Subject: Re: mboned: draft-ietf-mboned-embeddedrp-05.txt: R=1 and P/T != 1

From: Pekka Savola <[email-masked]>
Date: Thu, 1 Jul 2004 22:04:14 +0300 (EEST)

On Fri, 25 Jun 2004, Jerome Durand wrote:
> What I don't really like is that we started with a 4 bits flag field 
> that could potentially gave us 16 values for the global flag field.
> 
> Now we know that if P=1 -> T=1 and if R=1 -> P=1 -> T=1
> 
> We are becoming very limited.
> As I don't thing router are processing one bit at a time :) I would 
> prefer we consider the entire value instead of the value of each bit.
> 
> I would have preferred we have said
> 
> Flag = 0011 means RFC3306 address
> Flag = 0111 means embedded-rp address
> 
> Keeping 0100 or 0110 or whatever for any other proposal that could come.
> But it is certainly a bit late...

There were other comments regarding this from the IESG, and I ended up 
having to revise the document yet again (for other reasons), so I 
modified the text a bit toward what you're saying and what folks have 
been arguing for for a while now:

[...]
   R = 1 indicates a multicast address that embeds the address on the
   RP.  Then P MUST be set to 1, and consequently T MUST be set to 1, as
   specified in [RFC3306].  In effect, this implies the prefix
   FF70::/12.

   The behavior is unspecified if P or T is not set to 1, as then the
   prefix would not be FF70::/12.  Likewise, encoding and the protocol
   mode used when the two high-order bit in "flgs" are set to 11
   ("FFF0::/12") is intentionally unspecified until such time that the
   highest-order bit is defined.

   In the case that R = 1, the last 4 bits of the previously reserved
   field are interpreted as embedding the RP interface ID, as specified
   in this memo. 
[...]

In effect, we're just specifying R=P=T=1 (== FF70::/12), and leaving 
the rest unspecified.

Let's see if that faces resistance.  That will leave us with options
to change the meanings of flags or the flag field if appropriate if
needed later on...

(Btw, the version I just submitted is at 
http://www.netcore.fi/pekkas/ietf/draft-ietf-mboned-embeddedrp-07.txt 
until published.)

-- 
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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---

From: Pekka Savola <[email-masked]>
Date: Fri, 2 Jul 2004 00:39:32 +0300 (EEST)

On Thu, 1 Jul 2004, Alex Zinin wrote:
> Note that this para and the two ones above are saying different things.
> The upper ones say: "this spec defines how to interpret the 0111 combination
> only", which is reasonable. The last one says "01?? means embedded RP".
> The text needs to be more precise. In fact, I think the last para could
> be safely removed, as the first two say enough and are correct.

This is the paragraph that states that "RIID" field is to be 
interpreted at all, so I think it still has some meaning.

However, I agree it might be contradictory, and it might be simpler to 
just add a note about RIID in the first paragraph.

If there are no objections, this might be something worth fixing if 
there's need for another revision, or an RFC-ed. note, if not.