# A Design for SDN-Based Identifier-Locator Separation Architecture on IoT Networks
## 3 Proposed SDN-Based Identifier-Locator Separation Architecture for IoT Networks
### Operations of ARs and OFSs  
The ARs are classified by three roles. The first role is a home AR (h_AR) for an MN. If an MN's EID is included in an AR's EID block, this AR becomes an h_AR of the MN. The h_AR has to manage the EID-LOC mapping information, and it has the responsibility to send the corresponding LOCs for the EID queries. Second, it manages a zone in which an MN is physically located. In this case, the role of the AR becomes the serving AR (s_AR). When the s_AR detects the attachment of a new MN, it assigns an LOC for the EID of this MN and maintains the mapping information. It also announces and updates this EID-LOC binding information to the MN's h_AR. If an MN with an EID tries to send a packet to a corresponding node (CN) having EID, the s_AR sends a query that gets the LOC of a CN to prepare IP routing. Once the s_AR obtains the MN and the CN's LOC, it sets the flow tables of its OFSs. The last role of an AR is to act as a neighbor EID controller (n_AR). The ARs between the h_AR and the s_AR are regarded as n_ARs. The n_ARs just forward received packets to the nearest zone of the destination according to the preconfigured flow table for EID routing. Generally, OFSs forward the received packets based on the matching rules of its flow table. If there is no matching from the received packet, the OFS sends this packet to its AR. Otherwise, it performs proper process according to the rule. In the proposed scheme, the OFS connected to an MN has a function that converts LOCs to EIDs for the destination address and vice versa. The physical paths of the local EID domain that overlap with the IP domain may not be optimized. The address field conversion of OFSs makes it possible to find the optimal paths over the IP domain and forwards the packet through the paths. The OFSs that are located between the OFSs connected to the MN and the CN are considered to be intermediate OFSs (iOFSs), and their basic role is forwarding the received packets to the OFSs of the nearest zone toward the destination. Figure 1 describes the system architecture of the proposed scheme and packet flows using IP and EID routing. In Figure 1, the local EID domain is divided into four EID zones. Each zone is managed by an AR. The local EID domain is overlaid over the IP domain. The packets are practically forwarded on the IP domain. An example of packet forwarding on the architecture is also described in Figure 1. When an MN sends a packet to a CN, the addresses of the MN and the CN may be EID addresses or normal IP addresses. Assume that the MN and the CN use EID addresses. Then, the source and destination address in the packets become \(EID_{MN}\) and \(EID_{CN}\), respectively. The packets from the MN are delivered from the OFS of the s_AR to the OFS of the h_AR. Since the s_AR's OFS does not know the CN's LOC, it sends the packets to the s_AR for EID routing. The EID routing path, however, differs from the physical path of the physical zone because each AR manages more than the two OFSs within the zone. As we mentioned before, ARs preconfigure the EID routing path in their OFSs, and the EID packets are able to be forwarded by using the preconfigured EID routing path on an IP domain, even if the packets with EIDs are unrouteable on an IP domain. Therefore, the packets from the OFSs of the s_AR are forwarded to the OFS of the CN's h_AR using EID routing via the iOFSs. Since the OFS of the CN's h_AR already knows the mapping between the EID and the LOC of the CN, it replaces the destination filed from \(EID_{CN}\) to \(LOC_{CN}\) immediately, and it sends the packet to the IP domain. When the OFS of the CN's s_AR receives the packet, it can convert \(LOC_{\text{CN}}\) to \(EID_{\text{CN}}\) and directly forward the packet to the CN. In the case that the OFS of the MN's s_AR already knows the CN's LOC, it can directly convert the CN's EID to the CN's LOC and forward the packets via an optimal path for the IP domain without EID routing.