Re: Last Call: IP Mobility Support to Proposed Standard

[Dave Johnson <[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