T-U

task

A thread of execution. Real-time environments frequently use this term to depict code which has its own execution context including program counter, stack and local variables.

TCP

Transmission Control Protocol. Most widely used transport protocol for reliability.

telnet

A protocol used for terminal access to hosts in the Internet. Telnet runs over TCP.

thread

A schedulable entity that can share data with other such entities.

time division multiplexing (TDM)

A method of sharing a medium using time slots in which data from multiple senders is sent over multiple time slots.

timer

A function required to keep track of the temporal activities required by the communications system. Timers can be one shot (they only fire once) or continuous. One-shot timers are required for actions that are performed only once after a certain period of time. Continuous timers start off with a timeout value and count down from there. On reaching zero, they generate an event and reset the timeout value to count down again.

timer block

A data structure which stores the countdown value for a timer and the parameters related to it. These can include the ID of the task/module which started the timer along with the routine to be called upon timeout (with its parameters). Timer blocks are linked to each other to form one or more timer lists.

timer management

The mechanism to handle multiple timers for one or more protocols or the entire system. This mechanism involves starting and stopping timers as well as signaling tasks and modules with the appropriate parameters upon a timeout.

timer management task (TMT)

A task which manages the timers for all the tasks in the system. This is the only task which maintains the lists of timer blocks.

TL1

Transaction Language 1. A standard originally specified by Bellcore (now Telcordia) for the management of network elements. It is a set of ASCII-based instructions or messages used by a network manager (also called an Operations Support System or OSS in telecom parlance) to manage a network element or device.

TLV

Type Length Value. A scheme of encoding of messages where the first field represents the type of parameter, the second represents the length of the parameter, and the third represents the actual parameter value. Each of the fields could span multiple bytes.

TOE

TCP Offload Engine. A hardware device or board which is used to improve the performance of a system by terminating and processing TCP connections. This frees up the CPU to handle other tasks.

traffic engineering

An aspect of network engineering concerned with the performance optimization of traffic on the network. The most common is the optimization with respect to over-utilization and under-utilization of paths and links in the network.

trap

A notification or alert sent by an SNMP agent to one or more SNMP managers using an SNMP Trap PDU. The notification can be the result of an alert sent by a protocol or system task to the SNMP Agent task.

trie

A tree structure for storing strings with a common node for each prefix. Often used as a structure for storing IP network address prefixes for faster searches. The name comes from retrieval and is pronounced “tree.”

UDP

User Datagram protocol. A connectionless transport protocol less reliable than TCP.

unicast address

The network address of a specific station.

UNIX

An operating system originally developed at Bell Labs and commercialized by AT&T. Another version was developed in the late 70s at the University of California, Berkeley. This was known as Berkeley Systems Distribution (BSD) UNIX.

user mode

The mode in UNIX where applications operate as individual processes with memory protection enforced between processes, as well as between the process and the operating system kernel.