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Understanding Zone Connections
One of the most common complaints you will hear in the Tech room is a retail game player stating that they cannot join/host a retail game. Other descriptions of this problem include (but not limited to):
• Zoner’s States the error message “we have paused your connection to the zone while you were playing, Press the resume button to return to the zone”, while this is not an error message the zoner may perceive it as one if they think that the game is being played on the zone servers.
• The zoner may state that when trying to play they are disconnected or booted from the zone (again this is caused by the mistaken perception that they are playing on a zone server rather than a direct connect game)
• The zone may state the game crashes and returns them to the game lobby.
• The game may start in single player mode.
• The error message that the Zone does not support NAT, or other IP masquerading.
• The game may report being unable to connect to the lobby.
• The game launches but the zoner cannot see other players or players below them in the list.
All the above are symptomatic of the game failing to establish the required direct connection between players and game host.
Understanding the Zone’s Retail Gaming
The zone acts as a match making service for zoners with supported retail games installed on their systems. The games are not played on a zone server (given the number of players and the number of servers and bandwidth required to run a server based service this is understandable).
When the host clicks the launch button the game on their system is launched in a direct IP hosting (multiplayer) configuration. The players in the game room are then connected to the host and each other using a Dplay server connection. Dplay is a part of the DirectX package so often you will hear of these games being referred to as DirectX games.
After the connections between players are established the connections to the zone chat rooms are suspended and the zoners zone messaging is put into DND mode. This is done to reduce lag from the chat in the chat room and to prevent some messages popping up in play distracting the player or dropping the game to desktop.
Initial contact between player and host (handshaking) is done on one of two ports either 47624 (DX3-7) or 6073 (DX8). Once ommunications are established each player is connected to the others by opening a negotiated secondary port in the range of 2300-2400 TCP and UDP (2302-2400 UDP for DX 8). When game connections fail to establish it is typically because one or more of these ports are blocked or because a router/firewall/proxy server is improperly configured.
Direct Play connections are not capable of surviving the translation of IP protocols used by most proxy servers and NAT based routers. As a result the information being sent/received on the playing ports must be sent directly without translation to the client PC for the game connection to succeed.
It is also important to note that while it may be possible to connect two PCs to a common Internet connection using a hub, the lack of a unique IP address for each will also prevent the game from connecting properly.
Understanding Routers/Proxies/Firewalls
A firewall can be either software or hardware based. Its primary function is to act as a traffic cop, which stops unauthorized connections to the client PC. There are various types of firewalls and they have differing capabilities, far too many variations to discuss in detail here.
The classic firewall works by inspecting the inbound traffic from the Internet’s 65K possible connection ports and allowing only permitted traffic through as specified by the user in the firewall configuration.
More recently “vectored” firewalls have become prevalent, which allow connections to the Internet based on specific applications rather than a port-by-port specification. In general the user gives a particular application access to the Internet and the firewall then allows it to open any ports it requests. This type of firewall is far easier for the zoner to use on the whole and unless it’s stopped working properly, the user only need give permission for a game to connect and the firewall manages the connections from that point.
Proxy servers act similarly to routers, the server acts as a proxy or agent for the client PCs on the users network and directs traffic to the client PCs by tracking the packet header information to determine which client has sent information to a specific IP address and remembering which machine gets the replies from this address.
NAT based routers are hardware based proxies. Because the information is processed outside of the users PC they tend to be much faster solutions to establishing a network of several PCs sharing a single Internet connection but they function in much the same way.
When the user connects to their ISP they are assigned a “public” address from the ISP’s IP bank typically using DCHP (or dynamic) assignments from the ISPs server. This address is the one viewed by the public from the Internet. The router then establishes private addresses for the client PCs on the network in a range that is typically in one of the two reserved address ranges (192.168.xxx.yyy for windows reserved Class C or 10.10.xxx.yyy for NAT reserved Class A).
When a connection is established from one of the client PCs to an Internet site the packet headers contain the private address of the client and the IP address of the web site (translated by the ISP DNS) as well as the protocol to be used (TCP or UDP) and other information. The router/firewall/proxy uses this information to determine which PC will be the recipient of the replies from this address.
Bearing in mind that the DPlay server connections can not survive translation in the proxy/router we need to establish direct paths for these connections to allow the game to connect successfully by using either “port forwarding” or disabling the NAT firewall of one of the PCs on the network (most commonly referred to as establishing a demilitarized zone or DMZ). The choice of DMZ or port forwarding may be determined by the router (DMZ may not be supported in some routers) or by the user based on the need to connect one machine only (DMZ would be acceptable) or more than one client (Port Forwarding required for the entire network).
Routers – Some Finer Points
All routers include some form of configuration management tool. There are just too many different manufacturers and models to attempt to maintain a list of specific instructions for each so for the most part you will attempt to describe the process of router setup in broad terms only and refer the user to the router documentation for specifics.
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