Connection-oriented transport layer protocol that provides reliable full-duplex data transmission. TCP is part of the TCP/IP protocol stack.

An application that lets you log on remotely to a Unix computer, and act as if you're working from a terminal connected directly to the computer. You need a valid username and password to connect to a computer in this way.

In the Domain Name System (DNS), the next highest level of the hierarchy below the second level domains. In a domain name, that part of the domain name that appears two segments to the left of the top-level (or first level) domain. For example, the "support" in support.example.com. Third level domains are not the part of an e-mail address that appears in front of the "at" (@ )symbol. For instance, the support in support@example.com is not a third level domain.

A message and all its replies in an online discussion.

In the Domain Name System (DNS), the highest level of the hierarchy after the root. In a domain name, the top level domain is that part of the domain name that is furthest to the right. For example, the "com" in example.com.

A TCP/IP utility that allows a user to determine if two computers are communicating successfully with each other.