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Glossary

session

1) Session layer of OSI model is responsible for keeping track of

user data and keeping it separate on the network. 2) Reliable sessions can be
set up between hosts.

Session layer

Layer 5 of the OSI reference model, responsible for creating,

managing, and terminating sessions between applications and overseeing
data exchange between presentation layer entities. See also: Application
layer, Data Link layer, Network layer, Physical layer, Presentation layer,
and Transport layer.

setup mode

Mode that a router will enter if no configuration is found in

nonvolatile RAM when the router boots. Allows the administrator to con-
figure a router step-by-step. Not as robust or flexible as the command-line
interface.

A super frame (also called a D4 frame) consists of 12 frames with

192 bits each, and the 193rd bit providing other functions including error
checking. SF is frequently used on T-1 circuits. A newer version of the tech-
nology is Extended Super Frame (ESF), which uses 24 frames. See also: ESF.

shared tree

A method of multicast data forwarding. Shared trees use an

architecture in which multiple sources share a common rendezvous point.

shortest-path-first

A type of routing protocol. The only true SPF protocol

is Open Shortest Path First (OSPF).

signaling packet

An informational packet created by an ATM-connected

mechanism that wants to establish connection with another such mecha-
nism. The packet contains the QoS parameters needed for connection and
the ATM NSAP address of the endpoint. The endpoint responds with a mes-
sage of acceptance if it is able to support the desired QoS, and the connection
is established. See also: QoS.

silicon switching

A type of high-speed switching used in Cisco 7000

series routers, based on the use of a separate processor (the Silicon Switch
Processor, or SSP). See also: SSE.

simplex

The mode at which data or a digital signal is transmitted. Simplex

is a way of transmitting in only one direction. Half duplex transmits in two
directions but only one direction at a time. Full duplex transmits both direc-
tions simultaneously.

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