Re: [ipwave] draft-ietf-ipwave-ipv6-over-80211ocb-38

[Alexandre Petrescu <[e-mail]>]

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,

DO you know that in OCB the allowed power levels are much higher than in 
WiFi?  This has impact on your assumption that at 100m spacing between 
pairs of cars is still ok with 4 cars: they all hear each other ok.

In OCB one can go as far as 800m between two cars in open outdoors, 
safely.  We did.

In some countries one can go even further.  I would love to try this in 
America where power levels can go up to 40dbm (i.e. maybe 2km).

So, if you try to make 4 cars in America to follow your pencil and paper 
test you need maybe 8km distance.  You need a few drivers to work for 
you and as many programmers.  You also need walkie-talkies.  Can you get 
that?

Alex

  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
>> <[e-mail]> Sent: lundi 15 avril 2019 15:35 To:
>> Pascal Thubert (pthubert) <[e-mail]> Cc: Brian E
>> Carpenter <[e-mail]>; NABIL BENAMAR 
>> <[e-mail]>; Sri Gundavelli (sgundave) 
>> <[e-mail]>; nabil benamar <[e-mail]>; 
>> [e-mail]; [e-mail]; [e-mail];
>> draft-ietf-ipwave-ipv6-over- [e-mail] 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
>> <[e-mail]> 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)
>> <[e-mail] <mailto:[e-mail]>> 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"
>> <[e-mail] <mailto:[e-mail]>>
>>>>>> 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
>>>>>>