Comments on REQ5 (Compatibility) of draft-ietf-dmm-requirements-02

Hi All,

I have a comment on REQ5:  Compatibility of 
draft-ietf-dmm-requirements-02. What is not clear to me is that the 
meaning of the terms "compatibility\compatible\interoperate\co-exist" is 
not specific. Here is my clearification as following based on the comment 
I provided in the last DMM session in Atlanta.

Consider the scenario which is illustrated in figure A & B: 
Assuming operator A has already deployed PMIP protocol in city A (blue 
area in both figures), and wants to deploy dmm enabled euqipment in a 
certain area of city A in incremental manner (green area in both figures). 
Operator A needs the dmm protocol enabled area to be 
compatible\interopertable to exsiting PMIP protocol enabled area.  Here, 
operator A may have different requirements in terms of 
compatible\interopertable which are illustrated in figure A and B 
respectively.

Figure A, consider as roaming scenario. Any mobile node, as long as it is 
a subscriber of operator A, can be attached to operator A's network in 
both blue and green areas. The mobile node can not see any difference. 
E.g. assuming mobile node is now in green area, powered on, and initial 
attachment is performed (be asigned with an IP@). Then the mobile node can 
access the service provided by operator A (internet access and etc.).  In 
"roaming" scenario, when mobile node leaves green area and enters into 
blue area, the mobile node may need to perform initial attachment 
percedure again (be asigned with another IP@) for the purpose of accessing 
operator A's service. In this case, session continuity may not guaranteed 
when mobile node moves between the green and blue areas (i.e. IP@ may 
change when mobile node moves accross the border of the green and blue 
area).

Figure B, consider as handover scenario which requires more than the 
roaming scenario. E.g. assuming mobile node is initialized in blue area 
(be asigned with an IP@) and enjoys session continuity support when it 
moves within the blue area. When the mobile node enters the green area, in 
this handover scenario, the session continuity for sessions which have 
already setup shall be maintained (i.e. keep IP@ unchanged). The same 
requirement may also be applied to the scenario that when the mobile node 
is initialized in green area and moves to blue area. 

What I suggest is that we should make the terms 
"compatibility\compatible\interoperate\co-exist" more specific. I suppose 
adding some usage cases or usage scenarios may help to understand REQ5 
better.





Any comments are welcome.

BR
LUOWEN

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