Internet Packet: Definition & Explanation

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 and how you can test for and correct packet loss problems, such as signal loss.

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 (USPS) has employed transport agents, including steamboats, trains, horses (Pony Express), stagecoaches, and planes (airmail). Things have radically changed since then.

Packet delivery via Pony Express
Pony Express

Today, individuals and business people transmit billions of messages electronically everyday, 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:

  • Network address - Unique identifier applicable to specific network computer. The network address identifies the data packet's intended recipient.
  • Network protocol - Establishes the guidelines and conventions to send and receive messages formatted as data packets.
  • Data packet - 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 (payload), which in turn is followed by the packet footer (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 Table 1. Note: Bit distribution among fields may vary but will equal a total packet length of 32 bits.

Table 1. Fields comprising an IPv4 packet
IPv4 14 Packet Fields

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

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