proposal for RIPE's IPv6-address space structure

Hello,

we want to present a proposal concerning the allocation of 
IPv6-address space within the RIPE-region on the basis of the 
Internet Draft "An IPv6 Provider-Based Unicast Address Format" [1], 
which itself is consistent with RFC 1884 [2] and RFC 1887 [3]. 

The proposal is based on the following assumptions.

A1. There will likely be a mixture of providers of different sizes.
A2. Small providers will grow to become large providers.
A3. Large providers will lose customers and become small providers.
A4. Organizations which need to be multi-homed to more than one 
    provider will request a Provider ID assignment.

These four assumptions are essentially taken from [1] (see section 
3.3). We add one further assumption:

A5. Internet Service Providers will mainly offer their service 
within one country.

Our proposal tries to achieve the following goals:

D1. The hierarchical address structure is to simplify routing or 
    rather to offset the growth of routing tables. (Aggregation)

D2. Address space should be sufficient for a long time - in principle 
    for ever. This leads to a conservative approach. (Conservation)

D3. It should accommodate ISPs and their customers (avoid reassignments,
    if possible; long-term address space planning for providers).

D2 and D3 are contrary in a way.


We propose the following address allocation scheme:


|FP+RegID|  Provider ID | Subscriber ID | Intra-Sub |
|        |  PRID | RPID |               |           |
+--------+-------+------+---------------+-----------+
| 8 bit  | 7 bit | n bit| (49 - n)      |  64 bit   |
+--------+-------+------+---------------+-----------+

with n = 17 !


PRID (Provider Region ID)
7 bit corresponds to 128 IDs. These are mainly reserved for the
countries of the 'natural', ie. European, RIPE-Region (A5).
Non-European domains supported by RIPE get their own prefix
(FP+RegID) in order to support a dedicated authority for
these regions in the future.

We should mention that we have discussed the possibility to 
subdivide the RIPE address space in such a way that the 
length of the Country-ID depends on the size (population)
of that country. In such a scheme big countries could get a 
5 or 6 bit long Country-ID (instead of 7 bit), resulting
in a larger address space for those countries.


RPID (Rest of Provider ID):
In principle 56 bit are available to address providers and
their customers. With n=17 there is room for 2^17 (= 131072)
providers per provider region (=country).

The remaining 32 bits are available to identify a customer.
Hence, each provider has as many customer networks available
as there are host addresses available with IPv4.

If this turns out not to be enough to satisfy the needs of
a very LARGE provider then, there should be the option to
double the assigned address space by adjoining the neighboring
address block. In order to do so RPIDs should be assigned in
multiples of 16 initially, leaving the option to half the
'reserved' address space but still keeping the option to
double.

Given a reasonable size for an ISP within an open market 
this compromise should address D2 as well as D3 still
leaving the option for some degenerated cases with just
a single prefix.

Different assumptions about the future growth and dynamics
of national Internet markets might result in a different
choice for n.

We hope that this proposal will serve at least as input for 
discussion.

References:

[1] Rekhter, Y., Lothberg, P., Hinden, R., Deering, S., 
    Postel, J., "An IPv6 Provider-Based Unicast Address Format",
    Internet Draft, March 1996.

[2] Hinden, R., "IP Version6 Addressing Architecture",
    RFC 1884, December 1995.

[3] Rekhter, Y., Li, T., "An Architecture for IPv6 Unicast
    Address Allocation", RFC 1887, December 1995.


Best regards

Frank Hoffmeister
Guido Loeffler
Juergen Rauschenbach


Author's Addresses:

Frank Hoffmeister
EUnet Deutschland GmbH		   Phone: +49 231 972 00
Emil-Figge-Str. 80		     Fax: +49 231 972 1188
D-44227 Dortmund	 	  E-Mail: Frank.Hoffmeister at Germany.EU.net

Guido Loeffler
JOIN project
University of Muenster		   Phone: +49 251 83 8458
Einsteinstr. 60			     Fax: +49 251 83 2678
D-48149 Muenster		  E-Mail: join at uni-muenster.de

Juergen Rauschenbach	
DFN-Verein			   Phone: +49 30 884299 46
Pariser Str.44			     Fax: +49 30 884299 70
D-10707 Berlin			  E-Mail: jrau at dfn.de