In Riverbed SteelCentral Portal Application Models, an "Internal Element" is the most granular component representing a specific, monitored application process or instance running on a host. These elements are the fundamental building blocks of an application's architecture within the model. For example, a specific Apache web server process, a Java Virtual Machine (JVM), or a database instance on a server would each be defined as an Internal Element. The model then maps the communication paths and dependencies between these specific instances to provide a detailed view of application performance and behavior.

A. Traffic between hosts is represented as a "Link" or "Flow" in the application model, not an element itself.

B. Servers are the hosts on which elements run; an Internal Element is the specific application instance on the server, not the server itself.

D. Logical sets of hosts are defined as "Tiers" (e.g., Web Tier, Database Tier), which are containers for multiple Internal Elements.

1. Riverbed SteelCentral Portal User's Guide, Version 4.8, Chapter 6: "Application models," Section: "Application model components," Page 127. The guide states: "Internal elements are the application instances that are part of the application model. For example, you can add a specific HTTP server as an internal element." This directly supports that an Internal Element is an application instance.

2. Riverbed SteelCentral Portal User's Guide, Version 4.8, Chapter 6: "Application models," Section: "Application model components," Page 127. The guide defines a Tier as: "Tiers are logical groupings of servers in an application model." This confirms that a logical set of hosts (Option D) is a Tier, not an Internal Element.