VoIP Definition Stands for "Voice Over Internet Protocol," and is often pronounced "voip." VoIP is basically a telephone connection over the Internet. The data is sent digitally, using the Internet Protocol (IP) instead of analog telephone lines. This allows people to talk to one another long-distance and around the world without having to pay long distance or international phone charges. In order to use VoIP, you need a computer, an Internet connection, and VoIP software. You also need either ...

SIP Definition Stands for "Session Initiation Protocol." SIP is a protocol defined by the Internet Engineering Task Force (IETF). It is used for establishing sessions between two or more telecommunications devices over the Internet. SIP has many applications, such as initiating video conferences, file transfers, instant messaging sessions, and multiplayer games. However, it is most well known for establishing voice and video calls over the Internet. VoIP companies, such as Vonage, Phone Power, ...

TTL Definition Stands for "Time To Live." Pretty intense for a computer term, huh? It refers an aspect of the Internet Protocol. TTL is used when a "ping," or a request for a response, is sent to another computer, such as a server. The TTL represents the number of hops, or servers in different locations, the request can travel to before returning a failed attempt message.

Payload Definition When data is sent over the Internet, each unit transmitted includes both header information and the actual data being sent. The header identifies the source and destination of the packet, while the actual data is referred to as the payload. Because header information, or overhead data, is only used in the transmission process, it is stripped from the packet when it reaches its destination. Therefore, the payload is the only data received by the destination system.

IP Address Definition An IP address, or simply an "IP," is a unique address that identifies a device on the Internet or a local network. It allows a system to be recognized by other systems connected via the Internet protocol. There are two primary types of IP address formats used today — IPv4 and IPv6. IPv4 An IPv4 address consist of four sets of numbers from 0 to 255, separated by three dots. For example, the IP address of TechTerms.com is 67.43.14.98. This number is used to identify the TechT...

UDP Definition Stands for "User Datagram Protocol." It is part of the TCP/IP suite of protocols used for data transferring. UDP is a known as a "stateless" protocol, meaning it doesn't acknowledge that the packets being sent have been received. For this reason, the UDP protocol is typically used for streaming media. While you might see skips in video or hear some fuzz in audio clips, UDP transmission prevents the playback from stopping completely.

VCI Definition Stands for "Virtual Channel Identifier." The VCI, used in conjunction with the VPI (virtual path indicator), indicates where an ATM cell is to travel over a network. ATM, or asynchronous transfer mode, is a method that many ISPs (Internet Service Providers) use to transfer data to client computers. Because ATM sends packets over fixed channels, the data is easier to track than information sent over the standard TCP/IP protocol. The VCI within each ATM cell defines the fixed chann...