Destination Preference Attribute for BGP

Mon Aug 21 15:44:18 UTC 2023

>
> So, while this all sounds good, without any specifics on vendor, box,
> code, code revision number, fix, year it happened, current status, e.t.c.,
> I can't offer any meaningful engagement.
>

If you clicked Matt's link to the Google search, you could tell from the
results what vendor , model, and year it was pretty quickly.

>  It's just not moving the needle on this thread, though.
>

Assertion Made : "Networks can scrub communities for memory or convergence
reasons."
Others : "That doesn't seem like a concern. "
Matt : "Here was a real situation that happened where it was a concern, and
the specifics on the reason why."

How is that not 'moving the needle? Because you didn't get full transcripts
of his conversation with the vendor?.  I'm sure a lot of people didn't even
know that hashing / memory hotspotting was even a thing. Now they do.

On Sat, Aug 19, 2023 at 1:17 AM Mark Tinka <mark at tinka.africa> wrote:

>
>
> On 8/19/23 00:22, Matthew Petach wrote:
>
> Hi Mark,
>
> I know it's annoying that I won't mention specifics.
> Unfortunately, the last time I mentioned $vendor-specific information on
> NANOG, it was picked up by the press, and turned into a multimillion dollar
> kerfuffle with me at the center of the cross-hairs:
>
> https://www.google.com/search?q=petach+kablooie&sca_esv=558180114&nirf=petah+kablooie&filter=0&biw=1580&bih=1008&dpr=2
>
> After that, I've learned it's best to not name specific very-big-name
> vendors on NANOG posts.
>
> What I *can* say is that this was one of the primary vendors in the
> Internet backbone space, running mainstream code.
> The only reason it didn't affect more networks was a function of the
> particular cluster of signalling communities being applied to all inbound
> prefixes, and how they interacted with the vendor's hash algorithm.
>
> Corner cases, while valid, do not speak to the majority. If this was a
>> major issue, there would have been more noise about it by now.
>>
>
> I prefer to look at it the other way; the reason you didn't hear more
> noise about it, is that we stubbed our toes on it early, and had relatively
> fast, direct access to the development engineers to get it fixed within two
> days.  It's precisely *bcause* people trip over corner cases and get them
> fixed that they don't end up causing more widespread pain across the rest
> of the Internet.
>
>
>> There has been quite some noise about lengthy AS_PATH updates that bring
>> some routers down, which has usually been fixed with improved BGP code. But
>> even those are not too common, if one considers a 365-day period.
>>
>
> Oh, absolutely.  Bugs in implementations that either crash the router or
> reset the BGP session are much more immediately visible than "that's odd,
> it's taking my routers longer to converge than it should".
>
> How many networks actually track their convergence time in a time series
> database, and look at unusual trends, and then diagnose why the convergence
> time is increasing, versus how many networks just note an increasing number
> of "hey, your network seems to be slowing down" and throw more hardware at
> the problem, while grumbling about why their big expensive routers seem to
> be less powerful than a *nix box running gated?
>
> I suspect there's more of these type of "corner cases" out there than you
> recognize.
> It's just that most networks don't dig into routing performance issues
> unless it actually breaks the router, or kills BGP adjacencies.
>
> If you *are* one of the few networks that tracks your router's convergence
> time over time, and identifies and resolves unexpected increases in
> convergence time, then yes, you absolutely have standing to tell me to pipe
> down and go back into my corner again.  ;D
>
>
> So, while this all sounds good, without any specifics on vendor, box,
> code, code revision number, fix, year it happened, current status, e.t.c.,
> I can't offer any meaningful engagement.
>
> We all run into odd stuff as we operate this Internet, but the point of a
> list like this is to share those details so we can learn, fix and move
> forward.
>
> Your ambiguity does not lend itself to a helpful discussion,
> notwithstanding my understanding of your caution.
>
> I am less concerned about keeping smiles on vendors' faces. I tell them in
> public and private if they are great or not. But since you've been burned,
> I get. It's just not moving the needle on this thread, though.
>
> Mark.
>
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