Re: [MEXT] Comments on draft-ietf-mext-binding-revocation-02

["Ahmad Muhanna" <[e-mail]>]

Hi Patrick,
Thanks for your review. Please see responses inline.

Regards,
Ahmad
 

> -----Original Message-----
> From: Stupar, Patrick [mailto:[e-mail]] 
> Sent: Wednesday, December 10, 2008 7:19 PM
> To: Muhanna, Ahmad (RICH1:2H10)
> Cc: [e-mail]
> Subject: Comments on draft-ietf-mext-binding-revocation-02
> 
> Hi Ahmad,
> 
> I have reviewed binding revocation draft and have the 
> following comments/questions. 
> 
> - In MIPv6, Binding Update and Binding Ack have two different 
> MH type values. Why isn't the same approach taken for BRI and 
> BRA and only one value is used? 

[Ahmad]
This was discussed on the mailing list for a long time and agreed that
using one MH type will help in preserving the MH type space. I believe
the "Heartbeat Mechanism for PMIPv6" is a wg doc in Netlmm and use one
MH type for the Request and Response. On the other hand, do see an issue
or problem in having a single MH type for both messages?

> 
> - BRI has a revocation trigger field which is used for two 
> main usages.
> One is the provisioning of the reason why the revocation was 
> sent (e.g.
> inter-MAG handoff) and the other is related to specific 
> binding revocation procedures (e.g. IPV4 HoA Binding only, 
> Per-Peer Policy). I think it would be cleaner if the two 
> concepts remain separated in the messages, for instance 
> defining additional flags for Per-peer policy or
> IPv4 HoA Binding only.

[Ahmad]
I see what you are saying. However, as you said, the Revocation Trigger
field is defined to give the reason which caused the revoking node to
send the BRI message. Thus far, I believe all of the defined values are
inline with that definition or reasoning. For example: When the LMA sets
the R. Trigger value to "IPv4 HoA Binding Only" it means that the reason
behind sending this BRI message is to revoke the IPv4 HoA address in the
case that the MN is assigned two proxy HoA(v4 & v6) for the same pCoA. I
do not see this as a policy decision, because it is no difference from
the MAG sending a BRI with R. Trigger value is set to for example,
"Access Network Session Termination"

As for the R. Trigger value of "Per-Peer Policy", This is only
restricted to Global Revocation when the (G) bit is set. I still believe
that "Per-Peer policy" also indicate the reason that allowed the LMA to
send this Global BRI. Do you have a different name for this R. Trigger
value that would fit better? 

> 
> - In the draft you refer to MAG identity, where is this term 
> defined? I wasn't able to find it in RFC 5213.

[Ahmad]
Actually, under section 4.1. "Peer Authorization Database (PAD) Example
Entries", you can find the MAG-ID is defined there as mag_identity_1. It
is the same concept here. However, I agree that we do not have a
mobility option which is specific for carrying MAG-ID but the draft is
using the MN-ID in a very specific scenario. How the LMA would check if
this MAG is authorized for Global revocation is out of scope.

>  
> 
> Some other comments related to specific sections:
> 
> - page 21: in the first section after the bullet list, there 
> is the following sentence:
> "As described in Section 7.3, the LMA SHOULD retransmit this BRI to
>    the MAG before deleting the mobile node IP tunnel to the mobile
>    access gateway until it receives a matching Binding Revocation
>    Acknowledgement or the BRIMaxRetransmitNumber is reached. "
> But this doesn't always apply, e.g. in case of inter-mag 
> handoffs. What am I missing?

[Ahmad]
Yes, I see what you are saying here. It seems that the text needs some
tweaking. 
Do you have any suggestion?

> 
> - why is the A bit setting mandatory in case of IPv4 HoA 
> binding only revocation?

[Ahmad]
May be if you tell me why not, we could change it?

> 
> - section 10.1.1: 
> "BRI MUST be formatted as in Section 6.1 and if the (P) bit is set,
>       the mobile access gateway must validate that the 
> impacted binding
>       have the proxy binding flag set."
> MAG is not supposed to have any proxy binding flag or is it? 
> How can it validate this flag?

[Ahmad]
Good catch. There is another incident below it too.
What about the following text for both bullets:
"
   o  BRI MUST be formatted as in Section 6.1 and the (P) bit is set.

   o  If the Global (G) bit is set and the Revocation Trigger field is
      set to "Per-Peer policy", the mobile access gateway identify all
      bindings that are registered at the LMA and hosted at the MAG.
      This Binding Revocation Indication does not include any other
      mobility options. In this case, the MAG MUST send a BRA with the
      appropriate status code to the LMA.
"

> 
> 
> -section 11.1
> " If the Acknowledgement (A) bit is set in the Binding Revocation
>       Indication and the MN has the BCE in registered state, 
> the mobile
>       node MUST send a Binding Revocation Acknowledgement."
> 
> MN has no BCE, it has a binding update list.
[Ahmad]
Right. Thx. What about the following:

   o  If the Acknowledgement (A) bit is set in the Binding Revocation
      Indication and the MN has a Binding Update List entry for the
source
      of the BRI message, the mobile node MUST send a Binding Revocation

      Acknowledgement. However, in all other cases when the (A) bit is
set 
      in the BRI, the mobile node SHOULD send a Binding Revocation
Acknowledgement.  
      In all cases, the mobile node MUST follow Section 11.2 when send 
      a BRA using the appropriate status code.

> 
> -section 11.1
> "If the Revocation Trigger field value is "Administrative Reason",
>       the mobile node MUST NOT try to re-register with the home agent
>       before contacting its home operator."
> 
> I don't think that BRI specs have to mandate the MN to 
> contact the home operator, the text at the end of section 
> 11.1 is enough IMO.
> 
[Ahmad]
I see your point, It seems a very strong requirement and for a well
behaved MN implementation, it may not be a problem to remove the whole
bullet. However, for a non-well behaved MN, it may be necessary to keep
something. What about if we demote MUST NOT to SHOULD NOT. Would that
work?


NEW TEXT:
   o  If the Revocation Trigger field value is "Administrative Reason",
      the mobile node SHOULD NOT try to re-register with the home agent
      before contacting its home operator.

TEXT at end of 11.1 that Patrick is referring to:

   The Revocation Trigger field value in the received Binding Revocation
   Indication could be used by the mobile node to define what action the
   mobile node could do to be able to register again and receive its IP
   mobility service, e.g. contacting its home operator.

> I have some typos and editorial corrections as well, I will 
> send them off-list.

[Ahmad]
Please send them. Thanks for your review and good comments!

> 
> Regards,
> 
> Patrick
> 
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