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Thread: Cisco

  1. #1
    SG Enthusiast Merc's Avatar
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    Cisco

    Im taking this class and damn I can say it kinda is getting hard. Like besides nowing the layers of both the OSI and the TCP/IP i have to know what each layer does and which type of encapsilation each uses. Well im studying my ass off so I can make good grades in that class.
    We have seen their kind before. They're the heirs of all the murderous ideologies of the 20th century. By sacrificing human life to serve their radical visions, by abandoning every value except the will to power, they follow in the path of fascism, Nazism and totalitarianism. And they will follow that path all the way to where it ends in history's unmarked grave of discarded lies.

  2. #2
    Banned gmcd33's Avatar
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    Thats the easy part. Did you get into subnetting yet?

    You will look back and consider the OSI and the DOD (TCP/IP) models cake.

  3. #3
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    No I just gotta learn what each layer does its a lotta learning right there.
    We have seen their kind before. They're the heirs of all the murderous ideologies of the 20th century. By sacrificing human life to serve their radical visions, by abandoning every value except the will to power, they follow in the path of fascism, Nazism and totalitarianism. And they will follow that path all the way to where it ends in history's unmarked grave of discarded lies.

  4. #4
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    Here is their section on TCP/IP

    The U.S. Department of Defense (DoD) created the TCP/IP reference model because it wanted a network that could survive any conditions, even a nuclear war. To illustrate further, imagine a world at war, criss-crossed by different kinds of connections - wires, microwaves, optical fibers, and satellite links. Then imagine that you need information/data (in the form of packets) to flow, regardless of the condition of any particular node or network on the internetwork (which in this case may have been destroyed by the war). The DoD wants its packets to get through every time, under any conditions, from any one point to any other point. It was this very difficult design problem that brought about the creation of the TCP/IP model, and which has since become the standard on which the Internet has grown.
    As you read about the TCP/IP model layers, keep in mind the original intent of the Internet; it will help explain why certain things are as they are. The TCP/IP model has four layers: the application layer, the transport layer, the Internet layer, and the network access layer. It is important to note that some of the layers in the TCP/IP model have the same name as layers in the OSI model. Do not confuse the layers of the two models, because the application layer has different functions in each model.

    Application Layer
    The designers of TCP/IP felt that the higher level protocols should include the session and presentation layer details. They simply created an application layer that handles high-level protocols, issues of representation, encoding, and dialog control. The TCP/IP combines all application-related issues into one layer, and assures this data is properly packaged for the next layer.

    Transport Layer
    The transport layer deals with the quality-of-service issues of reliability, flow control, and error correction. One of its protocols, the transmission control protocol (TCP), provides excellent and flexible ways to create reliable, well-flowing, low-error network communications. TCP is a connection-oriented protocol. It dialogues between source and destination while packaging application layer information into units called segments. Connection-oriented does not mean that a circuit exists between the communicating computers (that would be circuit switching). It does mean that Layer 4 segments travel back and forth between two hosts to acknowledge the connection exists logically for some period. This is known as packet switching.

    Internet Layer
    The purpose of the Internet layer is to send source packets from any network on the internetwork and have them arrive at the destination independent of the path and networks they took to get there. The specific protocol that governs this layer is called the Internet protocol (IP). Best path determination and packet switching occur at this layer. Think of it in terms of the postal system. When you mail a letter, you do not know how it gets there (there are various possible routes), but you do care that it arrives.

    Network Access Layer
    The name of this layer is very broad and somewhat confusing. It is also called the host-to-network layer. It is the layer that is concerned with all of the issues that an IP packet requires to actually make a physical link, and then to make another physical link. It includes the LAN and WAN technology details, and all the details in the OSI physical and data link layers.
    We have seen their kind before. They're the heirs of all the murderous ideologies of the 20th century. By sacrificing human life to serve their radical visions, by abandoning every value except the will to power, they follow in the path of fascism, Nazism and totalitarianism. And they will follow that path all the way to where it ends in history's unmarked grave of discarded lies.

  5. #5
    Banned gmcd33's Avatar
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    I love the OSI and DOD. If you interview for a networking position, employers love asking you to explain the OSI and all its layers' functions.

    Besides you really need to know all that stuff. Its a great foundation for whats to come.

  6. #6
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    Basically Here is a broad generalization of what i have.

    App Is where it provides connectivity to the users applications and is closest to the user.

    Presentation makes sure that the data being sent is able to be read by the users application layer.

    Session establishes, manages, and terminates sessions between two communicating hosts sync dialogue and manages data exchange to the presentation layer regulation, the session layer offers provisions for efficient data transfer, class of service

    Network The transport layer attempts to provide a data transport service that shields the upper layers from transport implementation details. Specifically, issues such as how reliable transport between two hosts is accomplished is the concern of the transport layer. In providing communication service, the transport layer establishes, maintains, and properly terminates virtual circuits. In providing reliable service, transport error detection-and-recovery and information flow control are used.

    Network Layer is connectivity and Path Selection

    Data Link concerned with IP provides reliable transit of data across a physical link addressing, network topology, network access, error notification, ordered delivery of frames, and flow control.

    Physical layer the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between end systems.
    We have seen their kind before. They're the heirs of all the murderous ideologies of the 20th century. By sacrificing human life to serve their radical visions, by abandoning every value except the will to power, they follow in the path of fascism, Nazism and totalitarianism. And they will follow that path all the way to where it ends in history's unmarked grave of discarded lies.

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