Subject: [Mip6] A question in my apprehension of draft 24

From: "Lee Garth" <[email-masked]>
Date: Tue, 16 Dec 2003 03:56:57 +0000

Hello to all:

    I am now reading draft 24, and found a qustion difficult for me to 
answer.

    As described in Section 6.3, Home Address Destination Option attached 
to an IPv6 packet contains the Mobile Node's home address, while the Source 
Address field in the packet is the mobile node's CoA. This is said to be 
the rule of forming payload packets sent by a mobile node to a 
correspondent node. But in Section 9.3.1, draft say when calculating the AH 
value, we must assume that Home Address Destination Option contains CoA of 
the sending mobile node, and the Source Address field is home address. It 
seems contradictory to me.
    Same thing happened when I try to grasp the meaning of the Type 2 
Routing Header. In section 6.4 discussing the format of it, correspondent 
node should use this routing header to contain the receiving mobile node's 
home address. But Section 9.3.2 says when an IP packet only have a single 
Type 2 Routing Header, it should contain the mobile node's CoA, while the 
destination address field should be the mobile node's home address.
    I know it must be my reason that I haven't fully understand the entire 
process of MIPv6 in draft 24. But I am really confused with my question 
above. If someone ardent and proficient here should help me, I will be very 
thankful.
    Good Day
                                                                Yours
                                                                     
garthdawn

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From: Jari Arkko <[email-masked]>
Date: Tue, 16 Dec 2003 13:22:23 +0200

Lee Garth wrote:

> to an IPv6 packet contains the Mobile Node's home address, while the 
> Source Address field in the packet is the mobile node's CoA. This is 
> said to be the rule of forming payload packets sent by a mobile node to 
> a correspondent node. But in Section 9.3.1, draft say when calculating 
> the AH value, we must assume that Home Address Destination Option 
> contains CoA of the sending mobile node, and the Source Address field is 
> home address. It seems contradictory to me.

Its like the rule says: when calculating the authenticator,
the packet should be assumed to be in the latter form. Otherwise
e.g. on the wire its in the Section 6.3 form.

The reason behind this is to ease the calculation of the authenticator
in a typical implementation, where the receiver would swap the addresses
as it encounters a HAO, so that for upper layers it would look like the
packet arrived from the home address.

> Routing Header. In section 6.4 discussing the format of it, 
> correspondent node should use this routing header to contain the 
> receiving mobile node's home address. But Section 9.3.2 says when an IP 
> packet only have a single Type 2 Routing Header, it should contain the 
> mobile node's CoA, while the destination address field should be the 
> mobile node's home address.

Same answer & reasoning.

Hope this helps -- let me know if you have further
questions.

--Jari