lecture 2 Flashcards
Types of Operating Software/Platforms
Windows, Unix/ Linux/Red Hat/ Ubuntu, Apple iOS, Android, Mac
What do Operating systems do?
recognizinginput fromkeyboard
sendingoutput to thedisplay screen
keeping track offiles and directories on thedisk,
controllingperipheral devices such as disk drives andprinters.
It controls and allocates computer resources -
What is an application?
Performs a specific function directly for the user or, in some cases, for another application program.
Desktop Applications
- A desktop application means any software that can be installed on a single computer (laptop or a desktop) and used to perform specific tasks. Some desktop applications can also be used by multiple users in a networked environment.
Web Apps
A web application is a computer program that utilizes web browsers (google chrome, Microsoft explorer/edge) and web technology (Windows Server 2019 and Windows 10, HTTPS, FTP, SSH, etc.) to perform tasks over the Internet. The web application requires a web server to manage requests from the client, an application server to perform the tasks requested, and, sometimes, a database to store the information. Web applications give businesses the ability to streamline their operations, increase efficiency, and reduce costs.
Advantages of Web apps
working across multiple platforms, having a broader reach, and being easily accessible from anywhere.
How are web app development usually made?
Web application development is usually made on client-server architecture and uses a web browser as the client interface.
What are network layers?
framework that helps to understand complex network interactions.
The two models of Network Layers
Open Systems Interconnection (OSI) and Transmission Control Protocol/Internet Protocol (TCP/IP)
What is the OSI model?
model is a conceptual framework that describes networking or telecommunications systems as seven layers, each with its own function. OSI model remains relevant, especially when it comes to SECURITY and determining where technical risks and vulnerabilities may exist.
What are the seven OSI Layers
Layer 1 (Physical):
Layer 2 (Data Link):
Layer 3 (Network):
Layer 4 (Transport):
Layer 5 (Session):
Layer 6 (Presentation):
Layer 7 (Application):
Physical (layer 1)
Actual hardware & communication medium and the technologies to transmit data across that medium sit. (eg., fiber optic cables, Bluetooth)
Data Link (layer 2)
The data link layer refers to the technologies used to connect two machines across a network where the physical layer already exists and allows upper layers to access media - (e.g., MAC Device - switches)
Network (Layer 3)
This layer determines how data is sent to the receiving device. It’s responsible for packet forwarding, routing, and addressing across a dispersed network or multiple connected networks of nodes or machines.– the flow control (e.g., IP, routers). Across the internet, the Internet Protocol v4 (IPv4) and IPv6 are used as the main network layer protocols.
Transport (Layer 4)
This layer coordinates data transfer between system and hosts, including error-checking and data recovery - (e.g., TCP, UDP, port numbers).
The primary focus of the transport layer is to ensure that data packets arrive in the right order, without losses or errors, or can be seamlessly recovered if required.
Session (layer 5)
This layer establishes and terminates connections between devices. The session layer is responsible for network coordination between two separate applications in a session. A session manages the beginning and end of a one-to-one application connection and synchronization conflict.
It also determines which packets belong to which text and image files - (e.g., Syn/Ack)
Presentation (Layer 6)
The presentation layer prepares data for the application layer. It defines how two devices should encode, encrypt, and compress data so it is received correctly on the other end. The presentation layer takes any data transmitted by the application layer and prepares it for transmission over the session layer.. This allows the different layers to understand each other - (e.g., encryption) -
Application (layer 7)
Most of what the user interacts with is at this layer. Web browsers and other internet-connected applications (like Skype or Outlook) use Layer 7 application protocols - (e.g., SNMP, HTTP, FTP) - The application layer is used by end-user software such as web browsers and email clients.
What is TCP/IP
assumes that applications will take care of everything beyond the Transport layer. The TCP/IP model also squashes the OSI’s Physical and Data Link layers together into the Network Access Layer. Internet Protocol really doesn’t (and shouldn’t) care about the hardware underneath, so long as the computer can run the network device and send IP packets over the connection. The modern Internet is not based on OSI, but on the simpler TCP/IP model was created by the US Department of Defense (DoD).
TCP/IP Layers
Network Access (or Link)
Internet
Transport (or Host-to-Host)
Application (or Process)
Network access (layer 1)
Also called the Link or Network Interface layer. This layer combines the OSI model’s L1 and L2.
Internet (layer 2)
Similar to the OSI model’s L3
Transport (layer 3)
Also called the host-to-host layer. Similar to OSI model’s Layer 4.
Application (layer 4)
Also called the Process layer, this layer combines the OSI model’s L5, L6, and L7.
What is a protocol
In computer networking, a protocol defines a standard way for computers to exchange information
TCP
is a connection-oriented protocol, which means that if two devices would like to communicate or talk to each other (share data or message) via TCP they have to send formal messages to each other to set up the connection before any data can be transmitted. TCP keeps track of what is sent and in order and if anything, that is received is out of order on the other end it can be pieced back together in its correct form. For example - You can liken a TCP connection to a telephone connection. With a telephone connection you first need to setup the connection by dialing the number, and once the calling party answers you have a both way communications channel. You then proceed to speak and once done you hang up the connection.
UDP
is connectionless there’s no formal start up process to set up a communication to another device, so there’s no formal teardown process for the flow. UDP simply sends information to another device without any type of warning whatsoever. It is usually called an unreliable protocol. Station really have no idea if the information got to the other side or not. Generally, the applications that are using UDP don’t care if all that information got to the other side. There is no acknowledgements back or tracking. For example - You can liken UDP to email or the normal post. With email or a written message, you send your message, but have no idea whether that message was received.
What are Ports
the networkportidentifies theapplication or servicerunning on the computer. In computer networking, a port is an endpoint (combination of IP address and Port #) of communication between various software and applications. Physical as well as wireless connections are terminated at ports of hardware devices. Every specific process or a type of network service resides in port. Generally, one port is used to send data and another to receive it, so packets don’t collide.
