What does SYN Flooding attack mean?
The SYN Flooding attack is carried out against the three-way handshake of the TCP connection. The principle is to maintain too many half-open connections on the attacked host, exhausting all relevant resources, and causing normal user requests to fail to respond due to the lack of resources [ 1]. Generally, such attacks have the following characteristics:
1) During the attack, the frequency of TCP connection requests sent by the attacking host will greatly exceed L / T (L: the maximum number of half-open connections of the server, T: the timeout of half-open connections). That is, when an attack occurs, the link near the server must be flooded with high-strength TCP connection request packets;
2) The attacker's high-frequency transmission will last for a considerable period of time, and the longer the duration, the more serious the impact of the attack, but the greater the possibility of being tracked;
3) The attacker must forge the source address of the request message. These attack packets may continuously change the forged address, or may use the same forged address. However, these addresses must be invalid addresses that cannot be routed to the destination or inactive valid addresses, otherwise the forged host will send a RST message to release the half-open connection, causing the attack to fail. Feature 1 and feature 2 are necessary conditions for an attack to occur, feature 3 is a sufficient condition for an attack to occur, and satisfying three features at the same time is a sufficient and necessary condition for an attack to occur. Therefore, in the implementation of attack detection tools, it becomes a key indicator to determine whether an attack has occurred.
984 controllers are available in four generic hardware classes: Large, rugged, high-performance chassis mount controllers Rugged, midrange-performance slot mount controllers, which reside in a primary housing beside 800 Series I/O Modules Host-based controllers built on various industry-standard computer cards designed to reside in and execute control logic from a host computer Low-cost, easy-to-install compact controllers, for applications with less demanding environmental and performance requirements The family approach to 984 controller design allows you to make choices based on controller capacity (the number of discrete and analog/register points available for application programming, the number of I/O drops it supports), throughput (the rate at which it solves logic and updates I/O modules), and environmental hardness (the design standards its hardware implementation must meet).
A major advantage of the family approach to 984 controller design is product compatibility. Regardless of its computational capacity, performance characteristics, or hardware implementation, each 984 controller is architecturally consistent with other 984s. The 984 instruction set (the functional capabilities of the controller, part of the system firmware stored in executive PROM) comprises logic functions common to other 984s. This means that user logic created on a midrange or high-performance unit such as a 984-685 or a 984B can be relocated to a smaller controller such as a 984-145 (assuming sufficient memory in the smaller machine) and that logic created on a smaller controller is upwardly compatible to a larger unit. As your application requirements increase, it is relatively easy to upgrade your controller hardware without having to rewrite control logic. Also, training costs and learning curves can be reduced, since users familiar with one 984 model automatically have a strong understanding of others.
Modicon PC0984 Programmable Controller
Modicon PC 0984 Programmable Controller,Communication Processor,Processor Module,CPU Module
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