Physical, datalink, network layer are OSI circuit layers is covered in the X.25 standards.
X.25 is an ITU-T standard protocol suite for packet switched wide area network (WAN) communication. An X.25 WAN consists of packet switching exchange (PSE) nodes as the networking hardware, and leased lines, plain old telephone service connections, or ISDN connections as physical links.
Physical layer:-
The physical layer is the first layer of the Open System Interconnection Model (OSI Model). The physical layer deals with bit-level transmission between different devices and supports electrical or mechanical interfaces connecting to the physical medium for synchronized communication.
Data link layer:-
The data link layer is used for the encoding, decoding and logical organization of data bits. Data packets are framed and addressed by this layer, which has two sublayers. The data link layer's first sublayer is the media access control (MAC) layer. It is used for source and destination addresses.
Network layer:-
The network layer is the third level of the Open Systems Interconnection Model (OSI Model) and the layer that provides data routing paths for network communication. Data is transferred in the form of packets via logical network paths in an ordered format controlled by the network layer.