Brian's Brain

In his critique of my networking hands-on cover story published earlier this year, Maury Wright pointed out that while my testing was quite comprehensive, I might want to revisit the project at a later date and (as I mentioned here) supplement my existing results data set by simultaneously pumping multiple multimedia streams through each network spur. Specifically, in his past experience with powerline networking (albeit not with the latest-generation HomePlug AV), he'd noticed disproportionate degraded performance when multiple traffic sources were simultaneously contending for the available network resource, even when benchmarking results suggested that there was sufficient available bandwidth to handle them all.

Yesterday afternoon, I inadvertently had the opportunity to put Maury's suggestion into practice, and the results weren't terribly encouraging. It's been snowing for nearly 24 straight hours up here in the Sierras, and I directed two co-workers from EDN's Waltham, MA office to my home's webcams (one pointed out the front window, the other out the back) so that they could also enjoy the Christmas-in-October view. The webcams are D-Link DCS-5300s, tethered to my Linksys WRT54GC router via Actiontec's HPE200AV HomePlug AV adapters running the latest production firmware release from Intellon.

As you'll see from the above snapshot of Linksys' utility (which is HomePlug AV vendor-agnostic), the adapters report robust PHY bandwidth over my fairly modern (20 year old) and diminutive home's power grid. The webcams default to UDP streaming if they detect sufficient network bandwidth, as well as protocol support at the destination. They auto-downgrade to TCP and (worst-case) video-only HTTP on an as-needed basis.

One of us controlled each webcam's pan-and-tilt feature via its ActiveX-based web browser interface, while all three of us observed the results. Unfortunately, after a few minutes of fun, both webcams stopped responding to access requests. I initially thought the webcams had locked up, as I'd had various problems with them in the past (which you'll be able to read all about in my upcoming November 22 feature article). But then I noticed that the corresponding HomePlug AV adapters had also disappeared from view in the Linksys utility.

Disconnecting each HomePlug AV adapter from its power outlet, then re-plugging it in, restored normal adapter (and webcam) function. I'd never seen a problem like this before; then again, I'd never tried simultaneously viewing a webcam from multiple LAN and WAN clients, either. Ironically, since we were all receiving the exact same data, the bandwidth demands could have been lessened if the webcam/router combination supported broadcast streaming, but my setup isn't that sophisticated.