Lucent Technologies Release 8.2 manual Osi, Paccon

Open System Interconnect (OSI) Model Glossary

O

Open System Interconnect (OSI) Model

P

An International Standards Organization (ISO) interoperability specification. OSI defines standard services that compliant communications networks and equipment must provide, rather than specific implementations. It divides network operations into 7 steps, called layers, and arranges them hierarchically, in a protocol stack. The rules (protocols) in each layer of the stack specify a service that other parts of a communications system can always get, as long as they make their requests in a standard way. This approach leaves designers free to implement the internal details of the service in whatever way seems best to them. The OSI layers are 1 Physical (transmission medium), 2 Datalink (link-level signaling and error control), 3 Network (computer-to-computer signaling, routing, etc.), 4 Transport (delivery, end-to-end error control, and flow control), 5 Session (dialog management), 6 Presentation (data-format compatibility), and 7 Application (file-transfer services, virtual terminals, etc.).

OSI

See Open System Interconnect (OSI) Model.

out-of-service state (OOS)

The condition or state of an MMCX server that is operating but not ready to accept or place calls.

PACCON

Packet controller.

packet

A group of bits (including a message element, which is the data, and a control information element (IE), which is the header) used in packet switching and transmitted as a discrete unit. In each packet, the message element and control IE are arranged in a specified format.

packet bus

A wide-bandwidth bus that transmits packets.

packet switching

Adata-transmission technique whereby user information is segmented and routed in discrete data envelopes called packets, each with its own appended control information, for routing, sequencing, and error checking. The packets can travel to their destinations by varying routes. For data transmissions, a packet switched network can make more efficient use of available bandwidth than a circuit-switched network, because it does not dedicate a channel for the duration of a call. Instead, packets are queued and sent on a standby basis, as channel capacity becomes available. The Internet is a good example of a packet-switching network.

		Administration for Network Connectivity
482	CID: 77730	555-233-504 — Issue 1 — April 2000