OPNET-Chapter 3Token Ring

OPNET IT Guru Academic Edition

Chapter 3 – Token Ring

‍N. Abedpoor‍

International Imam Reza University of Mashhad‍

N. Abedpoor – International Imam Reza University of Mashhad Dec. 2013

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● Token Ring Model Description

• Model Scope and Limitations

• Process Models

• Model Interfaces

• Packet Formats

• ICI Formats

• Token Ring Addressing and Ring Identifiers

● Lab 2 – Token Ring

Chapter 3 Lab2- Token Ring

N. Abedpoor – International Imam Reza University of Mashhad Dec. 2013 2

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● The Token Ring Access Method (TR) provides general

purpose networking at 4 or 16 Mbits/sec transmission rates

for small or large numbers of communicating stations

configured in a ring or hub topology.

● Detailed information on the Token Ring protocol can be found

in the following documentation:

• IEEE Standard 802.5, 1985 Specification— Token Ring Access Method.

Token Ring Description


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● Model Scope and Limitations

● The first important restriction is that the ring initialization and

recovery processes are not modeled explicitly. While the

model could be extended to address these areas (it is

provided in source code form), its primary usefulness is in

obtaining measurements of steady state performance.

● A second restriction has to do with the modeling of error

conditions and in general, the role of the NMT entity. In its

current form, the model makes no attempt to implement the

mechanisms related to the detection of damaged frames, or

the reporting of errors to NMT. The interface between MAC

and NMT is, in fact, not presently incorporated into the

implementation of MAC.

● The effects of station latency and propagation delay are also

incorporated into the model. The restack operation and the

THT are also explicitly modeled.


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The parameters that may be easily controlled by the user,

without having to modify the internals of the provided models

include:

● The number of stations attached to the ring

● The address of the station that launches the token as the

simulation begins, the “active monitor”

● The delay incurred by frames and tokens as they traverse a

station’s ring interface

● The propagation delay separating stations on the ring

● The number of bits per second transmitted by the medium

● The duration of the THT, the amount of time a station may

transmit on the ring

● The amount of time it takes a station to modify its priority

stacks in a restack operation


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Model features include:

● 24-bit assured minimum latency

● Token acceleration

● Modularity—there can be more than one ring in a network

model

● Token Ring link models allow you to simulate point-to-point

trunk links; a single trunk link can carry traffic for multiple

VLANs as specified by IEEE 802.1q.


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Model features include:

● You can configure port-based VLANs on all generic bridge

and switch models, and on any vendor-specific models that

support this technology.

● To configure a VLAN, set the VLAN scheme attribute to

“Port-based VLAN” on the bridge or switch supporting the

VLAN. You can assign VLAN identifiers to specific port

numbers in the VLAN Port Configuration Table. (To find a

link’s port numbers, use Link Interfaces on the Edit Attributes

(Advanced) dialog box.) Note that you can assign only one

VLAN identifier to a specific port.


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● Process Models


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● Process Models


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● Model Interfaces

Packet Formats

● The following table enumerates the packet formats used in

the Token Ring model suite.


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ICI Formats (Interface Control Information)

● The following table enumerates the interface control

information (ICI) formats used in the Token Ring model

suite.


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Token Ring Addressing and Ring Identifiers

● Each ring has a unique identifier, specified by the ring_id attribute of the tr_mac_op_v2 process model. All Token Ring MAC entities on the same ring must agree on the value of this identifier. The ring IDs can be specified to be automatically assigned to meet these requirements.

● Each MAC entity has a physical address, specified by the station_address attribute of the tr_mac_op_v2 process model. Token Ring addresses must be consecutive (no gaps in numbering) and increase in the direction of the point-to-point links along a ring. In addition, when using these models in conjunction with the Spanning Tree Bridge models, the addresses must be unique across the entire OPNET network to support correct bridge address learning. The addresses can be specified to be automatically assigned to meet these requirements.


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● A token ring network consists of a set of nodes connected in

a ring.

● The ring is a single shared medium.

● The token ring technology involves a distributed algorithm

that controls when each node is allowed to transmit.

● With a ring topology, any link or node failure would render

the whole network useless. This problem can be solved by

using a star topology where nodes are connected to a token

ring hub.

● The hub acts as a relay, known as a multi station access unit

(MSAU)

Lab 2 – Token Ring


A Shared-Media Network with Media Access Control

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● The “token,” which is just a special sequence of bits,

circulates around the ring;

● each node receives and then forwards the token.

● When a node that has a frame to transmit sees the token, it

takes the token off the ring and instead inserts its frame into

the ring. When the frame makes its way back around to the

sender, this node strips its frame off the ring and reinserts the

token.

● The token holding time (THT) is the time a given node is

allowed to hold the token.

● The THT has an effect on the utilization and fairness of the

network, where utilization is the measure of the bandwidth

used versus that available on the given ring.


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● In this lab, you will set up a token ring network with 14 nodes

connected in a star topology. The links you will use operate

at a data rate of 4 Mbps.

● You will study how the utilization and delay of the network are

affected by the network load as well as the THT.

Pay Attention and Then Start …


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NOTES:

Create Project:

● Name the project <your initials>_Token

● Name the scenario Balanced

● make sure that Create Empty Scenario

● Choose Office for Network Scale


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NOTES:

Create the Network: ● Use Rapid Configuration.

● Star Topology

● Choose Token_ring from Model List


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● Save Project


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NOTES:

Configure Network Nodes

● configure the THT of the nodes

● Select Similar Nodes

● Edit Attributes.

● Set Value Shown in figure.


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NOTES:

Configure the Simulation


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NOTES:


● Object Attributes Tab

● Office Network.*.Token Ring Parameters[0].THT Duration


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NOTES:


● Advanced Tab

● Set Scalar File Name to <your initials>_Token_Balanced


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NOTES:

Choose the Statistics

● Choose Individual Statistics - Expand

the Global Statistics hierarchy

a) Traffic Sink – check the Traffic

Received (packets/sec) box

b) Traffic Source - check the Traffic Sent

(packets/sec) box

● Expand the Node Statistics hierarchy

a) Utilization


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NOTES:

● to collect the average of the above statistics as a scalar value

by the end of each simulation run:

● Simulation menu - Statistics (Advanced)


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NOTES:

● be sure Traffic Sent and Traffic Received appeared under

the Global Statistics Probes and Utilization appeared

under Node Statistics Probes

● Set the Values for both

Traffic Sent and traffic Rec


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● we need to analyze the effect of THT on the network

performance:

● Objects menu Create Attribute Probe

● Right Click on new Attribute Probe Choose Attributed

Object expand Office Network select Node_0

● Right Click on new Attribute Probe Edit Attributes

● Save from File Menu


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NOTES:

Duplicate Scenario

● The token ring network scenario we just implemented is

balanced: the distribution of the generated traffic in all nodes

is the same. To compare performance, you will create an

“unbalanced” scenario as follows:

● 1- Scenarios menu Duplicate Scenario name

Unbalanced OK

● 2- select Nod_0 and Nod_7 by shift-Clicking

Right click Edit Attributes

Set the Interarrival time Value show in this figure.

● 3- select all nodes except Nod_0 and Nod_7

Right click Edit Attributes

Set the Interarrival time Value show in this figure.

● 4- click anywhere in the workspace to unselect objects.


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NOTES:

● 5- Click Configure/Run Simulation button:

● Name the scalar file <your initials>_Token_Unbalanced


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NOTES:

Run the Simulation

● Scenarios menu Manage Scenario.

● Value under Results column to <collect>

● OK (to run Simulation)

● After simulation completes, click close

● Save your Project


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NOTES:

View the Results

● Flow Steps in your source document to get the flowing

results.


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NOTES:

View the Results

● Flow Steps in your source document to get the results.

● test your self in OPNET simulation now.

Start as professionals…


Documents

OPNET-Chapter 3Token Ring