# Neighbor Session Solutions for Integrated Routing Protocols
## 4 Modeling Protocol Integration Solution Classes
### PISC 3--L3 Transport, Multiple Adjacencies
#### 4.1.1 Sending Part
other than four or six (we have not yet received a packet from the neighboring router), two frames are created, one with an IPv4 and one with an IPv6 packet. #### 4.2.2 Receiving Part

The receiving part of the model of the fourth PISC class had to be modified to apply the algorithm described in Section 4.1.1. The modified part is shown in Figure 3:5

The received frame is decapsulated by the Decapsulate L2 transition and then stored in the L3 Packet place. Subsequently, the IPv4 packets are processed by the Decapsulate IPv4 transition. If this is the first packet from the neighbor, the neighbor table is set to four with the neighbor type, and the neighbor's IP address is stored. If this is not the first packet from the neighbor and an IPv6 packet has already been received, the packet is dropped, and an empty routing packet with the Dropped flag is generated. The packet is finally stored in the Received place and is later processed by the Process RoutePacket transition. In the case of receiving an IPv6 packet first, the situation is the same. Only the Decapsulate IPv6 transition is used, which sets IPv6-specific values (type value in the neighbor table with the number six). The part of the model representing router B is created similarly as presented in Section 4.1.5. It is necessary to make a copy of the A part of the router and address changes. ### PISC1 and 2

We derive the model of the first PISC, just as in the case of the fourth class, from the complete model of the third class described in Section 4.1. The entire graphical representation of the created model representing the first class is shown in Figure S1, and the source file for the CPN Tools is available in Source S1. The model of the second PISC is derived from the full model of the first class, as it shares the most similarities with it. The entire graphical representation of the created model representing the first class is shown in Figure S2, and the source file for the CPN Tools is available in Source S2. ## 5 Verification of Created Models

As a first step of design verification, based on the analysis of colored Petri nets and the CPN Tools, we try to verify the model using state space computation. Unfortunately, we are able to compute only partial state space. Since even after further studying the literature and increasing the calculation time, we cannot detect the source of the partial calculation problem, we try to test the model in another way. We perform an interactive simulation of the created model by manually selecting from the active transitions those to be performed in the following order: from IPv4 part of router

Figure 3:6 PISC 4—Changes in the receiving part. A -> routing message encapsulation into a packet -> packet encapsulation into a frame -> sending through the network -> receiving a frame by neighbor B -> decapsulating the packet from the frame -> decapsulating the routing message -> processing the message -> sending an initial message to neighbor B and so on. This is performed until the routers have exchanged all the required messages, thus establishing adjacency and exchanging routing information. Thus, the process is similar to the one representing adjacency creation by the EIGRP routing protocol. The process proceeds as expected, so we successfully repeat it for the IPv6 net in-> reighborship. The interactive simulation of both IPv4 and IPv6 requires around 250 simulation steps, which is time consuming (the desired transition had to be selected 250 times). Since the interactive simulation turns out to be successful, we decide to continue exploring the possibilities of the simulation. As a next step, we try to perform an automatic simulation by setting the number of steps taken to 300, as we expect the simulation to end after 250 steps as in the case of the interactive simulation. However, despite the promising results of the interactive simulation, the automatic simulation does not finish, even after setting the number of steps to 10,000, similar to the case of the state space calculation.