Hello, everyone.

There is a beautiful diagram here: TCP/IP Reference.

It also explains:

• RFC 791 - INTERNET PROTOCOL. APPENDIX B: Data Transmission Order
• RFC 1700 - Assigned Numbers. Introduction

The order of transmission of the header (from left to right)

 0                    1                   2                   3      - the tens
[0] 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1    - the ones

where:

[0] is the most significant bit (MSB). That is, the bit labeled 0 is the most significant bit.

 0
[0]          - 0th (00), total 1

 0
 _ 1         - 1st (01), total 2

 0
 _ _ 2       - 2nd (02), total 3

 0
 _ _ _ ... 9 - 9th (09), total 10

    1
... 0        - 10th (10), total 11

    2
... _ 1      - 21st (21), total 22

and so on