Re: SDN Internet Router (sir)

[Mel Beckman <mel () beckman org>]

Mike,

Your original question was:

“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?”

People then, respectfully, tried to clarify your request or explain why placing routes in a low-FIB capacity device 
isn’t seen as being beneficial. Only now have you added the desire to simply have “more than a default route” in such a 
router.

You can, of course, have more than a default route today - e.g., through local pref and BGP communities for things such 
as company routes. You haven’t said what you define as “more intelligently”, so perhaps you can more clearly explain 
the problem you see with the current BGP capabilities via some examples.

 -mel

On Jan 5, 2023, at 8:02 AM, Mike Hammett <nanog () ics-il net> wrote:


Then please bless the world with the right way.

You acknowledge that not every router in a network needs to be fully DFZ capable, but then crap on my desire to have 
more than a default route in one.



-----
Mike Hammett
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________________________________
From: "Tom Beecher" <beecher () beecher cc>
To: "Mike Hammett" <nanog () ics-il net>
Cc: "Mel Beckman" <mel () beckman org>, "NANOG" <nanog () nanog org>
Sent: Thursday, January 5, 2023 9:55:38 AM
Subject: Re: SDN Internet Router (sir)

"The right tool for the job" gets into a religious argument in assuming that one's way to do the job is the only 
reasonable way to do the job

I disagree that it's religious. I completely agree there are locations in networks that having full DFZ capable routers 
doesn't make technical or economic sense. But there have long been different products for those different use cases.

To perhaps explain my viewpoint better,(and perhaps I didn't properly comprehend the problem you're aiming to solve) :

If you are trying to use SDN stuff to shuffle routes on and off a box because you have the wrong sized routers in 
place, then I would argue you're doing it wrong.

If you are trying to use SDN stuff to (as Christopher mentioned) make decisions that are not strictly LPM, and the 
equipment you have cannot do that, then that's different and entirely reasonable.

If the second use case is more of what you were asking, then I apologize for misunderstanding.



On Thu, Jan 5, 2023 at 9:57 AM Mike Hammett <nanog () ics-il net<mailto:nanog () ics-il net>> wrote:
"The right tool for the job" gets into a religious argument in assuming that one's way to do the job is the only 
reasonable way to do the job.

Large networks historically have a very poor (IMO) model of gigantic iron in a few locations, which results in 
sub-optimal routing for the rest of their network between those large POPs. I've heard time and time again that someone 
buying service from a major network in say New Orleans has a first hop of Dallas or Atlanta. I agree that full-route 
capable routers need to be in the large, central locations, but it isn't cost effective to have them at every POP, 
especially if you're a last-mile provider.

I'd go into more examples of where it doesn't make sense to have full-route routers everywhere, but I'm afraid that the 
Internet would then focus on the examples instead of the core idea of intelligently putting routes into the FIBs of 
low-FIB routers throughout my network.



-----
Mike Hammett
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________________________________
From: "Tom Beecher" <beecher () beecher cc<mailto:beecher () beecher cc>>
To: "Mike Hammett" <nanog () ics-il net<mailto:nanog () ics-il net>>
Cc: "Mel Beckman" <mel () beckman org<mailto:mel () beckman org>>, "NANOG" <nanog () nanog org<mailto:nanog () nanog 
org>>
Sent: Wednesday, January 4, 2023 7:36:58 AM
Subject: Re: SDN Internet Router (sir)

Disagree that it’s a line in the sand. It’s use the right tool for the job.

If a device is low FIB, it’s that way for a reason. There are plenty of ways to massage that with policy and software, 
depending on capabilities , but at the end of the day, trying to sort 10 pounds of shit to store in a 5 pound bag is 
eventually going to end up the same way.

On Tue, Jan 3, 2023 at 13:18 Mike Hammett <nanog () ics-il net<mailto:nanog () ics-il net>> wrote:
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
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________________________________
From: "Mel Beckman" <mel () beckman org<mailto:mel () beckman org>>
To: "Mike Hammett" <nanog () ics-il net<mailto:nanog () ics-il net>>
Cc: "NANOG" <nanog () nanog org<mailto:nanog () nanog org>>
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 () ics-il net<mailto:nanog () ics-il net>> wrote:


https://github.com/dbarrosop/sir

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
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