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 simple 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.