## 3 Traffic Model
* UE 2 sends a call disengagement request (SIP BYE), which is forwarded to UE 1 and causes resource release in access and core of domains 2 and 1 (messages 69-77). * Resource release is confirmed (messages 78-82). Figure 1: Structure of the multidomain IMS/NGN network with an MPLS-based transport stratum. It is very important that, according to the abovementioned quota-based approach used in MPLS core networks, not all resource control operations performed by RACF C1 and RACF C2 involve communication with MPLS LERs (\"MPLS core 1\" and \"MPLS core 2\" blocks; Figure 2) for changes of LSP bandwidth. Blue arrows with dashed lines are used in Figure 2 to illustrate this optional communication between RACF units and controlled MPLS networks. The aim of our research is to evaluate selected CPP parameters in a multidomain IMS/NGN network with an MPLS-based transport stratum, which is depicted in Figure 1. For this reason, an analytical traffic model was developed [11] which uses definable queuing models (M/M/1 or M/G/1; Figure 3) to reflect the operation of CSCF servers and RACF C1 and RACF C2 units as well as all links between network elements. The choice of queuing models will be commented on later in this section. Modeling of the structure in Figure 1 comes down to the network of queuing systems and selected elements represented by random variables (RACF A1, RACF A2, SUP-FE 1/SAA-FE 1, SUP-FE 2/SAA-FE 2 and MPLS domains; details are provided later). Unfortunately, this network does not meet the assumptions of [PERSON]'s theorem, so it cannot be used to determine the probabilities of the state distributions of this network. Since we are interested in the mean values of delays (\(E(CSD)\) and \(E(CDD)\)), these distributions are not necessary. It is assumed in our model that message processing times for CSCF servers, RACF C1 and RACF C2 depend on the message type and are different for each network element. For links, message processing times (message transmission times) depend on the message lengths and link bandwidths. Random variables are used to model the response times for the remaining network elements presented in Figure 1: RACF A1, RACF A2, SUP-FE 1/SAA-FE 1 and SUP-FE 2/SAA-FE 2. For the RACF A1 and RACF A2 units, the response times include the time necessary to configure the controlled access networks. The response times of particular MPLS domains (\"MPLS core 1\" and \"MPLS core 2\"; Figure 1) are also taken into account as random variables in the described analytical model. They include the time of processing the request by the LER beginning the LSP and changing the LSP bandwidth, which requires interaction with all MPLS routers on the path. Thus, the influence of the structure and operation of MPLS domains on the analyzed output parameters is reflected by these random variables. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Name**} & \multirow{2}{*}{**Type of Call**} & **Originating** & **Same Access** & **Necessary** & \multirow{2}{*}{**Successful**} & \multirow{2}{*}{**Remarks**} \\  & & **Domain** & **Areas** & **Resources** & & \\ \hline b1 & Intra-operator & 1 & Yes & Access 1 & Yes & \\ \hline b2 & Intra-operator & 2 & Yes & Access 2 & Yes & \\ \hline c1 & Intra-operator & 1 & Yes & Access 1 & No & \\ \hline c2 & Intra-operator & 2 & Yes & Access 2 & No & \\ \hline d1 & Intra-operator & 1 & No & Access 1, core 1 & Yes & \\ \hline d2 & Intra-operator & 2 & No & Access 2, core 2 & Yes & \\ \hline e1 & Intra-operator & 1 & No & Access 1, core 1 & No & \\ \hline e2 & Intra-operator & 2 & No & Access 2, core 2 & No & \\ \hline f1 & Inter-operator & 1 & No & All networks & Yes & \\ \hline f2 & Inter-operator & 2 & No & All networks & Yes & \\ \hline g1 & Inter-operator & 1 & No & All networks & No & Variant 1 \\ \hline g2 & Inter-operator & 2 & No & All networks & No & Variant 1 \\ \hline h1 & Inter-operator & 1 & No & All networks & No & Variant 2 \\ \hline h2 & Inter-operator & 2 & No & All networks & No & Variant 2 \\ \hline \hline \end{tabular}
\end{table}