The ABCs of TCP/IP

  • Sample Chapter is provided courtesy of Cisco Press.
  • Date: Mar 25, 2005.

Contents

  1. What Is TCP/IP?
  2. The Abilities and Limitations of TCP/IP
  3. Chapter Summary
  4. Chapter Review Questions

Chapter Description

Learn the very basics of TCP/IP in this sample chapter by Mark Sportack. Find out how TCP/IP interacts with the internet, as well as with other communication protocols.

From the Book

TCP/IP First-Step

TCP/IP First-Step

$49.99

The Abilities and Limitations of TCP/IP

TCP/IP is a communications protocol that fits in the middle of a larger set of mechanisms. TCP/IP provides the linkage between communicating software applications and a physical network that carries messages sent by computers to other computers or devices. In this regard, TCP/IP complements and extends the capability of a physical network, but can't work without that network. Although TCP/IP does blur across some boundaries, it actually fits between the application software, operating system, and network or communications device such as a cable modem or local-area network (LAN). To visualize this, see Figure 1-1.

Figure 1Figure 1-1 TCP/IP Fits Between the Network and Your Software

Figure 1-1 shows a logical model. Logical models can be confusing due to their nature, but the best way to understand is to think of them as a necessary sequence of events. In this particular model, if you want to communicate across the Internet, you start with your application. Say you are sending a file directly to a friend across the Internet. The first thing you do is pick an application that lets you do that.

Fortunately, TCP/IP contains just such an application: It's called the File Transfer Protocol (FTP). You supply FTP with the necessary information, which is basically your friend's computer address and the file you want to send. FTP needs to engage the operating system to access your computer's physical resources including memory, CPU, and the peripheral device that connects your computer to the physical network.

The preceding example shows how TCP/IP can blur the traditional distinctions between types of software. Even though TCP/IP is just a communications protocol, it also contains numerous utilities or applications, such as FTP. It's part communications protocol and part application software.

On the receiving end, your friend's computer performs the same process, only in reverse. The file comes through the network, where your operating system uses whatever physical resources it must and ensures that TCP/IP gets the file via its own copy of FTP. Figure 1-2 illustrates this process.

Figure 2Figure 1-2 A Logical Perspective of Using TCP/IP to Transfer a File to a Friend

In its role as intermediary between software and the physical network, TCP/IP provides the rules and mechanisms that enable two or more different machines—even if they are very different machines—to communicate and share information with each other.

TCP/IP's mechanisms are designed to enable communications between any two or more machines connected to a network regardless of the device type, who made them, or their physical proximity to each other. Bridging the gap between dissimilar devices is a phenomenally powerful concept: You have created a mechanism that brings everybody together regardless of where they are or what technologies they use.

As shown in the preceding FTP example, the boundaries between operating system, application software, and communications protocols are blurred quite a bit by TCP/IP. When installed, TCP/IP functions as an extension of the operating system. So seamless is this integration that many people aren't even aware that they are using TCP/IP to communicate!

Even more confusion is added when you remember that TCP/IP contains quite a few simple applications that enable a user to directly do simple tasks like push files through a network or log on to remote computers. Part IV, "User Services—Making the Most Use of Your Network," looks more closely at those utilities. Users who are familiar with such utilities might think of TCP/IP as an application. They'd have justification for thinking that way! However, these utilities are just one small piece of the comprehensive set of protocols that you know and love and call TCP/IP.

Economically, too, TCP/IP has been a boon. The concept of an open mechanism that is not owned or controlled by any one commercial organization has opened doors few people could have imagined possible. For example, TCP/IP has become widely accepted around the world simply because it becomes the means by which different manufacturers' products can interoperate with each other. More importantly, TCP/IP broke new ground by pioneering a new method for developing new technologies that anyone could manufacture. Now, entities trying to develop a new communications-based product or technology can simply start with TCP/IP's openly published specifications and focus on adding value based on that preexisting set of capabilities. More importantly, developing products around TCP/IP brings a tremendous base of users who could easily integrate any new products based on that protocol suite.

TCP/IP's Top Five Critical Functions

By now you're probably anxious to get into what TCP/IP can do for you. Some of the applications that rely on TCP/IP (such as web surfing and e-mail) have been discussed, but you have seen how one set of mechanisms can so successfully support a rich and diverse array of applications.

The answer lies in determining the basic underlying capabilities any application requires to communicate. At the risk of sounding like a late-night talk show host, TCP/IP's top five critical functions follow:

  1. Globally Unique Addresses—An addressing system that permits you to uniquely identify any given machine connected to the Internet. This system affords the ability to create literally billions of unique addresses.

  2. Packet—Merely having an address for a networked machine isn't enough to permit communication. You also need a mechanism that allows you to send data to, and receive data from, the machine with that address. That mechanism is called a packet. Packets contain all the address information that a TCP/IP network needs to enable two or more devices to talk across a network.

  3. Segmentation and Reassembly—The ability to chop up application data into manageable pieces called segments is crucial to communicating across a network. These segments are then placed inside a packet for transmission across a network. The machine receiving this stream of packets can extract the segments of data and restore the data to its original form.

  4. Resequencing—TCP/IP also enables computers that receive a series of related packets to put them back into the correct order. This ability is important because you can't guarantee that packets will be received in the order they were sent. Networks are made of intelligent and autonomous devices known as routers, which decide where to send each packet. Their decisions can vary based on congestion and failures discovered within the network. The result is that packets are commonly received out of sequence!

  5. Data Integrity—Lastly, you can't always assume that what you put on a network will get to its destination intact. For that matter, you can't assume that it will get there at all! Lots of things can go wrong when data is traveling through a network. The result can be garbled data or even packets that get lost or dropped. TCP/IP is smart enough to detect data that was damaged or lost as it traveled through the network. Data that was damaged is discarded and TCP/IP's mechanisms ensure that—when appropriate—the damaged or lost block is retransmitted until it is successfully received.

TCP/IP can, of course, do many other things. Thus, this list is not comprehensive. Instead, these five things form the basis for communicating. Other features, including those that are part of TCP/IP and those commercially developed around TCP/IP, build upon this foundation.

What It Can't Do

TCP/IP is not a proverbial silver bullet. It offers tremendous capabilities, but it does have its limitations. Those limitations have more to do with the intended scope of the protocol suite than weaknesses. Please consider all the "can't dos" in this section as being by design rather than indicative of a flawed implementation.

First of all, TCP/IP is not an operating system (OS). An OS is the software that runs on a computer and creates the environment in which other applications can run. The various Windows platforms are examples of operating systems. When installed, TCP/IP becomes an important extension of your computer's operating system, but it does not replace it.

There was a time when some software vendors billed their operating system software as a Network Operating System (NOS), but that term is misleading. It indicates a computer OS that supports a robust ability to communicate. One critical component of that ability was the inclusion of communications protocols, such as TCP/IP. However, bundling a set of communications protocols with an operating system doesn't make those protocols the operating system! As networking ability has become a more integral part of both operating systems and application software, this distinction has fallen by the wayside; consumers began expecting their operating systems to offer a rich networking capability.

TCP/IP also isn't a network! Installing and configuring TCP/IP on your workstation or home computer does not, in and of itself, mean you can use that computer to communicate with other computers or devices. TCP/IP, by itself, is incapable of transmitting or carrying data. Those functions remain in the purview of a physical network such as an Ethernet or a wide-area network (WAN). TCP/IP prepares data received from applications for transmission and provides all the logical mechanisms needed to send and receive data between two devices connected via a physical network.

3. Chapter Summary | Next Section Previous Section

Cisco Press Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from Cisco Press and its family of brands. I can unsubscribe at any time.

Overview

Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about Cisco Press products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites; develop new products and services; conduct educational research; and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@ciscopress.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security

Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children

This site is not directed to children under the age of 13.

Marketing

Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out

Users can always make an informed choice as to whether they should proceed with certain services offered by Cisco Press. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.ciscopress.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links

This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020