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Frequently Asked Questions

The primary difference is that for each pair of ports, Linktropy simulates a single link and Netropy simulates multiple virtual links. This is easiest to explain for the Linktropy 5510 and Netropy N61 which each have a single pair of ports.

All traffic that enters the Linktropy 5510 on one port has the same configured conditions (bandwidth, latency, loss, etc.) applied before exiting the opposite port. If a latency of 50 ms is configured, all packets get delayed by 50 ms. This keeps configuration incredibly simply and intuitive – just fill in the bandwidth, delay, and loss of the link on the browser-based form, apply changes, and your link is configured.

However, some users need to apply different conditions to different flows. For example, you might want to simulate a headquarters or datacenter connected to multiple remote sites. Or you may want to isolate traffic from a single server to test a particular application. Or perhaps you want to run multiple tests in parallel for side-by-side comparison. Netropy offers this flexibility by creating multiple virtual links, or paths, between each pair of ports. Each link is configured with its own bandwidth, latency, and loss parameters. Packets entering each port are directed to the appropriate link by IP source and destination address range (IPv4 or IPv6), VLAN, TCP/UPD port numbers, or other packet identifier.

In addition to the single port-pair Linktropy 5510 and Netropy N61, both Linktropy and Netropy are available in models with multiple port pairs. It is easiest to think of each pair of ports as a separate emulation device. For example, the Linktropy 8510, which includes 4 port pairs, is essentially equivalent to having four Linktropy 5510 units.

Beyond the distinction of single link vs. multi-link, Netropy includes additional features for advanced testing requirements not found on Linktropy. For example, Netropy can simulate data corruption, network outages, IP ToS prioritization, RED queuing in addition to drop-tail, and periodic and burst packet loss conditions.

Whether Linktropy or Netropy is more suitable depends on your specific requirements for numbers of links, total emulated bandwidth, and special features. If you require any assistance, please call us and we’ll be happy to recommend the most appropriate and cost-effective model for your testing needs.

Until Apposite developed the Linktropy and Netropy products, there were only two alternatives for network simulation: high-end telecoms products and freeware emulators. High-end telecoms simulators are designed to test WAN connection equipment rather than application performance and the products are focused primarily on the needs of telecoms professionals. Their prices put them out of range of most IT departments while their complexity make them difficult to use without extensive training.

Freeware systems are extremely limited in precision and performance, rendering them useless as a reliable test tool.

See our side by side comparison to freeware here

The founders of Apposite Technologies recognized the need for a better solution. Linktropy and Netropy WAN Emulators are the culmination of a mission to offer a professional-quality WAN emulator designed for the needs of enterprise networking. The products had to have the precision and performance of the high end products, at a price suitable for IT departments and application developers with limited budgets and many priorities, and quick and intuitive to install and operate without training.

Both models have the same feature set and differ only in capacity and number of ports. With 4 pairs of independently configured ports, the 8510 is essentially equivalent to having four 5510s.

The Linktropy Mini2 and Mini-G are portable, low cost emulators, designed to simulate basic WAN conditions of bandwidth, latency, and loss for product demonstrations and application development.

The Mini2 and Mini-G were designed for portability and cost and offer only a subset of the features found on the Linktropy lab models. The Mini2 and Mini-G are appropriate for product demonstration and basic application testing, and offer precision and performance far superior to any software or freeware WAN emulator. The Linktropy 5510 and 8510 along with the Netropy emulators, offer additional features useful for lab testing and product benchmarking, and provide an order of magnitude higher level of precision. See the Linktropy Mini2 or Linktropy Mini-G product page for more details.

Yes, the NetropyVE is a software version of Apposite’s network emulation appliances.  With NetropyVE you can recreate realistic network conditions in virtualized or cloud environments.  NetropyVE works on leading hypervisors VMware vSphere and KVM, and coming soon on cloud platforms AWS, Google Cloud, and Microsoft Azure.

Why use the software version of Netropy? Many software development teams run their tests in a cloud or private datacenter where they do not have the ability to install an appliance. With NetropyVE, it is now possible to install WAN emulation between virtual resources.

Linktropy and Netropy network simulators are designed to be extremely easy to use, with an intuitive, browser-based GUI. Training is absolutely unnecessary. However, we’re happy to provide a one hour WebEx demo to walk through the configuration and operation of the product for your situation, review all of the features, and answer any questions you may have.

Apposite has always bundled hardware, software and maintenance releases into one bundle. We’re offering ongoing maintenance releases and support with the 1 year and 3 year product licenses.

Some older models have been replaced with updated hardware offering higher capacity and identical functionality at the same price. The replacement models are:

Linktropy 4500Linktropy 5510
Linktropy 5500Linktropy 5510
Linktropy 7500Linktropy 5510
Linktropy 7500 PROLinktropy 8510
Linktropy 8500Linktropy 8510
Linktropy 10GNetropy 10G2
Linktropy MiniLinktropy Mini
Netropy N60Netropy N61
Netropy N80Netropy N91
Netropy N90Netropy N91
Netropy 10GNetropy 10G2

All Linktropy and Netropy products are classified under ECCN 5A992 for the hardware and 5D992 for shipment or download of the firmware alone. The Schedule B code is 8517.62.90.

Linktropy 8510 can simulate one link through each of four port-pairs. Netropy N61 can simulate up to 15 links through a single port-pair. The price is the same. But there are some differences:

Netropy N61 can emulate 15 separate links compared to 4 for the Linktropy 8510. If you need more than four links, Netropy is the obvious choice.

With only one set of GigE ports, the Netropy N61 is limited to 1 Gbps in each direction aggregated over all the WAN links. The Linktropy 8510 can simulate 1 Gbps on each link. If you need to simulate multiple 1 Gbps links, Linktropy is the better choice.

If neither of the above criteria determine the choice, then it becomes a matter of feature set and preference. Linktropy is designed for absolute ease-of-use while Netropy is more feature-rich to meet the needs of advanced users.

Yes. Both Linktropy and Netropy were designed with satellite and other long latency conditions in mind and can handle delays of up to 10 seconds in each direction.

Yes. Both Linktropy and Netropy can emulate jitter conditions on a network link.

However, it is important to define what kind of jitter is required.

There are two main cases:

standard deviation
peak-to-peak (also known as max delay variation)
Standard deviation jitter can be represented as a normal distribution, where the standard deviation is the jitter.

Peak-to-peak jitter can be represented as a uniform distribution, where the difference of the max and min is the jitter.

Linktropy and Netropy can fulfill these test requirements by creating a normal or uniform delay distribution.

Users who have registered their unit are notified by e-mail whenever firmware updates become available. Firmware images are posted on the support section of the Apposite website for downloading. (A current maintenance contract or product license is required to log onto the site.) Use the Product Registration page to register a unit.

No. Linktropy and Netropy simulate the conditions of the wide area network. They are not traffic generators. However, both product lines can simulate background traffic to model the effect of competing traffic and bandwidth availability on application performance.

Yes. Product User’s Guides, Quick Start Guides, and Hardware Guides are all available in PDF form from the Product Documentation page.

Apposite certified Visio stencils for all the Linktropy and Netropy models are available free of charge from NetZoom. They can be downloaded by clicking on the following link:

Linktropy and Netropy products are designed for anyone who needs an accurate, easy-to-use, cost-effective way to test the performance of applications over the WAN, including:

  • Corporate IT managers and network administrators
  • Application and equipment vendors
  • Military network developers
  • Sales and SE professionals
  • Networking equipment resellers and system integrators
  • Q/A teams
  • Test labs

Linktropy and Netropy simulators are used by network managers across a wide range of industries with a need to test application performance, including retail, media, banking, healthcare, pharmaceuticals, manufacturing, and oil & gas. In addition, Linktropy and Netropy products are used by many of the leading network equipment and application developers, including Cisco, Juniper, Microsoft, Riverbed, IBM, HP, NetApp, EMC, BlueCoat, and Citrix. A few of the more than 2,500 Apposite customers are listed on our Customers page.

‘Linktropy’ and ‘Netropy’ are short for Link/Net + Entropy since the product is designed to add entropy to a clean link or network.

“Apposite” is pronounced similar to “opposite” but starting with an “a” sound. It means “highly pertinent or appropriate” (Merriam-Webster), hence our slogan: Apposite products, apposite prices, Apposite Technologies.