Subject: RE: [nemo] RE: splitting moving networks (was: DND test)

From: "Soliman Hesham" <[email-masked]>
Date: Fri, 26 Mar 2004 05:07:11 -0500

> Soliman Hesham wrote:
 > >> So, what do you think, am I missing something?  Is anything from 
 > >> the NEMO Base Support that forbids this kind of split moving 
 > >> networks configuration to work properly?
 > > 
 > > => There is only one scenario where this configuration 
 > doesn't work, 
 > > if MR1 and MR2 are assigned the same MNP. This is what I've been 
 > > trying to clarify in the draft.
 > 
 > First, why would one assign the same MNP to MR1 and MR2?  For failure
 > avoidance of HA?  In that case better use two MNP's.

=> Pascal put the case for this scenario, have another
look at the thread from the beginning (about a week
ago). I'm not sure it's needed.

 > 
 > Second, even if one assigns only one MNP to both MR1 and MR2 in the
 > figure in the preceding email, then one would still assign different
 > Home Addresses on MR1 and MR2 respectively; and I think at that point
 > everything still works fine from the NEMO perspective: it's just that
 > there are two BC entries and two routing table entries.

=> No no, the network is split you don't know where
to forward LFN1's traffic, to MR1 or MR2?

Hesham

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From: Alexandru Petrescu <[email-masked]>
Date: Fri, 26 Mar 2004 11:24:07 +0100

Soliman Hesham wrote:

>> Soliman Hesham wrote:
>>>> So, what do you think, am I missing something?  Is anything 
>>>> from the NEMO Base Support that forbids this kind of split 
>>>> moving networks configuration to work properly?
>>> 
>> First, why would one assign the same MNP to MR1 and MR2?  For 
>> failure avoidance of HA?  In that case better use two MNP's.
> 
> => Pascal put the case for this scenario, have another look at the 
> thread from the beginning (about a week ago). I'm not sure it's 
> needed.
> 
>> 
>>  figure in the preceding email, then one would still assign 
>> different Home Addresses on MR1 and MR2 respectively; and I think 
>> at that point everything still works fine from the NEMO 
>> perspective: it's just that there are two BC entries and two 
>> routing table entries.
> 
> => No no, the network is split you don't know where to forward LFN1's
>  traffic, to MR1 or MR2?

We don't seem to, or I don't seem to, understand.  When the network
is split, LFN1 can only be at one place at one time (it can not be both
behind MR1 and behind MR2 simultaneously, the network is split, this is
no quantum mechanics here). So LFN1 is only behind MR1. If MR1's Home
Address comes before MR2's Home Address (in HA's rt table) then LFN1
gets the packet, otherwise it doesn't. And if it doesn't then there's a
configuration problem. And then re-configure by re-assigning different
MNP's to MR1 and MR2.

Again, this problem happens whenever a router has two rt entries towards
the same prefix but different nxt hop gw (and no dynamic rt protocol).
This problem and its solution is not NEMO specific I think.

Alex

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From: Alexandru Petrescu <[email-masked]>
Date: Fri, 26 Mar 2004 11:24:07 +0100

Alex

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From: Ryuji Wakikawa <[email-masked]>
Date: Sat, 27 Mar 2004 04:23:26 +0900

At Fri, 26 Mar 2004 05:07:11 -0500,
> ago). I'm not sure it's needed.

It might be useful for vehicle's moving network. 

Even if we prohibit the single prefix assignment to multiple MRs as
you said, we still need to confirm whether each MNP is surely assigned
to single MR or not.  But how?  
Do you think we can just treat this as configuration errors and do
nothing for this?

I think it is much easier to verify whether a mobile network is not
split or not. HA can ask to one of MR whether the other is onlink
or not (ex. check ND cache). If not, HA can reject BUs from both MRs.
Of course, there isn't such operation in the basic nemo though.

I do not try to propose solutions here, but I just want to say..  

If NEMO can detect the split mobile network and prohibit the
split mobile network, there is no problem for the same MNP
configuration.

Let's try not simply remove the case where same MNP is assigned to
multiple MRs and wait more inputs from multihoming work of NEMO WG.

ryuji

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From: Ryuji Wakikawa <[email-masked]>
Date: Sat, 27 Mar 2004 04:23:26 +0900

ryuji

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From: Alexandru Petrescu <[email-masked]>
Date: Fri, 26 Mar 2004 21:07:08 +0100

Ryuji Wakikawa wrote:
>>>> => There is only one scenario where this configuration doesn't 
>>>> work, if MR1 and MR2 are assigned the same MNP. This is what 
>>>> I've been trying to clarify in the draft.
>>> 

Ok.

> you said, we still need to confirm whether each MNP is surely 
> assigned to single MR or not.  But how? Do you think we can just 
> treat this as configuration errors and do nothing for this?

I think I do not propose to forbid single MNP per moving link when there
are two MR's; I think that if there is only one MNP per moving link and
that there are two MR's and each has a different Home Address and each
maintains a different tunnel to a different HA, then a routing protocol
might help to avoid loosing Internet access to any LFN on that moving
link when one of the MR's looses its egress wireless connection;

I think that when I'm writing that NEMO Base Support supports a moving
link with one MNP on it then I'm replied "yes, but what about two
MNP's"; then if I'm writing that NEMO Base Support supports a moving
link with two MNP's on it then I'm replied "yes, but what about one
MNP" :-)

> split or not. HA can ask to one of MR whether the other is onlink or 
> not (ex. check ND cache). If not, HA can reject BUs from both MRs. Of
> course, there isn't such operation in the basic nemo though.
> 
> If NEMO can detect the split mobile network and prohibit the split 
> mobile network, there is no problem for the same MNP configuration.
> 
> multiple MRs

Yes, I agree with this, I don't propose to always have two MNP's per
link; there should be one MNP per link when there are two TLMR's and
they together with their HA's should use an IGP to detect whenever the
egress wireless interface is lost.

And, if the two TLMR's can have an IGP to detect best paths when one HA
becomes unavailable, why shouldn't that IGP solve also the splitting of
the moving link itself? This could work: just put a Fixed Router at the
point where the split is susceptible to occur and let it find the right
paths after the split.

> and wait more inputs from multihoming work of NEMO WG.

Yes, I do not mean to interfere with the NEMO WG multi-homing work,
sorry, I think it will help clarifying multi-homing in the NEMO context.

Alex

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From: Alexandru Petrescu <[email-masked]>
Date: Fri, 26 Mar 2004 21:07:08 +0100

Ok.

Alex