IPv6 Mobile Object Networking (IPMON): Problem Statement and Use Cases

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Table of Contents

1. Introduction

New Radio (NR) called 5G is a popular wireless communication technology for mobile devices such as smartphone, smart watch, and tablet [TS23501][TS38300]. This 5G-based communication also plays an important role of the interaction among a person's mobile devices, Internet-of-Things (IoT) devices and autonomous networked objects (e.g., robot and drone).¶

A moving object is defined as a physically movable networked device with a wireless networking capability such as cellular communications (e.g., 4G LTE and 5G) and IEEE 802.11 family (e.g., 802.11-OCB), which may be a terrestrial vehicle (e.g., car and motorcycle), a user's smart device (e.g., smartphone, smart watch, and tablet), an aerial vehicle (e.g., drone and helicopter), and a marine vehicle (e.g., boat and ship). These mobile objects are called vehicles in this document.¶

The main scenarios of vehicular communications are vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), and vehicle-to-everything (V2X) communications. First, this document explains use cases using V2V, V2I, and V2X networking over 5G. Next, for IPv6-over-5G vehicular networks, it makes a gap analysis of current IPv6 protocols (e.g., IPv6 Neighbor Discovery).¶

2. Terminology

This document uses the terminology described in [RFC8691][RFC9365].¶

3. Use Cases

This section explains use cases of V2V, V2I, and V2X networking. Those three kinds of use cases are the same as the use cases in IPWAVE (IPv6 Wireless Access in Vehicular Environments) Problem Statement [RFC9365] by assuming that the wiress access technology is 5G-based V2V, V2I, and V2X instead of IEEE 802.11-OCB-based V2V, V2I, and V2X. For the detailed discussion on the V2V, V2I, and V2X use cases, refer to the use cases in [RFC9365].¶

4. 5G Vehicular Networks

This section describes the context for vehicular networks supporting 5G V2V, V2I, and V2X communications among vehicles, gNodeBs, and other User Equipments (UEs) such as smartphones, smart watches, and tablets [TS23287]. As shown in Figure 1, infrastructure nodes for vehicles are gNodeBs in 5G vehicular networks.¶

                     Traffic Control Center in Vehicular Cloud
                    *******************************************
+-------------+    *                                           *
|Correspondent|   *             +-----------------+             *
|    Node     |<->*             | Mobility Anchor |             *
+-------------+   *             +-----------------+             *
                  *                      ^                      *
                  *                      |                      *
                   *                     v                     *
                    *******************************************
                    ^                   ^                     ^
                    |                   |                     |
                    |                   |                     |
                    v                   v                     v
              +---------+           +---------+           +---------+
              | gNodeB1 |<--------->| gNodeB2 |<--------->| gNodeB3 |
              +---------+           +---------+           +---------+
                  ^                     ^                    ^
                  :                     :                    :
           +-----------------+ +-----------------+   +-----------------+
           |      : V2I      | |        : V2I    |   |       : V2I     |
           |      v          | |        v        |   |       v         |
+--------+ |   +--------+    | |   +--------+    |   |   +--------+    |
|Vehicle1|===> |Vehicle2|===>| |   |Vehicle3|===>|   |   |Vehicle4|===>|
+--------+<...>+--------+<........>+--------+    |   |   +--------+    |
           V2V     ^         V2V        ^        |   |        ^        |
           |       : V2V     | |        : V2V    |   |        : V2V    |
           |       v         | |        v        |   |        v        |
           |  +--------+     | |   +--------+    |   |    +--------+   |
           |  |Vehicle5|===> | |   |Vehicle6|===>|   |    |Vehicle7|==>|
           |  +--------+     | |   +--------+    |   |    +--------+   |
           +-----------------+ +-----------------+   +-----------------+
                 Subnet1              Subnet2              Subnet3
                (Prefix1)            (Prefix2)            (Prefix3)

        <----> Wired Link   <....> Wireless Link   ===> Moving Direction

                           Data Network
             *****************************************
            *                                         *
           *            +-----------------+            *
          *             | V2X Application |             *             N6
         *              |      Server     |<-------------*----------------+
         *              +-----------------+              *                |
          *                      ^                      *                 |
           *                     |                     *                  |
            *                    v                    *                   |
             *****************************************                    |
                                                                          |
                                  5GC                                     |
+---------------------------------------------------------------------+   |
|             +---------+  +---------+  +---------+  +---------+      |   |
|             |   UDM   |  |   PCF   |  |   NEF   |  |    AF   |      |   |
|             +---------+  +---------+  +---------+  +---------+      |   |
|                  ^            ^            ^            ^           |   |
|                  |            |            |            |           |   |
|                  |            |            |            |           |   |
|                  v            v            v            v           |   |
|       ---------------------------------------------------------     |   |
|          ^            ^            ^            ^                   |   v
|          |            |            |            |               +---------+
|          |            |            |            |          ---->|   UPF   |
|          v            v            v            v         /     +---------+
|      +---------+  +---------+  +---------+  +---------+  /          |
|      |   NRF   |  |   UDR   |  |   AMF   |  |   SMF   | /           |
|      +---------+  +---------+  +---------+  +---------+             |
+---------------------------------------------------------------------+
                                    ^
                                    |
                                    |
                                    v
+-------------------+       +--------------+     Uu      +-------------------+
|        UE1        |       |    NG-RAN    |<...........>|        UE4        |
| (V2X Application) |       +--------------+             | (V2X Application) |
+-------------------+                  ^                 +-------------------+
          ^                            :                           ^
          : PC5 (V5)                   : Uu                        : PC5 (V5)
          v                            v                           :
+-------------------+    PC5 (V5)  +-------------------+           :
|        UE2        |<............>|        UE3        |<...........
| (V2X Application) |              | (V2X Application) |
+-------------------+              +-------------------+
                   <----> Wired Link   <....> Wireless Link

Mobility Anchor (MA) is a node that maintains IPv6 addresses and mobility information of vehicles in a road network to support their IPv6 address autoconfiguration and mobility management with a binding table. An MA has End-to-End (E2E) connections (e.g., tunnels) with IP-RSUs under its control for the address autoconfiguration and mobility management of the vehicles. This MA is similar to a Local Mobility Anchor (LMA) in PMIPv6 [RFC5213] for network-based mobility management. Mobility Anchor consists of 5G core functions such as PCF (Policy Control Function), AMF (Access and Mobility Management Function), SMF (Session Management Function), and UPF (User Plane Function) as shown in Figure 2. Note that Figure 2 shows an example 5G network architecture for vehicular networks.¶

Traffic Control Center (TCC) is a system that manages road infrastructure nodes (e.g., gNodeBs, MAs, traffic signals, and loop detectors), and also maintains vehicular traffic statistics (e.g., average vehicle speed and vehicle inter-arrival time per road segment) and vehicle information (e.g., a vehicle's identifier, position, direction, speed, and trajectory as a navigation path). TCC is part of a vehicular cloud for vehicular networks.¶

V2V communication between two vehicles as UEs uses a PC5 reference point [TS23287]. V2I communication between a vehicle and a gNodeB uses a Uu reference point [TS23287]. As shown in Figure 1, Vehicle1 can communicate with Vehicle3 via Vehicle2 in the same Vehicular Ad Hoc Network (VANET). In this figure, Vehicle1 can communicate with Correspondent Node via Vehicle2 as a relay node and gNodeB1 as an infrastructure node in a Radio Access Network (RAN) in 5G networks.¶

5. Problem Statement

For 5G V2V by PC5 in unicast mode, one vehicle UE (VehUE) needs to be an IPv6 router for IPv6 Stateless Address Autoconfiguration (SLAAC) [RFC4862]. The 5G V2X specifications [TS23287][TS24587] do not specify which VehUE shall be the IPv6 router for SLAAC. Also, it does not specify how many IPv6 addresses/prefixes a VehUE will have in this case.¶

   ===>                 ===>                 ===>                  ===>
+--------+   SLAAC   +--------+   SLAAC   +--------+ Link-Local +--------+
|Vehicle2|<.........>|Vehicle1|<.........>|Vehicle3|<..........>|Vehicle4|
+--------+           +--------+           +--------+            +--------+
IPv6 Host            IPv6 Router          IPv6 Host             IPv6 Host

        <....> Wireless Link   ===> Moving Direction

As shown in Figure 3, a VehUE (e.g., Vehicle1) among others shall be acting as an IPv6 router using SLAAC to assign IPv6 addresses/prefixes for other VehUEs. In this case, there are several issues as follows:¶

• Which VehUE shall be the IPv6 router for the role to assign IPv6 addresses/prefixes if multiple VehUEs can be or want to be an IPv6 router?¶
• For a VehUE acting as an IPv6 router, how many IPv6 addresses/prefixes will it assign? How much Will the role of an IPv6 router burden the IPv6 router VehUE?¶
• For a VehUE receiving IPv6 addresses/prefixes from a IPv6 router VehUE, how many IPv6 addresses/prefixes will it have on the movement?¶
• If a VehUE (e.g., Vehicle4 in Figure 3) does not have any connection with an IPv6 router VehUE, it will only use an IPv6 link local address for communications. In this case, multihop routing is triggered to forward IPv6 packets. How will this scenario affect the IPv6 networking among VehUEs?¶

For V2V and V2I communications among VehUEs and gNodeB, the 5G specifications [TS23287][TS24587] do not mention that VehUEs will use the same IPv6 configuration. It is necessary to consider whether the VehUEs will use the same prefix or the different prefixes for both V2V and V2I communications.¶

For multihop V2V and V2I among VehUEs and gNodeB, existing routing protocols are costly to maintain a routing table. The 5G specifications [TS23287][TS24587] do not consider how to minimize control traffic overhead for both routing and IPv6 Neighbor Discovery (ND) [RFC4861].¶

Mobility management in 5G V2X is required for the seamless communications between a VehUE and a server in a wired network (e.g., the Internet). It is necessary to consider how to manage the mobility of vehicles that have connections with a server while they are moving along their navigation paths [RFC9365].¶

6. Security Considerations

This section discusses security and privacy for IPv6-over-5G-based vehicular networking. The issues and considerations in 5G-based V2I, V2V, and V2X are the same as those in 802.11-OCB-based V2I, V2V, and V2X in [RFC9365].¶

7. IANA Considerations

This document does not require any IANA actions.¶

Appendix B. Contributors

This document is a group work, greatly benefiting from inputs and texts by Erik Kline (Aalyria) and Eric Vyncke (Cisco). The authors sincerely appreciate their contributions.¶

The following are coauthors of this document:¶

Authors' Addresses