| IPWAVE Working Group | J. Jeong |
| Internet-Draft | Y. Shen |
| Intended status: Standards Track | Z. Xiang |
| Expires: September 29, 2019 | Sungkyunkwan University |
| March 28, 2019 |
Vehicular Mobility Management for IP-Based Vehicular Networks
draft-jeong-ipwave-vehicular-mobility-management-00
This document specifies a vehicular mobility management scheme for IP-based vehicular networks. The vehicular mobility management scheme takes advantage of a vehicular link model based on a multi-link subnet. With a vehicle's mobility information (e.g., position, speed, and direction) and navigation path (i.e., trajectory), it can provide a moving vehicle with proactive and seamless handoff along with its trajectory.
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This document proposes a mobility management scheme for IP-based vehicular networks, which is called vehicular mobility management (VMM). This vehicular mobility management is tailored for a vehicular network architecture and a vehicular link model described in IPWAVE problem statement document [I-D.IPWAVE-PS].
To support the interaction between vehicles or between vehicles and Rode-Side Units (RSUs), Vehicular Neighbor Discovery (VND) is proposed as an enhanced IPv6 Neighbor Discovery (ND) for IP-based vehicular networks [I-D.IPWAVE-VND]. For an efficient IPv6 Stateless Address Autoconfiguration (SLAAC) [RFC4862], VND adopts an optimized Address Registration using a multihop Duplicate Address Detection (DAD). This multihop DAD enables a vehicle to have a unique IP address in a multi-link subnet that consists of multiple wireless subnets with the same IP prefix, which corresponds to wireless coverage of multiple Road-Side Units (RSUs). Also, VND supports IP packet routing via a connected Vehicular Ad Hoc Network (VANET) by letting vehicles exchange the prefixes of their internal networks through their external wireless interface.
The mobility management in this multi-link subnet needs a new approach from the legacy mobility management schemes. This document aims at an efficient mobility management scheme called vehicular mobility management called VMM to support efficient V2V, V2I, and V2X communications in a road network. The VMM takes advantage of the mobility information (e.g., a vehicle's speed, direction, and position) and trajectory (i.e., navigation path) of each vehicle registered into a Traffic Control Center (TCC) in the vehicular cloud.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119].
This document uses the terminology described in [RFC4861] and [RFC4862]. In addition, the following new terms are defined as below:
This section describes a vehicular network architecture for V2V and V2I communication. A vehicle and an RSU have their internal networks including in-vehicle devices or servers, respectively.
A vehicular network architecture for V2I and V2V is illustrated in Figure 1. In this figure, there is a vehicular cloud having a Traffic Control Center (TCC). The TCC has Mobility Anchors (MAs) for the mobility management of vehicles under its control. Each MA is in charge of the mobility management of vehicles under its prefix domain, which is a multi-link subnet of RSUs sharing the same prefix [I-D.IPWAVE-PS]. A vehicular network is a wireless network consisting of RSUs and vehicles. RSUs are interconnected with each other through a wired network, and vehicles can construct Vehicular Ad Hoc Networks (VANET).
*-----------------------------------------*
* TCC in Vehicular Cloud *
* +-------------------------------------+ *
+--------+ * | +---------+ +---------+ | *
| CN1 |<---->* | | MA1 |<------->| MA2 | | *
+--------+ * | +---------+ +---------+ | *
* +-------------------------------------+ *
* ^ ^ *
* | INTERNET | *
*---------v--------------------v----------*
^ ^ ^
| Ethernet | |
| | |
v v v
+--------+ Ethernet +--------+ Ethernet +--------+
| RSU1 |<-------->| RSU2 |<-------->| RSU3 |
+--------+ +--------+ +--------+
^ ^ ^
: : :
+-----------------------------------+ +-----------------+
| : V2I V2I : | | V2I : |
| v v | | v |
+--------+ | +--------+ +--------+ | | +--------+ |
|Vehicle1|======>|Vehicle2|======>|Vehicle3|====>| | |Vehicle4|====>|
| |<.....>| |<.....>| | | | | | |
+--------+ V2V +--------+ V2V +--------+ | | +--------+ |
| | | |
+-----------------------------------+ +-----------------+
Subnet1 Subnet2
<----> Wired Link <....> Wireless Link ===> Moving Direction
Figure 1: A Vehicular Network Architecture for V2I and V2V Networking
In Figure 1, three RSUs are deployed either at intersections or along roadways. They are connected to an MA through wired networks. In the vehicular network, there are two subnets such as Subnet1 and Subnet2. Subnet1 is a multi-link subnet consisting of multiple wireless coverage areas of multiple RSUs, and those areas share the same IPv6 prefix to construct a single logical subnet [I-D.IPWAVE-PS]. That is, the wireless links of RSU1 and RSU2 belong to Subnet1. Thus, since Vehicle2 and Vehicle2 use the same prefix for Subnet1 and they are within the wireless communication range, they can communicate directly with each other. Note that in a multi-link subnet, a vehicle (e.g., Vehicle1 and Vehicle2 in Figure 1) can configure its global IPv6 address through an address registration procedure including a multihop Duplicate Address Detection (DAD), which is specified in Vehicular Neighbor Discovery (VND) [I-D.IPWAVE-VND].
On the other hand, Subnet2 uses a prefix different from Subnet1's. Vehicle4 residing in Subnet2 cannot talk to Vehicle3 directly because they belong to different subnets. Vehicles can construct a connected VANET, so they can communicate with each other without the relaying of an RSU, but the forwarding over the VANET. In the case where two vehicles belong to the same multi-link subnet, but they are not connected in the same VANET, they can use RSUs. In Figure 1, even though Vehicle2 are disconnected from Vehicle3, they can communicate indirectly with each other through RSUs such as RSU1 and RSU2.
In Figure 1, it is assumed that Vehicle2 communicates with the corresponding node denoted as CN1 where Vehicle2 is moving in the wireless coverage of RSU1. When Vehicle2 moves out of the coverage of RSU1 and moves into the coverage of RSU2 where RSU1 and RSU2 shares the same prefix, the packets sent by CN1 should be routed toward Vehicle2. Also, when Vehicle2 moves out of the coverage of RSU2 and moves into the coverage of RSU3 where RSU2 and RSU3 use two different prefixes, the packets of CN1 should be delivered to Vehicle2. With a handoff procedure, a sender's packets can be delivered to a destination vehicle which the destination vehicle is moving in the wireless coverage areas. Thus, this document specifies a mobility management scheme in the vehicular network architecture, as shown in Figure 1.
This section explains the detailed procedure of mobility management of a vehicle in a vehicular network as shown in Figure 1.
A mobility management is required for the seamless communication of vehicles moving between the RSUs. When a vehicle moves into the coverage of another RSU, a different IP address is assigned to the vehicle, resulting in the reconfiguration of transport-layer session information (i.e., an end-point's IP address) to avoid service disruption. Considering this issue, this document proposes a handoff mechanism for seamless communication.
In [VIP-WAVE], the authors constructed a network-based mobility management scheme using Proxy Mobile IPv6 (PMIPv6) [RFC5213], which is highly suitable to vehicular networks. This document uses a mobility management procedure similar to PMIPv6 along with prefix discovery.
Vehicle RSU Mobility Anchor
| | |
|-RS with Mobility Info->| |
| [VMI] | |
| | |
| |--------PBU------>|
| | |
| | |
| |<-------PBA-------|
| | |
| | |
| |===Bi-Dir Tunnel==|
| | |
| | |
|<----RA with prefix-----| |
| | |
Figure 2: Message Interaction for a Vehicle's Network Attachment
Figure 2 shows the binding update flow when a vehicle entered the subnet of an RSU. RSUs act as Mobility Anchor Gateway (MAG) defined in [VIP-WAVE]. When it receives an RS message from a vehicle containing its mobility information (e.g., position, speed, and direction), an RSU sends its MA a Proxy Binding Update (PBU) message [RFC5213][RFC3775], which contains a Mobility Option for the vehicle's mobility information. The MA receives the PBU and sets up a Binding Cache Entry (BCE) as well as a bi-directional tunnel (denoted as Bi-Dir Tunnel in Figure 2) between the serving RSU and itself. Through this tunnel, all traffic packets to the vehicle are encapsulated toward the RSU. Simultaneously, the MA sends back a Proxy Binding Acknowledgment (PBA) message to the serving RSU. This serving RSU receives the PBA and sets up a bi-directional tunnel with the MA. After this binding update, the RSU sends back an RA message to the vehicle, which includes the RSU's prefix for the address autoconfiguration of the vehicle.
When the vehicle receives the RA message, it performs the address registration procedure including a multihop DAD for its global IP address based on the prefix announced by the RA message according to the VND [I-D.IPWAVE-VND].
In PMIPv6, a unique prefix is allocated to each vehicle by an MA (i.e., LMA), but in this document, a unique IP address is allocated to each vehicle by an MA through the multihop-DAD-based address registration. This unique IP address allocation can reduce the waste of IP prefixes by the legacy PMIPv6 because vehicles in a multi-link is allocated with a unique IP address based on the same prefix.
Vehicle c-RSU Mobility Anchor n-RSU
| | | |
| |===Bi-Dir Tunnel==| |
| | | |
| | | |
| |----DeReg PBU---->| |
| | | |
| | | |
| |<-------PBA-------| |
| | | |
| | | |
| | | |
| | | |
| | | |
|(------------------RS with Mobility Info-------------->)|
| [VMI] | |
| |<-------PBU-------|
| | |
| | |
| |--------PBA------>|
| | |
| | |
| |===Bi-Dir Tunnel==|
| | |
| | |
|<--------------------RA with prefix---------------------|
| |
Figure 3: Handoff of a Vehicle within One Prefix Domain with PMIPv6
When the vehicle changes its location and its current RSU (denoted as c-RSU) detects that the vehicles moves out of its coverage, c-RSU needs to report the movement of the vehicle into the coverage of another RSU to the MA.
Figure 3 shows the handoff of a vehicle within one prefix domain (i.e., a multi-link subnet) with PMIPv6. As shown in the figure, when the MA receives a new PBU from the new RSU, it changes the tunnel's end-point from the current RSU (c-RSU) to the new RSU (n-RSU). If there is ongoing IP packets toward the vehicle, the MA encapsulates the packets and then forwards them towards n-RSU. Through this network-based mobility management, the vehicle is not aware of any changes at its network layer and can maintain its transport-layer sessions without any disruption.
Vehicle c-RSU n-RSU
| | |
|---------------------| |
|c-RSU detects leaving| |
|---------------------| |
| |--------PBU------>|
| | |
| |===Bi-Dir Tunnel==|
| | |
| |<-------PBA-------|
| | |
| | |
|(--------RS with Mobility Info-------->)|
| [VMI] |
| |
|<------------RA with prefix-------------|
| |
Figure 4: Handoff of a Vehicle within One Prefix Domain with DMM
Figure 4 shows the handoff of a vehicle within one prefix domain (as a multi-link subnet) with DMM [I-D.DMM-PMIPv6]. RSUs are in charge of detecting when a node joins or moves through its domain. If c-RSU detects that the vehicle is going to leave its coverage and to enter the area of an adjacent RSU, it sends a PBU message to inform n-RSU of the handoff of vehicle. If n-RSU receives the PBU message, it constructs a bidirectional tunnel between c-RSU and itself, and then sends back a PBA message as an acknowledgment to c-RSU. If there are ongoing IP packets toward the vehicle, c-RSU encapsulates the packets and then forwards them to n-RSU. When n-RSU detects the entrance of the vehicle, it directly sends an RA message to the vehicle so that the vehicle can assure that it is still connected to a router for its current prefix. If the vehicle sends an RS message to n-RSU, n-RSU responds to the RA message by sending an RA to the vehicle.
When the vehicle moves from a prefix domain to another prefix domain, a handoff between multiple prefix domains is required. As shown in Figure 1, when Vehicle3 moves from the subnet of RSU2 (i.e., Subnet1) to the subnet of RSU3 (i.e., Subnet2), a multiple domain handoff is performed through the cooperation of RSU2, RSU3, MA1 and MA2.
Vehicle c-RSU MA1 MA2 n-RSU | | | | | | |==Bi-Dir Tunnel==| | | | | | | | | | | | | | |---DeReg PBU---->| | | | | |-------PBU----->| | | | | | | | |<------PBA-------| |-------PBA------>| | | | | | | | | |==Bi-Dir Tunnel==| | | | | | | | | | | |(----------------------RS with Mobility Info------------------->)| | | |[VMI] | | | | | | | | | | | | |<----------------------RA with prefix1 (c-RSU)-------------------| | | | | | |<----------------------RA with prefix2 (n-RSU)-------------------| | | | | |
Figure 5: Handoff of a Vehicle between Multiple Prefix Domains with PMIPv6
Figure 5 shows the handoff of a vehicle between two prefix domains (i.e., two multi-link subnets) with PMIPv6. When the vehicle moves out of its current RSU (denoted as c-RSU) belonging to Subnet1, and moves into the next RSU (n-RSU) belonging to Subnet2, c-RSU detects that the vehicles moves out of its coverage. c-RSU reports the movement of the vehicle into the coverage of another RSU (n-RSU) to MA1. MA1 sends MA2 a PBU message to inform MA2 that the vehicle will enter the coverage of n-RSU belonging to MA2. MA2 send n-RSU a PBA message to inform n-RSU that the vehicle will enter the coverage of n-RSU along with handoff context such as c-RSU's context information (e.g., c-RSU's link-local address and prefix called prefix1), and the vehicle's context information (e.g., the vehicle's global IP address and MAC address). After n-RSU receives the PBA message including the handoff context from MA2, it sets up a bi-directional tunnel with MA2, and generates RA messages with c-RSU's context information. That is, n-RSU pretents to be a router belonging to Subnet1. When the vehicle receives the RA from n-RSU, it can maintain its connection with its corresponding node (i.e., CN1). Note that n-RSU also sends RA messages with its domain prefix called prefix2. The vehicle configures another global IP address with prefix2, and can use it for the communication with neighboring vehicles under the coverage of n-RSU.
If c-RSU and n-RSU are adjacent, that is, vehicles are moving in specified routes with fixed RSU allocation, the procedure can be simplified by constructing bidirectional tunnel directly between them (cancel the intervention of MA) to alleviate the traffic flow in MA as well as reduce handoff delay.
Vehicle c-RSU n-RSU
| | |
|---------------------| |
|c-RSU detects leaving| |
|---------------------| |
| |--------PBU------>|
| | |
| |===Bi-Dir Tunnel==|
| | |
| |<-------PBA-------|
| | |
| | |
|(--------RS with Mobility Info-------->)|
| [VMI] |
| |
|<--------RA with prefix1 (c-RSU)--------|
| |
|<--------RA with prefix2 (n-RSU)--------|
| |
Figure 6: Handoff of a Vehicle within Multiple Prefix Domains with DMM
Figure 6 shows the handoff of a vehicle within two prefix domains (as two multi-link subnets) with DMM [I-D.DMM-PMIPv6]. If c-RSU detects that the vehicle is going to leave its coverage and to enter the area of an adjacent RSU (n-RSU) belonging to a different prefix domain, it sends a PBU message to inform n-RSU that the vehicle will enter the coverage of n-RSU along with handoff context such as c-RSU's context information (e.g., c-RSU's link-local address and prefix called prefix1), and the vehicle's context information (e.g., the vehicle's global IP address and MAC address). After n-RSU receives the PBA message including the handoff context from c-RSU, it sets up a bi-directional tunnel with c-RSU, and generates RA messages with c-RSU's context information. That is, n-RSU pretends to be a router belonging to Subnet1. When the vehicle receives the RA from n-RSU, it can maintain its connection with its corresponding node (i.e., CN1). Note that n-RSU also sends RA messages with its domain prefix called prefix2. The vehicle configures another global IP address with prefix2, and can use it for the communication with neighboring vehicles under the coverage of n-RSU.
This document shares all the security issues of Vehicular ND [I-D.IPWAVE-VND], Proxy MIPv6 [RFC5213], and DMM [RFC7333][RFC7429][I-D.DMM-PMIPv6].
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. |
| [RFC3775] | Johnson, D., Perkins, C. and J. Arkko, "Mobility Support in IPv6", RFC 3775, June 2004. |
| [RFC4861] | Narten, T., Nordmark, E., Simpson, W. and H. Soliman, "Neighbor Discovery for IP Version 6 (IPv6)", RFC 4861, September 2007. |
| [RFC4862] | Thomson, S., Narten, T. and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC 4862, September 2007. |
| [RFC5213] | Gundavelli, S., Leung, K., Devarapalli, V. and K. Chowdhury, "Proxy Mobile IPv6", RFC 5213, August 2008. |
| [RFC7333] | Chan, H., Liu, D., Seite, P., Yokota, H. and J. Korhonen, "Requirements for Distributed Mobility Management", RFC 7333, August 2014. |
| [RFC7429] | Liu, D., Zuniga, JC., Seite, P., Chan, H. and CJ. Bernardos, "Distributed Mobility Management: Current Practices and Gap Analysis", RFC 7429, January 2015. |
This work was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2017R1D1A1B03035885).