MRN_81

Release 8.1 OPNET Modeler

Release Notes

These release notes provide an overview of the differences between OPNET Modeler re-lease 8.1 and the previous release. If you are upgrading from a previous release, youshould review this document.

Contents

1

8.1 Release Description

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.1 System Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Flow Analysis Enhancements

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.1 Configuring Routing Protocols on Loopback Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . 42.2 Converting Link Utilizations to Traffic Flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.3 Flow Analysis Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.4 Permission Errors When Launching IP Reports on Windows 2000 . . . . . . . . . . . . . . . . 53

Router Configuration Import Enhancements

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

NetDoctor Enhancements

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

ACE Enhancements

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75.1 New Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85.2 Expanded Tutorials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Statistic Reporting Enhancements

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

Some IS-IS Support Temporarily Removed

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

ERP Network Assessment Module (ENAM) Unsupported

. . . . . . . . . . . . . . . . . . . . . . . . 89

KP Changes

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99.1 op_prg_list KPs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99.2 op_pk KPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99.3 op_stat_obj_reg() . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 910

Model Library Enhancements

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 910.1 ATM Enhancements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 910.2 PNNI Enhancements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1010.3 Application Model Enhancements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1010.4 TCP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1110.5 IP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1110.6 Hybrid Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1210.7 OSPF. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1210.8 BGP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1210.9 EIGRP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1310.10 DOCSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1310.11 Wireless LAN (WLAN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1310.12 MPLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

OPNET Modeler 8.1Release Notes

2

OPNET Modeler

Release Notes

Release 8.1

Part number: D00214Version: 2

© 2002 by OPNET Technologies, Inc.All rights reserved.This information is subject to all restrictions set forth in the Modeler documentation.

11

Model Behavior Changes in 8.1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1411.1 For Models Using BGP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1411.2 For Models Using EIGRP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1411.3 For Models Using IP Multicasting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1511.4 For Models Using TCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1511.5 For Models Using ATM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1511.6 For Models Using PNNI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1611.7 For Custom Applications Using the ACE Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1711.8 For Models Using Hybrid Simulation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18


Release Notes

3

1 8.1 Release Description

Modeler version 8.1 is a significant new release, offering substantial new functionality, in-cluding:

• Major enhancements to the FlowAnalysis module for both IP and ATM, including:

- new supported protocols

- extensive reports

- ability to convert utilizations to traffic flows

• Major enhancements to the MVI module in the area of Cisco router configurationimport

• MVI module support for importing traffic flows from NetScout nGenius

• New standard rules provided with the NetDoctor module

• Significant new features in the ACE module for predicting application perfor-mance, plus new tutorials and usage examples

• Enhancements to the following models: ATM, PNNI, Applications, TCP, IP, Hy-brid Simulation, BGP, EIGRP, DOCSIS, MPLS, OSPF, Wireless LAN, and NetDoc-tor Rules

This release also incorporates fixes for some reported software problems in the precedingrelease.

1.1 System Requirements

Be sure to check the latest system requirements on the OPNET website, at:

http://www.opnet.com/support

2 Flow Analysis Enhancements

The Flow Analysis module now supports expanded analyses of IP and ATM networks.Routing flow analyses and failure impact analyses model the behavior of the followingprotocols. Multiprotocol networks are supported, as is PNNI-to-VNN interworking. Notethat the IP and ATM Flow Analysis engines are separate, so combined IP/ATM routing isnot supported in Flow Analysis. It is, however, supported in discrete event simulation.


4

OPNET Modeler

Release Notes

Release 8.1

In addition to expanded protocol support, the Flow Analysis module has the followingnew capabilities:

•

IP Report Manager

—dynamically creates approximately 100 different reports atuser request

•

IP flow analysis

—performs routing flow analysis and delay analysis, and com-putes statistics. Problems that occur are reported in a separate IP flow analysis er-ror log.

•

ATM flow analysis

—includes the following enhancements:

- VNN modeling

- PNNI and VNN inter-working

- SVC modeling

- Reporting—also reports on unroutable VCs and available bandwidth

- Demand sequencing

- Per-node Customizable Call Admission Control (CAC)

- Point-to-Multipoint VCs

For a complete description of these capabilities, refer to the Flow Analysis

User Guide.

2.1 Configuring Routing Protocols on Loopback Interfaces

IP Flow Analysis is unable to compute a route for a conversation pair if the loopback in-terface on the source or destination node is not reachable. Similarly, route browsing willfail in IP flow analysis if the loopback interface on one of the selected nodes is not reach-able. The loopback interface may be unreachable because it does not have routing proto-cols configured on it.

OPNET provides a command (Protocols

➧

IP

➧

Configure Routing Protocols on LoopbackInterfaces…) to help you configure IP routing protocols on loopback interfaces. This com-mand performs a one-time configuration of the loopback interface. If you modify the con-figuration of one or more devices in OPNET prior to running an IP flow analysis, you mayneed to execute this command again. Alternatively, you can configure IP Flow Analysis to

Flow Analysis Supported Protocols

Network Technology Protocols

IP BGPEIGRPIGRPIP routingOSPFRIP

ATM Distance vectorPNNI/VNN


Release Notes

5

automatically execute this command while preparing to run the analysis. Refer to section

IP.4 Configuring and Running a Flow Analysis

(procedure step 4) in the Flow Analysis

UserGuide

for details.

2.2 Converting Link Utilizations to Traffic Flows

The Flow Analysis module allows you to convert the link utilizations in a network to traf-fic flows. This can be useful because traffic flows, unlike link utilizations, respond toevents during a simulation and thus can be rerouted by the routing protocols in use. Touse this feature, choose Traffic

➧

Convert Link Utilizations to Flows. For more details, referto the OPNET 8.1

New Features

document.

2.3 Flow Analysis Limitations

The following software problems (SPRs) have been reported in the 8.1 release of FlowAnalysis and are currently being investigated.

2.4 Permission Errors When Launching IP Reports on Windows 2000

If you are running OPNET on Windows 2000 from an account without administrator priv-ileges, you may notice errors when attempting to launch the IP Report Manager. This hap-pens because Windows 2000 prevents OPNET from writing to its system directory fornon-administrator users.

If you installed OPNET on a Windows 2000 machine and will be using it from an accountwithout administrator privileges, you must change file access permissions for the follow-ing directories:

<opnet_dir>

/8.1.A/sys/reports

<opnet_dir>

/8.1.A/sys/lib

To change permissions…

1) Navigate to

<opnet_dir>

/8.1.A/sys

.

2) Right-click on the directory name (

reports

or

lib

) and select “Properties”.

Known Flow Analysis Protocol Limitations

SPR Description

19400 IGRP works on CIDR networks, although it doesn’t support CIDR

19401 RIPv1 works on CIDR networks, although it doesn’t support CIDR

20121 Flow Analysis does not support BGP confederations

6

OPNET Modeler

Release Notes

Release 8.1

3) Select the “Security” tab.

4) Click on the “Users” group in the name table.

5) Click on the Allow column for the “Full Control” entry in the Permissions table.

6) Click on “Apply”.

3 Router Configuration Import Enhancements

RCI now imports the following information:

• BGP community lists and route maps

• EIGRP route maps and new model attributes

• Standard and extended access lists

• Prefix lists

• Per-interface bandwidth and delay parameters (interface metrics)

• Policy-based routing

• Packet filters on interfaces

• EtherChannel

In addition, RCI’s import of redistribution attributes has been enhanced and a loggingmechanism (controlled by the

router_import_logging

preference) for skipped com-mands and other import information has been added.


Release Notes

7

4 NetDoctor Enhancements

The following standard rules have been added to the NetDoctor module.

Simulation Requirements is a new category that includes rules that are required for a Dis-crete Event Simulation or Flow Analysis, but may not be required for a valid real-worldscenario. If a rule in this category is not followed, your simulation may generate errorseven though your model represents a valid network configuration.

5 ACE Enhancements

The Application Characterization Environment (ACE) module now has several new capa-bilities and expanded documentation.

New Standard NetDoctor Rules

Rule Suite Rules

EIGRP Routing Duplicate Router ID within ASExplicit Neighbor Not In Same ASExplicit Neighbor Not PeerExplicit Neighbor Without Passive InterfaceInappropriate Variance ValueInconsistent Active Timer within ASInvalid Interface For Explicit NeighborInvalid Route Filter in AS ConfigurationInvalid Route Filter on InterfaceInvalid Route Map NameMismatched Metric CoefficientsNot Enough Bandwidth Available to EIGRP

BGP Routing Invalid AS Path ListInvalid Prefix ListInvalid Update Source for Neighbor

IP Routing No Routing Protocol On InterfacePeers With Inconsistent Routing Protocols

IS-IS Routing Inconsistent Circuit Type

OSPF Routing Inconsistent Reference BandwidthReference Bandwidth Too Low

Route Map and ACLs Ineffective ACLIneffective Prefix ListInvalid ACL for Packet FilterInvalid Route Map for Policy RoutingIneffective Statement in Route Map

Simulation Requirements Loopback Not ReachableDuplicate AS Definition for EIGRP

8

OPNET Modeler

Release Notes

Release 8.1

5.1 New Capabilities

Several significant capabilities have been added to the ACE module.

•

Treeview

window has been reorganized and now includes timeline graphics.

•

QuickPredict

lets you vary several network parameters (such as bandwidth andlatency) and immediately see what effect the change has on application perfor-mance.

•

QuickRecode

lets you investigate how changes to an application will affect its per-formance.

•

ACE Model Wizard

helps you configure applications when importing an ACEtrace file into a new or existing network model.

The first three features are described in the OPNET 8.1

New Features

document, accessibleby choosing Help

➧

What’s New in 8.1. The Model Wizard is described in the

Reference

chapter of the ACE

User Guide

.

5.2 Expanded Tutorials

The two ACE tutorials previously found in the ACE

User Guide

have been removed. Theyare replaced by four new ACE tutorials and five examples of typical applications of ACE.To view the new tutorials and examples, choose Help

➧

Online tutorial.

6 Statistic Reporting Enhancements

You can now visualize throughput and utilization statistics directly in the Project Editorworkspace. Previously, this functionality was available only after a flow analysis, but isnow also available after a discrete event simulation. To use this new feature, choose theResults

➧

Visualize Link Statistics menu option.

7 Some IS-IS Support Temporarily Removed

Release 8.0.C PL7 introduced support for processing IS-IS protocol configuration as partof the MVI module’s router configuration import. Flow Analysis also supported IS-ISrouting. Because of significant changes in the routing protocol engine, this support hastemporarily been removed, but it will be restored in an upcoming patch or release. Mean-while, release 8.1 does support running NetDoctor-based rules and validation reports onnetwork topologies that use IS-IS.

8 ERP Network Assessment Module (ENAM) Unsupported

Beginning with this release, ENAM has been dropped as a product. This has been donebecause its capabilities have been superseded by standard product and model features.


Release Notes

9

9 KP Changes

Some changes to Kernel Procedures have been made.

9.1 op_prg_list KPs

KPs in the

op_prg_list

family are not thread-safe, except for

op_prg_list_create()

.This was reported incorrectly in earlier versions of the documentation. Because there is nobuilt-in mutex, users are responsible for managing serialization of these KPs when need-ed.

9.2 op_pk KPs

Packet size is now handled as a double (it was formerly treated as integer). As a result, thefollowing arguments and return values are now doubles:

•

op_pk_id()

— return value

•

op_pk_total_size_get()

— return value

•

op_pk_total_size_set()

— total_size argument

•

op_pk_bulk_size_get()

— return value

•

op_pk_bulk_size_set() — bulk_size argument

Also, op_pk_fd_get() no longer generates a recoverable error if the field index is out-of-range for the packet. This has been removed for efficiency purposes.

9.3 op_stat_obj_reg()

The obj_id argument of this KP is given as “int” in the documentation. It should be “Ob-jid”.

10 Model Library Enhancements

Details about model features can be found in the model descriptions. For the latest docu-mentation, follow the Model Usage Guides link in the Support Center (http://www.op-net.com/support).

10.1 ATM Enhancements

The ATM model now includes the following features for discrete event simulation.

• Hard PVx connections—These can be specified using the GUI or through a GDFfile. PVx connections can be made up of both hard and soft PVxs, as long as theend-to-end connection is either a permanent virtual path or a permanent virtualconnection.



10

OPNET Modeler Release Notes Release 8.1

• Preferred routing—You can specify preferred routes for an SPVx that are looselypinned or explicitly defined at each hop.

• VPI 0/1 support for data connections.

• Friendly names for switch ports—This feature allows you to specify names forports, which provides easy-to-use reports, statistics, and attribute references.

• Improved route reports—Enhanced route reports allow you to collect the valuesof the input and output ports, VPIs, and VCIs.

• IP traffic characteristics—New attributes allow you to map IP traffic flows to dif-ferent ATM QoS classes.

• Automatic SVC setup for IP background traffic—Conversation pairs between IPcontainer nodes (ATM workstations or routers) set up an SVC automatically ifthere is no hard or soft PVC between them.

• Visualize PVC routes—After running a simulation, you can view the routes takenby ATM PVCs set up in the network.

New example scenarios in the ATM example project demonstrate these features.

10.2 PNNI Enhancements

The PNNI model now supports the following features for discrete event simulation.

• Explicit discrete event simulation for flat and hierarchical topologies. You can nowrun a simulation using one of two modes of PNNI routing: Fast mode or Explicitmode.

• Topology database export—In Explicit mode for PNNI, the model can be config-ured to export the topology database to a log message at various times during thesimulation.

• Load balancing over equal-cost paths.

• Crankback for Fast mode and Explicit mode.

• Node and link aggregation for Fast mode and Explicit mode.

• Static Peer Group Leader election for Fast mode PNNI Routing.

• Dynamic Peer Group Leader election for Explicit mode PNNI Routing.

• Configurable Complex Node parameters.

• A “Hello Stop Time” efficiency mode that allows you to stop Hello message ex-change after the network has stabilized, resulting in shorter simulation run times.

• Statistics on routing table updates are available. These include statistics on routingtable size and on the time between updates.

New scenarios in the PNNI standard project demonstrate these features.

10.3 Application Model Enhancements

The application models now support the following features.

Release 8.1 OPNET Modeler Release Notes

11

• Background traffic modeling for Voice and Video applications. By allowing you tomodel some or all of the traffic generated by voice and video applications as back-ground traffic instead of explicit traffic, this feature can significantly reduce simu-lation run times. A new API provides an open interface for dynamically creatingbackground traffic flows from application layers running over IP.

• DiffServ Code Point (DSCP) tagging for all application traffic

• ACE Model Wizard—This feature allows you to easily configure applicationswhen importing ACE trace files into a new or existing network model. For addi-tional information about this feature, refer to the ACE User Guide.

• Additional server model statistics. Many of the server model statistics can now becollected on a per-job basis and not only on a per-server basis.

• Direct delivery protocol (DDP) for TPAL to TPAL communication in custom ap-plication traffic. This feature shortens simulation execution in custom applicationsand is most useful when you are not interested in studying network delays. DDPeliminates packet flow through the entire protocol stack by delivering packetsfrom the TPAL module on the sending node directly to the TPAL module on thereceiving node. To use this feature, use Direct Delivery as the transport protocolon the sending nodes, receiving nodes, and in the custom application definition.

10.4 TCP

The TCP model now supports the following features for discrete event simulation.

• ECN— ECN is supported at TCP and IP. IP sets ECN bits using RED recommen-dations. (RFC-3168)

• New-Reno—This TCP “flavor” is available as one of the pre-configured settingsfor the TCP Parameters attribute. (RFC-2582)

• Statistic annotations—Annotations now make the per-connection statistics easierto identify when viewing results.

10.5 IP

The IP model now supports the following features for discrete event simulation.

• Simplified configuration procedures—Several new menu operations make it easi-er to configure parameters on multiple nodes at once. These parameters includerouting protocols for loopback interfaces, load balancing option, route table ex-port, and conversation pair traffic.

• Routing protocol visualization—You can view the routing protocols configured inthe network in the project editor workspace. This eliminates the need to drill downinto several compound attributes just to see which protocols are configured on aninterface. To use this feature, select the Protocols ➧ IP ➧ Visualize Routing Domainsmenu operation.

• Route maps—Route maps can be configured with multiple terms and are to con-figure route redistribution for EIGRP and BGP. BGP also uses route maps to con-figure routing policies.

• Access Control Lists (ACLs)—ACLs are used in route filtering for EIGRP and BGP,and as match settings for route maps.

12


• Ability to set different administrative weights for internal EIGRP routes and exter-nal EIGRP routes.

• Default queue specification

• Low Latency Queue (LLQ)

• Route reporting for background traffic. This feature also displays incomplete traf-fic flows, providing reasons for unroutability.

• Additional routing table statistics, including statistics for size, additions, and dele-tions

• Additional queuing schemes for IP quality of service: MWRR, MDRR, and DWRR

• Two items on the Protocols ➧ IP menu have been renamed:

- “Configure Dynamic Routing Protocols” is now “Configure Routing Pro-tocols”

- “Display Routes…” is now “Display Routes for Configured Flows…”

10.6 Hybrid Simulation

The hybrid simulation model has been enhanced to support the following features.

• DiffServ Code Points (DSCP) for characterizing background traffic

• Configurable ToS/DSCP, packet size and inter-arrival time distributions, and trac-er packet frequency for each traffic conversation pair

• Traffic shaping—This feature allows you to scale conversation pair traffic in thenetwork to conform to the capacity of link data rates in the network.

• Easier creation of traffic conversation flows. A one-step process allows you to cre-ate a full-mesh of traffic conversation pairs for a set of nodes in the network.

10.7 OSPF

The OSPF model suite now supports the following features for discrete event simulation.

• Point-to-Multipoint interface type

• Option of Periodic or LSA-driven methods to determine when routing table calcu-lations are performed

• OSPF area information is now displayed in tool tips; this replaces the legend sub-net used previously. Also, you can now remove the area visualization by choosingProtocols ➧ OSPF ➧ Clear Area Visualization.

10.8 BGP

The Protocols ➧ BGP menu now includes a “Configure IBGP Peers” item. This operationconfigures the selected nodes as internal BGP neighbors, using the IP addresses of therouters’ loopback interfaces. If not already set, IP addresses are first auto-assigned.


13

10.9 EIGRP

The EIGRP model suite now supports the following features for discrete event simulation.

• Configurable Split Horizon on a per-interface basis

• Passive interfaces

• Route filters

• Balanced and Minimum Traffic Share modes for equal and unequal cost load bal-ancing

• Configurable metric parameters (K1 through K5)

• Per-interface configuration for bandwidth, delay, load, and reliability

• New statistic reports the size of the routing table

• Ability to print information about packet contents in debugging

See the EIGRP Model Description for additional information.

10.10 DOCSIS

The DOCSIS model suite now supports the following features for discrete event simula-tion.

• Multiple upstream and downstream channels

• Payload Header Suppression (PHS)

See the DOCSIS Model Description for additional information.

10.11 Wireless LAN (WLAN)

The WLAN model suite now supports the following features for discrete event simula-tion.

• A new signal power threshold attribute controls which packets are accepted by thereceiver. Packets with received signal power below the threshold do not make thereceiver busy and the receiver treats such packets as noise packets. This new at-tribute allows you to model clear channel assessment approach in your WLANnetwork model.

• Enhanced physical layer modeling, including implementation of PLCP preambleand PLCP header overheads

• Packets traveling more than 300m in the air between two WLAN nodes of the sameBSS, a standard-imposed limit, are no longer dropped by the model. Instead, net-works that do not comply with the standard’s limit may experience some MAC al-gorithm performance degradation. This feature enables spatial reuse which mayresult with better overall performance for some network configurations

10.12 MPLS

The MPLS model suite now supports Fast-Reroute in discrete event simulation.

14


11 Model Behavior Changes in 8.1

Some of the enhancements described above will cause your model to behave differentlythan they did in the 8.0.C release. You are likely to notice these changes if you use defaultsettings in certain models—as we model new features, we sometimes change the defaultmodel behavior to better reflect common configurations or standard behavior. If you wish,you can configure your models to use the behavior of the 8.0.C models by directly control-ling appropriate attributes and overriding defaults.

In addition, like all large software packages, our model libraries contain errors, and anumber of these errors have been fixed in Release 8.1. Depending on which protocols yournetwork models use, these corrections may also result in behavioral changes for your sim-ulations. However, we believe that these changes represent more accurate simulation ofthe protocols and provide you with better results.

The following sections describe model behavior changes in the 8.1 model release.

11.1 For Models Using BGP

Network Reachability

When inserting a route into BGP using the Network Reachability Information attribute,BGP sets the route’s MED value to the IGP metric. Previously, the IGP metric did not affectMED values. This meant that two routes to the same network destination were equallypreferred routes when advertised to EBGP neighbors. You can reproduce the 8.0.C behav-ior by using route maps to configure the MED value to “0” when these routes are adver-tised to EBGP neighbors.

Routing Policies

The model now includes an implicit “Deny” statement in routing policies. This means thata route that matches none of the route maps is rejected. Previously, the model acceptedthese routes—the only routes rejected were those that matched a route map correspond-ing to a “Deny” action. You can reproduce the 8.0.C behavior by adding a route map thataccepts all routes to the end of the Routing Policies tables. Such a route map would haveits Match Info and Set Info attributes set to “None” and its Action attribute set to “Permit.”

11.2 For Models Using EIGRP

Load Balancing

The default behavior for load balancing over equal cost routes is destination-based, whichresults in fewer out-of-order packets and reduced delay. Previously, the default behaviorused packet-based load balancing, which allowed packets from the same application go-ing to the same destination to use different routes. You can reproduce the 8.0.C behaviorby setting the IP Routing Parameters ➧ Load Balancing attribute to Packet-Based. A newProtocols menu operation provides a quick way of doing this for multiple routers. To usethis feature, select the Protocols ➧ IP ➧ Configure Load Balancing menu option.


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11.3 For Models Using IP Multicasting

The default model behavior allows a rendez-vous point (RP) to initiate a switch to a short-est path tree (SPT) in response to a register message from the sender’s first hop router. Thismay produce different simulation results than those obtained in prior releases. To restorethe behavior of the 8.0.C model, set the PIM-SM Interval attribute and the PIM-SM SourceThreshold attribute to “Infinity.”

The model now automatically prunes RP trees when a router in the network is directly at-tached to a source and one or more receivers. This prevents unnecessary traffic betweenthe router and the RP. Because earlier versions of the model did not prune RP trees, sim-ulation results may differ in the 8.1 model.

11.4 For Models Using TCP

Selective Acknowledgement (SACK)

Enhancements to the SACK feature enable the model to generate less TCP overhead be-tween nodes that send traffic (TCP requests) to each other. Model behavior is unchangedbetween nodes where one node sends only requests and the other node sends only re-sponses.

Statistic Panels

The annotations used when reporting TCP statistics have changed. If you created panelsin an earlier release and saved them as template panels, they will be unable to load datacollected from the 8.1 TCP model. To view your results, simply re-create the analysis pan-els after running a simulation with the 8.1 models.

11.5 For Models Using ATM

The 8.1 ATM models do not use a cell tax attribute, which increased the amount of band-width reserved for a call in earlier releases. Because less bandwidth is reserved per call,the routes chosen in 8.1 may differ from those in 8.0.C. You can restore the previous be-havior by modifying the reservation as indicated in the following table.

Reservation Modifications Required to Restore 8.0.C Behavior

QoS 8.0.C Value 8.1 Value Required For 8.0.C Results

CBR PCR PCR * (53/48)

rt-VBR SCR SCR * (53/48)

nrt-VBR SCR SCR * (53/48)

ABR MCR MCR * (53/48)

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11.6 For Models Using PNNI

Configuring the network to use PNNI

As in earlier releases, the ATM Dynamic Routing Protocol simulation attribute is still usedto configure your ATM network model to use PNNI routing. However, the “PNNI” valuefor this attribute has been replaced by two new options in 8.1, “Explicit PNNI” and “Fast-Mode PNNI.” Before running a simulation using PNNI in 8.1, you must first select one ofthe new PNNI options in the Configure Simulation dialog box.

Peer Group Leader Election

To support dynamic election of peer group leaders, the Peer Group Leader attribute hasbeen replaced by the Peer Group Leader Priority attribute. If a network configured in anearlier model release contains hierarchies, you must reconfigure the peer group leaders touse the new attribute. Otherwise, the hierarchy is lost and the network becomes a flat-levelnetwork. To restore the hierarchy, set the Peer Group Leader Priority attribute to a posi-tive integer for each peer group leader. This corresponds to a value of “Yes” for the PeerGroup Leader attribute of previous releases.

Unlike previous releases, which supported only static election of peer group leaders, the8.1 model dynamically elects peer group leaders during the simulation. When a peergroup leader is first elected during the simulation, the node with the highest peer groupleader priority is elected leader. If that node fails, a new leader is elected for the group.

Complex Node Parameters

The default complex node parameters, such as administrative weight, CTD, and CDV,have changed. This may cause the 8.1 model to choose different routes for the demands.To restore the 8.0.C behavior, restore the complex node parameters to the previous de-faults, as indicated in the following table.

Default Values for Complex Node Parameters

Attribute Default Value in 8.0.C models Default Value in 8.1 models

Administrative Weight 2520 10080

Cell Transfer Delay (CTD) (sec)

CBR 1.36E-007 0.002

rt-VBR 2.61E-007 0.002

nrt-VBR 5.11E-007 0.002

ABR and UBR 0.0 0.002

Cell Delay Variation (CDV) (sec)

CBR 1.25E-007 0.001


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Statistic Panels

The annotations used when reporting PNNI statistics have changed. If you created panelsin an earlier release and saved them as template panels, they will be unable to load datacollected from the 8.1 PNNI model. To view your results, simply re-create the analysispanels after running a simulation with the new models.

11.7 For Custom Applications Using the ACE Model

Task Contention Mode

When you configure custom applications to use ACE, you can now take advantage of con-tention modeling on tier nodes. Previous models only allowed you to simulate the delayincurred by the application on a tier node in the "Contention Already Modeled" mode,such that response time was obtained from the ACE trace and did not reflect contentionwith other concurrently executing tasks. If you wish to obtain the earlier behavior, simplyensure that the "Task Contention Mode" attribute is set to "Contention Already Modeled".

Inter-Repetition and Start Time Offsets

The default Inter-Repetition time for applications created using the ACE wizard uses anexponential distribution instead of the constant distribution used in earlier releases. By de-fault, the wizard configures the value of Start Time Offset to equal the value of Inter-Rep-etition Time. These changes reduce the likelihood of all applications starting at the sametime and producing a sudden spike in network traffic. You can restore the default behav-ior of the model by changing the attribute values to the 8.0.C defaults, as indicated below.

rt-VBR 2.5E-007 0.001

nrt-VBR 0.0 0.001

ABR and UBR 0.0 0.001

Cell Loss Ration (CLR)

CBR 1E-012 1E-008

rt-VBR 1E-009 1E-008

nrt-VBR 1E-006 1E-008

ABR and UBR 0.0 1E-008

Maximum Cell Rate (Mbps) 149.67 2500

Available Cell Rate (Mbps) 149.67 2500

Default Values for Complex Node Parameters (Cont.)

Attribute Default Value in 8.0.C models Default Value in 8.1 models

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11.8 For Models Using Hybrid Simulation

When conversation pair traffic exceeds link capacity, the traffic is scaled down to complywith the link’s data rate. If this traffic is from a single flow, the flow rate is scaled to thelink data rate. If the aggregate traffic of multiple flows exceeds a link’s capacity (as op-posed to a single flow in the previous case), each flow is scaled down proportionately ac-cording to its demand. For example, suppose there are two flows, A and B, traversing a T3link with a data rate of 45Mbps. If Flow A is 40Mbps and Flow B is 60Mbps, then Flow Arepresents 40% of the aggregate traffic traversing the link and Flow B represents 60%. Af-ter the traffic has been scaled to the link’s date rate, the flow rates will be 40% of 45Mbpsfor Flow A and 60% of 45Mbps for Flow B.

You can restore the behavior of earlier releases by disabling traffic shaping in the Back-ground Traffic (BGUtil) configuration object.

8.0 Default Settings from the ACE Wizard

Attribute 8.0.C Default Value

Inter-Repetition Time constant

Start Time Offset uniform (5, 10)

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