TCP Header

Source Port – sending port

Destination Port – Receiving port

Sequence Number – Initially random. Each new transmission adds the size of the data

Acknowledgment Number – The next byte expected to be received.

Data offset - Size of TCP header in 32bit words

Reserved – 0's

Flags – Bit mask of all TCP flags

Window size – Max number of bytes receiver can handle

Checksum – Checksum of header and data

Urgent Pointer – Only valid if URG flag set

Options – Allows for expanded uses