Home > Articles

This chapter is from the book

Internet Protocol

Internet Protocol (IP) is a protocol that operates from the Internet layer of the TCP/IP reference model. The specifications of IP are provided in RFC 791. IP is responsible for transmitting data to the correct destination. It also takes care of routing. Irrespective of the protocol used in the Transport layer, all the protocols rely on IP for sending and receiving data. The following are some of the characteristics of IP:

  • IP provides a connectionless delivery system. This means that every data packet that is sent across the network is treated as an independent unit. IP does not maintain the details of the connection between the server and the client.

  • IP does not guarantee a reliable data transfer. However, this does not mean that packets are ignored without a proper rule. Data loss occurs only when there are problems on the network.

  • IP provides a best-effort delivery system, which means that IP tries to avert data loss as much as possible. Data loss occurs only in exceptional situations, such as problems in the network due to a hardware failure.


The process of delivering data from one computer to another is called routing.

To learn more about routing, see "IP Routing," p. 259

Data Transmission Using IP

IP takes care of delivering a data packet irrespective of the location of the destination. Location in this context refers to the network on which the computer is located. The sender and the receiver can belong to the same network or might be on different networks. If the receiver is on the same network, the sender transmits the data directly to the destination. This is also called local delivery of packets. However, if the destination computer is on a different network, an intermediate device is required. The process of routing a data packet to a computer on a remote network is also called remote delivery of packets.

For more information on intermediate devices, see "Intermediate Devices," p. 13

To know more about how a computer checks whether the destination computer is on the same network, see "Routing Concepts," p. 260

The sender is ignorant of how the data packets reach the destination. The sender need not be aware of the path taken by the data to reach the destination. This concept is not new to you. For example, in the postal service, if you post a letter, all that you need to do is provide the correct address. You, as a sender, need not be aware of the how the letter is being sent to the destination. Similarly, during the transmission of data, it might pass through a number of intermediate devices before it reaches the final destination without the sender being aware of it. Each intermediate device can decide the best route or path that can be taken by the data.


The data that is sent by the application could be a text file, bitmap file, or an audio file.

Functions of IP

IP defines a set of standards for data transmission. The standards that are defined by IP are as follows:

  • IP defines the format of the basic unit of data transmission that can be sent to the Network Interface layer. This basic unit of data transmission is called a datagram or an IP datagram. The format of a datagram is discussed later in this chapter. A datagram is sent to the Network Interface layer in which it is encapsulated in a frame and transmitted over the physical medium. A frame is the basic unit of data transfer defined by the Network Interface layer. A datagram is converted to a frame because the Network Interface layer can transmit data only in the form of frames.

  • IP also performs routing. If there are more routes to the same destination, IP determines the best route that a data packet can take to reach the destination and also sends the data packet through the same path.

  • IP also defines a set of rules that define the conditions in which a datagram can be discarded. IP works with ICMP, which is responsible for generating error messages when an error occurs during data transmission. The Transport layer protocols, namely TCP and UDP, decide to retransmit data based on the error message that is received.

To know more about how error messages are generated by ICMP, see "Internet Control Message Protocol," p. 61

IP Hourglass Model

The data that is created by an application needs to pass through all the layers of the TCP/IP reference model to reach the destination. For example, the Application layer protocol used might be HTTP, FTP, or TFTP. Every application layer protocol is associated with a Transport layer protocol depending on whether it is connection-oriented or connectionless. The Transport layer protocol, in turn, interacts with IP for routing the data packets. It is very important to understand that irrespective of the Application layer protocols and the Transport layer protocols, the only protocol that is used for routing the data packets is IP. When the data transmission through the four layers is visualized, it takes the shape of an hourglass (see Figure 3.2) and thus the model is called the IP hourglass model.

Figure 3.2 The IP hourglass model depicts that whatever the path is taken by data, it has to pass through IP.

In Figure 3.2, notice that Source A and Source B interact with the HTTP, whereas Source C interacts with TFTP. HTTP interacts with TCP and TFTP interacts with UDP, which are in the Transport layer. TCP and UDP send the data to IP in the Internet layer. IP datagrams are forwarded to the Network Interface layer, which creates the frames based on the network technology used.

For information on RFCs, see "RFCs," p. 425

InformIT Promotional Mailings & Special Offers

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


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about 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.


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.


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


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


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


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.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. 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.informit.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.


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