IS-IS is an acronym for which of the following?

IS-IS stands for Intermediate System to Intermediate System, which is a link-state routing protocol used in both IPv4 and IPv6 networks. Originally developed for the ISO/IEC 10589 standard, this protocol is designed to facilitate routing within an autonomous system by exchanging routing information between routers, referred to as intermediate systems.

The relevance of this name lies in the operation of the protocol itself; it enables the exchange of routing information among network devices rather than directly between end devices like hosts. This nomenclature also emphasizes the role that each router plays in the routing process, acting as a point of control and decision-making in the overall network infrastructure.

By understanding that IS-IS refers to 'Intermediate Systems,' it highlights the protocol’s function within a larger network architecture, distinguishing it from other protocols which might operate at different layers or focus on varying aspects of network operation.