Re: [MEXT] Processing of BRI (Binding Revocation) by MAG

Ahmad

My comments inline...

Thanks
S Magesh

  _____  

From: Ahmad Muhanna [mailto:amuhanna@nortel.com] 
Sent: Monday, January 19, 2009 7:40 PM
To: Magesh Shanmugam
Cc: mext@ietf.org; netlmm@ietf.org
Subject: RE: Processing of BRI (Binding Revocation) by MAG

Ahmad

I have a query regarding the handling of Binding Revocation by MAG for
individual binding session.  
Following is the scenario:

Scenario:

1. Proxy Mobile Initial Registration, MAG sends PBU to LMA with HNP option
set to ALL_ZERO for MN 1.
2. LMA in turn sends back PBA with 3 HNP(s) assigned to MN 1 and updates
Binding Cache Entry.
3. MAG updates Binding Update List entry and sends Router Advertisement to
the MN with all the 
    prefixes and prefix lifetime. 
    Note: MAG considers the prefix lifetime as binding lifetime and starts
Binding Lifetime timer.
4. Bi-directional tunnel is established between MAG and LMA.  
5. Prefix Route(s) are created for all the prefixes at MAG.
6. MN 1 gets one IP Address from the alloted 3 HNP(s).
7. LMA sends BRI message with one HNP (out of the alloted 3 HNPs) with
revoke trigger as 
   "ADMINISTRATIVE REASON".

After step 7, when MAG receives BRI message with only one HNP and MN-ID:

Queries:

1. Will MAG stop the binding lifetime timer (started after binding session
establishment), due to the
    received BRI message?
2. Will MAG delete the complete Binding Update List maintained for the MN
(MN 1) or will it delete
    only the corresponding HNP entry from the BUL and send RA message to MN
1 (eventhough
    the IP Address used by MN is not from the HNP received in BRI message)?
If it deletes only the
    corresponding HNP entry, what will happen to the Binding Lifetime timer?

[Ahmad]
If the LMA assigned 3 HNP for MN1, then if the LMA would like to revoke all
of the HNPs, the LMA have one of the following options:

1. Send BRI with MN-ID option ONLY. This means that all HNPs are revoked, or

[Magesh] If there are multiple interfaces (multi-homed) for the same MN,
will MAG remove the Binding Update List maintained for all the interfaces, 
as there is no Link Layer Identifier Option in the BRI message?

2. Send a BRI with MN-ID and all HNPs.

Although, the draft recommend Number 1 BUT does not prevent No. 2.

On the other hand, if the LMA sends a BRI with MN-ID and a single HNP, then
the MAG MUST consider the revocation of that single HNP and MUST NOT remove
the MN1 from the BUL.

[Magesh]
What will be the status of binding lifetime timer?  
Will the timer be running even though the single HNP is removed from BUL
entry (or will the timer be stopped).

IMO, if LMA tries to revoke a particular mobility session (Binding Cache
Entry), it has to send the MN-ID and all the 
HNP(s) allocated for the particular session.  Sending of one HNP out of the
allocated n HNP(s) should be 
treated as Invalid Case. The behavior should be same as PBU received from
MAG for De-Registration (where all the
HNP(s) allocated are present in the PBU message).

Hope this help.

Regards,
Ahmad 

Thanks
S Magesh