Computer Science: Internet and Networks
How data moves, devices connect, and networks communicate
Computer Science: Internet and Networks
How data moves, devices connect, and networks communicate
CS - Grade 9-12
- 1
Explain the difference between the Internet and the World Wide Web. Include one example of something that uses the Internet but is not the Web.
Think of the Internet as the roads and the Web as one type of service that travels on those roads.
The Internet is the global network of connected devices and networks. The World Wide Web is a service that uses the Internet to access websites through browsers. Email, online gaming, file transfer, and video calls can use the Internet without being the Web. - 2
A student types www.example.com into a browser. Describe the role of DNS in helping the browser connect to the correct website.
DNS translates the human-readable domain name www.example.com into an IP address that computers can use to locate the server. After the browser receives the IP address, it can send requests to the correct server. - 3
A file is split into packets before being sent across the Internet. Explain why packet switching is useful.
Consider what happens if one road is blocked but other roads are still open.
Packet switching is useful because packets can travel across different routes and be reassembled at the destination. This makes networks more efficient and reliable because one failed route does not have to stop the entire message. - 4
A network connection has a bandwidth of 50 megabits per second. About how long would it take to download a 500 megabit file under ideal conditions? Show your calculation.
It would take about 10 seconds because 500 megabits divided by 50 megabits per second equals 10 seconds. Real downloads may take longer because of overhead, congestion, and server limits. - 5
Describe the difference between bandwidth and latency in a network. Give an example where low latency is especially important.
Bandwidth is like how many cars fit on a road at once. Latency is like how long it takes the first car to arrive.
Bandwidth is the amount of data that can be sent per second, while latency is the delay before data begins to arrive or a response is received. Low latency is especially important for video calls, online gaming, remote control systems, and live collaboration. - 6
In the diagram, four routers connect a laptop to a web server. The possible routes are A-B-D, A-C-D, and A-E-D. If router B fails, explain what a well-designed network can do to keep communication working.
A well-designed network can route packets through another available path, such as A-C-D or A-E-D. This redundancy helps the network keep working even when one router or link fails. - 7
An IPv4 address has the form 192.168.1.25. Explain what an IP address is used for and why devices on a network need addresses.
Compare it to a mailing address for digital messages.
An IP address identifies a device or network location so data can be sent to the correct destination. Devices need addresses so routers and other devices know where packets should go and where responses should be returned. - 8
Explain one important difference between IPv4 and IPv6.
IPv4 uses 32-bit addresses, which allows about 4.3 billion unique addresses. IPv6 uses 128-bit addresses, which allows a much larger number of unique addresses and helps support the growing number of Internet-connected devices. - 9
A home router uses NAT, or Network Address Translation. Explain why NAT is useful for a home network.
Think about several phones, laptops, and game consoles sharing one Internet connection.
NAT allows multiple devices on a home network to share one public IP address when communicating with the Internet. It also helps separate private local addresses from public Internet addresses. - 10
Put these steps in the correct order for loading a secure web page: browser sends HTTPS request, DNS returns an IP address, user enters a domain name, browser connects to the server, encrypted page data is returned.
The correct order is: user enters a domain name, DNS returns an IP address, browser connects to the server, browser sends an HTTPS request, and encrypted page data is returned. - 11
A user connects to public Wi-Fi at a coffee shop. Identify two security risks and one safe practice the user should follow.
Public networks are shared with people you do not know.
Two security risks are that attackers may intercept unencrypted traffic or create a fake hotspot that looks legitimate. One safe practice is to use HTTPS websites, a trusted VPN, and avoid entering sensitive information unless the connection is secure. - 12
Explain the purpose of the TCP protocol when data is sent over a network.
TCP helps provide reliable communication by checking that packets arrive, requesting retransmission of missing packets, and putting packets back in the correct order. This is useful for tasks where accuracy matters, such as loading web pages or sending files. - 13
UDP is often used for live video, voice chat, and online games. Explain why an application might choose UDP instead of TCP.
In a live call, a late packet may be less useful than the next current packet.
An application might choose UDP because it has lower overhead and can be faster than TCP. For live video, voice chat, or games, receiving data quickly can be more important than retransmitting every missing packet. - 14
The diagram shows two networks connected by a router. Network 1 uses addresses 192.168.1.x, and Network 2 uses addresses 192.168.2.x. Explain the router's job when a computer on Network 1 sends data to a computer on Network 2.
The router examines the destination IP address and forwards the packet from Network 1 to Network 2. Its job is to move data between different networks using addressing and routing information. - 15
A school's network becomes slow during lunch when many students stream video. Explain what network congestion is and name one way the school could reduce it.
Congestion is similar to a traffic jam when too many cars try to use the same road.
Network congestion happens when more data is trying to move through the network than it can handle efficiently, causing delays, buffering, or packet loss. The school could reduce it by increasing bandwidth, limiting high-data applications, improving Wi-Fi access points, or using traffic management rules.