Month: January 2020
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2.3 The Transport Layer (TCP)
The Internetwork layer is both simple and complex. It looks at a packet’s destination address and finds a path across multiple network hops to deliver the packet to the destination computer. But sometimes these packets get lost or badly delayed. Other times the packets arrive at their destination out of order because a later packet…
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2.2 The Internetwork Layer (IP)
Once your packet destined for the Internet makes it across the first link, it will be in a router. Your packet has a source address and destination address and the router needs to look at the destination address to figure out how to best move your packet towards its destination. With each router handling packets…
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2.1 The Link Layer
The Link layer is responsible for connecting your computer to its local network and moving the data across a single hop. The most common Link layer technology today is wireless networking.When you are using a wireless device, the device is only sending data a limited distance. A smartphone communicates with a tower that is a…
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2.7 Questions-Chapter 2
You can take this quiz online at http://www.net-intro.com/quiz/1) Why do engineers use a “model” to organize their approach to solving a large and complex problem?a) Because it allows them to build something small and test it in a wind tunnelb) Because talking about a model delays the actual start of the hard workc) Because they…
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2.6 Glossary-Chapter 2
client: In a networked application, the client application is the one that requests services or initiates connections.fiber optic: A data transmission technology that encodes data using light and sends the light down a very long strand of thin glass or plastic. Fiber optic connections are fast and can cover very long distances.offset: The relative position…
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2 Network Architecture
To engineer and build a system as complex as the Internet, engineers try to break a single challenging problem into a set of smaller problems that can be solved independently and then put back together to solve the original large problem. The engineers who built the first internets broke the overall problem into four basic…
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1.8 Questions-chapter 1
You can take this quiz online at http://www.net-intro.com/quiz/ What did early telephone operators do? a) Maintained cell phone towers b) Connected pairs of wires to allow people to talk c) Installed copper wire between cities d) Sorted packets as they went to the correct destination What is a leased line? a) A boundary between leased…
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1.7 Glossary-Chapter 1
address: A number that is assigned to a computer so that messages can be routed to the computer.hop: A single physical network connection. A packet on the Internet will typically make several “hops” to get from its source computer to its destination.LAN: Local Area Network. A network covering an area that is limited by the…
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1.6 Putting It All Together
So when we combine all this together we can understand the basic operation of today’s Internet. We have specialized computers called “routers” that know how to route packets along a path from a source to a destination. Each packet will pass through multiple routers during its journey from the source computer to the destination computer.…
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1.5 Addressing and Packets
In the early store-and-forward networks it was important to know the source and destination computers for every message. Each computer was given a unique name or number that was called the “address” of the computer. To send a message to another computer, you needed to add the source and destination address to the message before…
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1.4 Packets and Routers
The most important innovation that allowed messages to move more quickly across a multi-hop network was to break each message into small fragments and send each fragment individually. In networking terms, these pieces of messages are called “packets”. The idea of breaking a message into packets was pioneered in the 1960s, but it was not…
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1.3 Early Wide Area Store-and-Forward Networks
In the 1970s and 1980s, people working at universities around the world wanted to send each other data and messages using these computer-to-computer connections. Since the cost for each connection was so high and increased with distance, computers generally only had connections to other nearby computers. But if the computer that you were connected to…
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1.2 Computers Communicate Differently
When humans talk on the phone, they make a call, talk for a while, and then hang up. Statistically, most of the time, humans are not talking on the phone. At least they weren’t before everyone had smartphones. But computers, including the applications on your smartphone, communicate differently than humans do. Sometimes computers send short…
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1.1 Communicating at a Distance
Imagine a group of five people in a room sitting in a circle. As long as they are courteous and don’t have more than one conversation at the same time, it’s quite natural for any person to talk to any other person in the room. They just need to be able to hear each other…
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Chapter 1 Introduction
Using the Internet seems pretty easy. We go to a web address and up comes a page. Or we go to our favorite social site and see pictures of our friends, families, and pets. But it takes a lot of complex software and hardware to make the Internet seem so simple. The design of the…