Subject: [Mobike] issue 19 -- same addresses for both directions?

From: Jari Arkko <[email-masked]>
Date: Fri, 13 May 2005 12:20:46 +0300

It looks to me that the decision on issue 20 (who decides)
is the main determining factor issue 19 as well. If issue
20 resolution is that the initiator decides, then it more
or less follows that we have same addresses in both
directions. We can imagine different addresses even in
this case, but it does not appear to be very useful or
necessary.

On the other hand, if we decide in 20 that the decisions
are independent, then it may in fact be very hard to
ensure that the two directions use the same addresses.
As a result, allowing different addresses would make
more sense in this scenario.

My conclusion is that we should focus on trying to
solve issue 20 first.

--Jari

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From: Jari Arkko <[email-masked]>
Date: Sun, 29 May 2005 17:29:01 +0300

I wrote earlier tha the decision on issue 20 (who decides)
also has a big impact on issue 19. If we had decided in 20
that the decisions  are independent, then it might in fact
have been very hard to  ensure that the two directions
use the same addresses. As a result, allowing different
addresses would make  more sense in this scenario.

But we ended up with "initiator decides". Therefore the
deciding entity knows enough about the situation to be
able to use the same address pairs in both directions.

Of course, this does not necessarily have to be done.
We could develop a protocol that provides independent
addresses, yet would be controlled by the initiator.
(Probably with some cost in terms of complexity.
And I'm not quite sure how to deal with NATs and
keepalives in that kind of a scenario.)

How do you folks feel about this? Please post your
comments by Friday, June 3rd.

--Jari

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From: Geoffrey Huang <[email-masked]>
Date: Mon, 30 May 2005 09:53:50 -0700

Hi Jari,

Comments inline.

> able to use the same address pairs in both directions.

This makes sense to me - it's the logical progression from what was
decided for Issue 20.

> keepalives in that kind of a scenario.)

I can't imagine why this would be useful.  In which scenarios wouldn't
we want the initiator to decide which address pairs to use in both
directions?

-g

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From: "Mohan Parthasarathy" <[email-masked]>
Date: Tue, 31 May 2005 18:28:40 -0700

> keepalives in that kind of a scenario.)
Hmm.. we chose the "initiator decides" option because it works
well with NAT. So, i am not sure i understand the issue here.
Here, the initiator finds two sets of addresses (one for
upstream and one for downstream traffic) and updates the
peer providing information about which address pair to be used
for downlink and which address to be used for up link.
I would assume that it is the initiator's responsibility for sending
keep alives. So, what is the issue here with NATs ? 

If the initiator is multi-homed and connected simultaneously to more
than one access (e.g. UMTS and WLAN) at the same time, there
might be some usefulness in having different paths for upstream and
downstream traffic though i don't know really what it is :-)  

-mohan