T
TACACS+
Terminal Access Controller Access Control System. Often run on UNIX systems, the
TACAS+ protocol provides access control for routers, network access servers, and other
networked computing devices via one or more centralized servers. TACACS+ provides separate
authentication, authorization, and accounting services. User passwords are administered in a
central database rather than in individual routers, providing easily scalable network security
solutions.
tagged VLAN
You identify packets as belonging to the same tagged VLAN by putting a value into the
12-bit (4 octet) VLAN ID field that is part of the IEEE 802.1Q field of the header. Using this
12-bit field, you can configure up to 4096 individual VLAN addresses (usually some are
reserved for system VLANs such as management and default VLANs); these tagged VLANs can exist
across multiple devices. The tagged VLAN can be associated with both tagged and untagged
ports.
TCN
Topology change
notification. The TCN is a timer used in
RSTP that signals a
change in the topology of the network.
TCP / IP
Transmission Control Protocol. Together with Internet Protocol (IP), TCP is one of the
core protocols underlying the Internet. The two protocols are usually referred to as a group,
by the term TCP/IP. TCP provides a reliable connection, which means that each end of the
session is guaranteed to receive all of the data transmitted by the other end of the
connection, in the same order that it was originally transmitted without receiving
duplicates.
TFTP
Trivial File Transfer
Protocol. TFTP is an Internet utility used to transfer files, which does not provide security
or directory listing. It relies on
UDP.
TKIP
Temporal Key Integrity
Protocol (TKIP) is an enhancement to the WEP encryption technique that uses a set of
algorithms that rotates the session keys. The protocol's enhanced encryption includes a
per-packet key mixing function, a message integrity check (MIC), an extended initialization
vector (IV) with sequencing rules, and a re-keying mechanism. The encryption keys are changed
(re-keyed) automatically and authenticated between devices after the re-key interval (either a
specified period of time, or after a specified number of packets has been
transmitted).
TLS
Transport Layer
Security. See
SSL
ToS / DSCP
ToS (Type of Service) /
DSCP (Diffserv Codepoint). The ToS/DSCP box contained in the IP header of a frame is used by
applications to indicate the priority and
Quality of Service
for each frame. The level of service is determined by a set of service parameters which
provide a three way trade-off between low-delay, high-reliability, and high-throughput. The
use of service parameters may increase the cost of service.
transit node
In
EAPS, the transit node is a switch, or node, that is not
designated a master in the EAPS domain ring.
truststore
A repository containing
trusted certificates, used to validate an incoming certificate. A truststore usually contains
CA certificates, which represent certificate authorities that are trusted to sign
certificates, and can also contain copies of server or client certificates that are to be
trusted when seen.
TSN
Transition Security Network. A subset of Robust Security Network (RSN), which provides an
enhanced security solution for legacy hardware. The Wi-Fi Alliance has adopted a solution
called Wireless Protected Access (WPA), based on TSN. RSN and TSN both specify IEEE 802.1x
authentication with Extensible Authentication Protocol (EAP).
Time-Sensitive Networking. Standards under development by the Time-Sensitive Networking
task group of the IEEE 802.1 working group. There are various characteristics of TSN,
including packet preemption, prioritized packet queuing, congestion control, bandwidth
reservation, and transmit latency determination used to guarantee that data packets always
arrive within a certain predetermined window of time.
tunnelling
Tunnelling (or
encapsulation) is a technology that enables one network to send its data via another network's
connections. Tunnelling works by encapsulating packets of a network protocol within packets
carried by the second network. The receiving device then decapsulates the packets and forwards
them in their original format.