Subject: RE: [Tsvwg] multiaddressing

From: "Henderson, Thomas R" <[email-masked]>
Date: Wed, 17 Nov 2004 18:16:36 -0800

> -----Original Message-----
> From: Wesley Eddy [mailto:[email-masked]] 
> Sent: Monday, November 15, 2004 1:41 PM
> To: [email-masked]
> Subject: [Tsvwg] multiaddressing
> 
> 
> Architectures that don't include such wedges are what we were 
> considering in draft-eddy-tlmarch-00 (presented last week).  
> The idea of rapidly fixing the transport's path estimation 
> variables is roughly visible in draft-swami-tcp-lmdr-04.  For 
> architectures that *do* include wedges, some similar form of 
> signaling and responding to path changes is still _required_. 
>  Signaling has to occur both between the wedge and transport 
> locally and remotely, so that both half-connections can be 
> fixed.  Responses to these signals will have to be 
> implemented per-transport protocol.
> 
> It's not entirely clear to me how we can combine the 
> strengths of a multiaddressing wedge layer with the 
> rapid-response of path property estimates that we can have 
> without the wedge in a transport layer mobility scheme.  Thoughts?

What is not clear?  Whether to use the LMDR techniques, or how
to invoke them?  It doesn't seem that invoking them should be
much of a problem-- wedge layers can keep track of when addresses
change and do an internal trigger notification.  In fact, the 
proposed LMDR option might not be needed in such a case, and it
can all be handled locally, independently by both sides of the
connection.

What is the status of LMDR?  Has it been proposed for any WG
activity?  

Tom

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---

From: Wesley Eddy <[email-masked]>
Date: Wed, 17 Nov 2004 21:52:54 -0500

On Wed, Nov 17, 2004 at 06:16:36PM -0800, Henderson, Thomas R wrote:
> to invoke them?

Well, let's start by looking at the claim that a wedge layer is handy
because you don't have to modify any transports.  The argument is that
at least all congestion-controlled transports should be modified, so
this advantage of the wedge approaches falls down at least a bit.  The
wedge approach is still handy for dealing with the book-keeping as
addresses come and go, but to me it's pretty clear that we can't leave
the transport entirely untouched.

If we use a wedge, we have to extend the interface to pass "mobility
event" bits up to the transport so that congestion control and other
path estimates can be properly dealt with.  The exact interface will
require some thought.  I do not know of any current work on this.

> It doesn't seem that invoking them should be

That sounds right to me.  The LMDR option arose because Mobile IP masks
mobility events totally.  If a wedge was to be kindly enough to
propagate that information up the stack, then a TCP option wouldn't be
needed, we'd just need the TCP path state-reseting behavior in response
to triggers from the wedge.
 
> What is the status of LMDR?  Has it been proposed for any WG

The current version of the draft has not been discussed in an IETF
context yet.  I believe that earlier versions have been in either TSVWG
or TCPM, although have not generated much interest.  Yogesh can probably
provide a better answer to this.  I think Nokia is exploring it in some
internal use, and I know that we've been advocating a similar TCP
response to mobility events in NASA's ACAST project
(http://acast.grc.nasa.gov), and as a transport modification to aid in
planetary exploration missions using mobile devices.

-Wes

---

From: Yogesh Prem Swami <[email-masked]>
Date: Thu, 18 Nov 2004 11:22:45 -0600

Hi Wes, Tom,

Please see inline:

> or TCPM, although have not generated much interest.  Yogesh can probably

The old LMDR draft (using just a bit) was presented in TSVWG long time 
back, but there wasn't enough discussion. (Note that the draft has two 
parts, detection and response, and the response part should be valid 
regardless of the detection scheme.)

Yogesh