Re: [6lowpan] WG last call on Routing Requirements draft

[josep paradells <[e-mail]>]

Hi 6LoWPANners,

First of all, I would like to express my support to moving forward the 
document. It offers very useful information for people working on the 
use of IP on top of LoWPANs.

Regarding the objections expressed by JP Vasseur on the list, I would 
like to remark the following:

>In this document, several characteristics of the issues and challenges 
of routing in
>constrained and loosy environments are listed, nothing new to what is 
done in the
>ROLL Working Group.

IMHO, this is not true. ROLL has focused on application requirements, 
while 6LoWPAN has focused on 802.15.4-based requirements. There is, of 
course, some overlap between both, but I think this is not a problem. 
Instead, these two approaches complement each other gracefully.

On the other hand, note that the first 6LoWPAN routing requirements 
draft was submitted almost a year before the ROLL (then called RL2N) BoF 
took place.

>You mention that IP routing and what is referred to as Mesh-
>Under Routing can be
>used in such environment. So what is the aim of this document ?

The aim of the document is clearly stated in the abstract of the document:

“6LoWPANs are formed by devices that are compatible with the IEEE 
802.15.4 standard. However, neither the IEEE 802.15.4 standard nor the 
6LoWPAN format specification define how mesh topologies could be 
obtained and maintained. Thus, it should be considered how 6LoWPAN 
formation and multi-hop routing could be supported. This document 
provides the problem statement and design space for 6LoWPAN routing. It 
defines the routing requirements for 6LoWPAN networks, considering the 
low-power and other particular characteristics of the devices and links. 
The purpose of this document is not to recommend specific solutions, but 
to provide general, layer-agnostic guidelines about the design of 
6LoWPAN routing, which can lead to further analysis and protocol design. 
This document is intended as input to groups working on routing 
protocols relevant to 6LoWPAN, such as the IETF ROLL WG.”


>  1) Is it to provide routing requirement for L3 (route over) ?
>  2) Is it to provide routing requirement for L2 (mesh under) ?

>  If 1), then you may want to see with the ROLL WG whether some of the 
data could
>be used for this WG that is not already covered by the existing routing 
requirements
>documents.
>  If 2), what is the intent of the document since we do not rightly (at 
the IETF) intend to specify a L2 "routing"
>protocol for a specific media such as 802.15.4.

I think this reasoning is not valid and Carsten Bormann gave already a 
good explanation for this in the e-mail
he sent to the list in August 7, as a reply to the e-mail you sent the 
same day.

Furthermore, personally, I believe that this separation between L2 and 
L3 functionality is not that clear.
For example, it is possible to find routes using IP addresses and 
performing packet/frame forwarding using L2 addresses.

>  Figure 1 shows the place of 6LoWPAN routing in the entire network
>  stack.

>  +-----------------------------+ +-----------------------------+
>  | Application Layer | | Application Layer |
>  +-----------------------------+ +-----------------------------+
>  | Transport Layer (TCP/UDP) | | Transport Layer (TCP/UDP) |
>  +-----------------------------+ +-----------------------------+
>  | Network Layer (IPv6) | | Network +---------+ |
>  +-----------------------------+ | Layer | Routing | |
>  | 6LoWPAN +---------+ | | (IPv6) +---------+ |
>  | Adaptation | Routing*| | +-----------------------------+
>  | Layer +---------+ | | 6LoWPAN Adaptation Layer |
>  +-----------------------------+ +-----------------------------+
>  | IEEE 802.15.4 (MAC) | | IEEE 802.15.4 (MAC) |
>  +-----------------------------+ +-----------------------------+
>  | IEEE 802.15.4 (PHY) | | IEEE 802.15.4 (PHY) |
>  +-----------------------------+ +-----------------------------+

>  * Here, 'Routing' is not equivalent to IP routing,
>  but includes the functionalities of path computation and
>  forwarding under the IP layer.

>  Figure 1: Mesh Under (left) and Route Over routing (right)

>The right part is what we do at the IETF, in ROLL.
>The left part looks like a new "architecture" to me, an adaptation layer 
performing
>routing. I guess that you in fact mean routing at the MAC layer, in 
which case, you
>may want to discuss it with IEEE.

The same as before applies to this comment (please refer to Carsten’s 
e-mail of August 7). In addition, the figure just illustrates what is 
defined in RFC 4944, which is the base document describing how to 
transmit IPv6 packets on top of IEEE 802.15.4 networks.

As a final remark, from your e-mail, it seems like you are questioning 
the existence of the document. Let me remind you that the 6LoWPAN WG 
agreed some time ago on the current charter, which has the following item:

“4. As a separate Internet Draft, "6LoWPAN Routing Requirements" will 
describe 6LoWPAN-specific requirements on routing protocols used in 
6LoWPANs, addressing both the "route-over" and "mesh-under" approach. 
This document will be created and owned by this working group but is 
expected to be reviewed by the ROLL WG. This document will be 
informational.”


And another important point is that the WG reached consensus on adopting 
the document as a WG document almost a year ago in the IETF meeting in 
Minneapolis in November 2008. According to the minutes, you were there.

Regards,

Josep Paradells



En/na Geoff Mulligan ha escrit:
> Folks,
>   This note formally starts the WG Last Call for comments on
> draft-ietf-6lowpan-routing-requirements-04.txt, "Problem Statement and
> Requirements for 6LoWPAN Routing".
>
> The document can be found at:
> http://www.ietf.org/id/draft-ietf-6lowpan-routing-requirements-04.txt
>
> The document is intended to be submitted by this Working Group to the
> IESG for publication as an Informational Document.
>
> Please review the document carefully (one last time), and send your
> comments to the 6lowpan list.  Please also indicate in your response
> whether or not you think this document is ready to go to the IESG.
>
> This Last Call will end on Thursday 1 October 2009 at 2359 UTC.
>
>         Thanks,
>                 Geoff & Carsten
>
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