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TCP/IP stack fingerprinting is the remote detection of the characteristics of a TCP/IP stack implementation. The combination of parameters may then be used to infer the remote machine's operating system (aka, OS fingerprinting ), or incorporated into a device fingerprint .
The three privilege-level stack pairs (SS0:ESP0, SS1:ESP1, SS2:ESP2); Read during an inter-level CALL or INT to establish a new stack. The IO Port Bitmap pointer (IOPB) and the I/O Port Bitmap itself; Read during an IN, OUT, INS or OUTS instruction if CPL > IOPL to confirm the instruction is legal (see I/O port permissions below).
This type of stack is also known as an execution stack, program stack, control stack, run-time stack, or machine stack, and is often shortened to simply the "stack". Although maintenance of the call stack is important for the proper functioning of most software , the details are normally hidden and automatic in high-level programming languages .
sampling the entire call stack, not just the program counter or a limited number of levels. sampling only during during the interval of interest. taking only a moderate number of samples. 20 is enough. 100 is more than enough. computing for each address that appears on call stacks the percent of call stack samples it appears on.
Stack-based allocation can also cause minor performance problems: it leads to variable-size stack frames, so that both stack and frame pointers need to be managed (with fixed-size stack frames, the stack pointer is redundant due to multiplying the stack frame pointer by the size of each frame).
Newer processors contain a dedicated stack engine to optimize stack operations. Pentium M was the first x86 processor to introduce a stack engine. In its implementation, the stack pointer is split among two registers: ESP O , which is a 32-bit register, and ESP d , an 8-bit delta value that is updated directly by stack operations.
In a stack machine, the operands used in the instructions are always at a known offset (set in the stack pointer), from a fixed location (the bottom of the stack, which in a hardware design might always be at memory location zero), saving precious in-cache or in-CPU storage from being used to store quite so many memory addresses or index ...
sFlow, short for "sampled flow", is an industry standard for packet export at Layer 2 of the OSI model. sFlow was originally developed by InMon Corp. [1] It provides a means for exporting truncated packets, together with interface counters for the purpose of network monitoring.