TCP Example

TCP SYN

Analyze a TCP SYN packet used in connection establishment. Understand the SYN flag, sequence numbers, window size, and TCP header fields step by step.

Hex Data

00 14 01 BB 00 00 00 01 00 00 00 00 60 02 04 00 00 00 00 00 00 00 00 00
Note: SYN flag set to 1, sequence number randomly generated, window size 1024
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handshakesyn

Field Breakdown

Source Port
Source port number
20
FTP Data
Destination Port
Destination port number
443
HTTPS
Sequence Number
Sequence number of the first data byte in this segment
1
Acknowledgment Number
Next sequence number the sender expects to receive
0
Data Offset
Size of TCP header in 32-bit words (minimum 5, maximum 15)
96
Reserved
Reserved for future use (must be zero)
0b1100000
Flags
Control flags (NS, CWR, ECE, URG, ACK, PSH, RST, SYN, FIN)
0b110000000000010
Window Size
Size of the receive window (flow control)
1024
Checksum
Checksum for error detection
0x0000
Urgent Pointer
Offset from sequence number indicating last urgent data byte
0

Related Resources

TCP Protocol Visualizer - Parse & Analyze TCP PacketsTCP Header Format and Fields Explained - ByteLensTCP Three-Way Handshake Packet Breakdown | ByteLensTCP Flags Explained - SYN, ACK, FIN, RST, PSH, URG

About TCP

Transmission Control Protocol (RFC 793)

Fields: 10
Endianness: big
Specification: RFC 793