**2. Related works**

Most objects in our surrounding are not equipped with microprocessors and hence cannot attach to a computer network. However, these objects can be equipped with passive, lowcost RFID tags either as tags integrated or adhesively stuck to the object and hereby provide a mean of communications. Dominikus et al. [14] has suggested a way to integrate passive RFID systems into the Internet of Things, by using readers that function as IPv6 routers. In their work, an IPv6 addressing scheme that map tag IDs to network addresses was defined. Furthermore, the mobility problem, which arises when tags physically moves around, was investigated and the use of Mobile IPv6 (MIPv6) to cope with tag mobility was suggested. In contrast to the work presented by Dominikus et al. [14], this chapter opens the discussion on the proper formatting of the IPv6 addressing by introducing cryptographic hashing techni‐ ques as well as the possibility of separating identity and location information when forming an IPv6 address. The use of hashing techniques to construct an IPv6 address from an EPC, as opposed by using a compressed EPC format [14], eases practical implementations and al‐ lows the use of the same mapping scheme for all EPC types.

An alternative approach is to provide the tags themselves with the IPv6 protocol stack, mak‐ ing them able to use IPv6 communication over the Internet whenever close to a reader. This requires several changes to the design of existing tags. In this case, the tags do all the work themselves and need a separate power source. A solution where the tags are modified to hold the IPv6 stack on them is discussed by Rahman et al. [4]. The tags EPC, which is its identity, would then be made into a part of the tags IPv6 address due to the design of the tags proposed. This makes these tags too expensive for integration into the Internet of Things since the price of the tags could easily exceed the value of the "things" themselves.

Barish et al. [13], describes a somewhat similar setup than the one proposed here. In their approach, a global address manager is used to keep track of tags. The basic idea is that an application sends the EPC to a global server along with the IP address that the tag has been associated with. When a corresponding node wants to communicate with the tagged object, it contacts the last known address. If the tag is in the field of the reader the connection is established and communication can begin. If the tag is not present at the location the request is redirected to the global address server that returns the tag's present address or just redi‐ rects the request to the correct address. In contrast to the proposed solution by Barish et al. [13], the approach described here does not include extra nodes in the network to construct network addresses but adds functionality to the RFID readers residing at the network edge.

Xu et al. [25] proposed a general address mapping scheme based on a proprietary protocol named General Identity Protocol (GIP). The scheme takes all existing RFID systems into ac‐ count, and allows heterogeneous RFID systems to interwork over the Internet. This is ac‐ complished by mapping RFID tag identifiers to IPv6 addresses, constructing a GIP message with details of the RFID systems in use, and finally encapsulating the message in IPv6 and routing the packet over the Internet. This chapter describes a solution that minimizes the need for control protocols.
