CSBNET: FAQ

Frequently Asked Questions (with answers) for CSBNET - Chalmers Studentbostäder's Internet network - operated by BrainMill.

If you have problems with Internet in your home and the below steps and tips don't help, please contact BrainMill support via https://support.csbnet.se.

FAQ

• But I don't get anywhere near 1000/1000 Mbps today?
  1. The reason is either due to a limitation of your router, or the method in which you are testing the connection speed. For speed testing ideally you should connect a network cable from your computer directly into the apartment’s network port (bypassing the router). Second best is to connect it to one of your routers LAN ports.
  2. The 1000/1000 Mbps relates to the Ethernet link bandwidth between the network switch connected to the other side of your apartment’s network port, and your device. It is not very meaningful to try to measure the speed of the Ethernet port, using WiFi (see the slow WiFi question for more details.)
  3. Often when tenants contact us about only getting for example 90-95 Mbps, even when using a network cable to perform the test, it is commonly because the tenant's router claims a higher WiFi speed (for example 1300 Mbps), while it actually only has a 100 Mbps WAN (upstream/Internet) network port. The 1300 Mbps here is unfortunately "sales math", referring to the sum of the maximum WiFi bandwidth potentially possible for the device to communicate with - but only to/from clients connected directly to it. If your router only has a 100Mbps WAN port, then you will have to buy a new router with 1000Mbps WAN capabilities to reach speeds over 100Mbps, commonly known as gigabit routers.
  4. Other times, tenants can measure perhaps 300-500 Mbps using a network cable, and it turns out that is actually the maximum performance the router is capable of delivering. There have been rare cases where activating a performance/turbo feature in the router has improved this. The speed is also dependent on the client that you're testing on, so make sure to close background programs and use an incognito window in your browser to ensure that extensions aren’t slowing down the client.
  5. Because of the 1000 / 1000 Mbps definition applying to the Ethernet layer (Layer 2) in the network stack - maximum available bandwidth for eg. TCP payload is around 950 Mbps. A test performance above 850 Mbps is very good. Sometimes test servers or the path between the test servers and CSBNET can be congested, which reduces the speed. Also, the network distance (round trip time) between your computer and the test server can impact the measured performance due to the way congestion control algorithms work. We have a on-net iPerf3 server available for testing at iperf.csbnet.se, standard ports. This server is currently connected using only 1000/1000 Mbps itself, so congestion is possible. Wait a bit and test again if the results are bad.
• Why is my Internet (using WiFi) really slow and bad?
  1. 90% of cases tenants have with slow Internet are due to issues with the WiFi, which in turn are nearly always issues fundamentally due to the fact that the WiFi signals travels through a shared medium - e.g air/space.
  2. Tuning WiFi is complex, but an educated guess is that:
     1. You experience "co-channel interference", meaning other WiFi routers/APs (can be other radio transmitters too, both 2.4 GHz and 5 GHz are unlicensed spectra. We have seen wireless TV extenders, etc, cause interference.) - are "talking over" your router & device. Potential fix: Pick a different (and perhaps more narrow) channel on your WiFi router/AP. The 5Ghz band is also generally less congested and will provide more consistent speeds.
     2. Your router is old and uses a spectrally inefficient communication mode. Today, WiFi 6 (also known as 802.11ax) offers best chance of working WiFi due to its OFDMA (Orthogonal Feature Division Multiple-Access) feature. Basically, the newer the WiFi standard the more bits per airtime-frequency unit can fit, giving more room for more information in the air. OFDMA allows the interaction between WiFi router/AP and client to reserve mere fractions of the airtime, sufficient to send tiny but frequent amounts of data which is very common.
     3. Your neighbours' routers are configured to transmit with too much power.
  3. Unfortunately, there is not very much we can do to fix this other than supplying information, or providing the WiFi routers/access points in each apartment (something we do in all newly built apartments). The reason this helps is because it ensures:
     1. The WiFi access point is of an up-to-date standard,
     2. The radio channel choices can be managed to reduce co-channel interference,
     3. The transmission power can be managed to not leak too far outside the apartment.