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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