Internet outages are more common than most people think, and may be caused by misconfigurations, power outages, extreme weather, or infrastructure damage. Note that such outages are distinct from state-imposed shutdowns that also happen all too frequently, generally used to deal with situations of unrest, elections or even exams.
On the morning of January 4, 2022, citizens of The Gambia woke up to a country-wide Internet outage. Gamtel (the main state-owned telecommunications company of the West Africa country), announced that it happened due to “technical issues on the backup links” — we elaborate more on this below.
Cloudflare Radar shows that the outage had a significant impact on Internet traffic in the country and started after 01:00 UTC (which is the same local time), lasting until ~09:45 — a disruption of over 8 hours.
Looking at BGP (Border Gateway Protocol) updates from Gambian ASNs around the time of the outage, we see a clear spike at 01:10 UTC. These update messages are BGP signaling that the Gambian ASNs are no longer routable.
It is important to know that BGP is a mechanism to exchange routing information between autonomous systems (networks) on the Internet. The routers that make the Internet work have huge, constantly updated lists of the possible routes that can be used to deliver every network packet to their final destinations. Without BGP, the Internet routers wouldn’t know what to do, and the Internet wouldn’t work. As we saw in our blog post in 2021 about how Facebook disappeared from the Internet, the Internet is literally a network of networks, and it’s bound together by BGP.
The Gambia’s Internet access is solely dependent on a single provider, Gamtel. Because The Gambia’s international Internet connectivity via the ACE submarine cable was unavailable, it was reliant on the “backup links” referenced above – terrestrial connectivity via Senegal and the provider Sonatel. This is visible in BGP data. If we look at the ASNs that are allocated to networks in The Gambia (AS25250, AS37309, AS37503, AS37552, AS37524, AS37323, AS328488, AS328140), and put those into a regular expression on BGP routing tools like route-views as so:
route-views>show ip bgp regexp .*_(25250|37309|37503|37552|37524|37323|328488|328140)
We are able to see all the possible upstream ASN paths from these networks to the rest of the Internet.
Looking at the “Path” results, we see that AS8346 (Sonatel) and AS25250 (Gamtel) are in the path for all the Gambian networks.
Visualized, you can see the dependency on this network path for The Gambia’s Internet access.
No interruptions were seen in Sonatel (AS8346), so this indicates that the single network path between Sonatel and Gamtel (AS25250) is a critical point for connectivity. A failure in either of these networks could result in The Gambia going offline again.
Yesterday’s outage in The Gambia outage illustrates something we frequently reference here in the blog: the Internet is literally a network of networks. A significant amount of Internet traffic is carried by a complex network of undersea fiber-optic cables that connect countries and continents — all the cable systems used have landing points in two or more countries. So a problem in one country can easily affect others.
Going back to The Gambia, Gamtel explained in a January 5, 2022, press release that there was “a primary link failure at ACE” — the cable system that serves 24 countries, from Europe to Africa. “The ACE cable repair is expected to be completed in mid-January, 2022,” explained the company.
The “backup failure” here was “due to a faulty card at Toubakota, in Senegal”. That problem affects “both the Karang and Seleti links [points of cable connections from Senegal to The Gambia] as both North and South links converges there”. “Thus, the reason for the complete isolation on the Sonatel link”, concludes Gamtel.
Recognizing the critical importance of reliable Internet connectivity, The Gambia Public Utilities Regulatory Authority also issued a statement noting “The Authority, operators, MOICI, and the Government are exploring other options of making sure that the Gambia has a second fibre cable backup considering the impact that these failures are having on our national security, economy, and social activities.”