I had stopped working on improving the course, and posting on this subject, as it was unclear if I would be teaching it again in the spring. Now this appears to be cleared up, so I'll resume posting about what I'm doing.
The highest priority is improving the projects. The second and third project descriptions are very sketchy by comparison with the first project; I need to bring them up to the standard of the first project. In addition I want to add a fourth project which involves adding SSL to one of the first three projects. Finally, I want to have them all install
Wireshark and learn how to use it to monitor the packet exchanges in their projects.
The next priority is the textbook change. At this point, I think we'll go with Kurose & Ross, Computer Networking: A Top-Down Approach as starting from the application layer may help in many ways; every other textbook I've looked at takes the old fashioned bottom up approach. This will require me to reorder my lectures as they currently track the bottom up approach, but I don't think that this will be a huge problem.
I am temporarily giving up on adding the network simulator, there is simply not enough time to set that up properly.