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  1. #1

    Network Security Misconceptions: Chapter 3: Yes, you need to know TCP/IP

    I'm happy to see the response that our Networking Security Misconceptions series is getting. If you would like to contribute to the series, e-mail me at jparker@o-negative.net, and drop in and chat at irc.antionline.com, #Antionline.

    The next thing I would like to bring to your attention would be the lack of understand in the TCP/IP protocol suite itself. We, as computer users, should know what exactly is going on underneath all the glitz and glamour of the Internet. The backbone of this incredible network lies in the 7 layers of this protocol suite.
    Yes, I keep saying "suite" because TCP/IP is not one, not two, but comprised of MANY protocols all working together to give use services. Protocls like HTTP, SMTP, UUCP, FTP, IRC.. yes, even IRC has it's own protocol that trickles down through the layers of this old protocol suite.
    To begin, I guess we should start at the TCP/IP Model. The TCP/IP model lays out the flow of information in a TCP/IP based network. From the lowest point, the "network layer", to the highest point, the "application layer". Data that is sent across the network passes from layer to layer before actually being sent out from the machines. Each layer communicates with the the layers above and below it so that the information can be checked and packaged. When two computers communicate on a network, the layer (the software that controls all functions dealing with TCP/IP) on one machine assumes it's communicating with the layer on the other machine. So, what kind of networking hardware, OS or machine type that you're using doesn't matter, as long as they are using a TCP/IP compatible network stack. That is the beauty of being able to network the machines that have different OSs, and architectures.
    The TCP/IP model has 4 layers, from the top we have, Application, Transport, Internet, Network Access layers. Within these layers all TCP/IP information is processed.

    Starting at the Network Access, this transmits bits from one computer to another on a hardware level. This also encompasses the cabling, and network card and define how the information is sent over the cable. It also packages the information (the raw bits) from the Physical layer into "frames". Frames are structured packets that have a static setup to how information is collected into the packet. This layer is also responsible for sendinf the frames from one machine to another without an error. After sending a frame, it waits for an acknowledgment from the destination machine. This is comparable to the Physical and Data layers int he OSI model of layered network communication.

    The Internet Layer is where the addresses are attached to the packet. This would include the source, and destination IPs, and it also determines the route the packets will take to get to ther destination machine.

    The Transport Layer is where the error detection and header recorvery is done. It also rebundles the packets into smaller, easier to transport packets then rebuilds it upon receipt at the destination.

    Last but not least is the Application Layer, king of the hill, top of the heap. This layer is where we run all of our software that accesses network services. This layer gives us goodies like e-mail, and file transfers, web pages, and chat.

    So, what have we learned from all of this quick and dirty post? Nothing? ::Shrug:: I hope not. I hope that you take away a little bit of understanding as to what is going on when you're working with TCP/IP based system and you can incorporate this into your tasks and projects to make you better informed, and more careful, about what is going on beneath the surface.


    If you have any questions, or want to contribute to the Networking Security Misconception Series, please stop in on irc.antionline.com #Antionline, or e-mail me at: jparker@o-negative.net
    Jason Parker - http://www.o-negative.net
    o-Negative: Information Network

  2. #2
    Senior Member
    Join Date
    May 2002
    Thank u for that its was easy to read and understand

  3. #3
    Senior Member
    Join Date
    May 2002
    i got confused between the ISO model and the netwowrking where as networking has 7 layers which are but ya im clear now lol

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