From a security perspective encryption is important because it provides the

From a security perspective encryption is important

This preview shows page 7 - 9 out of 27 pages.

From a security perspective, encryption is important because it provides the ability to keep information confidential. Connection Versus Connectionless At the transport layer are the two protocols known as TCP and UDP; these protocols are known as connection and connectionless respectively. Connection-oriented protocols operate by acknowledging or confirming every connection request or transmission, much like getting a return receipt for a letter. Connectionless protocols are those that do not require an acknowledgement and in fact do not ask for nor get one. The difference between these two is the overhead that is involved. Due to connection-oriented protocol’s need for acknowledgements, the overhead is more and the performance is less, while connectionless is faster due to its lack of this requirement. NOTE Examples of these formats include American Standard Code for Information Interchange (ASCII) and Extended Binary Coded Decimal Interchange Code (EBCDIC).
Image of page 7
30 PART 1 | Hacker Techniques and Tools Layer 7: Application Layer Capping off the OSI reference model is the application layer (Layer 7). The application layer hosts several application services that are used by applications and other services running on the system. For example, Web browsers that would be classified as a user-level application run on a system and access the network by “plugging” into the services at this layer to use the network. This layer includes network monitoring, management, file sharing, RPC, and other services used by applications. The application layer is one that most users are familiar with because it is the home of e-mail programs, file transfer protocol (FTP), Telnet, Web browsers, office productivity suites, and many other applications. It is also the home of many malicious programs such as viruses, worms, Trojan horse programs, and other malevolent applications. The Role of Encapsulation In the OSI framework, the concept of encapsulation is the process of “packaging” infor- mation prior to transmitting it from one location to another. When transmitted across the network, it moves down from the application layer to the physical layer and then through the physical medium. As the data moves from the application layer down, the information is packaged and manipulated along the way until it becomes a collection of bits that race down the wire to the receiving station, where the process is reversed as the data moves back up the model. Data Application Transport Internet Link UDP Data IP Data UDP Header Frame Header Frame Footer IP Header Frame Data FIGURE 2-3 Encapsulation. Be sure that when thinking of the name “application layer,” you take care not to think of software applications. Software applications are those items that a user of a system interacts with directly, such as e-mail applications and Web browsers. The application layer is the point at which software applications access network services as needed. Think of the software applications as a microwave oven in your home and the application layer as the electrical outlet that the microwave plugs into to get power.
Image of page 8
Image of page 9

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture