187. Game Design, Development, and Technology
CS 382
Game Design, Development, and Technology
Networking and Multiplayer
Client-Server vs. P2P
MMOGs
Console Connectivity
Centralization vs. Decentralization
Network Latency
Cloud Gaming
Part 5.6

188. Networking and Multiplayer
Networked Gaming
One-to-many communication, in which each player’s actions are relayed to all other players, is problematic in networks today.
Peer-to-Peer
Scalable
High Performance
Low Security
Low Control
High Resilience
Low Cost
Client-Server
Not Scalable
Low Performance
High Security
High Control
Medium Resilience
High Cost
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Networking and Multiplayer
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189. Networking and Multiplayer
Massively Multiplayer Online Gaming
Gamers control the client applications, which deploy and run graphics, the user interface, and network communication.
The proxy/gateway is important not only in forwarding packets but also in providing security functionalities (as it can work like a firewall or run the protocol-checking procedure) for cell servers and cooperating with portals or billing systems.
The cell server houses, maintains, and executes the virtual world. It also receives players' control commands and verifies, computes, updates, and then forwards new player states to all gamers who will be affected by these commands (for example, a successful move command will generate a player's new position on the virtual-world map).
The database stores periodically updated player states to ensure that players continue to exist in the virtual world.
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Networking and Multiplayer
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190. Networking and Multiplayer
Differences Between MOGs & MMOGs
MOGs
MMOGs
Usually dozens of simultaneous players
Usually tens of thousands of simultaneous players
Game terminates when players depart
Game persists even after players exit
Lend themselves to user-created modifications (mods)
Mods usually not supported since games played on company servers
Players often play in sequence instead of simultaneously
Simultaneous play even when players aren’t using the same map
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Networking and Multiplayer
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191. Networking and Multiplayer
Console Connectivity
By the year 2000, each major console system provided connectivity via dial-up and/or broadband.
Xbox Live (2002) was highly centralized, so game companies supplied networking code and gameplay, but Microsoft provided the server bandwidth and user front-end.
This removed the financial burden from game developers who did not already have networking systems in place, adding incentive to include multiplayer modes to certain game genres.
Also, instead of paying third parties for access to each individual game, users paid only one subscription fee for every game they owned.
In addition, Xbox Live was broadband-only, so it was much less susceptible to network lag, although it did exclude users in geographic areas where high-speed Internet access was not affordable to residential customers.
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Networking and Multiplayer
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192. Networking and Multiplayer
Centralization Downsides
In addition to subscriber fees ($60 annually for Xbox Live Gold), specific game publishers may charge monthly fees, such as Phantasy Star Universe's $10 a month.
The centralized requirement of Xbox Live was also one of the reasons why Electronic Arts was reluctant to use the service. However, in 2004, Electronic Arts finally released its first Xbox Live title, NCAA Football 2005.
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Networking and Multiplayer
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193. Networking and Multiplayer
Portable & Console Wi-Fi Connectivity
The Nintendo 3DS and Nintendo Wii U have built-in Wi-Fi, allowing certain games to be played online via a wireless hotspot or through a wireless router.
Nintendo has also provided a device that connects the 3DS or Wii U online via a Windows computer, a USB port, and a broadband connection as an alternative to buying a Wi-Fi router.
Nintendo’s “Download Play” ability allows multiplayer network games to be played across multiple systems with only one copy of the game being played loaded into a participating system.
The Wii U also features connectivity with the 3DS.
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Networking and Multiplayer
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194. Networking and Multiplayer
Decentralized Connectivity
The original plan for online services for Sony’s PlayStation 3 games was that it would be decentralized and left up to individual game publishers.
While this would have given games publishers greater freedom in terms of what they would be able to offer online, it would have made it more difficult for Sony to control the quality of the online experience.
Three Gigabit Ethernet ports
IEEE g Wi-Fi
Bluetooth 2.0
USB 2.0 (4 front & 2 rear ports)
In addition, there would have been different user interfaces for each game depending on the developer.
Ultimately, Sony decided to design its online service (PlayStation Network) as a centralized service to compete with Microsoft's highly successful (10 million subscribers) Xbox Live.
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195. Networking and Multiplayer
Network Latency
One problem with networked games is the lag between one player’s actions and a remote player’s perception of that action, caused by the latency of the network connection.
This can cause particular problems in a game when one player perceives a successful hit while another perceives a clean miss.
If the server is told to update remote players after the original player fires, the update can appear as a shot that “came from nowhere”.
By taking the position, velocity, and latency all into account, the server can compute the shot as going faster than the original player perceived it, and can tell remote players to calculate it as even faster than that, choreographing the calculations to yield the same end result on each machine.
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196. Networking and Multiplayer
Cloud Gaming
Three primary obstacles have prevented networked gaming start-ups from successfully offering cloud computing services, in which games are synchronized, rendered, and stored on a remote server and delivered online:
Latency: Between pressing a controller’s fire button and being presented with the appropriate audio-visual response, players are only willing to tolerate a delay of about 120 milliseconds. (A typical network ping to a server takes milliseconds; GTA IV has a raw response time of 200 milliseconds on a non-networked flat panel TV.)
Video Compression: All current techniques combine intra-frame compression (exploiting spatial redundancy) and inter-frame compression (exploiting temporal redundancy). While compressing the video to about 1% of its original size reduces network latency, the actual compression and decompression takes time (which varies with camera motion speed and cut scene usage).
Bandwidth: Even game streaming companies like GameFly, Utomik, and StreamMyGame require 1.5 Mbps for SDTV and 5 Mbps for HDTV. (average broadband rates in the U.S. are 3.9 Mbps, with 25% having over 5 Mbps).
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