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

From: Pekka Savola <[email-masked]>
Date: Thu, 24 Jun 2004 10:39:31 +0300 (EEST)

Hi,

Alex Zinin raised an issue in the Embedded-RP spec at the telechat 
(otherwise, the comments have been straightforward):

====
>    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].

The spec needs to say what to do if R==1 && P==0 && T==0
====

I see that RFC3306 does not spell out the similar scenario either, 
but, in any case, I'm proposing to address this with:

====
   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].  If R = 1, but P is set to 0, the packet MUST
   be discarded.  The behaviour if T is set to 0 when P is set to 1 is
   derived from [RFC3306] and is unspecified in this memo.
====

The justification for this is that (IMHO) we only need to address the
case where R=1 but P=0 (i.e., there should be no prefix and embedded
RP makes no sense).  T does not matter for *this* specification as its
behaviour is derived from RFC3306, but the above also discards R=1,
P=0, T=0.  It leaves R=1, P=1, T=0 unspecified, because RFC3306 leaves
that unspecified.  I don't see why we should specify more than RFC3306
does.

I'd be interested if other people have quick opinions on this? (My 
inital plan is to publish the update taking IESG comments into the 
account today.)

-- 
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: Jerome Durand <[email-masked]>
Date: Fri, 25 Jun 2004 09:58:32 +0200

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...

As you see I don't give an answer, just a global comment.
BTW:
* is a flag 1010 possible ?
or is that forbidden by RFC3306 ?

* what about 1011 ?
does such a flag implies the multicast address depends on the prefix ?

Thanks

Jerome