Re: [B.A.T.M.A.N.] Fwd: [Babel-users] Fwd: Why we switched to Babel

[Moritz Warning <moritzwarning@web.de>]

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regarding MACs, would it be possible for batman-adv to use hashed MACs?

On 08/08/2015 11:51 PM, Mitar wrote:
> Hi!
> 
> Comments?
> 
> 
> Mitar
> 
> ---------- Forwarded message ----------
> From: Jenny Ryan <tunabananas@gmail.com>
> Date: Fri, Aug 7, 2015 at 11:41 PM
> Subject: [Babel-users] Fwd: Why we switched to Babel
> To: babel-users@lists.alioth.debian.org
> 
> 
> ---------- Forwarded message ----------
> From: "Marc Juul" <juul@labitat.dk>
> Date: Aug 6, 2015 9:58 AM
> Subject: Why we switched to Babel
> To: "Jenny Ryan" <tunabananas@gmail.com>
> Cc:
> 
> When people share their internet we use a tunnel to hide their IP (and
> to connect them to the mesh through the Internet). This tunnel takes a
> few bytes of overhead. All physical connections, whether they're
> ethernet, wifi or even an abstraction like a tunnel, have an MTU
> (Maximum Transfer Unit) which is the size of the largest packet that
> can be sent over the connection. Normally the MTU is 1500 but since
> the tunnel needs a few bytes for overhead the MTU of the tunnel will
> be less than 1500.
> 
> When people connect to the wifi network called peoplesopen.net they
> will connect with an MTU of 1500 since this is the default for wifi.
> We need a way to tell them that the MTU is actually less than 1500. In
> an IP network (which is at layer 3) there is a built-in system for
> dealing with this. If any router receives a packet larger than what it
> can pass on through the next connection (in this case through the
> tunnel) it can report back to the client using the ICMP protocol (a
> companion protocol to IP, and the protocol used for ping) that the
> packet was too big and the client can then adjust its MTU accordingly.
> 
> For batman-adv, because it is a layer 2 protocol, we don't have this
> system available. We tried different tactics such as using DHCP to
> tell the clients the MTU they should use, but it turns out that many
> operating systems completely ignore this. We tried something called
> TCP MSS clamping, which is a bit of a dirty hack, but that only works
> for TCP, which is a problem since UDP is widely used for e.g. VOIP,
> video streaming, gaming, torrenting, etc.
> 
> Even combining the different tricks we still had a problem where some
> operating systems would get in trouble if they tried to send large UDP
> packets. We had a moment where we realized that the only types of
> common communication that wouldn't work on this mesh would be
> torrenting and video streaming from windows computers, and joked about
> that being a feature instead of a bug :) but in the end we switched to
> Babel.
> 
> There was another reason: In batman-adv the MAC address is the
> identifier used for each device. It is possible to configure many
> devices to randomize their MAC address but it needs the user to do
> something, so most people will never know to do it. Having the MAC
> address as the identifier makes it pretty easy for anyone to track
> anyone else as they move about the city, as long as they know the MAC
> address of e.g. their phone, which it is easy to discover if you are
> ever in the same room with them, just by listening to network traffic.
> We had some ideas for how this could be fixed, but the potential
> solutions we came up with were never satisfactory.
> 
> For mesh, each time a user connects to a new node they get a new IP
> address. In the future we may implement roaming support which will let
> people keep their IP as they move around the city, but it will still
> switch after e.g. 10 minutes, so tracking people becomes much harder.
> 
> That's a lot of text, but eh it's a complicated issue. It sounds like
> you're having many late night conversations. Hope it is enjoyable!
> 
> --
> marc/juul
> 
> 
> 
> 
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> 
> 



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