Subject: [mobile-ip] New proposed sub-option (Alternate Tunnel End Point Address)

From: [email-masked]
Date: Thu, 14 Mar 2002 16:05:18 +0200

Hi all

I would like to propose a new type of sub-option to be used with 
Binding Acknowledgement messages.

Main motivation: 

In ForCES framework, it would be reasonable to use a different IPv6
addresses for a signaling end point (home agent address known by MN)
and for a tunnel end point (separation of control and forwarding planes). 
This would also be useful in case of virtual home link.

The usage of this sub-option could be configurable in home agent, and it 
should not have any major impacts to the current implementations. However 
for the separation to work when needed, this sub-option would be mandatory 
to implement in MN. Home agent's support for this option is not mandatory. 
It is home agent's decision when to use this sub-option if it supports it. 
The usage of this sub-option should not create any new security 
vulnerabilities because Auth sub-option is used in all BAs with this sub-option.

Proposed additional chapter to the draft:

5.7. Alternate Tunnel End Point Address

   Alternate Tunnel End Point Address   (alignment requirement: 8n+6)

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
                                      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                      |       5       |       16      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                                                               +
      |                                                               |
      +               Alternate Tunnel End Point Address              +
      |                                                               |
      +                                                               +
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      The Alternate Tunnel End Point Address sub-option is valid 
      only in Binding Acknowledgement destination options. The 
      Alternate Tunnel End Point Address field contains an address to
	use as the source address when tunneling packets from home agent
	to MN, and as the destination address when tunneling packets from
	MN to home agent. This sub-option is optional, and if home agent's
	own address is used as a tunnel end point address, this sub-option 
	SHOULD NOT be used. This sub-option MUST be honored by an MN when 
	present. Authentication data sub-option MUST be present in the same 
	Binding Acknowledgement.

	Home link renumbering will trigger home agent to sent Mobile Prefix 
	Advertisement with Binding Request destination option to MN. At the 
	end of this message exchange, home agent will sent Binding Acknowledgement
	back to MN using Alternate Tunnel End Point Address sub-option for new 
	tunnel end point address.

	At any time, home agent may notify MN about new tunnel end point address
	by adding Alternate Tunnel End Point Address sub-option to the Binding 
	Acknowledgement.

Rgs, Petteri Pöyhönen