Stress Test

A little blurb on the front of the 610N's product box says: "Dual-N Band: Two N radio bands for twice the bandwidth". This doesn't mean that you can get 600 Mbps out of a single connection. Instead, you should be able to get the full available bandwidth from each radio if you're running clients on both. I hadn't checked this before, so decided to finally give it a shot.

I cobbled together the setup in Figure 13 for the test. I used two notebooks, each with a Linksys WPC600N dual-band draft 11n notebook card and set them so that one connected to each radio. I decided that one wired client using a gigabit Ethernet connection would be plenty fast to handle sending traffic to both wireless clients. Note that for the wireless stress test, all traffic is on the LAN side of the router, so the router performance isn't involved.

Figure 13: Stress Test Setup

I also decided it would be fun to stress the router section of the 610N at the same time as I was maxing out the wireless connections. So I set up two more gigabit-Ethernet connected computers, one on the WAN side of the router and the other plugged into a LAN port. This was to ensure that the router traffic was completely independent of the WLAN test traffic.

I first ran just the wireless stress test, basically blasting full-speed TCP/IP traffic between the two notebooks and the 610N. Figure 10 shows that the two radios do indeed operate at the same speeds that I obtained when testing them independently. Figure 14 shows uplink traffic. Downlink tests had similar results.

Figure 14: Simultaneous 2.4 and 5 GHz, 20 MHz channel, uplink

I then added full-tilt LAN to WAN traffic and finally found the 610N's limits. In Figure 15, I first started the two wireless uplink streams. 10 seconds into the test, I ran some LAN to WAN traffic, rate-limited to 10 Mbps for 5-6 seconds, and found no effect.

Figure 15: Simultaneous 2.4 and 5 GHz plus LAN > WAN

Then at 20 seconds into the test, I ran 5-6 seconds of LAN to WAN traffic again, but this time rate-limited to 25 Mbps. The stupid throughput dropouts (which are not an effect from the test) make it difficult to see the drop in wireless throughput. But look right between the 20 second mark and the dropout start and you can see about a 10 Mbps reduction in wireless throughput on both radios.

30 seconds into the test, I started my last blast of LAN to WAN traffic, this time at a 50 Mbps rate. You can clearly see both radios get knocked down to 40 Mbps throughput; about a 2/3 of their normal maximum speed.

My last little test is around the 45 second mark, where I just clicked on the 610N's admin interface to change from one page to another (no LAN to WAN traffic was running). You can again clearly see a 33% drop in both radios' throughput, as the 610N's CPU services the administration request.

It's highly unlikely that you would see any of these effects in normal use. But it was fun to see what happens when the 610N was pushed to its limits!

Closing Thoughts

I'm glad to see manufacturers producing dual-band routers, since they can provide a needed alternative for folks whose neighborhoods have too many wireless LANs competing for too little airspace. But the 610N shows once again that if you're looking for dual-band draft 111n to solve all of your wireless LAN problems, you're sure to be disappointed.

As I said earlier, I have yet to see a dual-band draft 11n product (either AP, bridge or wireless router) that is consistently good in both bands and both channel widths and the 610N is no exception. The MIMO technology used in draft 11n is complicated stuff and seems to be proving difficult to optimize for good performance under all conditions. And neither Broadcom nor Linksys seem to have cracked the code in the 610N.

Since I wasn't able to test the 600N and 610N under the same conditions, I can't conclusively say that the 610N's wireless performance is better or worse than the 600N's. But if you're looking for a reasonably-priced dual-band, dual-radio draft 11n router, the 610N continues the 600N's tradition of being the only viable game in town.

Tags: 802.11n, Linksys, WiFi,

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