## 3 Results and Discussion  
### Development in the Configuration of a Real IP Network Based on Asterisk PBX  
The most popular solution that provides a huge range of additional features and capabilities is the Asterisk IP PBX software. It is a free software package capable of acting as an IP telephony server based on popular protocols such as SIP, call center functions, and many other functions. The project is open and is constantly under development, during which the list of features of this IP PBX is expanding. Asterisk allows any computer with an operating system of the Linux family installed on it to be used as a server. The scheme of the real network on the selected servers is shown in Figure 1.  
In Figure 1, 100, 200, 300 and 400 phones connected to the asterisk server which in Almaty (hosting in Germany) have the IP address 164.92.169.120, and in Astana (hosting in the Netherlands) the IP address 142.93.229.238. The networks were combined with the help of an Internet operator for a certain payment for the direction of information transfer in both directions. To install IP PBX Asterisk, we use a repository consisting of distributions and program archives, choosing from it a modern version that suits us; there are distributions that can satisfy the needs of everyone who accesses program archives. In our case, the Ubuntu distribution is selected. Let us determine the necessary distributions of Asterisk 16.16.1 to install them with the \"apt search asterisk\" command, as shown in Figure 3.  
Figure 2: The TLS Handshake Protocol. After the successful installation of Asterisk, we can check the status of Asterisk with the following command: system ctl status asterisk (Figure 4). The version can also be checked by directly accessing Asterisk with the v (version) key, as shown in Figure 5.  
Figure 4: Running Asterisk status check. Figure 3: Checking packages in the repository. After \"ecnfyjdrb llcnhb,enbdf\" it is proposed to copy the default settings that appear when installing the package. This is necessary in order to return to the original state in each case. To do this, we run the \"cp\" (copy) command and specify two arguments: the path to the original file and the path to the copy of the file (Figure 6). Now, to exchange data and connect remote users, we need to open some ports that work with Asterisk closed. Ports 5060 and 5061 are needed for the SIP protocol, 10,000-20,000 for RTP, port 4569 for IAX, and 5038 AMI, as shown in Figure 7.  
Next, we edit the <<sip.conf>> file on the remote servers. This file is responsible for registration on other Asterisk servers; telephone numbers are also registered here. On server 1 (conditionally designated \"Almaty\"), telephone numbers from 100 to 200 are created, and on the second server (\"Astana\" server), those from 300 to 400 are created. This is necessary for the conditional separation of numbers, that is, for context. For example, when calling 302, we know that we are referring to the \"Astana\" server, as shown in Figure 8.  
To connect to another server, we need to add a new peer. In Figure 9, this is the \"Astana\" peer. Type = friend means that the client can be both a receiving and a sending party. Secret is the password for authorization. Context is the name of the instruction that determines what to do with the call (these instructions are contained in the <<extensions.conf>> file). <<Host = dynamic>> means that the user can connect from any IP address. Figure 5: Checking the installed version. Figure 6: Copying default settings. Figure 3.0 Opening ports for Asterisk. GNO nano 5.4 (global)  
Figure 3.1 SIP settings on remote server No. 1. Figure 3.2 Dialplan settings on remote server No. 2. Figure 3.3 Captured SIP packet data. Figure 14 shows the RTP stream analysis. The important sections of the particular graph are the Jitter and the percentage of the expected and lost RTP packet. Packet loss can provide low-priority backdoors so cybercriminals can attack. In our case, there is no packet loss and minimal jitter, which indicates a stable connection.