What networking topics could I viably explore and conduct a project in this summer?

Hi, I just finished my junior year of college. Last fall, I took a networking course where we coded our own implementations of TCP/IP (based on rfcs 791 and 793). This summer, I don't have anything to do, so I was hoping to do some independent learning about more advanced networking topics, and also take on another coding project.

However, I'm a bit lost, and I don't know how to move forward. There are a LOT of topics in networking, it seems, and they are all very complicated and overwhelming. For example, I was interested in SDN and Openflow, but I'm just totally lost trying to do more reading on the subject.

So, I'm asking for help, if anyone knows any worthwhile topics that I should look into? I'm looking for things which are relevant today, which I can feasibly grasp at my level, and which I could even come up with a coding project for.

Thanks very much!