The following are diagrams of the TCP and IP header structure. UDP is quite simple—only source and destination port numbers, length, and checksum:
Some important things in the IP packet:
- Ver: Version 4 or 6.
- Header length: 20 to 24 bytes with options.
- Type of Service (ToS): Usually implemented with Differentiated Services (DiffServ), and provide priority to preferred services.
TCP standard (RFC 793 from October 1981) has named this field ToS, and defined its structure. Differentiated Services standards that were published later (RFCs 2474, 2475 from December 1998 and others) are used for the implementation of the ToS byte ...