chapter_1_-_internet_networks_and_tcp-ip:1-1_data_transmission_on_the_internet

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chapter_1_-_internet_networks_and_tcp-ip:1-1_data_transmission_on_the_internet [2013/01/18 12:27]
cellbiol
chapter_1_-_internet_networks_and_tcp-ip:1-1_data_transmission_on_the_internet [2013/02/15 19:41] (current)
cellbiol
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 If we picture a file as a train, the packets would be the individual wagons. Big train: several wagons, small train: few, maybe just one wagon. If we picture a file as a train, the packets would be the individual wagons. Big train: several wagons, small train: few, maybe just one wagon.
  
-Each packet is like an envelope sent by normal mail, with the actual data, part of the original file, inside. Outside, we have information that will allow TCP/IP to process the packet by extracting and merging it's inside data with the data from the other packets from the same file, in the correct order, in order to rebuild the file from it's packets. A scheme of a TCP/IP packet is shown in Figure 1-2)+Each packet is like an envelope sent by normal mail, with the actual data, part of the original file, inside. Outside, we have information that will allow TCP/IP to process the packet by extracting and merging it's inside data with the data from the other packets from the same file, in the correct order, in order to rebuild the file from it's packets. A scheme of a TCP/IP packet is shown in Figure 1-1-1)
  
-== Figure 1-2: Representation of a TCP/IP packet ==+== Figure 1-1-1: Representation of a TCP/IP packet ==
 Image Source: [[http://​en.wikipedia.org/​wiki/​Transmission_Control_Protocol|Wikipedia]] Image Source: [[http://​en.wikipedia.org/​wiki/​Transmission_Control_Protocol|Wikipedia]]
  
-{{ :​chapter_1_-_internet_networks_and_tcp-ip:​tcp_ip_header_ipv4.png?300 |}}+{{ :​chapter_1_-_internet_networks_and_tcp-ip:​tcp_ip_header_ipv4.png |}}
  
 Each packet, or envelope if we follow on the previous example, contains the following information:​ the source of the data (sender), the destination of the data (receiver), information on the source file and on the position of the packet in this file (say packet 3 of 123 from file X). With this information,​ once all the packets for a file have reached the intended destination,​ they can be used by TCP/IP to rebuild the original file. Each packet, or envelope if we follow on the previous example, contains the following information:​ the source of the data (sender), the destination of the data (receiver), information on the source file and on the position of the packet in this file (say packet 3 of 123 from file X). With this information,​ once all the packets for a file have reached the intended destination,​ they can be used by TCP/IP to rebuild the original file.
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 You may notice, in the scheme above, that the fact that packets travel individually is underlined. As we mentioned, communication paths (most often constituted by physical wires) between computer A and computer F (Figure 1-1) on the Internet are often redundant. Also, these paths are often not direct (unless A and F are in the same room or the same building), but rather contain a number or "​relays"​. That is in order for data to travel from A to F, they might be relayed through B, C, and D (Figure 1-1). Physically, on the hardware level, there relays are constituted by [[http://​en.wikipedia.org/​wiki/​Router_%28computing%29|Routers]]. As the name implies, routers allow packets to find the best route between two computers. Data are generally relayed through several such routers before they reach their final destination. You may notice, in the scheme above, that the fact that packets travel individually is underlined. As we mentioned, communication paths (most often constituted by physical wires) between computer A and computer F (Figure 1-1) on the Internet are often redundant. Also, these paths are often not direct (unless A and F are in the same room or the same building), but rather contain a number or "​relays"​. That is in order for data to travel from A to F, they might be relayed through B, C, and D (Figure 1-1). Physically, on the hardware level, there relays are constituted by [[http://​en.wikipedia.org/​wiki/​Router_%28computing%29|Routers]]. As the name implies, routers allow packets to find the best route between two computers. Data are generally relayed through several such routers before they reach their final destination.
- 
-<​html>​ 
-<div style="​margin-left:​auto;​margin-right:​auto;​margin-bottom:​20px;​text-align:​center">​ 
-        <script type="​text/​javascript"><​!-- 
-        google_ad_client = "​ca-pub-0159360445983090";​ 
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 The crucial thing to understand here, is that at any given time (we re talking about milliseconds),​ the best route between 2 computers might change. Routers are able to determine, at the moment of sending a particular packet, the best route at this time. When sending the next packet, the best route might have changed. Therefore, each packet from the same file could take a different route in order to reach the intended destination. The crucial thing to understand here, is that at any given time (we re talking about milliseconds),​ the best route between 2 computers might change. Routers are able to determine, at the moment of sending a particular packet, the best route at this time. When sending the next packet, the best route might have changed. Therefore, each packet from the same file could take a different route in order to reach the intended destination.
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 ==== Chapter Sections ==== ==== Chapter Sections ====
 +<box 100% left round blue | **Chapter 1**>
 +<​html>&​nbsp;</​html>​
   * [[chapter_1_-_internet_networks_and_tcp-ip:​start|Introduction]]   * [[chapter_1_-_internet_networks_and_tcp-ip:​start|Introduction]]
-  * **1-1**: Data Transmission on the Internet+  * **1-1**: ​[[chapter_1_-_internet_networks_and_tcp-ip:​1-1_data_transmission_on_the_internet|Data Transmission on the Internet]]
   * **1-2**: [[chapter_1_-_internet_networks_and_tcp-ip:​1-2_the_tcp-ip_family_of_internet_protocols|The TCP/IP Family of Internet Protocols]]   * **1-2**: [[chapter_1_-_internet_networks_and_tcp-ip:​1-2_the_tcp-ip_family_of_internet_protocols|The TCP/IP Family of Internet Protocols]]
   * **1-3**: [[chapter_1_-_internet_networks_and_tcp-ip:​1-3_networking_basics|Networking Basics]]   * **1-3**: [[chapter_1_-_internet_networks_and_tcp-ip:​1-3_networking_basics|Networking Basics]]
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 [[:​start|Back to main index]] [[:​start|Back to main index]]
 +</​box>​
chapter_1_-_internet_networks_and_tcp-ip/1-1_data_transmission_on_the_internet.1358530038.txt.gz · Last modified: 2013/01/18 12:27 by cellbiol