What is the maximum length of an IPv4 datagram?65,535 bytes32 bits20 bytes16 bits

Step 1: Break Down the Problem

To determine the maximum length of an IPv4 datagram, we need to understand how the maximum size is defined within the context of the IPv4 protocol.

Step 2: Relevant Concepts

The maximum length of an IPv4 datagram is indicated in the header of the packet:

1. The total length field in the IPv4 header is 16 bits.
2. This means it can represent values from $0$ to $2^{16} - 1$.
3. Thus, the maximum value represented is $65,535$ bytes.

Step 3: Analysis and Detail

• The total length field specifies the length of the entire IPv4 datagram, including both the header and the data.
• Since the total length is 65,535 bytes, it encompasses the header which typically has a minimum size of 20 bytes. Therefore, the maximum payload size (data) is $65,535 - 20 = 65,515$ bytes.
• However, the question asks only for the maximum length of the datagram itself, not the payload.

Step 4: Verify and Summarize

Thus, the calculations confirm that the maximum length of an IPv4 datagram is indeed $65,535$ bytes, which is the direct result of the 16-bit length field in the IPv4 header.

Final Answer

The maximum length of an IPv4 datagram is 65,535 bytes.