[FROG] A study on community-triggered updates in BGP

[Donald Sharp]

The sending of duplicate update packets I would consider it an
undesirable behavior but I would probably not call it a feature or a
bug in the strictest sense of the words.  Maria's answer over on the
bird email alias
https://bird.network.cz/pipermail/bird-users/2020-October/014923.html
has a very good take in my opinion.

I would like this behavior to be modified in FRR.  The overhead of not
building a duplicate update packet -vs- building a update packet and
sending it to a peer to have it decoded and nothing done with it is
far less computationally across the entirety of the network.

Thanks for pointing this out!  I actually saw this discussion on the
bird alias earlier in the week and built a small testbed to show this
behavior within FRR on friday night.  Just another aspect of how we
can help each other out to build a better system.

donald

On Sat, Oct 17, 2020 at 7:15 PM Thomas Krenc <tkrenc at nps.edu> wrote:
>
> Dear FRRouting users and developers,
>
> As a team of researchers from NPS and TU Berlin, we are investigating
> the impact of BGP community attributes on the update behavior between ASes.
>
> We find that when a route is associated with multiple distinct community
> attributes it does not only lead to multiple announcement at the tagging
> AS, but also at neighboring ASes, if communities are not filtered
> properly. This behavior is wide-spread.
>
> In order to better understand our observations, we have performed a
> series of laboratory experiments using Cisco IOS, Junos OS, as well as
> the routing daemons BIRD and FRRouting.
>
> We find that - by default - all routers generate announcements with
> changing community attributes, even when other attributes do not change.
> In addition, when communities are filtered at egress, Cisco, BIRD and
> FRRouting send duplicate announcements (Juniper does not).
>
>     Is this side-effect known to the FRRouting community and would you
> consider it a bug or a feature?
>
> Since our findings are limited to observations in public data as well as
> few router implementations, we would like to share our research and
> kindly ask you to have a look at:
>
>     https://www.cmand.org/communityexploration/
>
> There, we provide some resources documenting our research, as well as
> open questions. We greatly appreciate any feedback and insights you can
> offer. Also, please don't hesitate to contact us directly:
>
>     communityexploration AT cmand DOT org
>
> best regards
>
> Thomas Krenc
> Postdoctoral Researcher
> Naval Postgraduate School
>
>
> _______________________________________________
> frog mailing list
> frog at lists.frrouting.org
> https://lists.frrouting.org/listinfo/frog