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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 ...
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).
Create a connection to a listening socket and upon 3 way handshake (inside last ACK) send 0 window. syn -> (4k window) <- syn+ack (32k window) ack -> (0 window) Now the server will have to "probe" the client until the zero window opens up. This is the most simple of the attack types to understand.
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.
The TCP congestion-avoidance algorithm is the primary basis for congestion control in the Internet. [2] [3] [4] Per the end-to-end principle, congestion control is largely a function of internet hosts, not the network itself.
This scan type is also known as "half-open scanning", because it never actually opens a full TCP connection. The port scanner generates a SYN packet. If the target port is open, it will respond with a SYN-ACK packet. The scanner host responds with an RST packet, closing the connection before the handshake is completed. [3]