Study On Token Ring Topology Designing Procedure Computer Science Essay

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Connect nodes in a ring shaped design is called ring topology. To design simple ring topology we need a switch, nodes (Computer and peripherals) and connecting cables. Following figure shows a basic ring topology.

To design ring topology in opnet we can use rapid configuration wizard in the topology menu. Rapid configuration wizard have two screens, first screen defines topology configuration like Bus, Ring, Star, Tree topologies. Second screen defines Center Node Model (type of switching device) like switch, hub, router etc., Periphery node model defines end node of a network like computer, printer etc, Link model defines the inter communication channel specification like 4Mbps or 16Mbps connectivity cables. Number defines the total number of periphery nodes in the current topology. Placement block defines center point of the topology and total radius of the ring. Here our current simulation model having the following center, periphery and link model as follows,

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Network Nodal configuration is defined using THT - parameter of the nodal structure and also configuration needs the control of the traffic along the network. Each node has been set for their model as tr_station. Here, we have to assign tr_station_adv as the nodal model of the topology instead of tr_station model for configure node in advanced mode. Topology nodal name is assigned by default. We have to configure all nodes individually. So among 16 nodes, choose any one node, to select all nodes by choosing select similar nodes option in the popup menu will automatically select similar node in the scenario. Move to the next option Edit attributes .In the Edit Attribute Checkbox, the Apply Changes to selected Objects is checked, this will help to configure all nodes at the same time.

Now in Attribute box of the node, select model to reset the tr_station to tr_station_adv from their drop-down menu list. Then the THT of the node has to define for testing the network packet transfer work model.THT is the TOKEN HOLDING TIME. It is nothing but the amount of time taken by a single node to keep their token for packet exchange. The data share is possible only for the particular node which is having the token. Some of the Token Ring Parameters are Address, Hop propagation delay, Operational mode, Promiscuous mode, Ring ID, Spawn station offset, Stack Modification Time, station Latency at bits, THT duration at seconds. At the list of Token ring Parameters, THT duration is selected for promoted which allows to set multiple THT. This is done by selecting the option promoted named promote Attribute to Higher Level at THT Duration box. By defining multiple Token Time duration the nodal network is changing their convenient time allocation at run time.

Packet generation is done only at the ON state of the Token Ring MAC (media access control).Traffic Generation needs parameters like start time, ON state time, OFF state time, etc., to fix the packet transfer control. Exponential (100) is assigned at the ON State Time attribute and exponential (0) is assigned at the OFF State Time attribute. On and OFF state Time is made the generated time as the mean between the successive events at its exponential interval. Next hierarchy is the Packet Generation Arguments under Traffic Generation Parameters. We have to generate packets in a timely manner; this is done by set Inter-arrival Time as exponential (0.025). Check that all configuration setting is made. At last, Apply changes to selected option check box is selected to made that preferred configuration setup for all the selected nodes. Then Click Ok at Nodal Attribute box. Now, the window status is Project Editor Window. Project is made sure to save. Thus, our Nodal Configuration setup is done. Next step is our simulation test for our current configuration.

Simulation Configuration:

Behavior of the network under nodal interaction is defined at simulation part. Network Performance check is done under different THT. For which, we made THT duration of Token Ring Parameter as promoted in nodal configuration setup.

Simulation configurations of the current scenario are,

Duration: 5 minutes

Seed: 128

Values per static: 100

Update interval: 100000 events

In the object attribute add current scenario as unresolved attribute. We have to collect performance of the current topology. So we need different load, traffic etc. Value field in the objet attributes defined as .01, .02, .04, .08, .16 and .32. Save these configurations as a scalar file named in scalar file text box.

Statistics configuration:

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To collect the traffic, load, delay and all other performance data we have to add those parameters in the statistics configuration. In our simulation we need,

Network load

Traffic rate

Throughput

Packet loss ratio

Global statistics of the individual scenario (Sent and received)

Load

Throughput

Delay

Traffic drop

Add these statistics parameters in every node will collect and save it to the specified scenario. We need these parameters as time based units like number of packets or bits per time (minute, sec, or hour etc).

To define these parameters as scalar, select Choose Statistics Advanced option in the simulation menu. To map the scenario with data is by selecting Choose attributed object as current scenario duration. Change every option in Global, Node and link statistics probe attribute Scalar data as enable, and type as time average.

Token Bus :

Token Bus topology designing procedure

Connect multiple nodes to a common communication bus is called bus topology. To design simple bus topology we need a common bus(coaxial-cable), nodes (Computer and peripherals) and connecting cables. Following figure shows a basic bus topology.

TOKEN-BUS

To design bus topology in opnet we can use rapid configuration wizard in the topology menu. Rapid configuration wizard have two screens, first screen defines topology configuration like Bus, Ring, Star, Tree topologies. Second screen defines Center Node Model (type of switching device) like switch, hub, router etc., Periphery node model defines end node of a network like computer, printer etc, Link model defines the inter communication channel specification like 4Mbps or 16Mbps connectivity cables. Number defines the total number of periphery nodes in the current topology. Placement block defines size of the topology in horizontal (top and bottom) and vertical (left and right) allignment. And the last row of placement block contains X and Y - coordinates of the bus head, size of the bus and tap. Here our current simulation model having the following center, periphery and link model as follows,

Node Model: tr_station

Link Model: bus_adv

Tap model: bus_tap_adv

Number of Nodes: 16

This configuration creates a network topology like following figure

Bus Node Configuration:

Network Nodal configuration is defined using THT - parameter of the nodal structure and also configuration needs the control of the traffic along the network. Each node has been set for their model as tr_station. Here, we have to assign tr_station_adv as the nodal model of the topology instead of tr_station model for configure node in advanced mode. Topology nodal name is assigned by default. We have to configure all nodes individually. So among 16 nodes, choose any one node, to select all nodes by choosing select similar nodes option in the popup menu will automatically select similar node in the scenario. Move to the next option Edit attributes .In the Edit Attribute Checkbox, the Apply Changes to selected Objects is checked, this will help to configure all nodes at the same time.

Now in Attribute box of the node, select model to reset the tr_station to tr_station_adv from their drop-down menu list. Then the THT of the node has to define for testing the network packet transfer work model.THT is the TOKEN HOLDING TIME. It is nothing but the amount of time taken by a single node to keep their token for packet exchange. The data share is possible only for the particular node which is having the token. Some of the Token bus Parameters are Address, Hop propagation delay, Operational mode, Promiscuous mode, bus ID, Spawn station offset, Stack Modification Time, station Latency at bits, THT duration at seconds. At the list of Token bus Parameters, THT duration is selected for promoted which allows to set multiple THT. This is done by selecting the option promoted named promote Attribute to Higher Level at THT Duration box. By defining multiple Token Time duration the nodal network is changing their convenient time allocation at run time.

Packet generation is done only at the ON state of the Token bus MAC (media access control).Traffic Generation needs parameters like start time, ON state time, OFF state time, etc., to fix the packet transfer control. Exponential (100) is assigned at the ON State Time attribute and exponential (0) is assigned at the OFF State Time attribute. ON and OFF state Time is made the generated time as the mean between the successive events at its exponential interval. Next hierarchy is the Packet Generation Arguments under Traffic Generation Parameters. We have to generate packets in a timely manner; this is done by set Inter-arrival Time as exponential (0.025). Check that all configuration setting is made. At last, Apply changes to selected option check box is selected to made that preferred configuration setup for all the selected nodes. Then Click Ok at Nodal Attribute box. Now, the window status is Project Editor Window. Project is made sure to save. Thus, our Nodal Configuration setup is done. Next step is our simulation test for our current configuration.

Simulation Configuration:

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Behavior of the network under nodal interaction is defined at simulation part. Network Performance check is done under different THT. For which, we made THT duration of Token bus Parameter as promoted in nodal configuration setup.

Simulation configurations of the current scenario are,

Duration: 5 minutes

Seed: 128

Values per static: 100

Update interval: 100000 events

In the object attribute add current scenario as unresolved attribute. We have to collect performance of the current topology. So we need different load, traffic etc. Value field in the objet attributes defined as .01, .02, .04, .08, .16 and .32. Save these configurations as a scalar file named in scalar file text box.

Statistics configuration:

To collect the traffic, load, delay and all other performance data we have to add those parameters in the statistics configuration. In our simulation we need,

Network load

Traffic rate

Throughput

Packet loss ratio

Global statistics of the individual scenario (Sent and received)

Load

Throughput

Delay

Traffic drop

Add these statistics parameters in every node will collect and save it to the specified scenario. We need these parameters as time based units like number of packets or bits per time (minute, sec, or hour etc).

To define these parameters as scalar, select Choose Statistics Advanced option in the simulation menu. To map the scenario with data is by selecting Choose attributed object as current scenario duration. Change every option in Global, Node and link statistics probe attribute Scalar data as enable, and type as time average.

Balanced and Unbalanced networks

To evaluate performance of a network we have to change different network load for both Token bus and ring topology,

Balanced network: All nodes having sane packet inter - arrival time.

Unbalanced Network: Half of the nodes in the network having same inter arrival time and remaining are having another inter arrival time

Configuration

In Balanced network all nodes having inter arrival time 0.025.

In Unbalanced network 0-7 nodes having inter arrival time 0.005 and 8-15 having inter arrival time 0.075.