Subject: RE: mboned: I-D ACTION:draft-ietf-mboned-addrdisc-problems-00.txt

From: "Manfredi, Albert E" <[email-masked]>
Date: Mon, 4 Apr 2005 17:43:36 -0400

> From: Pekka Savola [mailto:[email-masked]]

> My reading of RFC2365 is pretty clear that the sites/enterprises that 
> use any other part of 239/8 rather than just 239.192.0.0/14 or
> 239.25[345].0.0/16 are basically violating the RFC.  IMHO, this is 
> pretty clear in 6.2.1:
> 
>     The ranges 239.0.0.0/10, 239.64.0.0/10 and 239.128.0.0/10 are
>     unassigned and available for expansion of this space.  
> These ranges
>     should be left unassigned until the 239.192.0.0/14 space 
> is no longer
>     sufficient. This is to allow for the possibility that future
>     revisions of this document may define additional scopes on a scale
>     larger than organizations.
> 
> In particular "allow for the possibility ..." clearly states that the 
> intent is NOT to use these addresses, so that in future we 
> could carve 
> out blocks from there if we wanted (exactly like a proposal was to do 
> now).

For future expansion, yes, but not for future expansion controlled by the IANA!

I'd say that the intent, also reflected in RFC 3171, is that the 239/8 block always be available for assignments made by organizations, much like RFC 1918. IANA is given access to the upper 256 in each scope only. This concept seems supported also by RFC 3171, which states:

9. Administratively Scoped Address Block (239/8)

   Addresses in the Administratively Scoped Address block are for local
   use within a domain and are described in [RFC2365].

9.1. Assignment Guidelines

   Since addresses in this block are local to a domain, no IANA
   assignment policy is required.

9.1.1. Relative Offsets

   The relative offsets [RFC2365] are used to ensure that a service can
   be located independent of the extent of the enclosing scope (see RFC
   2770 for details).  Since there are only 256 such offsets, the IANA
   should only assign a relative offset to a protocol that provides an
   infrastructure supporting service.  Examples of such services include
   the Session Announcement Protocol [RFC2974].  Pursuant to section
   4.4.2 of RFC 2780 [RFC2780], assignments of Relative Offsets follow
   an Expert Review, IESG Approval or Standards Action process.  See
   [IANA] for the current set of assignments.

> Two alternatives:
>   - use a non-239/8 space for these assignments (reason: just to make 
> it easier to block them in MSDP)
>   - just forget about it completely, pointing out that RFC 
> 2365 already 
> has a policy allowing obtaining scoped multicast addresses (however, 
> this is limited to 8 bits per scope, so this might not be sufficient 
> for long term)
> 
> Thoughts?

I'd say both of your options should be viable. From the point of view of the 239/8 range, seems to me that it's hard to say whether the "relative offsets" will run out first, or whether multicast addresses available to individual organizations will run out first. Is there a compelling reason now to violate RFC 3171?

Bert

_______________________________________________________________
user interface: http://darkwing.uoregon.edu/~llynch/mboned.html
web archive:  http://darkwing.uoregon.edu/~llynch/mboned/

---

From: Beau Williamson <[email-masked]>
Date: Mon, 04 Apr 2005 17:35:35 -0500

At 4/4/2005 04:43 PM, Manfredi, Albert E wrote:

>I'd say that the intent, also reflected in RFC 3171, is that the 239/8 
>block always be available for assignments made by organizations, much like 
>RFC 1918. IANA is given access to the upper 256 in each scope only. This 
>concept seems supported also by RFC 3171, which states:
>

Yes, exactly.  Thanks Bert, for pulling up the references that make this 
point.

Beau Williamson

---

From: Pekka Savola <[email-masked]>
Date: Tue, 5 Apr 2005 05:59:22 +0300 (EEST)

> For future expansion, yes, but not for future expansion controlled 

Not quite.

IMHO, it's clear that IANA does not have control over the "future 
expansion".  Rather, it is reversed _to the IETF_ for future expansion 
to.

That's why http://www.iana.org/assignments/multicast-addresses lists 
these blocks as:

  239.000.000.000-239.063.255.255 Reserved                    [IANA]

In all other contexts, when the address space is "reserved", it's not 
supposed to be used -- not by the users, nor assigned by IANA; 
until we IETF folks decide that the space is no longer reserved.

All these blocks have (IMHO) been reserved for the _IETF_ to decide 
what to do with them.

Too bad this is confusing, and to a degree slightly contradictory 
between 2365 and 3171..

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
_______________________________________________________________
user interface: http://darkwing.uoregon.edu/~llynch/mboned.html
web archive:  http://darkwing.uoregon.edu/~llynch/mboned/