Category: Education
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3.4 Summary-Chapter 3
So now we have looked at the “lowest” layer in our four-layer architecture. And we have only taken a simple look at how the Link layer works. There are many other details that must be designed into a link layer like connection distance, voltage, frequency, speed, and many others. A key benefit of the layered…
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3.3 Coordination in Other Link Layers
Sometimes when a link layer has many transmitting stations and needs to operate at near 100% efficiency for long periods of time, the design takes a different approach. In this approach, there is a “token” that indicates when each station is given the opportunity to transmit data. Stations cannot start a transmission unless they have…
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3.2 Courtesy and Coordination
Because many computers are sharing the same radio frequencies, it’s important to coordinate how they send data. When there’s a crowd of people in a room, they can’t all talk at the same time or everything will be garbled. The same thing happens when multiple WiFi radios transmit at the same time on the same…
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3.1 Sharing the Air
When your laptop or phone is using WiFi to connect to the Internet, it is sending and receiving data with a small, low-powered radio. The radio in your computer can only send data about 300 meters, so your computer sends your packets to the router in your home, which forwards the packets using a link…
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3 Link Layer
The lowest layer of our Internet Architecture is the Link layer. We call it the “lowest layer” because it is closest to the physical network media. Often the Link layer transmits data using a wire, a fiber optic cable, or a radio signal. A key element of the Link layer is that usually data can…
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2.5 Stacking the Layers
We usually show the four different layers (Link, Internetwork, Transport, and Application) stacked on top of each other with the Application layer at the top and the Link layer at the bottom. The reason we show them this way is because each layer makes use of the layers above and below it to achieve networked…
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2.4 The Application Layer
The Link, Internetwork, and Transport layers work together to quickly and reliably move data between two computers across a shared network of networks. With this capability to move data reliably, the next question is what networked applications will be built to make use of these network connections. When the first widely used Internet came into…
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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…