From: Remi Pommarel <repk@triplefau.lt>
To: b.a.t.m.a.n@lists.open-mesh.org
Subject: Re: [PATCH RFC 0/2] Better throughput estimation on half duplex interfaces
Date: Thu, 28 Sep 2023 21:16:36 +0200 [thread overview]
Message-ID: <ZRXRFFATYjEvIeVb@pilgrim> (raw)
In-Reply-To: <15370864.uLZWGnKmhe@rousseau>
On Thu, Sep 28, 2023 at 08:10:48PM +0200, Marek Lindner wrote:
> On Thursday, 28 September 2023 18:48:20 CEST Remi Pommarel wrote:
> > > If the direct path from Orig0 to Orig2 is better than the path over Orig1
> > > the metric should reflect that.
> >
> > In the example there is no direct path from Orig0 to Orig2, the only
> > way for Orig2 to reach Orig0 is by going through Orig1.
>
> If there is only one path, the computed metric does not matter at all.
>
> If there are alternative paths (as you saying below "Orig0 and Orig2 are
> connected via a 100Mbps"), batman-adv has to find the best of the existing
> paths.
Yes and it currently fails to do that as explained below.
>
>
> > Let's say that :
> >
> > - Orig0 and Orig1 are connected via a 200Mbps WiFi mesh link (mesh0)
> > - Orig1 and Orig2 are connected via a 110Mbps WiFi mesh link (mesh0)
> > - Orig0 and Orig2 are connected via a 100Mbps WiFi mesh link (mesh0)
> >
> > With the current implementation the originator table of Orig2 will show
> > something like the following:
> >
> > $ batctl o
> > Originator last-seen ( throughput) Nexthop [outgoingIF]
> > * Orig0-Main-Mac 0.220s ( 110) Orig1-mesh0-Mac [ mesh0 ]
> > Orig0-Main-Mac 0.220s ( 100) Orig1-mesh0-Mac [ mesh0 ]
> >
> > So best path for Orig2 to Orig0 would go through Orig1 with an expected
> > throughput of 110Mbps. But such a throughput cannot be reached because
> > Orig1 has to forward packet from and to the same WiFi interface.
>
> Correct. Looking at your example where is the problem with the store & forward
> penalty?
The problem is that the wrong path is selected.
The best one should be the direct one. Because going through Orig1, 110Mbps
would never be bereached due to the store & forward penalty on Orig1 and
the real throughput will be below the direct path (around 80Mbps).
>
> Or in other words: What scenario are your patches aiming to improve?
>
With both patches this
* Orig0-Main-Mac 0.220s ( 110) Orig1-mesh0-Mac [ mesh0 ]
Orig0-Main-Mac 0.220s ( 100) Orig0-mesh0-Mac [ mesh0 ]
will instead be
Orig0-Main-Mac 0.220s ( 80) Orig1-mesh0-Mac [ mesh0 ]
* Orig0-Main-Mac 0.220s ( 100) Orig0-mesh0-Mac [ mesh0 ]
Fixing the best path selection.
Thanks
--
Remi
next prev parent reply other threads:[~2023-09-28 19:17 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-28 12:39 [PATCH RFC 0/2] Better throughput estimation on half duplex interfaces Remi Pommarel
2023-09-28 12:39 ` [PATCH RFC 1/2] batman-adv: Keep half duplex penalty on OGM receiving side also Remi Pommarel
2023-09-28 12:39 ` [PATCH RFC 2/2] batman-adv: Better half duplex penalty estimation Remi Pommarel
2023-10-14 5:10 ` Linus Lüssing
2023-10-14 6:03 ` Linus Lüssing
2023-10-18 19:58 ` Remi Pommarel
2023-10-18 21:37 ` Nicolas Escande
2023-10-14 6:24 ` Linus Lüssing
2023-09-28 15:33 ` [PATCH RFC 0/2] Better throughput estimation on half duplex interfaces Marek Lindner
2023-09-28 16:48 ` Remi Pommarel
2023-09-28 17:54 ` Remi Pommarel
2023-09-28 18:10 ` Marek Lindner
2023-09-28 19:16 ` Remi Pommarel [this message]
2023-10-03 21:06 ` Marek Lindner
2023-10-11 8:55 ` Remi Pommarel
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