Re: [ipwave] Intdir last call review of draft-ietf-ipwave-vehicular-networking-20

Alexandre Petrescu <> Thu, 09 September 2021 08:20 UTC

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From: Alexandre Petrescu <>
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Subject: Re: [ipwave] Intdir last call review of draft-ietf-ipwave-vehicular-networking-20
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I am not disagreeing with the changes of the draft that PAscal proposed 
and authors integrated.

Howeve, I need to make a few remarks, just for clarification.

Le 02/09/2021 à 08:49, Pascal Thubert (pthubert) a écrit :
> “
> RPL is primarily designed to minimize the control plane activity, that 
> is the relative amount of routing protocol exchanges vs. data traffic;

We must not forget that RPL was designed in the RoLL WG; RoLL means 
Routing over Low Power and Lossy Links.  RPL was pushed forward very 
much by an application domain which relates to the electricity counters 
at home.  We should remember that, because we discussed it extensively 
at the time.  There was much frustration.  After all that discussion, 
now we come back to say that actually, no, it was not so?

In that sense, it is strange to say that RPL is 'primarily' designed for 
a goal (minimize control plane activity) which differs from the goals of 
the RoLL WG.

This situation is very much like when we have a tool (RPL) and try to 
use it for many different purposes whose scopes are different.

Cars are not low-power.  Cars have very high energy available and very 
many horses as power (horse-power).

Cars do not use lossy links any more than regular WiFi is a lossy link.

Certainly, when experimenting with car networks many packets get lost, 
and many errors show up.  But there are so many other causes for that to 
happen, than what a protocol can deal with: the things that happen have 
to do in many cases with human factors like the working conditions 
(programmers are not sitted comfortably at a desk, but are uncomfortably 
sit in cars with small screens small keyboards); then there are so many 
intermediary layers of protocols which might fail, and also the 
reporting which often fails.  These things generate a majority of events 
that one might take for a 'lossy network'.

> this approach is beneficial for situations where the power and 
> bandwidth are scarce (e.g., an IoT LLN where RPL is typically used 
> today), but also in situations of high relative mobility between the 
> nodes in the network (aka swarming, e.g., within a variable set of 
> vehicles with a similar global motion, or a toon of drones).

Car networks do not need arbitrary mobility.  Their mobility patterns 
are very restricted.  It is not brownian movements.

For example, cars move on ways along pre-determined paths.  There might 
be convoys, and sliding lanes of cars, there might be intersections 
controlled by traffic lights; human reaction (in the order of 1 or 2 
seconds, or more) is what makes for dynamicity in car networks; that 
time (seconds delay) is very very high compared to the latency of modern 
wireless media (e.g. 802.11bd with below milli-second latencies).  
Generally speaking it is  a very orderly movement.

Yes, we are impressed with the speed of cars, and imagine that for these 
speeds the communication protocols might not cope with.  But one has to 
consider _relative_ speeds (e.g. a car following another one is 
practically stationary with respect to it), and one has to consider the 
speed of the communication  medium which is the speed of light.

Think that even a launch of a rocket carrying tons of payload at 30.000 
km/h vertically still sends live video we can enjoy seeing over the 
Internet today.  There is no need of new protocol for that kind of 
mobility, and still the dynamicity aspect (speed) is very very extreme; 
it is probably the highest speeds one can achieve  on Earth.

Trying to make 'universal' protocols that work well in a a wide range of 
mobility and dynamicity is a too high objective.  One can try, yes, but 
does it succeed in deployment?


> To reduce the routing exchanges, RPL leverages a Distance Vector 
> approach, which does not need a global knowledge of the topology, and 
> only optimizes the routes to and from the root, allowing P2P paths to 
> be stretched. Although RPL installs its routes proactively, it only 
> maintains them lazily, in reaction to actual traffic, or as a slow 
> background activity. Additionally, RPL leverages the concept of an 
> objective function, which allows to adapt the activity of the routing 
> protocol to the use case, e.g., type, speed, and quality of the 
> radios. RPL does not need converge, and provides connectivity to most 
> nodes most of the time. The default route towards the Root is 
> maintained aggressively and may change while a packet progresses 
> without causing loops, so the packet will still reach the root. In 
> non-storing mode, a node inside the mesh/swarm that changes its 
> point(s) of attachment to the graph informs the root with a single 
> unicast packet the flows along the default route, and the connectivity 
> is restored immediately; this mode is preferable for use cases where 
> internet connectivity is dominant. OTOH, in storing mode, the routing 
> stretch is reduced, for a better P2P connectivity, while the internet 
> connectivity is restored more slowly, time for the DV operation to 
> operate hop-by-hop. While a RPL topology can quickly scale up and down 
> and fits the needs of mobility of vehicles, the total performance of 
> the system will also depend on how quickly a node can form an address, 
> join the mesh (including AAA), and manage its global mobility to 
> become reachable from outside the mesh.
> “
> Otherwise, all good!
> Take care,
> Pascal
> *From:* Mr. Jaehoon Paul Jeong <>
> *Sent:* lundi 30 août 2021 15:12
> *To:* Pascal Thubert (pthubert) <>
> *Cc:*; Last Call <>rg>; 
> <>es>; skku-iotlab-members 
> <>om>; Chris Shen 
> <>om>; Mr. Jaehoon Paul Jeong <>
> *Subject:* Re: [ipwave] Intdir last call review of 
> draft-ietf-ipwave-vehicular-networking-20
> Hi Pascal,
> Here is the revision (-21) of IPWAVE PS Draft:
> <>
> I attach the revision letter to show how I have addressed your 
> comments on the revision.
> Chris and I have worked for this revision together.
> If you have further comments, please let me know.
> Thanks.
> Best Regards,
> Paul
> On Fri, Jun 18, 2021 at 4:42 PM Pascal Thubert via Datatracker 
> < <>> wrote:
>     Reviewer: Pascal Thubert
>     Review result: Not Ready
>     Dear authors
>     In summary:
>     I read a number of very good drafts collated in one, from the use
>     cases that
>     very complete and ready to publish, to the architecture and
>     protocol solution
>     in section 4 that would require more work for completeness.
>     There are multiple instances in the use cases where protocols are
>     listed coming
>     out of the blue, e.g., the references to OMNI that seem
>     artificially spread
>     regardless of the context of the section. OMNI is used throughout,
>     both as an
>     open ended toolbox, and as a carpet under which all problems can
>     be hidden.
>     Reading this doc, OMNI shows as an interface to a software mobile
>     router, with
>     multiple of the device physical interfaces connected to the mobile
>     router. This
>     makes the stack very simple as the complexity moves to the router.
>     But now you
>     have to implement the router. Presented as that, the OMNI router
>     deserves its
>     name, it’s indeed very rich; it seems to cover all forms of MANET
>     (many to
>     choose from) and NEMO (and all the MIP protocol family across address
>     families), all the possible radio interfaces on which the ND
>     problems go away
>     by magic, and whatever else you want to put in there. Is that the
>     intention?
>     Instead of referring to OMNI for virtually anything, the doc
>     should refer to
>     MANET for MANET things (like BYOD), NEMO for NEMO things (like MNP),
>     draft-nordmark-intarea-ippl for split subnets, and
>     draft-thubert-6man-ipv6-over-wireless for P2MP/NBMA link and
>     subnet models. And
>     then you can say that all those components can be plugged in the
>     OMNI router,
>     and you can discuss which MANET and which MIP you want, including
>     using OMNI’s
>     built in mobility.
>     Note that my objections are not against the OMNI design, it might
>     be the
>     perfect thing and I am already aware of use cases that could be
>     served by a
>     P2MP interface like OMNI in conjunction with RFC8505 on the P2P
>     subinterfaces
>     (recycling the high level design we’ve been shipping for IPv4 /
>     frame relay for
>     the last 30 years). My objection is of the way the draft uses
>     [OMNI] as the
>     magic wand that solves all the problems when what you really do is
>     throw them
>     over the fence. I’d rather you focus on problems and use cases,
>     for which
>     there’s excellent text, and indicate what needs to be done without
>     making
>     assumption on how the needful things will be solved.
>     In agreement with a discussion on the 6MAN list, I’d suggest to
>     split, keep all
>     that’s use case and problem description and ship it, remove
>     references to
>     protocols envisioned in the solution, and start the work on
>     architecture of the
>     solution and the protocol applicability statements separately. An
>     alternate
>     would be to centralize the discussion on protocols to annex, and
>     explain that
>     protocol A or B could be envisioned in solution space because to
>     over this gap
>     or implement that function.
>     In any fashion, the current text is not ready for publication as
>     applicability
>     statement, architecture and or/solution, so the related work
>     should be removed
>     from the main text. But I find it mostly ready for use case and
>     problem
>     statement, more below.
>     Review:
>     Abstract
>        This document discusses the problem statement and use cases of
>        IPv6-based vehicular networking for Intelligent Transportation
>        Systems (ITS).
>     >>> The document goes beyond that; there was actually a thread at
>     6MAN where
>     Bob Hinden said “ This document says it is a problem statement,
>     but then
>     becomes a solution document.   Might be better to cut it down to
>     only the
>     problem statement part. “ >>> Would you consider doing this? If
>     not, why? Note:
>     you may want to respond on 6MAN as well. >>> >>>I would have
>     thought that the
>     traditional steps of problem statement and applicability statement
>     of existing
>     work could be expected from IPWAVE too. >>> Please clarify the
>     steps that you
>     intend to follow next with this work.
>     <snip>
>     1.  Introduction
>     >>> Very readable and informative section, many thanks!
>        Along with these WAVE standards and C-V2X standards, regardless
>     of a
>        wireless access technology under the IP stack of a vehicle,
>     vehicular
>        networks can operate IP mobility with IPv6 [RFC8200] and Mobile
>     IPv6
>        protocols (e.g., Mobile IPv6 (MIPv6) [RFC6275], Proxy MIPv6
>     (PMIPv6)
>        [RFC5213], Distributed Mobility Management (DMM) [RFC7333],
>     Locator/
>        ID Separation Protocol (LISP) [RFC6830BIS], and Asymmetric Extended
>        Route Optimization (AERO) [RFC6706BIS]).
>     >>> NEMO (RFC 3963) is not cited. Any reason why the vehicle would not
>     transport a network?
>     <snip>
>        This document describes use cases and a problem statement about
>        IPv6-based vehicular networking for ITS, which is named IPv6
>     Wireless
>        Access in Vehicular Environments (IPWAVE). First, it introduces the
>        use cases for using V2V, V2I, and V2X networking in ITS.  Next, for
>        IPv6-based vehicular networks, it makes a gap analysis of current
>        IPv6 protocols (e.g., IPv6 Neighbor Discovery, Mobility Management,
>        and Security & Privacy), and then enumerates requirements for the
>        extensions of those IPv6 protocols, which are tailored to
>     IPv6-based
>        vehicular networking.  Thus, this document is intended to motivate
>        development of key protocols for IPWAVE.
>     >>>
>     <snip>
>     2.  Terminology
>     >>>
>     <snip>
>        o  IP-OBU: "Internet Protocol On-Board Unit": An IP-OBU denotes a
>           computer situated in a vehicle (e.g., car, bicycle, autobike,
>           motor cycle, and a similar one) and a device (e.g.,
>     smartphone and
>           IoT device).  It has at least one IP interface that runs in IEEE
>           802.11-OCB and has an "OBU" transceiver. Also, it may have an IP
>           interface that runs in Cellular V2X (C-V2X) [TS-23.285-3GPP]
>           [TR-22.886-3GPP][TS-23.287-3GPP].  See the definition of the
>     term
>           "OBU" in [RFC8691].
>     >>> Can that be a router connecting multiple computers?
>     <snip>
>     3.  Use Cases
>     >>> This is another great read and an enlightening section. Maybe
>     mention in
>     the abstract that the doc also covers use cases?
>     <snip>
>        Although a Layer-2 solution can provide a support for multihop
>        communications in vehicular networks, the scalability issue related
>        to multihop forwarding still remains when vehicles need to
>        disseminate or forward packets toward multihop-away
>     destinations.  In
>        addition, the IPv6-based approach for V2V as a network layer
>     protocol
>        can accommodate multiple radio technologies as MAC protocols,
>     such as
>        5G V2X and DSRC.  Therefore, the existing IPv6 protocol can be
>        augmented through the addition of an Overlay Multilink Network
>     (OMNI)
>        Interface [OMNI] and/or protocol changes in order to support both
>        wireless single-hop/multihop V2V communications and multiple radio
>        technologies in vehicular networks.  In such a way, vehicles can
>        communicate with each other by V2V communications to share
>     either an
>        emergency situation or road hazard in a highway having multiple
>     kinds
>        of radio technologies, such as 5G V2X and DSRC.
>     >>> This text appears in the middle of high level use case, with a
>     crude list
>     of protocols; this is not a place for it
>     >>> On a 6MAN Thread, Brian Carpenter said that the above:
>     “
>     is of concern regardless of the mention of OMNI. Does it mean "can
>     be" or
>     "needs to be"? This paragraph seems like a very short summary of a
>     big problem
>     area. At the end of page 13 there is some related discussion,
>     which mentions
>     RPL as part of the solution (good choice, IMHO) but again seems to
>     depend on
>     OMNI. I don't think the fix of simply removing references to OMNI
>     works,
>     because it would leave a gap. In an informational document, that
>     is not a
>     formal problem but as far as this draft describes architecture, I
>     don't think
>     that big a gap is reasonable. "OMNI" is mentioned more than 20
>     times in the
>     document. There are also several references to AERO, which is strongly
>     associated with OMNI. “ >>> I agree with Brian. Here the document
>     seems to be
>     mixing solution with problem and putting the cart before the horse. My
>     recommendation is to stick to what needs to be done that IPv6 does
>     not do yet
>     -the reqs and gaps-; but the doc should not step in the how things
>     will be done
>     unless the group already decided to do it. The logical next steps
>     to a PS are
>     an applicability statement of existing work, and if the gaps
>     cannot be filled,
>     there may be one or more WG chartered to fill those gaps.
>     >>> I’d still be happy to see an annex with leads on where the
>     solution might
>     come from like RFC 8691 does.
>     <snip>
>        The existing IPv6 protocol must be augmented through the
>     addition of
>        an OMNI interface and/or protocol changes in order to support
>        wireless multihop V2I communications in a highway where RSUs are
>        sparsely deployed, so a vehicle can reach the wireless coverage
>     of an
>        RSU through the multihop data forwarding of intermediate vehicles.
>        Thus, IPv6 needs to be extended for multihop V2I communications.
>     >>> Note that I have no clue on how well OMNI applies in that
>     space, maybe it
>     does very well; but here it comes out of the blue with no
>     justification. If you
>     mention OMNI you need to detail what it is and which of the V2V 
>     problems you
>     expect it to solve. But then, that’s beyond the scope of a PS.
>     <snip>
>        The existing IPv6 protocol must be augmented through the
>     addition of
>        an OMNI interface and/or protocol changes in order to support
>        wireless multihop V2X (or V2I2X) communications in an urban road
>        network where RSUs are deployed at intersections, so a vehicle
>     (or a
>        pedestrian's smartphone) can reach the wireless coverage of an RSU
>        through the multihop data forwarding of intermediate vehicles (or
>        pedestrians' smartphones).  Thus, IPv6 needs to be extended for
>        multihop V2X (or V2I2X) communications.
>     >>> Please be more specific on what the missing functions are and
>     whether they
>     are missing from the stack development standpoint or if there’s
>     work needed
>     from the IETF. 1)      If something is really missing in our
>     specs, the text to
>     prove from the use case above is missing 2)      how OMNI serves
>     the use case
>     could be elaborated in an applicability statement of OMNI for
>     V2xyz, but it is
>     a bit blunt to present it as panacea when the problems to be
>     solved are not
>     listed. 3)      If you look at it, OMNI seems like a software
>     mobile router
>     within a bump in the stack. Can that become too big?
>     >>> my view is that the text above and the similar occasions
>     should be replaced
>     by something like :
>        The existing IPv6 protocol must be augmented to provide the
>     following
>        functions: 1) …
>     >>> and / or something like:
>        In addition to the IPv6 node requirements [RFC 8504], the IPv6
>     protocol
>        stack for use in a vehicle must support 1) RFC blah, 2) …
>     <snip>
>        To support applications of these V2X use cases, the functions
>     of IPv6
>        such as VND, VMM, and VSP are prerequisites for IPv6-based packet
>        exchange, transport-layer session continuity, and secure, safe
>        communication between a vehicle and a pedestrian either directly or
>        indirectly via an IP-RSU.
>     >>> “the functions of IPv6 such as VND, VMM, and VSP” does not
>     parse. There’s
>     no IPv6 reference that provides those functions. If the intention
>     is to say
>     that there’s stuff to add to IPv6 to support, like, say,  VND,
>     then this
>     document fails to define how an IPv6 VND should behave, though
>     it’s precisely
>     what I’d expect from a problem statement.
>     <snip>
>     4.  Vehicular Networks
>     >>> What is the purpose of section 4 as a whole, problem statement or
>     applicability statement of the listed protocols? In the former
>     case what’s the
>     problem? In the latter case it is incomplete and needs to be
>     exported to an
>     applicability statement doc with all the possible technologies
>     evaluated.
>        This section describes an example vehicular network architecture
>        supporting V2V, V2I, and V2X communications in vehicular networks.
>     >>> I read this as presenting a context to explain what the
>     problems are
>     instead of presenting the IPVAWE “architecture”. Maybe using the term
>     “Architecture” here is misleading and led to Bob’s comment.
>     <snip>
>     4.1.  Vehicular Network Architecture
>        Figure 1 shows an example vehicular network architecture for
>     V2I and
>        V2V in a road network [OMNI].
>     a.      Is using OMNI a decision that the WG made for the future
>     work ? what
>     does it do and what does it not do? b.      Is there work left to
>     be done? Who
>     will do that work? Or is it the expectation that OMNI has it all
>     defined
>     already?
>     <snip>
>        An existing network architecture (e.g., an IP-based aeronautical
>        network architecture [OMNI][UAM-ITS], a network architecture of
>        PMIPv6 [RFC5213], and a low-power and lossy network architecture
>        [RFC6550]) can be extended to a vehicular network architecture for
>        multihop V2V, V2I, and V2X, as shown in Figure 1.  In a highway
>        scenario, a vehicle may not access an RSU directly because of the
>        distance of the DSRC coverage (up to 1 km).  For example, the OMNI
>        interface and/or RPL (IPv6 Routing Protocol for Low-Power and Lossy
>        Networks) [RFC6550] can be extended to support a multihop V2I
>     since a
>        vehicle can take advantage of other vehicles as relay nodes to
>     reach
>        the RSU.  Also, RPL can be extended to support both multihop
>     V2V and
>        V2X in the similar way.
>     >>> all this could fit well in annex; anyway you need to explain
>     what you
>     expect the protocols to do and which extension is needed. In the
>     case of RPL at
>     least you indicate that it would do routing, but not why you
>     cannot use it of
>     the shelf; for OMNI, what you expect is less clear, though there’s
>     text
>     elsewhere about the many radio interfaces that could be used for
>     the purpose,
>     and the text in the UAM below that is enlightening.
>     <snip>
>                                       To support not only the mobility
>        management of the UAM end systems, but also the multihop and
>        multilink communications of the UAM interfaces, the UAM end systems
>        can employ an Overlay Multilink Network (OMNI) interface [OMNI]
>     as a
>        virtual Non-Broadcast Multiple Access (NBMA) connection to a
>     serving
>        ground domain infrastructure.
>     >>> Again, what is the expectation for OMNI? As an overlay it
>     requires an
>     underlay; when connecting to a MANET it needs support for that
>     MANET. The text
>     above seems to imply that is solves everything in V2xyz like
>     magic; reminds me
>     of the IPv6 multicast abstraction that was supposed to solve the
>     broadcast
>     problem and ended up worsening it.
>     <snip>
>                                 This infrastructure can be configured
>        over the underlying data links.  The OMNI interface and its link
>        model provide a means of multilink, multihop and mobility
>        coordination to the legacy IPv6 ND messaging [RFC4861] according to
>        the NBMA principle.  Thus, the OMNI link model can support
>     efficient
>        UAM internetworking services without additional mobility messaging,
>        and without any modification to the IPv6 ND messaging services or
>        link model.
>     >>> Again, what is the expectation for OMNI? As an overlay it
>     requires an
>     underlay; the text above seems to imply that is solves everything
>     in V2xyz like
>     magic; that would be a stretch, that reminds me of IPv6 multicast
>     that was
>     supposed to solve the broadcast problem and ended up worsening it.
>     <snip>
>        Multiple vehicles under the coverage of an RSU share a prefix
>     just as
>        mobile nodes share a prefix of a Wi-Fi access point in a wireless
>        LAN.  This is a natural characteristic in infrastructure-based
>        wireless networks.  For example, in Figure 1, two vehicles (i.e.,
>        Vehicle2, and Vehicle5) can use Prefix 1 to configure their IPv6
>        global addresses for V2I communication. Alternatively, mobile nodes
>        can employ an OMNI interface and use their own IPv6 Unique Local
>        Addresses (ULAs) [RFC4193] over the wireless network without
>        requiring the messaging of IPv6 Stateless Address Autoconfiguration
>       (SLAAC) [RFC4862], which uses an on-link prefix provided by the
>        (visited) wireless LAN; this technique is known as "Bring-Your-Own-
>        Addresses".
>     >>>  Is OMNI the only way to "Bring-Your-Own-Addresses”? Else the
>     text could be
>     more generic, at least use e.g., like the ref to AERO later. >>>
>     What are the
>     implications / limitations of doing that – like they can do line
>     of sight V2V
>     but not reach the internet, or the need of  a local MANET / RPL
>     that will
>     accept to route those addresses, or the security / address
>     ownership validation
>     issues ?
>     <snip>
>        A single subnet prefix announced by an RSU can span multiple
>     vehicles
>        in VANET.  For example, in Figure 1, for Prefix 1, three vehicles
>        (i.e., Vehicle1, Vehicle2, and Vehicle5) can construct a connected
>        VANET.  Also, for Prefix 2, two vehicles (i.e., Vehicle3 and
>        Vehicle6) can construct another connected VANET, and for Prefix 3,
>        two vehicles (i.e., Vehicle4 and Vehicle7) can construct another
>        connected VANET.  Alternatively, each vehicle could employ an OMNI
>        interface with their own ULAs such that no topologically-oriented
>        subnet prefixes need be announced by the RSU.
>     >>>  same as above. This seems to restate the same thing, derive
>     an address
>     from a topologically correct prefix or use your own with
>     limitations to be
>     described.
>     <snip>
>        For IPv6 packets transported over IEEE 802.11-OCB, [RFC8691]
>        specifies several details, including Maximum Transmission Unit
>     (MTU),
>        frame format, link-local address, address mapping for unicast and
>        multicast, stateless autoconfiguration, and subnet structure.  An
>        Ethernet Adaptation (EA) layer is in charge of transforming some
>        parameters between the IEEE 802.11 MAC layer and the IPv6 network
>        layer, which is located between the IEEE 802.11-OCB's logical link
>        control layer and the IPv6 network layer.  This IPv6 over
>     802.11-OCB
>        can be used for both V2V and V2I in IPv6-based vehicular networks.
>     >>>  solution space.
>     <snip>
>        An IPv6 mobility solution is needed for the guarantee of
>        communication continuity in vehicular networks so that a vehicle's
>        TCP session can be continued, or UDP packets can be delivered to a
>        vehicle as a destination without loss while it moves from an
>     IP-RSU's
>        wireless coverage to another IP-RSU's wireless coverage.  In
>        Figure 1, assuming that Vehicle2 has a TCP session (or a UDP
>     session)
>        with a corresponding node in the vehicular cloud, Vehicle2 can move
>        from IP-RSU1's wireless coverage to IP-RSU2's wireless
>     coverage.  In
>        this case, a handover for Vehicle2 needs to be performed by
>     either a
>        host-based mobility management scheme (e.g., MIPv6 [RFC6275]) or a
>        network-based mobility management scheme (e.g., PMIPv6
>     [RFC5213] and
>        AERO [RFC6706BIS]).
>        In the host-based mobility scheme (e.g., MIPv6), an IP-RSU plays a
>        role of a home agent.  On the other hand, in the network-based
>        mobility scheme (e.g., PMIPv6, an MA plays a role of a mobility
>        management controller such as a Local Mobility Anchor (LMA) in
>        PMIPv6, which also serves vehicles as a home agent, and an IP-RSU
>        plays a role of an access router such as a Mobile Access Gateway
>        (MAG) in PMIPv6 [RFC5213].  The host-based mobility scheme needs
>        client functionality in IPv6 stack of a vehicle as a mobile
>     node for
>        mobility signaling message exchange between the vehicle and home
>        agent.  On the other hand, the network-based mobility scheme
>     does not
>        need such a client functionality for a vehicle because the network
>        infrastructure node (e.g., MAG in PMIPv6) as a proxy mobility agent
>        handles the mobility signaling message exchange with the home agent
>        (e.g., LMA in PMIPv6) for the sake of the vehicle.
>        There are a scalability issue and a route optimization issue in the
>        network-based mobility scheme (e.g., PMIPv6) when an MA covers a
>        large vehicular network governing many IP-RSUs. In this case, a
>        distributed mobility scheme (e.g., DMM [RFC7429]) can mitigate the
>        scalability issue by distributing multiple MAs in the vehicular
>        network such that they are positioned closer to vehicles for route
>        optimization and bottleneck mitigation in a central MA in the
>        network-based mobility scheme.  All these mobility approaches
>     (i.e.,
>        a host-based mobility scheme, network-based mobility scheme, and
>        distributed mobility scheme) and a hybrid approach of a combination
>        of them need to provide an efficient mobility service to vehicles
>        moving fast and moving along with the relatively predictable
>        trajectories along the roadways.
>        In vehicular networks, the control plane can be separated from the
>        data plane for efficient mobility management and data forwarding by
>        using the concept of Software-Defined Networking (SDN)
>        [RFC7149][DMM-FPC].  Note that Forwarding Policy Configuration
>     (FPC)
>        in [DMM-FPC], which is a flexible mobility management system, can
>        manage the separation of data-plane and control-plane in DMM.  In
>        SDN, the control plane and data plane are separated for the
>     efficient
>        management of forwarding elements (e.g., switches and routers)
>     where
>        an SDN controller configures the forwarding elements in a
>     centralized
>        way and they perform packet forwarding according to their
>     forwarding
>        tables that are configured by the SDN controller.  An MA as an SDN
>        controller needs to efficiently configure and monitor its
>     IP-RSUs and
>        vehicles for mobility management, location management, and security
>        services.
>        The mobility information of a GPS receiver mounted in its vehicle
>        (e.g., position, speed, and direction) can be used to accommodate
>        mobility-aware proactive handover schemes, which can perform the
>        handover of a vehicle according to its mobility and the wireless
>        signal strength of a vehicle and an IP-RSU in a proactive way.
>        Vehicles can use the TCC as their Home Network having a home agent
>        for mobility management as in MIPv6 [RFC6275] and PMIPv6 [RFC5213],
>        so the TCC (or an MA inside the TCC) maintains the mobility
>        information of vehicles for location management. IP tunneling over
>        the wireless link should be avoided for performance efficiency.
>        Also, in vehicular networks, asymmetric links sometimes exist and
>        must be considered for wireless communications such as V2V and V2I.
>     >>>  This is all very informative text but does not state a
>     problem. Is there a
>     problem is left to be solved or are we assessing the applicability of
>     protocols? Could it for instance, forward point to issues
>     discussed in section
>     5?
>     <snip>
>        As shown in Figure 3, as internal networks, a vehicle's moving
>        network and an EN's fixed network are self-contained networks
>     having
>        multiple subnets and having an edge router (e.g., IP-OBU and
>     IP-RSU)
>        for the communication with another vehicle or another EN.  The
>        internetworking between two internal networks via V2I communication
>        requires the exchange of the network parameters and the network
>        prefixes of the internal networks.  For the efficiency, the network
>        prefixes of the internal networks (as a moving network) in a
>     vehicle
>        need to be delegated and configured automatically.  Note that a
>        moving network's network prefix can be called a Mobile Network
>     Prefix
>        (MNP) [OMNI].
>     >>> Then again you’re overselling OMNI. MNP is originally defined here
>     <> and
>     that’s a reference
>     you can use normatively.
>     <snip>
>        As shown in Figure 3, the addresses used for IPv6 transmissions
>     over
>        the wireless link interfaces for IP-OBU and IP-RSU can be either
>        global IPv6 addresses, or IPv6 ULAs as long as IPv6 packets can be
>        routed within vehicular networks [OMNI].
>     >>> Then again you’re overselling OMNI. There needs to  be a
>     routing protocol
>     like a MANET that will accept to carry the
>      MNPs, and that must be implemented by the infra and both cars.
>     The OMNI spec
>      is clear on that. This is why at first glance I see OMNI as a
>     full mobile
>      router in a bump in the stack. Now what is the problem behind
>     this? No such
>      protocol at IETF? Too many to choose from? No deployment?
>     <snip>
>     When global IPv6 addresses
>        are used, wireless interface configuration and control overhead for
>        Duplicate Address Detection (DAD) [RFC4862] and Multicast Listener
>        Discovery (MLD) [RFC2710][RFC3810] should be minimized to
>     support V2I
>        and V2X communications for vehicles moving fast along roadways;
>     when
>        ULAs and the OMNI interface are used, no DAD nor MLD messaging is
>        needed.
>     >>> Then again you’re overselling OMNI. Isn’t it the no dad needed
>     a property
>     of injecting a BYOA in the fabric for an GUA MIP Home Address
>     which is known to
>     be unique at home? >>> OTOH, autoconf’ing a random ULA “FD…”prefix
>     has lesser
>     DAD properties than autoconf’ing a random 64bit IID in a classical
>     subnet. So
>     who says DAD isn’t required for OMNI ULA? >>> note that IMHO DAD
>     on wireless is
>     a lot more harm than good, and I agree that with a good pseudo
>     random generator
>     the ULA has no chance to collision in the real world, as OMNI
>     claims. It’s just
>     that your argument here plays the other way, because there are
>     less random bits
>     (56)  in the ULA prefix than in the IID (62), and if one starts
>     using more
>     prefix bits to be non-random, there will be a time when DAD on
>     prefix is needed.
>     <snip>
>        Let us consider the upload/download time of a vehicle when it
>     passes
>        through the wireless communication coverage of an IP-RSU.  For a
>        given typical setting where 1km is the maximum DSRC communication
>        range [DSRC] and 100km/h is the speed limit in highway, the
>     dwelling
>        time can be calculated to be 72 seconds by dividing the diameter of
>        the 2km (i.e., two times of DSRC communication range where an
>     IP-RSU
>        is located in the center of the circle of wireless
>     communication) by
>        the speed limit of 100km/h (i.e., about 28m/s). For the 72 seconds,
>        a vehicle passing through the coverage of an IP-RSU can upload and
>        download data packets to/from the IP-RSU.
>     <snip>
>     4.3.  V2V-based Internetworking
>     >>> In this section it looks like the cars are in a stable line of
>     sight
>     relationship. Which is probably fine for a platoon, but when you
>     drive along
>     with friends in different cars, you realize that the line of sight
>     assumption
>     does not stand over time. Soon enough, other cars meddle in, and
>     possibly one
>     of the cars drives faster and too far ahead so you need the infra
>     to relay,
>     possibly over multiple infra hops.
>     >>> so in this section, I’d expect to see a Vehicle communicating
>     with another
>     one and using either line of sight or V2V relaying but also using
>     relay via V2I
>     (multihop I2I not just hub and spoke V2I2V ), alternatively to
>     together for
>     redundancy. Is that part of the problem?
>     >>> reading deeper section 5 I found excellent text on routing via
>     V and via I.
>     This tells that section 4 does not play a good role at justifying
>     section 5.
>     Maybe keep section 4 for another doc?
>     >>> What kind or reliability is required in a V2V use case? Do you
>     think ND can
>     handle it? Or MANET? What would be the assumption on L2 (roaming
>     time, unicast
>     vs P2MP) and on L3 (reliability ala DetNet/RAW). Should we have
>     some L3
>     redundancy?
>     <snip>
>     5.  Problem Statement
>     <snip>
>        In order to specify protocols using the architecture mentioned in
>        Section 4.1, IPv6 core protocols have to be adapted to overcome
>        certain challenging aspects of vehicular networking.  Since the
>        vehicles are likely to be moving at great speed, protocol exchanges
>        need to be completed in a time relatively short compared to the
>        lifetime of a link between a vehicle and an IP-RSU, or between two
>        vehicles.
>     >>> Any order of magnitude?
>     >>> Can you indicate whether this already rules out certain
>     procedures, e.g.
>     DAD ?
>        The lifetime of a session varies depending on the session's
>     type such
>        as a web surfing, voice call over IP, and DNS query. 
>     Regardless of a
>        session's type, to guide all the IPv6 packets to their destination
>        host, IP mobility should be supported for the session.
>     >>> this seems to be for unicast when you know who to talk to. Is
>     there a need
>     some multicast groups like anybody around interested in topic blah
>     like I could
>     be multicasting the speed of vehicles coming the other way that I
>     crossed
>     recently, for use of vehicles that I’m crossing now, so they can
>     see a slowdown
>     on advance
>        Thus, the time constraint of a wireless link has a major impact on
>        IPv6 Neighbor Discovery (ND).  Mobility Management (MM) is also
>        vulnerable to disconnections that occur before the completion of
>        identity verification and tunnel management. This is especially
>     true
>        given the unreliable nature of wireless communication.  This
>     section
>        presents key topics such as neighbor discovery and mobility
>        management.
>     >>> Only ND? What about the MANET?
>     >>> how fast should ND be to be suitable?
>     >>> is there also a bandwidth check? You can make things much
>     faster if you
>     dedicate a lot of spectrum to it. But that can also be a waste.
>     5.1.  Neighbor Discovery
>     <snip>
>        The requirements for IPv6 ND for vehicular networks are
>     efficient DAD
>        and NUD operations.
>     >>> Not lookup? Is it the intention to use IP unicast over MAC
>     broadcast, which
>     is a good idea in my book?
>      <snip>
>           This merging and partitioning should be considered for the
>        IPv6 ND such as IPv6 Stateless Address Autoconfiguration (SLAAC)
>        [RFC4862].
>     >>> Not lookup? Is it the intention to use IP unicast over MAC
>     broadcast, which
>     is a good idea in my book?
>      <snip>
>        Also, the partitioning of a VANET may make vehicles with the same
>        prefix be physically unreachable.  Also, SLAAC needs to prevent
>     IPv6
>        address duplication due to the merging of VANETs.  According to the
>        merging and partitioning, a destination vehicle (as an IPv6 host)
>        needs to be distinguished as either an on-link host or an off-link
>        host even though the source vehicle uses the same prefix as the
>        destination vehicle.
>     >>> should reference to draft-nordmark-intarea-ippl
>        To efficiently prevent IPv6 address duplication due to the VANET
>        partitioning and merging from happening in vehicular networks, the
>        vehicular networks need to support a vehicular-network-wide DAD by
>        defining a scope that is compatible with the legacy DAD.  In this
>        case, two vehicles can communicate with each other when there
>     exists
>        a communication path over VANET or a combination of VANETs and IP-
>        RSUs, as shown in Figure 1.  By using the
>     vehicular-network-wide DAD,
>        vehicles can assure that their IPv6 addresses are unique in the
>        vehicular network whenever they are connected to the vehicular
>        infrastructure or become disconnected from it in the form of VANET.
>     >>> Excellent
>        ND time-related parameters such as router lifetime and Neighbor
>        Advertisement (NA) interval need to be adjusted for vehicle
>     speed and
>        vehicle density.  For example, the NA interval needs to be
>        dynamically adjusted according to a vehicle's speed so that the
>        vehicle can maintain its neighboring vehicles in a stable way,
>        considering the collision probability with the NA messages sent by
>        other vehicles.
>     >>> Is that a problem or just an operational setting that needs to
>     be found?
>     >>> Do we need to reconsider the concepts of those timers?
>     <snip>
>        Thus, in IPv6-based vehicular networking, IPv6 ND should have
>     minimum
>        changes for the interoperability with the legacy IPv6 ND used
>     in the
>        Internet, including the DAD and NUD operations.
>     >>> I do not find the logical link with the text before, why is
>     this a “thus”?
>     >>> why should the ND inside the VANET be constrained to be
>     interoperable? This
>     may place constraints on the solution.
>     5.1.1.  Link Model
>        A prefix model for a vehicular network needs to facilitate the
>     >>> Do you mean a “subnet model” as opposed to “prefix model”.
>     >>> it would make this piece and the next should refer to
>     draft-thubert-6man-ipv6-over-wireless for IPv6 over P2MP /NBMA,
>     for both link
>     and subnet issues. The general ideas are the same, but the gory
>     details here
>     are slightly incorrect, like this notion of prefix model than
>     comes out of the
>     blue. The model is really the subnet model for the subnet
>     associated to P2MP.
>        communication between two vehicles with the same prefix
>     regardless of
>        the vehicular network topology as long as there exist bidirectional
>        E2E paths between them in the vehicular network including
>     VANETs and
>        IP-RSUs.  This prefix model allows vehicles with the same prefix to
>        communicate with each other via a combination of multihop V2V and
>        multihop V2I with VANETs and IP-RSUs.  Note that the OMNI interface
>        supports an NBMA link model where multihop V2V and V2I
>     communications
>        use each mobile node's ULAs without need for any DAD or MLD
>        messaging.
>     >>> again overselling OMNI.
>     >>> I kinda agree about the OMNI interface model, nothing against
>     that. But you
>     must see that there needs a lot more than what the OMNI interface
>     to get
>     packets across V and I hops to the destination. Like routing ala
>     MANET,
>     redundancy handling ala DetNet because it will be very lossy, path
>     management
>     ala RAW to optimize delivery vs. spectrum… And OMNI ignores ND so
>     it does not
>     solve the ND problems above.
>        IPv6 protocols work under certain assumptions that do not
>     necessarily
>        hold for vehicular wireless access link types other than OMNI/NBMA
>        [VIP-WAVE][RFC5889]; the rest of this section discusses
>     implications
>        for those link types that do not apply when the OMNI/NBMA link
>     model
>     >>> again overselling OMNI.
>     >>> The keyword here is P2MP / NBMA, and OMNI is one interface
>     that accepts
>     that. There are others. IBM’s IPv4 over Frame relay was already
>     P2MP / NBMA,
>     using routing to complete the partial mesh in P2MP. The text seems
>     to imply
>     that OMNI is the only way to do that and that’s wrong. Also OMNI
>     is loaded with
>     other stuff than a plain P2MP capable interface. And ND over P2MP
>     is not done
>     by OMNI, OMNI only makes classical ND worse and only works in a
>     full mesh. OTOH
>     RFC 8505, which is designed to do ND for P2MP /NBMA would indeed
>     work very well
>     within an OMNI interface and solve those problems. >>> My point is
>     that you
>     need to tell the full story or refrain from entering solution
>     space in this doc
>     <snip>
>        There is a relationship between a link and a prefix, besides the
>        different scopes that are expected from the link-local and global
>        types of IPv6 addresses.  In an IPv6 link, it is assumed that all
>        interfaces which are configured with the same subnet prefix and
>     with
>        on-link bit set can communicate with each other on an IPv6 link.
>     >>> not assumed; that’s what the onlink but set tells. The
>     conclusion should be
>     that the VANET cannot set the O bit.
>        However, the vehicular link model needs to define the relationship
>        between a link and a prefix, considering the dynamics of wireless
>        links and the characteristics of VANET.
>     <snip>
>        From the previous observation, a vehicular link model should
>     consider
>        the frequent partitioning and merging of VANETs due to vehicle
>        mobility.  Therefore, the vehicular link model needs to use an on-
>        link prefix and off-link prefix according to the network
>     topology of
>        vehicles such as a one-hop reachable network and a multihop
>     reachable
>     >>> No, the once a node saw a O bit set that sticks even if it
>     sees other
>     advertisements of the PIO with the O bit not set. >>> This is a
>     global and
>     intrinsic property of the prefix (and an attack vector that could
>     be mentioned
>     in the sec section). >>> the VANET prefix must never come with the
>     O bit set.
>     <snip>
>        network (or partitioned networks).  If the vehicles with the same
>        prefix are reachable from each other in one hop, the prefix
>     should be
>        on-link.
>     >>>> No, see above; but the router may redirect though it is
>     really risky
>     unless this is a stable situation like a parking place.
>        Thus, in IPv6-based vehicular networking, the vehicular link model
>        should have minimum changes for interoperability with standard IPv6
>        links in an efficient fashion to support IPv6 DAD, MLD and NUD
>        operations.  When the OMNI NBMA link model is used, there are
>     no link
>        model changes nor DAD/MLD messaging required.
>     >>>> again overselling OMNI.
>     >>>> You need a good P2MP subnet model with routing support when
>     the mesh is
>     partial. My company alone has been shipping million of nodes that
>     build subnets
>     of thousands, and that was done using IETF standards.
>     <snip>
>        For vehicular networks with high mobility and density, the DAD
>     needs
>        to be performed efficiently with minimum overhead so that the
>        vehicles can exchange a driving safety message (e.g., collision
>        avoidance and accident notification) with each other with a short
>        interval (e.g., 0.5 second) by a technical report from NHTSA
>        (National Highway Traffic Safety Administration)
>     [NHTSA-ACAS-Report].
>        Such a driving safety message may include a vehicle's mobility
>        information (i.e., position, speed, direction, and acceleration/
>        deceleration).  The exchange interval of this message is 0.5
>     second,
>        which is required to allow a driver to avoid a rear-end crash from
>        another vehicle.
>     >>> IPv6 over broadcast MAC (used to be called internet 0, 10+
>     years ago)
>     solves that MAC issue since there is no MAC.
>     5.1.3.  Routing
>        For multihop V2V communications in either a VANET or VANETs via IP-
>        RSUs, a vehicular Mobile Ad Hoc Networks (MANET) routing
>     protocol may
>        be required to support both unicast and multicast in the links
>     of the
>        subnet with the same IPv6 prefix.  However, it will be costly
>     to run
>        both vehicular ND and a vehicular ad hoc routing protocol in
>     terms of
>        control traffic overhead [ID-Multicast-Problems].
>     >>> we do that with IETF standards on battery operated devices
>     already. Using
>     RFC 8505 for the UNI and RPL for the NNI. It is scalable (we’ve
>     seen 30 hops in
>     meshes of thousands in the real world though it’s not the normal
>     operational
>     model, but can happen to maintain connectivity during the reboot
>     of a root) and
>     does not use broadcast. RPL was initially designed as a V2V2V
>     protocol but
>     found its market on the IoT. I’m sure the protocol would gladly
>     come back to
>     its roots.
>        A routing protocol for a VANET may cause redundant wireless
>     frames in
>        the air to check the neighborhood of each vehicle and compute the
>        routing information in a VANET with a dynamic network topology
>        because the IPv6 ND is used to check the neighborhood of each
>        vehicle.  Thus, the vehicular routing needs to take advantage
>     of the
>        IPv6 ND to minimize its control overhead.
>     >>> A clean description of the interaction of RPL and RFC 8505 in
>     our IoT
>     networks. Note that the speed of the PHY in VANET balanced the
>     instability of
>     the topology, and RPL still applies. Note also that RPL uses DV
>     with a routing
>     stretch in order to minimize the topology awareness that’s needed
>     in each node,
>     which results in minimal signaling.
>     5.2.  Mobility Management
>     <snip>
>        For a mobility management scheme in a shared link, where the
>     wireless
>        subnets of multiple IP-RSUs share the same prefix, an efficient
>        vehicular-network-wide DAD is required.  If DHCPv6 is used to
>     assign
>        a unique IPv6 address to each vehicle in this shared link,
>     >>> I would not use the term link, or shared. Maybe shared link ->
>     domain?
>     <snip>
>     the DAD is
>        not required.  On the other hand, for a mobility management scheme
>        with a unique prefix per mobile node (e.g., PMIPv6 [RFC5213]
>     and OMNI
>        [OMNI]), DAD is not required because the IPv6 address of a
>     vehicle's
>        external wireless interface is guaranteed to be unique.
>     >>> again overselling OMNI
>     >>> As I said earlier, this is wring there are (64*) more chances of a
>     collision in OMNI prefixes than in IPv6 IIDs. >>> OMNI prefixes
>     can collision,
>     home addresses that are unique on a home network cannot. >>> Now
>     if both the
>     OMNI prefix and the IID are good randoms, then obviously, the
>     chances of
>     collisions round up to 0. >>> Collision is certainly not my worst
>     fear.
>       There is a
>        tradeoff between the prefix usage efficiency and DAD overhead. 
>     Thus,
>        the IPv6 address autoconfiguration for vehicular networks needs to
>        consider this tradeoff to support efficient mobility management.
>     >>> This is way too superficial and hides the reality of things.
>     - Using a VANET Infra prefix allows direct routability to the
>     internet which
>     BYOA does not since the BYOA is not topologically correct. Yes, it
>     costs a DAD
>     with classic ND, but it does not with RCF8505 and the draft fails
>     to mention
>     that. - A BYOA needs a tunnel home, and the node needs to know who
>     is reachable
>     inside the VANET and what is not to decide to tunnel or not; this is a
>     difficult problem (vs. control place overhead) that is not
>     discussed here.
>     <snip>
>        For the case of a multihomed network, a vehicle can follow the
>     first-
>        hop router selection rule described in [RFC8028].  That is, the
>        vehicle should select its default router for each prefix by
>        preferring the router that advertised the prefix.
>     >>> Still router discovery (in and out) must be very fast. Thing
>     of the RA
>     intervale in MIPv6. Is that sufficient? Too expensive?
>     <snip>
>     6.  Security Considerations
>     >>> Any discussion on the security of classical ND and other
>     operational issues
>     (rfc6583) ?
>     <snip>
>        Security and privacy are paramount in V2I, V2V, and V2X networking.
>        Vehicles and infrastructure must be authenticated in order to
>        participate in vehicular networking.  Also, in-vehicle devices
>     (e.g.,
>        ECU) and a driver/passenger's mobile devices (e.g., smartphone and
>        tablet PC) in a vehicle need to communicate with other in-vehicle
>        devices and another driver/passenger's mobile devices in another
>        vehicle, or other servers behind an IP-RSU in a secure way.  Even
>        though a vehicle is perfectly authenticated and legitimate, it
>     may be
>        hacked for running malicious applications to track and collect its
>        and other vehicles' information.  In this case, an attack
>     mitigation
>        process may be required to reduce the aftermath of malicious
>        behaviors.
>     >>> The section should mention that both with classical ND and
>     BYOA, addresses
>     can be impersonated, and RFC 8928 protects against that in both
>     cases while
>     maintaining privacy.
>        Even though vehicles can be authenticated with valid
>     certificates by
>        an authentication server in the vehicular cloud, the authenticated
>     >>> Is PKI feasible (deploying it in every car?). Is it fast
>     enough? Is it
>     really what IPWAVE thinks vehicle should use????? >>> e.g. why
>     would one need
>     to authenticate to a V2I network? >>> from the text earlier in the
>     doc, it
>     seemed that what you really want is access that is fast to join,
>     capable of
>     offering the reachability you want, anonymous, and innocuous (cars
>     can not harm
>     one another).
>        vehicles may harm other vehicles, so their communication activities
>        need to be logged in either a central way through a logging server
>        (e.g., TCC) in the vehicular cloud or a distributed way (e.g.,
>        blockchain [Bitcoin]) along with other vehicles or infrastructure.
>        For the non-repudiation of the harmful activities of malicious
>     nodes,
>        a blockchain technology can be used [Bitcoin]. Each message from a
>        vehicle can be treated as a transaction and the neighboring
>     vehicles
>        can play the role of peers in a consensus method of a blockchain
>        [Bitcoin][Vehicular-BlockChain].  For a blockchain's efficient
>        consensus in vehicular networks having fast moving vehicles, a new
>        consensus algorithm needs to be developed or an existing consensus
>        algorithm needs to be enhanced.
>     >>> solution space; better express the security needs since this
>     is a PS.
>     <snip>
>        To identify malicious vehicles among vehicles, an authentication
>        method is required.
>     >>> No. As said earlier a vehicle can be infected. You need
>     innocuousness.which
>     can come from things like isolation, zerotrust, and protocols that are
>     difficult to hack around. Classical IPv6 ND is open bar. RFC
>     8505/8928 is
>     protected by construction, anonymous, and fast.
>     <snip>
>        For the setup of a secure channel over IPsec or TLS, the
>     multihop V2I
>        communications over DSRC is required in a highway for the
>        authentication by involving multiple intermediate vehicles as relay
>        nodes toward an IP-RSU connected to an authentication server in the
>        vehicular cloud.  The V2I communications over 5G V2X (or LTE
>     V2X) is
>        required to allow a vehicle to communicate directly with a
>     gNodeB (or
>        eNodeB) connected to an authentication server in the vehicular
>     cloud.
>     >>> solution space. Instead, you could mention that setting up
>     secured channels
>     between cars that cross one another might not complete in time to
>     establish the
>     communication channel, and that the innocuousness must come from
>     zerotrust in
>     the transactions between the cars.
>        For the IPv6 ND, the DAD is required to ensure the uniqueness
>     of the
>        IPv6 address of a vehicle's wireless interface.
>     >>> for classical ND (SLAAC) that’s true. That is not with RFC
>     8505, since the
>     infra maintains a table of all addresses in use in the prefix and
>     blocks
>     duplicates without the RFC 4862 DAD method. The stateful autoconf
>     address grant
>     is immediate.
>                                    This DAD can be used
>        as a flooding attack that uses the DAD-related ND packets
>        disseminated over the VANET or vehicular networks.
>     >>> also for DOS attacks. You can block a owner from using an
>     address. A
>     reference to rfc6959 is much needed here.
>     <snip>
>      This possibility
>        indicates that the vehicles and IP-RSUs need to filter out
>     suspicious
>        ND traffic in advance.  Based on the SEND [RFC3971] mechanism, the
>        authentication for routers (i.e., IP-RSUs) can be conducted by only
>        selecting an IP-RSU that has a certification path toward trusted
>        parties.  For authenticating other vehicles, the cryptographically
>        generated address (CGA) can be used to verify the true owner of a
>        received ND message, which requires to use the CGA ND option in the
>        ND protocols.  For a general protection of the ND mechanism,
>     the RSA
>        Signature ND option can also be used to protect the integrity
>     of the
>        messages by public key signatures.  For a more advanced
>        authentication mechanism, a distributed blockchain-based mechanism
>        [Vehicular-BlockChain] can be used.
>     >>> solution space. Again, the draft should focus on problems and
>     needs. The
>     problem here is that SEND is complex, and not implemented in the
>     major stack.
>     It relies on PKI for trusting the router. The V2I need is a
>     zerotrust model
>     where one V, the other local Vs, and the I, can help each other
>     anonymously and
>     harmlessly. <snip>
>     8.  Informative References
>     >>> no normative reference?
>     >>> no normative reference?
>     <snip>
>     Voila!
>     Keep safe;
>     Pascal
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