SDN Internet Router (sir)

Mike Hammett nanog at
Tue Jan 3 18:15:43 UTC 2023

There are likely more networks with 10 gigabit or less total external capacity than there are with more. 

Creating imaginary lines in the sand doesn't really help anyone. 

Mike Hammett 
Intelligent Computing Solutions 

Midwest Internet Exchange 

The Brothers WISP 

----- Original Message -----

From: "Mel Beckman" <mel at> 
To: "Mike Hammett" <nanog at> 
Cc: "NANOG" <nanog at> 
Sent: Tuesday, January 3, 2023 10:57:34 AM 
Subject: Re: SDN Internet Router (sir) 

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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