Subject: [MBONED] Site local addresses for MANET

From: Marshall Eubanks <[email-masked]>
Date: Fri, 11 May 2007 09:42:28 -0400

I wonder if people have seen this :

http://www.ietf.org/internet-drafts/draft-ietf-manet-iana-02.txt

The part that troubles me is the desire for a site local address in  
239 :

4.1.  Site-local Scoped Multicast Group for IPv4

    For IPv4, well-known, scope-relative multicast address (as  
defined by
    [RFC2365], Section 9) are used.  The offset for the scope relative
    address for scoped MANET Routers is TBD4 to appear in
    [IANAv4Multicast] registry.

    Different scopes are defined by [RFC2365].  The IPv4 Local Scope
    (239.255.0.0/16) is the minimal enclosing scope for administratively
    scoped multicast and not further divisible -- its exact extent is
    site dependent.

    For the IPv4 Local Scope, applying the rules of [RFC2365] and using
    the assigned offset of TDB4, the multicast address is therefore
    239.255.255.(255-TBD4).

At present, only one 239 "Site-Local" address has been assigned -  
rasadv by Dave Thaler,

  239.255.002.002

There has been concern expressed that IANA assigned addresses in 239  
might collide with existing
deployments using 239 local addresses. However, 239.255.2.2 is being  
used by Microsoft Windows, which
indicates to me that it should be OK to assign a Manet address up in  
239.255/16.

Comments or suggestions would be appreciated. I would also be  
interested if Dave Thaler or Dave
Meyer remembers why 239.255.2.2 was chosen, instead of something in  
239.255.1.X.

I would regard this as a test case - if there is consensus to move  
forward on this one, there will be more.

Regards
Marshall

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From: Brian Haberman <[email-masked]>
Date: Fri, 11 May 2007 09:53:49 -0400

Hi Marshall,
     I will make the same comment here that I made on the MANET list.
It is unclear why the MANET WG wants to reserve site-local multicast
addresses (IPv4 and IPv6) without a clear definition of how they would
be used.  I have seen some hand-waving around auto-configuration, but no
concrete proposal on *how* these addresses would be used.

     Reminds me of the paranoia to reserve addresses "just in case".

Regards,
Brian

Marshall Eubanks wrote:
> The part that troubles me is the desire for a site local address in 239 :
> 
>    For IPv4, well-known, scope-relative multicast address (as defined by
> At present, only one 239 "Site-Local" address has been assigned - rasadv
> by Dave Thaler,
> 
>  239.255.002.002
> 
> Comments or suggestions would be appreciated. I would also be interested
> if Dave Thaler or Dave

---

From: Brian Haberman <[email-masked]>
Date: Fri, 11 May 2007 09:53:49 -0400

Hi Marshall,

Regards,
Brian

---

From: Marshall Eubanks <[email-masked]>
Date: Fri, 11 May 2007 10:55:50 -0400

> concrete proposal on *how* these addresses would be used.

That is fair enough. However, that is a MANET WG question, and I was  
hoping for
some guidance here on the general question of site-local assignments.

Do you know if this has become a topic in the autoconf WG ? A search  
of the WG mail list doesn't reveal it.
It would seem that multicast addresses for auto-configuration should  
be addressed there.

Regards
Marshall

>> rasadv

---

From: Marshall Eubanks <[email-masked]>
Date: Fri, 11 May 2007 10:55:50 -0400

Regards
Marshall

---

From: "Manfredi, Albert E" <[email-masked]>
Date: Fri, 11 May 2007 15:37:49 -0400

>     [IANAv4Multicast] registry.

This part doesn't bother me, simply because Section 9 of RFC 2365 has
been around a long time, and the 239.255.255/24 has been out of bounds
for local scope administrative assignments. This range is for "relative
assignments," and RFC 3171 Section 9.1.1 says:

   Since there are only 256 such offsets, the IANA
   should only assign a relative offset to a protocol that provides an
   infrastructure supporting service.  Examples of such services include
   the Session Announcement Protocol [RFC2974].  Pursuant to section
   4.4.2 of RFC 2780 [RFC2780], assignments of Relative Offsets follow
   an Expert Review, IESG Approval or Standards Action process.  See
   [IANA] for the current set of assignments.

> indicates to me that it should be OK to assign a Manet address up in  

Going by the spirit of RFC 2365, I've started assigning multicast
addresses from 239.255.254.255 and work downward, so in principle if
Microsoft for some inexplicable reason took 239.255.2.2, that won't
bother me for a very long time, but that doesn't make it right. Is there
a reason why they couldn't use something up in the 239.255.255/24 range?
I would have thought that's where it belongs.

If 239.255/16 (minus 239.255.255/24) are supposed to be safe to use
without having to consult the IANA, why can't they remain safe?

Bert

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From: "Manfredi, Albert E" <[email-masked]>
Date: Fri, 11 May 2007 15:37:49 -0400

Bert

---

From: Dave Thaler <[email-masked]>
Date: Fri, 11 May 2007 13:11:56 -0700

Actually there is a point there I think.  I checked the draft again, and
I don't think it contains sufficient information about what the purpose
of the site-local multicast address is.  So the draft isn't sufficient
to answer
questions 7-11.  So it's interesting, but it isn't sufficient for say an
expert review.

-dave

> -----Original Message-----
> From: Brian Haberman [mailto:[email-masked]]
> Sent: Friday, May 11, 2007 6:54 AM
> To: Marshall Eubanks
> Cc: [email-masked]
> Subject: Re: [MBONED] Site local addresses for MANET
> 
> Hi Marshall,
defined by
rasadv
> > by Dave Thaler,
interested

---

From: Dave Thaler <[email-masked]>
Date: Fri, 11 May 2007 13:11:56 -0700

-dave

defined by
rasadv
interested

---

From: Dave Thaler <[email-masked]>
Date: Fri, 11 May 2007 13:19:54 -0700

By questions 7-11 I'm referring to
http://www.iana.org/cgi-bin/multicast.pl

-Dave

> From: Dave Thaler [mailto:[email-masked]]
> Sent: Friday, May 11, 2007 1:12 PM
> To: Brian Haberman; Marshall Eubanks
> Cc: [email-masked]
> Subject: RE: [MBONED] Site local addresses for MANET
> 
> > be used.  I have seen some hand-waving around auto-configuration,
but
> no

---

From: Dave Thaler <[email-masked]>
Date: Fri, 11 May 2007 13:19:54 -0700

-Dave

but

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From: Tim Chown <[email-masked]>
Date: Mon, 14 May 2007 16:23:19 +0100

>      Reminds me of the paranoia to reserve addresses "just in case".

Why would they want a site local reservation for v6?   In v6 the scoping
is explicit in the address format, so they can generate what they like
from any valid unicast prefix available (by my understanding of 3306 that 
could be a ULA prefix, or subnet thereof, if they really wanted to do that), 
and limit propogation by scope value. 

Is the requirement to have some well-known groups for some functions?

One could envisage that being used on some adhoc set of networks with one
or more uplinks limiting the scope.

-- 
Tim

---

From: Tim Chown <[email-masked]>
Date: Mon, 14 May 2007 16:23:19 +0100

-- 
Tim