| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
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| 16-bit source port number |
16-bit destination port number |
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| 16-bit UDP length |
16-bit UDP checksum |
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UDP Header Information
| Common UDP Well-Known Sever Ports | |
| 7 echo | 138 netbios-dgm |
| 19 chargen | 161 snmp |
| 37 time | 162 snmp-trap |
| 53 domain | 500 isakmp |
| 67 bootps (DHCP) | 514 syslog |
| 68 bootpc (DHCP) | 520 rip |
| 69 tftp | 33434 traceroute |
| 137 netbios-ns | |
| Length (Number of bytes in entire datagram including header; minimum value = 8) |
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| Checksum (calculated by pre-pending 12-byte pseudo-IP header and entire UDP datagram. Pseudo IP header consists of SRCIP (4), DSTIP (4) ,padding (1 byte zeros), IP Protocol (1), UDP Length (2) = 12 bytes |
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