USER'S GUIDE HSIM-W6

Chapter E: Glossary
238 HSIM-W6 User’s Guide
Network Layer — Layer 3 of the OSI reference model that provides the protocol routing
function.
Node — Refers to a termination point for communication links; entity that can access a network.
OSI — Open System Interconnection. An international standard developed by ITU (formally
CCITT) and ISO (International Organization for Standardization) to facilitate data networking
multi-vendor interoperability. The OSI Reference Model defines seven layers, each providing
specific network functions.
Packet — A group of data that includes a header and usually user data for transmission through a
network.
Ping (Packet Internet Groper) — An echo message, available within the TCP/IP protocol suite,
sent to a remote node and returned; used to test the accessibility of the remote node.
PPP (Point-to-Point Protocol) — A Data Link layer protocol that provides asynchronous and
synchronous connectivity between computer/network nodes. Includes standardization for security
and compression negotiation.
Q.921 — ISDN Data Link layer specification for the user-to-network interface.
Q.931 — ISDN specification for call set-up and signaling on ISDN connections.
RFC — Request for Comment. Documentation describing Internet communications
specifications (e.g., TELNET, TFTP). Often these RFCs are used to achieve multi-vendor
interoperability during implementation.
RJ11 — Standard 4-wire connectors for telephone lines.
RJ45 — Standard 8-wire connectors used for ISDN lines.
RIP (Routing Information Protocol) — Protocols used in IP and IPX for broadcasting open path
information between routers to keep routing tables current.
Routing — A Network layer function that determines the path for transmitting packets through a
network from source to destination.
RS-232 — EIA standard specifying the physical layer interface used to connect a device to
communications media.