Computing Systems & Networks

Computing Systems & Networks

You will learn how computer systems & networks (mostly the Internet) work. You will learn how information is transmitted on the Internet & about the safeguards that have been put in place to keep this system from breaking down.

Computing Systems

A computing device is a physical artifact that can run a program (computers, tablets, servers, smart scensors, etc). A computing system is when various types of computing devices plus software, work together, for a use (such as managing the power grid, traffic signals, a smart home, or a network such as the Internet). Anytime two devices are connected & can send/receive data, a computer network has been created. This connection creates paths. Routers are computing devices along a path that send (route) the information along to the next stop on the path.

Computing Systems (contined)

Bandwidth of a computer network is the maximum amount of data that can be sent in a fixed amount of time (it is measured in bits per second).

Multiple Choice

What is a computer network?

• A set of IP addresses needed to access other computers

• Web pages that can be shared globally

• A dedicated line from one computer to another

• A way to connect devices to share data

Multiple Choice

What are the connected steps between a sending and a receiving location called?

• route

• conduit

• path

• protocol

Multiple Choice

What is bandwidth?

• How long it takes 10 megabytes of data to be sent.

• The delay in how long it takes between requesting & loading a web page.

• The amount of data divided by the latency.

• The amount of data that can be sent in a fixed period of time.

How the Internet Works

The Internet is a network of networks that uses standardized, open communication protocols. The word came from "interconnection of computer networks". It is very hardware-driven with wires, cables, and devices such as routers and servers. While some connections are wireless, there are still access points and cables that create the wireless network.

Packets & Data Streams

Data streams are information transmitted via the Internet. The processing of Internet traffic is done at the sending & receiving locations. At the sending location, the information to be sent (ex: webpage, email, music file, etc.) is broken into smaller packets of the same size (last one could be smaller). Header information is attached that includes the destination address & where to place the packet in the final reconstruction of the data stream. The packets are sent on their way to the destination via different routes. The intermediate routers along the path move the packets to the next destination. The packets arrive at different times in order, out of order, or not at all. Then they are reassembled. See example on the next slide.

Protocols

Every device on a network is called a "node" or "host". When a device connects to the Internet, it is given an "address" similar to the the idea of a mailing address. The nodes or devices can be anywhere in the world. The addresses enable devices to find and communicate with each other. The address is called an IP (Internet Protocol) address. It's how the Internet knows where to route information. Protocols are a set of rules that are agreed upon & specify the behavior of a system. These are needed so different equipment made by different companies can communicate with each other. Whether a connection is wired or wireless, before the packets can travel, a common protocol for transmitting & receiving the packets, must be used.

Protocols (continued)

Protocols are created by a team of representatives from different industries who agree on the set of rules for everyone to follow. The committee (tem) is the Internet Engineering Task Force (IETF). The Internet does not belong to any one country or individual, but its use needs to be agreed on and managed. These standards are continually reviewed and modified as needed and to add new hardware & other tools to its structure. The capacity for the system to change in size and scale to meet new demands is called scalability.

Common protocols used on the Internet are IP, TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). The protocols used in the Internet are open, which allows users to easily connect additional devices to the Internet.

Multiple Choice

Why is the Internet routing usually dynamic?

• So that it can speed up or slow down as necessary to avoid data congestion

• So that new routes can be tested in beta mode before being available globally.

• So that if a path on the route is congested or not working, a new path can be assigned.

• So that as data on a route becomes larger, traffic can be limited until it reaches acceptable levels.

Multiple Choice

What is the name for the protocol that handles processing at the sending & receiving locations?

• Local Area Network Protocol

• Point-to-Point Protocol

• Transmission Control Protocol

• Redundancy Protocol

Multiple Choice

What is the number assigned to devices on the Internet?

• Internet Protocol address

• Domain name

• Host name

• Router location

Multiple Choice

How do packets know how to get to their destination?

• The router knows the path & sends it step-by-step to its destination

• Each packets header tells the destination for the router

• Each path has an embedded code that directs the packets to its location

• The destination IP address is included in each packet

World Wide Web

The WWW is an application that runs on the Internet. The WWW is a collection of web pages, documents, and files, written in hyper-text markup language (HTML). Web browsers read the HTML code to know how to display the web page with colors, formatting, images, videos, lists, and more. HTTP (Hypertext Transfer Protocol) is used by the World Wide Web. It controls how a web pages data is requested, sent, & received from the browsers & servers where the web pages are stored. For secured transactions, such as finiancial and medical data, or those requiring passwords, HTTPS should be used.

Fault Tolerance

With the Internet, redundancy is a good thing. There is a lot of redundancy (duplication) built into the Internet on purpose. It is built in by providing multiple paths between devices on the Internet. This means that if one point goes down and doesn't work, then the traffic will be redirected to a different path to get to its destination. It is referred to as "fault tolerant" due to these multiple connections & paths. It is also abstraction because we don't know where all the connections are and how paths are determined, we just know it works. Fault tolerance increases the reliability of the Internet. The redundancy built in makes it scalable to meet the demand of more devices & people connecting to it. It costs more to build this fault tolerant system, but is needed for reliability & convenience.

Multiple Choice

Why is the Internet considered to be fault-tolerant?

• It has dedicated lines between devices

• It is secured against all threats

• It has duplicate paths to all locations

• It is open to anyone with a connection

Multiple Choice

What is the World Wide Web?

• Another name for the Internet

• A browser

• A way to search for and share documents & resources

• Provides the Internet

Types of Processing

1) Sequential Computing Systems - with this model, the operations execute one after the other in order. This model is more than suffiecient for what we do on local devices. However, it is not efficient for certain organizations because this type of system cannot scale since it runs step by step.

Types of Processing (continued)

2) Parallel Computing Systems -this model is where the program is broken into multiple smaller sequential computing operations. Each runs its section of sequential steps. The steps are executed simultaneously (in parallel), reducing the overall processing time needed. This also speeds up processing of very complex algorithms used by some organizations. More computers & processers can be added to scale up & reduce amount of time to run the program (to a certain point). The "speedup" of a parallel solution is measured in the time it took to complete the task (sequentially) divided by the time it took to complete the task when done in parallel.

Types of Processing (continued)

3) Distributed Computing Systems - another model often used for very large data sets by using multiple devices. This model can handle the speed & memory requirements for heavy-duty processing needs. The data is spread out among multiple computers. Each computer runs the same program on its section of data at the same time. There could be hundreds of thousands of computers involved in this type of processing system.