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@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
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