Page 637

598

Glossary

store-and-forward packet switching

A technique in which the switch

first copies each packet into its buffer and performs a cyclical redundancy
check (CRC). If the packet is error-free, the switch then looks up the desti-
nation address in its filter table, determines the appropriate exit port, and
sends the packet.

STP

1) Shielded Twisted Pair: A two-pair wiring scheme, used in many net-

work implementations, that has a layer of shielded insulation to reduce EMI.
2) Spanning Tree Protocol.

stub area

An OSPF area carrying a default route, intra-area routes, and

interarea routes, but no external routes. Configuration of virtual links
cannot be achieved across a stub area, and stub areas are not allowed to con-
tain an ASBR. See also: non-stub area, ASBR, and OSPF.

stub network

A network having only one connection to a router.

STUN

Serial Tunnel: A technology used to connect an HDLC link to an

SDLC link over a serial link.

subarea

A portion of an SNA network made up of a subarea node and its

attached links and peripheral nodes.

subarea node

An SNA communications host or controller that handles

entire network addresses.

subchannel

A frequency-based subdivision that creates a separate broad-

band communications channel.

subinterface

One of many virtual interfaces available on a single physical

interface.

subnet

See: subnetwork.

subnet address

The portion of an IP address that is specifically identified

by the subnet mask as the subnetwork. See also: IP address, subnetwork, and
subnet mask.

subnet mask

Also simply known as mask, a 32-bit address mask used in

IP to identify the bits of an IP address that are used for the subnet address.
Using a mask, the router does not need to examine all 32 bits, only those
selected by the mask. See also: address mask and IP address.

www.sybex.com