CHAPTER 5 SIMULATION FRAMEWORK MODELING 5.1 INTRODUCTION This chapter starts with the design and development of the universal mobile communication system network and implementation of the TCP congestion control flavors, queuing disciplines for implementation of QoS in UMTS network model. For the implementation of different TCP flavor s and queuing disciplines various scenarios have developed using the OPNET Modeler 14.5. For creating different scenarios start up wizard is used and dragging of different devices like User equipment, RNC, Node B, SGSN, GGSN and servers etc, interconnecting them with the appropriate links. When the model development and testing within OPNET Modeler performed, modified TCP Tahoe is implemented to check its performance for multimedia data. 5.2 TCP SCNERIOS A number of TCP flavors are available for implementation. We have implemented four different scenarios for four different types of TCP versions to UMTS network. These scenarios contain two types of the UMTS traffic classes, one for the conversational class and other for the interactive class. Workstations contain different UMTS QoS profile configurations for different multimedia classes. Each UMTS scenario is designed and implements one TCP version. Four different TCP versions are implemented on four different UMTS network scenarios (i.e. TCP RENO, TCP SACK, TCP TAHOE and TCP New RENO). These scenarios are implemented by using different entities that is used to design a UMTS model.
SIMULATION FRAMEWORK MODELING 114 5.3 ENTITIES OF THE OPNET UMTS NETWORK MODEL FOR TCP FLAVORS We have selected different network elements to create UMTS network model to create various TCP congestion control model and configure it according to the requirement of our scenarios. Following entities are selected from the Object Palette Tree from the OPNET Modeler. Application Configuration Profile Configuration Packet Discarder Umts_rnc_atm2_eth2_slip2_adv UMTS_node_ b_ atm_ adv Umts_ggsn_atm8_ethernet8_slip8_adv Umts_sgsn_ethernet9_atm_slip_adv FTP Server Umts_wkstn_adv 128_Ethernet switch Various links are used to connect different elements of the UMTS network. That is: Ethernet Switch-> FTP Server- 100 BaseT GGSN->Ethernet Switch- 100 BaseT SGSN->GGSN-PPP_DS3 RNC->SGSN-ATM_OC3 Node B->RNC-ATM_OC3 5.4 ENTITIES OF THE OPNET UMTS NETWORK MODEL FOR QUEUING DISCIPLINES Application Configuration Profile Configuration Umts_rnc_atm2_eth2_slip2_adv
SIMULATION FRAMEWORK MODELING 115 UMTS_node_ b_ atm_ adv Umts_ggsn_atm8_ethernet8_slip8_adv Umts_sgsn_ethernet9_atm_slip_adv FTP Server Umts_wkstn_adv 128_Ethernet switch Various links are used to connect different elements of the UMTS network. That is: Ethernet Switch-> FTP Server- 100 BaseT GGSN->Ethernet Switch- 100 BaseT SGSN->GGSN-PPP_DS3 RNC->SGSN-ATM_OC3 Node B->RNC-ATM_OC3 All these network entities are configured according to the requirements of the two scenarios. These scenarios are explained in the following sections. 5.5 TCP CONGESTION CONTROL VARIANTS MODELING OVER UMTS 5.5.1 OPNET Modeler simulation environment To perform simulations, OPNET Modeler simulation environment utilizes two mechanisms i.e. Project and Scenario. In any OPNET Modeler simulation, projects always remains at the top level. Initially a project workspace is created. Each project has one or more scenario as per the requirement of network. These scenarios show the network configuration that will be simulated by the modeler. In OPNET modeler a scenario shows the network configuration of a real network that includes topology used in network, their protocols, applications, different services and traffic flow. A project have one or as per requirement multiple scenarios also possible. Each scenario contains a network that is either same or a little bit different with varied parameters. In this thesis, a universal mobile telecommunication system network was designed with four user
SIMULATION FRAMEWORK MODELING 116 equipment. When the design of network is completed in all respect the scenario was duplicated with some modification in the network and in network or object parameter for every simulation. Traffic is created by application and profile configuration parameters and it depicts the different levels of congestion at various objects in the network. The results are obtained from scenarios either they are similar networks with minor variations to the network or parameters or different. The scenarios are used to permit results after the execution. Results will be taken and utilized in analysis and comparison in various scenarios. Figure 5.1 New Project - Project and Scenario names
SIMULATION FRAMEWORK MODELING 117 UMTS is modeled through the OPNET Modeler. At the beginning start up wizard is used to create new project and various scenarios in a project. Figure 5.1 shows the startup wizard to create new project named TCP UMTS. Different scenarios are design to as per the requirement of project. When the name of the project is given in the startup wizard, it starts. After entering the name of the project in startup wizard a new window is opened called start up wizard initial topology. This window shows that a user can start with any network topology as per the requirement of the user. So by using this window user can design its own network or may be import the network from others. Fig. 5.2 is used to show startup wizard to create initial scenario. Fig. 5.2 Startup wizard Create initial scenario
SIMULATION FRAMEWORK MODELING 118 A number of methods are used to create initial network that is shown in fig. 5.2. User can start with initial topology as per requirement or import the network topology by some specially formatted file that is offered as in built of the OPNET modeler. When design the network according to own criteria the option given in initial topology wizard is creates empty scenario. So to design UMTS network, this research work does not import any built in technology. Create empty scenario gives an option to design network manually. For a user this option is very much benefitted to design network manually as per the requirement. This creates empty scenario shows blank widow to freely design the any type of network that is choose by the user. In Figure 5.2, create empty scenario is opted for this research work. Fig. 5.3 Start up Wizard Initial Topology
SIMULATION FRAMEWORK MODELING 119 When create empty scenario is choose as initial topology a new window is opened in startup wizard to choose the size of the network referred as network scale. To define the network scale and its size network scale is used. Various network scale is shown in fig. 5.3 i.e. world, campus, office, logical and others. In this research project, to simulate a universal mobile telecommunication system logical network scale is used. Figure 5.3, depicts that logical scale is choose for this research work. When the size and scale of UMTS network is opted, the next work is to define various technologies will be utilized in the network. This research work is based on the UMTS technology, so to design the UMTS network, UMTS is choose in the technology window. To simulate UMTS network UMTS network technology is used. When start up wizard network technology step is performed as to choose UMTS network, a new window is open that shows various elements that is used to design the UMTS network and required to create different scenarios. In fig. 5.4Object palette shows all the UMTS network elements that are required to design UMTS network i.e. various type of base stations, different radio network controllers, SGSNs and GGSNs. Object palette contains a number of UNTS network elements that will be used to design the UMTS network. As per the design requirement of UMTS network, the selections of the elements are done by using the object palette. According to the selection of different technologies, the technology and network elements are given in object palette. By using object palette they can be simply put in to the project editor. On the project editor different UMTS network elements are placed according design requirement of UMTS network. This research project only simulate the UMTS network, so the object palette only shows the network elements used in UMTS network shown in fig. 5.4. When all of above steps are finished, the network simulation environment has been created and now it is ready to create network models and scenarios and perform simulation.
SIMULATION FRAMEWORK MODELING 120 Figure 5.4 Start up Wizard - Object Palette 5.5.2 OPNET Modeler simulation environment for TCP flavors To simulate different TCP congestion control algorithms, this research work modeled a UMTS network in which five end users are connected to the UMTS network. Base stations are used to provide a connection between end users and UMTS network. Figure 5.5 shows that five end users are connected to a base station and further connected to the UMTS network.. The five end users can send voice data to each other by using the voice server in the network.
SIMULATION FRAMEWORK MODELING 121 Fig.5.5 UE with node B Chapter 1 shows the basic architecture of UMTS network. UMTS architecture mainly configure by three domains: Core Network (CN), UMTS Terrestrial Radio Access Network (UTRAN) and User Equipment (UE). To model a UMTS network, different models of UMTS network are properly used and connected in a scenario. Both circuit switched and packet switched networks are used in UMTS networks. This research work is concerned only with packet switched network, so circuit switched network elements like Mobile services Switching Centre (MSC), Visitor location register (VLR) and Gateway MSC are not modeled in this research work. The key elements of packet switched network are Serving GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN). These key elements are necessary for the UMTS core network and should be modeled in this research work. This research work starts to model the core
SIMULATION FRAMEWORK MODELING 122 network of UMTS. PPP_DS3 link is used to connect various routers as shown in Figure 5.5. GGSNs connected to router and finally the server. UMTS model contain end users that is connected to base stations and base stations is further connected to SGSN and GGSN. According to the scale of the network number of SGSN models in the network. This research work contains only one SGSN and it is connected server by via PPP_DS3 link. Figure 5.5 depicts the design of core network when SGSN are connected to RNC. Fig. 5.6 UTRAN with UE When RNC is added to the base station then further UMTS Terrestrial Radio Access Network (UTRAN) is added into the network. UTRAN contain two different types of network models: the radio network controller (RNC) model and the Node B (base station) model. Number of radio network controller can be connected to a serving GSN and number of base station can be connected to a radio network controller. To connect the base station to RNC and the RNC to the SGSN, ATM_OC3 links are used. This research designs a simple UMTS network in which one base station, one RNC and one SGSN and
SIMULATION FRAMEWORK MODELING 123 GGSN is used. The topology, network elements and connections in between them is shown in figure 5.7. Each scenario is designed for five users with their movement across Node B. Along with users, simulation model have following entities: one Node B access point, RNC, SGSN, GGSN and one FTP server for single type of traffic class. For connectivity between nodes various links were used form object palette. After the architecture is completed, the attributes required for each node are defined for network. Applications are defined in the application configuration node and packet discarder utility is used to discard the packet at particular time interval. For each TCP variants different scenarios are designed for measuring the different global and object statistics. Figure 5.7 UMTS Modeling for TCP
SIMULATION FRAMEWORK MODELING 124 OPNET Modeler has a UMTS workstation model, this UMTS workstation model may be utilized as the UMTS user equipment (UE). UMTS workstation model may be utilized as voice end users and some other used as FTP clients sending and receiving FTP data to and from FTP server. This research uses, five UMTS workstation models that are added to basic UMTS network is depicts in Figure 5.7. These workstations models are used to simulate voice call and FTP data over various TCP congestion control flavors. In OPNET modeler to connect UMTS works station models to the UMTS network, manual configuration is performed to utilize the correct SGSN. To perform this, first right click on the SGSN node, it shows various parameters of SGSN node. Click on the attributes dialog and select SGSN Edit Attributes, under. It finally opens various attributes of SGSN node. In the attributed list select a parameter known as SGSN ID. The default value of UE Serving SGSN ID is 0. All the UMTS workstations that connect with SGSN by using the different base stations contain the same ID as provide in the serving ID of SGSN. A right click is done on user equipment; different user equipment parameters are shown. By selecting the UE Serving SGSN ID, it is confirmed that which UE is connected to which SGSN node. All the UEs set with this SGSN ID. Here, a base UMTS network has been modeled. 1) UE attributes Attributes is set for user equipment to communicate with server and other UMTS network equipments. Various parameters such as application destination preferences, application supported profiles and UMTS QoS profile configuration is set for user equipments. The UMTS QoS profile configuration is set for background class because the user equipments transmit and receive the FTP files and FTP data belongs to background class. Traffic type is all discrete in manner. User equipments are connected to server through a wireless link there must a mapping in between symbolic and actual name of server. The selection weight that is given to server is 10. Table 5.1 shows the attributes that is assigned to user equipments.
SIMULATION FRAMEWORK MODELING 125 After configuration of user equipment attributes, the attributes of FTP server is to be set. Server is used to send and receive the FTP data. Attribute Application Symbolic Name Actual Name Table 5.1 User Equipment attributes Value FTP _Application FTP Server Logical Network. FTP Server Selection Weight 10 Profile Name Traffic Type Application Delay Tracking Delivery of Erroneous SDU FTP Profile All Discrete Disabled No Block Error Ratio 1/100 Maximum Bit Rate (Uplink) Maximum Bit Rate (Downlink) Maximum SDU Size Priority Level Mapped Logical Ch. Queuing 64 Kbps 64 Kbps 1500 octets Lowest priority Modified Weighted Round Robin
SIMULATION FRAMEWORK MODELING 126 2) FTP server attributes Application configuration is used to set the attributes for various applications that a user wants to be performed in network. This research only use FTP data, so FTP application configuration attributes is set. Here the attributes is set for file size that is 2 Mb, inter request time constant 1000 and symbolic server name is FTP server. Server is set to FTP application supported. 3) Application configuration Application configuration is used to set the application parameters that are implemented in UMTS network. Application configuration set various parameters for applications. In this UMTS network model only FTP application is implemented. Application configuration attributes is set in application definitions where the description of FTP application is set to FTP. Other parameters such as file size, type of service, symbolic server name are shown in table 5.2. Table 5.2 FTP Application Configuration Attributes Attribute Value Command Mix 100% Inter request Time (seconds) constant (1000) File Size Constant (20000000) Symbolic Server Name FTP Server Type of Service Best Effort (0) RSVP Parameters Back-End Custom Application None Not Used
SIMULATION FRAMEWORK MODELING 127 4) Profile Configuration Profile configuration is used to set various profiles of application that this research used in network. To transfer FTP data FTP profile is used. So, different attributes are set to run the FTP profile in the network. For FTP application profile configuration set the parameters like FTP application start time its duration and repeatability that is shown if table 5.3 Table 5.3 FTP Profile configuration attributes Attribute FTP Application Name Value FTP_Application Start time offset Constant (5) Duration (seconds) Repeatability FTP Profile name Operation Mode End of Profile Once at a start time FTP _profile Serial (ordered) Start time (seconds) Constant (100) Duration (seconds) Repeatability End of Simulation Once at start time 5) Packet Discarder Attributes Packet discarder is used to drop the packets at various time intervals. To discard the packets at various time intervals a start time and end time. The discard count shows that
SIMULATION FRAMEWORK MODELING 128 what numbers of packets are discarded in that particular time interval. At different start and end time a fixed number of packets are dropped that shows network congestion. For various packet drops such as 5%, 10%, 20% and 25% are set to detect the congestion. Table 5.4 shows the packet discarder attributes. Table 5.4 Packet Discarder Attributes Start time End Time Discard Count (%) 100 100.5 5 150 150.5 10 200 200.5 15 250 250.5 20 300 300.5 25 5.5.3 Analyzing simulation for modified TCP Tahoe Performance For implementation of TCP Tahoe with modified TCP Tahoe five scenarios have been created, i.e. TCP Tahoe, TCP SACK, TCP RENO, TCP New Reno and Modified TCP Tahoe. First we analysis the TCP congestion window for all TCP variants. After that we compare the results for all variants of TCP. A modified TCP Tahoe is implemented and results are compared for both TCP Tahoe and modified TCP Tahoe for TCP congestion window. A single scenario completed in all aspects, duplicated and then attributes are set for all the scenarios. Each scenario is employed only for file transfer by using Background class.
SIMULATION FRAMEWORK MODELING 129 Fig.5.8 Network Simulation Model for Modified TCP Tahoe Fig. 5.8 shows the simulation model for modified TCP Tahoe congestion control protocol. Certain parameters of TCP Tahoe are changes to perform modification in TCP Tahoe. The Parameters that is modified for TCP Tahoe congestion control protocol is shown in table 5.5 Table 5.5 shows that receive buffer size is set to 8760 bytes and receive buffer usage threshold is set to.75 and the maximum segment size is initialize with 4 MSS. The retransmission threshold that is initial RTO is 3.0 sec and minimum and maximum RTO is 1.0 sec and 54 sec. Table 5.5 shows the and modified TCP Tahoe parameters. RNC is connected to node b. The parameters of UMTS RNC are shown in table 5.6.
SIMULATION FRAMEWORK MODELING 130 Table 5.5 UMTS Modified TCP Tahoe Parameters Attributes Receive window size at FTP server Receive window size at User equipments Maximum ACK Delay Value 8760 bytes 8760 bytes 0.2 seconds Maximum ACK segments 2 Maximum ACK threshold Sack option Slow start initial count Minimum RTO Maximum RTO 1450 bytes auto assigned Disabled 4MSS 1 Sec 64 Sec RTT deviation coefficient 4.0 Fast Retransmit Fast Recovery Enabled Disabled Deviation gain 0.25 Radio network controller is connected to node b and node b is connected to a number of user equipments. For UMTS RNC transmission and receive window size is set to 8 and the uplink and downlink radio link control is set in unacknowledged mode. The parameters of UMTS RNC are shown in table 5.6.
SIMULATION FRAMEWORK MODELING 131 Table 5.6 UMTS RNC parameters Attributes Value Transmission window size 8 Receiver window size 8 Timer move receiving window (MRW) millisecond 180 Timer discard (millisecond) 1500 Max MRW 8 In sequence delivery UL radio link control (RLC) mode DL RLC mode No Unacknowledged mode Unacknowledged mode 5.6 QUEUING DISCIPLINES MODELING OVER UMTS To implement various queuing disciplines in UMTS network OPNET simulator shows a network model for that. Various queuing disciplines are implemented in UMTS network to manage the traffic and also to reduce the congestion in the UMTS network. To modeled queuing discipline in UMTS network this research first creates a simulation environment. After that various queuing discipline is implemented for evaluating the best queuing discipline for UMTS network. 5.6.1 OPNET Modeler simulation environment Following fig.5.9 shows the network model for implementation of queuing disciplines in UMTS network. In this network model two servers one for transferring FTP file and one for transferring Voice is used. The remaining network components are same as used in UMTS TCP scenario. In this network model number of users is more to communicate
SIMULATION FRAMEWORK MODELING 132 with each other and also with server. So UE_1 & UE_5 send and receive the FTP files where UE_4, UE_5 and UE_5 send and receive voice data. Two routers are used to connect the core network with GGSN. Ethernet switch is used to connect GGSN with FTP and Voice server. Fig.5.9 QoS on UMTS network This thesis implement various queuing disciplines on UMTS network to find which queuing discipline is best suitable for UMTS network to send and receive the multimedia data. Queuing disciplines that are implemented in UMTS network are First in First out (FIFO), Priority queuing (PQ), Weighted fair queuing (WFQ), Modified weighted round robin (MWRR) and deficit weighted round robin (DWRR).QoS implementation is perform on UMTS shown as QoS configuration in Fig. 5.9
SIMULATION FRAMEWORK MODELING 133 5.6.2 Non QoS on UMTS network Modeling In Non QoS scenario the QoS configuration is not implemented in UMTS network. Network model contain only application and profile configuration. Fig. 5.10 shows that none of the queuing discipline is implemented in UMTS network model. Fig.5.10 Non QoS on UMTS network To model QoS and Non QoS on UMTS network various network components, parameters and configuration is used. Following figures shows various parameters and attributes that are used to create the network model. 1) Application Configuration In OPNET modeler application configuration is a set of rules. Application configuration contains different types of OPNET libraries that are used to produce the traffic on the network as per the type of user requirement. As if user equipment contain voice data then
SIMULATION FRAMEWORK MODELING 134 for this user equipment voice traffic is set. To perform simulation for each new project in OPNET MODELER, It is required to configure the application configuration in the scenario. For the queuing network model application configuration is defined for two applications FTP and voice configuration. FTP is configured as a low load and voice conferencing encoder scheme is GSM FR with best effort TOS. The reason for generation of these different traffic types is to generate and analyze the performance of network on different application scenarios. Fig. 5.11 shows the different FTP and voice conferencing parameters. Application configuration attributes is set for application definitions. Number of rows for application definitions is set to two i.e. FTP application and voice application. Further for FTP application the FTP parameters are configured and for voice application voice conferencing parameters are configured. Table 5.7 shows the FTP Application Configuration Attributes. Fig.5.11 Application configuration attributes
SIMULATION FRAMEWORK MODELING 135 Table 5.7 FTP Application Configuration Attributes Attributes Value Command Mix 50% Inter request Time (seconds) constant (3600) File Size Constant (10000000) Symbolic Server Name FTP Server Type of Service Best Effort (0) RSVP Parameters None Back End Custom Application Not Used Table 5.8 Voice Application Configuration Attributes Attributes Value Silence Length Symbolic Destination Name Encoder Scheme Default Voice Destination GSM FR Voice Frames Per Packet 2 Type of Service Best Effort (0) Traffic Mix (%) All discrete
SIMULATION FRAMEWORK MODELING 136 2) Profile Configuration Profile configuration is a profile of the nodes which they act according to define parameters in application configuration. It is essential to define profile configuration in the network otherwise there is no possibility to simulate the network. Two different profile configuration attributes each for different application are set in the number rows. First define FTP load and second define voice conferencing. Table 5.9 shows the detail parameters of FTP profile configuration. Table 5.9 FTP Profile configuration attributes Attribute Value FTP Application Name FTP_Application Start time offset Constant (5) Duration (seconds) Repeatability FTP Profile name Operation Mode End of Profile Once at a start time FTP _profile Simultaneous Start time (seconds) Constant (100) Duration (seconds) Repeatability End of Simulation Once at start time Voice profile configuration attributes are set to run the voice profile. Table 5.10 shows the voice profile configuration attributes. Voice application name is set to voice application and start time offset is set to constant 5.
SIMULATION FRAMEWORK MODELING 137 Table 5.10 Voice Profile configuration attributes Attribute Value Voice Application Name Voice Application Start Time Offset (Seconds) Constant (5) Duration (Seconds0 Repeatability Profile Name Operation Mode End of Profile Once at start time Voice Profile Simultaneous Start Time(Seconds) Constant (2) Duration (Seconds) Repeatability End of Simulation) Once at start time 3) QoS Parameters Generally, Quality of Service defined as the ability of the network to guarantee certain levels of service to diverse traffic flows. Global QoS profiles are implemented on UMTS scenario, which means every node within the UMTS scenario have access to global quality of service profiles. QoS profile is set to provide scheduling for different multimedia traffic as shown in fig. 5.12
SIMULATION FRAMEWORK MODELING 138 Fig.5.12 QoS parameters 4) Node B Attributes UMTS node B is used to transmit and receive the multimedia data to and from radio network controller and user equipment UE. Node B is connected to a particular radio network controller by setting the parameters of serving RNC-ID to 1. Other parameters are set as default. In UMTS network model if multiple base stations and RNC are
SIMULATION FRAMEWORK MODELING 139 connected then, each base station is uniquely identified by its serving RNC-ID shows in fig. 5.13 Fig.5.13 Node B attributes
SIMULATION FRAMEWORK MODELING 140 5) UE attributes In UMTS QoS and Non QoS model two types of user equipment is used to send and receive multimedia data that is FTP user and voice user. Itself the user equipment is communicated with each other and by the voice server also. Attributes set for user equipment which carrying voice data comes in UMTS QoS profile configuration. In UMTS profile configuration the conversational class is chosen. Various Conversational class parameters are shown is table 5.11(a) and conversational class parameters at UE_4 shown in table 5.11(b). Table 5.11(a) Conversational class parameters Attribute Value Deliver of Erroneous SDU No Block Error Ratio 1/100 Delivery Order No Maximum SDU Size (octets) 1500 Transfer Delay (ms) 65535 Allocation Retention Priority Mapped Logical Ch. Queuing Default Modified Weighted Round Robin For Voice Conversation different voice parameters are set at various user equipments. These parameters are used to perform communication among user equipments. Application destination preferences are set to voice application shown in table 5.12
SIMULATION FRAMEWORK MODELING 141 Table 5.11(b) Conversational class parameters at UE_4 Attribute Value Symbolic Name Actual Name Voice Destination Logical. Network_UE_4Voice Selection Weight 10 Various Application supported profile and services are also set to run voice profiles on various user equipments and server. Table 5.12 shows the application supported profiles for user equipment. Table 5.12 Voice profile parameters Attribute Value Profile Name Traffic Type Application Delay Tracking Voice Profile All Discrete Disabled 6) Server Attributes FTP and voice server is used to transmit and receive the data to and from the user equipment. Application supported services parameters is set for various application that is provided by the server. Voice server attributes are set for application supported services. The application supported services for voice server is voice application.
SIMULATION FRAMEWORK MODELING 142 Table 5.13 Voice Parameters description table Attribute Value Service Status Enabled Processing Speed (Bytes/ Sec) 1,000,000 Overhead (Sec/Request) 1E-006 Selection Weight 10 Type of Service As requested by client Various voice application parameters are set on voice server. Voice server provides the voice specific services that are shown table 5.13 To check whether is packets is transmitted or received at user end, animation viewer is used. Fig. 5.14 and 5.15 shows the real scenario that shows the receiving and transferring of packets of TCP and QoS scenario in UMTS network. Fig. 5.14 Animation view of packets transfer and receive in QoS scenario
SIMULATION FRAMEWORK MODELING 143 Fig. 5.15 Animation View of Packet Transfer and Receive in TCP Scenario 5.7 PERFORMANCE PARAMETERS For performance evaluation of TCP congestion control algorithms and for queuing disciplines various metrics are considered. Different parameters are considered for the performance evaluation of the congestion control protocols. Each congestion control protocol produce different impact on the overall performance of the UMTS network. This thesis evaluates five parameters that are used to study the comparison of overall performance of the UMTS network. The parameters are delay, throughput, Jitter, MOS and congestion window for performance evaluation. These parameters are very significant in evaluation to calculate UMTS network performance under various TCP congestion control protocols and QoS in UMTS network. These congestion control protocols and QoS need to be checked against certain parameters for their performance. To check TCP congestion control protocols effectiveness in finding minimum congestion or packet loss in network, this thesis will modify the existing TCP Tahoe congestion control algorithm. If one TCP congestion control protocol produces very high end to end
SIMULATION FRAMEWORK MODELING 144 delay, it means particular congestion control protocol is inefficient as comparison to other protocols which shows low end to end delay. Throughput is also considered to define the network performance. Throughput is defined as the successful deliveries of packets in time. If a congestion control protocol illustrates high throughput it means it is the efficient congestion control protocol than other congestion control protocols which gives low throughput. For a network the jitter is considered to be lower and congestion window the lowest congestion in network. 5.7.1 Delay Packet end to end delay is defined as the time taken for producing a packet by the sender up to the receiving of a packet at destination. So packet end to end delay is the time taken by a packet to travel across the network. Time is defined in seconds. Entire delays like transmission time and buffer queues in the network are known as packet end to end delay. Sometimes this delay is known as latency. A multimedia application such as voice conferencing is a delay sensitive application so it is sensitive to packet delay. A low average delay is required for voice conferencing application in the network. FTP can tolerate a firm level of delay. Due to various types of activities network delay is raised. Throughput is a measure of how sound congestion control protocols minimize the packet drops in the communication network. 5.7.2 Throughput Throughput can be classified as the ratio of total amount of data send by the sender with respect to the data receives by the receiver. Throughput is also defined as time taken by the receiver to receive the last message. Throughput is measured as bytes per second (bytes/ second or bits/ second). Some factors like limited bandwidth, limited energy, unreliable communication between nodes and different topology changes in the network are the measure reason that affects the throughput. If a network shows high throughput it
SIMULATION FRAMEWORK MODELING 145 means it is the network with less number of dropouts and preference is given to this type of network. 5.7.3 Jitter Time variation between various packets arriving in the communication network is known as jitter. It means if multiple packets are arrived at different delay such as one packet arrive after 2 m/s and other packets are arrive after 3, 4, 5 m/s and so on this is known as jitter. In jitter packets arrive at receiver at different delay variations. Jitter occurred in the network by network congestion, route changes or timing drift. TCP/IP is accountable for dealing with the jitter impact on communication 5.7.4 MOS In voice communications, the mean opinion score (MOS) shows a numerical measure of the quality of human speech at the receiving end of the communication network. MOS implements subjective tests (opinionated scores) that are mathematically averaged to obtain a quantitative indicator of the communication network performance. 5.8 DES CONFIGURATION PARAMETERS The discrete Event Simulation criterion was configured by clicking on scenarios. Under the scenarios manage scenarios option is taken and the simulation is run for total time of 500 sec. All the scenarios that are to be run updated for a simulation time. After clicking on run option all the scenarios are executed serially. To monitor the overall simulation following DES configuration parameters are taken.
SIMULATION FRAMEWORK MODELING 146 Table 5.14 DES configuration parameters Simulation Parameters Simulation Time Value 10 minutes (500 Sec) Number of Nodes 05 Environment Size Traffic Type Logical Environment Constant Bit Rate Seed 300 Value per Statistics 300 Update Interval Simulation Number of runs 500000 events Based on Kernel type Preferences One for each scenario 5.9 VIEWING RESULTS After building the network with required node configuration in terms of parameters and network environment, this thesis run the simulation model. Prior to running a simulation model in OPNET modeler 14.5, the output data options to be obtained need to be selected; these are referred to as the performance metrics. In OPNET two types of statistics are taken, object statistics and global statistics. Object statistics are described as the statistics that can be gathered from the each and every node of the network and Global Statistics can be gathered from the whole network. This thesis gathered DES (global discrete event statistics) for every TCP congestion control protocol and Queuing discipline. This thesis gets various graphs from simulation
SIMULATION FRAMEWORK MODELING 147 like first for delay second for network throughput third for jitter and fourth for congestion. Main objective of the simulation is to model various TCP congestion control protocols and compare with Modified TCP Tahoe congestion control protocol. Other than this this thesis also model Queuing disciplines to perform QoS requirements in UMTS network. Some configuration or runtime options such as common settings, inputs and outputs, executions and duration of simulations can still be changed or selected before running the model. Finally, results are available after the simulation is run. Each result can be viewed as the project or scenario is saved after running the simulation. Required results must have been chosen as part of the performance metrics earlier selected, likewise to view results on the screen, one has to click the check box of the nodes or options whose results are needed. Results can be displayed in different views with the aid of the two presentation options available on the results window. This is done by making combination of the options that help present the result better.