[Mip4] flag bit conflict in Mobility Agent Advertisement Extension

[j-awano at az.jp.nec.com]

Each RFC3543 "Registration Revocation in Mobile IPv4" and RFC4857
"Mobile IPv4 Regional Registration" defines a new flag for Mobility
Agent Advertisement Extension.
These are X bit and I bit, respectively.

But these bits is the same position in Mobility Agent Advertisement
Extension!

In this case, what should we do?
I'm not sure but I guess RFC3543 is more frequently used than RFC4857.
(e.g. WiMAX forum refers to RFC3543.)
So, I wish RFC3543 could keep the position of X bit.

I hope this decision which RFC to be changed is made as soon as possible.

----------------------------------------------------------------------------
RFC3543 "Registration Revocation in Mobile IPv4"
3.1.  Advertising Registration Revocation Support

   Mobility agents can advertise their support of registration
   revocation with a modification to the Mobility Agent Advertisement
   extension described in [1].  An 'X' bit is introduced to indicate an
   agent's support for Registration Revocation.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |        Sequence Number        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Registration Lifetime      |R|B|H|F|M|G|r|T|U|X| reserved  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  zero or more Care-of Addresses               |
   |                              ...                              |

      X   The mobility agent supports Registration Revocation

----------------------------------------------------------------------------
RFC4857 "Mobile IPv4 Regional Registration"
8.1. Regional Registration Flag

   Regional Registration flag:

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Type      |    Length     |        Sequence Number        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |           Lifetime            |R|B|H|F|M|G|r|T|U|I| reserved  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                  zero or more Care-of Addresses               |
       |                              ...                              |

   The flag is defined as follows:

            Type    16 (Mobility Agent Advertisement)

            I       Regional Registration.  This domain supports
                    regional registration as specified in this document.
----------------------------------------------------------------------------

Regards,
Jun


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