8602 is the XBC port forward, so XBC does actually require the port forwarding.
It also requires 2 port forwards, one on UDP, one on TCP.
We require 34518 and 34519 both on UDP.
XBox Live doesn't need port forwards because the ports it runs on are registered for use with XBox Live and most routers / ISPs will accept the port without any interference.
|Is it really necessary for the three ports mentioned in Troubleshooting (UDP 88, UDP 3074, and TCP 3074) to be opened for Xbox Live to work properly?|
Most cable/DSL routers implement Network Address Translation (NAT), as does Windows Internet Connection Sharing (ICS). For NAT devices, no port forwarding is required for Xbox Live to work. Port forwarding is required only if you are running a proxy server or true firewall instead of or in addition to a NAT.
Also, the VoiceStream port works for most people without any configuration of their router, but if it doesn't then the additional port forward is required.