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Glossary

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
topology and token passing.

toll network

WAN network that uses the public switched telephone net-

work (PSTN) to send packets.

traceroute

also 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 com-

munication between end nodes over the network. The transport layer provides
mechanisms used for establishing, maintaining, and terminating 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.

trap

Used to send SNMP messages to SNMP managers.

TRIP

Token Ring Interface Processor: A high-speed interface processor

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

trunk link

Link used between switches and from some servers to the

switches. Trunk links carry information about many VLANs. Access links
are used to connect host devices to a switch and carry only VLAN informa-
tion that the device is a member of.

TTL

time to live: A field in an IP header, indicating the length of time a

packet is valid.

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