CIS-3230 Exam 1

open systems interconnection reference model (OSI Model)

Referred to as the network model. European networks use this model but did not catch on in North America. Most networks today use the Internet Model. This model has 7 layers: (7)Application, (6)Presentation, (5)Session, (4)Transport, (3)Network, (2)Data Link, (1)Physical. ALL PEOPLE SEEM TO NEED DATA PROCESSING.

osi physical layer

Primarily concerned with transmitting data bits over a communication circuit. Defines the rules for how ones and zeros are transmitted like voltages of electricity, number of bits sent per second, and the cables and connectors used. Uses network cable connecting computer to the rest of the network.

osi data link layer

Manages the physical transmission circuit and transforms it into a circuit that is free of transmission errors as far as layers above are concerned. This layer must create and recognize message boundaries, that is, it must mark where a message starts and ends. As well as solve problems caused by damage, lost, or duplicate messages so that the next layers are shielded from transmission errors (error detection and correction). Handles when a device can transmit so two computers do not try at once. Uses Ethernet.

osi network layer

Performs routing. Determines the next computer to which the message should be sent and follows the best rout through the network and finds the full address for that computer if needed. Uses IP.

osi transport layer

Deals with end-to-end issues like entering and departing from the network. It establishes, maintains, and terminates logical connections for the transfer of data between original sender and the final destination of the message. It also breaks a large data transmission into smaller packets, ensures all packets sent, eliminates duplicate packets and controls flow control. Can also perform error checking. Uses TCP.

local area network (LAN)

A group of computers located in the same general area. It covers a defined small area like a floor, a building or a group of buildings. It supports high-speed data transmission; commonly operating 100 million bits per second (100 Mbps).

backbone network (BN)

Most LANs are connected to this. It is a larger central network; that connects several LANs, other BNs, MANs, and WANs. It typically spans from hundreds of feet to several miles ad provides very high-speed data transmission commonly 100-1,000 Mbps.

wide area network (WAN)

This connects BNs and MANs. Most organizations do not build these on their own. Organizations usually lease circuits from IXCs (AT&T, Sprint) and use that to transmit data. Circuits for this come in all types and sizes, typically it is hundreds or thousands of miles. Data transmission rates from 64 Kbps to 10 Gbps.

intranet

a LAN that uses the same technologies as the internet (Java, HTML) but is open to only those inside the organization.

extranet

a LAN that uses the same technologies as the internet (Java, HTML) but is provided to invited users outside the organization.

osi session layer

Responsible for managing and structuring all sessions. Must arrange for all desired and required services between session participants like logging on to circuit equipment, transferring files, and performing security checks. Session termination or abort a session prematurely. Session accounting to send bill to correct party.

osi presentation layer

Formats the data for presentation to the user. Accommodates to different interfaces on different computers to the application program can run. Like displaying, formatting, and editing user inputs and outputs.

osi application layer

End user's access to the network. Primary purpose is to provide a set of tools for application programs. Network monitoring and network management. Uses HTTP.

server

Stores data or software that can be accessed by the clients. Several servers may work together over the network with a client.

client

The input and output hardware device at the user's end of a communication circuit.

circuit

The pathway through which messages travel; typically copper wire but now fiber-optic cable and wireless transmission are becoming common.

components of a network

a server, client and a circuit.

peer-to-peer network (P2P)

A set of similar computers that share their data and software with each other.

file server

Stores data and software that can be used by computers on the network.

web server

Stores documents and graphics that can be accessed from any web browser, such as Firefox. Can respond to requests from computers on the network.

mail server

Handles and delivers email over the network.

internet model

A five-layer network model most commonly used: (5)Application, (4)Transport, (3)Network, (2) Data Link, (1) Physical. Has never been formally defined.

protocol

Each layer uses formal language. Simply a set of rules that define what the layer will do and that provides a clearly defined set of messages that software at the layer needs to understand. All layers expect physical create a Protocol Data Unit (PDU).

protocol data unit (PDU)

Contains information that is needed to transmit the message through the network.

standards

Necessary in almost every business and public service entity. Ensures that hardware and software produced by different vendors can work together. Allows customers to buy hardware and software from any vendor as long has it meets standards.

international organization for standardization (ISO)

One of the most important standards-making bodies is this organization. Based in Geneva, Switzerland.

application architecture

The way in which the functions of the application layer software are spread among the clients and servers in the network.

application program

Can be divided into four general functions. Data storage, data access logic, application logic, and presentation logic.

host-based architecture

The server/host computer performs virtually all the work.

client-based architecture

The client computers perform most of the work.

client-server architecture

The work is shared between the servers and clients.

peer-to-peer architecture

Computers are both clients and servers and thus share the work.

thin-client

This approach places little or no application logic on the client.

thick-client

This approach places all or almost all of the application logic on the client.

Software as a Service (SaaS)

An organization outsources the entire application to the cloud provider. Based on multitenancy (no copies of same application, one shared). Email (Gmail) is an example.

Platform as a Service (PaaS)

Originally made application as well as your own data on the cloud infrastructure provided by your cloud supplier. Needed software and hardware infrastructure is called the platform and rented from cloud provider. Offers a much faster development.

Infrastructure as a Service (IaaS)

Cloud provider manages hardware, including servers, storage, and networking components. Sometimes referred to as HaaS or Hardware as a Service because only the hardware is provided.

hyper text transfer protocol (HTTP)

The way data is transferred to an external site through a server. Web browser issues a special packet called HTTP request that contains the URL. When server receives the HTTP request it processes and sends back an HTTP response.

HTTP request

request line: starts with command, request header: contains a variety of optional info like web browser, request body: contains info sent to the server like info user typed.

HTTP response

response status: contains HTTP version number (404 means not found), response header: contains variety of optional info like web server or URL, response body: is the web page itself.

telnet

Enables users to log in to servers (or other clients). Requires an application layer program on the client computer and an application layer program on the server or host computer. Once connection is established you must use the account name and password of an authorized user to log in.

logical circuit

Used to connect two devices, which refers to the transmission characteristics of the connection.

modem

A device at the sender's computer translates the computer's digital data into analog data that can be transmitted through the voice communication circuits.

codec

A device that translates analog voice data into digital form for transmission over digital computer circuits.

simplex transmission

One-way transmission, such as that with radios and TVs.

half-duplex transmission

Two-way transmission, but you can transmit in only one direction at a time.

full-duplex transmission

You can transmit in both directions simultaneously, with no turnaround time.

multiplexing

To break one high-speed physical communication circuit into several lower-speed logical circuits so that many different devices can simultaneously use it but still "think" that they have their own separate circuits.

twisted pair cable

The most commonly used kind of networking cable today. Insulated pairs of wires that can be packed close together.

coaxial cable

Has a copper core with an outer cylindrical shell for insulation. Less prone to interference and errors than twisted pair wires. Cost 3x more.

fiber-optic cable

Uses a very thin glass or plastic fiber. Transmissions are pulses of light.

radio transmission

Uses radio-wave frequencies to send data directly between transmitters and receivers.

microwave transmission

A form of point-to-point wireless transmission over unbounded media in which signals are sent via pulses of electromagnetic energy in the
microwave region of the spectrum.

satellite transmission

A wireless transmission system that uses satellites for broadcast communications.

parallel transmission

Internal transfer of binary data takes place inside a computer.

serial transmission

A stream of data is sent over a communication circuit sequentially in a bit-by-bit fashion.

digital transmission

Transmission of binary electrical or light pulses in that it only has two possible states, 1 or 0.

analog transmission

Occurs when the signal sent over the transmission media continuously varies from one state to another in a wave-like pattern much like the human voice

amplitude

Height of a wave measured in decibels (dB).

frequency

Length of a wave measured in hertz (Hz).

phase

The direction in which a wave begins measured in degrees.

modulation

A technical term referred to as shape changes.

basic modulation

The height of the wave changed.

frequency modulation

A change in the frequency of a carrier wave.

phase modulation

Changing the direction in which a wave starts to signal a 0 or a 1.

bandwidth

The difference between the highest and lowest point of a signal.