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

Thomas Krenc tkrenc at nps.edu
Thu Oct 22 00:06:26 UTC 2020


Hi donald,

This is all very interesting. I'm glad our findings are useful.

I was wondering if FFR supports some kind of suppression logic that
needs to be explicitly enabled,  similar to BIRDs "export able on". I
searched the Internet but could not find any answers.

best regards
Thomas

On 10/18/20 4:56 AM, Donald Sharp wrote:
> NPS WARNING: *external sender* verify before acting.
>
>
> 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





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