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  • Hirofumi Takahashi thinks this is interesting:

An important observation from Chapter 1, “TCP/IP Review,” is that the data link/physical layers and the transport/network layers, as defined by the OSI model, perform very similar duties: They provide the means for conveying data from a source to a destination across some path. The difference is that the data link/physical layers provide communications across a physical path, whereas the transport/network layers provide communications across a logical or virtual path made up of a series of data links.

From

Cover of Routing TCP/IP, Volume 1, 2/e

Note

Layer1&2 vs. Layer3&4