New Algorithm Offers Hope for Old Routers
That benefit is balanced against the fact that employing the algorithm means each router has less precise information about what the state of the network actually is.
Each router with XL would maintain data about its neighbors' shortest path tree -- how its neighbor views the network -- and uses that to determine whether to forward path updates. That would increase the amount of data routers keep, but Savage says his team thinks that additional data is very small.
In big networks, overall performance is limited by the slowest router. "That's the router you're waiting for so the new network configuration can converge," Savage says.
Because buying cycles for routers may vary within very large networks, older slower routers can have a big impact, he says. "Scalability may be limited by stuff you bought 10 years ago that you can't afford to replace yet," he says.
The algorithm is compatible with Intermediate System-to-Intermediate System and Open Shortest Path First link-state routing, he says, which means the software upgrade containing the algorithm could be deployed incrementally and would interoperate with existing router protocols. The goal in these networks would be to optimize paths based on a given parameter such as latency or bandwidth, he says.
Getting XL into practical use would require router makers to incorporate it in their software, Savage says. "It would need to be embraced by vendors. If Cisco picked it up it would have impact," he says.
He has already briefed Cisco -- which helped fund his research through the Center for Network Systems.