Subject: [nemo] Issue 3

From: "Pascal Thubert (pthubert)" <[email-masked]>
Date: Wed, 16 Jul 2003 09:03:42 +0100

"The Home Agent SHOULD store the list of Mobile Network Prefixes 
  owned by a Mobile Router in the corresponding Binding Cache 
  entry.  However this is done only when the Mobile Router has
  included prefix information in the Binding Update.  This list 
  of prefixes should include only those for which the Home Agent 
  currently has routes pointing to the Mobile Router's current 
  Care-of address.  This information can later be used to delete 
  the routes when the Binding Cache entry for the Mobile Router 
  is deleted."

> is this okay?

If the info is to be used to delete the routes, then you need to know
which prefixes you actually created routes for, so maybe you need more
info associated to the prefixes, like pointers to the adjacencies that
were instantiated. This is deep into implementation, a bit to much to my
taste.

I would have preferred a text saying that "the MR MUST keep all
necessary information to clean up whichever routes it installed, for
instance by keeping the list of prefix in BCE, whether they come from
implicit or explicit source". Vijay, please do not tell people how to
implement things (even if your proposal seems perfectly proper).

Pascal

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From: Vijay Devarapalli <[email-masked]>
Date: Wed, 16 Jul 2003 11:49:00 -0700

"Pascal Thubert (pthubert)" wrote:
> which prefixes you actually created routes for, 

  This list
  Care-of address.

> implement things (even if your proposal seems perfectly proper).

:) I do agree that over specification is bad. but I thought 
it was necessary in this case. please suggest text.

Chan-Wah, what do you think? (you raised this issue)

Vijay

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From: Vijay Devarapalli <[email-masked]>
Date: Wed, 16 Jul 2003 11:49:00 -0700

This list

Vijay

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From: Chan-Wah Ng <[email-masked]>
Date: 17 Jul 2003 16:18:10 +0800

> > implement things (even if your proposal seems perfectly proper).

I don't think its "telling people how to implement things", just like in
MIPv6, suggesting the conceptual structure of BCE should contain the
home address, care-of-address, and the BU flags is not "telling people
how to implement things".

> Chan-Wah, what do you think? (you raised this issue)

I am okay with both text.  All I wanted to make sure is that when routes
are injected by the registration of a BU, the HA must have means of
removing / or updating those routes when a subsequent BU comes in.

/rgds
/cwng

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From: Chan-Wah Ng <[email-masked]>
Date: 17 Jul 2003 16:18:10 +0800

/rgds
/cwng

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From: Kent Leung <[email-masked]>
Date: Thu, 17 Jul 2003 03:28:48 -0700

>removing / or updating those routes when a subsequent BU comes in.

Then the goal is clear and consensual.

>   the routes when the Binding Cache entry for the Mobile Router

This text may be a bit too specific and incomplete.  One can incorrectly 
interpret
that route is only deleted when BCE is deleted.

>Pascal

This text doesn't cover the case when routes need to be re-injected into
the routing table.

My suggestion:

"The Home Agent MUST keep all necessary information to be able to add or
delete routes associated with the Mobile Router at the time.  For instance,
the list of Mobile Network Prefixes may be stored in the Binding Cache
entry."

Kent

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From: Kent Leung <[email-masked]>
Date: Thu, 17 Jul 2003 03:28:48 -0700

My suggestion:

Kent

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From: Chan-Wah Ng <[email-masked]>
Date: 17 Jul 2003 22:10:14 +0800

Hello Kent, Vijay, Pascal, and all,

> the list of Mobile Network Prefixes may be stored in the Binding Cache

Hmm, this drops the implicit and explicit source part, which I think is
important.  May I propose to further refine the text to

"The Home Agent MUST keep all necessary information to be able to add or
delete routes associated with the Mobile Router at the time, whether the
routes come from implicit or explicit source(s).  For instance, the list
of Mobile Network Prefixes may be stored in the Binding Cache entry."

/rgds
/cwng

---

From: Chan-Wah Ng <[email-masked]>
Date: 17 Jul 2003 22:10:14 +0800

/rgds
/cwng

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From: Vijay Devarapalli <[email-masked]>
Date: Thu, 17 Jul 2003 10:38:24 -0700

> the list of Mobile Network Prefixes may be stored in the Binding Cache

hmm.. this doesnt tell me if I should store only those prefixes
for which the MR has requested the HA to create routes, or all
the prefixes. it doesnt make sense to include all prefixes.
that is why there was more specific text in my proposal.

to store the list of all prefixes owned by the Mobile Router
we have the prefix table. Binding cache entries are removed 
when they expire. the Prefix Table stays on.

Vijay

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From: Vijay Devarapalli <[email-masked]>
Date: Thu, 17 Jul 2003 10:38:24 -0700

Vijay

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From: Kent Leung <[email-masked]>
Date: Thu, 17 Jul 2003 15:15:48 -0700

At 10:38 AM 7/17/2003 -0700, Vijay Devarapalli wrote:
>the prefixes.

Right, deliberately so.  That's implementation details, IMHO.  The key
point is that HA has to have "all necessary information" to do the
right thing for route addition/deletion.  Some coders may store prefixes
from MR in BCE and some coders may store all prefixes in BCE.
Why should the spec care?  As long as the objective is achieved.

>it doesnt make sense to include all prefixes.

See above.

>when they expire. the Prefix Table stays on.

You have a good pt here.  I was coming from the angle of not
over-specifying or too much details.  I can't come up with a good
reason for some cases where all prefixes would be useful, right now.

Since this is in the sentence that starts with "For instance", then
there's no objection from me.  :)  The objective is covered by HA MUST
keep relevant info to properly maintain the routing table.

Kent

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From: Kent Leung <[email-masked]>
Date: Thu, 17 Jul 2003 15:15:48 -0700

See above.

Kent

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From: Vijay Devarapalli <[email-masked]>
Date: Thu, 17 Jul 2003 15:41:39 -0700

> from MR in BCE and some coders may store all prefixes in BCE.

binding cache entries expire.

> Why should the spec care? 

it should, IMO.

> keep relevant info to properly maintain the routing table.

the problem with a sentence like

  The Home Agent MUST keep all necessary information to be able 
  to add or delete routes associated with the Mobile Router at 
  the time.

is that it is too vague. what information are we talking 
about? where do you keep the information? you have another 
data structure in mind?

Mobile IPv6 has a brief description on Binding Cache 
structure. we are just extending it. see section 6.1 of 
http://people.nokia.net/vijayd/nemo/draft-ietf-nemo-basic-support-pre01.txt.
this contains the latest text.

Vijay

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From: Vijay Devarapalli <[email-masked]>
Date: Thu, 17 Jul 2003 15:41:39 -0700

it should, IMO.

Vijay