Urgent Mechanism
Difference between push and urgent flags in TCP
https://stackoverflow.com/questions/9153566/difference-between-push-and-urgent-flags-in-tcp
Attacks Involving Window Management
The window management procedures for TCP have been the subject of various attacks, primarily forms of resource exhaustion.
In essence, advertising a small window slows a TCP transfer, tying up(zhan yong) resources such as memory for a potentially long time.
This has been used as a form of attack on bad traffic (i.e., worms).
The LaBrea tarpit [L01], for example, arranges to complete the TCP three-way hand- shake and then either does nothing or produces minimal responses that simply cause the sending TCP to continually slow down.
This keeps the sending TCP busy and essentially slows down worm propagation. Tarpits are thus attacks on attacking traffic.
Summary