Re: Distributed Router Fabrics

[David Sinn <dsinn () uw edu>]

From experience I can tell you that once you fully operationalize the pizza box model you will never go back to the 
chassis model. Why would you trade, open, standards based model for interconnect (OSPF and BGP work great at scale) for 
proprietary black boxes that do stupid router tricks to make a bunch of discrete components pretend to be one along 
with giving you the benefit of a huge blast-radius when the software inevitably breaks? Distributed ARP/ND, solved. 
Actually distributed BFD (not "it's all running on one line card because customers like LACP bundles spread between 
line cards and that's really hard to distribute reliably), solved. Pizza box models means the boxes are fungible. So 
you can competitively bid between multiple suppliers and pick and choose who you want to buy from depending on what is 
the most important thing at the time (delivery dates? price? which of them is annoying you the least at that moment in 
time?). They are also infinitely more scaleable(*) than any big chassis model. State of the art 5 years ago had 
Internet edge systems deploying with 8k of 400G ports and datacenter deployments with 65k 400G ports using the same 
fundamental design.

The real downside: vendors don't like the flexibility that it affords the customer and the meaninglessness of 
differentiation between vendors that it drives the operators to avoid.

David

(*) - Among some of the critical things to get right from the outset is what peak scale you want to have for the fabric 
because recabling is not something to be taken lightly...


On Dec 23, 2024, at 7:15 AM, Mike Hammett <nanog () ics-il net> wrote:

"Obviously, at some point, buying a big chassis..."

Actually, as I read more about it and watch more videos about it, it seems like that isn't necessarily true. The claims 
they have at the top end surpass what any chassis platform I've seen is capable of, though I don't know that they 
actually have pushed the upper bounds of what's possible in the real world.



-----
Mike Hammett
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________________________________
From: "Mike Hammett" <nanog () ics-il net<mailto:nanog () ics-il net>>
To: "NANOG" <nanog () nanog org<mailto:nanog () nanog org>>
Sent: Friday, December 20, 2024 10:06:36 AM
Subject: Distributed Router Fabrics

I've noticed that the whitebox hardware vendors are pushing distributed router fabrics, where you can keep buying pizza 
boxes and hooking them into a larger and larger fabric. Obviously, at some point, buying a big chassis makes more 
sense. Does it make sense building up to that point? What are your thoughts on that direction?



-----
Mike Hammett
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