Which term describes a protocol used for connecting routers of different systems?

The term that describes a protocol used for connecting routers of different systems is the Exterior Gateway Protocol (EGP). EGPs are specifically designed to facilitate communication between different autonomous systems, which are collections of IP networks and routers under the control of a single organization.

An example of an Exterior Gateway Protocol is Border Gateway Protocol (BGP), which is crucial for the functioning of the internet as it enables the exchange of routing information between diverse networks. This is essential in maintaining the overall connectivity of the internet and ensuring that data can be routed appropriately from one network to another that may not share a common path.

In contrast, the other options refer to protocols that operate within a single system or are not primarily designed for inter-system communication. Routing Information Protocol (RIP) and Interior Gateway Protocols (IGPs) like Open Shortest Path First (OSPF) are mainly used within a single autonomous system. Dynamic Routing Protocols, while they can include both interior and exterior protocols, do not specifically denote the purpose of connecting different autonomous systems like EGPs do. Thus, the focus and application of EGPs make this the most appropriate choice for the definition provided in the question.