DPI - what's in a name?

One my my favourite pet peeves regarding the public perception of this industry is the way the term Deep Packet Inspection is used to describe any sort of device that processes layer seven, no matter what it does. Consider the following three implementations:

• A WAN optimization appliance with protocol awareness / on-the-fly data compression.
• A protocol aware bandwidth limiting device, a.k.a traffic shaper.
• Ad insertion in random web pages. Yes, this is plain evil.

I've seen all of those referred to as DPI, despite them having almost nothing in common when it comes to what task they actually perform.

Let's paraphrase this using another type of traffic - automotive. You wouldn't refer to the concepts of toll roads, bus lanes and congestion charges as all being Road Traffic Management, right? Yet this is pretty much what's happening with DPI.

The industry itself isn't helping much either, as new prefixes and suffixes are invented by some vendors just to further add to the confusion. We've got Qosmos and their ixDPI, more than one vendor is pushing or has been pushing DFI, etc. In a way, I can understand this - since world + dog does DPI, I'm guessing they're trying to differentiate 'our DPI' from 'their DPI'. Thankfully, I'm not a vendor and not trying to sell anything. 

Bottom line: Be careful about thinking of DPI gear as one single class of gear. The technical implementation depends on what you need to do with the traffic, the positioning in the network depends on what you need to do with the traffic and one device really isn't anything like the next. Even if you can do horribly nasty stuff with some devices, the concept all by itself isn't necessarily evil.

Someone else who blogged about this and more is Travis Dawson (who works for Sprint but opines all on his own). You can find his take on it from a service prodier perspective here.