Re: [pim] IPv6 Inter-domain Multicasting and Address Assignments

[Tim Chown <tjc at ecs.soton.ac.uk>]

On Tue, Feb 20, 2007 at 03:41:33PM -0500, Gibbons, James wrote:
> 
>    Hello,
> 
> 
>    SI   International  represents  and  contracts  with  DITO  (DoD  IPv6
>    Transition  Office)  on  a number of IPv6 issues.  In this case we are
>    providing  DITO  with  a  white  paper  on IPv6 Inter-domain multicast
>    address   assignments   and  issues/problems  (expected  or  realized)
>    regarding IPv6 multicast implementations.
> 
>    To begin, I have gone over a number of RFCs (including RFC 3306, 3956,
>    3307,  2375,  4607,  ID draft-ietf-mboned-ipv6-multicast-issues-02.txt
>    among  others)  but they are vague as to actual working implementation
>    of  inter-domain  multicast  address  assignments and how they will or
>    might work proceed.

RFC3306 lets you create for yourself a globally unique multicast group
address where your unicast prefix (which is unique by allocation) contributes
towards the first 96 bits of the group address.

The missing bit is how you manage the last 32 bits, but that could be 
application determined if for example you used a /64 per application.
Or you can choose your own manually.
 
>    In IPv4 GLOP was developed but not widely used, where an organizations
>    ASN  is embedded in the 223.0.0.0 / 8 multicast range.  In IPv6 I have
>    seen  V6UPBM  (RFC  3306)  and  "Embedded  RP"  (RFC  3956) as similar
>    proposals for IPv6.

Yep.

>    However,  I  am  still  not  clear  of the "reality" of IPv6 multicast
>    address  assignments  especially  with  regards to globally unique (by
>    organization, domain, site, etc.) inter-domain multicast.

We're using RFC3306 and Embedded-RP group addresses for international
IPv6 multicast applications.
 
>    That is, how far have actual address assignments proceeded?

For 3306 you don't need an authority to hand it out, it's just there for
you to use implicitly by the format.
 
>    What is just proposed versus being implemented or to be implemented?
> 
>    Are there actual standards being followed?

A growing base of routers support Embedded RP... we've run that between
the UK and US academic networks; all router son path (mainly Cisco and
Juniper) support it.   No RP required :)
 
>    Are   there  known/expected  issues/problems  with  IPv6  inter-domain
>    multicast and address assignments?
> 
>    Maybe a quote from my actual assignment will further clarify what I am
>    looking for:
> 
>    "DITO  is  having  some concerns with IPv6 multicast address space and
>    how  it  should  or  should  not be provisioned.  You should start the
>    study  with  regards  to  how  IPv4 multicast addressing worked in the
>    past.   If  you  ever  worked  with  it you would know there was never
>    official  group  reservations  made  with  regards  to address blocks.
>    However,  this  was  never a real issue since its popularity died.  So
>    except  for  what  was deemed to be the well-known addresses there was
>    never  any  reservations, unlike how unicast is reserved.  One thought
>    might be the Army gets a block of addresses, Navy, and so on."

A big win for v6 is that you dont need an ASN for GLOP like v4, you can
just form multicast groups from your unicast allocated prefix(es).

And with a lot of /64's in an IPv6 site, you can (as we have) assign an
RFC3306 group range per application if you chose to do so.

The other nice thing about v6 multicast is the explicit scoping bits, which
make it easier to control where your traffic flows.

-- 
Tim

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