Chapter 1 N+

host

(1) Any computer or device on a network that provides or uses a resource such as an application or data. (2) In the context of virtualization, the physical computer on which virtualization software operates and manages guests.

HTTP (Hypertext Transfer Protocol)

An Application layer protocol that formulates and interprets requests between web clients and servers.

FTP (File Transfer Protocol)

An Application layer protocol used to send and receive files via TCP/IP.

header

An area at the beginning of a payload where protocols add control information.

hub

An outdated connectivity device that belongs to the Physical layer of the OSI model and retransmits incoming data signals to its multiple ports.

fire suppression system

Any system designed to combat the outbreak of a fire. A fire suppression system might include an emergency alert system, fire extinguishers, emergency power-off switch, and/or a suppression agent such as a foaming chemical or water.

grounding

Connecting a device directly to the earth so that, in the event of a short circuit, the electricity flows into the earth rather than out of control through the device.

client-server application

Data or a service requested by one computer from another.

domain

In the context of Windows Server NOSes, a group of users, servers, and other resources that share account and security policies.

MSDS (material safety data sheet)

Instructions provided with dangerous substances that explain how to properly handle these substances and how to safely dispose of them. Also called SDS (safety data sheet).

firmware

Programs embedded into hardware devices.

decapsulation

Removing a header or trailer from a lower OSI layer.

Data Link layer address

See MAC (Media Access Control) address.

hardware address

See MAC (Media Access Control) address.

backbone

The central conduit of a network that connects network segments and significant shared devices (such as routers, switches, and servers) and is sometimes referred to as "a network of networks."

client

A computer or application that makes a request from another computer or application.

fragmentation

A Network layer service that subdivides packets into smaller packets when those packets exceed the maximum size for the network.

datagram

A UDP message at the Transport layer.

logical topology

A characteristic of network transmission that reflects the way in which data is transmitted between nodes, including how access to the network is controlled and how specific resources are shared on the network. A network's logical topology may differ from its physical topology.

knowledge base

A collection of accumulated insights and solutions to the problems encountered on a particular network.

IMAP4 (Internet Message Access Protocol, version 4)

A mail retrieval protocol that allows users to store messages on the mail server. The most current version of IMAP is version 4 (IMAP4).

MAC (Media Access Control) address

A method of access control where resources are organized into hierarchical classifications, such as "confidential" or "top secret," and grouped into categories, perhaps by department. Users, then, are also classified and categorized. If a user's classification and category match those of a resource, then the user is given access.

hybrid topology

A physical topology that combines characteristics of more than one simple physical topology.

IP address

A unique Network layer address assigned to each node on a TCP/IP network. IPv4 addresses consist of 32 bits divided into four octets, or bytes. IPv6 addresses are composed of eight 16-bit fields, for a total of 128 bits.

AD (Active Directory)

The centralized directory database that contains user account information and security for the entire group of computers on a network.

API (application programming interface) call

The process an application uses to make a request of the OS.

encapsulation

The process of adding a header to data inherited from the layer above.

Data Link layer

The second layer in the OSI model. The Data link layer, also called the Link layer, bridges the Physical layer's networking media with Network layer processes.

Application layer

The seventh layer of the OSI model. Application layer protocols enable software programs to negotiate formatting, procedural, security, synchronization, and other requirements with the network.

IP (Internet Protocol)

A core protocol in the TCP/IP suite that operates in the Network layer of the OSI model and provides information about how and where data should be delivered. IP is the subprotocol that enables TCP/IP to internetwork.

catastrophic failure

A failure that destroys a component beyond use.

network

A group of computers and other devices (such as printers) that are connected by and can exchange data via some type of transmission media, such as a cable, a wire, or the atmosphere.

LAN (local area network)

A network of computers and other devices that typically is confined to a relatively small space, such as one building or even one office. Each node on a LAN can communicate directly with others on the same LAN.

MAN (metropolitan area network)

A network of connected LANs within a limited geographical area, such as multiple city government buildings around a city's center.

CAN (campus area network)

A network of connected LANs within a limited geographical area, such as the buildings on a university campus.

client-server network model

A network where resources are managed by the NOS via a centralized directory database.

emergency alert system

A system that typically generates loud noise and flashing lights in response to a fire or other environmental threat. The system might also be able to send alert messages to key personnel or make network-wide announcements.

bus topology

A topology in which a single cable connects all nodes on a network without intervening connectivity devices.

connection-oriented protocol

A type of Transport layer protocol that requires the establishment of a connection between communicating nodes before it will transmit data.

connectionless protocol

A type of Transport layer protocol that services a request without requiring a verified session and without guaranteeing delivery of data.

mesh topology

A type of network in which several nodes are directly interconnected and no single node controls communications on the network.

fail open

System default that allows access during a system or network failure.

fail close

System default that denies access during a system or network failure.

AD DS (Active Directory Domain Services)

The Active Directory service that manages the process allowing a user to sign on to a network from any computer on the network and get access to the resources that Active Directory manages.

HTTPS (HTTP Secure)

The URL prefix that indicates a web page requires its data to be exchanged between client and server using SSL or TLS encryption.

frame

The entire Data Link layer message, including the header, payload, and trailer.

Network layer

The third layer in the OSI model. The Network layer, sometimes called the Internet layer, is responsible for moving messages between networks.

ESD (electrostatic discharge)

The transfer of electrical charge between two bodies, such as when a technician touches a computer component.