Re: [ipwave] draft-ietf-ipwave-ipv6-over-80211ocb-39

[Brian E Carpenter <[e-mail]>]

Excuse top posting. 

As I've said, I am no expert, but I do know some physics, and
it seems pretty clear to me that if there are multiple lanes 
of traffic, a large truck can easily shield signals between
two cars and the shielding will be intermittent, regardless
of how much wireless power is allowed, depending on traffic
movement. So it's a highly dynamic mesh network. That's a very
interesting problem that has been much studied, and it's
fundamentally different from the ND design scenario.

So I find it hard to believe that nobody can write the TBD
text.

Regards
   Brian

On 15-Apr-19 23:26, Alexandre Petrescu wrote:
> Hi Brian,
> 
> Le 14/04/2019 à 22:49, Brian E Carpenter a écrit :
>> Hi Alexandre,
>>
>> On 15-Apr-19 04:38, Alexandre Petrescu wrote:
>>> 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.
>>
>> That's exactly the text that I find problematic. I can't write a new
>> version because I lack your expert knowledge, but IMHO it should be
>> more specific:
>>
>>      The baseline Neighbor Discovery protocol (ND) [RFC4861] MUST be used
>>      over 802.11-OCB links.  However, as on any wireless link, transmission
>>      of multicast ND packets may fail in OCB. In particular, scenarios
>>      where TBD TBD TBD are likely to be unreliable and SHOULD NOT be
>>      deployed until an alternative standardised solution is available.
>>      The best of current knowledge indicates the kinds of issues that
>>      may arise with ND in OCB mode; they are described in Appendix J.
> 
> I can agree with that formulation and put it in the text.
> 
> But I need an indicat that TBD is defined soon.  The time commitments of 
> Pascal seem to be saying he is no longer interested in writing that TBD.
> 
> I wait a little for this to clarify.
> 
>> Also I don't like this phrasing in Appendix J:
>>
>>     Early experiences indicate that it should be possible to exchange
>>     IPv6 packets over OCB while relying on IPv6 ND alone for DAD and AR
>>     (Address Resolution).
>>
>> Could you rather say the opposite:
>>
>>     Early experience indicates that it is possible to exchange
>>     IPv6 packets over OCB while relying on IPv6 ND alone for DAD and AR
>>     (Address Resolution) in good conditions. However, this does not
>>     apply if TBD TBD TBD...
> 
> This is an appendix.  I could put TBD there now.
> 
> Alex
> 
>>
>> Regards
>>      Brian
>>
>>
>>>
>>>
>>> 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
>>>>>
>>>>
>>>>
>>> .
>>>
>>
>>
>