Subject: RE: [Mip4] MIP RRQ Doubt

From: "Arunkumar Sivaraman" <[email-masked]>
Date: Fri, 20 Apr 2007 17:55:49 +0530

Thanks for the clarifications, Bjorn.

regards,
 
Arunkumar Sivaraman,
Airvana India Pvt. Ltd.,
Ph: +91-80-66189835.
 
"Truth is a bully we all pretend to like."

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
Bjorn Andersson
Sent: Friday, April 20, 2007 1:11 PM
To: Arunkumar Sivaraman
Cc: [email-masked]
Subject: Re: [Mip4] MIP RRQ Doubt

On 4/20/07, Arunkumar Sivaraman <[email-masked]> wrote:
> HA returning the same IP addr for the same NAI, will this be
> because of a policy or the general behavior of the HA?

Because of policy. I don't believe the RFCs take any stance on this
issue. Both behaviours will work, the other way is just not as
efficient. Well, on second thought, there can actually be a more
serious problem with allocating a new address in case the second reply
gets lost. Then the HA will be bound to the second address and the MN
will use the first, preventing any data to go through:

1. MN sends RRQ1
2. HA receives RRQ1, allocates addr1 and sends RRP1
3. MN sends RRQ2
4. RRP1(addr1) arrives at MN
5. HA receives RRQ2 removes binding to addr1, allocates addr2 and sends
RRP2
6. RRP2(addr2) gets lost

This is actually just a problem if nonces are used in the
identification field. According to the RFC nonces are allowed to be
resent unchanged for retransmissions. Timestamps must change for each
retransmission.

> So, is it also likely that a HA - not implemented on the lines stated
> above, can potentially end up assigning a new IP address, to a (rogue)
> MN repeatedly.

Yes, as long as the RRQ is authenticated. But then you know who is
causing the problems and can take actions as an
administrator/operator.

> Also, is there a reference in handling such scenario in the base rfc
> (3344) or in any updates.

Out of my head, I don't think so. Maybe there should be?

  Bjorn

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---

From: "Kent Leung \(kleung\)" <[email-masked]>
Date: Fri, 20 Apr 2007 22:07:57 -0700

Hi Arunkumar and Bjorn.

This dynamice home address assignment scenario is documented in case #7
in section 6.1 (
draft-paulkandasamy-mobileip-nai-based-home-addres-02.txt).  Pls feel
free to review the draft which is design to clarify some of the
implementation issues that we had encountered on RFC 2794.

To summarize the answer to this question, the HA should reply with the
same IP address in the its mobility binding entry for the MN.

Kent 

-----Original Message-----
From: Arunkumar Sivaraman [mailto:[email-masked]] 
Sent: Friday, April 20, 2007 5:26 AM
To: Bjorn Andersson
Cc: [email-masked]
Subject: RE: [Mip4] MIP RRQ Doubt

regards,
 
Arunkumar Sivaraman,
Airvana India Pvt. Ltd.,
Ph: +91-80-66189835.

-----Original Message-----

On 4/20/07, Arunkumar Sivaraman <[email-masked]> wrote:
> HA returning the same IP addr for the same NAI, will this be because 
> of a policy or the general behavior of the HA?

Because of policy. I don't believe the RFCs take any stance on this
issue. Both behaviours will work, the other way is just not as
efficient. Well, on second thought, there can actually be a more serious
problem with allocating a new address in case the second reply gets
lost. Then the HA will be bound to the second address and the MN will
use the first, preventing any data to go through:

1. MN sends RRQ1
2. HA receives RRQ1, allocates addr1 and sends RRP1 3. MN sends RRQ2 4.
RRP1(addr1) arrives at MN 5. HA receives RRQ2 removes binding to addr1,
allocates addr2 and sends
RRP2
6. RRP2(addr2) gets lost

This is actually just a problem if nonces are used in the identification
field. According to the RFC nonces are allowed to be resent unchanged
for retransmissions. Timestamps must change for each retransmission.

Yes, as long as the RRQ is authenticated. But then you know who is
causing the problems and can take actions as an administrator/operator.

  Bjorn

---

From: "Arunkumar Sivaraman" <[email-masked]>
Date: Sat, 21 Apr 2007 13:22:32 +0530

Kent,
  I went through the draft & also the particular section & case, referred in your last mail. The situation i've put in my mail isn't same as case #7. In the scenario i've given, the MN hasn't rebooted but is discarding the RRP(s) from the FA since it has waited for a reasonable time' - as per rfc 3344, for a RRP. So, if the MN is using the timestamp method to send new registration requests, then it will keep discarding the RRP(s) - even if the FA/HA keeps accepting each of its RRQ(s). 

  Can we have this as a case scenario in the draft?

  But it still begs the question, if a MN was doing this again & again, shouldn't the FA/HA  remove its binding after say 'n' such similar RRQ(s). 

All,

  On a related note, any reason why there isn't a specific time for a MN to wait for a RRP, before sending new RRQ(s) using the timestamp method. 

Thanks,

Arun

" If you're in a vehicle going at the speed of light, what happens when you turn on the headlights?"

-----Original Message-----
From: Kent Leung (kleung) [mailto:[email-masked]]
Sent: Sat 4/21/2007 10:37 AM
To: Arunkumar Sivaraman; Bjorn Andersson
Cc: [email-masked]
Subject: RE: [Mip4] MIP RRQ Doubt
 
Hi Arunkumar and Bjorn.

Kent 

-----Original Message-----
From: Arunkumar Sivaraman [mailto:[email-masked]] 
Sent: Friday, April 20, 2007 5:26 AM
To: Bjorn Andersson
Cc: [email-masked]
Subject: RE: [Mip4] MIP RRQ Doubt

regards,
 
Arunkumar Sivaraman,
Airvana India Pvt. Ltd.,
Ph: +91-80-66189835.

-----Original Message-----

1. MN sends RRQ1

  Bjorn

---

From: "Kent Leung \(kleung\)" <[email-masked]>
Date: Sun, 22 Apr 2007 21:24:18 -0700

Hi Arun.

It shouldn't matter if the MN rebooted or discarding RRP for some
reason.  The message flow is still the same.  I just reread your
original post and it appears to me that you are describing the same
situation of HA receiving an RRQ with Home Address field set to zero
(i.e. requesting dynamic home address) when it already has a mobility
binding for the MN.  Is this right?

This is what case #7 in the table in section 6.1 covers.  You had asked
if the HA should reply with same Home Address or a new IP address.  The
draft says HA assigns the same Home Address to the MN.  The scenario in
the draft is really just an example of when this event happens. 
 
Kent 

-----Original Message-----
From: Arunkumar Sivaraman [mailto:[email-masked]] 
Sent: Saturday, April 21, 2007 12:53 AM
To: Kent Leung (kleung); Bjorn Andersson
Cc: [email-masked]
Subject: RE: [Mip4] MIP RRQ Doubt

Kent,
  I went through the draft & also the particular section & case,
referred in your last mail. The situation i've put in my mail isn't same
as case #7. In the scenario i've given, the MN hasn't rebooted but is
discarding the RRP(s) from the FA since it has waited for a reasonable
time' - as per rfc 3344, for a RRP. So, if the MN is using the timestamp
method to send new registration requests, then it will keep discarding
the RRP(s) - even if the FA/HA keeps accepting each of its RRQ(s). 

  But it still begs the question, if a MN was doing this again & again,
shouldn't the FA/HA  remove its binding after say 'n' such similar
RRQ(s). 

All,

  On a related note, any reason why there isn't a specific time for a MN
to wait for a RRP, before sending new RRQ(s) using the timestamp method.

Thanks,

Arun

" If you're in a vehicle going at the speed of light, what happens when
you turn on the headlights?"
<snip>

---

From: "Arunkumar Sivaraman" <[email-masked]>
Date: Mon, 23 Apr 2007 16:44:42 +0530

Reply inline - [Arun].

Thanks,

Arun

" If you're in a vehicle going at the speed of light, what happens when you 
turn on the headlights?"

-----Original Message-----
From: Kent Leung (kleung) [mailto:[email-masked]]
Sent: Mon 4/23/2007 9:54 AM
To: Arunkumar Sivaraman; Bjorn Andersson
Cc: [email-masked]
Subject: RE: [Mip4] MIP RRQ Doubt
 
Hi Arun.

[Arun]: The scenario that i've put in is different. The difference being that in this scenario the MN thinks it hasn't registered yet with the HA - though the HA/FA are giving a 'sucess' response to all its RRQ. The MN is discarding this RRP because they don't match the timestamp of its latest RRQ.

So, there's a disconnect in the state of a call between MN & FA/HA. MN thinks for some reason it keeps getting RRP of expired RRQ(s), whereas the HA/FA already have the call as being in a registered state and therefore treat further RRQ(s) from the MN as being re-registrations.

I hope I have been able to get my point across :).

Kent 

-----Original Message-----
From: Arunkumar Sivaraman [mailto:[email-masked]] 
Sent: Saturday, April 21, 2007 12:53 AM
To: Kent Leung (kleung); Bjorn Andersson
Cc: [email-masked]
Subject: RE: [Mip4] MIP RRQ Doubt

Kent,

All,

Thanks,

Arun

---

From: "Chugtu Manish-a22653" <[email-masked]>
Date: Mon, 23 Apr 2007 20:07:54 +0800

Hi Arun, 

Just happened to go through this thread. I guess you have got most of
answers apart from that fact that your MN is in state of DISCONNECT as
it always happens to send a new RRQ before it gets a response for the
old one.

But I am not sure why would this happen. There sure is a timing issue
somewhere. I can understand MN missing the 1st RRP as the 2nd RRQ could
be sent in 1 second time, but the rest would be sent in 2xn time. This
is a lot of time for MN to get the RRP for the new RRQ it has sent
(Assuming HA is responding to it and its reaching the MN). So just
making sure MN is sending re-transmissions of RRQ according to RFC
should work.

Regards
Manish Chugtu

-----Original Message-----
From: Arunkumar Sivaraman [mailto:[email-masked]] 
Sent: Monday, April 23, 2007 4:45 PM
To: Kent Leung (kleung); Bjorn Andersson
Cc: [email-masked]
Subject: RE: [Mip4] MIP RRQ Doubt

Reply inline - [Arun].

Thanks,

Arun

-----Original Message-----
From: Kent Leung (kleung) [mailto:[email-masked]]
Sent: Mon 4/23/2007 9:54 AM
To: Arunkumar Sivaraman; Bjorn Andersson
Cc: [email-masked]
Subject: RE: [Mip4] MIP RRQ Doubt
 
Hi Arun.

[Arun]: The scenario that i've put in is different. The difference being
that in this scenario the MN thinks it hasn't registered yet with the HA
- though the HA/FA are giving a 'sucess' response to all its RRQ. The MN
is discarding this RRP because they don't match the timestamp of its
latest RRQ.

So, there's a disconnect in the state of a call between MN & FA/HA. MN
thinks for some reason it keeps getting RRP of expired RRQ(s), whereas
the HA/FA already have the call as being in a registered state and
therefore treat further RRQ(s) from the MN as being re-registrations.

 
Kent 

-----Original Message-----
From: Arunkumar Sivaraman [mailto:[email-masked]] 
Sent: Saturday, April 21, 2007 12:53 AM
To: Kent Leung (kleung); Bjorn Andersson
Cc: [email-masked]
Subject: RE: [Mip4] MIP RRQ Doubt

Kent,

All,

Thanks,

Arun

---

From: "Kent Leung \(kleung\)" <[email-masked]>
Date: Mon, 23 Apr 2007 08:36:48 -0700

As I mentioned before, pls look at the registration request/reply
exchange from the MN and HA.  What field is different between any of the
scenarios described so far?

As for your specific scenario, I don't see how this would typically
happen.  Why would MN's pending RRQ expire before the RRP is received?
Does it take 10 seconds or something?  It's a strange situation.  Looks
like a bug in the MN to me.

Anyways, I thought your main question was about how the HA deal with
such a case of receiving RRQ for dynamic HoA assignment when "HA/FA
already have the call as being in a registered state".  I won't answer
that again...

Kent

-----Original Message-----
From: Arunkumar Sivaraman [mailto:[email-masked]] 
Sent: Monday, April 23, 2007 4:15 AM
To: Kent Leung (kleung); Bjorn Andersson
Cc: [email-masked]
Subject: RE: [Mip4] MIP RRQ Doubt

Reply inline - [Arun].

Thanks,

Arun

-----Original Message-----
From: Kent Leung (kleung) [mailto:[email-masked]]
Sent: Mon 4/23/2007 9:54 AM
To: Arunkumar Sivaraman; Bjorn Andersson
Cc: [email-masked]
Subject: RE: [Mip4] MIP RRQ Doubt
 
Hi Arun.

 
 
Kent 

-----Original Message-----
From: Arunkumar Sivaraman [mailto:[email-masked]] 
Sent: Saturday, April 21, 2007 12:53 AM
To: Kent Leung (kleung); Bjorn Andersson
Cc: [email-masked]
Subject: RE: [Mip4] MIP RRQ Doubt

Kent,

All,

Thanks,

Arun