THE CALCULATING METHOD OF NGN ACCESS NODE CHARACERISICS WHEN SERVICING VOICE AND DATA TRAFFIC

. Access nodes of NGN networks provide traffic aggregation to various network services and its transfer to the transport layer, which allows calling such networks multiservice.  1;2  . These networks are used to simultaneously transmit voice, video, and data presented in the from of standard packets. At the same time, network services provide an unlimited set of telecommunication services with specified characteristics of quality of service.  1;2  The selected technology of information distribution in the NGN determines the degree of complexity of access nodes and, of course, affects the quality of information exchange service between user terminals. One of the ways to ensure a given level of quality of service for each of the services is the introduction of priority service for certain traffic flows. Introducing priorities for packets is an effective way to manage the size of queues and the time spent in it. When a high-priority packet is received, a packet with a lower priority is either interrupted (absolute priority) or a high priority packet becomes the beginning of the packets queue (relative priority). In this paper, we study the characteristics of NGN access nodes as a two priority queuing system with a limited expectation.  5  . Formulas for calculating the probability of loss of speech packets, as well as data packets, and other characteristics of the access node have been proposed. The NGN's access nodes provide aggregation of traffic to various services directed by the Public Switched Telephone Network (PSTN) and its transportation to a higher level, which allows you to call such networks multiservice ones. The new generation networks allow simultaneous transmission of mixed streams (voice, video, and data) represented in the form of standard packets. One of the ways to ensure the specified quality of service is to introduce a priority method for servicing traffic flows  5  .

functioning of the NGN network largely depends on the quality of its end access nodes. Characteristics of the performance of the NGN endpoint with priority methods for maintaining the interfaces used, connected from the access network side at the physical network layer for the transmission of mixed traffic.
It is known that speech information traffic coming from channel switching networks is first converted to a packet form. After that, it is encapsulated in IP packets [2]. In this case, RTP and UDP protocol headers of 12 and 8 bytes respectively are added to the new packet. Additional 20 bytes are required for voice IP packeting and 4 bytes per packet addressing for the MPLS network. Thus, the total length of the packet address field (header) is 44 bytes, which is transmitted each time when a packet containing speech information is sent. Since the length of the RTR protocol information field is 160 bytes, the total length of the RTR protocol packet is 204 bytes. It is known that the data flow in packet networks is transmitted over the IP/MPLS network, which is switched at LSP addresses to the transport network.
The intensities of speech and data packet flows that arrive simultaneously at the NGN endpoints can be regulated by setting the probability of service failure rate.
The specified rates of failure (loss) of an NGN node shall be determined by the characteristics of mixed packets that have not been accepted for servicing by the network immediately and have been waiting in its buffer memory (in the queue). In NGN networks, the rate of loss of service quality for its endpoints is set based on the purpose, flows, their structure, and the technical means used to receive, process, and deliver information to their end users.
The purpose of the article is to develop engineering formulas for calculating the quality of service characteristics of multiservice access nodes of NGN networks.
Let's consider the process of functioning of a multiservice terminal node of the NGN network, which receives two Poisson information flows different in intensity. With the receipt intensity of λ 1 when servicing, it has an absolute priority, and others with the intensity of λ 2have no priority (relative priority). In this case, the average total intensity of the information flow entering the j terminal node is determined by the formula of 3;4: It is assumed that the mixed traffic at the terminal node servicing in the stationary mode is equal to the incoming traffic. In this case, the time distribution function for both types of packets (speech and data) is exponential with the parameter of µ 1 = µ 2 = µ. The discipline (algorithm) for servicing the packet stream is such that the first type of the stream has absolute priority over the second type of the stream. Packets that arrive within each priority are served in the order of the service algorithm used. During the receipt of the packet stream, when all V servicing devices (servers) have been busy, the first priority packets shall be interrupted and the second priority packets shall be serviced, taking into account its further return from the buffer memory (queue). If an incoming packet of the second priority is caught in the queue, it is to be queued on after the last packet of the first priority, and one packet of the second priority is to be lost. If other first-priority packets are already in the queue when the next first-priority packet arrives, it is to be lost as well, i.e. a limited service queue is allowed on each endpoint (Fig1). With this in mind, in stationary mode (2) Based on the system of algebraic equations (2), the probabilities of states of a classical multichannel system with a limited queue and absolute priority are determined. Using the normalization condition: where "r" is the number of waiting spaces (buffer memory duration) in buffer memory v-is the number of serving servers .
Here, Y=Y 1 +Y 2 =(  1 + 2 )/ (  1 + 2 )==y/v (7) is the bandwidth of the multiservice access node(server) of the NGN network, Expression (7) specifies that using criteria 1, calculations can be made for others. Taking into account(7) the formulas (5) and (6), it can be rewritten as follows: ( ) The average waiting time for a data packet to start processing (relative-second priority packets) is determined by the formula: The probability that the server will be in a pending state (pending greater than zero packets) is calculated as follows: 2. A method for calculating the quality of service characteristics of NGN network endpoints multiservice nodes (servers) that serve mixed packet streams with a limited queue and absolute priority has been proposed.
3. The obtained analytical formulas and the method for calculating the terminal multiservice nodes (servers)with a limited waiting queue and absolute priority are more generalized. From these, in particular cases, analytical formulas are obtained for calculating characteristics when using two (V=2) communication servers with and without bandwidth priority  1 =01,  2 =0,2=const, V=2 ;V=3 4. With the developed program, for example, two qualitative characteristics are proposed using the proposed formulas.