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Versions: 00 01 02 03                                                   
IPWAVE Working Group                                              Z. Yan
Internet-Draft                                                     CNNIC
Intended status: Standards Track                                  J. Lee
Expires: November 11, 2021                             Sejong University
                                                                J. Jeong
                                                 Sungkyunkwan University
                                                                 Y. Park
                                            University of Malaysia Sabah
                                                             H. Nakazato
                                                       Waseda University
                                                            May 10, 2021

           Data Aggregation in IPv6-based Vehicular Networks


   Considering the large-scale but small-sized information exchange in
   the vehicular information network, this draft document aims at
   outlining the requirements to support the data aggregation in
   vehicular networks based on the concept of Information-centric
   networking (ICN), in order to make the information retrieval and
   dissemination in an efficient way.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 11, 2021.

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Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Data naming . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Routing . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Aggregation and Segregation . . . . . . . . . . . . . . . . .   4
   5.  Caching . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Other Issues  . . . . . . . . . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   A vehicular information network aims at implementing a myriad of
   applications related to vehicles, traffic information, drivers,
   passengers and pedestrians.  Then a flexible data integration and
   segregation architecture in Intelligent Transportation Systems (ITS)
   should be designed to support the exchange of a huge number of
   heterogeneous information objects in an efficient and scalable

   The main case for data integration we discuss in this draft is:
   multiple requested information objects originated from different
   sources are shared in some or all hops on the transmission paths.

   This document outlines the general requirements for data integration
   from several key aspects described in the following sections.  But
   this draft does not specify the requirements in special communication
   cases, such as Vehicle-to-Everything (V2X), Infrastructure-to-
   Everything (I2X), and Vehicle-to-Infrastructure-to-Vehicle (V2I2V)
   communications.  The particular requirements under these special
   cases will be analyzed in the future.

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2.  Data naming

   Generally, location and data type are potentially critical indexes
   for data retrieval in ITS.  Also, for configuration, management, and
   maintenance, devices may need to be accessed directly by a device-
   specific identifier.  Therefore, a naming scheme needs to incorporate
   location, data type and device information, in order to be scalable
   to support trillions of information objects.

   o  Location-based: A critical organizing factor for vehicular sensing
      data, which is to be widely shared and fused, is the location to
      which it applies.

   o  Device-based: In some cases, the data produced by a specialized
      vehicle or infrastructure device may be requested.

   o  Type-based: Another critical element for naming is the type of
      data.  Namespaces need also incorporate data type designators,
      such as speed, emission, trajectory and so on.

   Then to better support the data aggregation, the name included in the
   data request message can be designed as:

   /Producer1:Producer2:...ProducerX/ Location1:Location2:...LocationY/
   Type1:Type2:...TypeZ/ end/

   [The format of the content name used in this document only identifies
   the logic of the name structure.]

   The parsing logic is: the data objects with Type (1,2,...,Z) created
   from Location (1,2,...,Y) by Producer(1,2,...,X) are requested.  A
   producer identifies the device here.

   For example, if a vehicle wants to get the traffic information in
   Street-1, Street-2, and Street-3 (without specifying the data
   producer/device), a name of the data may be:


   In most cases, the requester only cares what information it wants,
   but does not exactly know the information source.  In other words, it
   is possible that the requester can not specify the destination
   address of the request message.  Thus a service discovery scheme,
   which may make use of the information in the data name as the index,
   can be designed in ITS.

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3.  Routing

   In IP-based vehicular networks, the routing table and routing scope
   should be adaptively designed based on the TCP/IP stack.

   (1) Routing Table

   To support different kinds of ITS communication and different
   aggregation policies, in the routing table of the router in the RSU
   and the edge router in the vehicle, there are at least two types of
   entries to be maintained: geo-location based and IP based routing
   entries.  The former one is based on the geographical location
   information of the routers, which is established either through the
   coordinate information exchanged between routers or through
   centralized configuration.  On the other hand, the latter one is
   established based on the normal routing protocols in the TCP/IP

   2) Routing Scope

   As in the IP network, the routing scopes also mainly include
   multicast and unicast for different communication cases.  Then
   different routers may be configured for different multicast groups.
   This document mainly considers IPv6 scenario.  One router may also
   belong to multiple different multicast groups.  Although the data
   aggregation acts like the multicast to converge the communications,
   it is the packet-level optimization and can be applied to both
   unicast and multicast cases.

4.  Aggregation and Segregation

   Based on the naming labels and the routing information, the router
   (especially a router in an RSU) will decide whether the request
   packet should be split over its multiple outgoing network interfaces
   or not.  Specially, the router should determine whether the outgoing
   network interfaces for the multiple data elements the same or not.
   If so, direct forwarding is made based on the matched entry in the
   routing table.  Otherwise, the router has to split the original
   request packet into multiple new request packets according to their
   different outgoing network interfaces and send them to different
   next-hop routers according to the newly generated names.  Similarly,
   if the data is sent back through the reverse path, they can be

   As illustrated above, based on the routing table, the router decides
   whether the request message should be split over their related
   outgoing network interfaces or not.  However, some conditions (e.g.,
   traffic jam or traffic accident information) should be learned by the

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   traffic administrator as soon as the vehicular information network
   changes quickly and quite frequently.  As a result, a timer value
   used for the data aggregation should be carefully set.  Different
   policies for setting the timer value can be used and such policies
   need to be indicated by the upper level aggregator (e.g., previous-
   hop router) in the request message.  Generally, some of the request
   messages should be handled on a first-in-first-out basis, for
   example, in the emergency case.  On the other hand, some of the
   request messages can only be processed until all the required
   information is collected, for example, in the case where the overall
   traffic condition information is required.  The upper level
   aggregator can set up the timer value to the lower level ones (e.g.,
   the next-hop router) in the request message.  But the protocol to
   support this notification and policy decision is beyond the scope of
   this document.

   Another key element to support the aggregation and segregation
   procedure is a pending table that maintains the original data name
   and the newly extracted data names.  This table is mainly maintained
   by a branching node on the communication path, which conducts the
   segregation operation.  In this way, the reverse operation (i.e.,
   data aggregation) can be executed.

    | V3|-----\
    +---+     |
          +-----+ //Street-3/traffic/end/
          |RSU3 |------------------\
          +-----+                  |   //Street-3:Street-4/traffic/end/
                                +-----+                 +-----+
                                |RSU2 |-----------------|RSU1 |
                                +-----+                 +-----+
          +-----+                  |                       |
          |RSU4 |------------------/                       |
          +-----+ //Street-4/traffic/end/                  |
              |                                          +---+
    +---+     |                                          |V1 |
    |V4 |-----/                                          +---+
    +---+                       //Street-3:Street-4/traffic/end/

          Figure 1: Operation of the Aggregation and Segregation

   An example of the aggregation and segregation is shown in Figure 1.
   In this figure, Vehicle-1(V1), Vehicle-3(V3), and Vehicle-4(V4)
   connect to the Internet through RSU1, RSU3, and RSU4, respectively.
   When V1 wants to know the current traffic states of two blocks served

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   by RSU3 and RSU4 to select a better path between them, it sends out
   the data request message with the data name //Street-3:Street-
   4/traffic/end/. When RSU1 receives this request message, it directly
   sends the message to RSU2 because the next hop to request all the
   data in this message comes from RSU2.  But when RSU2 receives this
   message, it will recognize that the data should be requested from two
   different outgoing interfaces toward RSU3 and RSU4, respectively.
   Then two new names are generated through the information extraction
   from the original name.  Specially, the data request for the new name
   //Street-3/traffic/end/ is sent to RSU3 and the data request for the
   new name //Street-4/traffic/end/ is sent to RSU4.

   After the retrieval of the data corresponding to the two data request
   messages, the aggregation is conducted through the reverse path based
   on the recorded states.

5.  Caching

   Caching is necessary to reduce unnecessary data transmissions, so it
   can improve the scalability in ITS.  When the router receives a data
   request, it will check its cache firstly.  Based on the cache hit
   result, the request may be segregated when it is possible.
   Generally, two different cache tables should be maintained:

   o  Time-sensitive Data Cache: Some data in the ITS is very time-
      sensitive, such as traffic jam condition.  Thus, the timer should
      be strictly inherited from the related response message for the
      particular data.

   o  Time-insensitive Data Cache: for other time-insensitive data, such
      as the geo-map information, a default timer with a long lifetime
      should be used to serve the following requests efficiently.

6.  Other Issues


7.  Security Considerations


8.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

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Authors' Addresses

   Zhiwei Yan
   No.4 South 4th Street, Zhongguancun
   Beijing  100190

   EMail: yan@cnnic.cn

   Jong-Hyouk Lee
   Sejong University
   209, Neungdong-ro, Gwangjin-gu
   Seoul  05006
   Republic of Korea

   EMail: jonghyouk@sejong.ac.kr

   Jaehoon Paul Jeong
   Department of Computer Science and Engineering
   Sungkyunkwan University
   2066 Seobu-Ro, Jangan-Gu
   Suwon, Gyeonggi-Do
   Republic of Korea

   EMail: pauljeong@skku.edu

   Yong-Jin Park
   University of Malaysia Sabah
   88400, Kota Kinabalu

   EMail: yjpark@ums.edu.my

   Hidenori Nakazato
   Waseda University

   EMail: nakazato@waseda.jp

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