Subject: [Int-area] draft-fuller-240space-00.txt

From: Eliot Lear <[email-masked]>
Date: Mon, 17 Sep 2007 12:11:34 +0200

Dear all,

I bring to your attention draft-fuller-240space-00.txt.  This draft 
addresses 240.0.0.0/4, which is currently "reserved for future use."  
The authors believe that the future is rapidly approaching, and that we 
should begin to think about using this address space.  There are a 
number of potential uses.  All currently contemplated uses are for 
unicast address space.  If approved, this draft would require 
implementors to not generate errors in the face of these addresses.  
Obviously getting new code out there takes time.  During that time we 
can contemplate appropriate uses.

The draft is short.

Comments?

Thanks,

Eliot

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From: Joe Touch <[email-masked]>
Date: Mon, 17 Sep 2007 06:20:04 -0700

> can contemplate appropriate uses.

It doesn't seem appropriate to recommend behavior other than the current
until these addresses are actually allocated. They remain "reserved for
future use" until actually used, not before.

This draft is odd in that it is recommending an action (treat as
unicast) without actually defining the behavior of that space. "Partly"
defining that behavior isn't, IMO, a useful step forward.

Joe

-- 
----------------------------------------------------------------------
Joe Touch                Sr. Network Engineer, USAF TSAT Space Segment
               Postel Center Director & Research Assoc. Prof., USC/ISI

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From: Eliot Lear <[email-masked]>
Date: Mon, 17 Sep 2007 15:26:49 +0200

Joe,
> defining that behavior isn't, IMO, a useful step forward.

We claim that the space can and should be used as normal unicast space, 
just as old Class A, B, or C space.  What we don't know is whether it 
should be public or private, and we claim that there is no need to 
decide that question today because the coding for either is exactly the 
same.  Is there wording that you think would make this more clear?

Eliot

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From: Joe Touch <[email-masked]>
Date: Mon, 17 Sep 2007 06:37:47 -0700

> same.  Is there wording that you think would make this more clear?

Public and private space are coded differently in some cases - e.g., in
firewalls and other configuration software (not at the net layer, though).

Section 4 would need not to say "please allocate this space", not "leave
it reserved" (to paraphrase).

Other observations

- whether IPv4 is the 'future' or not, it doesn't seem appropriate to
consume the entirety of the remainder of the space for an existing use.
Perhaps not all /4 should be reserved, but some - a /6 or /7 - should be
left reserved.

- I'll leave to IANA whether the argument therein is sufficient to
allocate a /4 (minus a /6 or so); I don't think the case is made very
well, FWIW.

Joe

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From: Iljitsch van Beijnum <[email-masked]>
Date: Sat, 22 Sep 2007 17:10:28 +0200

> Comments?

    At the present time, most IP implementation consider any IP address
    in the range 240.0.0.0 through 255.255.255.255 to be invalid as the
    source or destination of a datagram.

This is untrue. _Most_ implementations have no problem with it.

I've thought about writing a draft like this myself and given the use  
for these addresses some thought. They'd be useful for things that do  
need global uniqueness, but can do without global reachability. A  
good example of that would be the numbering of network equipment. In  
ISP networks this can eat up a decent chunk of address space. Most of  
the devices in such networks are updated regularly so the addresses  
could be useful here relatively soon.

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From: Danny McPherson <[email-masked]>
Date: Sun, 30 Sep 2007 21:50:00 -0600

> This is untrue. _Most_ implementations have no problem with it.

Iljitsch,
I'd be quite interested in any empirical evidence you might have
in support of this statement.  Pointers welcome.

Thanks!

-danny