Very slow router speeds

Question

I have a ASUS RT-N16 router running the latest build of OpenWrt (OpenWrt Chaos Calmer r43801 / LuCI Master (git-14.359.33351-5e6c33e)). I've been experiencing some shoddy network performance, so I decided to create a 5GiB test file on my server (wired to the router) and transfer it to my desktop (Mac mini on wireless about 3 meters away).

My transfer speed has been topping out at around 250KiB/s. This is an internal network and should be MUCH faster than this, no? What could be the issue?

EDIT: I also had to kill the test transfer process because I couldn't post this question. The network was clogged - at 250KiB/s...

Answer 1

First let's set some expectations:

The ASUS RT-N16 is a very old 2.4GHz-only, HT40 (40MHz-wide channels) capable, 2 spatial stream 802.11n router. When using 40MHz-wide channels, it could use the 300Mbps data rate, but 40MHz channels in the 2.4GHz band hogs the band and doesn't leave room for other uses like Bluetooth, so Apple has chosen to make all their 802.11n products only use traditional 20MHz-wide channels in the 2.4GHz band. So the best PHY rate (physical layer per-packet signaling rate, before overhead) is 144.4Mbps. If your Mac mini is 3m away from your AP, and your AP is on a clear channel, then it should be getting the 144.4Mbps PHY rate. After Wi-Fi and TCP/IP overhead, a good throughput to expect for an efficient file transfer protocol (such as HTTP or FTP) would be 70-100Mbps (that's in megabits; 1,000,000's of bits per second; that's 8-12 MiB/s (MebiBytes; 1,048,576's of 8-bit Bytes)). So the 2Mbps ( == 250 MiB/s) you're getting is indeed quite low.

Some things to try, short of upgrading to a modern AP:

1. Make sure your AP is using the cleanest channel available. Use a spectrum analyzer like a Wi-Spy if you have access to one, because it'll show you all RF interference in each channel, including Bluetooth, wireless mice and keyboards, 2.4GHz cordless phones, microwave ovens, Wii remotes, wireless cameras and security systems, wireless speakers especially subwoofers, baby monitors, etc.. Otherwise you could use or a Wi-Fi scanner like inSSIDer, but that only shows you the other Wi-Fi stuff.
2. If you have wireless security enabled, make sure you're using WPA2, not WEP or WPA[1]. WEP and WPA used the old RC4 hardware implementations that were designed for WEP, and can't keep up with 802.11n speeds. WPA2 uses AES-CCMP hardware implementations that were designed for 802.11n rates.
3. If your OpenWrt lets you turn WMM (QoS) on and off, make sure it's ON. 802.11n requires WMM.

Note that with #2 and #3, if you had those set wrong, your Mac mini would be associating at 802.11g speeds, for a max PHY rate of 54Mbps, with an expected max throughput of maybe 25Mbps (3 MiB/s)

4. If OpenWrt lets you select 20MHz-wide channels, try that. Maybe it's not being smart about the fact that the Mac mini only wants to use 20MHz-wide channels, so maybe the AP is sometimes wasting time trying to transmit 40MHz-wide signals at the Mac mini. This is an unlikely case, but it's easy enough to try.
5. Disconnect or turn off all your other network devices while doing the test. Maybe a bunch of your bandwidth was being sucked up by some device doing automatic software updates in the background. For that matter, make sure your Mac mini and your server weren't doing any other network traffic in the background.
6. File service protocols that let you mount a remote share like it's a local disk (like SMB, AFP, and NFS) tend to not be as efficient as file transfer-only protocols like FTP, HTTP, and rsync. If you'd been using one of those remote volume mounting protocols, try one of the file-transfer-only protocols. Or consider using IPerf as your benchmarking tool so that you know for sure you've got a well-written, efficient TCP app without any file service overhead.
7. Try benchmarking the server over gigabit Ethernet to make sure it's not just that the server is choking.
8. Try going back to the latest official firmware from ASUS for a sanity check. Maybe OpenWrt sucks on the RT-N16.

Answer 2

Many factors could contribute to the slow transfer speed:

• Router is maxing out on its CPU or memory - you can verify this by going to the router's admin console and check the status to make sure its not maxing out when transferring file.
• Client connection - The latest OSX Yosemite (upgraded) seems to have some issues.

On your Mac, try removing the Network Configuration:

1. Turn Off Wi-Fi from the Wireless menu item
2. From the OS X Finder, hit Command+Shift+G and enter the following path: /Library/Preferences/SystemConfiguration/
3. Move the following files to a temporary folder somewhere: com.apple.airport.preferences.plist 
com.apple.network.identification.plist com.apple.wifi.message-tracer.plist
 NetworkInterfaces.plist
 preferences.plist
4. Reboot and reconnect to the Wifi