SDN Internet Router (sir)

Fri Jan 6 08:25:08 UTC 2023

Having wanted something similar recently, let me clarify what my desire
was.

I had a 1M FIB device I needed to get some additional life out of, running
ipv4 and ipv6.  It also was running short on memory.  This particular
device had 3 connections to the rest of the net which were running BGP, one
of which was a peering connection at an exchange so quite a few bgp
sessions on that one link.

What I would have liked to see is a solution to offload the BGP itself onto
a VM which would then aggregate the routes before installing into the FIB.
   Just aggregating prefixes in my case would have taken care of what I
wanted to do.   Instead,  I ended up pointing default at the transit
providers and taking only the peering routes, and hoped the preferred
transit provider didn't end up with odd breakage too often before we could
get a replacement device sourced and installed which took way too long.

There are quite a lot of multihomed situations I've seen where the edge
device simply can't do a full routing table and buying something that can
isn't really possible due to budget or other constraints.  Pointing default
at one of the upstreams works until connectivity breaks from that upstream
to the rest of the net.   A solution which could dynamically look at the
bgp reachability and install a default route to whichever upstream was
better connected and then install additional routes overriding that default
to some predefined maximum number of prefixes would be useful.  That way
you could gain the benefits of multi homing without needing a large fib
device.   With some intelligent rules you could also ensure that the
overriding routes first covered any prefixes that didn't seem reachable
through the default provider, then additional rules could be prioritized
based on various other metrics so you'd get similar performance to a full
internet routing table with significantly fewer routing entries.

In the end though,  I do expect that the hassle of setting up and managing
a solution like this is likely to result in most people deciding that it
isn't worth the extra complexity just to avoid upgrading a low fib device
where a larger one is really needed.

On Thu, Jan 5, 2023, 9:31 AM Mel Beckman <mel at beckman.org> wrote:

> 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 at 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
> Intelligent Computing Solutions <http://www.ics-il.com/>
> <https://www.facebook.com/ICSIL>
> <https://plus.google.com/+IntelligentComputingSolutionsDeKalb>
> <https://www.linkedin.com/company/intelligent-computing-solutions>
> <https://twitter.com/ICSIL>
> Midwest Internet Exchange <http://www.midwest-ix.com/>
> <https://www.facebook.com/mdwestix>
> <https://www.linkedin.com/company/midwest-internet-exchange>
> <https://twitter.com/mdwestix>
> The Brothers WISP <http://www.thebrotherswisp.com/>
> <https://www.facebook.com/thebrotherswisp>
> <https://www.youtube.com/channel/UCXSdfxQv7SpoRQYNyLwntZg>
> ------------------------------
> *From: *"Tom Beecher" <beecher at beecher.cc>
> *To: *"Mike Hammett" <nanog at ics-il.net>
> *Cc: *"Mel Beckman" <mel at beckman.org>, "NANOG" <nanog at 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 at 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
>> Intelligent Computing Solutions <http://www.ics-il.com/>
>> <https://www.facebook.com/ICSIL>
>> <https://plus.google.com/+IntelligentComputingSolutionsDeKalb>
>> <https://www.linkedin.com/company/intelligent-computing-solutions>
>> <https://twitter.com/ICSIL>
>> Midwest Internet Exchange <http://www.midwest-ix.com/>
>> <https://www.facebook.com/mdwestix>
>> <https://www.linkedin.com/company/midwest-internet-exchange>
>> <https://twitter.com/mdwestix>
>> The Brothers WISP <http://www.thebrotherswisp.com/>
>> <https://www.facebook.com/thebrotherswisp>
>> <https://www.youtube.com/channel/UCXSdfxQv7SpoRQYNyLwntZg>
>> ------------------------------
>> *From: *"Tom Beecher" <beecher at beecher.cc>
>> *To: *"Mike Hammett" <nanog at ics-il.net>
>> *Cc: *"Mel Beckman" <mel at beckman.org>, "NANOG" <nanog at 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 at 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
>>> Intelligent Computing Solutions <http://www.ics-il.com/>
>>> <https://www.facebook.com/ICSIL>
>>> <https://plus.google.com/+IntelligentComputingSolutionsDeKalb>
>>> <https://www.linkedin.com/company/intelligent-computing-solutions>
>>> <https://twitter.com/ICSIL>
>>> Midwest Internet Exchange <http://www.midwest-ix.com/>
>>> <https://www.facebook.com/mdwestix>
>>> <https://www.linkedin.com/company/midwest-internet-exchange>
>>> <https://twitter.com/mdwestix>
>>> The Brothers WISP <http://www.thebrotherswisp.com/>
>>> <https://www.facebook.com/thebrotherswisp>
>>> <https://www.youtube.com/channel/UCXSdfxQv7SpoRQYNyLwntZg>
>>> ------------------------------
>>> *From: *"Mel Beckman" <mel at beckman.org>
>>> *To: *"Mike Hammett" <nanog at ics-il.net>
>>> *Cc: *"NANOG" <nanog at 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 at 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
>>> Intelligent Computing Solutions <http://www.ics-il.com/>
>>> <https://www.facebook.com/ICSIL>
>>> <https://plus.google.com/+IntelligentComputingSolutionsDeKalb>
>>> <https://www.linkedin.com/company/intelligent-computing-solutions>
>>> <https://twitter.com/ICSIL>
>>> Midwest Internet Exchange <http://www.midwest-ix.com/>
>>> <https://www.facebook.com/mdwestix>
>>> <https://www.linkedin.com/company/midwest-internet-exchange>
>>> <https://twitter.com/mdwestix>
>>> The Brothers WISP <http://www.thebrotherswisp.com/>
>>> <https://www.facebook.com/thebrotherswisp>
>>> <https://www.youtube.com/channel/UCXSdfxQv7SpoRQYNyLwntZg>
>>>
>>>
>>>
>>
>
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