Subject: RE: mboned: Addresses lost in RFC2365 ? + IANA multicast addresses document

From: "Manfredi, Albert E" <[email-masked]>
Date: Wed, 8 Feb 2006 11:39:48 -0500

RFC 2365 says that the site local scope can be expanded backwards, after
239.255.0.0/16 is all used up, presumably until you reach, going
downwards, 239.193.0.0. So I think that's what RFC 2365 expected to do
with the range 239.196.0.0 through 239.252.255.255 that you mention.
It's room for growth.

I took that to mean that organizations were permitted to expand that
way, without IANA intervention.

Organization local scope uses 239.192.0.0/14 until that's filled up, and
then it can expand downward too, until 239.0.0.0. Again, without IANA
intervention.

Seems to me that the IANA multicast address assignments you point to has
changed the intent of RFC 2365 somewhat, reserving what used to be the
expansion room of both site local and organization local scope regions.
Site local is now restricted to 239.255.0.0/16, and organization local
scope is only allowed to expand *upwards*, no longer downwards, until
239.251.255.255.

Is this an errata? To me, it's an update of RFC 2365, which is different
and more restrictive. I assume the IANA document to be an update to RFC
2365. And that this should somehow be reflected in the RFC Index?

Bert

> -----Original Message-----
> From: Dave Price [mailto:[email-masked]] 
> Sent: Wednesday, February 08, 2006 9:33 AM
> To: [email-masked]
> Cc: [email-masked]
> Subject: mboned: Addresses lost in RFC2365 ? + IANA multicast 
> addresses document
> 
> Dear All,
> 
> 	While exchanging emails with Pekka Savola
> I mentioned an issue which I think I may have
> mentioned on this list before.
> 
> RFC2365 defines "Administratively Scoped IP Multicast"
> for the IP range 239.0.0.0 -> 239.255.255.255
> 
> While it give uses for various regions within this
> space, it does not for instance define the use
> of  239.196.0.0 -> 239.252.255.255
> 
> Looking at
> 
> http://www.iana.org/assignments/multicast-addresses
> which claims to be updated to 18 January 2006,
> it defines...
> 
> the whole of 239.192.0.0 -> 239.251.255.255
> to be allocated to "Organization-Local Scope"
> 
> (rather than just 239.192.0.0/14 as in RFC)
> 
> and defines
> 
> 239.252.000.000-239.252.255.255 as "Site-Local Scope (reserved)"
> 
> Which of the documents should be considered correct or definitive ?
> 
> Whichever it is, should we not try to get either an errata
> to the RFC noted or get the IANA one changed depending
> on which is wrong.
> 
> Dave Price
> 	---------------------------------------------------------
> 	| David Price, Computer Science				|
> 	|							|
> 	|  Computer Science, University of Wales, Aberystwyth,	|
> 	|  Penglais Campus, Aberystwyth, Ceredigion, SY23 3DB	|
> 	|                                                       |
> 	| Email: [email-masked] WWW: http://www.aber.ac.uk/~dap |
> 	|  Phone: +44 1970 622428   FAX: +44 1970 622455	|
> 	---------------------------------------------------------
> 
> 
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---

From: Dave Price <[email-masked]>
Date: Wed, 08 Feb 2006 17:19:23 +0000

Dear Bert,

[email-masked] said:
> RFC 2365 says that the site local scope can be expanded backwards,
> after 239.255.0.0/16 is all used up, presumably until you reach, going

As far as I can see, in section 6.6.1, RFC2365 only talks explicitly about
expanding IPv4 local scope

> into the reserved ranges
>    239.254.0.0/16 and 239.253.0.0/16. However, these ranges should not
>    be utilized until the 239.255.0.0/16 space is no longer sufficient.

it does not talk about IPv4 local scope expanding lower than that.

That's my point about there being a "dead zone"
from 239.252.255.255 down to 239.196.0.0 in the RFC

[email-masked] said:
> Seems to me that the IANA multicast address assignments you point to
> has changed the intent of RFC 2365 somewhat, reserving what used to be
> the expansion room of both site local and organization local scope
> regions. Site local is now restricted to 239.255.0.0/16,

No, it does document expansion space downwards for "site local", in fact
further than the RFC as the IANA document goes down to 239.252.0.0
whereas the RFC only goes down to 239.253.0.0

[email-masked] said:
> and organization local scope is only allowed to expand *upwards*, no
> longer downwards, until 239.251.255.255.

They show it as "already" going to that upper value
with no restriction!

[email-masked] said:
> Organization local scope uses 239.192.0.0/14 until that's filled up,
> and then it can expand downward too, until 239.0.0.0. Again, without
> IANA intervention.

As you note, the IANA document shows this as "reserved" to
IANA with out a planned purpose.

The RFC in msection 6.2.1 about expansion of IPv4 Organization Local Scope
does indeed note expansion downwards, but says

> 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.

[email-masked] said:
> Is this an errata? To me, it's an update of RFC 2365, which is
> different and more restrictive. I assume the IANA document to be an
> update to RFC 2365. And that this should somehow be reflected in the
> RFC Index?

I suppose my position is that we seem to have enough confusion
about multicast addresses as it is and having two,
apparently authoritative, documents saying contradictory
things does not help.

Dave Price

---

From: Pekka Savola <[email-masked]>
Date: Wed, 8 Feb 2006 20:19:15 +0200 (EET)

> with the range 239.196.0.0 through 239.252.255.255 that you mention.

No, 6.1.1 only says:

    "The IPv4 Local Scope space grows "downward". As such, the IPv4 Local
    Scope may grow downward from 239.255.0.0/16 into the reserved ranges
    239.254.0.0/16 and 239.253.0.0/16. However, these ranges should not
    be utilized until the 239.255.0.0/16 space is no longer sufficient."

The "black hole" address space mentioned by Dave is not mentioned at 
all; it's clearly meant to be reserved for yet unspecified IETF use.

Similarly, 6.2.1 says:

6.2.1. Expansion of the IPv4 Organization Local Scope

    should be left unassigned until the 239.192.0.0/14 space is no longer

If those ranges were meant to be available for free expansion by the 
users, the last sentence wouldn't hold.  So, clearly the intent is to 
reserve those ranges *for the IETF* to define (with different scope 
semantics as necessary) in future documents.

> way, without IANA intervention.

This has been discussed in the past -- and I'm not sure it's useful to 
repeat that now -- but there is no such worrding in RFC 2365.

> 2365. And that this should somehow be reflected in the RFC Index?

I think it should be pretty clear that IANA webpages can not update 
standards-track RFCs.

The only possible short term fix here is correcting the IANA webpage 
to reflect to RFC 2365.  There may be some debate on what RFC 2365 
means, though :-).  After that, if folks feeel it's appropriate, we 
could try to figure out whether (and how) RFC 2365 could be updated to 
make this clearer.

.....

So my suggested IANA fix is:

In http://www.iana.org/assignments/multicast-addresses, replace:

OLD:
  239.000.000.000-239.063.255.255 Reserved                    [IANA]
  239.064.000.000-239.127.255.255 Reserved                    [IANA]
  239.128.000.000-239.191.255.255 Reserved                    [IANA]
  239.192.000.000-239.251.255.255 Organization-Local Scope   [Meyer,RFC2365]
  239.252.000.000-239.252.255.255 Site-Local Scope (reserved)[Meyer,RFC2365]
  239.253.000.000-239.253.255.255 Site-Local Scope (reserved)[Meyer,RFC2365]
  239.254.000.000-239.254.255.255 Site-Local Scope (reserved)[Meyer,RFC2365]
  239.255.000.000-239.255.255.255 Site-Local Scope           [Meyer,RFC2365]
  239.255.002.002  rasadv                                    [Thaler]

NEW:
  239.000.000.000-239.063.255.255 Reserved                    [IANA]
  239.064.000.000-239.127.255.255 Reserved                    [IANA]
  239.128.000.000-239.191.255.255 Reserved                    [IANA]
  239.192.000.000-239.195.255.255 Organization-Local Scope   [Meyer,RFC2365]
  239.196.000.000-239.251.255.255 Reserved                    [IANA]
  239.252.000.000-239.252.255.255 Site-Local Scope (reserved)[Meyer,RFC2365]
  239.253.000.000-239.253.255.255 Site-Local Scope (reserved)[Meyer,RFC2365]
  239.254.000.000-239.254.255.255 Site-Local Scope (reserved)[Meyer,RFC2365]
  239.255.000.000-239.255.255.255 Site-Local Scope           [Meyer,RFC2365]
  239.255.002.002  rasadv                                    [Thaler]

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
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