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Mscgen (short for MSC generator) is a software tool for drawing message sequence charts [1] from a simple to manage text-based source file. Rendered charts can be output in PNG, SVG and PostScript, with hyperlink information in ismap format.
In a Sequence Diagram, a vertical line is usually an object. The object can be active (in its own thread of execution) or passive (in the execution context of an active object). Arrows; In an MSC an arrow is usually an asynchronous message sent from one entity to another one. Once the message is sent the sending entity resumes its execution.
A TCP sequence prediction attack is an attempt to predict the sequence number used to identify the packets in a TCP connection, which can be used to counterfeit packets. [1] The attacker hopes to correctly guess the sequence number to be used by the sending host. If they can do this, they will be able to send counterfeit packets to the ...
TCP sequence numbers and receive windows behave very much like a clock. The receive window shifts each time the receiver receives and acknowledges a new segment of data. Once it runs out of sequence numbers, the sequence number loops back to 0. When a receiver advertises a window size of 0, the sender stops sending data and starts its persist ...
Example of three way handshaking. Establishing a normal TCP connection requires three separate steps: . The first host (Alice) sends the second host (Bob) a "synchronize" (SYN) message with its own sequence number , which Bob receives.
For an in-order packet, this is effectively the last packet's sequence number plus the current packet's payload length. If the next packet in the sequence is lost but a third packet in the sequence is received, then the receiver can only acknowledge the last in-order byte of data, which is the same value as was acknowledged for the first packet.
Defeating port knocking protection requires large-scale brute force attacks in order to discover even simple sequences. An anonymous brute force attack against a three-knock TCP sequence (e.g. port 1000, 2000, 3000) would require an attacker to test every three port combination in the 1–65535 range and then scan each port between attacks to uncover any changes in port access on the target ...
When a client sends back a TCP ACK packet to the server in response to the server's SYN+ACK packet, the client must (according to the TCP spec) use n+1 in the packet's Acknowledgement number, where n is the initial sequence number sent by the server. The server then subtracts 1 from the acknowledgement number to reveal the SYN cookie sent to ...