[huyegn]

Absolutely agree with this.

Another nice illustration of how when arrival rate is greater than departure rate we get overflowing queues:

http://setosa.io/blog/2014/09/02/gridlock/index.html

[l3nz]

I sometimes use this - that was built as a call-center simulation - to get quick-and-dirty figures to have an idea of the actual queueing strategy tradeoffs. Queueus are okay, depends on what you want to do with them. http://queuewiz.queuemetrics.com/