Internet Packet: Definition & Explanation

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  • 0:04 Basic Principles
  • 1:13 Key Terms
  • 1:50 Data Packet Description
  • 2:47 Data Packet Composition
  • 4:27 Packet Loss
  • 5:06 Lesson Summary
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Lesson Transcript
Instructor: Kent Beckert

Kent is an adjunct faculty member for the College of Business at Embry-Riddle Aeronautical University and has a Master's degree in Technical Management.

In this lesson, we'll define Internet packets and describe Internet packet construction. We'll also discuss the 14 fields comprising a typical data packet.

Basic Principles

It was 1775 when the Second Continental Congress called for a line of posts from Falmouth in New England to Savannah in Georgia, and since that time, the United States Postal Service (or USPS) has employed transport agents, including steamboats, trains, horses (known as the Pony Express), stagecoaches, and planes (known as airmail). Things have radically changed since then.

Today, individuals and business people transmit billions of messages electronically every day, having their messages sent and delivered in seconds. To accomplish this high speed delivery, message contents and communicative information are packaged into small groups called Internet packets. These Internet packets, hereon referred to as data packets, are formatted, addressed, and sent using common Internet communication protocols, such as the Transmission Control Protocol/Internet Protocol (TCP/IP). This is not much different from preparing a package for a friend or family member, providing the return (originator) and the recipient (destination) addresses then delivering the package to the post office for transmission (forwarding) via the USPS system.

Key Terms

Before we begin our data packet discussion, let's define three applicable terms:

  1. A network address, which are unique identifiers applicable to specific network computer; the network address identifies the data packet's intended recipient

  2. A network protocol, which establishes the guidelines and conventions to send and receive messages formatted as data packets; and

  3. A data packet, which is essentially a container used to convey data or information via TCP/IP or similar protocol; the data packet contains (among other information) the IP address of the intended recipient, source data, and network information.

Data Packet Description

In this context, a data packet is composed of binary data (ones and zeros) formatted to allow movement along a computer network. Transmitted data arrives as individual data packets; each packet contains several sections. There is a header section composed of packet origin and packet destination information. The header section is followed by the message body (or payload), which in turn is followed by the packet footer (or trailer). Typically the packet footer contains ending or termination instructions. This process of sending and receiving data packets is referred to as packet-switching.

Both the packet header section and the packet footer section contain an error-checking algorithm needed to ascertain reception accuracy. Upon receipt, the receiving device reassembles the individual packets returning the message to its original form. Part of the re-assembly process requires the removal of header and footer information and the concatenation of individual packets placing the packets in their proper order.

Data Packet Composition

Presently there are two IP format versions: IPv4 and IPv6, with IPv4 being the most widely accepted. For the purposes of this lesson, we will concentrate on IPv4 composition.

Typically, an IPv4 packet is composed of the 14 fields shown in the table appearing on your screen right now. It's important to note that bit distribution among fields may vary but will equal a total packet length of 32 bits.

Each of the 14 fields indicated by name in Table 1 are numbered and briefly described in the itemized list here:

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