the network layer of the osi reference model provides for internetwork connectivity.
the network layer of the osi reference model provides for internetwork connectivity.
which layer s of the osi reference model provide s for internetwork connectivity?
network layer
although x.25 predates the osi reference model (osirm), the physical layer of the osi model corresponds to the x.25 "physical layer", the data link layer to the x.25 "data link layer", and the network layer to the x.25 "packet layer". the x.25 "data link layer", lapb, provides a reliable data path across a data link (or multiple parallel data links, multilink) which may not be reliable itself. the x.25 "packet layer" provides the virtual call mechanisms, running over x.25 lapb. the "packet layer" includes mechanisms to maintain virtual calls and to signal data errors in the event that the "data link layer" cannot recover from data transmission errors. all but the earliest versions of x.25 include facilities which provide for osi network layer addressing (nsap addressing, see below).
x.25
in 1983, these two documents were merged to form a standard called "the basic reference model for open systems interconnection". the standard is usually referred to as "open systems interconnection reference model", "osi reference model", or simply "osi model". it was published in 1984 by both the iso, as standard iso 7498, and the renamed ccitt (now called the telecommunications standardization sector of the international telecommunication union or itu-t) as standard x.200.
osi model