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Course: AP®︎/College Computer Science Principles > Unit 2
Lesson 8: The Internet protocol suiteThe Internet protocol suite
As we've seen over the course of this unit, there are many protocols that power the Internet. Each protocol operates at a different layer, building functionality on top of the layer below it.
The layers of Internet protocols are often visualized in a diagram like this:
That diagram is by no means complete. There are many more protocols in the Internet protocol suite—especially at the application layer—such as SMTP for sending email and FTP for uploading files.
Let's review protocols at each layer and their contributions to the Internet.
Layer by layer
At the bottom layer, two computing devices need a physical mechanism to send digital data to each other. They send electromagnetic signals either over a wired or wireless connection and interpret the signal as bits. The type of physical connection affects the bit rate and bandwidth.
Once a network is bigger than two computers, we need addressing protocols to uniquely identify who is sending data and who should receive the data. Every node on the Internet is identified with an IP address.
The route between any two computers on the Internet isn't just a straight path from A to B. The data must pass from router to router until it finally reaches its destination, a strategy that comes from the Internet routing protocol.
Data needs to be broken up into small packets, which are then reassembled at the destination. The Transmission Control Protocol (TCP) is used to ensure reliable transport of those packets, with sequencing, acknowledgement, and retries. A faster but less reliable transport protocol is the User Datagram Protocol (UDP).
There are many uses for the data flowing around the Internet, such as sending emails, uploading files, or chatting online. The most common use of the Internet is the World Wide Web, with its millions of publicly viewable websites, all made possible due to the HyperText Transfer Protocol (HTTP).
We can visit a website by typing a domain name in the browser address bar, since the browser knows how to turn the domain into an IP address using the Domain Name System (DNS).
When the data contains private information, it needs to be transported securely from the sender to the destination. The Transport Layer Security (TLS) protocol uses algorithms to encrypt the data, while certificate authorities help users trust the encryption.
A protocol stack
When a message is sent through the Internet, it doesn't use every protocol in the suite. It does use at least one protocol from every layer, however.
When you're loading a webpage from a domain your browser has never visited before, your browser may need to make a DNS request. This stack of protocols is used when a DNS request is sent through the Internet:
Then your browser will make an HTTP request to fetch the webpage. This protocol stack is used when an HTTP request is sent through the Internet:
If the webpage is served over HTTPS, then the stack includes multiple protocols at the application layer (both HTTP and TLS):
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Wow, with all of the layers the machines have to use to communicate, I'm just impressed that the internet works at all! (or that it was invented :)).(58 votes)
I may have missed it but I'm not sure how the most efficient server/host route is initially established. Is that done by a general broadcast out through the entire network and then progressively improves the routing efficiency by timing measurements?(6 votes)
Packets may not travel via the most efficient/optimal path. A protocol called Border Gateway Protocol (BGP), however, uses a local broadcast to communicate with nearby nodes and generally forms the basis of how a path is established.
Since nodes can go online/offline (e.g. Internet outage), the protocol supports changing network graphs. So at any given time, the path constructed by the protocol may not be "optimal".
Additionally, the idea of "most efficient" depends on the method of comparison. One metric behind the "best" path is timing, but others might be based on shortest physical distance or avoiding inter-ocean/satellite network links.
Hope this helps!(11 votes)
What is the point of making some protocols "reliable" and some "unreliable", do we have any control over this when we create a new protocol?(3 votes)
A reliable protocol is used to ensure every packet is received, but in some cases, it may not make a huge difference if some of the packets are lost and we want to avoid the extra overhead of ensuring reliable delivery. When downloading an application, for example, we need all of the packets, otherwise, the application will not work correctly. On the other hand, if we are in a video chat, we want the audio/video to update in almost real-time and it would be better if the audio cuts out for a split second than if the video chat were to pause for several seconds to wait for the next packet in the sequence.(10 votes)
The text says, "The data must pass from router to router..." I'm assuming this doesn't mean like my router. I googled, and one site says that the packets travel through many different Internet Service Providers. However, there are a lot of contradictions and nonspecific answers. So does anyone know the exact name of the computer that receives and keeps sending packets?(5 votes)
If I read your question correctly, that would be the ISP's routers like you had said. They would be located at datacenters and would contain the needed services to support transport of data. Hope this helps!(3 votes)
How do you change your avatar. I have 10000 energy points but i can't evolve my character(4 votes)- Click on your name in the top right corner of your screen to open your profile. Click on the avatar next to your name on that page. There should be a pop up with all of the options you have earned. Hope this helps!(2 votes)
What's the rule of IPv6 addresses?(3 votes)
IPv6 addresses are a type of internet protocol (IP) address used to identify devices on a network.
They are designed to provide a larger pool of unique addresses than the previous IPv4 standard, which is becoming increasingly depleted. This allows for more devices to be connected to the internet and provides improved security and network management capabilities.
Additionally, IPv6 addresses support new features and technologies that are not possible with IPv4, such as simpler network configuration, auto-configuration of devices, and better support for mobile devices.(3 votes)
- Plz correct me if I am wrong: playing an online video game is different from using teh world wide web..right?
TIA(3 votes) 
Can the Internet Protocol Suite be used to build other websites?(1 vote)
You don't use protocols to build websites. You use protocols to use the internet and access websites from a browser. IE - retrieve the website from the correct server - protocols allow you to safely and reliable do this. To build a website you need to create a file - usually the file includes HTML, CSS and JavaScript depending on what you are building.(5 votes)
ᠴᠠᠨ ᠶᠥᠦ ᠫᠷᠥᠳᠦᠴᠡ ᠮᠥᠷᠡ ᠤ᠋ᠳᠡᠥᠰ ᠠᠪᠥᠦᠲ ᠴᠥᠮᠫᠦᠲᠡᠷ ᠰᠴ᠋ᠡᠨᠴᠡ ᠫᠯᠡᠠᠰᠡ ᠳᠥᠨᠲ ᠦᠨᠳᠡᠷᠰᠲᠠᠨᠳ ᠸᠡᠯᠯ ᠹᠷᠥᠮ ᠡᠨᠭᠯ᠋ᠰᠬ ᠠᠷᠲ᠋ᠴᠯᠡᠰ(3 votes)
I think DNS is when old computer calling router with strange old noise.(2 votes)- DNS is used to convert domain names (such as google.com) into IP addresses.
The sound old computers used to make while using the internet was caused by establishing a connection through a dial-up modem.(2 votes)
