IPv6 mapping to non-IP protocols
draft-rizzo-6lo-6legacy-00

Abstract

IPv6 is an important enabler of the Internet of Things, since it provides an addressing space large enough to encompass a vast and ubiquitous set of sensors and devices, allowing them to interconnect and interact seamlessly. Many of those devices presently are based on networking technologies other than IP. In order to include them into an IPv6 based Internet of Things, a mechanism for assigning an IPv6 address to each of them is required.

The only existing proposal for a standard way of assigning an IPv6 address to devices which do not support IPv6 or IPv4, is very generic, it leaves many problems unsolved and it is nowadays inadequate to cope with the new scenarios opened by the Internet of Things. This document defines a mechanism, 6TONon-IP, for assigning automatically an IPv6 address to devices which do not support IPv6 or IPv4, in a way which minimizes the chances of address conflicts, and of frequent configuration changes due to instability of connection among devices. Such a mapping mechanism enables stateless autoconfiguration for legacy technology devices, allowing them to to interconnect through the Internet and to fully integrate into a world wide scale IPv6 IoT.

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Table of Contents

• 1. Terminology
• 2. Introduction
• 3. Reference System
• 4. Issues addressed through the 6TONon-IP mapping mechanism
• 5. 6TONon-IP Mapping Method
• 6. Examples
• 6.1. Example 1 - EIB/Konnex
• 6.2. Example 2 - RFID
• 7. IANA Considerations
• 8. Further considerations
• 9. Acknowledgements
• 10. Normative References
• Authors' Addresses

1. Terminology

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 [RFC2119].

2. Introduction

The Future Internet and IPv6 protocol present a new generation of capabilities and access to the network, which will extend the Internet seamlessly to personal devices, smart phones and sensors, enabling the Internet of Things (IoT). Current sensors and their application environments consist of a vast group of technologies which lack efficient interoperability among them. Some associations of manufactures have been formed to build a common technological framework in specific application domains, e.g. Konnex (KNX) for building automation, ZigBee with an independent Alliance (ZigBee Alliance), and protocols such as X10 and CAN. These protocols are not interoperable. Moreover, most of these technologies were designed in a context of small and local networks, with limited capabilities, so that they were not conceived for integration within the Internet. For instance, several years ago when X10 was defined, only a small number of sensors would be placed in the same building or a single control area. The same applied for EIB/KNX, which was one of the first technologies to offer an extended deployment of sensors in home and building automation. Nowadays, sensors are found almost everywhere. Indeed their number will increase exponentially in a short period of time with the definition of the smart grid, of smart cities, and the demand to connect every device to the Internet for full connectivity and interoperability via technologies such as ZigBee-IP, 6LoWPAN, and GLoWBAL IPv6. For those reasons, many designers of the Internet of Things are considering a move towards a common access and communications framework based on IPv6. Such a move would affect the addressing of the devices, since a common addressing at the device level is mandatory, in order to implement true Machine to Machine (M2M) communications without Portal Servers, or gateways. In order to integrate such legacy technologies within the Internet of Things, it is necessary to define an IPv6 mapping for the native addressing of the devices. Indeed, as a migration strategy, it would be desirable to have a mechanism to integrate them into the IoT. We propose here a mechanism for the users and devices to map the different addressing spaces to a common IPv6 one. This would make it possible for every device from each technology to operate through a common framework based on IPv6 and protocols over IPv6 such as RESTFul WebServices and Constrained Application Protocol (CoAP). For each technology, the proposed mechanism maps technology-specific features to a set of fields defined within the IPv6 address. This allows the location and identification of the devices in a multi-protocol card, or in any gateway or Portal Server.

3. Reference System

In this section we describe a reference system where the IPv6 mapping is used. Such a system includes:

1. A set of networks running non-IPv6-compatible technologies, each with one or more hosts connected. Such networks generally use different OSI layer 3 protocols, or they may adopt a technology which does not have any layer 3 protocol.
2. A proxy, which hosts the IPv6 mapping functionality. Such device is typically connected to each of the legacy protocols networks, and it accesses the Internet via the IPv6 protocol. Such IPv6 addressing proxy performs all the necessary conversions and adaptations between IPv6 and the (local) networking protocol of the legacy technologies, in a way which depends on the specific legacy technology considered. This proxy makes use of the IPv6 mapping mechanism in order to transforms the native addressing to IPv6 Host ID and vice versa in a way that depends on the legacy technology.

Though in what follows we will describe the proposed mapping with reference to such a system, the main ideas behind it are more general, and they apply to settings others than the one of reference presented here.

4. Issues addressed through the 6TONon-IP mapping mechanism

In this section we highlight the main open issues regarding assignment of IPv6 addresses to devices which do not support IPv6 or IPv4, and we describe a set of desirable properties for a mechanism for automatic assignment of IPv6 addresses to such devices, which we name henceforth 6TONon-IP. In Appendix A of RFC 4291, a method is described for creating modified EUI-64 format Interface Identifiers out of links or nodes with IEEE EUI-64 Identifiers, or with IEEE 802 48-bit MACs. Moreover, for technologies having other link layer interface identifier, some possible mapping methods are sketched, leaving for each legacy protocol the possibility to define its own mapping method.

In the present document, we propose a mapping mechanism which enables stateless address autoconfiguration for legacy technologies, and which exploits some protocol specific identifier such as link layer interface identifiers, and the like. The proposed mapping mechanism addresses the following issues:

1. Protocol identification: For the legacy protocols to which the mapping described in RFC 4291 does not apply, a mechanism is needed to map an IPv6 address to the right legacy protocol. This feature is necessary in case of devices which operate as proxy for more than one legacy technology at the same time.
2. Inter protocol aliasing: Without a mechanism for identifying the legacy protocol from the host part of the IPv6 address, address conflicts are possible among devices belonging to different legacy protocols. For instance, this may happen when the link layer interface identifier is the same for two devices belonging to different technologies. As several legacy technologies are characterized by a small addressing space, address conflicts are not so unlikely.
3. Conflicts between IPv6 mapped legacy technology addresses and addresses derived from (modified or not) EUI-64 format interface identifiers.
4. Intra-protocol aliasing: As several legacy technologies are characterized by a small addressing space, it is not unlikely to have two legacy devices, mapped to IPv6 addresses with the same network ID (for instance, in the case in which they belong to two separate networks of the same technology, both connected to a same proxy), and with a same interface identifier, and mapping therefore to a same IPv6 address.

Moreover, the following is a list of desirable properties for a 6TONon-IP mapping:

1. Consistency: A host should get the same IPv6 address every time it connects to a same legacy network, assuming that the configuration of all the other devices in that network remains unchanged. This allows avoiding to advertise a new address every time the host reconnects. This feature might be particularly important for devices which are not always "on", or which are not permanently connected.
2. Local Uniqueness: For devices which have an IPv6 address with a same network part, the host part should be unique for each host. This property allows avoiding address conflicts.
3. Uniqueness within the whole Internet: Coherently with the IoT vision, the host part of an IPv6 address associated to a host should be unique within the whole Internet.

Depending on the specific legacy protocol, there might be protocol specific limitations to the satisfaction of these properties. In particular, for those protocols which do not have an interface identifier which is unique, properties 1) and 2) cannot be fully satisfied. Indeed, no mapping can solve address conflicts which take place inside a legacy protocol network. When legacy protocols have a interface identifier which is unique, this can be used to produce a unique host part of an IPv6 address, and its uniqueness would guarantee the satisfaction of properties 1), 2) and 3).

5. 6TONon-IP Mapping Method

In this section we describe the proposed strategy for forming IPv6 addresses from legacy protocol information, and the address format that derives from it. We assume that (one or more) 64 bits Network ID prefixes are given to the mapping function, which therefore computes the 64 bits of the Host ID part of the address (IPv6 interface identifier), in order to form a full IPv6 address.

The input of the proposed mapping function consists in the interface identifier of the legacy protocol.

In the proposed mapping method, the resulting Host ID part (IPv6 interface identifier) is composed by six fields, as shown in Figure 1:

• A Technology ID field (6 bits), containing a code which identifies the specific legacy protocol.
• U/L bit (1 bit), in order to keep compatibility with the mapping EUI-64 [RFC4291]. The U/L bit is the seventh bit of the first byte and is used to determine whether the address is universally or locally administered. This bit is set to "0", in order to indicate local scope, analogously to what proposed in [RFC4291]. This choice prevents address conflicts with IPv6 interface identifier generated from IEEE EUI-64 identifiers or IEEE 48-bit MAC identifiers.
• I/G bit (1 bit). The I/G bit is not used. It will be used with value "0" by default.
• A Reserved field (8 bits). This field can be used in the future for the identification of different interfaces for a same technology (in the same subnetwork).
• Technology Mapping field (32 bits), which maps the interface identifier of the legacy protocol. For those protocols for which the IID is not larger than 32 bits, this field contains the 32 bits of the IID. For IID which are larger than 32 bits, a hashing function is used instead of direct mapping. In particular, some hashing algorithms such as CRC-32 are suggested. Hashing satisfies the requirements of consistency and uniqueness within a subnet with a very high probability, which depends on the hashing algorithm used. This field is split into two parts, one of 8 bits, and another of 24 bits.
• The fourth and fifth bytes are both set to to "0x00", in order not to conflict with EUI-64 interface identifiers.

The resulting format of the Host ID part of the IPv6 address obtained from the mapping is indicated in Figure 1.

		+--------+-------+-------+---------+--------+----------+---------+
		| Tech.  |  U/L  |  I/G  | Reserved| Tech.  |  EUI-64  | Tech.   |
		|  ID    |  "0"  |  "0"  |         | Mapping| "0x0000" | Mapping |
		|        |       |       |         |  MSB   |          |   LSBs  |
		|(6 bits)|(1 bit)|(1 bit)| (8 bits)|(8 bits)| (16 bits)|(24 bits)|
		+--------+-------+-------+---------+--------+----------+---------+
				
    Figure 1: general format of the host ID part for legacy protocols
         

6. Examples

In this section we illustrate the proposed mapping method by applying it on some examples.

6.1. Example 1 - EIB/Konnex

We assume the legacy protocol is EIB/Konnex. This device has two kind of addresses: On the one hand, a logical address for management of group operations, and on the other hand, an individual address for identification of the device in the topology.

The mapping will be focused for the individual address. This includes an Area ID (4 bits), Line ID (8 bits), and Device ID (8 Bits). An example, is the value 0x1/0x01/0x01 for a sensor connected in the Area ID 0x1, Line ID 0x01, and Device ID 0x01.

We apply a hash (CRC-32) to the sequence 0x10101. The result is 0xDEA258A5.

Let us assume that EIB/Konnex Technology ID is "0". Thereby, the IPv6 interface identifier is "0000:DE00:00A2:58A5", considering the documentation network 2001:db8::/32. The final IPv6 address for the legacy device is "2001:db8::DE00:A2:58A5".

The address is presented in the Figure 2.

    +--------+-------+-------+---------+--------+----------+---------+
    | Tech.  |  U/L  |  I/G  | Reserved| Mapping|  EUI-64  | Mapping |
    |  ID    |  "0"  |  "0"  |         |  MSB   | "0x0000" |   LSBs  |
    |(6 bits)|(1 bit)|(1 bit)| (8 bits)|(8 bits)| (16 bits)|(24 bits)|
    |  0x00  |   0   |   0   |   0x00  |  0xDE  |  0x0000  | 0xA258A5|
    +--------+-------+-------+---------+--------+----------+---------+
				
      Figure 2: EIB/Konnex example: the IPv6 interface identifier.
         

6.2. Example 2 - RFID

We assume the legacy protocol is RFID. Each RFID device is identified by its Electronic Product Code (EPC), whose length may vary from 96 to 256 bits. Let us assume to have an RFID device whose EPC is given by 01.23F3D00.8666A3.000000A05 (12 bytes). Let us assume that EIB/Konnex Technology ID is "1".

We apply a hash (CRC-32) to the sequence 0x0123F3D008666A3000000A05. The result is 0xA93AFFA0.

Thereby, the IPv6 interface identifier is "0400:A900:003A:FFA0", considering the documentation network 2001:db8::/32. The final IPv6 address for the RFID Tag is "2001:db8::400:A900:3A:FFA0".

The address is presented in the Figure 2.

    +--------+-------+-------+---------+--------+----------+---------+
    | Tech.  |  U/L  |  I/G  | Reserved| Mapping|  EUI-64  | Mapping |
    |  ID    |  "0"  |  "0"  |         |  MSB   | "0x0000" |   LSBs  |
    |(6 bits)|(1 bit)|(1 bit)| (8 bits)|(8 bits)| (16 bits)|(24 bits)|
    | 0x04   |   0   |   0   |   0x00  |  0xA9  |  0x0000  | 0x3AFFA0|
    +--------+-------+-------+---------+--------+----------+---------+
				
      Figure 3: RFID example: the IPv6 interface identifier.
         

7. IANA Considerations

Not yet defined.

8. Further considerations

Not yet defined.

9. Acknowledgements

The authors wish to acknowledge the following for their review and constructive criticism of this proposal: Robert Cragie. Thanks to the IoT6 European Project (STREP) of the 7th Framework Program (Grant 288445), and the colleagues who have collaborated in this work. In particular, Antonio Skarmeta from the University of Murcia, Peter Kirstein and Socrates Varakliotis from the University Colleague London, and Sebastien Ziegler from Mandat International.

10. Normative References

Authors' Addresses