X.25 Network : X.25 standard is a packet-switching wide area network developed by ITU-T in 1976. The standard specifies an interface between a host system and a packet switching network. That is, X.25 standard is an interface between data terminal equipment(DTE) and data circuit terminatiny equipment (DCE) for terminal operation in the packet mode on public data networks.
Layers :
(i) Physical Layer
(ii) Data Link layer
(iii) Network layer
1) Physical layer :
The layer od OSI that co-ordinates the function required to transmit a
bit over a physical medium called physical layer. It deals with the
mechanical and electrical specification of devices.
Characteristics :
i) Physical characteristics of interfaces & media
ii) It represents the data
iii) Data rate
iv) Synchronization of bits
v) Physical topology
vi) Transmission mode
vii) Line configuration
2) Data Link layer : The layer of OSI that transforms the physical layer to a reliable link is called data link layer.
Characteristics :
i) It deals with framing
ii) Physical addressing
iii) Flow control
iv) Error control
v) Access control
vi) Traffic regulation mechanism
3) Network Layer : The layer that responsible source to destination to delivery of packet
multiple network is called network layer.
Characteristics :
i) Logical addressing
ii) Routing
iii) Connecting different network.