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Glossary

TE1

A device with a four-wire, twisted-pair digital

interface is referred to as terminal equipment type 1.
Most modern ISDN devices are of this type.

TE2

Devices known as terminal equipment type 2 do

not understand ISDN signaling techniques, and a ter-
minal adapter must be used to convert the signaling.

telco

A common abbreviation for the telephone

company.

Telnet

The standard terminal emulation protocol

within the TCP/IP protocol stack. Method of remote
terminal connection, enabling users to log in on
remote networks and use those resources as if they
were locally connected. Telnet is defined in RFC 854.

terminal adapter

A hardware interface between a

computer without a native ISDN interface and an
ISDN line. In effect, a device to connect a standard
async interface to a non-native ISDN device, emulat-
ing a modem.

terminal emulation

The use of software, installed

on a PC or LAN server, that allows the PC to function
as if it were a "dumb" terminal directly attached to a
particular type of mainframe.

TFTP

Conceptually a stripped-down version of FTP,

it's the protocol of choice if you know exactly what
you want and where it's to be found. TFTP doesn't
provide the abundance of functions that FTP does. In
particular, it has no directory-browsing abilities; it can
do nothing but send and receive files.

Thicknet

Also called 10Base5. Bus network that

uses a thick cable and runs Ethernet up to 500 meters.

Thinnet

Also called 10Base2. Bus network that uses

a thin coax cable and runs Ethernet media access up to
185 meters.

token

A frame containing only control information.

Possessing this control information gives a network
device permission to transmit data onto the network.
See also: token passing.

token bus

LAN architecture that is the basis for the

IEEE 802.4 LAN specification and employs token
passing access over a bus topology. See also: IEEE.

token passing

A method used by network devices

to access the physical medium in a systematic way

based on possession of a small frame called a token.
See also: token.

Token Ring

IBM's token-passing LAN technology.

It runs at 4Mbps or 16Mbps over a ring topology.
Defined formally by IEEE 802.5. See also: ring topol-
ogy and token passing.

toll network

WAN network that uses the Public

Switched Telephone Network (PSTN) to send packets.

trace

IP command used to trace the path a packet

takes through an internetwork.

transparent bridging

The bridging scheme used in

Ethernet and IEEE 802.3 networks, it passes frames
along one hop at a time, using bridging information
stored in tables that associate end-node MAC
addresses within bridge ports. This type of bridging is
considered transparent because the source node does
not know it has been bridged, because the destination
frames are sent directly to the end node. Contrast
with: SRB.

Transport layer

Layer 4 of the OSI reference model,

used for reliable communication between end nodes
over the network. The Transport layer provides mech-
anisms used for establishing, maintaining, and termi-
nating virtual circuits, transport fault detection and
recovery, and controlling the flow of information. See
also: Application layer, Data-Link layer, Network
layer, Physical layer, Presentation layer, and Session
layer.

TRIP

Token Ring Interface Processor: A high-speed

interface processor used on Cisco 7000 series routers.
The TRIP provides two or four ports for interconnec-
tion with IEEE 802.5 and IBM media with ports set to
speeds of either 4Mbps or 16Mbps set independently
of each other.

troubleshooting engine

Part of the Online Techni-

cal Support menu. This tool can be used to help isolate
and diagnose many networking problems, based on
user input and the Cisco database.

troubleshooting model

A series of steps or proce-

dures that can be executed or followed to methodi-
cally and effectively troubleshoot and resolve network
failures or outages.

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