Why use UDP instead of TCP?

UDP has lower overhead (8-byte header vs 20+ for TCP) and no connection setup delay. It is ideal for: real-time data (video, voice) where retransmission is worse than loss, simple query-response (DNS), broadcast/multicast, and when the application handles reliability itself (QUIC).

Is the UDP checksum optional?

In IPv4, yes — a checksum of 0 means "not computed". In IPv6, the checksum is mandatory. Always compute the checksum for reliability — a missing checksum means corrupted data will be delivered undetected.

TASK

Parse UDP datagram headers

UDP headers are 8 bytes: source port, destination port, length, and checksum. Learn to decode UDP for protocol analysis.

1

A UDP header is exactly 8 bytes: source port (2 bytes), destination port (2 bytes), length (2 bytes, includes header + data), checksum (2 bytes, optional in IPv4). UDP is connectionless — no handshake, no flow control, no retransmission. It is used for DNS, DHCP, SNMP, and real-time protocols (RTP, QUIC).
2

Hex Decoder →
Decode the hex representation of a UDP header. Bytes 0-1: source port, 2-3: destination port, 4-5: length (header + payload), 6-7: checksum. For example, 0035 0044 0010 0000 is source port 53 (DNS), dest port 68, length 16, no checksum.
3

Binary Decoder →
Decode the length and checksum fields. The length includes the 8-byte header plus payload. The checksum covers the pseudo-header (source/dest IP, protocol, length) + UDP header + data. In IPv4, checksum 0 means no checksum was computed.

Frequently asked questions

Why use UDP instead of TCP?: UDP has lower overhead (8-byte header vs 20+ for TCP) and no connection setup delay. It is ideal for: real-time data (video, voice) where retransmission is worse than loss, simple query-response (DNS), broadcast/multicast, and when the application handles reliability itself (QUIC).
Is the UDP checksum optional?: In IPv4, yes — a checksum of 0 means "not computed". In IPv6, the checksum is mandatory. Always compute the checksum for reliability — a missing checksum means corrupted data will be delivered undetected.