What should the server administrator investigate when the download speed is decreasing?

When the speed of the internet line is slow, I think that there are times when you think that "People around me are watching movies on YouTube and other video sites and are crowded". However, even though we can guess the cause, it can be said that it is virtually impossible to require specific expertise to investigate in order to be specific. We are developing web development application "Coda" for iOS and macOSPanicSo, suddenly the download speed of the application slowed down, so we investigated and found that the cause was able to be located.

Panic Blog »The Mystery of the Slow Downloads
https://panic.com/blog/mystery-of-the-slow-downloads/

The correspondence which Panic actually did is to be understood by seeing the following movie.

The Mystery of the Slow Downloads - YouTube


The network configuration of Panic is very simple, and between Panic's server and usersAWSYaPaaS,CDNIt seems that we do not introduce such a system as going through other networks. The server of Panic is between the userProvider(CogentThere is only a structure that there is. In other words, it is almost the same environment as when you use internet line contract at home.


Panic seems to have looked back at possible server configuration file and OS parameters etc. inside the Panic, but it seems there was no particular problem. So I decided to write a test script to download 20 MB files and test it. In this case, I decided to compare the download speed with the server called Linode which is located at another base from the Panic server in question.


When actually downloading through the network of many providers, we found out that only the download speed of the user connected to the provider of Comcast is remarkably slow.


Usually between providers (ISP)PeeringWe exchange information such as route information and connection status while checking communication with each other.


Therefore, when a user tries to connect to a different server of a connection provider, communication such as route information is carried out beforehand between ISPs so that communication can be performed smoothly.


However, this problem may be due to some trouble with the communication between Cogent and Comcast provider to which the Panic server is connected.


According to Panic, Cogent has found out that there is a fact that Netflix content is distributed to Comcast users. In other words, it seems to have speculated that the big traffic of Netflix flowing between Cogent and Comcast is the cause of this problem. Therefore, contacting people in Comcast and Cogent's network personnel and explaining the circumstances, "Please wait for about one or two weeks, and you should be satisfied with the retesting at that time."


As I told you, testing again after two weeks seems to have improved the line speed dramatically.


According to the person in charge of Comcast, "correspondence between increase in traffic capacity between Cogent and Comcast" and "change of parameters of communication equipment" were dealt with, and the problem was solved. However, although Panic is satisfied with the fact that the problem has been solved, there seems to be a part that is not convinced, "Why aware of the fact that communication traffic between Cogent and Comcast is tight (pulls) It seems to be in doubt that "Was not there was it?"