Computer Systems and Networks · ⁨מערכות מחשב ורשתות⁩

Enduring Understanding (CSN-1): Computer systems and networks facilitate the transfer of data.

Learning Objective CSN-1.A: Explain how computing devices work together in a network. [Skill 5.A]

• CSN-1.A.1 A computing device is a physical artifact that can run a program. Some examples include computers, tablets, servers, routers, and smart sensors.
• CSN-1.A.2 A computing system is a group of computing devices and programs working together for a common purpose.
• CSN-1.A.3 A computer network is a group of interconnected computing devices capable of sending or receiving data.
• CSN-1.A.4 A computer network is a type of computing system.
• CSN-1.A.5 A path between two computing devices on a computer network (a sender and a receiver) is a sequence of directly connected computing devices that begins at the sender and ends at the receiver.
• CSN-1.A.6 Routing is the process of finding a path from sender to receiver.
• CSN-1.A.7 The bandwidth of a computer network is the maximum amount of data that can be sent in a fixed amount of time.
• CSN-1.A.8 Bandwidth is usually measured in bits per second.

Learning Objective CSN-1.B: Explain how the Internet works. [Skill 5.A]

• CSN-1.B.1 The Internet is a computer network consisting of interconnected networks that use standardized, open (nonproprietary) communication protocols.
• CSN-1.B.2 Access to the Internet depends on the ability to connect a computing device to an Internet-connected device.
• CSN-1.B.3 A protocol is an agreed-upon set of rules that specify the behavior of a system.
• CSN-1.B.4 The protocols used in the Internet are open, which allows users to easily connect additional computing devices to the Internet.
• CSN-1.B.5 Routing on the Internet is usually dynamic; it is not specified in advance.
• CSN-1.B.6 The scalability of a system is the capacity for the system to change in size and scale to meet new demands.
• CSN-1.B.7 The Internet was designed to be scalable.

Learning Objective CSN-1.C: Explain how data are sent through the Internet via packets. [Skill 5.A]

• CSN-1.C.1 Information is passed through the Internet as a data stream. Data streams contain chunks of data, which are encapsulated in packets.
• CSN-1.C.2 Packets contain a chunk of data and metadata used for routing the packet between the origin and the destination on the Internet, as well as for data reassembly.
• CSN-1.C.3 Packets may arrive at the destination in order, out of order, or not at all.
• CSN-1.C.4 IP, TCP, and UDP are common protocols used on the Internet.

Learning Objective CSN-1.D: Describe the differences between the Internet and the World Wide Web. [Skill 5.A]

• CSN-1.D.1 The World Wide Web is a system of linked pages, programs, and files.
• CSN-1.D.2 HTTP is a protocol used by the World Wide Web.
• CSN-1.D.3 The World Wide Web uses the Internet.

Enduring Understanding (CSN-1): Computer systems and networks facilitate the transfer of data.

Learning Objective CSN-1.E: For fault-tolerant systems, like the Internet: a. Describe the benefits of fault tolerance. [Skill 1.D] b. Explain how a given system is fault-tolerant. [Skill 5.A] c. Identify vulnerabilities to failure in a system. [Skill 1.D]

• CSN-1.E.1 The Internet has been engineered to be fault-tolerant, with abstractions for routing and transmitting data.
• CSN-1.E.2 Redundancy is the inclusion of extra components that can be used to mitigate failure of a system if other components fail.
• CSN-1.E.3 One way to accomplish network redundancy is by having more than one path between any two connected devices.
• CSN-1.E.4 If a particular device or connection on the Internet fails, subsequent data will be sent via a different route, if possible.
• CSN-1.E.5 When a system can support failures and still continue to function, it is called fault-tolerant. This is important because elements of complex systems fail at unexpected times, often in groups, and fault tolerance allows users to continue to use the network.
• CSN-1.E.6 Redundancy within a system often requires additional resources but can provide the benefit of fault tolerance.
• CSN-1.E.7 The redundancy of routing options between two points increases the reliability of the Internet and helps it scale to more devices and more people.

Enduring Understanding (CSN-2): Parallel and distributed computing leverage multiple computers to more quickly solve complex problems or process large data sets.

Learning Objective CSN-2.A: For sequential, parallel, and distributed computing: a. Compare problem solutions. [Skill 1.D] b. Determine the efficiency of solutions. [Skill 1.D]

• CSN-2.A.1 Sequential computing is a computational model in which operations are performed in order one at a time.
• CSN-2.A.2 Parallel computing is a computational model where the program is broken into multiple smaller sequential computing operations, some of which are performed simultaneously.
• CSN-2.A.3 Distributed computing is a computational model in which multiple devices are used to run a program.
• CSN-2.A.4 Comparing efficiency of solutions can be done by comparing the time it takes them to perform the same task.
• CSN-2.A.5 A sequential solution takes as long as the sum of all of its steps.
• CSN-2.A.6 A parallel computing solution takes as long as its sequential tasks plus the longest of its parallel tasks.
• CSN-2.A.7 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.

Learning Objective CSN-2.B: Describe benefits and challenges of parallel and distributed computing. [Skill 1.D]

• CSN-2.B.1 Parallel computing consists of a parallel portion and a sequential portion.
• CSN-2.B.2 Solutions that use parallel computing can scale more effectively than solutions that use sequential computing.
• CSN-2.B.3 Distributed computing allows problems to be solved that could not be solved on a single computer because of either the processing time or storage needs involved.
• CSN-2.B.4 Distributed computing allows much larger problems to be solved quicker than they could be solved using a single computer.
• CSN-2.B.5 When increasing the use of parallel computing in a solution, the efficiency of the solution is still limited by the sequential portion. This means that at some point, adding parallel portions will no longer meaningfully increase efficiency.