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

From: "Manfredi, Albert E" <[email-masked]>
Date: Mon, 28 Mar 2005 19:35:46 -0500

> -----Original Message-----
> From: John Kristoff [mailto:[email-masked]]

> I don't share Beau and Albert's concerns about using a block in 239/8,
> but I also don't share their experience so they are probably on to
> something.  I would like to say that I feel very little sympathy for
> anyone or organization who considered 239/8 to be like RFC 1918 space.
> It seems to me those folks failed to properly implement RFC 2365 (and
> that includes my current organization :-).

Let me clarify my position. Maybe we aren't communicating precisely enough.

I've been assigning parts of the upper 239/8 space, per RFC 2365, to be configured identically for multicast groups inside different (mobile) platforms. These multicasts are not to go outside the boundaries of each platform's control system network.

So indeed, I'm using a portion of the 239/8 space very much like RFC 1918 address blocks for unicasts are used. I need to know that these multicasts will remain inside the local nets of each platform, that assignments can be reused in each platform (also for ease of configuration), and that the addresses are never going to conflict with those of larger scope multicasts in these platform networks (e.g. multicasts between platforms or between different nets on a given platform).

239.255.255.0 to 239.255.255.255 is for IANA assignment.

239.255.0.0 to 239.255.254.255 is the range I'm using now, in the 239/8 range.

From RFC 2365:

---------------
6.1. The IPv4 Local Scope -- 239.255.0.0/16

   239.255.0.0/16 is defined to be the IPv4 Local Scope.  The Local
   Scope is the minimal enclosing scope, and hence is not further
   divisible. Although the exact extent of a Local Scope is site
   dependent, locally scoped regions must obey certain topological
   constraints.

9. Structure and Use of a Scoped Region

   The high order /24 in every scoped region is reserved for relative
   assignments. A relative assignment is an integer offset from highest
   address in the scope and represents a 32-bit address (for IPv4). For
   example, in the Local Scope defined above, 239.255.255.0/24 is
   reserved for relative allocations. The de-facto relative assignment
   "0", (i.e., 239.255.255.255 in the Local Scope) currently exists for
   SAP [SAP].
   ...

9.1. Relative Assignment Guidelines

   Requests for relative assignments should be directed to the IANA. The
   IANA will be advised by an area expert when making relative address
   assignments. The area expert will be appointed by the relevant Area
   Director.
---------------

At this time, speaking for myself, I would have no problem with IANA assignment first come first served of the 239.0.0.0 through 239.254.255.255 space, but I can see that other organizations might have. RFC 2365 has been around for 7 years!

As far as I can tell from RFC 2365, the IANA has access to 256 addresses in the 239/8 range, and I'm not using those. Perhaps that was our misunderstanding? Those upper 256 addresses are legitimately theirs to assign.

Bert

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---

From: John Kristoff <[email-masked]>
Date: Mon, 28 Mar 2005 20:25:48 -0600

On Mon, 28 Mar 2005 19:35:46 -0500

> Let me clarify my position. Maybe we aren't communicating precisely enough.

Sorry Albert.  Let me also clarify.  As I recall, you were initially
opposed to any further assignment by IANA within 239/8, which is why
I referred to you by name.  Fair enough.  What I was also calling out
was any use in the currently reserved space, such as 239.0.0.0/10.  I
was associating use of all the 239/8 space as if it was all RFC 1918
space.  I suspected that perhaps you were using all of 239/8, but I
didn't know for sure.  I believe Beau has indicated multiple times that
he knows of a number of places using addresses throughout 239/8.  Sorry
for insinuating that you were part of that group (and I'm not putting
Beau in that group either, just some of his customers :-).  Thanks for
clarifying.

> At this time, speaking for myself, I would have no problem with IANA
> assignment first come first served of the 239.0.0.0 through
> 239.254.255.255 space, but I can see that other organizations might
> have. RFC 2365 has been around for 7 years!

I don't think anything other than something from the currently reserved
239/8 space could even be considered, but as I think Pekka's document is
trying to capture in some form and I think we are in consensus about, it
is probably not a viable solution to use statically assigned, globally
unique, local scope addressing.

John

---

From: Beau Williamson <[email-masked]>
Date: Tue, 29 Mar 2005 01:11:02 -0600

At 3/28/2005 06:35 PM, Manfredi, Albert E wrote:
>239.254.255.255 space, but I can see that other organizations might have. 
>RFC 2365 has been around for 7 years!

But it does not in any way imply that these address are assigned by IANA 
other than Scope Relative addresses.  This is still simply "private" 
address space. Period.

>As far as I can tell from RFC 2365, the IANA has access to 256 addresses 
>in the 239/8 range, and I'm not using those. Perhaps that was our 
>misunderstanding?

Yes, I believe you misunderstand Scope Relative addresses.  This are the 
top 256 addresses of any arbitrary scope defined within the 239/8 address 
space.  There is only one well-defined scope and that is the Site-Local 
239.255/16 space which is considered the smallest scope possible.  This was 
(well)defined so that applications like MADCAP would have a well-known 
starting address in the smallest scope in the organization.

>Those upper 256 addresses are legitimately theirs to assign.

Yes, and no.  They can assign the Scope Relative addresses which are 
"relative" to the top of EVERY arbitrary scope inside of 239/8. Since the 
Site Local scope is well-known at 239.255/16, that means the Scope Relative 
addresses for this scope is in the range of 239.255.255/24.

Beau