Architecture

An arrangement of protocol layers in which each layer is given specific tasks to accomplish.

Cache

A file on a domain name resolver that stores domain names and IP addresses that have been resolved. Then, when someone else needs to resolve that same domain name, there is no need to go through the entire resolution process. Instead, the resolver can supply the IP address from the local file.

 A means for coordinating activity between two or more communicating computers. Two machines must agree on the protocol to use, and they must follow that protocol as they send messages back and forth. Because there is so much to do, communications tasks are broken up into levels, or layers, of protocols.

Domain name

The registered, human-friendly valid name in the domain name system (DNS). The process of changing a name into its IP address is called resolving the domain name.

Domain name resolution   

The process of converting a domain name into a public IP address.

Domain name resolvers   

Computers that facilitate domain name resolution by storing the correspondence of domain names and IP addresses.

Domain name system (DNS)

A system that converts user-friendly names into their IP addresses. Any registered, valid name is called a domain name.

A service provided by some communications devices that allocates and deallocates a pool of IP addresses. A device that hosts the DHCP service is called a DHCP server. On request, a DHCP server loans a temporary IP address to a network device such as a computer or printer. When the device disconnects, the IP address becomes available, and the DHCP server will reuse it when needed.

File Transfer Protocol (FTP)   

A Layer-5 protocol used to copy files from one computer to another. In interorganizational transaction processing, FTP enables users to exchange large files easily.

The container used at Layers 1 and 2 of the TCP/IP–OSI model. A program implementing a Layer-2 protocol packages data into frames.

Hypertext Transfer Protocol (HTTP)   

A Layer-5 protocol used to process Web pages.

An international organization that sets worldwide standards. ISO developed a seven-layer protocol architecture called Open Systems Interconnection (OSI). Portions of that protocol architecture are incorporated into the TCP/IP–OSI hybrid protocol architecture.

Internet Corporation for Assigned Names and Numbers (ICANN)   

The organization responsible for managing the assignment of public IP addresses and domain names for use on the Internet. Each public IP address is unique across all computers on the Internet.

Internet Engineering Task Force (IETF)   

An organization that specifies standards for use on the Internet. Developed the four-layer scheme called the TCP/IP (Transmission Control Program/Internet Protocol) architecture. TCP/IP is part of the TCP/IP–OSI protocol architecture that is used on the Internet and most internets today.

Internet Protocol (IP)

IP address 

A series of dotted decimals in a format like 192.168.2.28 that identifies a unique device on a network or internet. With the IPv4 standard, IP addresses have 32 bits. With the IPv6 standard, IP addresses have 128 bits. Today, IPv4 is more common, but it will likely be supplanted by IPv6 in the future. With IPv4, the decimal between the dots can never exceed 255.

IPTV (Internet Protocol television)   

A technology that uses the TCP/IP–OSI protocol to transmit television and other video signals via a broadband connection and set-top box.

Layered protocols

Different ways of arranging the layers of communication protocols for transmission of data across networks. TCP/IP is one such layered protocol.

Logical address

Also called an IP address, a series of dotted decimals in a format like 192.168.2.28 that identifies a unique device on a network or internet. With the IPv4 standard, IP addresses have 32 bits. IP addresses are called logical addresses because they can be reassigned from one device to another.

MAC address   

Network Address Translation (NAT)   

The process of changing public IP addresses into private network IP addresses, and the reverse.

 Program   [that implements a protocol]

A specific computer product that implements a protocol; for example, Netscape Navigator and Microsoft Internet Explorer are two such programs.

 A standardized means for coordinating an activity between two or more entities.

Public IP address

An IP address used on the Internet. Such IP addresses are assigned to major institutions in blocks by the Internet Corporation for Assigned Names and Numbers (ICANN). Each IP address is unique across all computers on the Internet.

Reference Model for Open Systems Interconnection (OSI)   

A protocol architecture created by ISO that has seven layers. Portions of the OSI model are incorporated into the TCP/IP–OSI hybrid architecture that is used on the Internet and most internets.

Root servers   

Special computers that are distributed around the world that maintain a list of IP addresses of servers that resolve each type of top-level domain.

Routing table   

A table of data used by a router to determine where to send a packet that it receives.

 The container that a TCP uses to carry messages. The TCP program places identifying data at the front and end of each segment that are akin to the to and from addresses that you would put on a letter for the postal mail.

Set-top box

Simple Mail Transfer Protocol (SMTP)   

A Layer-5 architecture used to send email. Normally used in conjunction with other Layer-5 protocols (POP3, IMAP) for receiving email.

  A company, owned by Yahoo!, that provides voice-over-IP (VoIP) phone service.

Switch table   

A table of data used by a switch to determine where to send frames that it receives.

TCP/IP–OSI (protocol) architecture   

A protocol architecture having five layers that evolved as a hybrid of the TCP/IP and the OSI architecture. This architecture is used on the Internet and on most internets.

Top-level domain (TLD)   

The last letters in any domain name. For example, in the domain name www.icann.org the top-level domain is .org. Similarly, in the domain name www.ibm.com, .com is the top-level domain. For non–U.S. domain names, the top-level domain is often a two-letter abbreviation for the country in which the service resides.

Transmission Control Program (TCP)

TCP operates at Layer 4 of the TCP/IP–OSI architecture. TCP is used in two ways: as the name of a Layer 4 protocol and as part of the name of the TCP/IP–OSI protocol architecture. The architecture gets its name because it usually includes the TCP protocol. TCP receives messages from Layer-5 protocols (like http) and breaks those messages up into segments that it sends to a Layer-3 protocol (like IP).

Transmission Control Program/Internet Protocol (TCP/IP) architecture   

A protocol architecture having four layers; forms the basis for the TCP/IP–OSI architecture blend used by the Internet.

Uniform resource locator (URL)   

A document’s address on the Web. URLs begin on the right with a top-level domain, and, moving left, include a domain name and then are followed by optional data that locates a document within that domain.

Voice over IP (VoIP)