Linux Network Administration - Glossary

Backbone

The top level in a hierarchical network. Stub networks and transit networks which connect to the same backbone are guaranteed to be interconnected.

Client

(1) a process running on a host computer which requests services; (2) a computer running a client process.

Concurrent Server

A concurrent server operates in this fashion: 1. The server receives the incoming connection. 2. The server calls fork() to split itself into two processes, a parent and a child. 3. The child process handles the connection, while the parent returns to listen on the original port. 4. When the child process is finished with the connection, it terminates. A server which operates like this is called a concurrent server. A concurrent server is always available for incoming connections. For example, a system in which the telnet server is set up as a concurrent server can handle multiple telnet connections, each of which is managed by a different child of the listening server process.

Daemon

On UNIX systems, a process which runs independently of any login session and performs system maintenance or functions as a server.

DNS

Domain Name Service - resolves domain names to IP addresses

Domain

On the Internet, "domain" is most commonly used to refer to a group of computers whose hostnames share a common suffix, the domain name. The last component of this is the top-level domain.

Ethernet

A LAN developed by Xerox in 1976. Ethernet became a widely implemented network from which the IEEE 802.3 standard for contention networks was developed. It uses a bus topology and the original Ethernet relies on CSMA/CD to regulate traffic on the main communication line.

Fiber Distributed Data Interface (FDDI)

FDDI is a 100 Mbit/s ANSI standard local area network architecture. It is based on optical fibre (though it can be copper cable, in which case it may be called CDDI).

File Transfer Protocol (FTP)

Protocol used to transfer data over a network.

Gateway

A machine which links two networks.

Hypertext Transfer Protocol (HTTP)

Hypertext Transport Protocol defines how messages are formatted and transmitted over the Web and how Web browsers should respond to those messages.

Internet control message protocol (ICMP)

A protocol used to communicate errors or other conditions at the IP layer

IP address

Server or Host address. Usually represented in dotted decimal notation, eg., 255.255.0.0.

Iterative server

An iterative server operates in this way: 1. The server receives the incoming connection. 2. The server handles the connection. 3. The server closes the connection. 4. The server returns to listening on its well-known port. A server that operates like this is called an iterative server. When an iterative server is handling a request, other connections to that port are blocked. The incoming connections must be handled one after another. For example, a system in which the telnet server is set up as an iterative server can handle only one incoming telnet connection at a time.

kernel

The kernel is the core of the UNIX operating system. The kernel remains hidden from typical users.

Local Network (LAN)

Local Area Network. A collection of computers and other hardware components linked by physical cabling that permits any device on the network to interact with any other device.

Loopback address

127.0.0.1. This address is used for diagnostics.

MTU

MTU=maximum transmission unit; the largest single packet of data thata particular medium can send.

Netmask

A 32-bit bit mask which shows how an Internet address is to be divided into network, subnet and host parts.

Network Information Database

The NID (Network Information Database) provides a means to synchronize account information across computer systems.

Network Information Service (NIS)

NIS is Sun Microsystems' Yellow Pages (yp) client-server protocol for distributing system configuration data such as user and host names between computers on a network.

NFS

Network File System (NFS) is a Unix-based file system that allows remote access to shared disk resources.

NNTP

Network News Transfer Protocol (NNTP) is a protocol that allows the browsing and downloading of messages from discussion forums on a TCP/IP network. NNTP also defines the procedures used by NNTP servers for replication messages between them.

Point-to-point protocol (PPP)

A protocol for connecting to the Internet. PPP provides error checking and compression of the IP and TCP headers.

process

A UNIX process is a running program.

Protocol stack

A layered set of protocols which work together to provide a set of network functions.

Raw socket

A raw socket allows privileged users direct access to a protocol other than those normally used for transport user data, for example, network level protocols.

Resolver library

The TCP/IP protocol library software that formats requests to be sent to the Domain Name Server for hostname to Internet address conversion.

RIP

RIP uses distance-vector algorithms to determine routes. With RIP, routers transfer information among other routers to update their internal routing tables and use that information to determine the best routes based on hop counts between routers. TCP/IP and IPX support RIP.

Router

A device used to connect networks of different types, such as those using different architectures and protocols. Routers work at the Network layer of the OSI model. This means they can switch and route packets across multiple networks. They do this by exchanging protocol-specific information between separate networks. Routers determine the best path for sending data and filter broadcast traffic to the local segment.

Serial port

A connector on a computer to which you can attach a serial line connected to peripherals which communicate using a serial (bit-stream) protocol.

Server

(1) a process running on a host computer which supplies services in response to client requests. (2) a computer which runs server processes.

Service Access Facility

The Service Access Facility is a Solaris mechanism for controlling access to server processes.

SMTP

Simple Mail Transfer Protocol (SMTP) is a protocol that allows the sending of messages over a TCP/IP-based network from one computer to another. It is generally used to send messages from one Internet mail server to another and to send messages from clients to servers. Messages are typically retrieved from servers by clients using POP3 or IMAP4.

SUID permission

The SUID permission sets a process's user ID on execution.

TCP (Transmission Control Protocol) TCP/IP Illustration

A transport layer protocol providing reliable data transmission.

TCP/IP

TCP/IP is the network protocol suite used by the Internet and most local area networks.

Telnet

A TCP/IP application that is used for remote terminal access and can be used to administer a UNIX machine.

Transport layer

Provides communication sessions between computers.

UDP

User Datagram Protocol: A connectionless datagram service in the Transport layer used by applications that typically transmit small quantities of data.

WAN

Wide Area Network. A network that extends over distances greater than one mile.

X

The X protocol is used for sharing of graphical display resources across a network. Most UNIX systems use X for their graphical user interface. The X protocol allows a process to run on one machine and open a window for graphical output on another machine. In the X protocol, an X server usually corresponds to a display, and an X client is a program that shows data on that display.The X server is typically called X, and a sample X client is xterm, which opens a terminal window. X clients usually use port numbers starting at 6000 to make connections with X servers.

X-Windows

X-Windows is a Graphical User Interface standard that is widely used in the UNIX world.

10BaseT

A variant of Ethernet which allows stations to be attached via twisted pair cable. 10BASE-T is an implementation of Ethernet which allows stations to be attached via twisted pair cable. The name 10BASE-T is derived from several aspects of the physical medium. The 10 refers to the transmission speed of 10 Mbit/s. The BASE is short for baseband. This means only one Ethernet signal is present on the send and/or receive pair. In other words there is no multiplexing as with broadband transmissions. The T comes from twisted pair, which is the type of cable that is used. The nominal segment length for a 10Base-T cable is 100 meters, not 10, as with 100BASE-T and 1000BASE-T.