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This article follows on from part one, published last week.

Performance
IT Guru led the pack. The product is very flexible and scaleable, providing many customisation features. The user interface offers several options and templates that let users drag and drop several kinds of network topologies. This creates a product that is sophisticated, powerful and complex. At times, we found ourselves overwhelmed by its rich features and complexity.

NetRule required little time and effort to configure and build a network model. The product provided a palette of Cisco-specific and generic network devices. Model creation is straightforward. Simply drag and drop devices from the NetRule library to create the network, adding the appropriate links and routing protocol information. Next, define the source and destination, and the required resources such as priority, message bytes, delay and traffic type. We felt this was as straightforward as a model configuration can be.

Unfortunately, NetRule does not interface with management packages such as OpenView and CiscoWorks. NetRule can read a CiscoWorks text file, but not as directly as IT Guru. The text file has to be in the predefined format that NetRule expects. This made the replication of our large-scale production environment a labour-intensive process. As a result, we couldn't easily import our 120-device network topology into the product. Instead, we manually created a 12-router subset of our production network. It took us about 30 minutes to model the 12-router, full-mesh network topology.

Once the model was completed, we could create reports based on configuration changes to the devices and links. The NetRule reporting feature was very good, and provided a graphical display of network utilisation, delay, traffic flow and the like.

NetRule's performance was acceptable. It took longer than we expected for the application to launch, but once it started, NetRule seemed to operate relatively quickly in displaying the result whenever we implemented changes to the model.

Shunra's approach to network modelling is more empirical - it literally records the network conditions directly and plays them back, while enabling applications to run against the recorded model. Because of this approach, some typical modelling parameters don't apply to the product, such as importing network configurations from CiscoWorks or OpenView.

Configuration involved right-clicking on a link or device in Visio and making changes through a drop-down menu. We could then observe the changes on the network by watching how the applications running through StormAppliance behaved. A built-in Sniffer-like protocol-decode function was a plus. Shunra's reporting function produces a nice real-time chart that displays throughput per second in and out, queues, delay and packet counts.

Shunra is a hardware-based, network-modelling product. That gives it somewhat of an edge in terms of performance over an entirely software-based modelling application. In most instances its speed was as good as or better than the other products in terms of implementing network-modelling changes. However, the appliance did have an annoying tendency: Whenever we changed certain model parameters, we had to warm-boot the hardware. For example, switching StormAppliance between Layer 2 and Layer 3 (switching and routing) required a reboot, as did turning on and off multicast. (It's often preferable to change between switching and routing in the same network to observe the performance characteristics of a network model using Layer 2 switching or Layer 3 switching/routing.) Adding insult to injury, the reboot process was slow - it took more than 2 minutes.

Installation issues
Opnet's IT Guru 10.5 is a complete product. We received four CDs that contained the Report Server module, the IT Guru application, documentation and the Opnet Model Library. The package also includes the Application Characterisation Environment (ACE), Simulation Runtime, Flow Analysis, Net Doctor and the ACE Decode Module. There are numerous modules (some come with the base product, some are included depending on the specific configuration ordered, and some are optional at extra cost.) The number of modules available for IT Guru reflects the flexibility and complexity of the product. This isn't a package that you just install and walk away from. It has a plethora of options and capabilities that need to be mastered before a user can take full advantage of it.

IT Guru installed without problem, although it took nearly 10 minutes to install the model library, which checks in at a whopping 830M bytes of hard drive space. We were surprised that the installation process required two complete reboots to make the program ready for use.

NetRule was far more compact, taking up a mere 13M bytes of space, but it doesn't not contain the tools and modules that IT Guru has. NetRule took just more than a minute to install, with no reboots required.

The Shunra/Storm package included the StormAppliance hardware, StormCatcher (enables the capture and replay of network activity) and StormConsole. StormAppliance is responsible for emulating link conditions such as bandwidth, packet loss, delay and out-of-order packets. StormConsole (a Microsoft Visio macro) creates the network model and is used as the interface to StormAppliance. Installation of StormCatcher and StormConsole was brief.

We had some problems attaching our laptop to the network ports on StormAppliance. The Dell Latitude notebooks equipped with 100M bit/sec Ethernet PC cards could not connect to StormAppliance, while another Dell laptop with an integrated Gigabit Ethernet port connected without a problem. After searching the documentation, we found that PCs must be connected to the appliance using the supplied crossover cables. We were using regular Ethernet cables. The Gigabit Ethernet-enabled laptop supported auto-sensing of cable configuration. Shunra should have pointed out the need to use the crossover cables in the installation section instead of burying this in an appendix.

Documentation
The IT Guru documentation is on a CD-ROM and online. If a customer requires printed documentation, there is an extra fee. We were surprised that a product this complex and expensive did not include professionally printed documentation.

NetRule's printed documentation appeared to come from a colour laser printer. We would have preferred a higher-quality presentation, although the necessary information was included.

Shunra provided a professionally printed user manual. The configuration procedure is nicely laid out. We were disappointed in the amount of effort it took to dig out some specific information from the documentation (for example, our crossover cable issue).

Deployment considerations
IT Guru is extremely powerful and feature-rich. Users are expected to possess both a thorough knowledge of networking and the product itself, giving it the highest learning curve of any of the products we tested.

Even after a full day's training by Opnet, we sometimes scratched our heads when we tried to use several of the product's advanced features. However, once we began to understand the product, it became clear that IT Guru was almost unlimited in its capabilities.

Network engineers looking for a sophisticated package that can model almost any enterprise network would find IT Guru to their liking.

NetRule doesn't have all the bells and whistles of IT Guru, but what it lacks in muscle power it makes up for in user friendliness.

After attending a one-day training session, we could create network models without problem. This easy-to-learn package does a decent job modelling smaller-sized networks, making it ideal for modelling building or departmental LANs.

While Shunra doesn't compare to IT Guru and NetRule for in-depth enterprise network modelling, it does show how applications and networks can be affected by bandwidth throttling, link limitations, packet delay, jitter and the like. Using Visio as the device interface was a brilliant idea.

It is the rare network engineer or designer who isn't at least somewhat familiar with Visio. This makes it a terrific front end to Shunra/Storm, and significantly reduces the learning curve. It has excellent capabilities to simulate frame relay, T-1s and Gigabit links. This, coupled with drop-downs that allow on-the-fly changes to links, make Shunra/Storm a natural for modelling WAN connections.

Jeffrey Fritz is the director of Enterprise Networking Services for the University of California, San Francisco. He is responsible for network technology development and campus-wide voice and data network operations, and is the author of Remote LAN Access: a guide for networkers and the rest of us, and Sensible ISDN Data Applications, which is in its third printing.