CTL Blog

Why Did I Have Problems Accessing CoursePlus on Saturday Morning?

April 03, 2021 | 1 Minute Read

Although we know websites by names like amazon.com or Spotify or jhu.edu, that's not how your computer or phone actually reaches those websites. Computers, phones, and all internet-connected devices find one another through a series of numbers, known as an IP (Internet Protocol) address. It's a lot easier to remember amazon.com than it is to remember As such, nearly all internet-connected devices use a system known as the domain name system to connect to one another in a human-readable way.

When you click on a link, or type a website name into your browser, your browser has to look up the numeric address of that site in order to make a connection to the site. This is known as a domain name lookup. This process uses thousands of domain name servers around the world to make this lookup happen instantly. If a computer or phone or device can’t reach a domain name server, it can’t find the website you’re looking for.

Around 4:20 AM on Saturday, April 3, the domain name servers on the School of Public Health network started having problems. As a result, nearly all of the computers, servers, and devices on the JHSPH network — including the servers that power CoursePlus — couldn’t talk to one another properly. CoursePlus talks to a lot of different systems, including SIS, Zoom, NameCoach, and Amazon Web Services. When it couldn’t talk to these other systems normally, it started slowing down and dropping some connections. Some people could get through on some requests, but others could not.

The JHSPH IT team, who manages the network infrastructure at the School of Public Health, was hard at work on resolving this problem early this morning. At 10:19 AM, they confirmed that they had resolved the issues with domain name lookups on the SPH network. CoursePlus resumed normal operation almost immediately.

We know how incredibly frustrating it is to not be able to work on CoursePlus when you need to. Fortunately, CoursePlus outages are rare. We appreciate the hard work of the JHSPH IT team in resolving the problem, and restoring full access to CoursePlus again quickly.