I know about a couple of these. Some use very specific compression based on external knowledge—like that this is all office xml documents, with freedom to study

I know about a couple of these. Some use very specific compression based on external knowledge—like that this is all office xml documents, with freedom to study the set of the last year’s documents. Some work by eliciting pessimal behavior from TCP flows sharing the same link—they’re really bad neighbors! Some use a family of different approaches to cope with different performance domains. Some use intermediate relays to cut the bandwidth-deat product by reducing delay. But the big key is this: standard tools aren’t even trying to be good at this. They’re aimed at making an Internet work, not at optimizing and particular flow.