"B.A.T.M.A.N" b.a.t.m.a.n-bounces@lists.open-mesh.org schrieb am 20.05.2016 15:51:38:
Von: Antonio Quartulli a@unstable.cc An: The list for a Better Approach To Mobile Ad-hoc Networking b.a.t.m.a.n@lists.open-mesh.org Datum: 20.05.2016 15:52 Betreff: Re: [B.A.T.M.A.N.] [PATCHv3 2/6] batman-adv: speed up dat by snooping received ip traffic Gesendet von: "B.A.T.M.A.N" b.a.t.m.a.n-bounces@lists.open-mesh.org
On Fri, May 06, 2016 at 10:58:23AM +0200, Andreas Pape wrote:
Speeding up dat address lookup is achieved by snooping all incoming ip traffic. This especially increases the propability in bla setups that a gateway into a common backbone network already has a fitting dat
entry
to answer incoming ARP requests directly coming from the backbone network thus further reducing ARP traffic in the mesh.
Any IP packet can't be sent if an ARP "handshake" has not been
performed. This
means that when you are snooping an IP packet you have already snooped
an ARP
packet slightly before. In which case do we really win something ?
In case of a static mesh ("static" in terms of non-moving mesh nodes and when the mesh nodes almost always use the same backbone gateways for a common wired backbone) we gain nothing by snooping every packet. The idea came up when I started experimenting with more dynamic setups where the mesh nodes move around with several gateways into a common wired backbone. In this case routing becomes more dynamically and it is not assured that the traffic from/for a mesh node is always routed via the same gateway which has already snooped the arp traffic.
On top of that, don't you think that snooping *every* packet will badly
affect
the performance ? Have you tried measuring the difference ?
I'm aware that this has an impact. I can try to measure the difference using my devices but these results of course are related to the hardware I use. I'm lacking experience if such results can be used to generalize a conclusion.
On the other hand this "feature" was not the root cause to post this patchset. More important for me is the prevention of the "arp reply storms" and the temporary loops between backbone network and the mesh because this generates trouble in my application. If it increases the propability for acceptance I don't care to remove the ip source address snooping from the patchset.
Best regards, Andreas
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