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The window scale option is used only during the TCP 3-way handshake. The window scale value represents the number of bits to left-shift the 16-bit window size field when interpreting it. The window scale value can be set from 0 (no shift) to 14 for each direction independently.
Handshaking is a technique of communication between two entities. However, within TCP/IP RFCs, the term "handshake" is most commonly used to reference the TCP three-way handshake. For example, the term "handshake" is not present in RFCs covering FTP or SMTP. One exception is Transport Layer Security, TLS, setup, FTP RFC 4217.
TCP is a connection-oriented protocol which adds complexity and processing overhead. These aspects include: Connection establishment using the "3-way handshake" (SYNchronize; SYNchronize-ACKnowledge; ACKnowledge). Acknowledgment of packets as they are received by the far end, adding to the message flow between the endpoints and thus the ...
Although encryption was not part of the original SCTP design, SCTP was designed with features for improved security, such as 4-way handshake (compared to TCP 3-way handshake) to protect against SYN flooding attacks, and large "cookies" for association verification and authenticity. Reliability was also a key part of the security design of SCTP.
Multipath TCP adds new mechanisms to TCP transmissions: The subflow system, used to gather multiple standard TCP connections (the paths from one host to another). Subflows are identified during the TCP three-way handshake. After the handshake, an application can add or remove some subflows (subtypes 0x3 and 0x4).
However, in order for transport layer protocols to operate most efficiently, ICMP Unreachable messages (type 3) should still be permitted. Some routers, including the Linux kernel [ 9 ] and Cisco, [ 10 ] provide an option to reduce the maximum segment size (MSS) advertised in the TCP handshake as a workaround.
In any case, I don't believe anyone ever refers to the connection termination as a handshake and pretty sure never a 3-way or 2-way handshake, but I'm prepared to be proven wrong. ...and we refer IP datagrams, UDP messages and TCP segments, but most people tend to say "packets" and that is generally fine unless one is being particularly pedantic.
The three-way handshake is correctly performed. SYN Flood. The attacker (Mallory, green) sends several packets but does not send the "ACK" back to the server. The connections are hence half-opened and consuming server resources. Legitimate user Alice (purple) tries to connect, but the server refuses to open a connection, a denial of service.