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<a class="dropdown-item" tabindex="-1" href="InternetOverview.html#"><b>Chapter 1</b></a>
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<a class="dropdown-item" href="IntroConcSysOverview.html"> 1.1. Introduction to Concurrent Systems</a>
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<a class="dropdown-item" href="SysAndModels.html"> 1.2. Systems and Models</a>
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<a class="dropdown-item" href="Themes.html"> 1.3. Themes and Guiding Principles</a>
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<a class="dropdown-item" href="Architectures.html"> 1.4. System Architectures</a>
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<a class="dropdown-item" href="SequenceModels.html"> 1.6. Sequence Models in UML</a>
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<a class="dropdown-item" href="StateModelImplementation.html"> 1.7. Extended Example: State Model Implementation</a>
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<a class="dropdown-item disabled"><b>Chapter 2</b></a>
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<a class="dropdown-item" href="ProcessesOverview.html"> 2.1. Processes and OS Basics</a>
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<a class="dropdown-item" href="Multiprogramming.html"> 2.2. Processes and Multiprogramming</a>
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<a class="dropdown-item" href="UnixFile.html"> 2.6. The UNIX File Abstraction</a>
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<a class="dropdown-item" href="EventsSignals.html"> 2.7. Events and Signals</a>
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<a class="dropdown-item" href="Extended2Processes.html"> 2.8. Extended Example: Listing Files with Processes</a>
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<a class="dropdown-item disabled"><b>Chapter 3</b></a>
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<a class="dropdown-item" href="IPCOverview.html"> 3.1. Concurrency with IPC</a>
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<a class="dropdown-item" href="IPCModels.html"> 3.2. IPC Models</a>
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<a class="dropdown-item" href="POSIXvSysV.html"> 3.5. POSIX vs. System V IPC</a>
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<a class="dropdown-item" href="MQueues.html"> 3.6. Message Passing With Message Queues</a>
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<a class="dropdown-item" href="IPCSems.html"> 3.8. Semaphores</a>
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<a class="dropdown-item" href="Extended3Bash.html"> 3.9. Extended Example: Bash-lite: A Simple Command-line Shell</a>
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<a class="dropdown-item disabled"><b>Chapter 4</b></a>
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<a class="dropdown-item" href="SocketsOverview.html"> 4.1. Networked Concurrency</a>
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<a class="dropdown-item" href="FiveLayer.html"> 4.2. The TCP/IP Internet Model</a>
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<a class="dropdown-item" href="NetApps.html"> 4.3. Network Applications and Protocols</a>
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<a class="dropdown-item disabled"><b>Chapter 5</b></a>
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<a class="dropdown-item" href="InternetOverview.html"> 5.1. The Internet and Connectivity</a>
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<a class="dropdown-item" href="AppLayer.html"> 5.2. Application Layer: Overlay Networks</a>
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<a class="dropdown-item" href="TransLayer.html"> 5.3. Transport Layer</a>
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<a class="dropdown-item" href="NetLayer.html"> 5.5. Network Layer: IP</a>
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<a class="dropdown-item" href="ThreadsOverview.html"> 6.1. Concurrency with Multithreading</a>
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<a class="dropdown-item" href="POSIXThreads.html"> 6.4. POSIX Thread Library</a>
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<a class="dropdown-item" href="ThreadArgs.html"> 6.5. Thread Arguments and Return Values</a>
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<a class="dropdown-item" href="ImplicitThreads.html"> 6.6. Implicit Threading and Language-based Threads</a>
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<a class="dropdown-item" href="Extended6Input.html"> 6.7. Extended Example: Keyboard Input Listener</a>
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<a class="dropdown-item" href="SynchOverview.html"> 7.1. Synchronization Primitives</a>
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<a class="dropdown-item" href="CritSect.html"> 7.2. Critical Sections and Peterson's Solution</a>
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<a class="dropdown-item" href="Locks.html"> 7.3. Locks</a>
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<a class="dropdown-item disabled"><b>Chapter 8</b></a>
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<a class="dropdown-item" href="SynchProblemsOverview.html"> 8.1. Synchronization Patterns and Problems</a>
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<a class="dropdown-item" href="SynchDesign.html"> 8.2. Basic Synchronization Design Patterns</a>
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<a class="dropdown-item" href="ProdCons.html"> 8.3. Producer-Consumer Problem</a>
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<a class="dropdown-item" href="ReadWrite.html"> 8.4. Readers-Writers Problem</a>
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<a class="dropdown-item" href="DiningPhil.html"> 8.5. Dining Philosophers Problem and Deadlock</a>
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<a class="dropdown-item" href="CigSmokers.html"> 8.6. Cigarette Smokers Problem and the Limits of Semaphores and Locks</a>
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<a class="dropdown-item" href="Extended8ModExp.html"> 8.7. Extended Example: Parallel Modular Exponentiation</a>
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<a class="dropdown-item disabled"><b>Chapter 9</b></a>
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<a class="dropdown-item" href="ParallelDistributedOverview.html"> 9.1. Parallel and Distributed Systems</a>
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<a class="dropdown-item" href="ParVConc.html"> 9.2. Parallelism vs. Concurrency</a>
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<a class="dropdown-item" href="ParallelDesign.html"> 9.3. Parallel Design Patterns</a>
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<a class="dropdown-item" href="Scaling.html"> 9.4. Limits of Parallelism and Scaling</a>
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<a class="dropdown-item" href="DistTiming.html"> 9.5. Timing in Distributed Environments</a>
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<a class="dropdown-item" href="DistDataStorage.html"> 9.6. Reliable Data Storage and Location</a>
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<a class="dropdown-item" href="DistConsensus.html"> 9.7. Consensus in Distributed Systems</a>
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<a class="dropdown-item" href="Extended9Blockchain.html"> 9.8. Extended Example: Blockchain Proof-of-Work</a>
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<a class="dropdown-item disabled"><b>Appendix A</b></a>
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<a class="dropdown-item" href="CLangOverview.html"> A.1. C Language Reintroduction</a>
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<a class="dropdown-item" href="Debugging.html"> A.2. Documentation and Debugging</a>
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<a class="dropdown-item" href="BasicTypes.html"> A.3. Basic Types and Pointers</a>
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<a class="dropdown-item" href="Arrays.html"> A.4. Arrays, Structs, Enums, and Type Definitions</a>
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<a class="dropdown-item" href="Functions.html"> A.5. Functions and Scope</a>
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<a class="dropdown-item" href="Pointers.html"> A.6. Pointers and Dynamic Allocation</a>
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<a class="dropdown-item" href="Strings.html"> A.7. Strings</a>
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<a class="dropdown-item" href="FunctionPointers.html"> A.8. Function Pointers</a>
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<a class="dropdown-item" href="Files.html"> A.9. Files</a>
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<script>ODSA.SETTINGS.DISP_MOD_COMP = true;ODSA.SETTINGS.MODULE_NAME = "InternetOverview";ODSA.SETTINGS.MODULE_LONG_NAME = "The Internet and Connectivity";ODSA.SETTINGS.MODULE_CHAPTER = "The Internet and Connectivity"; ODSA.SETTINGS.BUILD_DATE = "2021-06-01 15:31:50"; ODSA.SETTINGS.BUILD_CMAP = false;JSAV_OPTIONS['lang']='en';JSAV_EXERCISE_OPTIONS['code']='java';</script><div class="section" id="the-internet-and-connectivity">
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<h1>5.1. The Internet and Connectivity<a class="headerlink" href="InternetOverview.html#the-internet-and-connectivity" title="Permalink to this headline">¶</a></h1>
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<div class="figure mb-2 align-center" style="width: 100%">
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<a class="reference internal image-reference" href="_images/CSF-Timeline.5.png"><img class="p-3 mb-2 align-center border border-dark rounded-lg" alt="Timeline of major CSF topics with Sockets and Networking highlighted" src="_images/CSF-Timeline.5.png" style="width: 90%;" /></a>
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</div>
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<blockquote class="blockquote text-center">
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<p>“The stuff I design, if I’m successful, nobody will ever notice.
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Things will just work, and be self-managing.”
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<footer class="blockquote-footer">Radia Perlman</footer>
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</blockquote><p>Early computer networks, such as ARPANET, were designed for government and military applications. As
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an increasing number of researchers worked on these technologies, there was a growing push to
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standardize the communication protocols and open access to academic and commercial interests. Vint
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Cerf introduced the term Internet in RFC 675 (1974) as part of the first specification of TCP, and
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the name stuck. The TCP/IP protocol suite was later standardized in 1982, with the Internet emerging
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as the public successor of ARPANET.</p>
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<div class="topic border border-dark rounded-lg bg-light px-2 mb-3">
|
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<div class="figure align-left" style="width: 5%">
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<a class="reference internal image-reference" href="_images/CSF-Images-Objectives.png"><img alt="Decorative chapter objectives image" src="_images/CSF-Images-Objectives.png" style="width: 100%;" /></a>
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</div>
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<p class="topic-title first pt-2 mb-1">Chapter Objectives</p><hr class="mt-1" />
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<p>In this chapter, we will address the following instructional objectives:</p>
|
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<ul class="simple">
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<li>We will describe the principles of application-layer overlay networks.</li>
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<li>We will compare and contrast the functioning of the UDP and TCP transport-layer protocols.</li>
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<li>We will explore how cryptography can be used to provide secure network communication.</li>
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<li>We will summarize how the network and link layers deliver messages through the Internet.</li>
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<li>We will consider how wireless technologies different from traditional wired networks.</li>
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||
</ul>
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||
</div>
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<p>The previous chapter introduce the socket API as a mechanism that appears to behave like other forms
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of IPC. Using the socket API, the application can use traditional <code class="docutils literal notranslate"><span class="pre">read()</span></code> and <code class="docutils literal notranslate"><span class="pre">write()</span></code>
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functions or the equivalent <code class="docutils literal notranslate"><span class="pre">sendto()</span></code> and <code class="docutils literal notranslate"><span class="pre">recvfrom()</span></code> to exchange data with other processes.
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From this perspective, building networked applications bears many similarities to traditional
|
||
single-host concurrent software. The key differences arise at the design stage.</p>
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||
<p>Networked applications can face a dilemma that other forms of concurrent software do not. For
|
||
example, assume that a process correctly formats a message and sends it into the socket. At the
|
||
other end, the receiver has correctly prepared to receive the message, but the message never
|
||
arrives. In other forms of IPC, the processes could check error codes provided by the OS to
|
||
determine what went wrong. In the network, however, there is no OS. The sender believes it was
|
||
successful at its end and hopes for the best for the message delivery. The receiver only knows the
|
||
data did not arrive; it cannot tell if the data was lost in transit or if the sender itself failed.</p>
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||
<p>Architects of networked applications must consider how to handle this scenario. Some socket
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||
configurations request the lower layers of the protocol stack fix the problem; the lower layers may
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||
still fail, but they will at least try. In other configurations, the application itself can accept
|
||
responsibility for handling the fault, either by re-sending the request, displaying an error
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||
message, or downgrading the quality of the application service (such as showing a pixelated version
|
||
of the image or pausing a video playback while more data is being buffered). This design choice
|
||
entails selecting an appropriate transport-layer protocol. While it may seem that reliability is
|
||
always required, that is not necessarily so. To properly design networked applications, it is
|
||
important to understand how the layers of the network fit together.</p>
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<p>In this chapter, we will explore the full protocol stack of the <a class="reference internal" href="Glossary.html#term-internet-model"><span class="xref std std-term">Internet model</span></a>. Starting at
|
||
the top, we will start with the overall system architecture of the application, along with how the
|
||
transport layer protocols influence the design. In addition, we will explore the capabilities and
|
||
functioning of the lower protocol layers, which can influence application design choices. This
|
||
overview includes an introduction to available security services, how hosts are located, and how
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data is actually transmitted. This chapter necessarily omits some details to create a foundational
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understanding of the key concepts of these layers. Interested readers should explore the details in
|
||
the recommended resources.</p>
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</div>
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