A brief mention of Broadcom ASIC families in the Networking Hardware/Software Disaggregation in 2022 blog post triggered an interesting discussion of ASIC features and where one should use different ASIC families.

Like so many things in life, ASIC design is all about tradeoffs. Usually you’re faced with a decision to either implement X (whatever X happens to be), or have high-performance product, or have a reasonably-priced product. It’s very hard to get two out of three, and getting all three is beyond Mission Impossible.

Last week I described some of the data center switching ASIC design tradeoffs and the ASIC families Broadcom created to fit somewhere in that multi-dimensional space.

Next step: how could you design your data center fabric to make the most out of them? To keep things simple, we’ll build a typical leaf-and-spine fabric with a WAN edge layer (sometimes called border leaf switches).

A few weeks ago I wrote about tradeoffs vendors have to make when designing data center switching ASICs, followed by another blog post discussing how to select the ASICs for various roles in data center fabrics.

You REALLY SHOULD read the two blog posts before moving on; here’s the buffer-related TL&DR for those of you ignoring my advice ;)

The last time I spent days poring over vendor datasheets collecting information for the overview part of Data Center Fabrics webinar a lot of 1RU data center leaf switches came in two form factors:

• 48 low-speed server-facing ports and 4 high-speed uplinks
• 32 high-speed ports that you could break out into four times as many low-speed ports (but not all of them)

I expected the ratios to stay the same when the industry moved from 10/40 GE to 25/100 GE switches. I was wrong – most 1RU leaf data center switches based on recent Broadcom silicon (Trident-3 or Trident-4) have between eight and twelve uplinks.