Networks: Packets, Topology, and Links PDF

Networks: Packets, Topology and Links https://njctl.org/video/?v=SaA6jaYoTo8 Return to Table of Contents  Packets of Data When messages, or data, are sent from one...

Networks: Packets, Topology and Links https://njctl.org/video/?v=SaA6jaYoTo8 Return to Table of Contents  Packets of Data When messages, or data, are sent from one computer to another via the Internet, they are first broken down into fixed­sized packets of data and metadata (e.g., P1, P2 & P3). Message Packets P1P2P3 P1 P2 P3 P1 P2 P3 1. Break the message/ data into packets  Packets of Data Next, each packet is sent to its destination (e.g., another computer) independently via the Internet. The independence could cause them to take different paths. 2. Packets travel to destination P1 P2 P3 1. Break the message/ data into packets  Packets of Data The packets are then re­assembled at the destination to form the original message, or data. These packets may arrive at the destination in the order they were sent, out of order, or not at all. Computer communication networks that send data in the form of small packets are called packet switched networks (PSNs). 2. Packets travel to destination P1 P2 P3 3. Re­assemble 1. Break the message/ packets data into packets  Why Send Packets of Data? In the 1960s, the driving motivation was a desire for a network that could withstand a nuclear attack. To do this, the network had to be decentralized and have multiple paths between two computers. Dividing data into small packets that routed independently prevented the entire data set from being intercepted before reaching its destination. Each router along the path would forward the packets to another router until it reached the final destination.  Network Scope & Scale Depending on the size of the network, different names are given to define properties or features of the network. The two most common types of networks are: 1) A Local Area Network (LAN) connects computers within a school or home. All the computers on this network are within a very small geographic location. 2) A Wide Area Network (WAN) connects computers across a broad geographic region, such as a telephone network.  Network Topology How networks are organized can have a significant effect on output and reliability. Depending on the layout or topology of the network, one failure can cause an entire network to fail.  Network Topology Token Ring is probably the least familiar type of network connection because it has been almost completely replaced by Ethernet Protocol, due to lack of efficiency and high cost. It is a wired LAN that connects workstations in the form of a "ring" as shown above. In this protocol, a signal called a "Token" is sent to a computer, which authorizes it to send data. Only computers with a Token can send data. The number of regulated tokens prevents the collision of computers while they are trying to send data in the network.  Network Topology Token Ring Protocol is not efficient because each station has to wait to receive or send data, which slows down communication. Ethernet Protocol is a much more efficient wired LAN today. It has been refined to be able to send data at a rate of a gigabit per second (a seemingly instant speed). The image above shows how computers are linked through one common cable, called an Ethernet Cable, which allows any computer connected to communicate with another. This is also known as a bus topology.  Network Topology Ethernet Cables are a specific type of cable used to connect workstations. They prevent data from colliding, so that it can be sent and received at any time, by any workstation. It is backward compatible, meaning it can connect old and new technologies, as well as work hand in hand with Internet Protocol (IP).  Network Topology WiFi Protocol is now considered the most common type of LAN, also referred to as WLAN. It uses radio waves to connect computer workstations and devices (e.g., smart phones, tablets, etc.), instead of cables/wires. This is known as a star topology. Interesting Fact: WiFi stands for Wireless Fidelity, meaning data stays true through a wireless transfer, where it must be distorted into radio waves. Then it is essentially "recombined" into its original form.  Network Topology WiFi Protocol has also become the most commonly used WAN. It's so common, that a popular misconception is that WAN stands for Wireless Area Network. But that is FALSE! Just as the "L" in LAN means "local, the "W" in WAN has a geographic meaning of "wide", NOT "wireless". These acronyms represent the physical distance between computers/devices on a network, not the method by which they are connected. In both types of networks, the connection itself could be Ethernet, WiFi, or even a combination of both.  Network Topology Today, we see a combination of Ethernet and WiFi connected LANs depending on the needs of the individual business, educational institution, or person setting it up. Some WANs connect smaller LANs, but also can have Ethernet and WiFi components at various points of the connections. We will learn more about this in the next topic.  Bus vs. Star Topology Comparing the Bus vs. Star network setup, we can see the pros/cons of each setup. single cable connects all utilizes a central hub peripheral devices if one computer in the if one computer in the network network is damaged, the stops working the entire network network continues to function stops working more difficult to create simple to create uses more cable length uses less cable length more expensive more economical works well with large works well with a few computers numbers of computers