Analyser UDP datagram headers
UDP headers sont 8 octets: source port, destination port, longueur, et checksum. Apprendre en décoder UDP pour protocol analyse.
- 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 Décodeur hexadécimal →
Décoder 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 Décodeur binaire →
Décoder 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.
Questions fréquentes
- 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.