Introduction to Networking

UDP (User Datagram Protocol)

A core protocol in the TCP/IP suite that does not guarantee delivery because it does not first make the connection before sending data or check to confirm that data is received.

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.

TCP (Transmission Control Protocol)

A core protocol of the TCP/IP suite that makes a connection with the end host, checks whether data is received, and resends it if it is not.

catastrophic failure

A failure that destroys a component beyond use.

Remote Desktop Services

A feature of Windows Server 2008 and later editions of Windows Server that allows technicians to manage remote applications.

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.

star bus topology

A hybrid topology in which groups of workstations are connected in a star fashion to connectivity devices that are networked via a single bus.

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 IMAP4 is version 4 (IMAP4).

SSL (Secure Sockets Layer)

A method of encrypting TCP/IP transmissions—including Web pages and data entered into Web forms—en route between the client and server using public key encryption technology.

OSI (Open Systems Interconnection) model

A model for understanding and developing computer-to-computer communication developed in the 1980s by ISO. It divides networking functions among seven layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

SOHO (Small office/home office) networks

A network consisting of fewer that 10 workstations.

P2P (peer-to-peer) network model

A network in which every computer can communicate directly with every other computer. By default, no computer on a P2P network has more authority than another.

ring topology

A network layout in which each node is connected to the two nearest nodes so that the entire network forms a circle. Data is transmitted in one direction around the ring. Each workstation accepts and responds to packets addressed to it, then forwards the other packets to the next workstation in the ring.

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.

PAN (personal area network)

A network of personal devices, such as a cell phone, laptop, and Bluetooth printer.

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.

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 right 16-bit fields, for a total of 128 bits.

PDU (protocol data unit)

A unit of data at any layer of the OSI model.

TLS (Transport Layer Security)

A version of SSL standardized by the IETF (Internet Engineering Task Force). TLS uses slightly different encryption algorithms than SSL, but otherwise is very similar to the most recent version of SSL.

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.

physical topology

The physical layout of the media, nodes, and devices on a network. A physical topology does not specify device types, connectivity methods, or addressing schemes.

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.

scalable

The property of a network that allows you to add nodes or increase its size easily.

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.

Presentation layer

The sixth layer of the OSI model. Protocols in the Presentation layer are responsible for reformatting, compressing, and/or encrypting data in a way that the application on the receiving end can read.

NOS

The software that runs on a server and enables the server to manage data, users, groups, security, application, and other networking functions.

NOSes (networking operating systems)

The software that runs on a server and enables the server to manage data, users, groups, security, applications, and other networking functions. Popular examples include Windows Server, Ubuntu Server, and Red Hat Enterprise Linux.

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.

MAC (Media Access Control) address

Unique 48-bit address assigned to each network card. IEEE assigns blocks of possible addresses to various NIC manufacturers to help ensure that the address is always unique. The Data Link layer of the OSI model uses MAC addresses to locate machines.

PPE (personal protective equipment)

Wearable equipment such as goggles that might be required in the workplace to increase safety of workers.

OSHA (Occupational Safety and Health Administration)

The main federal agency charged with regulating safety and health in the workplace.

segments

(1) A TCP message at the Transport layer. (2) A part of a network.

host

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

router

A Layer 3 device that uses logical addressing information to direct data between two or more networks and can help find the best path for traffic to get from one network to another.

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 the 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.

client

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

SSH (Secure Shell)

A connection utility that provides authentication and encryption. SSH is often used to log onto a host, execute commands on that host, and copy files to or from the host.

WAN (wide area network)

A network that spans a long distance and connects two or more LANs.

client-server network model

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

port

A number that identifies a process, such as an application or service, running on a computer, TCP and UDP ports ensure that data is transmitted to the correct process among multiple processes running on a computer.

star topology

A physical topology in which every node on the network is connected through a central device.

hybrid topology

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

SFTP (Secure File Transfer Protocol)

A protocol available with the proprietary version of SSH that securely copies files between hosts.

network service

A resource the network makes available to its users, including application and the data provided by these applications.

network services

A resources the network makes available to its users, including application and the data provided by these applications.

protocol

A standard method or format for communication between network devices.

protocols

A standard method or format for communication between network devices.

TCP/IP

A suite of networking protocols that includes TCP, IP, UDP, and many others. TCP/IP provides the foundation for data exchange across the Internet.

Emergency Alert System

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

Telnet

A terminal emulation protocol used to log on to remote hots using the TCP/IP protocol.

bus topology

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

SMNP (Simple Network Management Protocol)

An Application layer protocol in the TCP/IP suite used to monitor and manage devices on a network.

SMTP (Simple Mail Transfer Protocol)

An Application layer protocol responsible for moving messages from one email server to another.

HTTP (Hypertext Transfer Protocol)

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

RDP (Remote Desktop Protocol)

An Application layer protocol that uses TCP/IP to transmit graphics and text quickly over a remote client-host connection. RDP also carries session, licensing, and encryption information.

POP3 (Post Office Protocol version 3)

An Application layer protocol used to retrieve messages from a mail server. When a client retrieves mail via POP, messages previously stored on the mail server are downloaded to the client's workstation, and then deleted from the mail server. The most commonly used form of POP is POP3.

FTP (File Transfer Protocol)

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

remote application

An application that is installed and executed on a server, and is presented to a user working at a client computer.

header

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

static electricity

An electrical charge at rest. When that charge is transferred between two bodies, it creates an electrostatic discharge, or ESD.

hub

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

server

Any computer or application that provides a service, such as data or other resources, to other devices.

node

Any computer or other device on a network that can be addressed on the local network.

Grounding

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

trailer

Control information attached to the end of a packet by the Data Link layer protocol.

upset failure

Damage that can shorten the life of a component and/or cause intermittent errors.

client-server application

Data or a service requested by one computer from another.

client-server applications

Data or a service requested by one computer from another.

payload

Data that is passed between application or utility programs and the operating system, and includes control information

topology

How the parts of a whole work together

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.

trip hazards

Items such as extension cords or tools lying on the ground in walkways that can cause someone to stumble.

firmware

Programs embedded into hardware devices.

Decapsulation

Removing a header or trailer from a lower OSI layer.

physical layer

The lowest, or first, layer of the OSI model. The Physical layer is responsible only for sending bits via a wired or wireless transmission.

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 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 that a Web page requires its data to be exchanged between client and server using SSL or TLS encryption. HTTPS uses the TCP port number 443.

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."

AD (Active Directory)

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

switch

The determination of how connections are created between nodes on a network.

NIC (Network Interface Card)

The device that enables a workstation to connect to the network and communicate with other computers. They are also called network adapters.

frame

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

packet

The entire Network layer message, which includes the segment (TCP) or datagram (UDP) from the Transport layer, plus the Network layer header.

Session layer

The fifth layer in the OSI model. The Session layer describes how data between applications is synced and recovered if messages don't arrive intact at the receiving application.

Transport layer

The fourth layer of the OSI model. The Transport layer is responsible for transporting Application layer payloads from one application to another.