I've waited to post again because I've been doing some research and also ran this by a couple of people in desktop support where I work. Their answer? Get a sniffer [packet capture] trace. Hm. But they always say that because they know us network guys can usually figure things out.
First: Steam authentication traffic is encrypted so, no, a packet capture of network traffic when you start your game does not place your Steam credentials at risk. Yes, you should always be careful when transmitting anything over the network.
As I always remind people - you should always assume anything transmitted (or received) via the Internet is being monitored or captured. So, if you are worried about it, either don't send it via the Internet or encrypt it.
A packet capture is different than a keylogger because it operates at a different hardware level. More questions? Feel free to PM me.
So, aside from the somewhat alarmist statement of "logging his authentication", if you're uncomfortable with a trace, that's fine, ManBearPig. We can work around that. I'd still want you to get one. I'll just have to walk you through what things I'd want to look for and have you look for them instead.
Second: Why did I want a packet capture? Because I want to know what the heck the PC and the game server are saying to each other that results in larger and larger packets being sent to the PC.
The tools at Sysinternals (know many of them and love em' all) show network socket and basic network information from the PC perspective. That's not what I want to see.
Specifically, I want to see the TCP window negotiation and renegotiation.
Third: Why do I want to see the TCP negotiation exchange? Because, as I said earlier, the "in" of net_graph does
NOT refer to amount of bandwidth being consumed. Instead, it refers to an absolute number: the size of the last packet received in bytes.
The next stat refers to average bandwidth used, inbound. And from the original image, it's about 4.7 Kbyte/second. That's fine. In fact, if you look at the original post, with a 138 ms ping and 53 FPS, things look really fine.
Except.
If "in" is really getting to 5000, there's something goofy there. But we already know that. And also... notice the 27.3 on the far right? That refers to the average number of packets being sent from the PC to the server.
Interesting.
ManBearPig,
Startup your game, please, and in the console, type:
cl_updaterate
cl_cmdrate
What are the results you have for those two entries?
Last, it certainly won't hurt to install an Ethernet card, but you don't seem to be suffering any ill effects from being wireless (surprise!). At a bare minimum, it should reset the IP stack - which is where my interest lays right now.