Re: [B.A.T.M.A.N.] about batman performance

Simon Wunderlich
2011-12-06T09:46:00Z

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Hello zb1981gm (btw, do you have a real name?),

On Tue, Dec 06, 2011 at 05:01:13PM +0800, zb1981gm wrote:
> I have used batman on my project for several months.It performs very well,stable especially!
> But,actually,I am not satisfied with the performance of Batman.I found that the bandwidth would drop sharply with the wireless hop increase.
> Now I provide my test result here:
>
> routerA and routerB is composed of compex wp543ahv mainboard (AR7161 platform) and two AR9220 wireless card.Firmware is Openwrt backfire.
> one card is working on 2.4G channel as AP mode,the other is working on 5G channel as mesh backbone
> batman version:2.0

What is batman version 2.0? We have batmand (layer 3), but I guess you are using batman advanced
as you talk about bonding/interface alternating later. These have 0.X (for old releases) or 201X.Y.Z
version schemes (since 2 years). Please clarify.

> notebook1 and notebook2 is equiped with 802.11n usb wireless card which access to the AP mode card of routerA and routerB
>
> channel 1 channel 36 channel 11
> notebook1 --------------- routerA -------------- routerB -------------- notebook2
>
> I use iperf to test bandwidth
>
> notebook1 ----------- routerA 45Mbps
> routerA ----------- routerB 46Mbps
> routerB ----------- notebook2 45Mbps
>
> But the bandwidth between notebook1 and notebook2 remains 8Mbps
> bandwidth between notebook1 and routerB remain 18Mbps

Have you compared this to static routing?

>
> So the conclution is that the bandwidth will be halfed with the 1 hop increase! right?

It should not, as different radio modules are used (and correctly tuned on different channels).
However, you may have a limitation in your CPU power or something else.
You may want to try static routing to find this out.

>
> I also found that the interface alternating mode and bonding mode doesn't take effect
>
> channel 1
> routerA ------------------ routerB
> channel 36
>
> The test result is no difference whatever I configured alternating or bonding or just single radio

To make bonding work, there are a few conditions:
* routers must be equipped with multiple radios which can connect to each other
* activate bonding (batctl bonding 1)
* make sure the transmit qualities are similar (check with batctl o), should not be more than a difference of 50

If everything is fine, you can get a boost of approx. 50%.

>
> According to the batman official site, alternating or bonding mode would improve the performance compared with the single radio mode
>

Yup, it should help. Alternating is not helping in your scenario as far as I understand (your
mesh is only 1 hop long, as notebooks are connected via infrastructure mode). Bonding may
help as described above.

best regards,
Simon

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