Re: Technical objections -- Mobility

[Dave Johnson <[e-mail]>]

Bill,

In your latest message, you say:

>> > Use of the "co-located care-of address" is a poor design option, and
>> > should be removed (again).
>>
>> I don't think so.  I think it's a great design option.
>>
>I here omit the detailed analysis that was provided in my previous
>message, and note that no counter analysis was provided.  Instead, we
>have "proof by assertion".


You seem to ignore my counter analysis, presented to you in my response
to you on March 1, reproduced below:


>To: William Allen Simpson <[e-mail]>
>Cc: [e-mail]
>In-Reply-To: Your message of "Fri, 01 Mar 96 14:22:51 GMT"
>             <[e-mail]> 
>From: Dave Johnson <[e-mail]>
>Subject: Re: Last Call: IP Mobility Support to Proposed Standard 
>Date: Thu, 07 Mar 96 00:43:15 EST
>Message-ID: <[e-mail]>
>Sender: [e-mail]
>
>>I oppose the advancement of these protocols to Proposed Standard, on
>>both technical and process issues.
>>
>>This missive covers a few of the technical issues for
>>
>>>  1. IP Mobility Support
>>> 	<draft-ietf-mobileip-protocol-15.txt>
> ...
>>
>>                                ----
>>
>>Use of the "co-located care-of address" is a poor design option, and
>>should be removed (again).
>>
>>In this model, the tunnel is from the Home Agent to the Mobile Node:
>>
>>                     HA ====>R====>R====>FA====> MN
>>
>>Yet, the last hop to the Mobile Node likely has the least bandwidth, and
>>therefore the burden of the larger tunneled datagram is most likely to
>>be a problem.  It also inhibits other bandwidth improvements, such as VJ
>>TCP header compression.
>>
>>Instead, only the FA handled registrations should be used:
>>
>>                     HA ====>R====>R====>FA----> MN
>>
>>This would simplify the protocol implementation, remove the need for the
>>'R' bit negotiation, and remove one of the potential patent problems.
>
>Bill,
>
>Although some might wish that the entire world could be made to use
>only foreign agents, this is simply not the case.  For example, I
>am using Mobile IP to support transparent switching between Ethernet
>and CDPD.  When you get CDPD service from your cellular phone company,
>you get an IP address, much the way you get a phone number with 
>cellular phone service.  CDPD does not have any foreign agents.
>Instead, I can use my CDPD-assigned IP address as a co-located care-of
>address, and can tunnel packets directly to my mobile node on CDPD.
>The home address of my mobile node is its Ethernet (CMU-assigned) IP
>address, and its co-located care-of address is its CDPD-assigned IP
>address.  This cannot be supported without co-located care-of addresss,
>since there are no foreign agents and I can't make Bell Atlantic
>NYNEX Mobile deploy any.  Of course, I would like to have the
>encapsulation header removed before the transmission over the slow
>CDPD wireless link, but I simiply do not have that choice in this
>application.
>
>					Dave


In some cases, foreign agents simply are not (and will not be) present.
For example, by using a co-located care-of address, I can have my home
address be the Ethernet in my office, and can use CDPD while away from
home.  You may choose to again ignore this counter analysis (I don't
know why you replied to Charlie on this point and not to me), but I
expect it is obvious to anyone rationally thinking about the problem,
that the optional use of co-located care-of addresses adds more power
to the protocol.  In the example outlined in my earlier message to you
(above), this simply cannot be done without use of a co-located care-of
address.

For you to imply that no counter analysis has been provided to you is
inaccurate.  Perhaps Charlie didn't state any in his message, but my
counter analysis has been sent to you and to the IETF mailing list, and
you have ignored it, chosing instead to attack Charlie.

					Dave