17 Sep
2009
17 Sep
'09
2:01 a.m.
In the ROBIN address allocation described here
http://robin-mesh.wik.is/Documentation/Router_Configuring/Advanced_Configur…
I'm curious how collisions are avoided.
If you generate IP 5.dd:ee:ff from aa:bb:cc:dd:ee:ff won't you get a collision if you
other devices with MACs ending in dd:ee:ff like aa:aa:cc:dd:ee:ff, aa:aa:aa:dd:ee:ff, and
so on.
17 Sep
17 Sep
6:15 p.m.
2009/9/16 Lick A Prize <lick.prize(a)gmail.com>
In the ROBIN address allocation described here
http://robin-mesh.wik.is/Documentation/Router_Configuring/Advanced_Configur…
curious how collisions are avoided.
If you generate IP 5.dd:ee:ff from aa:bb:cc:dd:ee:ff won't you get a
collision if you other devices with MACs ending in dd:ee:ff like
aa:aa:cc:dd:ee:ff, aa:aa:aa:dd:ee:ff, and so on.
What is the occurrence probability of "r" MAC-Adress twon agree on their
last two bytes?
This is similar to the birthday paradox: At a meeting of r> 2 people which
is the number of people needed for the probability that two men have same
birthday sould be 99%? The solution is in many books and that can view at:
http://en.wikipedia.org/wiki/Birthday_problem
Then, At a meeting of 60 people there is the 99% probability of the least
two men have a birthday the same day. So,, Similarly to the case of
MAC-Adress is:
P(r)=1-65536!/(65536^r * (65536-r)!)
where *! is factorial operator, and "r" is the Mac-Adress.
Well if the calculations are not mistake, we obtain r = 13,107 MAC-Adress
minimun in the same site then 99% probability two matches in his last two
bytes.
Now a new MAC entering, which is the probability that given "n"
MAC-Adress,,, all with two last byte differents this new MAC matches with
any MAC-Adress in its last two bytes? Well this is:
P(n)=1-(65535/65536)^n then when n=13107 is P(13107)=0.18 or 18%. That is
MAC-paradox...
_______________________________________________
B.A.T.M.A.N mailing list
B.A.T.M.A.N(a)lists.open-mesh.net
https://lists.open-mesh.net/mm/listinfo/b.a.t.m.a.n
7:21 p.m.
Gustavo Lindberg wrote:
Then, At a meeting of 60 people there is the 99%
probability of the least
two men have a birthday the same day. So,, Similarly to the case of
MAC-Adress is:
P(r)=1-65536!/(65536^r * (65536-r)!)
Robin uses 3 bytes of the MAC address to choose the IP address of the
mesh interface, not only 2 bytes = 65536 possibilities. This leads to
2^24 = 16777216 different addresses.
Expressed in PARI/GP syntax, you get the following formula:
p(n) = 1 - (factorial(2^24) / ((2^24)^n * factorial(2^24 - n)))
For a network of n=1000 nodes, PARI/GP calculates a probability of about
3 % for an address collision, which should pose no problem.
This is only valid if the NIC vendors randomly choose the MAC addresses
of their cards; chances are that they simply increment the address for
each NIC manufactured. This would increase the possibility of collisions.
However, as Marek already wrote, the focus of the batman development
moves to layer 2 where IP addresses are not used. On top of batman-adv,
you can use any IP address distribution scheme you like. For example,
you could simply run a DHCP server.
Regards,
Daniel
8:14 p.m.
2009/9/17 Daniel Seither <post(a)tiwoc.de>
Gustavo Lindberg wrote:
All IP addresses are derived by device's MAC address, if MAC is
aa:bb:cc:dd:ee:ff then ath0 IP (mesh iface) will be 5.dd:ee:ff while ath1 IP
and ath2 IP will be 101.ee:ff:1 and 102.ee:ff:1 (obviously in decimal
format).
Then, At a meeting of 60 people there is the 99%
probability of the
least
two men have a birthday the same day. So,,
Similarly to the case of
MAC-Adress is:
P(r)=1-65536!/(65536^r * (65536-r)!)
Robin uses 3 bytes of the MAC address to choose the IP address of the
mesh interface, not only 2 bytes = 65536 possibilities. This leads to
2^24 = 16777216 different addresses.
8:36 p.m.
Gustavo Lindberg schrieb:
2009/9/17 Daniel Seither <post(a)tiwoc.de>
I read this before, but now I realize that colliding IP addresses of the
ath1/2 interfaces are a problem. This seriously limits the number of
nodes in the network for reasonably low collision probabilities. With
200 nodes, you already have a probability greater than 25%. Enter IPv6...
Regards,
Daniel
Gustavo Lindberg wrote:
All IP addresses are derived by device's MAC address, if MAC is
aa:bb:cc:dd:ee:ff then ath0 IP (mesh iface) will be 5.dd:ee:ff while ath1 IP
and ath2 IP will be 101.ee:ff:1 and 102.ee:ff:1 (obviously in decimal
format). Then, At a meeting of 60 people there is the 99%
probability of the
least
two men have a birthday the same day. So,,
Similarly to the case of
MAC-Adress is:
P(r)=1-65536!/(65536^r * (65536-r)!)
Robin uses 3 bytes of the MAC address to
choose the IP address of the
mesh interface, not only 2 bytes = 65536 possibilities. This leads to
2^24 = 16777216 different addresses.
18 Sep
18 Sep
4:38 a.m.
OK so IPs from MAC addresses is pretty good but not a perfect solution.
This comment is interesting...
However, as Marek already wrote, the focus of the
batman development
moves to layer 2 where IP addresses are not used. On top of batman-adv,
you can use any IP address distribution scheme you like. For example,
you could simply run a DHCP server.
Regards,
Daniel
Batman-adv does indeed seem like the way forward. So, on top of batman-adv,
what solutions are there for IP address distribution? What might you try in
a situation where there is no obvious central coordinator to put a DHCP
server on?
8:19 a.m.
Batman-adv does indeed seem like the way forward. So,
on top of batman-adv,
what solutions are there for IP address distribution? What might you try in
a situation where there is no obvious central coordinator to put a DHCP
server on?
Just do a quick search for "ip
autoconfiguration"/"address
autoconfiguration"[1,2] and you will find different solutions like
zeroconf[3]/APIPA[4]. These are of course only link-local/point-to-point
solutions.
Best regards,
Sven
[1] http://tools.ietf.org/html/rfc3927
[2] http://tools.ietf.org/html/rfc4862
[3] http://www.zeroconf.org/
[4] http://msdn.microsoft.com/en-us/library/aa505918.aspx
8:42 a.m.
And for multi-hop networks, of the kind that BATMAN, OLSR, etc. are used
for?
--------------------------------------------------
From: "Sven Eckelmann" <sven.eckelmann(a)gmx.de>
Sent: Friday, September 18, 2009 6:19 PM
To: "The list for a Better Approach To Mobile Ad-hoc Networking"
<b.a.t.m.a.n(a)lists.open-mesh.net>
Subject: Re: [B.A.T.M.A.N.] IP from MAC
_______________________________________________
B.A.T.M.A.N mailing list
B.A.T.M.A.N(a)lists.open-mesh.net
https://lists.open-mesh.net/mm/listinfo/b.a.t.m.a.n
6:04 p.m.
Hey,
right, on batman-adv you can use a central DHCP server
or use decentralized link-local IP autoconfiguration tools as Sven suggested.
On Fri, Sep 18, 2009 at 06:42:18PM +1000, Lick A Prize wrote:
And for multi-hop networks, of the kind that BATMAN,
OLSR, etc. are used
for?
--------------------------------------------------
From: "Sven Eckelmann" <sven.eckelmann(a)gmx.de>
Sent: Friday, September 18, 2009 6:19 PM
To: "The list for a Better Approach To Mobile Ad-hoc Networking"
<b.a.t.m.a.n(a)lists.open-mesh.net>
Subject: Re: [B.A.T.M.A.N.] IP from MAC
_______________________________________________
B.A.T.M.A.N mailing list
B.A.T.M.A.N(a)lists.open-mesh.net
https://lists.open-mesh.net/mm/listinfo/b.a.t.m.a.n
_______________________________________________
B.A.T.M.A.N mailing list
B.A.T.M.A.N(a)lists.open-mesh.net
https://lists.open-mesh.net/mm/listinfo/b.a.t.m.a.n
7:15 p.m.
2009/9/18 Simon Wunderlich <simon.wunderlich(a)s2003.tu-chemnitz.de>
Hey,
right, on batman-adv you can use a central DHCP server
or use decentralized link-local IP autoconfiguration tools as Sven
suggested.
In this scenario, as would resolve the situation of having several internet
gw? L3 Batman announces gw nodes and the client chooses the most
appropriate. But in L2 ?
On Fri, Sep 18, 2009 at 06:42:18PM +1000, Lick A Prize wrote:
And for multi-hop networks, of the kind that
BATMAN, OLSR, etc. are used
for?
--------------------------------------------------
From: "Sven Eckelmann" <sven.eckelmann(a)gmx.de>
Sent: Friday, September 18, 2009 6:19 PM
To: "The list for a Better Approach To Mobile Ad-hoc Networking"
<b.a.t.m.a.n(a)lists.open-mesh.net>
Subject: Re: [B.A.T.M.A.N.] IP from MAC
_______________________________________________
B.A.T.M.A.N mailing list
B.A.T.M.A.N(a)lists.open-mesh.net
https://lists.open-mesh.net/mm/listinfo/b.a.t.m.a.n
_______________________________________________
B.A.T.M.A.N mailing list
B.A.T.M.A.N(a)lists.open-mesh.net
https://lists.open-mesh.net/mm/listinfo/b.a.t.m.a.n
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (GNU/Linux)
iEYEARECAAYFAkqzy8IACgkQrzg/fFk7axZddACguK3p2nbQfMgtfG6KnQ9i+V9r
L5cAoMjtLEl9uLFoO+gC1Dp2vY37sjJw
=Xo4P
-----END PGP SIGNATURE-----
_______________________________________________
B.A.T.M.A.N mailing list
B.A.T.M.A.N(a)lists.open-mesh.net
https://lists.open-mesh.net/mm/listinfo/b.a.t.m.a.n
21 Sep
21 Sep
4:31 a.m.
Will link local autoconfiguration/APIPA work in multi-hop ad hoc networks?
Say you have 5 nodes connected, in a line, in an ad hoc network as
follows...
A <----> B <-----> C <-----> D <------> E
Will autoconfigure ensure that A and E have different addresses? Is there a
chance that they will both end up with, say for example, 169.254.0.123?
--------------------------------------------------
From: "Simon Wunderlich" <simon.wunderlich(a)s2003.tu-chemnitz.de>
Sent: Saturday, September 19, 2009 4:04 AM
To: "The list for a Better Approach To Mobile Ad-hoc Networking"
<b.a.t.m.a.n(a)lists.open-mesh.net>
Subject: Re: [B.A.T.M.A.N.] IP from MAC
_______________________________________________
B.A.T.M.A.N mailing list
B.A.T.M.A.N(a)lists.open-mesh.net
https://lists.open-mesh.net/mm/listinfo/b.a.t.m.a.n
4931
days inactive
4935
days old
b.a.t.m.a.n@lists.open-mesh.org
11 comments
5 participants
participants (5)
-
Daniel Seither -
Gustavo Lindberg -
Lick A Prize -
Simon Wunderlich -
Sven Eckelmann