Which protocol should you select if the network diameter is more than 17 hops?

For a network where the diameter is more than 17 hops, you would generally prefer a protocol designed for larger, more complex networks. In traditional IP networks, protocols like OSPF (Open Shortest Path First) or IS-IS (Intermediate System to Intermediate System) are better suited for larger networks due to their scalability and efficiency over large distances and complex topologies. OSPF and IS-IS are both link-state routing protocols that can handle large networks with many routers efficiently by understanding the entire network topology.

However, if we’re discussing large-scale networks specifically in the context of spanning-tree calculations for Ethernet networks, one might consider MSTP (Multiple Spanning Tree Protocol) or even TRILL (Transparent Interconnection of Lots of Links) as these are designed to create efficient large-scale layer 2 networks, though the original question seems to pertain more to routing protocols where OSPF or IS-IS would be applicable.

For WAN (Wide Area Network) connections that might span great distances beyond the scope of simple protocols like RIP (Routing Information Protocol), which is limited by a maximum hop count of 15, MPLS (Multiprotocol Label Switching) is another technology often used to efficiently manage and route traffic across large and complex networks, although it’s not a routing protocol per se but rather a technique for managing traffic flows across a network.

Choosing the right protocol depends on several factors including the specific network requirements, existing infrastructure, and performance needs.