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The TCP/IP Guide  9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)       9  TCP/IP Internet Layer (OSI Network Layer) Protocols            9  Internet Protocol (IP/IPv4, IPng/IPv6) and IP-Related Protocols (IP NAT, IPSec, Mobile IP)                 9  Internet Protocol Version 4 (IP, IPv4)

IP CIDR Addressing Example 1 IP Datagram Encapsulation

The primary job of the Internet Protocol is the delivery of data between devices over an internetwork. On its journey between two hosts in an internet, this data may travel across many physical networks. To help ensure that the data is sent and received properly, it is encapsulated within a message called an IP datagram. This datagram includes several fields that help manage the operation of IP and ensure that data gets where it needs to go.

In this section I take a look at how the Internet Protocol takes data passed to it from higher layers and packages it for transmission. I begin with a general discussion of IP datagrams and encapsulation. I then describe the general format of IP datagrams, including the fields used in the IP header and how they are interpreted. I also include a brief discussion of IP datagram options and their use.

IP CIDR Addressing Example 1 IP Datagram Encapsulation