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My office network has a fully switched 1000Megabit ethernet network. I have an Apple iMac with a Gigabit NIC and FireWire, and a Compaq laptop with a 100Megabit NIC and a 4-pin FireWire interface. Accessing my office's shared drives using my laptop is (obviously) much slower using my laptop than my iMac. Would I see a noticible performance boost if I enabled Internet Connection Sharing on my iMac and shared the private ethernet network from my iMac with my laptop over FireWire? FireWire is 480400Mbit/sec, right? So would I see roughly 4x speed improvement with such a setup?

EDIT: OK. Having set this up I find that performance is actually worse when copying a file from a server on our ethernet network to my laptop, when my laptop is connected to my iMac using FireWire. I suspect this is because of NAT on my iMac slowing things down?

I got about 5.9 MB/sec when copying a 100Meg file over 100Megabit ethernet, and only 3.6 MB/sec when copying the same file using firewire <-> iMac <-> ethernet. But when going between the iMac and the laptop using FireWire I get 11 MB/sec! So it must be NAT slowing things down then, huh?

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Thanks for the edits @ChrisF! I was typing way too quickly, that was sloppy of me – Josh Apr 9 '10 at 15:06
"FireWire is 480Mbit/sec, right?" Firewire 400/IEEE 1394a is 400Mb/S, not 480, and in practice runs much faster than USB 2.0's supposed 480Mb/S. You should see speedups versus 100Mbit ethernet. "loswer"? – kmarsh Apr 9 '10 at 15:50
@kmarsh: I'm just not with it today! Thanks for the corrections. – Josh Apr 9 '10 at 16:03
up vote 2 down vote accepted

Sure. For point-to-point FireWire is great. Unlike USB, FireWire controllers have brains and can handle data transfers easily. Do be aware that CPU usage will go up though.

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When you say CPU usage will go up is that due to NAT? Could that be why I'm finding that using firewire is slower? – Josh Apr 9 '10 at 15:50
It will go up because you have to feed the data to the interface that much faster. It could be slower because the driver just isn't optimized for networking. After all, many more people use Ethernet for networking rather than FireWire, so there's little motivation to get it right. – Ignacio Vazquez-Abrams Apr 9 '10 at 15:56
Ah, I missed that you were bridging it to the LAN. Yeah, that could slow it down. – Ignacio Vazquez-Abrams Apr 9 '10 at 16:10
Since there's no other devices on the firewire chain I don't need "full" NAT. Is there any way I could just translate ALL traffic from my laptop to a given static IP on the 10.1 network? Something like <-> – Josh Apr 9 '10 at 16:19
Since that's really a different question, I asked it as such: – Josh Apr 9 '10 at 16:20

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