The problem, if I remember correctly from what Bungie themselves have stated, has to do with NAT settings, which are directly involved in their matchmaking system, and therefore pretty much unavoidable.
Trakan and I often have this problem when trying to join oneanother's games. Like he said, if you've pegged who is having trouble joining the room, have them sign out and try again. If you can't figure out who it is, have everyone do it. Sometimes I can't even after signing out, and have to power-cycle my Xbox. It's a total pain in the ass, but it's the only reliable way to fix the problem unfortunately.
Hey, waddyaknow, I found the
Bungie.net article detailing the problem.
[quote name='Bungie']Dozens of you asked,
Sometimes when I try to accept a party invite, I get a blue screen with an error message saying something about, 'Sorry, we're having network troubles." What are these troubles, exactly?
One of the reasons players will sometimes encounter the infamous "We're experiencing network problems" message when trying to accept a party invitation is NAT type incompatibility. This unfortunately is one of the ways we ensure good, solid connections and is unavoidable. Below is a somewhat dry explanation of what a NAT type is, but before you lull yourself to sleep � here's a possible solution � it works for us quite often.
If an invitation fails, you can try to get a NAT compatible host or player to start a brand new party then have everyone join him instead. When everyone rejoins this new party they simply have to keep their fingers crossed that a new host can invite the failed invitee successfully. It's annoying, but it's usually for someone who's worth the extra effort.
How do you know who this host will be? In many cases, simply having an excellent connection � a T3 line for example, will often ensure hosting duties and compatibility, but there's no surefire way to know. One other solution, which is less drastic, is to start a custom game and then immediately quit and start again � Halo 2 will always try to find a best-case host, and that may fix the invitation failure by auto selecting a new, better host.
Again, we wish there was a way around this, but it happens at the router level and it happens on other systems and games. The reason we don't identify the host is obvious to anyone who's suffered through other forms of router and modem-related cheating.
NAT is an acronym for "Network Address Translation" and is also known as Network masquerading or IP-masquerading. This is a technique in which the IP addresses of network packets are rewritten as the packets pass through a router or firewall. This technique is used to enable multiple hosts on a network to access the internet using only one IP address. Now, even though routers aren't really supposed to do this, sometimes they do anyway, since it's a very convenient little trick. The problem is that this incompatibility in NAT types causes communication problems between hosts, and that's where the "Network Problems" message is encountered.
We should note that other factors can contribute to this problem, but NAT type is the main culprit[/QUOTE]