Subject: (ngtrans) RE: v6[v4] address in ngtrans-bgp-tunnel

From: [email-masked]
Date: Tue, 21 Aug 2001 12:14:54 +0200

I guess you are right for ngtrans list discussion
I refer to draft-ietf-ipng-addr-arc-v3.06; it refers to RFC1933 for a case of use of v4 compatible addresses., BGP tunnel culd be another one
I am not trying to be legalistic, but the wording IPv4 nodes can be ambiguous: RFC1933 defines it as an IPv4 only or an IPv6/IPv4 node but the addressing ID does not clearly refer to that definition IMHO. So, somewhere, this should be made clear in the
addressing ID. Without the legalistic approach,I agree that mapped addresses could be used as well
gérard

Erik Nordmark <[email-masked]> on 21/08/2001 10:24:47

Please respond to Erik Nordmark <[email-masked]>

  To:          Gerard GASTAUD/FR/ALCATEL@ALCATEL              
                                                              
  cc:          Dave Thaler <[email-masked]>,   
               Dirk OOMS/BE/ALCATEL@ALCATEL, Tony Hain        
               <[email-masked]>, Erik Nordmark        
               <[email-masked]>, Steve Deering     
               <[email-masked]>, Jeremy DE                 
               CLERCQ/BE/ALCATEL@ALCATEL,                     
               [email-masked],                      
               [email-masked], [email-masked]      

  Subject      RE: v6[v4] address in ngtrans-bgp-tunnel       
  :                                                           

Folks, how about moving this discussion to the ngtrans list so that others
can chime in?

> My recollection of the interim meeting in Redmond/Washington is that v 4
> compatible addresses will not be removed from the addressing ID, and I made
> a remark to this effect. I believe this does not preclude removing their use
> in RFC2373 as talked about in London without objection.

I'm confused - isn't what you call "addressing ID" the update to RFC 2373?

> Thes addresses
> required global Ipv4 addresses. Their use is perfectly legal, and if routers
> suport them as mentioned in a previous mail, there is nothing wrong with
> this option.

The language in draft-ietf-ipngwg-addr-arch-v3 for these addresses explicitly
refer to the tunneling described in [TRANS]. Thus I don't come to
the conclusion that they can be used in other contexts.

> To use mapped address for BGP tunneling, one needs as a minimum
> to modify their definition in the address draft and in RFC 2373  since they
> represent for BGP tunneling dual stack routers as mentioned in a previous
> mail.

You seem to be interpreting things differently than I do.
Should we embark on a legalistic interpretation of the draft?
The sentence says:
   A second type of IPv6 address which holds an embedded global IPv4
   address is also defined.  This address type is used to represent the
   addresses of IPv4 nodes as IPv6 addresses.  This type of address is
   termed an "IPv4-mapped IPv6 address" and has the format:

To me, clearly an IPv4 node can also be an IPv6 node.
If it had said "IPv4-only node (can not have IPv6 support)" I'd agree
with you but that isn't what the document says.

> They require too global IPv4 addresses.

That isn't what section 2.5.5 says in draft-ietf-ipngwg-addr-arch-v3.

So, ignoring the legalistic interpretation of the specs, are
there technical reasons why you think IPv4-mapped address will not work?

  Erik

> But it  is likely that inside
> an AS, the IPv4 address of a BGP border router would be a global one (?).
> ISATAP format is define in Fred's ID which states that the format could be
> used for other purposes than ISATAP. This format is not yet included in the
> addressing ID. ISATAP for its own purposes, mandates to use any globally
> aggregatable 64-bit IPv6 routing prefix (whether from a  native IPv6
> assigned numbers authority or from a special-purpose numbering  scheme such
> as [6BONE][6TO4]) reserved by a local network administrator specifically for
> ISATAP purposes (native addresses must not be configured with an ISATAP PF).
> The embedded IPv4 s address can be private or public depending on the site
> numbering scheme. For BGP tunnel, it is likely that global address would be
> used in the AS. I believe that when this format is included in the
> addressing ID, there will be no reference to the use of the prefix by ISATAP
> which is defined in the ISATAP ID and may be in BGP tunnel. I am not sure we
> need a prefix per island, but the prefix should be meaningful in the AS site
> and as such should be configured in the border routers. As mentioned
> elsewhere, a site prefix could be used fec0::/ assuming MP-BGP does not
> mandate that this address is globally routable
> So, my opinion is: compatible addresses or isatap format. If BGP tunnel is
> the only remaining ID to use compatible addresses or H/R don't use it
> anymore, then I would vote for use of ISATAP. gérard
>
>
>
>
>
> "Dave Thaler" <[email-masked]> on 17/08/2001 19:57:52
>
>
>
>   To:          Dirk OOMS/BE/ALCATEL@ALCATEL, "Tony Hain"
>                <[email-masked]>, "Erik Nordmark"
>                <[email-masked]>, "Steve Deering"
>                <[email-masked]>, Jeremy DE
>                CLERCQ/BE/ALCATEL@ALCATEL, Gerard
>                GASTAUD/FR/ALCATEL@ALCATEL,
>                [email-masked],
>                [email-masked], [email-masked]
>
>   cc:
>
>
>
>   Subject      RE: v6[v4] address in ngtrans-bgp-tunnel
>   :
>
>
>
>
>

---

From: Francois Le Faucheur <[email-masked]>
Date: Wed, 22 Aug 2001 15:46:08 +0200

Hi,

I'd like to support Erik's argument in favor of selecting "IPv4-mapped IPv6 
address" for ngtrans-bgp-tunnel.

My perception is that:
         - "IPv4-mapped IPv6 address" are defined exactly for the purpose 
of conveying an IPv4 address in an IPv6 address format, which is precisely 
what we need to do in ngtrans-bgp-tunnel (for memory what we want to do is 
convey the IPv4 address of the BGP Next Hop inside a BGP advertsiement, but 
purely because of BGP encoding restrictions we are forced to convey it as 
an IPv6 address)
         - draft-ietf-ipngwg-addr-arch-v3-06.txt has already carefully 
replaced the term "IPv4-only" (which was used in RFC2373) by "IPv4" so 
there is no problem with current definition with the fact that the BGP 
router is dual-stack.
         - as Erik said, there does not seem to be any issue specific to 
IPv4-mapped address relating to the use of a private IPv4 address. If you 
use a private IPv4 address in an "IPv4-mapped address", then obviously the 
IPv4 address you convey is not globally routable, but that's what you've 
decided to do; note that in ngtrans-bgp-tunnel, the "IPV4-mapped IPv6 
address" itself is not used as a destination address of a v6 packet, so 
routers are not trying to route on it. Again, it is just used to carry the 
v4 address of a BGP Next Hop inside a BGP v6 advertisement in a format that 
does not break BGP encoding rules.

So, to me, the bottom line is:
         (i) current definition of "v4-mapped" exactly matches what we need
         (ii) I have not seen any technical issue in using those.

Am I missing something?

Thanks

Francois

At 12:14 21/08/2001 +0200, [email-masked] wrote:

>I refer to draft-ietf-ipng-addr-arc-v3.06; it refers to RFC1933 for a case 
>of use of v4 compatible addresses., BGP tunnel culd be another one
>I am not trying to be legalistic, but the wording IPv4 nodes can be 
>ambiguous: RFC1933 defines it as an IPv4 only or an IPv6/IPv4 node but the 
>addressing ID does not clearly refer to that definition IMHO. So, 
>somewhere, this should be made clear in the

_______________________
Francois Le Faucheur
Development Engineer, IOS Layer 3 Services
Cisco Systems
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