RDTSC Network Timing & Jitter Analysis in x64 Assembly: Nanosecond Packet Measurement & SOC Detection Evasion
OS-level clocks (gettimeofday, clock_gettime) introduce their own scheduling jitter — unusable for nanosecond-scale network measurement. RDTSC reads the CPU’s Time Stamp Counter directly: rdtsc + shl rdx,32 + or rax,rdx yields a 64-bit cycle count. Delta between two RDTSC reads gives precise inter-packet timing. Jitter = |D_i - D_{i-1}| across packet sequence. Gaussian distribution = stable network. High variance = bufferbloat, middlebox processing, or behavioral detection baseline deviation. CPUID/RDTSCP prevent out-of-order execution from skewing measurements.
