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Terminologies Simplified

OAM(&P) Operations, Administration, Management (and Provisioning) refer to ATM-specific diagnostic flows used to test/troubleshoot switching systems.

OC The optical specification over SONET. An OC level is the optical equivalent of an STS signal. Transmission rates are based on 51.84 Mbps (OC-1). A c following an OC level identifies concatenation of payload (for example, OC-3c).

Open Datalink Interface Protocol-independent Novell specification providing standardized access to networks; allows multiple network interface card device drivers and protocols to share a single network interface card without conflict.

Open Systems Interconnection (OSI) Program created by the ISO and CCITT (now ITU-T) for developing international standards for data networking.

Open Shortest Path First (OSPF) An interior gateway protocol that routes messages according to the shortest and least expensive path. OSPF was developed to replace RIP.

Open Systems Interconnection (OSI) reference model A seven-layer model for data communication that is the standard network architecture developed by the International Organization for Standardization (ISO). The layers are as follows: physical, data-link, network, transport, session, presentation, and application.

Packet Burst The technology used in NetWare networks that allows clients and servers to transmit multiple packets of information without requiring a response to each packet, thus reducing local and wide area network traffic.

Packet-switching network A network that transmits

messages by dividing them into individual packets, routing them randomly over the best available connection, and then reassembling them to form the complete message at the destination. Most modern WAN protocols, including TCP/IP, X.25, and frame relay, are based on packet-switching technologies.

Peer-to-peer network A network in which each node (computer) has equivalent client and server capabilities. In a peer-to-peer network, communication and data sharing occurs directly between nodes, rather than through an intermediary node.

Permanent virtual circuit (PVC) A continuously available communications path that connects two fixed end points. A PVC is similar to a leased line.

Physical layer The first of seven layers of the OSI model, the physical layer puts data onto and removes data from the network media.

Physical topology The physical layout of a network's guided transmission media (usually network cabling). The most common physical topologies are the bus, the star, and the star-wired ring.

Pluggable Authentication Module (PAM) A login framework used by system entry components to authenticate users to a UNIX system.

Point of Presence (POP) The location of an access point to the Internet. A POP necessarily has a unique IP address. An Internet Service Provider or online service has a point of presence on the Internet. The number of POPs that an ISP or OSP has is sometimes used as a measure of its size or growth rate.

Point-to-Point Protocol (PPP) The communications protocol a computer uses to make TCP/IP connections with a regular telephone line and a modem.

Point-to-Point Remote Node Service (PPPRNS) A service that provides PPP support for remote DOS and Windows clients that are using Internetwork Packet Exchange (IPX) software or Internet Protocol (IP).

Point-to-Point Tunneling Protocol (PPTP) A technology used to create virtual private networks. PPTP ensures that messages transmitted from one VPN node to another are secure.