Airport Extreme (AC) wireless extending - is it using AC speed?

[hualon]

I have two Airport Extreme (AC) routers in the house. One is the router and the other is configured to "Extend a Wireless Network" and is, in turn plugged into a couple Ethernet devices upstairs. I am extending the network wirelessly.

My questions is: how fast should the link between the primary (router) and the WAP be? Is it, in fact, using AC speeds or is it using N or something else? How would I know?

I ask because I'm getting surprisingly slow data transfer speeds from my desktop (wired to the "Upstairs Airport Extreme AC") to my NAS... ~9MB/s.

If I transfer files to the NAS from my Macbook Pro (late 2013 with AC) then the speeds are crazy-fast.

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Followup with more information:

1. I am using SuperDuper to back up and it is indicating the 9MB/s figure.
2. I stopped the transfer and did a disk speed test (black magic) to the network volume and it registers ~36MB/s write speed
3. The network volume is mounted using AFP
4. SuperDuper is writing to a .sparsebundle

 

[Altemose]

When wirelessly extending, only half of the bandwidth is available due to it also having to carry it to the original Extreme.

 

[mneblett]

Not to mention the decrease in signal strength/throughput due to distance and wall/floor penetration.

 

[tdale]

When wirelessly extending, only half of the bandwidth is available due to it also having to carry it to the original Extreme.

Thats correct, its half duplex. It sends or receives. Full Duplex send and recieves at the same time. Extending assumes range and AC will drop off far sooner and far faster than N. Best option is to cable as far as you can, if that is an option, and set the extended router as an Access Point. That will reduce the range and be full duplex

 

[Brian33]

My questions is: how fast should the link between the primary (router) and the WAP be? Is it, in fact, using AC speeds or is it using N or something else? How would I know?

Open Airport Utility 6.3.1 and click the remote WAP airport. In the displayed box there's a label "connection" followed by something like "Excellent" (in my case). If you hover the mouse pointer over the "Excellent" or whatever yours is, another info box will pop up that shows the connection's type, data rate, RSSI, and PHY mode. The data rate should give you a good idea of the connection between the two airport devices. (There are other places you can hover over to get info, too, but I've never seen them documented anywhere.)

As others have pointed out, at a distance the connection will probably be in the 2.4 frequencies. I'd guess that it picks the strongest signal, not necessarily the fastest connection. If you name your 2.4 and your 5 GHz networks with different names, you could configure the remote airport to (try to) connect to the primary router using the 5 GHz frequencies. Maybe they are close enough that you'd get better throughput that way even if the signal reception is weaker...

As noted, though, probably the half-duplex nature of extending wirelessly is the biggest problem. That's why I ran an ethernet cable through my crawlspace to the other side of the house where I have an airport express set up.