I readed some articles but I still don't undestand the difference, is point-to-point transmites unicast messages, so point-to-multipoint uses broadcasts ? is point-to-point consist of one dedicated physical cable, so point-to-multipoint consist of shared routes ?.... and wich topology is used in Internet and Ethernet ?
Most of time, the terms point to point or point to multipoint refer to logical topology, not physical topology. One can configure P2P or P2MP on various type of media, and the ability to use broadcasts depends on the type of media you have.
Ethernet is usually considered a broadcast media, where every station can hear every other station, but modern switched Ethernet makes it act like P2P, because the switch connects a sender and receiver with a single logical connection. And when you have a single Ethernet cable connecting two devices, that can also be considered a P2P connection although the media is still broadcast.
In the context of OSPF configuration, again it's a logical topology, so you get to decide how it's configured.
These terms refer to Wide Area Networking at the link layer, i.e., data link layer. Sites/branch offices can be connected via dedicated end-to-end links (point to point) or they can be connected via a single link to a shared infrastructure, sometimes called a cloud. The benefit of the mesh topology vs point to point is that spokes/branch offices can:
- communicate directly with other spokes without having to route (hairpin) through a central site.
- utilize a single link to the mesh cloud (provider) vs having to provision several (n+1) links.
Frame relay and MPLS are often implemented as mesh topologies, called Non Broadcast Multi Access (NBMA). Layer 2 Ethernet WAN's are very popular now. This would be a Broadcast Multi Access (BMA). In any case, these terms refer to the passing of frames.
The Internet (as in Internet Protocol, IP) is a higher layer / level communications model whereby packets are routed based on available underlying links.