The data payload of an IP datagram contains the segment or message from the next higher-layer protocol , most commonly a TCP segment (or UDP datagram, ICMP message, etc.).

Quick Scoop

In normal TCP/IP communication, the IP layer just wraps and forwards whatever data it receives from the transport or higher layer. That wrapped content becomes the payload.

What exactly is inside the IP data payload?

For a typical TCP/IP scenario, the IP payload will contain:

  • A TCP segment when using the TCP protocol
    • Source port and destination port
    • Sequence and acknowledgment numbers
    • Flags (SYN, ACK, FIN, etc.)
    • Window size, checksum, urgent pointer, options
    • The actual application data (e.g., part of an HTTP request, email, file chunk)
  • Or, depending on the Protocol field in the IP header, it could contain:
    • A UDP datagram (for DNS, streaming, simple request/response services)
    • An ICMP message (for ping, error messages)
    • Other higher-layer protocol data (e.g., OSPF, GRE)

In other words, the IP payload is “whatever the higher layer hands down” — IP doesn’t understand its internal structure, it just transports it.

What is not in the IP data payload?

Certain things you might see as answer options in quizzes are not inside the IP payload itself:

  • Not an ARP discovery request (ARP runs at the link layer and is carried in Ethernet frames, not inside IP datagrams).
  • Not an entire network address space (only individual source and destination IP addresses appear in the IP header, not in the payload).
  • Not an ARP table (that is local state in a host/router, not transmitted as payload).

So, if you see a multiple‑choice question like:

“What information is in the data payload for the IP datagram?
– ARP discovery request
– Network B address space
– ARP table
– TCP segment”

The correct answer is: TCP segment.

Mini recap (for exam memory)

  • Think of the IP header as: “where it’s going and control info.”
  • Think of the IP payload as: “the higher‑layer message (often a TCP segment) plus the user data.”

Information gathered from public forums or data available on the internet and portrayed here.