Non "n" hardware on an "n" network-- speed degradation?

Discussion in 'Mac Accessories' started by michaelsaxon, May 16, 2007.

  1. michaelsaxon macrumors 6502

    Nov 15, 2006
    I can't seem to get a straight answer on this. I have an older Macbook Pro that doesn't have "n" capability, as well as a Wii, but I'd like to get an Airport Extreme for my AppleTV (and for the network hard drive / printer capability).

    Will having my Wii and MBP on the "n" network kill the "n" speeds for my AppleTV? Thanks.
  2. Anonymous Freak macrumors 603

    Anonymous Freak

    Dec 12, 2002
    Alright. It's technical, but here it is:

    Yes, having non-N gear on an -N network will reduce the speed of -N hardware. But it will *NOT* drop all the way to -G speeds.

    The technical explanation is that if we assume that each device transfers a full size 1500-byte packet, then faster devices will take less time to transfer that packet than slower devices. That means that slower devices will take up more of the base station's time to transfer the same amount of data.

    Let's talk theoretical (and overly simplified) for a moment:

    We have a theoretical 802.11 Draft 2.0 N router with a Gigabit Ethernet switch on it. We have a server connected to the Gigabit Ethernet port that is capable of transferring files at the full 1 Gbps speed, so it can obviously flood -G and even -N clients. With a single -N client, the router sends data at full -N speeds. With two -N clients, each client gets approximately 50% of the speed, because each one takes 50% of the router's time and effort to service. With one -N and one -G client, the -G client will take up more of the time, because it takes more time to receive each packet than the -N client does. Let's say it's 66% of the time on the -G client and 33% of the time on the -N client. But, because the -N client can transfer data 5x faster than the -G client, it is still receiving data faster than the -G client is even capable of if the -G client were on the network alone.

    So, yes. The -N client will see a speed reduction, but it will still be faster than -G.

    In reality, 802.11n handles it much better than my oversimplified explanation above. In my explanation, with my sample math, one would expect the -N client to be receiving data at approximately half its maximum possible rate. In reality, it's better than that because of the way 802.11 really works.

    (Although, in reality, 802.11n will never reach 300 Mbps of true computer-to-computer data throughput, just as .11g never reaches 54 Mbps, and .11b never reaches 11 Mbps. But that's another topic.)
  3. michaelsaxon thread starter macrumors 6502

    Nov 15, 2006
    Thank you for that very thorough reply. It seems I'll be well-served by going from my Linksys G router to an Airport Extreme!

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