Subject: [Roll] Last Call: <draft-ietf-roll-trickle-mcast-05.txt> (Multicast Protocol for Low power and Lossy Networks (MPL)) to Proposed Standard

From: The IESG <[email-masked]>
Date: Thu, 10 Oct 2013 15:17:13 -0700

The IESG has received a request from the Routing Over Low power and Lossy
networks WG (roll) to consider the following document:
- 'Multicast Protocol for Low power and Lossy Networks (MPL)'
  <draft-ietf-roll-trickle-mcast-05.txt> as Proposed Standard

The IESG plans to make a decision in the next few weeks, and solicits
final comments on this action. Please send substantive comments to the
[email-masked] mailing lists by 2013-10-24. Exceptionally, comments may be
sent to [email-masked] instead. In either case, please retain the
beginning of the Subject line to allow automated sorting.

Abstract

   This document specifies the Multicast Protocol for Low power and
   Lossy Networks (MPL) that provides IPv6 multicast forwarding in
   constrained networks.  MPL avoids the need to construct or maintain
   any multicast forwarding topology, disseminating messages to all MPL
   Forwarders in an MPL Domain.  MPL uses the Trickle algorithm to
   manage message transmissions for both control and data-plane
   messages.  Different Trickle parameter configurations allow MPL to
   trade between dissemination latency and transmission efficiency.

The file can be obtained via
http://datatracker.ietf.org/doc/draft-ietf-roll-trickle-mcast/

IESG discussion can be tracked via
http://datatracker.ietf.org/doc/draft-ietf-roll-trickle-mcast/ballot/

The following IPR Declarations may be related to this I-D:

   http://datatracker.ietf.org/ipr/1858/

---

From: Ralph Droms <[email-masked]>
Date: Fri, 11 Oct 2013 13:09:27 -0400

draft-ietf-roll-trickle-mcast-05 and draft-ietf-6man-multicast-scopes-00 are in conflict with each other.

From draft-ietf-roll-trickle-mcast-05:

   When
   used with MPL, Realm-Local scope is administratively defined and used
   to define the boundaries of multicast message dissemination by MPL.

From draft-ietf-6man-multicast-scopes-00:

   Realm-Local scope is the largest scope that is automatically
   configured, i.e., automatically derived from physical
   connectivity or other, non-multicast-related configuration.

Specifically, "administratively defined" seems to me to be in direct
conflict with "automatically configured". 

I suggest fixing the problem with two updates.  First, the definition
of "scop 3" in an IP-over-IEEE802.15.4 needs to be published, based on
this text from draft-ietf-6man-multicast-scopes-00: 

   The definition of any Realm-Local scope for a particular network
   technology should be published in an RFC.

I suggest:

   When used in an IP-over-IEEE802.15.4 network, "scop 3" is defined
   to include all interfaces sharing a PAN ID.

This text could be added to draft-ietf-roll-trickle-mcast-05, or to
draft-ietf-6man-multicast-scopes-00 or published separately in yet
another "world's shortest RFC".

Second, draft-ietf-roll-trickle-mcast-05 should be changed to read:

   When used with MPL, Realm-local scope is defined according to the
   underlying network technology; for example, [cite the
   IP-over-IEEE802.15.4 definition].

As a further refinement, I suggest text be added to
draft-ietf-roll-trickle-mcast-05 to the effect of:

   "scop 4" can also be used with MPL to cover deployments that use
   administratively defined scopes that cover, for example, subnets
   based on different underlying network technologies.

- Ralph

PS I originally posted about this issue to the rool WG mailing list:
http://www.ietf.org/mail-archive/web/roll/current/msg08188.html.
After a discussion with Kerry Lynn, I made a change to the definition
of scop 3 for IEEE802.15.4.

---

From: Robert Cragie <[email-masked]>
Date: Mon, 14 Oct 2013 15:06:25 +0100

I would propose adding the language to draft-ietf-roll-trickle-mcast. 
There doesn't seem much point to doing another "world's shortest RFC".

Here's an attempt at combining Ralph's text with the terminology in the 
draft:

=================
OLD
By default, an MPL Forwarder SHOULD participate in an MPL Domain 
identified by the ALL_MPL_FORWARDERS multicast address with a scope 
value of 3 (Realm-Local) [I-D.droms-6man-multicast-scopes].  When used 
with MPL, Realm-Local scope is administratively defined and used to 
define the boundaries of multicast message dissemination by MPL.

NEW
By default, an MPL Forwarder SHOULD participate in an MPL Domain where 
the MPL Domain Address is the ALL_MPL_FORWARDERS multicast address with 
a scope value of 3 (Realm-Local) [I-D.droms-6man-multicast-scopes].  
When used with MPL, Realm-Local scope is defined according to the 
underlying network technology; for example, when used in an 
IP-over-IEEE802.15.4 network, Realm-Local scope is defined to include 
the set of MPL Interfaces sharing a PAN ID.

An MPL Forwarder MAY participate in an MPL Domain where the MPL Domain 
Address uses a scope value of 4 (Admin-Local) 
[I-D.droms-6man-multicast-scopes]. When used with MPL, Admin-Local scope 
can be used in deployments that use administratively defined scopes that 
cover, for example, subnets based on different underlying network 
technologies.
=================

Robert
On 11/10/2013 18:09, Ralph Droms wrote:
> _______________________________________________
> Roll mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/roll
>

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From: "Ralph Droms (rdroms)" <[email-masked]>
Date: Fri, 25 Oct 2013 19:56:42 +0000

There was a long discussion about this issue on the [email-masked] mailing list:

  When

I think I've read consensus in the various discussion threads to make the following change to draft-ietf-roll-trickle-mcast-05:

OLD:

   When

NEW:

   When
   used with MPL, Realm-Local scope is defined according to the
   underlying network technology; for example, [cite the
   IP-over-IEEE802.15.4 definition].

where "the IP-over-IEEE802.15.4 definition" is text to be published elsewhere (perhaps draft-ietf-6man-multicast-scopes) that defines scop 3 for IEEE802.15.4 mesh networks.

I read less strong consensus (less discussion) of the following proposed changes:

NEW (to be added immediately following text describing the use of Realm-Local scope):

  Admin-Local scope (scop value 4) can also be used with MPL
  in deployments that use administratively defined scopes that
  cover, for example, multiple subnets based on different
  underlying network technologies.

As a side note, there is a related discussion about draft-ietf-6man-multicast-scopes on the [email-masked] mailing list.  The term "Realm-Local scope" may change (should be changed for consistency with) the final published version of draft-ietf-6man-multicast-scopes.

- Ralph