comnet iii - London South Bank University

Transcription

COMNET III
________________________
Getting Started Guide
______________________
Release 2.0
CACI
Call or Fax for an Immediate Response
Worldwide
CACI Products
3333 N Torrey Pines Ct
Third Floor
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92037
USA
Tel (619) 457-9681
Fax (619) 457-1184
Wash., DC Area
CACI Products
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Thirteenth Floor
Arlington, Virginia
22209
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Tel (703) 875-2900
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UK
CACI Products
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GU15 3YL UK
Tel +44 (0) 1276 671 671
Fax +44 (0) 1276 670 677
Copyright © 1998 CACI
Release 2.0
All rights reserved. No part of this publication may be reproduced by any means without
written permission from CACI.
For product information contact:
CACI Products Company
3333 North Torrey Pines Ct
La Jolla, California 92037
Telephone: (619) 457-9681
Fax: (619) 457-1184
CACI Products Division
Coliseum Business Centre
Riverside Way
Camberley, Surrey, GU15 3YL, UK
Telephone: +44 (0) 1276 671 671
Fax: +44 (0) 1276 670 677
The information in this publication is believed to be accurate in all respects. However,
CACI cannot assume the responsibility for any consequences resulting from the use
thereof. The information contained herein is subject to change. Revisions to this
publication or new editions of it may be issued to incorporate such change.
COMNET III, COMNET Baseliner, and COMNET Predictor are trademarks of CACI
Products Company. Adobe Acrobat Reader is a trademark of Adobe. STK is a registered trademark of Analytical Graphics Incorporated. STK/Pro, STK/Chains, and STK/
Connect are trademarks of Analytical Graphics Incorporated.
Table of Contents
PREFACE
....................................................................................................................
a
CHAPTER 1
Installing and Running COMNET III on a PC
1
System Requirements
.............................................................................. 1
Installation on Windows 95 and Windows NT
........................................ 2
License Activation and Running COMNET III
....................................... 4
Online Documentation
CHAPTER 2
........................................................................... 12
Installing and Running COMNET III on UNIX ........ 13
System Requirements
............................................................................ 13
Installing COMNET III under UNIX
CHAPTER 3
........
.................................................... 14
........................................................................... 25
COMNET III Sample Models
............................................
27
Loading and Running the Sample Models ............................................. 27
Sample Model Descriptions ................................................................... 29
i
ii • Table of Contents
CHAPTER 4
Modeling with COMNET III
What is Simulation?
49
.......................................................................... 49
Modeling as an Iterative Process
Seeing the Big Picture
..........................................
....................................................... 49
....................................................................... 50
Common Modeling Mistakes
............................................................ 50
How COMNET III is Unique
............................................................ 51
COMNET III Modeling Terminology
............................................... 54
Preface
Purpose
COMNET III is a performance analysis tool for computer and communications
networks. Based on a description of a network, its control algorithms and workload,
COMNET III simulates the operation of the network and provides measures of network
performance. No programming is required. Network descriptions are created
graphically through a highly intuitive interface that speeds model formulation and
experimentation.
You can predict the performance of networks ranging from simple LANs to
complex enterprise-wide systems—quickly and easily.
COMNET III supports a building-block approach where blocks are “objects” you
are familiar with in the real world. You start with a library of objects that closely
model the objects in your real networks, with one COMNET III object representing
one or more real world objects. The COMNET III object’s parameters are easily
adjusted to match the real-world object.
This object-oriented framework gives you the flexibility to try an unlimited number
of “what if” scenarios. Your recommendations will be supported by an easy-tounderstand animated picture of the network configuration you have selected.
a
b • Preface
Documentation
The documentation for COMNET III consists of three manuals:
• COMNET III Getting Started Guide
• COMNET III Reference Manual
• COMNET Baseliner User Guide
The COMNET III Getting Started Guide is for first-time COMNET III users. It
provides an overview of discrete event simulation modeling, the COMNET III
product, and details system requirements and installation guidelines.
The COMNET III Reference Guide details all aspects of COMNET III. It is an
excellent document to use to look up how various features in COMNET III work.
The COMNET Baseliner User Guide is a detailed document describing how to
import network topology and traffic files captured with various Network
Management Systems (NMS) and traffic collectors.
In addition to the manuals listed above, CACI Products Company provides white
papers on various aspects of network modeling. These papers are available from
the CACI home page at:
http://www.caciasl.com.
Technical Support
CACI Products Company provides technical support for its licensed users.
Worldwide
Europe
Phone:
619-824-5200
+44 (0) 1276.671.671
Fax:
619-457-1184
+44 (0) 1276.670.677
Email:
[email protected]
[email protected]
CHAPTER 1
Installing and Running
COMNET III on a PC
To install COMNET III on a UNIX system, see the next chapter, Installing and
Running COMNET III on UNIX.
System Requirements
Please review these PC system requirements before installing COMNET III.
Operating System
Minimum Requirements
Recommended
Windows 95 and NT
4.0
Pentium processor w/32
MB RAM, 25 MB free disk
space
Pentium Processor w/64
MB RAM, 40 MB free
disk space
1
2 • Installing and Running COMNET III on a PC
Installation on Windows 95 and Windows NT
From CD ROM
1.
Insert the COMNET III CD ROM into your computer’s CD ROM drive.
2.
After a few seconds the COMNET III AUTORUN installation screen will
appear.
If the AUTORUN installation screen does not appear, then choose Start, and
Run from the Windows desktop for Windows 95 or Windows NT 4.0. Type
X:\AUTORUN\AUTORUN for the Command Line (where X is the letter of the
CD ROM drive) and choose OK. The AUTORUN program will bring up a
dialog window with options to install COMNET III.
3.
Click on the “Install COMNET III” button. This will activate the COMNET III
installation wizard which will step you through the installation of the COMNET
III program files. A program group will be created, and icons will be placed on
the Start menu.
Installing and Running COMNET III on a PC • 3
4.
If Adobe Acrobat Reader is not already installed on your workstation, then click
on the “Install Adobe Acrobat Reader” button. This will activate the Adobe
Acrobat Reader installation wizard which will step you through the installation
of Adobe Acrobat Reader. Adobe Acrobat Reader is necessary in order to view
the online documentation. A program group will be created, and icons placed on
the Start menu. The installation will also tell COMNET III where to look for
Adobe Acrobat Reader when it is launched to view the COMNET III
documentation set.
5.
Next, click on Install COMNET III Manuals to install the COMNET III
documentation and add a Documentation folder to the program group.
License Activation and Running COMNET III
The final step is to run COMNET III and select the method of license activation.
COMNET III is run with either a hardware license key or a software license key.
Most commercial installations of COMNET III for Windows 95/NT will use a
hardware key for license activation, although some will use a software license key.
Trial licenses of COMNET III always use a software license key. Consult the
appropriate paragraph below, depending upon which version of license activation
for COMNET III that you will be using.
To activate a trial license refer to the following paragraph. To activate a hardware
license, refer to page 7. To activate a software license, refer to page 8 and to activate a university license refer to page 11.
Trial License Activation for Windows 95 and NT
For commercial customers with a 30-day trial copy, follow these instructions:
1.
After COMNET III has finished installing and creating a program group and
icons, you need to launch COMNET III to complete the installation and license
activation.
2.
When you first launch COMNET III, the Activation dialog window appears and
you are prompted to choose the method of software licensing you wish to use.
Click on the Trial software license key option and then click the OK button.
Another dialog will appear, “A license has not been issued to run COMNET III
on this computer. Would you like to register a license now?” Click on OK. The
license registration dialog window appears (see below). To obtain a License Key,
send your Hostcode (found on the License Registration dialog), your release
number and your Software Serial ID number to the CACI License Manager
according to the directions on the License Registration dialog. Once you have
received your Software License Key, enter it on the License Key field. Click the
Register button.
3.
Before you begin to build models, you will want to load the COMNET Baseliner
License Key. The COMNET Baseliner feature allows you to import network
topology and traffic files in order to help you baseline an existing network.
4.
To install the COMNET Baseliner license pull down the File menu in
COMNET III and select Import.
5.
From the sub-menu under Import, select Network Topology. This brings up the
CACI License Manager dialog box (see below).
6.
Click OK which brings up the License Registration dialog box. Enter the
COMNET Baseliner License Key in the License Registration dialog box and
click Register to establish a valid COMNET Baseliner license.
Hardware License Activation for Windows 95 and NT
The commercial version of COMNET III for Windows 95 and Windows NT is
shipped with a hardware license key which is attached to an open parallel port on
the back of the workstation.
The hardware license key for Windows NT requires that you install certain drivers
which come on the COMNET III CD ROM. Typically, for Windows 95, you will
not be required to install the drivers. For Windows NT PCs, you must be logged
onto your workstation as the administrator in order for the hardware key drivers
to be installed correctly.
1.
Place the hardware key on the parallel port of the workstation.
2.
icons, launch COMNET III to start the license activation.
NOTE: If you are running Windows 95, activation of the hardware key typically will proceed automatically and the COMNET III edit window will be
open. If so, your installation and license activation is complete. Otherwise,
continue through the following instructions.
3.
you are prompted to choose the method of software licensing you want to use.
The default is Hardware security device on... and this is the method you
typically use for a commercial license of COMNET III.
4.
Click on the pull-down box to the right of the Hardware security device on ...
and select the Windows operating system that is running on your PC.
5.
When everything is set to your PC specifications click the Install driver first
button. When the hardware key drivers are installed successfully you are
prompted with a message to reboot your PC.
6.
Once you have rebooted, you can run COMNET III.
Perpetual Software License Activation for Windows 95 and NT
For commercial customers with a perpetual software license key, follow these
instructions:
1.
activation.
2.
Click on the Perpetual software license key for... option. You will then select
the COMNET III feature set you have licensed from the pull-down list and then
click the OK button.
3.
license registration dialog window appears (see below). To obtain a License
Key, send your Hostcode (found on the License Registration dialog), your
release number and your Software Serial ID number to the CACI License
Manager according to the directions on the License Registration dialog. Once
you have received your Software License Key, enter it on the License Key
field. Click the Register button.
Table 1. COMNET III Feature Sets
Feature
Set
Code
Feature Set
Name
Basic
Product
Circuit
Switching
Module
Distributed
Software
Module
Satellite/
Mobile
Module
Application
Profiler
11
Basic
Product
Yes
------
------
------
------
1100
Enterprise
Modeler
Package
Yes
Yes
Yes
Yes
Yes
1101
Update for 1.4
customers
Yes
Yes
Yes
------
------
1102
Distribute
Software
Package
Yes
------
Yes
------
------
1103
Mil/Sat
Package
Yes
Yes
------
Yes
1104
Client/Server
Package
Yes
------
Yes
------
Yes
1199
Model Viewer
------
------
------
------
------
4.
5.
6.
University License Activation for Windows 95 and NT
For university customers, follow these instructions:
1.
activation.
2.
When you first launch COMNET III, the Activation dialog window appears.
Enter your Software Serial ID Number in the appropriate field. Click on the
OK button.
3.
release number and your Software Serial ID Number to the CACI License
The following documents will be installed when you choose Install COMNET III
Manuals from the COMNET III Installation CD. The manuals can also be
downloaded from the CACI website (http://www.caciasl.com). Once installed,
they can be launched from the Windows Start menu, by selecting the
Documentation folder under the COMNET III program group.
1.
COMNET III Getting Started Guide (C3START.PDF)
2.
COMNET III Reference Manual (COMNET.PDF)
3.
COMNET Baseliner User’s Guide (BASELINR.PDF)
The COMNET III Getting Started Guide gives an introduction to COMNET III and
describes how to install COMNET III.
The COMNET III Reference Manual contains information on all aspects of
COMNET III.
The COMNET Baseliner User’s Manual details the use of COMNET Baseliner,
which allows for the import of network topology information from various network
management consoles.
CHAPTER 2
Installing and Running
COMNET III on UNIX
System Requirements
Please review these system requirements before installing COMNET III.
Operating System
Minimum Requirements
Recommended
Solaris 2.5, or SunOS
5.5
SPARC Station w/32 MB
RAM, 50 MB free disk
space
SPARC Station w/64
MB RAM, 50 MB free
disk space
HP-UX 10.2
HP 700 Series w/32 MB
space
HP 700 Series w/64 MB
space
SGI-IRIX 6.3
32 MB RAM, 50 MB free
disk space
64 MB RAM, 50 MB
free disk space
13
14 • Installing and Running COMNET III on UNIX
Installing COMNET III under UNIX
In the first part of the installation, the COMNET III programs, system libraries, and
sample models are installed in a single program directory. It is not required that
root perform the installation, although this will be the case if you choose to install
in a directory that requires root access. At many installations, a system administrator performs the first part of the installation.
In the second part of the installation, individual COMNET III users set up their
own model directory. At many single user sites, the same individual performs both
parts of the installation.
Part 1: Building the Program Directory
1.
Change to the directory where you want to install the COMNET III program
files. You must have write permission in this directory.
2.
If you have downloaded the COMNET installation from the web, uncompress
the file as follows:
uncompress Comnet20-commercial-solar.tar.Z
The name of the file may be different, depending on which platform you are
installing COMNET III on. Now skip to step 4.
If you received COMNET III on a CD ROM, insert the COMNET III CD ROM
into the CD ROM drive and mount it as follows:
/usr/bin/ps -ef | /bin/grep vold
The Volume Manager is running if you get a response similar to:
root 28158 16925 7 13:14:27 1 0:06
/usr/sbin/vold
In this case the CD is automatically mounted. If the Volume Manager is not
running, become root and mount the CD manually:
mkdir -p /cdrom/comnetdistr
mount -F hsfs -r <Device Name> /cdrom/comnetdistr
Device Name is typically /dev/dsk/4s0. On HP-UX become root and
mount the CD manually:
Installing and Running COMNET III on UNIX • 15
mkdir /comnetdistr
/etc/mount <Device Name> /comnetdistr -t cdfs
3.
Copy the tar file, Comnet-<Platform Name>, to your installation directory.
4.
Untar the file:
tar xvf Comnet20-commercial-solar.tar
The name of the file may be different, depending which platform you are
installing COMNET III on.
5.
Remain in the COMNET III installation directory where you just untarred the
comnet tar file and run the COMNET III install script by typing:
./c3install
The ./c3install script creates the script files comnet, simdraw, and
c3batch. The comnet and simdraw script files can be edited to include
additional X-Windows options used to control the appearance of X-Windows
applications. X-Windows controls can be passed as -xrm options on the
command line in each script file. The c3batch script is used to run a simulation
in batch mode. Just type c3batch <model name>. For example, c3batch
ACME, runs the model ACME.c3. The c3install script also sets the
permission on the COMNET III system libraries contained in the ObjLibs and
SG2Libs directories so that only the owner has write access to these directories.
6.
Here you will have the option of installing the Adobe Acrobat Reader. The
Reader is required to view the COMNET III online documentation.
Part 2: Activating COMNET III
Trial License Activation for COMNET III on UNIX
For commercial customers with a 30-day trial copy, follow these instructions:
1.
Start COMNET III by typing comnet at the command prompt. When you first
launch COMNET III, the Activation dialog window appears and you are
prompted to choose the method of licensing you wish to use.
2.
Click on the Trial software license key option and then click the OK button.
3.
license registration dialog window appears (see below). Enter the Software
License Key found in the upper-right corner of your letter included with your
distribution package. Click the Register button.
4.
1.
2.
click Register to establish a valid COMNET Baseliner licens
Hardware License Activation for COMNET III on UNIX
The commercial version of COMNET III for UNIX is shipped with a hardware
license key which is attached to an open serial port on the back of the workstation.
1.
you are prompted to choose the method of licensing you want to use.
The default is Hardware security device on... . This is the method you typically
use for a commercial license of COMNET III.
2.
Click on the pull-down box to the right of the Hardware security device on ...
and select the serial port you have placed the hardware key on. See the
ReadMe file for platform dependent guidelines that will help you choose the
correct option.
3.
When everything is set to your workstation’s specifications, click the OK
button. When the hardware key drivers are installed successfully you are
prompted with a message to reboot your computer.
4.
Once you have rebooted, you can run COMNET III.
Perpetual Software License Activation for COMNET III on UNIX
For commercial customers with a perpetual software license key, follow these
instructions:
1.
After COMNET III has finished installing, launch COMNET III to complete
the installation and license activation.
2.
Click on the Perpetual software license key for... option. You will then select
the COMNET III feature set you have licensed from the pull-down list and then
click the OK button.
TABLE 2. COMNET III Feature Sets
Feature
Set
Code
Feature Set
Name
Basic
Product
Circuit
Switching
Module
Distributed
Software
Module
Satellite/
Mobile
Module
Application
Profiler
11
Basic
Product
Yes
------
------
------
------
1100
Enterprise
Modeler
Package
Yes
Yes
Yes
Yes
Yes
1101
Update for 1.4
customers
Yes
Yes
Yes
------
------
1102
Distribute
Software
Package
Yes
------
Yes
------
------
1103
Mil/Sat
Package
Yes
Yes
------
Yes
1104
Client/Server
Package
Yes
------
Yes
------
Yes
1199
Model Viewer
------
------
------
------
------
3.
release number and your Software Serial ID number to the CACI License
4.
5.
6.
University License Activation for COMNET III on UNIX
For university customers, follow these instructions:
1.
activation.
2.
When you first launch COMNET III, the Activation dialog window appears.
Enter your Software Serial ID Number in the appropriate field. Click on the
OK button.
3.
release number and your Software Serial ID Number to the CACI License
Part 3: Building a Model Directory
This part of the installation should be performed by each individual COMNET III
user after the COMNET III program directory has been established.
1.
Create a directory for your COMNET III model files. As an example, you
could create the /home/myfiles directory. Important note: whether you
use an existing directory or you are creating your own directory, you must have
write permission in the directory that you use for your model files.
2.
Copy the samples directory to your model directory. For example:
cp -R /home/bin/comnet3/samples /home/myfiles
3.
To make it convenient to run the COMNET III programs, add the COMNET III
program installation directory (in this example, /home/bin/comnet3) to
your path.
4.
To run COMNET III, change to your model directory and run the comnet
script file:
cd /home/myfiles
comnet
If you did not include the program installation directory in your path, then you
would need to type the full path to the comnet script file:
cd /home/myfiles
/home/bin/comnet3/comnet
This completes the COMNET III installation. The next two paragraphs provide
additional information for users who want to add objects to the object libraries in
the ObjLibs directory or who want to add icons to the graphics libraries in the
SG2Libs directory.
Object Libraries
To add objects to the COMNET III object libraries, you must have write permission in the ObjLibs directory and write access to the libs.dat file (if it exists)
in the ObjLibs directory. Only the owner of the ObjLibs directory is granted
write permission by the c3install program. If you do not have write permission to the ObjLibs directory, ask your system administrator (or whoever is the
owner of the ObjLibs directory) to change the permission level or add the objects
you want in the library.
If you do not have write access to the ObjLibs directory and the owner does not
change the permission levels nor add the objects for you to the library, you can
make your own local copy of the system libraries in a directory where you do have
write access. If you choose this approach be forewarned: keeping local copies of
system libraries creates an extra burden for you when future releases of COMNET
III are installed, because you need to make sure that you update your local copies
of certain files in the system libraries. Suppose you want your own copy of the
system libraries in the directory /home/mylibs. You need to copy both the
ObjLibs and SG2Libs directories and their contents to /home/mylibs. For
example,
cp -r /home/bin/comnet3/ObjLibs /home/mylibs/ObjLibs
cp -r /home/bin/comnet3/SG2Libs /home/mylibs/SG2Libs
To tell COMNET III to look for the system libraries in /home/mylibs instead of
the program installation directory, set the environment variable /SIMLIBS to
/home/mylibs. For example
setenv SIMLIBS /home/mylibs
Note that it is only necessary to set SIMLIBS if you want to use system libraries
that are not in the program installation directory (i.e., /home/bin/comnet3 in
this example).
usermsg.sg2
Message Sources
userrem.sg2
Remote Pads, Sockets
userres.sg2
Response Sources
userses.sg2
Session Sources
usergen.sg2
Virtual Circuits
The above files do not exist until you import a bitmap using File/Import or you create
them using SIMDRAW. The files contain only user-provided icons. The CACIprovided icons are in files with names of the form caci*.sg2.
The following documents are distributed with the COMNET III installation:
1.
COMNET III Getting Started Guide (C3START.PDF)
2.
COMNET III Reference Manual (COMNET.PDF)
3.
COMNET Baseliner User’s Guide (BASELINR.PDF)
The COMNET III Reference Manual can be opened from the Help menu by
selecting Reference Manual. The COMNET III Reference Manual contains
information on all aspects of COMNET III. All other documents must be opened
from within the Adobe Acrobat Reader.
The COMNET III Getting Started Guide gives an introduction to COMNET III and
describes how to install COMNET III.
The COMNET Baseliner User’s Manual details the use of COMNET Baseliner,
which allows for the import of network topology information from various network
management consoles.
COMNET III Sample
Models
CHAPTER 3
Loading and Running the Sample Models
Once you have started COMNET III, you can load the model you wish to run from
the File menu. To begin, choose File/Open from the menubar. Use the Open dialog
to browse for the sample model you wish to load and click on Open. By default,
these models will be found under your COMNET system directory, in the
Models\Samples sub-directory. The model will load and its layout appears on the
screen.
The Simulate menu can be used to adjust the model's simulation parameters and to
start and halt the simulation. To run the model, choose Simulate/Start Simulation.
•
•
•
•
The tool palette on the left will be grayed out and disabled.
The simulation clock will appear at the bottom in the status bar.
The simulation starts and the clock starts counting time into the simulation.
The animation reflects frames being transmitted and packets being received by
nodes.
27
28 • COMNET III Sample Models
While the model is running you may:
• Use the Simulate/Animate menu to turn animation on and off, set the speed of
the animation, or schedule animation to turn on or off at a future time.
• Use the Simulate/Trace menu to turn tracing on or off, or to specify whether
execution trace statements appear on the screen or go to a file. The trace statements
appear in the status box at the bottom of the screen. You can also specify that you
would like to single-step through the execution.
• Double click on any link or node icon and bring the device up or down, to simulate
a link or node failure. You can also schedule a failure or recovery event at some
time in the future.
After the model has completed the simulation run, choose Browse Reports from the
Report menu to look at the performance measures of the model.
More detail on the sample models is available from the Sample Models Guide, an
html document available online.
COMNET III Sample Models • 29
Sample Model Descriptions
3TIER.C3
3TIER.C3 is a model of a 3-tier client/server application. It demonstrates the use of
a dynamically assigned message text to convey information that is used by various
tiers in a multi-tier client/server application. The message text is assigned dynamically
by constructing strings using Assign Variable commands. Information is then
extracted from the message text at the receiving end using expressions and the intrinsic
procedures SUBSTR and POSITION.
ALCANET.C3
This is a model of a PTT network that connects the US to Europe. The model
mainly models voice communication over Time Division Multiplexing (TDM)
links. There is one data source defined by using the COMNET III session source.
Additionally, the trace to screen feature is turned on to show the call connection
and the message session on screen.
BANK.C3
This is a simple model of a bank Automatic Teller Machine transaction processing
network containing many of the major elements of this type of network. This network is a small bank with branches in Boston and Washington DC and a Teller
Machine transaction processing center in New York. The Teller Machines in each
area are on a 4 MB Token Ring Local Area Network (LAN). Each LAN is connected to a Cisco 7010sp router that is connected, in-turn, by a point-to-point link
to the router at the New York processing center. There is a backup connection
between the routers in Boston and Washington DC through which packets can be
rerouted if one of the backbone links goes down. The point-to-point links have a
bandwidth of 9.6 kbps. The model is set up to represent a busy peak of Teller
Machine usage. Each group node is set to generate an average of 120 transactions
per minute by using an average interarrival time on the traffic generator of 0.5 seconds. We have also added another single node in each area where we have a transaction generator with an interarrival time of 30 seconds. When we come to look at
the reports we will see the response time for these single transactions as they contend with the traffic generated from the group node.
BANK_2
This model is a variation of the ‘Bank’ model. In this example a WAN Cloud has
replaced the point-to-point links of the previous model. The WAN Cloud is used to
model a Frame Relay WAN link between the central host and the remote sites.
CALLCEN.C3
This model simulates a transaction processing application in a client/server
environment. Local nodes send a message to the server. The server responds to the
first incoming message and sends a response message back to the nodes. The
nodes wait until they receive the server's first response, then send another message
to the server. When the server receives the second update message from the nodes,
it analyzes the data, writes the data to a customer file, and then sends a broadcast
message to all the nodes that it has updated the customer file.
CSTELCOM.C3
This model uses user-defined packet routing tables to route data along a specified
path. The idea is to provide alternate routing for the "WS" node along links "3A"
and "3B", and for the "COMMS" node along links "7A" and "7B". The user
defined packet routing protocol defined under the backbone properties uses a "First
Available" choice to determine the primary route. If the first choice is unavailable,
then another choice is made among the remaining routes. If a route is always available, then no other route will chosen. In this model, the first primary route is
always available. Therefore, the second primary route will never be used, and traffic will never be split among links 3A and 3B, and 7A and 7B.
D7ASC.C3
This model shows client/server applications and traffic. Workstation client nodes
request data from a server. The server processes the data request, reads a data file,
and sends the data file back to the workstation client node. The client requests use
a weighted list destination list to insure that 70% of the requests go to the "EServer" and 30% of the requests go to "T-Server".
DEMO1.C3
This model shows a simple client/server application using just message and
response sources. The model also shows the use of the Group Node to represent
multiple nodes graphically as one node. “Workgroup 1”, “Workgroup 2”, and
“Workgroup 3” each represent 30 separate client nodes. When the simulation is
run, 180 total client nodes will be sending database requests to the “Host” database
server. The “Host” database server responds to incoming messages and sends back
a message. This response message could represent an acknowledgment or a data
transmission.
DEMO 2.C3
This model shows a model of a voice network connecting NATO HQ to the
Pentagon, London, Paris, and Frankfurt. The network has been set up to handle
both voice and data traffic, but only voice traffic has been defined. Three different
classes of voice traffic have been defined at each site representing 9.6 Kbps, 32
Kbps, and 64 Kbps.
DEMO2A.C3
This is the same model as DEMO2.C3, with higher levels of voice traffic added.
DEMO3.C3
This model shows two client nodes “A” and “B” establishing multiple sessions
with node “C”. During each session, a number of messages will be sent from the
source node to node “C”. Node “C” then responds and sends a message back to the
source node. The purpose of the model is twofold:
1. To model “adaptive” routing through the use of COMNET III’s routing penalty tables. A packet routing penalty table has been set up to provide an
alternate route selection when link delay reaches 5 seconds. This is seen at
the 500-second point of the simulation, when link “A-B” shows traffic utilization. At this point there is now a 5-second queuing delay at link “A-C”
and “B-C”.
2. To show that multiple sessions can be established between source and destination before a session has completed.
DEMO3A.C3
This is an expansion of DEMO3.C3.
DEMO4.C3
This model is an expansion of the DEMO3.C3 model. The model shows how subnets can be used to provide a hierarchical representation of different segments of a
network. In this model, the subnet is also used to allow the “Ethernet” subnet to use
a different routing protocol from the main protocol. This means that all traffic
routed through the “Ethernet” subnet uses a RIP Minimum routing protocol, while
all traffic at the top, or backbone level uses a Minimum Penalty routing strategy. In
addition to the different routing algorithms used, a different transport protocol is
employed for the “Request” traffic inside of the “Ethernet” subnet. A special “LAN
transport” protocol has been defined to transport data that originates and terminates
inside of the subnet. For all “Inquiry” traffic that will terminate at Node “C” on the
backbone, a “Generic” protocol will be used.
EX-1.C3
This model simulates a LAN Email application and a LAN client/server session. A
message and response traffic source is attached to each node in the LAN, and generates
Email traffic to a random neighbor. When a node receives an Email message, it
generates a response message which is sent back to the originating node. Each client
node also establishes a periodic session with the server.
EX2.C3
This model expands on EX-1.C3. Whereas EX-1.C3 modeled a LAN, EX2.C3
models a WAN. The model also introduces the concepts of Subnets and Transit
Nets. Each subnet (NW, NE, SE, SW) represents a LAN. The transit network
which represents the backbone is defined as "SMDS".
Each subnet is comprised of local Email messages and responses to local neighbors
within the subnet, as well as the implementation of an Application Source to
represent a client/server FTP request, transfer data, and write data. The application
sources use a combination of Local and Global commands. Global commands can
be applied to any node in the model, while local commands can only be applied to
the node they were created on. Through the "FTP Request" application source, the
client nodes will send an FTP request to a random server in any of the subnets and
wait for a response. When a response comes back, the client will process and then
write to general storage. The "server app" will wait for a client FTP request,
process, read data, and then send data back to the client.
The transit network represents the WAN backbone and will route traffic among the
subnets. Each router in the transit network has a message source which will
simulate the updating of routing tables on the routers.
FRTEST.C3
This simple model demonstrates the "Assume direct unconstrained VC" capability
of the WAN Cloud. When using a WAN Cloud you can assume that any message
entering the Cloud will be routed to the proper exit point whether or not a virtual
circuit has been defined between the exit and entry points. Note that you could also
create a virtual circuit (VC) between two access points on a Cloud, and use the
"Multiply transit cloud along VCs". This would potentially block a message from
exiting the cloud if there were no virtual circuit pathway connecting the entry point
to the exit point.
JBA2.C3
This model demonstrates how to use application sources from the distributed software module to model client/server database applications. Local commands are
used to simulate a client making an account inquiry and having the application
screens on the client machine updated. This model is an excellent example of a
Windows or Windows-like accounting application and how it behaves on a client
system. Requests are made to an application server, which in turns makes requests
of a database server. The database server responds to the application server which
in turn responds to the client.
MELCO.C3
This model shows a client/server application using a combination of message
sources as server request messages, and an application source on the file server that
processes the incoming message, reads a file, and sends a file back to the node
making the server request.
PREEMPT.C3
This model is a demonstration of priority preemptive port buffers.
1. A low priority message dumps 10 packets at a time into a buffer.
2. A high priority message dumps 1 packet slightly later.
3. The port output buffer from source to link is 10 packets.
3a. Preemption is a port-buffer behavior.
4. The link is slowed down to transmit 1 packet/second.
CHAPTER 4
Modeling with
COMNET III
What is Simulation?
Broadly defined, a simulation model is a simplified representation of a system,
enabling the system’s properties and behavior to be studied. Because the model
represents a system, it can be manipulated in ways that would be difficult, expensive, or impossible to perform on the actual system. Thus, simulation is an excellent way to test proposed systems or to evaluate existing systems.
Modeling as an Iterative Process
You will find that over the course of a simulation study, you will refine the model or
models many times. The end result may look different than when you began. The
scope of a project often changes which requires the basic model to change. The
modeling process then becomes an iterative process.
49
50 • Modeling with COMNET III
Seeing the Big Picture
As you develop your model, it is important to not get bogged down in the detail of
modeling every event that occurs on every application at every node in your model.
If you are not careful, you may find yourself trying to emulate an existing network
instead of simulating it.
Emulating a network with COMNET III is undesirable. The reason is rooted in the
difference between analytical modeling and discrete event modeling. In analytical
modeling you are using a formula to make one calculation to obtain a performance
measure. In discrete event simulation you observe events as they happen over
time, and collect performance measures to calculate results. Typical performance
measures of interest include utilization levels, waiting times, and queue sizes.
Thus, for any network with many nodes and traffic sources, this can create an
unnecessarily large and detailed model that takes a long time for a discrete event
simulation tool to simulate. The output data produced is difficult to interpret
because too much information is being gathered during the simulation run.
Therefore, when using a discrete event tool like COMNET III, it is best to model
one or two typical segments of the network in detail and then analyze the results.
From the information gathered, it will be easy to extrapolate the results to reflect a
department in an office, and then to reflect the office itself. Thus, an entire office
or region could be represented by a single “super” node and “super” traffic source.
In this way, you can run the simulation in a short time; the results will be meaningful and more realistic than those from an analytical model.
Common Modeling Mistakes
Not defining an attainable goal
Modeling is a way to achieve a goal; it is not the goal itself. You must set clearly
defined, attainable objectives for your simulation. As an example, suppose you
wanted to determine the average end-to-end traffic delay across your the network
backbone. To answer this question, you would build a model that would represent
just the network backbone along with backbone traffic. There would be no need to
model any network segments that are not in the backbone.
Modeling with COMNET III • 51
Too much detail
A model is a simplified representation of a system. Focus on only those features of
the system that are important to the end result.
How COMNET III is Unique
COMNET III gives you unparalleled ability to rapidly build a model of a network,
simulate it, and generate output data in meaningful reports. This allows you to
easily build a model of an existing or proposed network using real-world data, and
then study its behavior in the simulation.
Here are some features that distinguish COMNET III from other network modeling
and performance prediction tools:
Hierarchical, Event-Driven Simulation
COMNET III provides hierarchical and event-driven simulation capabilities that
had been previously unavailable for modeling large-scale systems.
Point, Click, Model
COMNET III’s interface is powerful, flexible, and easy to use. COMNET III
allows you to drag, drop, and connect objects graphically to build models of voice
and data communication networks. No programming is necessary.
Any time you want to change a model, simply modify the object you want to
change or drag a new object from the tool palette, drop it into the existing model,
and connect it appropriately. No coding or recompiling is necessary.
Complex Scheduling with the Distributed Software Module
The Distributed Software Module (DSM) allows COMNET III to model the message traffic generated by a network application, as well as the behavior of the application itself. COMNET III does this by taking into account the interaction
between the application and the node that is processing it. In this way, you get both
message traffic and application performance information.
Enhanced Multi-Protocol Modeling
COMNET III provides the capability to simulate multi-protocol layering within a
model. This means that COMNET III can accurately model TCP/IP over ATM.
For example, a message may be generated on a TCP/IP network and routed to
another workstation across the country running on TCP/IP. In between the two
workstations is an ATM backbone over which the message is sent. COMNET III is
able to generate the initial message and packetize it over the TCP/IP network.
When the message gets to the ATM backbone, the message is further segmented
into ATM cells and sent over the ATM backbone where it is re-assembled into
TCP/IP packets which are then sent on to the receiving station.
Importing Network Topology and Traffic Data Through
COMNET Baseliner
COMNET Baseliner has the unique ability to import both network topology information gathered from network management discovery tools and captured network
traffic data from network sniffers, RMON, and RMON II probes. See the
COMNET Baseliner User Guide for more information.
COMNET Baseliner currently imports topology data from these tools:
•
•
•
•
•
•
•
•
•
•
•
•
Cabletron SPECTRUM
Castlerock SNMPc
Digital POLYCENTER
HP NetMetrix
HP OpenView
IBM Netview for AIX
NAC MIND
NAI Expert Sniffer Network Analyzer
NAI Distributed Sniffer System
NetSuite
Files which support the CACI API format
Additional systems added regularly
Network traffic data can be imported from these tools:
• 3COM LANSentry
•
•
•
•
•
•
•
•
Compuware EcoSCOPE
HP Netmetrix
NetScout Systems NETscout Manager
NAI Distributed Sniffer System
NAI Expert Sniffer Network Analyzer
Most RMON tools
User-defined traffic files
Additional systems added regularly
Rapid Model Development
COMNET III’s graphical interface allows you to rapidly develop models. Simply
point, click, and drag network objects from the tool palette and drop them onto the
canvas. Connect them, add at least one traffic source, and click the start simulation
button. No programming or compiling is required.
Multi-platform support
COMNET III runs on Windows NT, Windows 95, Solaris, HP-UX, and SGI IRIX.
Many Ways to Display Output
COMNET III collects a great deal of data during a simulation and offers you several ways to view it. While the simulation is running, you can view data flow
dynamically through real-time plots and snapshot reporting traced to the screen.
For example, at any point in time, you can see how heavily any or all links are
being used. After the simulation is complete, you can view the data in a variety of
reports. For example, you can see the total utilization for each link for the entire
simulation.
COMNET III Modeling Terminology
Nodes
A node in COMNET III models switches, hubs, routers, end systems, pads and
general network components. Specific types of nodes are processing nodes, router
nodes, switch nodes, and computer group nodes.
Links
A link is an object to which nodes may be connected by arcs. A link represents the
medium through which nodes send and receive data. The types of links include
Aloha, CSMA, CSMA/CA Wireless LAN (IEEE 802.11), CSMA/CD, DAMA
(Demand-Assigned Multiple Access), FDDI and Priority FDDI, Point-to-Point,
Polling, Priority Token Ring, Token Passing, and parameter sets for SONET and
ISDN links.
Traffic Sources
Traffic sources are objects that act as network traffic generators simulating the
flow of data over the network. Different types of traffic sources are used to model
voice and data communications.
WAN Clouds
The WAN cloud object provides an abstract model for public or private data networks. It provides a higher level abstraction than is available if modeling the physical nodes and links of the network. The WAN cloud object is an alternative for
modeling WANs instead of explicitly modeling the topology with routers and
links.
Subnets
The subnet object serves two purposes. First, it manages the display of a large network. Rather than having one flat picture that has either many small icons or
requires extensive scrolling, various sites or domains in the network can be placed
in a subnetwork which is represented by one icon at the backbone level. Second,
you can use different subnetworks to represent different domains in a network
which operate under different routing protocols.
Transit Networks
The transit network object is an intermediate network that interconnects a collection of nodes. It provides an additional level of segmentation and reassembly at the
boundaries of the transit network. It is called a transit network because its primary
purpose is to model packets that enter on one side of the net, flow through the net,
and finally exit on the other side of the net. In other words, it models packets transiting a network.
Canvas
The work area in COMNET III from which you build and run models.
Tool Palette
Select object(s)
Diagonal arc
Processing node
Router
Transit network
Cloud
Zoom into work area
Horizontal/vertical arc
Computer group
Access point
Subnet
STK link
Cloud VC
Point-to-point link
CSMA/CD link
Token-passing link
Message source
Response source
Application source
Call source
Background shape
Background map
Session source
Source socket
Remote link
Background text

comnet iii - London South Bank University

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