Re: [Mip6] Issue 73: v4 mapped address in IPv6 header

[Alexandru Petrescu <[e-mail]>]

Is the IPv6 Home Address a v4-mapped address?

Can I still use a EUI64-derived IPv6 Home Address when I use DS-MIPv6?

Will the MN have three Home Addresses when using DS-MIPv6? (a v4-mapped 
IPv6 address, a EUI64-derived IPv6 address and a IPv4 address).

Alex

Hesham Soliman wrote:
> 
>  > Yes, KAME support it too with your meaning.
>  > Can you revise this point?
> 
> => Sure, apologies for misprepresenting KAME's implementation. 
> 
> Hesham
> 
>  > 
>  > I basically understand the analysis.
>  > Thank you for the effort.
>  > 
>  > Koshiro
>  > 
>  > 
>  > 
>  > On 2007/02/26, at 16:14, Hesham Soliman wrote:
>  > 
>  > > Hi Koshiro,
>  > >
>  > >>> Mapped addresses are supported in all major OSs (with the
>  > >> exception
>  > >>> of KAME)
>  > >>
>  > >> Can you please explain what do you mean by "supported"?
>  > >>
>  > >> We can use mapped addresses inside a node with KAME,
>  > >
>  > > => I meant at least what you describe above. So by my meaning I  
>  > > guess KAME
>  > > supports it too.
>  > >
>  > >    but
>  > >> KAME rejects
>  > >> a packet
>  > >> which has a mapped address as the source or destination address.
>  > >
>  > > => Right, but as I mentioned below, I understand the reason for  
>  > > doing that
>  > > in general because it implies that there is no return address (in  
>  > > the case
>  > > of the src address), but this is not the case in DSMIP.
>  > >
>  > > Hesham
>  > >
>  > >>
>  > >> regards,
>  > >> Koshiro
>  > >>
>  > >>
>  > >>
>  > >> On 2007/02/26, at 12:07, Hesham Soliman wrote:
>  > >>
>  > >>>
>  > >>> Folks,
>  > >>>
>  > >>> This is the final issue listed on the tracker. This one is
>  > >> a bit long.
>  > >>>
>  > >>> Issue Text:
>  > >>> -----------
>  > >>>
>  > >>> the IPv4 mapped address has a special meaning by RFC
>  > >>> 2553 API.  It is not preferable to use the mapped address in IPv6
>  > >>> headers (See the following the drafts)
>  > >>> 	draft-itojun-v6ops-v4mapped-harmful
>  > >>> 	draft-cmetz-v6ops-v4mapped-api-harmful
>  > >>>
>  > >>> In our code based on KAME, the IPv6 implementation discard a IPv6
>  > >>> header which has the v4 mapped address for sanity at
>  > >> ip6_input() and
>  > >>> ip6_rthadr2().  We also need to add the mapped address in
>  > >> an address
>  > >>> list (the list of all addresses which the node has) to 
>  > receive the
>  > >>> header.  This is somehow uncomfortable because the mapped
>  > >> address is
>  > >>> actually not routable.
>  > >>>
>  > >>>> From Hesham:
>  > >>> => No one suggested that it should/would be routable. It's simply
>  > >>> used to keep the packet format. There is no routing based on this
>  > >>> information.
>  > >>>
>  > >>>> From Koshiro:
>  > >>> => I am not sure whether it's just an implementation issues.  But
>  > >>> putting
>  > >>> the mapped address in the address list in order to process
>  > >> the DSMIP
>  > >>> IPv6 header means the mapped address may be chosen as a
>  > >> source address
>  > >>> even the address is actually not routable.  To avoid 
>  > this, we need
>  > >>> e.g. an additional flag to distinguish the mapped address
>  > >> from others.
>  > >>> I think some implementers will not accept this.
>  > >>>
>  > >>> The above is not only the reason again the mapped address
>  > >> in the IPv6
>  > >>> header.  Please refer the draft-*-harmful.  So, my idea is
>  > >> to put HoA
>  > >>> in IPv6 header and kind of IPv4 CoA option to idicate it's
>  > >> IPv4 CoA.
>  > >>>
>  > >>> BTW, if you just want to keep the packer format, I think
>  > >> it's better
>  > >>> to use compatible address, or 6to4 address, or
>  > >> newly-defined address
>  > >>> for this purpose.
>  > >>>
>  > >>> Analysis:
>  > >>> ---------
>  > >>>
>  > >>> The resons listed in the issue text (and other reasons
>  > >> discussed in
>  > >>> the DT)
>  > >>> as well as their rebuttal are listed in this section. The first
>  > >>> reason for
>  > >>> using a different address format was that the use of
>  > >> mapped address
>  > >>> was not
>  > >>> recommended. The issue text refers to two drafts above. Those two
>  > >>> drafts
>  > >>> were discussed several years ago in 2002 (first v6ops
>  > >> meeting). The
>  > >>> only
>  > >>> issue that was agreed on in those drafts was that the mapped
>  > >>> address should
>  > >>> not be used as a routable address. Therefore, the issue
>  > >>> misinterprets the
>  > >>> agreement in the community. Also, the mapped address is
>  > >> not used as a
>  > >>> routable address in DSMIP. The drafts referred to above
>  > >> did suggest
>  > >>> the
>  > >>> removal of the v4 mapped address altogether from IPv6, but this
>  > >>> suggestion
>  > >>> was rejected and the drafts were not adopted. Mapped
>  > >> addresses are
>  > >>> supported
>  > >>> in all major OSs (with the exception of KAME).
>  > >>>
>  > >>> The issue text also suggests the use of a different 
>  > address format
>  > >>> (compatible address, 6-to-4, or a new address format). The
>  > >> compatible
>  > >>> address format was deprecated from the IPv6 address architecture
>  > >>> and the
>  > >>> mapped format is the recommended format for embedding IPv4
>  > >>> addresses in
>  > >>> IPv6. 6-to-4 addresses imply a specific tunnelling behaviour
>  > >>> (tunnelling to
>  > >>> the v4 address), which is not useful for our purposes. A new
>  > >>> address format
>  > >>> will be no different from the mapped address, which is
>  > >> designed for
>  > >>> this
>  > >>> purpose.
>  > >>>
>  > >>> Another concern that was raised against the use of the mapped
>  > >>> address was
>  > >>> that they are "implicit" in nature ad do not explicitly
>  > >> show the IPv4
>  > >>> address. However, IP stacks must check the src address in the
>  > >>> packet to
>  > >>> insure that is in fact a legal address (e.g. not multicast) in
>  > >>> ip6_input.
>  > >>>
>  > >>>
>  > >>> Recommendation:
>  > >>> --------------
>  > >>>
>  > >>> My recommendation is to reject this issue for several reasons:
>  > >>> a. There is no clear problem with the current format, i.e. what
>  > >>> breaks?
>  > >>> b. We've already removed the alt-CoA option in a previous
>  > >> issue, so
>  > >>> if we
>  > >>> accept this issue we'd have to introduce a new address format for
>  > >>> DSMIP.
>  > >>> This can take a long time and will yield the same result.
>  > >> Although,
>  > >>> if there
>  > >>> is something specific in the mapped address format that
>  > >> will cause
>  > >>> problems,
>  > >>> and a new address format will solve this problem then I'm
>  > >>> personally ok with
>  > >>> the new address format. However, we need to understand what that
>  > >>> problem is.
>  > >>>
>  > >>>
>  > >>>
>  > >>> Regards,
>  > >>> Hesham
>  > >>>
>  > >>>
>  > >>>
>  > >>>
>  > >>>
>  > >>>
>  > >>> _______________________________________________
>  > >>> Mip6 mailing list
>  > >>> [e-mail]
>  > >>> https://www1.ietf.org/mailman/listinfo/mip6
>  > >>
>  > >>
>  > >
>  > 
>  > 
> 
> 
> 
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