Subject: [netlmm] Question about handover procedure in PMIP6

From: "Soininen Jonne (NSN - FI/Espoo)" <[email-masked]>
Date: Fri, 17 Aug 2007 22:35:43 +0300

Hello everybody,

somebody asked me a question when doing an handover between two MAGs if 
the old MAG was supposed to send a deregistration message to the LMA 
before the old binding is going to be deleted - or will the new BU from 
the new MAG already delete the binding. I didn't remember this exactly, 
but I checked the spec. Actually, I couldn't find anything definite. I 
would guess the old MAG does not have to deregister itself for the 
packets to flow to the new MAG. In addition, I guess the new BU does 
change the routing to the new MAG. Am I right?

However, I don't think this is very clear in the document. I didn't 
really find any description of the actual handover at all. The only 
place where I found a hint of the handover procedures is in "5.8.1. 
Initial Proxy Binding Registration". Perhaps it would be good to add to 
the section 5.8 a section describing the actual handover. A signalling 
picture would not hurt either.

Or if I missed the description could you please point me to the section 
where the description is.

Cheers,

Jonne.

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---

From: Frank Xia <[email-masked]>
Date: Fri, 17 Aug 2007 14:52:22 -0500

Hi Jonne.

Probably, you can refer to our draft 
http://tools.ietf.org/wg/netlmm/draft-xia-netlmm-fmip-mnagno-01.txt

In fact , we also presented the draft in WiMAX inter-working  subteam.
http://www.wimaxforum.org/apps/org/workgroup/nwg/download.php/19971/latest/070816_NWG_Inter-ASNGW_Interface_Contribution.ppt

BR
Frank

---

From: "Soininen Jonne (NSN FI/Espoo)" <[email-masked]>
Date: Fri, 17 Aug 2007 22:59:50 +0300

Hi Frank,

Thanks for the references. However, I think the base spec has to be stand
alone and have the needed text inside the spec itself.

Cheers,

Jonne.

On 8/17/07 10:52 PM, "ext Frank Xia" <[email-masked]> wrote:

> http://www.wimaxforum.org/apps/org/workgroup/nwg/download.php/19971/latest/070
> 816_NWG_Inter-ASNGW_Interface_Contribution.ppt
> 
> BR
> Frank
> 

-- 
Jonne Soininen
Nokia Siemens Networks

Tel: +358 40 527 46 34
E-mail: [email-masked]

---

From: Sri Gundavelli <[email-masked]>
Date: Fri, 17 Aug 2007 19:21:36 -0700 (PDT)

Hi Jonne,

When a MAG detects that a  mobile node is no longer
attached to its access link, there are two possibilities:

a.) MN moved out of the PMIP6 domain
b.) Inter-MAG handoff (MN is attached to a different MAG)

The MAG will not be able to differentiate between the two,
unless there are context transfer/FMIP  schemes in place.

Now, as per the spec,

1.) MAG must ensure the mobile node is still on the access
link before extending binding lifetime with the LMA.
2.) If the MAG detects the mobile node is no longer attached
to the access link, it must deregister.

For scenario #a, this is sufficient and complete.

For scenario #b, #1 is correct. However, with #2, there
is potentially a race condition. The old MAG should
deregister only if there is no handoff. But, it would not
know that. However, it must deregister to make sure the
resources are cleaned up at the LMA, for covering scenario
#a.

The proposed solution (not the exact text):

- The LMA on receiving a Proxy Binding Update with
lifetime=0, SHOULD wait for MinDelayBeforeBCEDelete amount
of time before the BCE is deleted. However, it must
send the Proxy Binding Ack right away.

- During this time, if the LMA receives a non-zero
lifetime and with a later timestamp, it must not delete
the BCE,  but just update the entry.

Protocol Constant:

MinDelayBeforeBCEDelete = 1 Second (Default)

This issue was raised by Juny Kang, Kyungpook National Univ.

Thanks
Sri

On Fri, 17 Aug 2007, Soininen Jonne (NSN - FI/Espoo) wrote:

> Hello everybody,
>
> somebody asked me a question when doing an handover between two MAGs if the 
> old MAG was supposed to send a deregistration message to the LMA before the 
> old binding is going to be deleted - or will the new BU from the new MAG 
> already delete the binding. I didn't remember this exactly, but I checked the 
> spec. Actually, I couldn't find anything definite. I would guess the old MAG 
> does not have to deregister itself for the packets to flow to the new MAG. In 
> addition, I guess the new BU does change the routing to the new MAG. Am I 
> right?
>
> However, I don't think this is very clear in the document. I didn't really 
> find any description of the actual handover at all. The only place where I 
> found a hint of the handover procedures is in "5.8.1. Initial Proxy Binding 
> Registration". Perhaps it would be good to add to the section 5.8 a section 
> describing the actual handover. A signalling picture would not hurt either.
>
> Or if I missed the description could you please point me to the section where 
> the description is.
>
> Cheers,
>
> Jonne.
>
>
>

---

From: Vijay Devarapalli <[email-masked]>
Date: Sat, 18 Aug 2007 08:38:08 -0700

Sri,

I thought we concluded on ignoring a de-registration BU (where the 
lifetime is set to 0) from a MAG if there is a valid binding cache entry 
created by another MAG. In your case b) below, it is possible that the 
new MAG has sent a proxy binding update updating the binding cache entry 
already before the old MAG sends a de-registration BU.

> the BCE,  but just update the entry.

A particular LMA implementation could do this for every de-registration 
BU, but not when the binding cache entry has already been updated by the 
new MAG. In that case, the LMA just responds to the old MAG with a proxy 
binding ack with success status 0. No changes to the binding cache 
entry. And no starting the MinDelayBeforeBCEDelete timer.

Vijay

>> somebody asked me a question when doing an handover between two MAGs 
>> if the old MAG was supposed to send a deregistration message to the 
>> LMA before the old binding is going to be deleted - or will the new BU 
>> from the new MAG already delete the binding. I didn't remember this 
>> exactly, but I checked the spec. Actually, I couldn't find anything 
>> definite. I would guess the old MAG does not have to deregister itself 
>> for the packets to flow to the new MAG. In addition, I guess the new 
>> BU does change the routing to the new MAG. Am I right?
>>
>> Initial Proxy Binding Registration". Perhaps it would be good to add 
>> to the section 5.8 a section describing the actual handover. A 
>> signalling picture would not hurt either.
>>
>> Or if I missed the description could you please point me to the 
>> section where the description is.
>>
>> Cheers,
>>
>> Jonne.
>>
>>
>>

---

From: Sri Gundavelli <[email-masked]>
Date: Sat, 18 Aug 2007 08:55:44 -0700 (PDT)

Vijay,

We are talking about the case, where the dereg PBU from the
pMAG arrives at the LMA before the reg PBU from the nMAG
arrives. In that case, we cannot just delete the BCE, but
allow the PBU from the nMAG to arrive at the LMA. Allow the
make-before-break option.

For the other case you are referring too, the LMA will
ignore the message, as there is no BCE associated with
that pMAG/MN, the BCE would already be updated with the
PBU from the nMAG. Also, our earlier point of discussion
was in the context CMIP/PMIP intergrated scenario.

Sri

On Sat, 18 Aug 2007, Vijay Devarapalli wrote:

> Sri,
>
> I thought we concluded on ignoring a de-registration BU (where the lifetime 
> is set to 0) from a MAG if there is a valid binding cache entry created by 
> another MAG. In your case b) below, it is possible that the new MAG has sent 
> a proxy binding update updating the binding cache entry already before the 
> old MAG sends a de-registration BU.
>
> Sri Gundavelli wrote:
>>
>>  Hi Jonne,
>>
> A particular LMA implementation could do this for every de-registration BU, 
> but not when the binding cache entry has already been updated by the new MAG. 
> In that case, the LMA just responds to the old MAG with a proxy binding ack 
> with success status 0. No changes to the binding cache entry. And no starting 
> the MinDelayBeforeBCEDelete timer.
>
> Vijay
>
>>
>>  Protocol Constant:
>>

---

From: Vijay Devarapalli <[email-masked]>
Date: Sat, 18 Aug 2007 12:22:16 -0700

> was in the context CMIP/PMIP intergrated scenario.

Ok, we are on the same page. Your earlier email appeared to say that the 
tentative BCE timer is always created.

Vijay

>> lifetime is set to 0) from a MAG if there is a valid binding cache 
>> entry created by another MAG. In your case b) below, it is possible 
>> that the new MAG has sent a proxy binding update updating the binding 
>> cache entry already before the old MAG sends a de-registration BU.
>>
>> Sri Gundavelli wrote:
>>>
>>>  Hi Jonne,
>>>
>> A particular LMA implementation could do this for every 
>> de-registration BU, but not when the binding cache entry has already 
>> been updated by the new MAG. In that case, the LMA just responds to 
>> the old MAG with a proxy binding ack with success status 0. No changes 
>> to the binding cache entry. And no starting the 
>> MinDelayBeforeBCEDelete timer.
>>
>> Vijay
>>
>>>
>>>  Protocol Constant:
>>>
>>> > >  somebody asked me a question when doing an handover between two 
>>> MAGs if >  the old MAG was supposed to send a deregistration message 
>>> to the LMA >  before the old binding is going to be deleted - or will 
>>> the new BU from >  the new MAG already delete the binding. I didn't 
>>> remember this exactly, >  but I checked the spec. Actually, I 
>>> couldn't find anything definite. I >  would guess the old MAG does 
>>> not have to deregister itself for the >  packets to flow to the new 
>>> MAG. In addition, I guess the new BU does >  change the routing to 
>>> the new MAG. Am I right?
>>> > >  However, I don't think this is very clear in the document. I 
>>> didn't >  really find any description of the actual handover at all. 
>>> The only >  place where I found a hint of the handover procedures is 
>>> in "5.8.1. >  Initial Proxy Binding Registration". Perhaps it would 
>>> be good to add to >  the section 5.8 a section describing the actual 
>>> handover. A signalling >  picture would not hurt either.
>>> section >  where the description is.
>>> > >  Cheers,
>>> > >  Jonne.
>>> > > >