We hit half-million: The Cidr Report

Tue Apr 29 16:22:36 UTC 2014

> The remainder of the prefixes (45%) shares the same origin AS and the same path.
> The could be TE prefixes, but as they are identical to their covering
> aggregate its hard to appreciate exactly what the engineering intent may be. I could
> make a wild guess and call these 45% of more specifics to be an act of senseless routing
> vandalism. ( :-) ) This number has been steady as a % for the past three years.

This could easily be TE, and a type of TE which would be trivially fixed.

Let's take a simple example of a network with a /22 and 4 POPs. They have the same transit provider(s) at all 4 POPs and a small backbone to connect them. Each POP gets a /24.

A not-ridiculous way to force their transit provider to carry bits instead of clogging their backbone while still ensuring redundancy would be to announce the /22 at all four POPs and the individual /24 at each individual POP. This creates four /24s and a covering /22 with exactly the same path, but still has "use" as TE.

Of course, it would be trivial for the network to clean up their act by attacking no-export to the /24s. But some people either do not know it exists, know how it works, or know BGP well enough to understand it would not harm them. Or maybe they are just lazy: "What's 3 extra prefixes in half a million?"

The answer to the last question is, frankly, nothing. But 3 prefixes for 30K ASNs is an ass-ton. (That's a technical term meaning "lots & lots".)

This is a good time for a marketing effort. Let's see if we can get the table back under 500K. Everyone check your announcements. Are you announcing more specifics and a covering aggregate with the same path? Can you delete the more specific? Can you add no-export or another community to keep the more specifics from the global table?

If you are unsure, ask. I think it would be rather awesome if we saw a quick reversal in table growth and went back under 500K, even if it was short lived. ESPECIALLY if we can do it before we hit 512K prefixes. Would prove the community still cares about, well, the community, not just their own network. Because on the Internet, "your network" is part of the "community", and things that harm the latter do harm the former, even if it is difficult for you to see sometimes.

Who will be the first to pull back a few prefixes?

-- 
TTFN,
patrick

On Apr 29, 2014, at 03:31 , Geoff Huston <gih at apnic.net> wrote:

> 
> On 29 Apr 2014, at 12:39 pm, Valdis.Kletnieks at vt.edu wrote:
> 
>> On Mon, 28 Apr 2014 21:59:43 -0400, "Patrick W. Gilmore" said:
>>>> On Apr 28, 2014, at 19:41, Chris Boyd <cboyd at gizmopartners.com> wrote:
>>>> I'm in the middle of a physical move.  I promise I'll take the 3 deagg'd
>>>> /24s out as soon as I can.
>>> Do not laugh. If everyone who had 3 de-agg'ed prefixes fixed it, the table
>>> would drop precipitously. We all have to do our part.
>> 
>> Do we have a handle on what percent of the de-aggrs are legitimate attempts
>> at TE, and what percent are just whoopsies that should be re-aggregated?
>> 
> 
> I made a shot at such a number in a presentation to NANOG in Feb this year
> (http://www.potaroo.net/presentations/2014-02-09-bgp2013.pdf)
> 
> 
> If you assume that Traffic Engineering more specifics share a common origin AS with the
> covering aggregate, then around 26% of more specifics are TE advertisements. This 
> number (as a percentage) has gwon by 5% over the past three years
> 
> 
> If you assume that Hole Punching more specifics are more specifics that use a different
> origin AS, then these account for 30% of the more specifics in today's routing table.
> This number has fallen by 5% over the past three years.
> 
> The remainder of the prefixes (45%) shares the same origin AS and the same path.
> The could be TE prefixes, but as they are identical to their covering
> aggregate its hard to appreciate exactly what the engineering intent may be. I could
> make a wild guess and call these 45% of more specifics to be an act of senseless routing
> vandalism. ( :-) ) This number has been steady as a % for the past three years.
> 
> Interestingly, it's the hole punching more specifics that are less stable, and the
> senseless routing vandalism more specifics that are more stable than the average.
> 
> thanks,
>   Geoff