server-sparc.iso --2008-04-22 15:56:53-- http://mirror.cs.uwaterloo.ca/ubuntu-releases/dapper/ubuntu-6.06.2-server-sparc.iso Resolving mirror.cs.uwaterloo.ca... 129.97.152.77 Connecting to mirror.cs.uwaterloo.ca|129.97.152.77|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 412856320 (394M) [text/plain] Saving to: `ubuntu-6.06.2-server-sparc.iso'
0% [ ] 942,080 2.13M/s 1% [ ] 5,607,872 2.19M/s 4% [> ] 19,587,072 1.97M/s eta 3m 3s 8% [==> ] 33,109,664 2.24M/s eta 2m 51s 12% [===> ] 50,850,640 2.19M/s eta 2m 42s 16% [=====> ] 69,363,112 2.22M/s eta 2m 32s 23% [========> ] 98,991,832 2.25M/s eta 2m 18s 36% [=============> ] 148,809,128 2.25M/s eta 1m 56s 38% [==============> ] 157,883,088 140K/s eta 2m 2s 38% [==============> ] 160,275,112 140K/s eta 2m 26s 41% [===============> ] 170,110,968 117K/s eta 3m 58s 42% [===============> ] 175,448,880 101K/s eta 4m 50s 43% [================> ] 180,703,184 99.7K/s eta 5m 44s 43% [================> ] 181,581,296 88.5K/s eta 5m 52s 44% [================> ] 184,742,376 77.8K/s eta 6m 26s 48% [==================> ] 200,324,016 57.6K/s eta 9m 34s 50% [===================> ] 208,982,344 46.3K/s eta 11m 27s 50% [===================> ] 209,633,064 46.2K/s eta 11m 37s 52% [====================> ] 216,817,944 25.9K/s eta 13m 39s 53% [====================> ] 218,983,984 58.8K/s eta 14m 6s 54% [====================> ] 224,401,792 28.9K/s eta 15m 20s 55% [=====================> ] 227,171,400 27.4K/s eta 15m 56s 56% [=====================> ] 232,991,392 28.8K/s eta 17m 2s 56% [=====================> ] 233,810,808 36.9K/s eta 17m 10s 57% [=====================> ] 236,375,144 37.0K/s eta 17m 35s 58% [======================> ] 241,916,248 54.0K/s eta 18m 22s 60% [=======================> ] 247,920,448 37.2K/s eta 19m 2s 64% [========================> ] 265,272,456 37.3K/s eta 20m 8s 65% [=========================> ] 269,241,248 37.3K/s eta 20m 14s 67% [=========================> ] 278,040,112 37.4K/s eta 20m 15s 68% [==========================> ] 281,901,936 37.4K/s eta 20m 11s 69% [==========================> ] 287,954,592 29.1K/s eta 19m 59s 72% [============================> ] 300,107,216 25.1K/s eta 19m 19s 73% [============================> ] 302,555,672 36.6K/s eta 19m 8s 77% [=============================> ] 319,476,656 54.3K/s eta 17m 30s 77% [==============================> ] 320,267,688 37.8K/s eta 17m 24s 78% [==============================> ] 322,482,128 36.8K/s eta 17m 9s 78% [==============================> ] 323,057,312 23.9K/s eta 17m 5s 80% [===============================> ] 332,393,496 37.0K/s eta 15m 52s 81% [===============================> ] 338,212,672 37.1K/s eta 15m 2s 82% [================================> ] 341,035,936 36.7K/s eta 14m 36s 84% [================================> ] 346,986,264 31.9K/s eta 13m 40s 89% [==================================> ] 368,645,832 38.0K/s eta 9m 47s 91% [===================================> ] 378,088,272 42.9K/s eta 7m 53s 96% [=====================================> ] 398,174,800 37.5K/s eta 3m 29s 99% [======================================> ] 411,232,768 37.5K/s eta 24s 100%[=======================================>] 412,856,320 19.9K/s in 1h 41m 2008-04-22 17:37:55 (66.5 KB/s) - `ubuntu-6.06.2-server-sparc.iso' saved [412856320/412856320]
- csc-wireless
- 700MB Ubuntu CD image
- Initial speed: 2.12MB/s
- Final speed: 2.43MB/s
- Time: finished in 3m 31s
mike@freyr:/tmp/test$ wget http://mirror.csclub.uwaterloo.ca/ubuntu-releases/hardy/ubuntu-8.04-beta-server-i386.iso --2008-04-17 05:34:44-- http://mirror.csclub.uwaterloo.ca/ubuntu-releases/hardy/ubuntu-8.04-beta-server-i386.iso Resolving mirror.csclub.uwaterloo.ca... 129.97.134.71 Connecting to mirror.csclub.uwaterloo.ca|129.97.134.71|:80... connected. HTTP request sent, awaiting response... 302 Found Location: http://taurine.csclub.uwaterloo.ca/iso/ubuntu-8.04-beta-server-i386.iso [following] --2008-04-17 05:34:44-- http://taurine.csclub.uwaterloo.ca/iso/ubuntu-8.04-beta-server-i386.iso Resolving taurine.csclub.uwaterloo.ca... 129.97.134.34 Connecting to taurine.csclub.uwaterloo.ca|129.97.134.34|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 526323712 (502M) [application/x-iso9660-image] Saving to: `ubuntu-8.04-beta-server-i386.iso' 2% [ ] 10,988,599 2.12M/s eta 4m 36s 4% [> ] 21,247,679 2.43M/s eta 3m 58s 6% [=> ] 31,897,719 2.41M/s eta 3m 41s 16% [=====> ] 85,867,575 2.40M/s eta 3m 2s 27% [=========> ] 143,900,519 2.36M/s eta 2m 38s 38% [==============> ] 203,245,351 2.36M/s eta 2m 11s 43% [================> ] 228,489,783 2.43M/s eta 2m 2s 51% [===================> ] 269,462,391 2.41M/s eta 1m 45s 58% [======================> ] 309,395,335 2.48M/s eta 88s 67% [=========================> ] 354,638,095 2.41M/s eta 70s 78% [==============================> ] 410,898,984 2.41M/s eta 47s 84% [================================> ] 444,207,328 2.42M/s eta 33s 94% [====================================> ] 498,937,384 2.39M/s eta 12s 97% [======================================> ] 514,212,336 2.39M/s eta 5s 99% [======================================> ] 524,255,664 2.43M/s eta 1s 100%[=======================================>] 526,323,712 2.43M/s in 3m 31s 2008-04-17 05:38:15 (2.38 MB/s) - `ubuntu-8.04-beta-server-i386.iso' saved [526323712/526323712]
These tests are sloppily done, to be sure, but still demonstrate the huge performance advantage of csc-wireless. I will repeat them without aborting, when I have time.
Detailed Configuration
Required Packages
To install required packages, type:
sudo aptitude install madwifi-source madwifi-tools wireless-tools vlan bridge-utils ebtables iptables iproute
Then build the modules for the installed kernel via:
sudo m-a a-i madwifi
Wireless Interface Configuration
First, load the Atheros and 802.11q modules:
modprobe ath_pci 8021q
These need to be loaded early in the boot, so add them to /etc/modules:
ath_pci 8021q
Next, configure the wireless interface. Use the following snippet:
auto ath0
iface ath0 inet manual
pre-up wlanconfig ath0 destroy || true
pre-up wlanconfig ath0 create wlandev wifi0 wlanmode ap
post-down wlanconfig ath0 destroy
wireless-mode master
wireless-channel 36
wireless-essid csc-wireless
Finally, make a bridge between the wireless and auth3net. Use the following snippet, replacing IFACE by the interface connected to auth3net
auto br192
iface br192 inet manual
bridge_ports IFACE ath0
bridge_stp yes
up brctl setbridgeprio br192 40000
up ip route add 129.97.192.0/23 dev br192
Brouting Configuration
Additional setup is needed to enable fast communication between mathstudentorgsnet and auth3net. We take the minimally invasive approach of pulling packets destined for mathstudentorgsnet off the bridge and routing them, masquerading as wireless-nat.csclub.uwaterloo.ca. Masquerading is needed to ensure responses are routed correctly.
First, add 129.97.134.85 as a secondary IP address. You might do so by adding this snippet, replacing IFACE by the interface connected to mathstudentorgsnet:
auto IFACE:nat
iface IFACE:nat inet static
address 129.97.134.85
netmask 255.255.255.0
network 129.97.134.0
Second, enable routing, by typing the following:
echo 1 >> /proc/sys/net/ipv4/ip_forward
To make this permanent, add the following snippet to sysctl.conf:
net.ipv4.ip_forward=1
Third, configure ebtables to pull packets off the bridge. Type:
ebtables -t broute --flush
ebtables -t broute -A BROUTING -i ath0 \
-p ipv4 --ip-src 129.97.192.0/23 --ip-dst 129.97.134.0/24 \
-j redirect --redirect-target DROP
invoke-rc.d ebtables save
Finally, configure iptables to masquerade wireless users as wireless-nat.csclub. Type the following, replacing IFACE by the interface connected to mathstudentorgsnet:
iptables -t nat --flush
iptables -t nat -A POSTROUTING -o IFACE \
-s 129.97.192.0/23 -d 129.97.134.0/24 \
-j SNAT --to-source 129.97.134.85
invoke-rc.d iptables save
Ensure the appropriate routing table entry for auth3net exists--masquerading will not work without it. It is included in the bridge configuration snippet above.