I looked at some of these models back in ~2000, but the dotcom boom ended and I didn't get laid off from my day job, so I didn't go trolling for venture capitalists, and my employer sold off their cable companies - since then, the market economics have changed a lot, and routers have started to support enough memory to keep up with the demand. The big questions about the dual-homed customer base are what kind of connectivity they really need - Primary/Backup, or Primary / Backup+extrabandwidth, or truly load-shared, and also what diverse topology is available at the bandwidth they need. For a reasonably large chunk of the ~Y2K market, the answer was "A T1 or two with cable-modem backup", and another chunk was "T3 or bigger, able to afford a telco or CLEC access ring", and most customers were more concerned about backhoe fade, which takes a long time to fix, than about ISP routing glitches, which were less common than 5 years earlier and usually had a much shorter mean time to repair. None of these solutions requires a World Domination Grand Master Plan agreed to buy everybody before it can be deployed - almost anything can start out with two carriers or a transit-buying service provider and then grow. One obvious business model to serve the smaller market was to start a "Slash-19.net", which would get a routable chunk of address space, buy transit from one or two colo providers, and use GRE/IPSEC/L2TPv3 tunnels to connect to the customer through whatever Layer 3 media is available, e.g. cable modems, and optionally use LEC frame or similar transport where available. In the emerging IPv6 world, a tunnel broker service could do something like this. And for equipment-cost reasons, you'd probably use PCs instead of routers as your tunnel servers. Another business model would be for a Tier 1 or Tier 2 ISP to do something similar, using a smaller chunk of their own address space, and using a tunnel server at one of their peering points (or colo space served by another ISP) to handle tunnels through the secondary carrier, such as cable modem companies. Making the addresses work well would require them to use the dual-homing address space for those customers' interfaces instead of whatever probably-geographical schema they use for single-homed customers. The cable companies would be an obvious ISP to do this - they've got control over the most common small diverse access methods, and most of them use PPPoE to connect to their customers so they've already got tunnelling. New wireless access ISPs could do much of the same business. Another model is cooperation between big carriers - if you're doing the N**2 pairs-of-carriers model, there are ~30-35 Tier 1 carriers in the US, so ~1000 address blocks would be enough (if it sounds like a cabal, too bad), and probably a similar but smaller number for Europe. Tier 2 players might need to arrange separate deals with one or more of their upstream Tier1s, so they might double their address space (still only adds ~10K routes), or else they might do an exchange point approach (e.g. somebody like Linx starts Diverse-Linx.) If somebody can get more than two Tier 1s to cooperate, they could do the geographic approach, which can make a major dent with ~50-100 cities in their market.