Edit: it seems I either misunderstood or was misled by this article, which seems to imply that a 10 Gbps switch is required to make good use of a dozen nodes with gigabit ports. With the clarification that 10/100/1000 generally refers to link speed, the rest of the question doesn't make much sense anymore!
I am new to networking, and I am having trouble finding resources on how traffic is routed through an ethernet network. As I understand it, most gigabit-compatible devices can handle the full gigabit bandwidth through a single interface, and even cat6 cables can handle 10 Gbps--so neither interfaces nor links are likely to be the rate-limiting components of a network. But it is unclear to me exactly how the limits that do exist apply. I have a few diagrams to illustrate.
Say I have 1 gigabit of data on node 1, and I want to send 1/3 gigabit of it to each of the other nodes.
Network A is simple and seemingly pretty standard. Assuming that the switch can only handle 1 Gbps of net traffic (I've read articles that seem to imply this, but I've never seen it stated explicitly), it is clear that the transfer cannot be faster than 1 second, with node 1 sending at 1 Gbps and nodes 2-4 receiving at 1/3 Gbps each.
In Network B (two switches), is it the case that 1) traffic is distributed through both switches so the transfer is completed twice as fast as in Network A, or 2) the network protocol as a whole can only handle 1 Gbps of data and the transfer rate is unchanged?
In Network C (fully-connected), where each node has many interfaces, does the communication protocol enforce a bandwidth limit, or is the interface speed the only bottleneck?
Note: I am aware that this is an oversimplified case--that in some cases, links and interfaces can be bottlenecks, and that I've ignored lots of issues with overhead, theoretical vs. real bandwidths etc. But I don't believe those are necessary for the question I'm asking.