Connection Host
From Halopedia, the Halo wiki
Connection Host is a term used to define the player with best connection in a Halo 3 online Multiplayer game.
Finding the Connection Host
Finding the connection host can be found out in several ways but one can only be used in forge.
First Method
The first method is the easiest but can only be used in forge. Simply have multiple people in a game on forge then have everyone turn into editor mode and look straight down. Then have everyone turn back, whoever is still looking down is the connection host.
Second Method
The second method can be used in matchmaking and stuff (which is kind of pointless unless you are trying to Power Drain Jump. Grab any equipment and walk up to an overshield or Active Camo and crouch and walk to it VERY slowly while holding RB and if you use the active camo or overshield you are the connection host otherwise you will pick up the overshield or camo as if it was an equipment.
Third Method
The third method requires two people to be in a theater lobby. In order to view films, the person with the best connection will have to be the party leader.
Purpose of the connection Host
The connection host was a feature bungie inserted to help keep an online game balanced see it as everyone is "feeding" off of the connection host's connection. In a Nutshell it's supposed to help an online game run better.
Forcing the Connection Host
It's possible to force a person in the party to be the connection host.
Walkthrough
Have everyone except the person who is wanting to be the connection host leave the game and join back. This will force that player to be the connection host since he will be the only one there thus having the best connection.