When things go wrong, there must be demons, and when evil arrives, there must be ghosts.
In the entire TCP/IP protocol, the IP protocol is the core protocol.
The IP protocol is an unreliable, connectionless service.
Why is it unreliable?
There is no guarantee that the IP datagram can successfully reach the destination, and the reliable transmission is provided to the transport layer or the application layer to achieve.
Why no connection?
IP does not maintain any state information about subsequent datagrams.
Into the title:
The normal IP header length is 20 bytes, and the maximum length of the IP header is 60 bytes.
How does 20 bytes come:
because:
4bit + 4bit + 8bit + 16bit + 16bit + 3bit + 13bit + 8bit + 8bit + 16bit + 32bit + 32bit + 0bit = 160bit
8bit = 1Byte
Byte = Byte
So:
160bit = 20Byte = 20 words FestivalHow does 60 bytes come from:
4-bit header length means: The header length is the number of 32-bit words in the header.
The translated meaning is: the number of 32bit fields in the IP header, 4bit converted to decimal is 1+2+4+8=15. That is, the maximum number of 32-bit fields in the IP header is 15, which is generally understood as:
There are a total of 15 lines, one line of 32bit, that adds up to: 15 x 32bit = 15 x (32/8 Byte) = 60 Byte = 60 bytes