Xbox Live/Connection Test
The network settings screen on the Xbox Dashboard will perform a connection test to Xbox Live when a user edits settings, to ensure that it can still connect to the Internet.
If the user has not connected to Xbox Live before, this will be where the Xbox first connects to create a Machine Account via MACS (Machine Account Creation Service). Then, it will use this account to authenticate the machine and perform a ping test as well as a speed test on dashes before 5960(? double check if this was the first dash to change behaviour).
Pressing Y once the connection test has finished will show some extra info;Pressing A on 5960 or later will perform another test using
xds.xboxlive.com- this server is still up (CNAME'd to xds.gtm.xboxlive.com, IP 184.108.40.206). This will then return three more results:
MT - MTU test, if 1 your MTU is 1365+ and works with Xbox Live, if 0 then <1365 IC - ICMP test, if 1 your router is properly forwarding ICMP, if 0 then not NT - NAT test, where 1 is open, 2 is moderate, and 3 is strict.
This info is from Xbox Live's archived diagnostics page
Pressing the Black button on the controller once the connection test has finished will save a packet log to the hard drive as a save [FIXME: add more info] - xbcap2pcap can convert this DAT file into a standard PCAP.
The DAT's structure is as follows:
uint32_t total packet length uint32_t timestamp in ms total packet length - 8 bytes of Ethernet packet data