SDN Internet Router (sir)

Mel Beckman mel at
Tue Jan 3 16:57:34 UTC 2023

It’s not a problem, due to cheap, plentiful high-speed memory and rapid prefix search silicon in backbone routers. The entire Internet routing table consumes at most a few gigabytes when fully structured (and only a few hundred Mbytes stored flat).  That’s less memory than your average laptop sports.

Even in the worst case scenario, where every network decides to announce only its most specific prefixes, the BGP backbone would temporarily enter an oscillating state that generates a large number of routing updates into the inter-domain routing space. In this case, BGP route damping will quickly suppress the crazies while  the backbone stabilizes.

Small routers should not be taking full tables, since there is no point to them being in the default free zone. For large routers, neither memory nor CPU speed are an issue. High-speed routers operating in the default-free zone have a critical path in the forwarding decision for each packet: it needs to take less than the inter-packet arrival time for minimum-sized IP packets.

This is easy to achieve with today’s hardware. A router line card with an aggregate line rate across all of its point-to-point interfaces of 10Tbps (readily available in today’s gear) can process packets with just a handful of cycles in the FIB Ternary Content Addressable Memory (TCAM) using ASIC-assisted lookups. TCAM is the most expensive component you’re paying for in such a router.  It’s not cheap,  but backbone routers don’t need to be cheap. They just need to not be memory-constrained.

-mel via cell

On Jan 3, 2023, at 7:47 AM, Mike Hammett <nanog at> wrote:

I came across this over the weekend. Given that the project was abandoned six years ago, are there any other efforts with a similar goal (more intelligently placing routes into FIBs of low-FIB capacity devices?

Mike Hammett
Intelligent Computing Solutions<>
Midwest Internet Exchange<>
The Brothers WISP<>
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