[v6ops] Comments to draft-mlevy-v6ops-auto-v6-allocation-per-asn

[Dino Farinacci <[e-mail]>]

Sorry I am late on this thread. I just joined the list and read the discussion on this draft. Here are my comments from a LISP perspective. I am cross posting to the LISP WG mailing list.

Your draft text comes first indented and my comments follow.

> Network Working Group                                            M. Levy
> Internet-Draft                                        Hurricane Electric
> Intended status: Informational                               M. Pounsett
> Expires: July 28, 2013                                           Afilias
>                                                         January 24, 2013
> 
> 
>    A mechanism to allocate IPv6 blocks for BGP networks based on the
>                            networks AS Number
>           draft-mlevy-v6ops-auto-v6-allocation-per-asn-00.txt

We have been discussing in the LISP WG the allocation of a coarse IPv6 prefix for the use of Provider Independent EID prefixes.

> Abstract
> 
>    This document provides a methodology for automatically allocating
>    IPv6 [RFC2460] address blocks for networks that run BGP [RFC4271] and
>    are either single-homed or multi-homed [BARBER2011].  The automatic
>    allocation is taken from a specific /16 block assigned by IANA for
>    this purpose.
> 
>    Networks that require more than this single /48 can still request
>    additional allocations via the existing RIR process.  Networks are
>    not forced to use this allocation and can ignore this completely.
>    Availability of the /48 assignment via this mechanism does not change
>    existing mechanisms for obtaining IPv6 assignments through the
>    existing RIR (Regional Internet Registry) or LIR (Local Internet
>    Registry) mechanisms.

This is a good idea PROVIDED these prefixes are not injected into the core routing system.

> 1.  Introduction
> 
>    IPv6's massive address space provides a wonderful opportunity to
>    radically change the process of IP address allocation.  Presently
>    IPv6 allocation is the same process as used by the IPv4 world.  The
>    RIRs allocate IPv6 address blocks based on member requests and their
>    space requirements.  A minimum allocation of a /48 is believed to be
>    sufficient to start any enterprise in the world of IPv6.

Or a small set of devices that plan to be mobile. Where they do not want to reallocate addresses when they move.

> 2.  Defining the /48 address
> 
>    The /48 address is allocated using a fixed pattern.
> 
> 
>    ASN-based address assignment
>    +----------+--------------------+-----------------/ /------------+
>    | IANA /16 |     32 bit ASN     |   80 bits for IPv6 /48 space   |
>    +----------+--------------------+-----------------/ /------------+

This is similar in concept to the GLOP space we allocated for IPv4 multicast addresses. What we said is that anyone could join a group with a ASN-based address. That is, they did not have to own it.

Can the authors tell me if someone who owns such a prefix, will they be allowed to use and reallocate for any general purpose to other entities/organizations?

>    The sum of the bits in the IANA allocated /16 prefix plus the 32 bits
>    of the ASN plus the /48 of user defined usage adds up to 128 bits.
> 
>                       +------+----------------------+
>                       | Bits |                Usage |
>                       +------+----------------------+
>                       |   16 | IANA provided prefix |
>                       |   32 |                  ASN |
>                       |   80 |         User defined |
>                       |  128 |                TOTAL |
>                       +------+----------------------+
> 
>                         Table 1: Address space math

Can there be some ASN values assigned to signify "no one owns the /48"? So we can have even more independent assignments. For the purposes of LISP, we don't care if these address don't perfect aggregate because these addresses will go into the LISP mapping database system which may not need to aggregate since the RLOCs associated with the prefixes will be different anyways (and therefore can't aggregate or compress).

>    The end network can allocate out of the assigned /48 as needed.  It
>    is assumed that the end network will use this allocation for global
>    routing; however the network may choose to not announce this
>    allocation.

Okay, so lets use an example to see how this can be used. Let's say a /80 comes out of Verizon's space:

(1) Does Verizon allocate say a /64 to each of BMW, Mercedes, and Ford so they can use Vehicle ID Numbers for the rest of the allocation for their automobile EID assignments?

(2) Or do the RIRs believe they need to assign a /48 with distinct ASNs to each of BMW, Mercedes and Ford so they have more bits to embed VIN numbers?

(3) What if these auto manufactures don't want to allocate ASN numbers because they will never have any intent to run BGP either in the cars, POPs, data centers?

>    If any route is announced from this allocation, any prefixes more
>    specific than the allocated /48 must not be propagated in to the
>    global IPv6 routing table.  This is to prevent the IPv6 routing table

This is fine authors, but if you are multi-home, it will require each system at the site to possess multiple addresses one from each attached ASN if they do not have their own prefix but get it out of their provider.

If you say that this prefix will never be associated with a provider's attachment point, then I'm okay with that and agree.

>    from becoming too large.  Therefore, a site which uses this
>    allocation MUST NOT advertise a more specific than the allocated /48
>    routing prefix.  All native IPv6 network operators MUST filter out
> 
> 
> 
> Levy & Pounsett           Expires July 28, 2013                 [Page 3]
> Internet-Draft  Auto allocation mechanism for IPv6 blocks   January 2013
> 
> 
>    and discard any routing prefix advertisements longer than /48 from
>    within this /16 allocation.

Can you explicitly state then that this prefix for use as a PROVIDER INDEPENDENT prefix. Thanks.

> 3.  IANA allocated /16
> 
>    IANA is to allocate a /16 in a similar manner to the 2002::/16
>    allocation for 6to4 [RFC3068] which is used by the 6to4
>    protocol[RFC3056]..  No IPv4 allocation by IANA is required.

But in this case there is no implicit assumption about mapping to anything else with a bit-by-bit algorithm but rather an advertisement or another network-based mapping data structure. Correct?

>    ASNs are normally expressed as human-readable decimal numbers; yet
>    for this allocation the number should be converted into a hexadecimal
>    notation.  All IPv6 addresses are written in hexadecimal.  (NNNN
>    represents the /16 allocation by IANA)
> 
>        +----------------+--------------------+---------------------+
>        | ASN in decemal | ASN in hexadecimal |     Sample IP block |
>        +----------------+--------------------+---------------------+
>        |            AS1 |                  1 | NNNN:0000:0001::/48 |
>        |         AS6939 |               1B1B | NNNN:0000:1B1B::/48 |
>        |        AS29001 |               7149 | NNNN:0000:0001::/48 |
>        |       AS393220 |              60004 | NNNN:0006:0004::/48 |
>        +----------------+--------------------+---------------------+

What we had found in the old days of NSAP deployment (OSI) that encoding IPv4 addresses in BCD format in a hexadecimal longer address was extremely useful for management. And as we have seen for IPv6, even embedding IPv4 dotted decimal format was extremely useful.

Rather than having to build tools and make vendors do UI work, can we have some form of BCD format for AS number. I know this will be difficult for a 32-bit number but we could make it work for the ASNs that are <= 65535. Just a thought. But even 10 million ASNS would only take up to 8 nibbles. And since we won't and can't aggregate ASNs there is no point in making the encoding a power-of-2 value.

> 5.  ASN allocation
> 
>    ASNs are allocated by RIRs and this RFC does not handle that arena.
> 
>    ASNs defined as private ASNs MUST NOT use this scheme.  The special
>    16-bit ASN 23456 MUST NOT use this scheme.

I would let users do this with private ASes if they want to. Set a local/global bit in your encoding so they can use it. If you don't they will steal ASN numbers which they should not do but will.

> 6.  BGP Filtering and Validation
> 
>    Filtering would be a simple case of mapping the final ASN in a path
>    to the prefix in an exact bit-order match.
> 
>    For example; the prefix NNNN:0000:1B1B::/48 should only be seen as
>    announced from AS6939 (6939 equals 0x1B1B in hex).  Networks would
>    have their upstream transit providers add this /48 prefix to their
>    existing inbound BGP route filters.

IMO, these addresses should stay out of underlying routing. If you want to build a mobile Internet for IPv6, these sort of addresses are identity addresses and not topological.

Let's not perpetuate the non-sense of the past.

> 10.  Routing Table Impact
> 
>    This mechanism is not expected to have any impact to the global
>    Internet routing table since existing policies in the RIR system
>    already readily provide for the allocation of provider-independent
>    IPv6 prefixes.  Additionally, AS number holders are likely to be
>    multihomed entities which were going to be independently routed in
>    any case.  Service Providers are, as always, not obligated to route
>    these IPv6 assignments and/or may establish conditions of service
>    which offset any additional routing cost.

I would say it would have the same impact as PI prefixes do today.

> 14.2.  Informative References


You may, not sure, but may want to add these as possible informative references:

draft-ietf-lisp-eid-block
draft-iannone-lisp-eid-block-mgmnt

>    Martin J. Levy
>    Matthew Pounsett

Thanks for coming out with this,
Dino