Considering the USB port of models like RB751U-2HnD, I didn’t find in the PDFs the theoretical speed limit for the USB port in Routerboards. The reason I am asking it if because of the following concern: using this port for a 3G USB dongle modem or a LTE modem, could the USP port speed limit be a bottleneck? For a single modem the answer might be no but if I plug three, four, five modems using a USB hub, could they hit this bottleneck.
Could anyone provide this number? Thanks in advance.
Routerboard uses standard USB 2.0, and the USB 2.0 specifications.
The “practical” limit of USB 2.0 is up to 40 MB/sec (or up to around 300 mbps).
3G is MUCH slower than that… so you should be ok on speed even with multiple modems as far as the speed limit of the USB port is concerned.
I’m not sure if the USB 2.0 standard used in the Routerboard actually mean they are capable of reaching the limit of the specification, in that case, the 40 MB/sec. I wonder if other factors (due to the Routerboard architecture) would reduce this value, for instance, a bottleneck between the USB I/O and the other components or the CPU itself.
Is there a way I can measure this speed in a reliable/relevant way?
Sure, you can use a 100mbps USB Network Adapter. Then, measure the throughput through that adapter. You will find out the maximum throughput that can go all the way through the router from the USB port.
What a clever idea! That would generate really reliable data. Thanks.
This one works great with RouterBOARDs http://store.apple.com/us/product/MC704ZM/A/apple-usb-ethernet-adapter