# Anchor-Based Method for Inter-Domain Mobility Management in Software-Defined Networking
## 4 Proposed Methodology
### The RI-SDN Method
#### 4.2.2 Method Illustration  
We present two figures, Figures 3 and 4, which serve as the basic architecture to illustrate our method. Figure 3 represents the network with eight (08) domains in which a corresponding node \(CN\) is fixed and a mobile node \(MN\) moves. When the mobile node moves from one domain to another and connects to it (each domain is represented by a node that is actually the domain controller), the controller of that domain then detects a new registration and initiates the handover procedure for that mobile node. Figure 4 is a simplified representation, showing the links between each domain with their weights (representing bandwidth values) and the domain numbers to locate the mobile's movement. The service requires a minimum bandwidth of 400 Mbps (\(B_{s}=4\)). In the next two paragraphs, we illustrate the first stage and then the second stage of the RI-SDN method.  
First stage: Mobility Anchor Selection  
The adjacency matrix associated with our network is presented in Figure 5. Let us determine the mobility anchor.  
* The red line has the most 1 s, the set of most connected nodes \(SMC=\{5\}\). Thus, the domain associated with this line is the most connected and corresponds to node 5. The nodes between node 5 and the destination node are candidate nodes.
* \(SMC\) is a singleton. We check whether there are any nodes between this node and the destination node. On the adjacency matrix, nodes 6 and 7 are connected to both node 5 and node 8 (the destination node), as indicated by the black lines and the small green circles.  
Figure 2: Algorithm for route selection.  
* Therefore, the set of domains closest to the destination, SCD, is computed. \(SCD=\{6,7\}\). \(SCD\) is not a singleton, so we determine the set of most connected belonging to SCD, which is denoted by \(SMC(SCD)\).
* \(SMC(SCD)=\{6\}\). Thus, node 6 is taken as the anchor.  
Figure 6 shows the key concepts of our method (i.e., RI-SDN) and the route provided by our method from the architecture illustrated by Figure 4.  
Figure 4: Basic simplified architecture.  
Figure 5: Adjacency matrix.  
Figure 3: Basic architecture, from [19].  
Figure 6: Architecture with routes.  
Second stage:  
The anchor domain is strategically positioned, and this strongly influences the model in [10], where a metric involves the number of domains crossed by the data flow.  
* Determine \(RMA\): \(RMA=\{r_{1}=\{\)1-3;3-5;5-6;6-8\(\};r_{2}=\{\)1-2;2-5;5-6;6-8\(\};r_{3}=\{\)1-2;2-4;4-6;6-8\(\};r_{4}=\{\)1-2;2-4;4-5;5-6;6-8\(\}\}\)
* \(RMA\) is not empty. So, for each route \(r_{k}\) of \(RMA\), \(B_{k}\) is computed as follows: \(B_{1}=\) 4, \(B_{2}=\) 4, \(B_{3}=\) 1, \(B_{4}=\) 4
* Compare \(B_{k}\) and \(B_{s}\): \(B_{1}\geq B_{s}\), \(B_{2}\geq\) 4, \(B_{3}<B_{s}\), \(B_{4}\geq B_{s}\), then \(RMA(Inf)=\{B_{3}\}\) and \(RMA(Sup)=\{B_{1},B_{2},B_{4}\}\)
* Calculation of \(M_{k}\) metrics:
* For \(r_{1}\) we have \(M_{1}=MD_{1}+1/B_{1}\) \(M_{1}=3+1/4=3,25\)
* For \(r_{2}\) we have \(M_{2}=MD_{2}+1/B_{2}\) \(M_{2}=3+1/4=3,25\)
* For \(r_{4}\) we have \(M_{4}=MD_{4}+1/B_{4}\) \(M_{4}=4+1/4=4,25\)
* Determine \(SRK\): \(SRK=\{r_{1};r_{2}\}\)
* Sum of bandwidths for each \(r_{k}\in SRK\): For \(r_{1}\), this sum is equal to \(5+5+4+4=18\); For \(r_{2}\), this sum is equal to \(5+4+4+4=17\); The result is that \(r_{2}\) is the route that will be taken.