Subject: Re: [Mipshop] gen-art IETF LC Review: draft-ietf-mipshop-4140bis-02.txt

From: "Joel M. Halpern" <[email-masked]>
Date: Sat, 19 Apr 2008 15:09:10 -0400

I have been selected as the General Area Review Team (Gen-ART)
reviewer for this draft (for background on Gen-ART, please see
http://www.alvestrand.no/ietf/gen/art/gen-art-FAQ.html ).

Please resolve these comments along with any other Last Call comments
you may receive.

Document: Hierarchical Mobile IPv6 Mobility Management
Reviewer: Joel M. Halpern
Review Date: 19-April-2008
IETF LC End Date: 22-April-2008
IESG Telechat date: 24-April-2008

Summary: Almost ready for publication as a proposed standard.

Comments:
Significant:
	As I read this protocol, if a Home Agent is beign used, then packets 
arriving at the MAP from the Home Agent will be tunneled, with the 
original packet inside a header from the HA to the MAP.  The MAP will 
then wrap that up in a tunnel and ship it to the LCoA.  This means that 
HMIP nodes that use Home Agents need to be preapred to receive 
doubly-encapsulated packets.  But there is no description of this in the 
Mobile Node Operation section 6.1.
	This also seems to imply that for communications where a Home Agent is 
being used, and bidirectional tunneling is being used with the Home 
Agent, then the Mobile Node needs to generate doubly-encapsulated packets.
	The section on detecting MAP failures could use improvement.  I realize 
that this is the same text as was in RFC 4140.  However, it seems to 
allow fairly common undetected failures.  It seems to me that stronger 
warning text about the weaknesses of manual intervention, and the 
possibility of undetected failures even with some keep-alive protocols 
ought to be mentioned.

Minor:
	The changes section indicates that Dynamic MAP discovery was removed. 
However, section 5 indicates that the distance "SHOULD be set to 1 if 
Dynamic MAP discovery is used."
	The fourth paragraph of section 6.1 indicates that a Mobile Node must 
send a binding update to is Home Agent.  If it is using a Home Agent, 
this is correct.  However, this spec now indicates that a Home Agent is 
not mandatory.  So this paragraph should say that the Binding Update 
must be sent if the Home Agent is being used.
	Given that Home Agents are option, the second paragraph of 6.1.1 should 
be clarified.  Either communicating directly with a CN is only permitted 
when one has a Home Agent, or the RCoA is permitted in the Home Address 
option of the Binding Update.
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---

From: Hesham Soliman <[email-masked]>
Date: Mon, 21 Apr 2008 19:28:23 +1000

Thank you for your comments.

> 	As I read this protocol, if a Home Agent is beign used, then  
> packets arriving at the MAP from the Home Agent will be tunneled,  
> with the original packet inside a header from the HA to the MAP.   
> The MAP will then wrap that up in a tunnel and ship it to the LCoA.   
> This means that HMIP nodes that use Home Agents need to be preapred  
> to receive doubly-encapsulated packets.  But there is no description  
> of this in the Mobile Node Operation section 6.1.
> 	This also seems to imply that for communications where a Home Agent  
> is being used, and bidirectional tunneling is being used with the  
> Home Agent, then the Mobile Node needs to generate doubly- 
> encapsulated packets.

=> Ok, I can add text to emphasise this point.

>
> 	The section on detecting MAP failures could use improvement.  I  
> realize that this is the same text as was in RFC 4140.  However, it  
> seems to allow fairly common undetected failures.  It seems to me  
> that stronger warning text about the weaknesses of manual intervention

=> Sure.

> , and the possibility of undetected failures even with some keep- 
> alive protocols ought to be mentioned.

=> What type of failures do you have in mind? a reboot that happens  
between keepalives for example?

>
>
> Minor:
> 	The changes section indicates that Dynamic MAP discovery was  
> removed. However, section 5 indicates that the distance "SHOULD be  
> set to 1 if Dynamic MAP discovery is used."

=> Ok.

>
> 	The fourth paragraph of section 6.1 indicates that a Mobile Node  
> must send a binding update to is Home Agent.  If it is using a Home  
> Agent, this is correct.  However, this spec now indicates that a  
> Home Agent is not mandatory.  So this paragraph should say that the  
> Binding Update must be sent if the Home Agent is being used.

=> ok.

>
> 	Given that Home Agents are option, the second paragraph of 6.1.1  
> should be clarified.  Either communicating directly with a CN is  
> only permitted when one has a Home Agent, or the RCoA is permitted  
> in the Home Address option of the Binding Update.

=> ok.

Hesham

---

From: "Joel M. Halpern" <[email-masked]>
Date: Mon, 21 Apr 2008 07:11:15 -0400

Thanks for the prompt reply.   One comment in line, confirming your reading.
Joel

> Thank you for your comments.
...
>> seems to allow fairly common undetected failures.  It seems to me that 
>> stronger warning text about the weaknesses of manual intervention
> 
> => Sure.
> 
>> , and the possibility of undetected failures even with some keep-alive 
>> protocols ought to be mentioned.
> 
Yep, that's the case I was thinking of.  Because we are not esepecifying 
the protocol, it seems to me that these sorts of concerns should be 
mentioned, to indicate that the protocol needs to deal with them.
...
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