[Commotion-dev] nailing down the default mesh network

[Paul Gardner-Stephen]

Hello,

Deterministic BSSID generation is a good thing, and we did briefly try to
push this general idea into the 802.11 working group in the IEEE.  It great
advantages in reducing the possibility for cell splits which are a real
nuisance with ad-hoc as currently "standardized".

Paul.


On Fri, May 3, 2013 at 12:12 PM, Hans-Christoph Steiner <
hans at guardianproject.info> wrote:

>
> Sean McIntyre and I developed an algorithm to generate the BSSID based on
> the
> SSID and channel:
>
>
> > Hey folks,
> >
> > Talked about this with Hans today. We came up with the following
> algorithm:
> >
> > BSSID = MD4(ESSID)[0:4] ++ channel 2-byte integer
> >
> > This is read in English as: "The six byte BSSID is the first four
> > bytes of the MD4 hash of ESSID concatenated with the lowest two bytes
> > of the channel."
> >
> > The rationale for this is that MD4 is uniformly distributed, and the
> > first four bytes of MD4 are presumably uniformly distributed. (Should
> > be distributed enough.) Then add on the bytes of the channel so that
> > same ESSIDs don't collide. MD4 was an arbitrary function choice, and
> > security is not an issue.
> >
> > I found a public domain implementation of MD4
> > <
> http://openwall.info/wiki/people/solar/software/public-domain-source-code/md4
> >
> > and made a simple get_bssid() function the same as the above algorithm
> > (attached).
> >
> > Signature for get_bssid:
> >
> > get_bssid(char *essid, unsigned int channel, unsigned char *bssid) //
> > (result goes in bssid)
> >
> > Not sure how to add this in, so hope one of you goes ahead and does
> > that, or let me know how I can be of further service.
>
> Also, see the attached source code for Sean's implementation of it.
>
> .hc
>
>
>
> On 05/02/2013 02:32 AM, Teco Boot wrote:
> > I prefer WiFi channels 1, 6 or 11 as a default.
> >
> > I prefer a true (pseudo-)random BSSID. Could be hash over SSID&channel.
> >
> > I'm afraid there is no ideal solution for addressing. Short term: some
> v4 space. More fundamental: auto-generated IPv6 ULA and with support for v4
> traffic. With IPv6, multi-homing with multi-path is much easier to
> implement (routing based on source address).
> >
> > Teco
> >
> > Op 1 mei 2013, om 22:17 heeft Hans-Christoph Steiner <
> hans at guardianproject.info> het volgende geschreven:
> >
> >>
> >> One idea that we discussed at the last dev sprint last Thursday/Friday
> is
> >> nailing down a default mesh profile that we can set everywhere.  The
> core idea
> >> is that people can use this as the easiest way to get started, and
> also, it
> >> can serve as the mesh config for impromptu meshing.
> >>
> >> Currently, we have been using this:
> >>
> >> SSID: commotionwireless.net
> >> BSSID: 02:CA:FF:EE:BA:BE
> >> Channel: 5
> >> IP range: 5.0.0.0/255.0.0.0
> >>
> >> There are two issues that we need to address in order to nail down this
> >> default profile: a valid IP range, and perhaps a unique BSSID.
> >>
> >> 5.0.0.0/255.0.0.0 is an officially allocated block of IPs that is
> actually
> >> deployed in some places.  We should use an IP block that is officially
> >> allocated for uses like Commotion intends.  We discussed this, and it
> seems
> >> like the best bet is to use one of the RFC1918 private network ranges
> (10/8,
> >> 172.16/12, and 192.168/16).  172.16.0.0-172.31.255.255 seems to be the
> least
> >> used of the three.  It privdes 1,048,576 unique IP addresses, so plenty.
> >>
> >> We might want to consider using 100.64.0.0/10, which is reserved for
> "carrier
> >> grade NAT", i.e. a large scale NATed network that is attached to the
> internet.
> >>
> https://en.wikipedia.org/wiki/Private_network#Dedicated_space_for_Carrier_Grade_NAT_deployments
> >>
> >> The rules for using it are in RFC 6598:
> >> https://tools.ietf.org/html/rfc6598
> >>
> >>
> >> As for the BSSID, I think we should probably use a unique BSSID to
> prevent
> >> collisions with other mesh networks.  02:ca:ff:ee:ba:be is used by a
> number of
> >> other meshes.  It really could be any valid adhoc BSSID like
> 02:02:02:02:02:02
> >>
> >> .hc
> >> _______________________________________________
> >> Commotion-dev mailing list
> >> Commotion-dev at lists.chambana.net
> >> https://lists.chambana.net/mailman/listinfo/commotion-dev
> >
>
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>
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