Thoughts and Ramblings

In one of the El Capitan updates, I had issues where iTunes playback would start skipping when the CPU was under heavy load. I noticed that if I brought iTunes to the foreground, the skipping stopped, but if the heavy CPU load application was in the foreground, it resumed. Being a developer, this meant that my music would continually skip whenever I compiled something, which is a common occurrence. I was able to conclude that App Nap was the culprit and disabled it.

This weekend, I noticed that the spinning hard drive in my MacBook Pro was dying. I ordered a replacement, installed it, then proceeded to install Yosemite. After counting the numerous Yosemite installer bugs, I noticed an unusual one:

This copy of the Install OS X Yosemite application can’t be verified. It may have been corrupted or tampered with during downloading.

My searches for this didn’t yield a useful solution so I figured out what the problem really was: Since I disconnected the battery as part of my install process, the computer was completely without power for a moment and loss the date/time. So, I set the date in the terminal using the date command, and then the above mentioned error went away.

The term Net Neutrality covers a lot of hotly debated topics but at its core is whether ISPs should be allowed to treat some traffic differently. In the midst of the discussion, one minor fact seems to have been lost: Not all packets are truly equal.

Around 10 years ago, I had DSL with 768kbps down and 128kbps up. I quickly learned that if I did any upload at all, the download speeds suffered greatly. Upon investigation, I discovered that the outgoing control packets, such as ACK packets, were being stuffed in the same queue as outgoing data packets. One of the solutions was to employ egress traffic shaping. This was simply prioritizing control packets such as ACK, SYN, and RST, followed by small packets all ahead of the large data packets. The result: uploading data no longer slowed downloads. Today, with much higher speeds, this shaping has less benefit, but it is not gone.