Subject: [mobile-ip] Mobile IPv6 I-D 18:BA status value

From: Hiroyuki OHNISHI <[email-masked]>
Date: Wed, 31 Jul 2002 13:32:04 +0900

I have some comments about BA status value in I-D 18.

1. Typo: status value for insufficient resources

*6.1.8. Binding Acknowledgement (BA) Message

             130   Insufficient resources
             ~~~~
             131   Home registration not supported

*9.5. Cache Replacement Policy
    When attempting to add a new "home registration" entry in response
    to a Binding Update with the Home Registration (H) bit set, if no
    sufficient space can be found, the node MUST reject the Binding
    Update and MUST return a Binding Acknowledgement to the sending
    mobile node, in which the Status field is set to 131 (insufficient
                                                                      ~~~~~~~~
    resources).

2: Question: status value 136
(Route optimization unnecessary due to low traffic)

I do not understand clearly how to use this status value.
I am not sure that I missed some information about usage of this status value.
The followings are my assumptions.

*Case 1
HA measures the traffic that pass trough the HA. and if the amount of 
traffic is low,
the HA notifies MN that route optimization is not needed.
This status value is sent to the MN as BA for MN's home registration.
(Receiving the BA with 136, the MN does not try to initiate RR.)

*Case 2
Or is this value related to following description in 6.1.2?

6.1.2. Binding Refresh Request (BRR) Message

    [...] When a mobile node receives a
    packet containing a Binding Refresh Request message and there
    already exists a Binding Update List entry for the source of the
    Binding Refresh Request, it MAY start a return routability procedure
    (see Section 5.2) if it believes the amount of traffic with the
                             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    correspondent justifies the use of route optimization.

This means MN judges whether the MN uses RO or not depends
on the amount of traffic with CN when it receives BRR.
And if the amount is low enough, it sends BA with 136 to the CN?

---
Hiroyuki

---

From: Jari Arkko <[email-masked]>
Date: Wed, 31 Jul 2002 10:50:40 +0300

>    mobile node, in which the Status field is set to 131 (insufficient

Right...

>    (see Section 5.2) if it believes the amount of traffic with the

Hmm... for sure this value is not for the home registrations. I don't
think the HA should be involved in traffic measurements either. If the
MN decides to not initiate RR and BU, it simply never sends any packets,
so the BRR does not need an error answer.

Where this error was meant to be used is when the CN supports RO, but
for this particular MN it does not want to give the service as it believes
there's too little traffic to benefit from RO.

Text is missing on how to use this.

However, I'm not really sure this is genuinely different from 130. 130
means "i don't have enough memory or signaling resources to establish
RO with you". Does that mean hitting a hard limit on available BCE entries,
or some value judgement on using a remaining BCE entry for this particular
MN, given some assessment of how much traffic we are going to have with that
MN? The trouble is, from the MN's point of view both of these look the same.
My suggestion is that we clarify the rules for using 130 and remove 136.

Issue #91.

Jari