**6. Strategies for interworking IPv6 with RFID tags**

In this Section we will discuss different methods of mapping between an RFID namespace and an Internet namespace.

#### **6.1. Address mappings**

**Waiting for TagSwipe**

Expiration time expired

124 Radio Frequency Identification from System to Applications

Converted to hexadecimal 4 groups of 4 hex.

Tag identity (Example with EM4100

Binary ID representation with left-

Network prefix of RFID reader

Unicast IPv6 address associated

tag)

zero-padding

(example)

with the tag

interfaces.

Program started

**Figure 7.** State machine for the virtual interface resulting from a TagSwipe event at the reader.

5 decimal numbers

4 groups of 4 hex.

8 groups of 4 hex.

The application has no visual interface and all configurations must be done in software. For example, it is possible to use more than one virtual interface to represent the tags online. These interfaces need to be preinstalled, as already mentioned, and some parameters in the application need to be configured. Hereafter, it is possible to make use of at least 5 virtual

Although focus is on the assignment of IPv6 unicast addresses, tags can also be assigned to become member of multicast groups thereby facilitating one-to-many communication. As an example an application may want to address all tags at a particular reader. Likewise, read‐ ers can become members of multicast groups hereby enabling communication to all readers

(40 bits)

digits

digits

digits

**Table 1.** Example of IPv6 network address construction from on EM4100 tag ID.

**Interface alive while Expiration time > 0**

127 0 58 207 19

0000 007f 003a cf13

2001:16d8:dd92:aaaa::/64

2001:16d8:dd92:aaaa::007f:003a:cf13/128

64 bits 0000 0000 0000 0000 0000 0000 0111 1111 0000 0000 0011 1010 1100 1111 0001 0011

TagSwipe event

> TagReswipe event. Expiration time reset

The most simple approach to find IPv6 addresses for tags is the mapping of the tag ID to an IPv6 address, i.e., the bits from the ID are used to form the IP address [14]. As different pas‐ sive RFID standards exist there is no common ID structure for tags. Even within standards, there are different types of IDs with different structures. This means, that a general concept to map tag IDs to IPv6 addresses will not work.

Table 2 shows a list of some commonly encountered passive tags and their ID formats.


**Table 2.** Common passive RFID tag and their characteristics.

An EPC with the length of 64 bits maps well in the IPv6 address format and can result in globally unique addresses. With longer EPCs it is impossible to map the EPC directly into the IPv6 address space and here specialized functions are needed. One solution would be to simply hash the longer EPC's into a length of 64 bits and then use the direct mapping meth‐ od again. The hashing technique used to derive identifiers was described in Section 3.4, when the CGA namespace was introduced. Another method would be to identify if there are some bits in the longer EPC's that can be removed without affecting the uniqueness property of the tags.

**7. Mobility considerations**

One of the largest challenges for a dynamic, networked system lies within the mobility sup‐ port of the network. In the case described here, we consider a system of fixed readers that are connected in a common network infrastructure. Mobility arises when tags are moved be‐ tween readers. Readers will be wired or wireless and they will have different communica‐ tion ranges according to their MAC technology. Moreover, they will forward the read tag

Integrating RFID with IP Host Identities http://dx.doi.org/10.5772/53525 127

When a tag moves from one reader to another, the network prefix will change but the host suffix/interface ID will still match the tag's EPC. The tag will in effect change its network address every time it passes a new reader. Hence, the challenge is to effectively keep track of

There are basically two distinct ways to solve the mobility problem. One is a centralized ap‐ proach, such as mobile IPv6 [30], where a central server, i.e., the home agent, is used to keep track of the mobile hosts that move around in the world. The mobile IPv6 architecture relies on the concept of a home agent and a care-of address. The method is based on some soft‐ ware on the network layer that can send messages to the home agent making sure that the home agent is holding an updated address list at all times. Initially, traffic destined to the mobile host is routed to the home network and subsequently tunneled to the foreign net‐ work that the host is visiting. Fortunately, IPv6 supports mechanisms to circumvent the tri‐

Dominikus et al. [14], proposed to use mobile IPv6 to handle the mobility of IPv6-enabled tags. In their approach, the care-of address refers to the subnet of the RFID reader, where the tag is currently present. Whilst the care-of address is a globally unique address assigned to the host, i.e., the tag visiting a foreign network, the home agent address is specific to the en‐

Alternatively, mobility support can be obtained in a more distributed way by separating lo‐ cation and identity information. This can be achieved by using the HIP approach [22]. In this approach, there is a need to compute the routable IPv6 address from the given non-routable

HIP allows consenting hosts to securely establish and maintain shared IP-layer state, allow‐ ing separation of the identifier and locator roles of IP addresses, thereby enabling continuity of communications across IP address changes. A consequence of such a decoupling is that

Metcalfe's law states that the value of a telecommunications network is proportional to the square of the number of connected users of the system. When the law is applied to a net‐

new solutions to network-layer mobility and host multi-homing are possible [22].

IDs to the server through the common network infrastructure.

tags when the address changes this rapidly.

angular routing problem that arises in this setup [30].

terprise using the issued tags.

HIT the host has been given.

**8. Conclusions**

A key benefit of the proposed solution is that there is no need to change the design of exist‐ ing RFID technology with its EPC namespace conventions. The application can be installed on a computer connected to the reader, and then all objects with RFID tags that pass this reader will put the objects online and thereby giving them the ability to communicate over the Internet as long as the tag is within range of a reader.


**Table 3.** Overview of strategies for mapping Tag ID codes to IPv6 network addresses.

Table 3 outlines the different strategies for mapping of tag IDs to IPv6 addresses. Essential‐ ly, these divide into methods that work with tags of 64-bit identification or less and tags that use more that 64-bit for identification.
