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Nintendo DS - WI-FI vs NI-FI
Posted by Darkain on Fri Jan 21, 2005 3:20 am
Explanation of OSI Network Model Layers

The Nintendo DS fully supports IEEE 802.11 specifications. People have argued that because of the slower data link speed and lack of a TCP stack, that the DS is using something other then "Wi-Fi". This is put here to set things right.

The OSI Network Model describes 7 layers of communication. Layer 1 is the hardware layer (basic wireless), and Layer 2 is Data Link Layer (MAC). IEEE 802.11b lays out the guidelines for a wireless connection operating at the 2.4ghz spectrum (separated into 14 channels), and using MAC packets similar to that used in IEEE 802.3, and operating speeds of 1mbps, 2mbps, 5.5mbps, and 11mbps. An optional feature of 802.11b is short preamble while requiring support for long preamble, however, 802.11g requires devices to have both.

The Nintendo DS uses IEEE 802.11b for ALL of its wireless communications. The DS operates at a specific subset of the features of 802.11b, including only operating using short preamble (not sure if this is a software option on the DS), and only operating at 1mbps or 2mbps max (to save power).

The DS does not internally support a TCP stack or any IPv4/IPv6 communications at all. This is why the DS cannot be played online without the use of tunneling (see below). It will be possible for future DS games and applications to implement the TCP/IP protocol via software, but none of the current titles do this. Does this mean that the DS isn't using "Wi-Fi"/802.11? NO! 802.11 only lay out the framework for layers 1 and 2 of the OSI model. IPv4/IPv5 occur at layer 3, while TCP/UDP occur at layer 4. Since the DS communicates on layers 1 and 2 using 802.11, if there was a software application/game for the DS to implement TCP/IP, it would work with a home network and even possibly the internet.

The layer 3 protocol that current DS software supports is not routable over the internet. The reason it does not work, is the same reason why protocols such as IPX/SPX, NetBEUI, and AppleTalk cannot be routed via the internet. The internet current supports only two major protocols, IPv4 and IPv6. If we take a look at our home equipment and compare a home based network hub to a network switch to a network router, we can start to understand why. A network hub will take in a MAC packet from one source and forward it to all potential destinations, and then the destination determines if it should accept the packet or not. Network switches are slightly more competent. Switches hold an internal MAC address table, this way, MAC packets are forwarded to the correct destination, and all other potential destinations are ignored. Routers work in a different manor. Routers operate strictly based on layer 3 IP data, instead of layer 2 MAC data. If you try to shove non-ID data across it, once it hits the next router (most likely your ISP), the data will be discarded if it cant translate and parse the message.

Tunneling works by padding the MAC data with an IP header so that data can be transmitted over the internet. The destination machine receives this packet, strips out the IP headers, and repeats the messages as a MAC packet. This can be applied to the DS as followed. DS 1 sends MAC packet. PC 1 receives MAC packet. PC 1 applies IP header to MAC packet. PC 1 sends IP packet over the internet. PC 2 receives IP packet. PC 2 strips out IP headers. PC 2 sends MAC packet. DS 2 receives MAC packet.

Wi-Fi vs Ni-Fi? no. Ni-Fi is not an alternative to Wi-Fi/802.11. Ni-Fi is a layer 3 protocol on top of 802.11.
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