More Routers Needed For Multiple ISPs

BRIAN SANTO

The ISP access agreement imposed on the AOL Time Warner merger could be an unexpected windfall for router companies.

There are several ways to provide access to multiple Internet service providers, but the approach Time Warner Cable has chosen will require the company to slightly modify its network architecture to include what TWC is calling a "policy router."

The name refers to its function rather than any fundamentally new sort of router. Existing routers can fulfill the function, which is to help identify specific users so they can be connected to their ISPs immediately.

TWC will require one policy router in each of its 39 divisions. In many divisions, the company has routers already in place that can be used for policy routing; in some cases, Road Runner has installed or is installing such routers, while new routers might have to be purchased for others, says Michael Adams, the company's VP-network engineering. Adams' comments were made during a talk called "Planning for Multiple ISP Deployment" at the SCTE Emerging Technologies conference in New Orleans last week.

TWC is still evaluating its network, but there will be instances where the company will need to install some new routers, which Adams says could cost $200,000 to $300,000 each, depending on how they are configured. He says the company is now in the process of evaluating several commercial routers for their suitability as policy routers.

(There are also some additional costs associated with changes and upgrades in the TWC's DHCP routers and management/provisioning systems.)

The basic issue TWC has to contend with - and which other cable operators will have to deal with also - is how to design a system that allows for multiple ISPs. TWC has made a few choices and a few assumptions that dictated the path it would take. TWC also made the assumption that customers would choose to get service from a single ISP. The company wanted to continue to emulate the "always on" experience people get with DSL.

In other words, the company doesn't want its customers to have to go through a process of selecting their ISPs each time they re-boot or try to connect to the Internet. To avoid that, TWC needs some way to identify the customer, which it has to do by somehow recognizing the computer the customer is using.

Connecting to the Internet is, by nature, an IP service, which means each device hooked to the Net has to have its own IP address. TWC can't use that address, because it changes. Since each ISP has only a limited pool of IP addresses, they must draw an unused address from their pools and temporarily assign it to a customer for the customer's session connected to the Internet.

Every computer does have, however, a unique media access control (MAC) number, so TWC has resolved to use that. In short, it is the job of the policy router to identify the MAC addresses of the computers that customers use to log on and store them, and then each subsequent time any given customer logs on, to associate that specific MAC address with the specific ISP the customer has chosen. This automatic association provides the appearance of an "always on" connection.

While this is admittedly complex, the real challenge, Adams says, is changes in the back office, because this approach forces the cable operator to assume greater management responsibilities.

The cable operator puts itself in the position of having to monitor and meter Internet usage. This has several ramifications. Among them, the cable operator and each ISP will have to agree on an approach to billing the customer - Do they get a single bill from the cable operator, or two bills, one from the cable operator, another from the ISP?

The approach TWC is taking also opens up several questions. What happens when a customer shares a single ISP account among two or more computers? What happens when a customer has more than one ISP account? What happens if the ISP offers video services, and connections are required not just to the computer, but also to the TV? Adams is confident most of these issues can be dealt with, but acknowledges those circumstances complicate the matter.