Hello Pascal,
You describe below a problem with DAD, and a potential solution with
RFC8505.
We have two drafts here in IPWAVE WG: IP-over-OCB, and IPWAVE Problem
Statement.
Do you disagree if we move the appendix titled "ND issues in wireless
links" away from IP-over-OCB, and into the Problem Statement draft?
Maybe that draft would be a better fit for ND an DAD problems and
suggested solutions.
Alex
Le 15/04/2019 à 10:04, Pascal Thubert (pthubert) a écrit :
Hello Alexandre.
I hoped I was clear before.
Take 4 cars, A, B, C, D separated by 100 meters each, such that all can hear C, though A has a bad quality, and A and D are too far apart. C advertises a prefix in RA(PIO), all can hear it.
- Try pinging A from D using the address based on that prefix, won't ping.
- Try configuring A's address on D it will be accepted, which means that DAD will not work either.
This is nothing new, common to all the short/middle range radios we have looked at. You may try the same placing C at the corner of a street, A and D in orthogonal streets.
This has nothing to do with low power and everything to do with radio propagation.
The exception is Wi-Fi, and that's because the BSS emulates the broadcast domain, as I think I explained already.
RFC 8505 recreates the Wi-Fi design but at L3... and the use cases above were made to work on other radios with similar properties. More in the 6TiSCH architecture I guess...
Sorry you consumed all the time I could dedicate, and more.
All the best,
Pascal
-----Original Message-----
From: Alexandre Petrescu <alexandre.petrescu@xxxxxxxxx>
Sent: lundi 15 avril 2019 15:35
To: Pascal Thubert (pthubert) <pthubert@xxxxxxxxx>
Cc: Brian E Carpenter <brian.e.carpenter@xxxxxxxxx>; NABIL BENAMAR
<n.benamar@xxxxxxxxxxxxx>; Sri Gundavelli (sgundave)
<sgundave@xxxxxxxxx>; nabil benamar <benamar73@xxxxxxxxx>;
ietf@xxxxxxxx; its@xxxxxxxx; int-dir@xxxxxxxx; draft-ietf-ipwave-ipv6-over-
80211ocb.all@xxxxxxxx
Subject: Re: draft-ietf-ipwave-ipv6-over-80211ocb-38
Pascal - do you know of a OCB use and some scenario where ND does not
work?
(I mean some trials that you may have done with OCB; if you never played with
OCB and wiht IP on it, I think it makes no sense to describe speculations of it).
Alex
Le 15/04/2019 à 08:53, Pascal Thubert (pthubert) a écrit :
This text is wrong, Alexandre.
There is a distinction between performance issue and does not work. You
can not MUST a protocol that by design will only work in a subset of the
possible situations.
What you can do is document in which situations it can be made to work
(P2P and full overlap of the broadcast domains) and explain the drawbacks (eg
if broadcast is sent at higher power or slower phy then it impacts unicast
communications).
Then you want to open the door to using more suitable techniques in future
documents, which the MUST seems to discourage.
Regards,
Pascal
Le 14 avr. 2019 à 18:38, Alexandre Petrescu
<alexandre.petrescu@xxxxxxxxx> a écrit :
Brian,
Le 14/04/2019 à 04:20, Brian E Carpenter a écrit :
All we need is a simple statement in the spec which puts some
scope limits, w.r.t the missing ND pieces and issues.
Yes, that is clearly essential, as well as an associated health
warning that implementers must not rush ahead because of the risk of
non-interoperability.
There is already paragraph, and an Appendix, about potential ND issues. I
think that text qualifies as an associated health warning.
I do not know what do you mean about the risk of interoperability. This ND
that works is interoperable between several OCB cards, IP Road Side Units, and
linuces. (I can cite brands that I al familiar with and that interoperate.
This is the current paragraph and Appendix that qualify as a warning that
you suggest:
The baseline Neighbor Discovery protocol (ND) [RFC4861] MUST be used
over 802.11-OCB links. Transmitting ND packets may prove to have
some performance issues. These issues may be exacerbated in OCB
mode. Solutions for these problems SHOULD consider the OCB mode of
operation. The best of current knowledge indicates the kinds of
issues that may arise with ND in OCB mode; they are described in
Appendix J.
Alex
Regards
Brian
On 14-Apr-19 13:58, NABIL BENAMAR wrote:
+1 Sri
On Sun, Apr 14, 2019, 00:06 Sri Gundavelli (sgundave)
<sgundave@xxxxxxxxx <mailto:sgundave@xxxxxxxxx>> wrote:
I understand your point Brian, but IMO there are enough reasons not
to
delay this work.
There are many use-cases/applications where there is a stable
topology of
RSU¹s and OBU¹s. The regulations around 5.9 Ghz (DSRC) band allows
the
channel use for non-priority/non-traffic safety related applications.
For
example, a vehicle in a gas station can receive a coupon from the
802.11-OCB radio (AP/RSU) in the gas station. There, its a stable
topology
that classic ND is designed for. In this operating mode, its perfectly
reasonable to use classic ND and it works. The authors have shown
enough
lab data on the same.
Ideally, I agree with you that it makes lot more sense to publish both
the
specs at the same time. But, for what ever reasons the WG went on
this
path. Authors have spent incredible amount of efforts in getting the
draft
this far and we cannot ignore that. You can see the efforts from the
version number; when did we last see a draft version -037?
We also need to distill the recent ND discussions and filter out the
threads that are clearly motivated to insert a ND protocol that is
designed for a totally different operating environment. An argument
that a
protocol designed for low-power environments is the solution for
vehicular
environments requires some serious vetting. Looking at the
characteristics, always-sleeping, occasional internet connectivity,
low-power, no memory, no processing power, no mobility ..etc,
meeting
vehicular requirements is some thing most people in the WG do not
get it.
Bottom line, IMO, we should move this forward and publish the
document.
All we need is a simple statement in the spec which puts some scope
limits, w.r.t the missing ND pieces and issues. There are other
proposals
in the WG that will address the gaps and bring closure to the work.
Sri
On 4/12/19, 1:28 PM, "Brian E Carpenter"
<brian.e.carpenter@xxxxxxxxx <mailto:brian.e.carpenter@xxxxxxxxx>>
wrote:
>On 13-Apr-19 02:59, Sri Gundavelli (sgundave) wrote:
>>If you go back and check 2017 archives, I did raise many of these
>>issues. But, we clearly decided to limit the scope excluding address
>>configuration, DAD, ND aspect, link models. When there is such a
scope
>>statement, it should clearly move these comments to the draft that
>>defines how ND works for 802.11-OCB links.
>
>This is of course possible. In general the IETF hasn't done that, but
has
>followed the lead set by RFC 2464 with the complete specification of
>IPv6-over-foo in one document.
>
>However, I don't believe that publishing an RFC about the frame
format
>without *simultaneously* publishing an RFC about ND etc would be a
good
>idea. That would leave developers absolutely unable to write useful
>code, and might easily lead to incompatible implementations. Since
>we'd presumably like Fords to be able to communicate with
Peugeots,
>that seems like a bad idea.
>
>Regards
> Brian
