With remote access to College suddenly being thrust to the fore during the current Covid-19 pandemic and now becoming an essential service rather than a 'nice to have' option, here are some tips on troubleshooting common problems and getting the most from your connection.
If trailing Ethernet cables all around the house doesn't appeal, you could use powerline networking or better still, consider installing a permanent wired network. If you're good at DIY or if your home is currently being renovated or rewired, now is a good time to do this (or have this done for you). It's no more difficult than electrical rewiring and need not cost a lot to put a double network socket into each room cabled back to a network switch or even a patchpanel with cat 6-grade cable, with possibly more outlets in rooms used as an office or containing audio-visual equipment, home cinemas, etc. And if you're an AV fan, the network could be used to distribute audio and video all around the house, into garden buildings, etc opening up all sorts of interesting possibilities.
Probably the best way to see what's going on with the wi-fi networks in your current location and which channels are being used is to use a wi-fi network analyser app on a smartphone. Many of these can be downloaded for free and some offer added features for a small extra payment. On the left is a screenshot from the 'channel radar' feature of WiFi Overview 360 Pro for Android which shows graphically which channels are in use along with their signal strengths. As you can see, channels 1 & 6 have quite a few networks using them whereas the networks with names beginning with 'Lausanne22' have had their channels changed manually to space them out onto unused channels. However, there are only 13 channels available in the 2.4 GHz band (and only 11 if your router or wi-fi access point is intended for a region other than Europe, such as the US) so it can get very congested.
On the 2.4 GHz band ideally there should be 4 unused channels between every channel that is in use, for the best results. This means using channels 1, 6 and 11, or 2, 7 and 12, and so on and also means the band's channel capacity is effectively only 3 channels.
In the same building, on the right is a screenshot showing only one channel on the 5 GHz band is in use leaving many free ones. If your devices support 5 GHz operation then use this band although older laptops and some devices such as home security cameras and remote controllable cat flaps (yes, really) are only designed to be used on 2.4 GHz wi-fi networks. Using the same 4 channel spacing rule as for the 2.4 GHz band, the total channel capacity of the 5 GHz band is 43 channels.
5 GHz wi-fi offers faster data speeds but a downside is a shorter wi-fi range and since it uses a shorter wavelength radio signal, there are more objects around in the average home that may block the signal.
While many routers have an 'auto' setting which claims the router will detect channel usage in its vicinity and select the best available channel, this rarely works and it is best to manually select a quiet channel based on what you find using a wi-fi network analyser. You can do this through the router's control panel accessible through a web browser using either a wi-fi connection or a wired link.
You should be able to remain connected to a remote system via ssh for months on end even without resorting to keep-alives and you certainly can with BT and Zen Internet connections but some ISPs (TalkTalk, for example) randomly disconnect and then reconnect the broadband service every few days. Some ssh connections will survive the disconnection and resume afterwards but others will end with a depressing message similar to this one:
Fssh_packet_write_wait: Connection to 126.96.36.199 port 22: Broken pipe
Generally, all of the well-known internet server providers (ISP's) provide a service usable with Imperial College online services but there are significant differences in cost, reliability and in the consistency of upload/download speeds.
For heavy usage or extensive remote working you might want to consider a business broadband connection. These don't cost much more than a domestic residential connection but do have some advantages that may be important to you; line faults and roadside cabinet faults get fixed on the same day they are reported or by the next business day, there is much less network bandwidth contention with other users, one or more static IP addresses are available and nearly all TCP ports are open and usable (port 139 used by Windows for SMB network discovery is almost always blocked on business connections to protect customers from themselves!). With most ports open you can run mailservers, webservers and all sorts of things which are always blocked or prohibited on residential connections.
Here are some sample screenshots of broadband speed test results; these were all taken within a few seconds of each other on a PC that could be switched quickly between connections to both TalkTalk and Zen Internet FTTC (Fibre To The Cabinet, also known as VDSL, fibre or SuperFast) services and VirginMedia's Voom 500 cable broadband service.
As you can see, TalkTalk is not providing the connectivity speeds you'd expect from a VDSL/FFTC connection (~76 Mbit/s download, ~18 Mbit/s upload) at this time although this connection has reached these figures at other times.
On the other hand, the Zen Internet connection consistently meets the stated download/upload speeds at all times together with high reliability. All Zen Internet connections give you a static IP address which is useful if you want to connect to devices within your home from outside such as security cameras or if you are running publicly acessible gaming and web servers at home.
If you live in an area served by Virgin Media cable, very fast download speeds of around 550 Mbit/s (just over half of what you would expect from a standard college Ethernet gigabit network connection) are possible on a business broadband connection with up to 300 Mbit/s available on residential services although long-term reliability of the connection is not quite as good as BT or Zen Internet.
For all three of the above connections the ISP's supplied routers were not used (in the case of the Virgin Media connection, the supplied Hitron cable modem/router was retained but configured as a modem-only feeding into a separate router) and DrayTek 2860 series routers were used instead which does make a big difference to performance and reliability. Despite their quaint retro 1980's look and beige casings (see right), they offer a vast range of features (the English language version user manual alone runs to almost 1000 pages) with a high network throughput - highly recommended and doubly so if you are a network geek!
Research Computing Manager, Department of Mathematics
last updated: 25.9.2020