[6lo] About the GAAO option format

[Luigi IANNONE <[e-mail]>]

Hello 6lo WG,

In order to move the GAAO idea forward,  we would like to have some help and gather more feedback about it, in particular on the proposed format.
(The full document can be found at: https://datatracker.ietf.org/doc/draft-iannone-6lo-nd-gaao/)

The proposed format  of the option is:
~~~
  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    | Status/PfxLen |    Opaque     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R|F| P | I |Rsd|     AAF       |     Assignment   Lifetime     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
|                        Address/Prefix                         |
|                          (128 bits)                           |
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~~~

(for convenience the definitions as for the current document is provided at the bottom of this mail)

Points we would like to have feedback/opinions/help are:

1) Type; Length; Status/Pfxlen; AAF; Assignment Lifetime, F (defined in draft-thubert-6lo-prefix-registration); P (defined in draft-6lo-multicast-registration)
They are the minima to make the mechanism work we do not see particular changes to be done on these. Anyone having a different opinion?

2) About flags I and Opaque:
RFC8505 defines them to be used: “I=0 indicates that the Opaque  field carries an abstract index that is used to decide in which routing topology the address is expected to be injected.”
This was also pointed out by Pascal during last meeting, imply that strict coherence with EARO format is not necessary.
Our thoughts were to use I+Opaque in GAAO to request a prefix/address in  a specific routing topology, so that the same fields can be set in the registration following GAAO. Does it make sense?
Can be the default option I=0 + Opaque =0?  Or is it not so useful?

3) Another question not discussed so far is about ROVR. Does it make sense to use it as an ID in prefix requests? To be used as a token for the transaction? Any opinion?

Thank you in advance for any feedback.

Ciao

Luigi & David


~~~~~~
Fields definition

Option Fields:

   Type:  42 (Suggested)

   Length:  8-bit unsigned integer.  The length of the option in units
      of 8 bytes.  This field is set to 1 when the option is used in NS
      messages.  It is set to 3 when this option is used in NA messages
      because the assigned address/prefix is appended to the option.

   Status/PfxLen:  8-bits unsigned integer.  It indicates the Prefix
      Length of the assigned address if the assignment is successful.
      On success, the returned GAAO will have appended to it the
      assigned address/prefix and in this case the Length field will be
      set to 3.  This field can indicate an error code (See table 1 in
      [RFC8505] for error codes) if the assignment failed.  On failure,
      the returned GAAO message will not have any address/prefix
      appended to it.  Hence it will have the Length field set to 1,
      indicating a failure, whose code is indicated in this field.  This
      field MUST be set to 0 in NS messages.

   Opaque:  As defined in [RFC8505].

   R (Reserved):  This field is unused.  It MUST be initialized to 0 by
      the sender and MUST be ignored by the receiver.

   F:  F-Field as defined in [I-D.thubert-6lo-prefix-registration].

   P:  P-Field as defined in [I-D.thubert-6lo-prefix-registration]
      indicating the type of address requested.

   I:  As defined in [RFC8505].

   R (Reserved):  This field is unused.  It MUST be initialized to 0 by
      the sender and MUST be ignored by the receiver.

   Address Allocation Function(AAF):  1-byte unsigned integer.  Describe
      the allocation function (AF), i.e. the algorithm, used to assign
      the address/prefix. 0 is a special value indicating that the field
      is not used.  On request this field can be set to 0 to indicate
      there is no preference on how the address is assigned.  If
      different from 0 it means that it is requested to use a specific
      AAF to assign the address/prefix.

   Assignment Lifetime:  16-bit integer, expressed in minutes.  In NS
      message the field expresses the minimum requested lifetime.  In NA
      messages it expresses the maximum lifetime.

   Address/Prefix:  128-bits address or prefix returned in a GAAO option
      in an NA message.  This field is not present in GAAO requests in
      NS messages or in the NA message when an error occurs.



[e-mail]<mailto:[e-mail]>
Paris Research Center
Huawei Technologies France S.A.S.U.
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