PHYSICAL SERVICE DEFINITION OF OPEN SYSTEMS INTERCONNECTION
FOR CCITT APPLICATIONS1
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1 Recommendation X.211 and ISO/IEC 10022, Information processing systems -
Open systems interconnection - Physical layer service definition, were
developed in close collaboration and are technically aligned.
half-duplex (two-way alternate), or simplex (one way); either point-to-point or
multi-endpoint; and either synchronous or asyhchronous as appropriate (see Section
8).
plexing, they will be conveyed implicitly via the Physical Layer protocol.
Note - This encompasses various forms of LAN topology (ring/bus).
by the Network Layer Protocol Control Information being conveyed either via the same
PhC (in-band signalling), or via a separate PhC (out-of-band signalling), see Figure
4/X.211. Physical Layer relay systems do not complete the end-to-end PhC until
Network Layer control actions are completed among the Network Layer entities en
route. Deactivation may be accomplished through either Network layer protocol or
management actions.
of PhPDU transmission. They are required for half-duplex and are optional for duplex
and simplex. The Ph-ACTIVATE request primitive requests activation of the PhC. Each
direction of transmission is activated independently for half-duplex operation, and
both directions of transmission are activated for duplex operation. For half-duplex
and simplex operation, the Ph-ACTIVATE request primitive activates the outgoing
direction of transmission, and the Ph-ACTIVATE indication primitive indicates
activation of the incoming direction of transmission. During half-duplex operation, a
Ph-ACTIVATE request cannot be issued by the PhS user after receipt of a Ph-ACTIVATE
indication and before the receipt of a Ph-DEACTIVATE indication primitive.
PhS Activation - mode shift: half-duplex receive to half-duplex
send or to duplex (without inactive state)
tion of PhPDU transmission. They are required for half-duplex and are optional for
duplex and simplex. The Ph-DEACTIVATE request primitive requests deactivation of the
PhC. Each direction of transmission is deactivated independently for half-duplex
operation, and both directions of transmission are deactivated for duplex operation.
For half-duplex and simplex operation, the Ph-DEACTIVATE request primitive
deactivates the outgoing direction of transmission, and the Ph-DEACTIVATE indication
primitive indicates deactivation of the incoming direction of transmission. During
half-duplex operation, a Ph-ACTIVATE request primitive can be issued by a PhS
user after receipt of the Ph-DEACTIVATE indication primitive.
PhS User Deactivation - Mode shift: half-duplex send or duplex
to half-duplex receive (without inactive state)
