The anatomy of a network switch: an eight-port, gigabit glitch

The anatomy of a network switch: an eight-port, gigabit glitch

By eeNews Europe

First on the list is TRENDnet’s TEG-S8, an eight-port GbE switch which was in production in the latter part of the last decade (in May 2008, for example, it was promotion-priced at $15) but has now been discontinued (here’s the associated product support page). The TEG-S8 was notable not only for its aggressive pricing but also for its performance-boosting jumbo frame support, and it served me well (albeit only periodically … I’d phase it in and out of service as my residence locations and network topology needs evolved) for many years.

Recently, however, a few remotely accessible LAN clients mysteriously went offline while I was away on a trip. Upon my return, I noticed that all of the TEG-S8’s front panel "link" and "activity" LEDs were extinguished (echoing an experience I’d had nine months earlier); only the "power" LED was still illuminated. I power-cycled the switch and it came back to life … for a few minutes, at least, until the unwanted switch slumber returned. A few more power cycles resulted in the same undesirable end result, at which point I decided it was time to transition to a switch successor.

Removing four underside-accessible Phillips head screws is all it takes to pry apart the TEG-S8’s plastic case. At the top of the following photo, you can see the eight metal-shielded Ethernet ports, with the TEG-S8 power plug to their left:

Below them, you’ll notice four SOIC-packaged ICs; I thought "DRAM" when I first saw them. A Google search quickly revealed, however, that they’re 1000-Base-T LAN transformers (the G4802CG, to be precise, from Dongguan Mentech Optical & Magnetic), one per two ports. Ironically, however, memory represents the TEG-S8’s fundamental shortcoming versus successor-generation products from both TRENDnet and other suppliers. The TEG-S8’s diminutive 8 kByte buffer could be insufficient when, for example, shuttling packets between GbE and 100 Mbps clients. Take a look at TRENDnet’s now-shipping 8-port GbE "Home Products," in contrast, and you’ll encounter buffer sizes ranging from 128 kBytes to 256 kBytes.

The other object in the system board’s top-side photo that will likely catch your eye is the heatsink in the lower centre, directly above the multi-LED array. SmallNetBuilder’s review says that underneath it is Broadcom’s BCM5398 eight-port switch single-chip controller with integrated PHYs (quick aside: Broadcom and foundry partner UMC announced what they claimed was the "world’s first 8-Port Gigabit Ethernet switch-on-a-chip," the BCM5680, back in May 2000). Thank goodness for SmallNetBuilder’s IC insights; I wasn’t able to pry the heat sink away from the device underneath it in a way that I felt confident would preserve the package markings, and although TRENDnet claims that the TEG-S8 "has been tested and found to comply with FCC and CE Rules," I couldn’t find a FCC ID either on the device itself or its packaging or documentation, which might lead to a bill-of-materials report:

The TEG-S8’s system board bottom side is far less exciting, befitting a cost sensitive, therefore highly integrated, consumer electronics device:

So what happened to the TEG-S8? One possibility that comes to mind is that the "wall wart" power supply is failing, and its diminished current and/or voltage output is inhibiting full operation. I suspect however, that extended exposure to high ambient heat might be behind the TEG-S8’s demise. I’d located the switch in the middle of a three-device stack, in-between my Cisco Linksys E4200 v2 router (below it) and DPC3008 cable modem (above it). Although I’d been careful to not obscure any of the three devices’ airflow vents, their close vertical proximity may have still led to the TEG-S8’s internals getting "cooked." While most of the time when we speak of "power consumption" we’re thinking of electrical bill impacts, it’s also important to consider the potentially formidable thermal effects of power draw excess.

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