Subject: [mobile-ip] confusion in mipv6 I-D?

From: Frank Quick <[email-masked]>
Date: Thu, 02 Oct 2003 13:46:15 -0700

In 11.7.1, page 131:

"The care-of address for the binding MUST be used as the Source Address in 
the packet's IPv6 header, unless an Alternate Care-of Address mobility 
option is included in the Binding Update."

In same section, page 132:

"The mobile node MUST use its home address - either in the Home Address 
destination option or in   the Source Address field of the IPv6 header - in 
Binding Updates sent to the home agent."

I would recommend some additional explanation, since the Source Address 
can't hold both the home address and the care-of address.  It would appear 
that at least one of the two options is required to avoid the conflict.  If 
both options are present, what is the recommended content of the Source 
Address field?

Frank Quick
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From: Vijay Devarapalli <[email-masked]>
Date: Thu, 02 Oct 2003 15:01:50 -0700

well, these statements are used in differnt contexts.

Frank Quick wrote:

> In 11.7.1, page 131:
>
> "The care-of address for the binding MUST be used as the Source 
> Address in the packet's IPv6 header, unless an Alternate Care-of 
> Address mobility option is included in the Binding Update."

the above sentence is trying to say that the address (CoA) to which the 
MN is binding
the home address MUST be in the source address or in the alt CoA 
mobility option.

> "The mobile node MUST use its home address - either in the Home 
> Address destination option or in   the Source Address field of the 
> IPv6 header - in Binding Updates sent to the home agent." 

this sentence is trying to say the Home Address MUST be either in the 
Home Adress
option or in the source address. the source address is set to the Home 
Address when
the MN sends a Binding Update (for example for deregistration) from the 
home link.
ingress filtering in the visited link will always prevent the MN from 
setting the
source address to home address when the MN is on a visited link. the MN 
can use
home address as source address only in the home link.

>
>
> I would recommend some additional explanation, 

see section 6.1.7

>   The care-of address is specified either by the Source Address field
>   in the IPv6 header or by the Alternate Care-of Address option, if
>   present.  The care-of address MUST be a unicast routable address.
>   IPv6 Source Address MUST be a topologically correct source address.
>   Binding Updates for a care-of address which is not a unicast routable
>   address MUST be silently discarded.  Similarly, the Binding Update
>   MUST be silently discarded if the care-of address appears as a home
>   address in an existing Binding Cache entry, with its current location
>   creating a circular reference back to the home address specified in
>   the Binding Update (possibly through additional entries).
>
>   The deletion of a binding can be indicated by setting the Lifetime
>   field to 0 and by setting the care-of address equal to the home
>   address.  In deletion, the generation of the binding management key
>   depends exclusively on the home keygen token, as explained in Section
>   5.2.5.  (Note that while the senders are required to set both the
>   Lifetime field to 0 and the care-of address equal to the home
>   address, Section 9.5.1 rules for receivers are more liberal, and
>   interpret either condition as a deletion.)
>

and section 9.5.1

>   The specified care-of address MUST be determined as follows:
>
>   o  If the Alternate Care-of Address option is present, the care-of
>      address is the address in that option.
>
>   o  Otherwise, the care-of address is the Source Address field in the
>      packet's IPv6 header.
>
>   The home address for the binding MUST be determined as follows:
>
>   o  If the Home Address destination option is present, the home
>      address is the address in that option.
>
>   o  Otherwise, the home address is the Source Address field in the
>      packet's IPv6 header.
>  
>

Vijay

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From: Frank Quick <[email-masked]>
Date: Thu, 02 Oct 2003 17:01:08 -0700

I still wonder what happens if both the Alternate Care-of Address and the 
Home Address option are present.  In that case can the Source Address field 
be either of those addresses, or perhaps neither?

At 03:01 PM 10/2/2003 -0700, Vijay Devarapalli wrote:
>>"The care-of address for the binding MUST be used as the Source Address 
>>in the packet's IPv6 header, unless an Alternate Care-of Address mobility 
>the above sentence is trying to say that the address (CoA) to which the MN 
>is binding
>the home address MUST be in the source address or in the alt CoA mobility 
>option.
>
>>
>>destination option or in   the Source Address field of the IPv6 header - 
>>in Binding Updates sent to the home agent."
>
>this sentence is trying to say the Home Address MUST be either in the Home 
>Adress

Frank Quick

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From: Vijay Devarapalli <[email-masked]>
Date: Thu, 02 Oct 2003 17:13:41 -0700

the only restriction is that the source address on the BU MUST be a
topologically correct address (otherwise packet is dropped bu ingress
filtering).

> I still wonder what happens if both the Alternate Care-of Address and 
> the Home Address option are present.  In that case can the Source 
> Address field be either of those addresses, 

typically CoA when in visited link and home address when the MN is
on the home link.

> or perhaps neither?

yes. for example, a MN could have two Care-of addresses, CoA1 and
CoA2. in the Binding Update, it could set the source address to CoA1,
include CoA2 in alt CoA option and home address in the Home Address
option. when the HA processes this Binding Update, the home address is
bound to CoA2.

Vijay

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From: Frank Quick <[email-masked]>
Date: Thu, 02 Oct 2003 17:56:46 -0700

Thanks.  But in section 10.3.1:

"To begin processing the Binding Update, the home agent MUST perform the 
following sequence of tests:

...

   o  A Home Address destination option MUST be present in the message.

..."

11.7.1 says essentially the same thing on page 131:

"   o  The packet MUST contain a Home Address destination option, giving
       the mobile node's home address for the binding."

This seems to moot some of the text in 11.7.1, page 132:

Seems this sentence should only refer to the destination option for 
consistency.

At 05:13 PM 10/2/2003 -0700, Vijay Devarapalli wrote:
>>Home Address option are present.  In that case can the Source Address 
>>field be either of those addresses,
>

Frank Quick

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From: Brian Haley <[email-masked]>
Date: Fri, 03 Oct 2003 09:52:34 -0400

The MN can use its home address in both the source address field and the home 
address option (and the alternate care-of address for that matter) in the same 
packet, for example when it is de-registering with its home agent.  In that 
context the sentence seems correct.

-Brian

ps: mobile ipv6 discussions have moved to the [email-masked] mailing list

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From: Jari Arkko <[email-masked]>
Date: Fri, 03 Oct 2003 17:38:14 +0300

Brian Haley wrote:
> The MN can use its home address in both the source address field and the 
> home address option (and the alternate care-of address for that matter) 
> in the same packet, for example when it is de-registering with its home 
> agent.  In that context the sentence seems correct.

Yes.

--Jari