Intro to Networking, Chapter 1

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.

Host

Anything with an IP address (Printers, Node, Land Phone, Work Stations, etc). (1) Any PC 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. A host on one (1) LAN cannot communicate with a host on another LAN without a router to manage that communication and stand as a gateway b/w the networks.

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.

NIC (Network Interface Card) and/or Network Adapter

Expansion card on the motherboard that enables a PC to connect to a network via a network cable and communicate with other PCs. A wireless NIC enables connection via radio waves rather than a physical cable.

Decapsulation

Removing a header or trailer from a lower OSI layer.

Personal Area Network (PAN)

Smallest network. A network of personal devices.

Ring Topology (*CompTia Net+ Exam Q)

Rarely used today b/c of its slow speed. Nodes are connected in a ring, with one node connecting only to its two neighboring nodes. A node can put data on the ring ONLY when it holds a token, which is a small group of bits passed around the ring. This is similar to the saying, "I hold the token, so I get to talk now." (A network layout in which each node is connected to the two (2) 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).

Logical Topology

(Has to do with software, how access to the network is controlled, including how users and programs initially gain access to the network, and how specific resources, such as applications and databases, are shared on the network). 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.

Physical Topology

(Mostly refers to a network's hardware and how PCs, other devices and cables fit together for form the physical network). 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.

The Seven (7) Layer OSI (Open System Interconnection) Model

7. Application Layer 6. Presentation Layer 5. Session Layer 4. Transport Layer 3. Network Layer 2. Data Link Layer 1. Physical Layer * OSI Model will help understand networking protocols & troubleshoot network problems. (Memorization = All People Seem To Need Data Processing OR Please Do Not Throw Sausage Pizza Away)

Data Link Layer Address Diagram / MAC (Media Access Control Address

A 48- or 64-bit network interface identifier that includes two parts: the OUI, assigned by IEEE to the manufacturer, and the extension identifier, a unique number assigned to each NIC by the manufacturer. (Hardware address)

Fragmentation

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

IMAP4 (Internet Message Access Protocol, Version 4)

A mail retrieval protocol that allows users to store messages on the mail server.

Switch vs. Router

Switch belongs ONLY to its local network. Router belongs to two (2) or more local networks.

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.

Client

A computer or application that makes a request from another computer or application. A computer making a request from another. (Clients on a client-server network network can run applications installed on the desktop and store their own data on local storage devices. Client's don't share their resources directly with each other; instead, access is controlled by entries in the centralized domain database. A client computer accesses resources on another computer by way of the servers controlling the database. A computer program that uses the services of another computer program. It is also software that extracts information from a server; your auto-dial phone is a client, and the phone company is its server. It is also a machine that accesses shared resources on a server.

Server

A computer that shares its resources, such as printers and files, with other computers on a network. Any computer or program that provides a service, such as data or other resources, to other devices. * Servers that have a NOS installed requires MORE memory, processing power and storage capacity than clients b/c servers are called on to handle HEAVY processing loads and requests from multiple clients.

Switch

A connectivity device that filters and forwards traffic based on some criteria. It receives incoming data from one of its ports and redirects (switches) it to another port or multiple ports that will send the data to its intended destination(s).

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.

Remote Desktop Services

A feature of Windows Server 2008 and later editions of Windows Server that allows technicians to manage remote applications. (Uses RDP (Remote Desktop Protocol) to provide secure, encrypted transmission that allow a technician to remote in - that is, to access a remote computer from the technician's local computer).

Metropolitan Area Network (MAN) or Campus Area Network (CAN)

A group of LANs in the SAME geographical area.

Wide Area Network (WAN)

A group of LANs that spread over a wide geographical area.

Network

A group of PCs and other devices (such as: cell phones, PCs, mainframe PCs, printers, corporate phone systems, security cameras, vehicles and wearable technology devices) that are connected by some type of transmission media (e.g., copper wires, fiber-optic cable or radio waves).

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.

P2P (Peer-to-Peer) Network Model

A network in which every PC can communicate directly with every PC. (Each machine can act as a client and a server). By default, no computer on a P2P network has more authority than another; each PC controls its own administration, resources and security. (Examples of OS that might be installed on PCs in a P2P network are: Windows, Linux and macOS on desktop/laptop PCs and iOS, Android, and BlackBerry on mobile devices). Pros: - Simple to configure. - Less expensive to setup/maintain. Cons: - They are not scalable - meaning as P2P network grows larger, adding or changing significant elements of the network may be difficult. - Not necessarily secure, meaning in simple installations, data and other resources shared by network users can be easily discovered and used by unauthorized people. - Not practical for connecting more than a few PCs b/c it is too time consuming to manage the resources on the network.

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. A LAN can have several switches. (Group of PCs connected via cabling, radio, or infrared that use this connectivity to share resources such as printers and mass storage).

CAN (Campus Area Network)

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

Emergency Alert System

A system that typically generates loud noise and flashing lights in response to a fire or 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.

Web Service

A type of Client-Server application. Serves up web pages to clients. Primary protocol used by web servers and browsers (clients) is HTTP (Hypertext Transfer Protocol).

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 each device connects to multiple other devices.

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.

HTTPS (HTTP Secure)

A variant of the standard web transfer protocol (HTTP) that adds a layer of security on the data in transit through a secure socket layer (SSL) or transport layer security (TLS) protocol connection.

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.

Remote Application

An application that is installed and executed on a server, and is presented to a user working at a client computer. (Becoming popular b/c most of the computing power (memory/CPU speed) and technical support (for application installations and updates and for backing up data) are focused on the server in a centralized location, which means the client computers require less computing power and desk-side support).

Header

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

Hub

An inefficient and outdated networking device that has been replaced by switches. This device belongs to the Physical layer of the OSI model and re-transmits incoming data signals to its multiple ports.

Node

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

Client-Server Applications

Data or a service requested by one computer from another. PCs on a network are able to communicate via protocols they have in common. (The 1st PC = a Client PC requests data or service from the 2nd PC, which is the server). Example: Web browser (client application) requests a web page from a web server (server application); the web server returns the requested data to the client.

Topology

How the parts of a whole work together.

Firmware

Programs embedded into hardware devices.

Telnet Service

Protocol used by the telnet client-server command-line application to allow an administrator or other user to "remote in" or control a computer remotely. Telnet is not encrypted and this is not secure.

Client-Server Network Model (AKA - Client-Server Architecture or Client-Server Topology)

A network where resources are managed by the NOS via a centralized directory database. The database can be managed by one or more servers, so long as they each have a similar NOS installed. Requires one or more NOSes (Network Operating Systems), which control access to the entire network. (Examples of NOSes: Windows Server 2016, Ubuntu Server, and Red Hat Enterprise Linux (Ubuntu and Red Hat are versions of Linux). *More complex in design and maintenance than P2P networks. Offer many advantages over P2P networks including: - User accounts/passwords to the network are assigned in one place. - Access to multiple shared resources (e.g., data files/printers) can be centrally granted to a single user or groups of users. - Problems on the network can be monitored, diagnosed, and often fixed from one location. - More scalable than P2P networks - easier to add PCs and other devices.

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.

Network Services

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

Protocol

A set of rules and methods governing the exchange or transmission of data between network devices. (Example: To handle a request for a web page, the client computer must first find the web server. Then, the client and server must agree on the protocols they will use to communicate. Finally, the client makes the request and the server sends its response in the form of a web page. Hardware, the OS, and the applications on both PCs are all involved in the process). 2 Primary Protocols: - TCP (Transmission Control Protocol) - IP (Internet Protocol) Suite of ALL the protocols an OS uses for communication on a network is the TCP/IP.

Email Services

Client-server application that involves two servers. The client uses SMTP (Simple Mail Transfer Protocol) to send an email message to the first server, which is sometimes called the SMTP server. The 1st server sends the message on the receiver's mail server, where it's stored until the recipient requests delivery. The recipient's mail server delivers the message to the receiving client using two (2) protocols: POP (Post Office Protocol, Version 3) or IMAP4 (Internet Message Access Protocol, Version 4).

Function of the OS (Operating System)

Controls how users and programs get access to resources on a network. Each OS is configured to use one of two models to connect to network resources: 1. Peer-to-Peer Model 2. Client-Server

Domain

In the context of Windows Server NOSes, a group of users, servers, and other resources that share account and security policies. (Groupings of users, computers, or networks. In Microsoft networking, a domain is a group of computers and users that share a common account database and a common security policy).

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 PC on the network and get access to the resources that Active Directory manages.

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."

Active Directory (AD)

The centralized directory database that contains user account information and security for the entire group of computers on a network. Each user on the network has his/her own domain-level account assigned by the network administrator & kept in Active Directory (AD). This account might be a local account, which is specific to that domain, or a Microsoft account, which links local domain resources with Microsoft cloud resources.

Frame

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

OSI - Layer 5: Session Layer

The fifth layer of the OSI model. * Session layer describes how data b/w applications is synced and recovered if messages do not arrive intact at the receiving application. (I.e., the Skype application works with the OS to establish & maintain a session between two end points for as long as a voice conversation or video conference is in progress. (The Application, Presentation & Session Layers are so intertwined that, in practice, it is often difficult to distinguish b/w them. Also, tasks for each layer may be performed by the OS or the Application. Most tasks are performed by the OS when an application makes an API call to the OS. API (Application Programming Interface) Call is the method an application uses when it makes a request of the OS.

OSI - Layer 1: Physical Layer

The first and the lowest layer of the OSI model. * Layers 2 and 1 are responsible for interfacing with the physical hardware only on the local network. (The protocols at Layers 2 and 1 are programmed into the firmware of a PCs NIC and other networking hardware). Simplest layer of all and is responsible ONLY for sending bits via a wired or wireless transmission. These bits can be transmitted as wavelengths in the air (e.g., Wi-Fi), voltage on a copper wire (e.g., Ethernet on twisted-pair cabling), or light (e.g., Ethernet on fiber-optic cabling). On the OSI model, ONLY the Data Link layer and Physical layers must deal with the details of wired vs. wireless transmissions on the firmware of the NIC.

OSI - Layer 4: Transport Layer

The fourth layer of the OSI model. Responsible for transporting Application layer payloads from one application to another. The two (2) main Transport layer protocols are: 1. TCP (Transmission Control Protocol) which guarantees delivery; and 2. UDP (User Datagram Protocol) which does NOT guarantee delivery by first connecting/checking whether data is received; thus, UDP is used connectionless protocol or best-effort protocol.

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 the data inherited from the layer above.

OSI - Layer 2: Data Link/Link Layer

The second layer in the OSI model. * Layers 2 and 1 are responsible for interfacing with the physical hardware only on the local network. (The protocols at these layers are programmed into the firmware of a PCs NIC and other networking hardware) Bridges the Physical layer's networking media with Network layer processes. The type of networking hardware or technology used on a network determines the Data Link layer protocol used. (Examples of Data Link layer protocols are Ethernet and Wi-Fi. - Ethernet works on wired networks and Wi-Fi is wireless). Several types of switches exist. The least intelligent (non-programmable) switches, which are called Data Link layer switches or Layer 2 switches, operate at this layer. The Data Link layer puts its own control information in a Data Link layer header and also attaches control information to the end of the packet in a trailer. The entire Data Link layer message is then called a frame.

OSI - Layer 7: 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. * Interface b/w two applications, each on separate PCs. Several protocols used at this layer (HTTP, SMTP, POP3, IMAP4, FTP, Telnet and RDP). Application layer protocols are used by programs that fall into two (2) categories: 1. Application programs that provide services to a user, such as browser and web server using the HTTP Application layer protocol. 2. Utility programs that provide services to the system, such as SNMP (Simple Network Mgmt Protocol) programs that monitor & gather info about network traffic and can alert network administrators about adverse conditions that need attention. Data passed b/w applications or utility programs and the OS is called a PAYLOAD and includes control information. The two (2) end-system PCs that initiate sending/receiving data are called HOSTS.

OSI - Layer 6: 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. (I.e., an email message can be encrypted at the Presentation layer by the email client or by the OS.

NOS (Network Operating System)

The software that runs on a server and enables the server to manage data, users, groups, security, applications, and other networking functions. The most popular are Windows Server, (Ubuntu Server and Red Hat Enterprise = Linux). The software that allows multiple computers to communicate, share files and hardware devices with one another. Responsible for: - Managing data and other resources for a number of clients. - Ensuring only authorized users access the network. - Controlling which types of files a user can open and read. - Restricting which rules computers will use to communicate.

OSI - Layer 3: Network/Internet Layer

The third layer of the OSI model. * Responsible for moving messages between networks. (From one node to another until they reach the destination host). The principle protocol used by the Network layer is IP (Internet Protocol). IP adds its own Network layer header to the segment or datagram, and the entire Network layer message is now called a PACKET. The Network layer header identifies the sending/receiving hosts by their IP addresses. (Post Office analogy - the Network layer would be the trucking system used by the Post Office and the IP addresses would be the full return and destination addresses written on the envelope). If a Network layer protocol is aware that a packet is larger than the maximum size for its network, it will divide the packet into smaller packets in a process called fragmentation.

ESD (Electrostatic Discharge)

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

Troubleshooting Network Problems

When troubleshooting problems with networking hardware, OS, or applications, follow these steps: 1. Identify the problem and its symptoms 2. Establish a theory of probable cause 3. Test your theory to determine the cause 4. Establish a plan for resolving the problem 5. Implement the solution or escalate the problem 6. Verify functionality and implement preventive measures 7. Document findings, actions, and outcomes