T1 Connection
A phone or data connection that can support the transfer of up to 1.544Mbits of data per second. T1 connections are popular among businesses and ISPs. Most T1s are connected to T3, which can handle up to 43Mbits per second and are actual Internet backbone connections.

T3
Dedicated telecommunications line providing 44 Mbps of bandwidth. T3 lines are often used by ISPs to connect to the Internet backbone.

Tape back-up
A popular and inexpensive way to back up Web sites. Contents of a site are periodically stored that looks similar to a cassette. Some cassettes can store several gigabytes.

Tcl - Tool command language
Simple scripting language and library often used for GUI, string-manipulation, testing, and integration of multiple components.

TCP - Transmission Control Protocol
Transmission Control Protocol or TCP is an important network protocol. TCP allows two hosts to connect and exchange data, and ensures that "data packets" are delivered exactly as sent.

TCP/IP - Transmission Control Protocol/Internet Protocol
This protocol suite is the de facto standard for the today's Internet. TCP is a higher level protocol that runs on top of the IP protocol.

Technical Support
The support provided by an official or an external professional with the appropriate technical skills. In web hosting the quality and efficiency of tech support offered varies greatly. Recently this has become the measuring stick used to define a quality web hosting company.

Telnet
Character-based protocol for connecting with remote systems. Still popular among hosts, but it is being replaced by much more secure SSH access.

Terabyte
TB equals 1,000 Gigabytes or 1 million Megabytes or 1 billion kilobytes.

Terminal Server
This is a special purpose computer that has places to plug in many modems on one side, and a connection to a LAN or host machine on the other side. Thus, the terminal server does the work of answering the calls and passes the connections on to the appropriate node. Most terminal servers can provide PPP or SLIP services if connected to the Internet.

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Third Level Domain
The next highest level of the hierarchy underneath the second level domains. In a domain name, that portion of the domain name that appears two segments to the left of the top-level domain. For example, this is used quite often in city and governmental websites like the web site for Orange County California is www.oc.ca.gov (oc is the 3rd level).

TIA - Telecommunications Industry Association
Another telecommunications standards organization.

Title Tags
An HTML tag with text describing a specific Web page (but not visually displayed on the page). The title tag should contain strategic keywords for the page and be constructed following specific guidelines. The title tag is important because it usually becomes the text link to the page found in search engine listings, and because search engines pay special attention to the title text when indexing pages.

TLD - Top Level Domain
In the Domain Name System (DNS), the highest level of the hierarchy after the root. In a domain name, that portion of the domain name that appears furthest to the right. For example, the .net in whois.net The most common domains or TLDs are .COM, .NET, and .ORG

Traceroute
A computer program that lists network hosts visited by a packed on the way to its destination. Very useful for network debugging.

Traffic
Data packets being transmitted over a network.

Tree
A data structure consisting of nodes which may contain other nodes via its branches. Unlike a tree in nature, the root node is usually represented at the top of the structure and does not have a parent node. All other nodes have a single parent. Nodes having no child nodes are called leaf nodes. An XML document represents a tree structure.

Trouble Ticket
A computerized system of reporting a specific problem or requesting help from a web hosting providers tech support staff. The trouble ticket system is usually web based and is beneficial to the hosting company in tracking requests and ensuring timely resolutions for clients.

TTL - Time To Live
Time To Live, the number of seconds remaining on a cached record before it is purged. For authoritative records the TTL is fixed at a specific length. If a record is cached, the server providing the record will provide the time remaining on the TTL rather then the original length it was given.

Twisted Pair
A pair of wires twisted one around the other. Very common in the networking applications.

TXT Record
Text Record: Strictly informational, not functional. Used to provide up to 255 characters of free form text, hopefully about the zone. Multiple TXT records are permitted but their order is not necessarily retained, a bad forum for presenting War and Peace.