Re: Guidelines for Numbering IPv6 Point-to-Point Links and Easing the Addressing Plans

[JORDI PALET MARTINEZ <jordi.palet@consulintel.es>]

Hi Ole,

See below, in-line.

Regards,
Jordi




> De: Ole Troan <ot@cisco.com>
> Responder a: <owner-v6ops@ops.ietf.org>
> Fecha: Wed, 01 Mar 2006 19:15:45 +0900
> Para: <jordi.palet@consulintel.es>
> CC: "v6ops@ops.ietf.org" <v6ops@ops.ietf.org>
> Asunto: Re: Guidelines for Numbering IPv6 Point-to-Point Links and Easing the
> Addressing Plans
> 
>> We have submitted before yesterday a new draft, it seems is still not
>> available at the IETF repository, but meanwhile, the document can be reached
>> at:
>> http://www.consulintel.euro6ix.org/ietf/draft-palet-v6ops-point2point-00.txt
>> 
>> Comments welcome !
> 
>    3.  Numbering Interfaces
> 
>    Often, in point-to-point links, hardware tokens are not available, so
>    frequently they are manually numbered sequentially with most of the
>    bits cleared to zero.  This also match the need to keep certain bits
>    (u, g) cleared.  This numbering makes as well easier to remember the
>    interfaces, which typically will become numbered as 1 (with 63
> 
> point to point links, even though they don't have L2 addresses, do
> have link-local addresses. I don't know of any implementation which
> requires you to manually configure these. typically the implementation
> reuses a link-local from an interface with a L2 address.

I believe I taken most of this text from the IPv6 addressing document. Even
if that's not correct (meaning that you have always L2 addresses), most of
the providers that I worked with, prefer to use something like 1 and 2 for
easy numbering the links.

> 
>    4.  Routing Aggregation of the Point-to-Point Links
> 
>    Following this approach and assuming that a shorter prefix is
>    typically delegated to a customer, in general a /48 [4], it is
>    possible to simplify the routing aggregation of the point-to-point
>    links.  Towards this, the point-to-point link may be numbered using
>    the first /64 of a given /48.
> 
> using the first (or any) subnet of a larger prefix, breaks the
> conceptual model of DHCP prefix delegation. the prefix is delegated to
> the requesting router and cannot be used to number the link between
> the delegating and requesting router.

I just re-read the DHCP-PD document, and is not so clear to me that this
breaks the model (I mean strictly there is no any text that is against this
usage). Also, we have actually tested this, even with Cisco, and it works
;-)

If you mean that DHCP-PD concept is to delegate the complete prefix to the
requesting router, well, the user owning the CPE will not complain having
one less /64, but also is not so clear to me that we are stealing from them
a /64 because this is actually used to connect it ;-)

> 
> cheers,
> Ole
> 




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