T

TCP port

Used to define a common communications channel for Transmission Control Protocol/Internet Protocol (TCP/IP) applications. For example, the Simple Mail Transfer Protocol (SMTP) protocol uses port 25 to communicate, which allows mail servers that otherwise would not know of each other to successfully exchange data.

Time to Live (TTL)

The amount of time a packet destined for a host will exist before it is deleted from the network. TTLs are used to prevent networks from becoming congested with packages that cannot reach their destinations.

top-level folder

In a Microsoft Exchange Server 2003 public folder hierarchy, a top-level folder is the highest-level folder in the tree. By default, users can create top-level folders, but a common security practice is to remove this permission so that only administrators can create top-level folders and users can create subfolders.

transaction logs

The primary storage area for new transactions made to Extensible Storage Engine (ESE) databases. Data is written to the logs sequentially as new transactions occur. Changes in the logs are later committed to the actual databases. Transaction logs in Microsoft Exchange Server 2003 are always 5 megabytes (MB) in size, and when a log reaches 5 MB, a new log is created.

Trojan horse

A computer program that appears to be useful but that actually does damage. See also virus, worm.

TTL

See Time to Live (TTL).