Packet, routers, and reliability | Internet 101 | Computer Science | Khan Academy

Summary

In this video, Lynn Root, a Software Engineer at Spotify, discusses the Internet's reliability and the complex process behind data delivery. The script explains how the Internet Protocol (IP) and Transmission Control Protocol (TCP) work together to ensure data packets are sent, received, and reassembled correctly, even if they travel different routes or arrive out of order. The video highlights the Internet's fault tolerance and scalability, emphasizing its ability to grow without interrupting service.

Takeaways

• 🌐 The Internet's reliability is often taken for granted, yet it handles an astonishing amount of data efficiently.
• 🚀 Data on the Internet doesn't travel on direct, dedicated lines but through a less direct, packet-based system.
• 🛣️ Information travels in packets, which can change paths dynamically, similar to how one might choose different routes in a car based on traffic.
• 📦 Large files, like images, are broken down into smaller packets for transmission, which are then reassembled at the destination.
• 🔍 Routers act as traffic managers on the Internet, directing packets through the most efficient routes based on various factors.
• 🔁 Packets may take different routes and arrive out of order, but the system is designed to handle this and maintain data integrity.
• 🛡️ The Internet Protocol (IP) ensures that routers keep track of multiple paths, enhancing the network's fault tolerance.
• 🎵 TCP (Transmission Control Protocol) acts as a reliable mail service, ensuring all packets of a data request are delivered correctly.
• 🔄 If packets are missing or incomplete, TCP will request retransmission until all parts are successfully received.
• 🌟 The scalability of TCP and routers allows the Internet to function smoothly even as the number of devices grows exponentially.
• 🌐 The Internet's interconnectedness is facilitated by agreed-upon standards, allowing diverse systems to communicate effectively.

Q & A

What does Lynn Root admit to taking for granted about the Internet?

Lynn Root admits to often taking for granted the reliability of the Internet.

How does the Internet typically deliver data to users?

Data travels on the Internet in a less direct fashion, not through direct, dedicated connections, but rather through a system of packets that can take various routes to reach their destination.

Who is Bob Kahn and what was his contribution to the Internet?

Bob Kahn is Lynn Root's partner, and together they began working on the design of what we now call the Internet in the early 1970s, focusing on the Internet's protocols and architecture.

What is a packet in the context of the Internet?

A packet is a unit of data that travels from one computer to another on the Internet, similar to how a car travels from one place to another depending on traffic or road conditions.

How does the Internet handle large amounts of data, such as a large image?

Large amounts of data, like an image, are broken down into smaller parts called packets. These packets can take different routes and be reassembled at the destination.

What are routers and what role do they play in the Internet?

Routers are special computers on the Internet that act like traffic managers, keeping packets moving through the networks smoothly and choosing the best available path for each packet based on various factors.

What does 'cheapest' mean in the context of choosing a path for data packets?

'Cheapest' in this context refers to the most efficient path in terms of time and non-technical factors such as politics and relationships between companies, rather than monetary cost.

What is the Transmission Control Protocol (TCP) and how does it ensure data delivery?

TCP is a protocol that manages the sending and receiving of data packets. It ensures all packets are delivered by doing a full inventory upon arrival and sending back acknowledgements for each packet received. Missing packets are resent until all are accounted for.

How does the TCP protocol handle missing or incomplete packets?

If TCP detects missing or incomplete packets, it will request the sender, such as Spotify, to resend them. Only after TCP verifies the delivery of all packets will the data, like a song, start to play.

Why is the Internet considered scalable and reliable?

The Internet is scalable and reliable due to its principles of fault tolerance and redundancy. The system can work with a small or large number of devices, and adding more routers increases the network's reliability.

How do the different systems that make up the Internet communicate and work together?

The different systems on the Internet communicate and work together based on agreed-upon standards for how data is sent around, allowing for seamless data transfer across various networks and devices.

Outlines

00:00

🌐 Internet's Indirect Data Delivery

This paragraph introduces the concept of how the Internet delivers data in an indirect manner, contrary to the common misconception of direct connections. It explains that data travels in packets, similar to how one might choose different routes in a car based on traffic or road conditions. The paragraph also highlights the early development of the Internet by Bob Kahn and the narrator, emphasizing the importance of protocols and architecture in the Internet's design. It uses the analogy of transporting a space shuttle in pieces to illustrate how large data sets are broken down into smaller packets for transmission.

05:01

🔄 The Role of TCP in Internet Data Reliability

The second paragraph delves into the role of the Transmission Control Protocol (TCP) in ensuring the reliable delivery of data over the Internet. It describes TCP as a system that manages packet transmission, akin to a guaranteed mail service, where packets are sent, received, and acknowledged. The paragraph explains how TCP ensures all data packets are delivered correctly by requesting retransmission of any missing or incomplete packets. It also touches on the scalability and fault tolerance of the Internet, highlighting how the addition of routers enhances network reliability without disrupting service. The paragraph concludes by emphasizing the agreed-upon standards that allow diverse systems to communicate and function cohesively on the Internet.

Keywords

💡Internet

The Internet is a global network of interconnected computers and devices that communicate with each other using standardized protocols. It is the central theme of the video, as it discusses the reliability and functioning of the Internet. The script uses the term to describe the complex system that allows for the transfer of data, such as when playing a song from Spotify, which is not a direct connection but rather a series of interconnected networks.

💡Packet

In the context of the video, a packet refers to a unit of data that is sent over the Internet. It is the fundamental way information is transmitted, with each packet containing parts of a larger message. The script illustrates this with the analogy of a car, where packets, like cars on a road, may take different routes to reach their destination, and can arrive out of order but are reassembled at the destination.

💡Routers

Routers are specialized computers on the Internet that act as traffic managers, directing packets to their destinations. They are crucial to the video's theme of Internet reliability, as they determine the best path for data to travel based on various factors. The script explains that routers keep track of multiple paths and choose the most efficient one, contributing to the fault tolerance of the network.

💡TCP (Transmission Control Protocol)

TCP is a protocol that ensures the reliable transmission of data over the Internet. It is highlighted in the script as a 'guaranteed mail service' that manages the sending and receiving of data packets. TCP checks for missing packets and requests retransmission if necessary, ensuring that data, such as a song from Spotify, is delivered in its entirety and plays perfectly.

💡Reliability

Reliability in the video refers to the consistent and dependable delivery of data over the Internet. It is a key principle of the Internet's design, as explained by the script, which emphasizes the network's ability to keep sending packets even when something goes wrong. The script also mentions that the Internet's reliability is based on its fault tolerance and redundancy.

💡IP Address

An IP address is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. In the script, it is mentioned that each packet has the IP address of its origin and destination, which helps routers direct the packets to their correct paths.

💡Bob Kahn

Bob Kahn is one of the 'fathers of the Internet,' as mentioned in the script. He, along with his partner, is credited with designing the Internet's protocols and architecture. His contribution is essential to the video's narrative, as it discusses the origins and development of the Internet.

💡Congestion

Congestion in the video refers to the state of being overcrowded or packed full, particularly in the context of data traffic on the Internet. The script explains that if one route is congested, individual packets may take alternative routes, which is part of the Internet's design to maintain smooth data flow.

💡Fault Tolerance

Fault tolerance is the ability of a system to continue operating properly in the event of the failure of some of its components. The script describes the Internet as fault-tolerant, meaning it can keep functioning and sending packets even if parts of the network fail, which is a key aspect of its reliability.

💡Redundancy

Redundancy in the video is the presence of backup systems or components that can take over in case of a failure. It is related to the concept of fault tolerance, as the script explains that having multiple paths for data to travel makes the network more reliable by providing alternative routes when needed.

💡Protocols

Protocols in the video are the set of rules governing the format and transmission of data over the Internet. The script mentions that the Internet's protocols and architecture were designed by the speaker and Bob Kahn, which are essential for the reliable and efficient functioning of the Internet.

Highlights

The Internet's reliability is often taken for granted despite the vast amount of information being transmitted.

The Internet does not operate on direct, dedicated connections but uses a less direct method for data transmission.

In the 1970s, the design of the Internet's protocols and architecture was initiated by Bob Kahn and Vint Cerf.

Data on the Internet travels in packets, which can change paths dynamically during transmission.

Packets of information on the Internet are similar to transporting goods in vehicles, adapting to traffic and road conditions.

Large files like images are broken down into smaller packets for transmission.

Routers on the Internet act as traffic managers, directing packets based on the destination IP address.

Packets may take different routes and arrive out of order, but are reassembled at the destination.

The 'cheapest' path for data is determined by factors like time and non-technical aspects, not cost.

The Internet's fault tolerance allows continuous packet transmission even when some components fail.

TCP (Transmission Control Protocol) ensures reliable data delivery by managing packet sending and receiving.

TCP verifies the delivery of all packets, requesting retransmission of any missing or incomplete packets.

The scalability of TCP and router systems allows the Internet to handle billions of devices without service interruption.

The Internet's growth and scaling can occur without disrupting service due to its principles of fault tolerance and redundancy.

Hundreds of thousands of networks and billions of devices connect and communicate through agreed-upon Internet standards.

Computing devices and routers help packets reach their destinations, where they are reassembled in the correct order.

The Internet facilitates billions of data transmissions daily for various activities like emails, web browsing, video chats, and IoT communications.

Transcripts

- [Voiceover] Seven, six, five, four, three, two, one.

(funky music)

- Hi, my name is Lynn Root. I am the Software Engineer

here at Spotify, and I will be the first to admit that I

often take for granted the reliability of the Internet.

The sheer amount of information zooming around the

Internet is astonishing. But how's it possible for every

piece of data to be delivered to you reliably?

Say you want to play a song from Spotify.

It seems like your computer connects directly to

Spotify's servers, and Spotify sends you a song

on a direct, dedicated line. But actually, that's not

how the Internet works.

If the Internet were made of direct, dedicated connections,

it would be impossible to keep things working as

millions of users join, especially since there is no

guarantee that every wire and computer is

working all the time.

Instead, data travels on the Internet in a much less

direct fashion.

- Many, many years ago, in the early 1970s,

my partner, Bob Kahn, and I began working on

the design of what we now call the Internet.

Bob and I had the responsibility and the opportunity

to design the Internet's protocols and its architecture.

So, we persisted in participating in the Internet's growth

and evolution for all of this time,

up to, and including, the present.

The way information gets transferred from one computer

to another is pretty interesting.

It need not follow a fixed path.

In fact, your path may change in the midst of a

computer-to-computer conversation.

Information on the Internet goes from one computer

to another in what we call a packet of information,

and a packet travels from one place to another on

the Internet a lot like how you might get from one place

to another in a car, depending on traffic congestion or

road conditions, you might choose or be forced to take

a different route to get to the same place each time

you travel.

And just as you can transport all sorts of stuff

inside a car, many kinds of digital information can be

sent with IP packets, but there are some limits.

What if, for example, you need to move a space shuttle

from where it was built to where it will be launched?

A shuttle won't fit in one truck, so it needs to be broken

down into pieces, transported using a fleet of trucks.

They could all take different routes, and might get to

the destination at different times, but once all the pieces

are there, you can reassemble the pieces into the

complete shuttle, and it'll be ready for launch.

On the Internet, the details work similarly.

If you have a very large image that you want to send

to a friend or upload to a website, that image might

be made up of tens of billions of bits of ones and zeroes,

too many to send along in one packet.

Since it's data on a computer, the computer sending

the image can quickly break it into hundreds or even

thousands of smaller parts called packets.

Unlike cars or trucks, these packets don't have drivers,

and they don't choose their route. Each packet has

the internet address of where it came from and where

it's going. Special computers on the Internet,

called routers, act like traffic managers to keep the

packets moving through the networks smoothly.

If one route is congested, individual packets may

travel different routes through the Internet,

and they may arrive at the destination at slightly

different times, or even out of order.

- So, let's talk about how this works.

As part of the Internet Protocol, every router

keeps track of multiple paths for sending packets,

and it chooses the cheapest available path for

each piece of data, based on destination

IP address for the packet.

"Cheapest," in this case, doesn't mean cost,

but time and non-technical factors such as politics

and relationships between companies.

Often the best route for data to travel isn't necessarily

the most direct. Having options for paths makes the

network fault tolerant, which means the network can

keep sending packets, even if something goes horribly,

horribly wrong. This is the basis for a key principle of

the Internet, reliability.

Now, what if you want to request some data

and not everything is delivered?

Say you want to listen to a song.

How can you bee 100% sure all the data will be

delivered so the song plays perfectly?

Introducing your new best friend, TCP,

Transmission Control Protocol.

TCP manages the sending and receiving of all your data

as packets. Think of it like a guaranteed mail service.

When you request a song on your device,

Spotify sends the song broken up into many packets.

When your packets arrive, TCP does a full inventory

and sends back acknowledgements of each packet received.

If all packets are there, TCP signs for your delivery,

and you're done.

(upbeat music)

If TCP finds some packets are missing,

it won't sign. Otherwise, your song wouldn't sound as good,

or portions of the song could be missing.

For each missing or incomplete packet,

Spotify will resend them. Once TCP verifies the delivery

of many packets for that one song request,

your song will start to play.

(upbeat music)

What's great about the TCP and router systems is

they're scalable. They can work with eight devices or

8,000,000,000 devices. In fact, because of these principles

of fault tolerance and redundancy, the more routers we add,

the more reliable the Internet becomes.

What's also great is we can grow and scale the

Internet without interrupting service for anybody using it.

- The Internet is made of hundreds of thousands of

networks and billions of computers and devices

connected physically. These different systems that make up

the Internet connect to each other, communicate with

each other, and work together because of agreed upon

standards for how data is sent around on the Internet.

Computing devices, or routers along the Internet,

help all the packets make their way to the destination

where they're reassembled, if necessary, in order.

This happens billions of times a day, whether you and

others are sending an email, visiting a webpage,

doing a video chat, using a mobile app, or when sensors

or devices on the Internet talk to each other.