During our attempt to create an STCP packet, we encountered this problem: RFC 793 states that DATA OFFSET field must be 4 bits long. After it, comes the RESERVED field which is 6 bits long.
Wireshark analysis of regular TCP packets from UMLs reveals that the HEADER LENGTH field, which we assume to be the equivalent of the DATA OFFSET field, has a field-length of 2 hex digits = 2x4bits = 8bits. If the RFC states DATA OFFSET must be 4 bits, how come wireshark is expecting this field to have 8 bits in it? How can a TCP header length of 20 = value of "50" in wireshark be achieved if our DATA OFFSET field is limited to 4 bits. With 4 bits you can only go up to 15. Thanks, -- Imad
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