Ver |
IHL |
ToS |
Total Length |
Identification |
Flags |
Fragment Offset |
Time to Live |
Protocol |
Header Checksum |
Source Addess |
Destination Addess |
Options |
(padding) |
|
The fields are described below:
- Ver - Internet format type or version (4 bits). For example: 4=IPv4 and 6=IPv6.
- IHL - Internet Header Length (4 bits) in 32 bit words. The minimum size is 20 bytes or a value of 5 in this field.
- ToS - Type of Service (8 bits).
- Total Length - Length of packet (16 bits).
- Identification - The fragment identification for rebuilding a fragmented packet (16 bits).
- Flags - Fragmentation flags: allowing fragmentation and more/last fragment (3 bits).
- Fragment Offset - The offset where the fragment belongs. The number is in 8-byte increments (13 bits). In other words, an offset value of 50 is byte offset 50*8 or 400 bytes.
- Time to Live - The maximum number of router hops allows for this packet (8 bits).
- Protocol - The message type (TCP, UDP, etc.) (8 bits).
- Header Checksum - The checksum of the IP header (16 bits).
- Source - The originating host's IP address (32 bits).
- Destination - The destination host's IP address (32 bits).
- Options - A set of IP options padded to 32-bit boundary (0-44 bytes).