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(usagi-users 03904) Re: Binding Update Failure

Hi Ryan,

On 2007/07/20, at 2:15, Ryan Measel wrote:
I tried a new setup today with the routers separated down the fall
from each other so that the wireless networks overlap just a bit.
Both wireless networks are on a separate ESSID (homenet and visitnet).


I had both of the networks on the same channel though.  Is it
necessary or preferred to have the routers on different channels?

This is bad. If both APs are on the same channel, you'll have noise and interferences between both APs. Every AP whose coverage overlaps with another must use nonoverlapping independent channels (usually channels 1, 6 and 11 are used).

does the MN receive router advertisements from the AR if it is
listening for its own router on a different channel?

The MN can't listen to 2 AP at the same time with a single WiFi card. The MN actually listens to the AP it is attached too, and for example when the link quality is too low (or for your test you can force the MN to associate with another AP by doing "ifconfig ath0 essid visitnet" for example), it tries to associates with a different AP on a different channel. Then the MN receives the new RA, and the layer 3 handover procedure is launched. That's why in Mobile IPv6, L3 handovers can take several seconds. Some solutions such as using multiple interfaces (for example MCoA) can reduce greatly the L3 handover time. But first, let's have a simple MIPv6 testbed running :-)

In addition, the
routers are set to master (ap) mode and the HA and MN are in managed
mode.   Would it be better to put everything in ad-hoc?

No no, current configuration (master and managed mode) is the only mode you can use for a MIPv6 Testbed. Ad-hoc mode is another story.

When I gave this setup a try, it partially succeeded.  The MN did
successfully bind into the foreign network a couple times, but failed
considerably more.  The issue was that router advertisements from both
the HA and AR were being received in both wireless networks.  The MN
is receiving both of these from either the HA or the AR (depending on
which network it resides in at the time), and the MN is out of range
of which ever network it is not in.  Hence, the router advertisements
are being forwarded between the networks.  IPv6 forwarding
(/proc/sys/net/ipv6/conf/forwarding) is set to 1, but Accept RAs
(/proc/sys/net/ipv6/conf/accept_ra) is set to 0 on the HR, HA, and AR.
This is very confusing because I did not believe routers were suppose
to forward router advertisements.  I suppose it is possible just
because I am using normal nodes with a bridge as access points, as
opposed to true routers.  Is there another way to prevent router
advertisements from being forwarded?

Hmm I do not completely understand your network topology, and RA are not supposed to be routed by routers. Maybe you could send some ascii drawing with some information such as where are the routers, who is sending RAs, where are the APs.

FYI, every different IP link must be separated from the other one with an IP Router. This router sends different RA on each link. One AP can be placed on each link playing the role of a bridge.


On 7/19/07, Romain KUNTZ <kuntz@xxxxxxxxxxxxxxxxxxxxx> wrote:
Hi Ryan,

On 2007/07/19, at 5:53, Ryan Measel wrote:
> I am still having issues with the mobile node not being able to bind
> to the home agent. It knows that it moves into a foreign network, but
> it then throws an error that "blackhole is already set." And, no

Do not pay attention to this message, this is juste a debug message
that ii IMHO not the cause of your problem.

> binding update will be sent. I have posted the debug from the mobile
> node and the config file for the mobile node below.

Ok, see my comment inline below.

> Also, how does everyone else setup their testbed, i.e., what type of
> hardware do use for routers and the home agent?

Personnally, I use some usual desktop PCs for the HA, MR, Access

> Mobile Node Debug Output
> =====================
> Wed Jul 18 23:32:38 mn_move: 1578
> Wed Jul 18 23:32:38 mn_move: in foreign net
> Wed Jul 18 23:32:39 mn_move: 1578
> Wed Jul 18 23:32:39 mn_move: in home net
> Wed Jul 18 23:32:44 mn_move: 1578
> Wed Jul 18 23:32:44 mn_move: in foreign net
> Wed Jul 18 23:32:45 mn_move: 1578
> Wed Jul 18 23:32:45 mn_move: in home net

Looks like your MN moves to the Home Network right after (1 sec.)
finding a foreign network. I think it does not send any BU because it
does not have the time to send one :-)

How do you performs handovers? Are your APs configuration OK
(different channel and ESSID, etc.)?


-- Romain KUNTZ kuntz@xxxxxxxxxxxxxxxxxx Louis Pasteur University - Networks and Protocols Team