I had 98% iPhone battery life left, but wanted to make sure it hit 100%. I was on-call for the next 7 days - and it was only Day 1. Seems ridiculous to think the phone's battery would die completely overnight, but I didn't want to take any chances. I was primary on-cal...
When there are network connectivity issues, the first thing to be blamed is the firewall.
40% of my job is proving that the issue is not with the firewall. The simplest of tasks is just showing the customer that traffic has ingressed and egressed successfully out of a dual or multi-homed firewall.
The OSI Model is used to describe how data moves from your networked computer to an application in another network. Instead of trying to memorize all the layers, the protocols, and what device belongs in which layer, it is better to just know the concepts.
Here is an excerpt from the OSI Model video from the members section of the site.