UDP Header
Byte
Offset
0 1 2 3
0
Source Port Destination Port
8
Bytes
4
Length Checksum
1 2 3
Bit 0 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1
0 0 0
Nibble Byte Word
ICMP Header
Byte
Offset
0 1 2 3
0
Type Code Checksum
8
Bytes
4
Other message specific information...
1 2 3
Bit 0 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1
0 0 0
Nibble Byte Word
ICMP Message Types Checksum RFC 768 and 792
Type Code/Name Type Code/Name Type Code/Name
Checksum of entire Please refer to RFC
0 Echo Reply 4 Source Quench 13 Timestamp
3 Destination Unreachable 5 Redirect 14 Timestamp Reply
UDP segment and 768 for the complete
0 Net Unreachable 0 Redirect Datagram for the Network 15 Information Request
1 Host Unreachable 1 Redirect Datagram for the Host 16 Information Reply
pseudo header (parts User Datagram
2 Protocol Unreachable 2 Redirect Datagram for the TOS & Network 17 Address Mask Request
of IP header) (for UDP) Protocol (UDP)
3 Port Unreachable 3 Redirect Datagram for the TOS & Host 18 Address Mask Reply
4 Fragmentation required, and DF set 8 Echo 30 Traceroute
Specification, and to
5 Source Route Failed 9 Router Advertisement
6 Destination Network Unknown 10 Router Selection
Checksum of ICMP RFC 792 for the
7 Destination Host Unknown 11 Time Exceeded
8 Source Host Isolated 0 TTL Exceeded in Transit
header (for ICMP) Internet Control
9 Network Administratively Prohibited 1 Fragment Reassembly Time Exceeded
Message protocol
10 Host Administratively Prohibited 12 Parameter Problem
11 Network Unreachable for TOS 0 Pointer indicates the error
(ICMP) specification.
12 Host Unreachable for TOS 1 Missing a Required Option
13 Communication Administratively Prohibited 2 Bad Length
Copyright 2004 - Matt Baxter - [e-mail]